@misc{BendixTrachtePalaciosetal., author = {Bendix, J{\"o}rg and Trachte, Katja and Palacios, Enrique and Rollenbeck, R{\"u}tger and G{\"o}ttlicher, Dietrich and Nauss, Thomas and Bendix, Astrid}, title = {El Ni{\~n}o meets La Ni{\~n}a - anomalous rainfall patterns in the "traditional" El Ni{\~n}o region of Southern Ecuador}, series = {Erdkunde}, volume = {65}, journal = {Erdkunde}, number = {2}, doi = {10.3112/erdkunde.2011.02.04}, pages = {151 -- 167}, abstract = {In this paper, the central Pacific cold event of 2008 and its exceptionally warm conditions in the eastern tropical Pacific are analyzed by using rainfall data of south Ecuadorian meteorological stations, sea surface temperatures in the El Ni{\~n}o3 and 1+2 regions, and simulations with the Weather Research and Forecasting (WRF) model. It can be shown that El Ni{\~n}o-like rainfall conditions with severe inundations occur particularly in the coastal plains of southern Ecuador while a central Pacific cold event prevails. In contrary to previous situations, positive rainfall anomalies as a result of El Ni{\~n}o-like conditions in the El Ni{\~n}o1+2 region during the 2008 La Ni{\~n}a event occurred in both regions, the coastal plains and the highlands, for the first time. A detailed analysis of the ocean-atmosphere system during episodes of heavy rainfall reveals typical El Ni{\~n}o circulation and rainfall patterns as observed during previous El Ni{\~n}o events for the coastal area and La Ni{\~n}a-like conditions for the highlands. The spreading of Pacific instability in the Ni{\~n}o1+2 region to the eastern escarpment of the Andes could be the result of a temporary eastward shift of the Walker circulation. The unusual combination of El Ni{\~n}o-like conditions in the eastern tropical Pacific during a La Ni{\~n}a state in the central Pacific is the newest indicator for an impact mode shift regarding severe rainfall anomalies during El Ni{\~n}o/La Ni{\~n}a events in the traditional El Ni{\~n}o area of southern Ecuador since the end of the last century. Since 2000, El Ni{\~n}o events unexpectedly provide below average rainfall while central Pacific La Ni{\~n}a conditions generate exceptional severe flooding in the normally drier coastal plains. The novel sea surface temperature (SST) anomaly dipole structure between the eastern and central/western tropical Pacific and the weakening of El Ni{\~n}o events since 2000 could be due to natural decadal oscillations in the El Ni{\~n}o background state, the Pacific Decadal Oscillation (PDO). However, the observed atmospheric patterns and the recent increase of the SST anomaly difference between the central and the eastern tropical Pacific resemble structures that also result from climate change simulations.}, language = {en} } @misc{KnerrTrachteGareletal., author = {Knerr, Isabel and Trachte, Katja and Garel, Emilie and Huneau, Fr{\´e}d{\´e}ric and Santoni, S{\´e}bastien and Bendix, J{\"o}rg}, title = {Partitioning of Large-Scale and Local-Scale Precipitation Events by Means of Spatio-Temporal Precipitation Regimes on Corsica}, series = {Atmosphere}, volume = {11}, journal = {Atmosphere}, number = {4}, doi = {10.3390/atmos11040417}, pages = {19}, abstract = {The island of Corsica in the western Mediterranean is characterized by a pronounced topography in which local breeze systems develop in the diurnal cycle. In interaction with the large-scale synoptic situation, various precipitation events occur, which are classified in this study with regard to their duration and intensity. For this purpose, the island was grouped into five precipitation regimes using a cluster analysis, namely the western coastal area, the central mountainous region, the southern coastal area, the northeast coastal area, and the eastern coastal area. Based on principal component analysis using mean sea level pressure (mslp) obtained from ERA5 reanalysis (the fifth generation of the European Centre for Medium-Range Weather Forecasts, ECMWF), six spatial patterns were identified which explain 98\% of the large-scale synoptic situation, while the diurnal breeze systems within the regimes characterize local drivers. It is shown that on radiation days with weak large-scale pressure gradients, pronounced local circulations in mountainous regions are coupled with sea breezes, leading to a higher number of short and intense precipitation events. Meridional circulation patterns lead to more intensive precipitation events on the eastern part of the island (30\% intensive events with meridional patterns on the east side compared to 11\% on the west side). On the west side of Corsica, however, coastal precipitation events are seldom and less intense than further inland, which can be attributed to the influence of the topography in frontal passages.}, language = {en} } @misc{SeidelTrachteOrellanaAlvearetal., author = {Seidel, Jochen and Trachte, Katja and Orellana-Alvear, Johanna and Figueroa, Rafael and C{\´e}lleri, Rolando and Bendix, J{\"o}rg and Fernandez, Ciro and Huggel, Christian}, title = {Precipitation Characteristics at Two Locations in the Tropical Andes by Means of Vertically Pointing Micro-Rain Radar Observations}, series = {Remote Sensing}, volume = {11}, journal = {Remote Sensing}, number = {24}, doi = {10.3390/rs11242985}, pages = {18}, abstract = {In remote areas with steep topography, such as the Tropical Andes, reliable precipitation data with a high temporal resolution are scarce. Therefore, studies focusing on the diurnal properties of precipitation are hampered. In this paper, we investigated two years of data from Micro-Rain Radars (MRR) in Cuenca, Ecuador, and Huaraz, Peru, from February 2017 to January 2019. This data allowed for a detailed study on the temporal precipitation characteristics, such as event occurrences and durations at these two locations. Our results showed that the majority of precipitation events had durations of less than 3 h. In Huaraz, precipitation has a distinct annual and diurnal cycle where precipitation in the rainy season occurred predominantly in the afternoon. These annual and diurnal cycles were less pronounced at the site in Cuenca, especially due to increased nocturnal precipitation events compared to Huaraz. Furthermore, we used a fuzzy logic classification of fall velocities and rainfall intensities to distinguish different precipitation types. This classification showed that nightly precipitation at both locations was predominantly stratiform, whereas (thermally induced) convection occurred almost exclusively during the daytime hours.}, language = {en} } @misc{CarrilloRojasSchulzOrellanaAlvearetal., author = {Carrillo-Rojas, Galo and Schulz, Hans Martin and Orellana-Alvear, Johanna and Ochoa-S{\´a}nchez, Ana and Trachte, Katja and C{\´e}lleri, Rolando and Bendix, J{\"o}rg}, title = {Atmosphere-surface fluxes modeling for the high Andes: The case of p{\´a}ramo catchments of Ecuador}, series = {Science of the Total Environment}, journal = {Science of the Total Environment}, number = {704}, issn = {0048-9697}, doi = {10.1016/j.scitotenv.2019.135372}, abstract = {Interest in atmosphere-surface flux modeling over the mountainous regions of the globe has increased recently, with a major focus on the prediction of water, carbon and other functional indicators in natural and disturbed conditions. However, less research has been centered on exploring energy fluxes (net radiation; sensible, latent and soil heat) and actual evapotranspiration (ETa) over the Neotropical Andean biome of the p{\´a}ramo. The present study assesses the implementation and parameterization of a state-of-art Land-Surface Model (LSM) for simulation of these fluxes over two representative p{\´a}ramo catchments of southern Ecuador. We evaluated the outputs of the LSM Community Land Model (CLM ver. 4.0) with (i) ground-level flux observations from the first (and highest) Eddy Covariance (EC) tower of the Northern Andean p{\´a}ramos; (ii) spatial ETa estimates from the energy balance-based model METRIC (based on Landsat imagery); and (iii) derived ETa from the closure of the water balance (WB). CLM's energy predictions revealed a significant underestimation on net radiation, which impacts the sensible and soil heat fluxes (underestimation), and delivers a slight overestimation on latent heat flux. Modeled CLM ETa showed acceptable goodness-of-fit (Pearson R = 0.82) comparable to ETa from METRIC (R = 0.83). Contrarily, a poor performance of ETa WB was observed (R = 0.46). These findings provide solid evidence on the CLM's accuracy for the ETa modeling, and give insights in the selection of other ETa methods. The study contributes to a better understanding of ecosystem functioning in terms of water loss through evaporative processes, and might help in the development of future LSMs' implementations focused on climate / land use change scenarios for the p{\´a}ramo.}, language = {en} } @misc{CampozanoTrachteCellerietal., author = {Campozano, Lenin and Trachte, Katja and C{\´e}lleri, Rolando and Samaniego, Esteban and Bendix, J{\"o}rg and Albuja, Crist{\´o}bal and Mejia, John F.}, title = {Climatology and Teleconnections of Mesoscale Convective Systems in an Andean Basin in Southern Ecuador: The Case of the Paute Basin}, series = {Advances in Meteorology}, volume = {2018}, journal = {Advances in Meteorology}, number = {3}, doi = {10.1155/2018/4259191}, abstract = {Mesoscale convective systems (MCSs) climatology, the thermodynamic and dynamical variables, and teleconnections influencing MCSs development are assessed for the Paute basin (PB) in the Ecuadorian Andes from 2000 to 2009. *e seasonality of MCSs occurrence shows a bimodal pattern, with higher occurrence during March-April (MA) and October-November (ON), analogous to the regional rainfall seasonality. *e diurnal cycle of MCSs shows a clear nocturnal occurrence, especially during the MA and ON periods. Interestingly, despite the higher occurrence of MCSs during the rainy seasons, the monthly size relative frequency remains fairly constant throughout the year. On the east of the PB, the persistent high convective available potential and low convective inhibition values from midday to nighttime are likely related to the nocturnal development of the MCSs. A significant positive correlation between the MCSs occurrence to the west of the PB and the Trans-Ni{\~n}o index was found, suggesting that ENSO is an important source of interannual variability of MCSs frequency with increasing development of MCSs during warm ENSO phases. On the east of the PB, the variability of MCSs is positively correlated to the tropical Atlantic sea surface temperature anomalies south of the equator, due to the variability of the Atlantic subtropical anticyclone, showing main departures from this relation when anomalous conditions occur in the tropical Pacific due to ENSO.}, language = {en} } @misc{TrachteSeidelFigueroaetal., author = {Trachte, Katja and Seidel, Jochen and Figueroa, Rafael and Otto, Marco and Bendix, J{\"o}rg}, title = {Cross-Scale Precipitation Variability in a Semiarid Catchment Area on the Western Slopes of the Central Andes}, series = {Journal of Applied Meteorology and Climatology}, volume = {57}, journal = {Journal of Applied Meteorology and Climatology}, number = {3}, doi = {10.1175/JAMC-D-17-0207.1}, pages = {675 -- 694}, abstract = {Spatiotemporal precipitation patterns were investigated on the western slopes of the central AndesMountains by applying EOF and cluster analysis as well as the Weather Research and Forecasting (WRF)Model. In the semiarid catchment area in the highlands of Lima, Peru, the precipitation is assumed to be across-scale interplay of large-scale dynamics, varying sea surface temperatures (SSTs), and breeze-dominatedslope flows. The EOF analysis was used to encompass and elucidate the upper-level circulation patternsdominating the transport of moisture. To delineate local precipitation regimes, a partitioning cluster analysiswas carried out, which additionally should illustrate local effects such as the altitudinal gradient of the Andes. Theresults demonstrated that especially during the transition to the dry season, synoptic-scale circulation aloft controlsthe precipitation (correlation coefficients between 0.6 and 0.9), whereas in the remaining seasons the slope breezesdue to the altitudinal gradient mainly determine the precipitation behavior. Further analysis with regard to thespatiotemporal precipitation variability revealed an inversion of the precipitation distribution along the elevationalgradient within the study area, mainly during February (29\%) and March (35\%), that showed correlations withcoastal SST patterns ranging between 0.56 and 0.67. WRF simulations of the underlying mechanisms disclosed thatthe large-scale circulation influences the thermally induced upslope flows while the strength of southeastern low-level winds related to the coastal SSTs caused a blocking of easterlies in the middle troposphere through a reducedanticyclonic effect. This interplay enables the generation of precipitation in the usually drier environment at lower elevations, which leads to a decrease in rainfall with increasing elevation.}, language = {en} } @misc{LehnertThiesTrachteetal., author = {Lehnert, Lukas W. and Thies, Boris and Trachte, Katja and Achilles, Sebastian and Osses, Pablo and Baumann, Karen and Schmidt, Jakob and Samolov, Elena and Jung, Patrick and Leinweber, Peter and Karsten, Ulf and B{\"u}del, Burkhard and Bendix, J{\"o}rg}, title = {A Case Study on Fog/Low Stratus Occurrence at Las Lomitas, Atacama Desert (Chile) as a Water Source for Biological Soil Crusts}, series = {Aerosol and Air Quality Research}, volume = {18}, journal = {Aerosol and Air Quality Research}, number = {1}, issn = {1680-8584}, doi = {10.4209/aaqr.2017.01.0021}, pages = {254 -- 269}, abstract = {The Atacama Desert is well known for the high occurrence of large-scale fog (spatial extents: hundreds of kilometers) emerging as low stratus (LST) decks over the Pacific Ocean. By contrast, the small-scale and heterogeneous occurrence of small-scale fog (hundreds of meters) particularly during summers is widely unconsidered. However, these events are important for the local vegetation and particularly for the biological soil crusts (BSC) that are widely distributed in this extreme ecosystem. Consequently, a case study in a typical fog oasis in the Pan de Az{\´u}car National Park was conducted to test the feasibility combining field measurements, drone profiling, remote sensing and numerical modeling (i) to investigate fog-type specific differences regarding dynamics, physical properties and formation, (ii) to test the applicability of remote sensing technology for fog monitoring based on existing low-resolution and a proposed new high-resolution product and (iii) to estimate the related fog water input to BSCs. Two types of fog were observed. The well-known fog/LST deck emerging from the Pacific Ocean with high water path and large spatial extent was the first type. Fog of the second type was patchier, small-scale and not necessarily connected to the LST over the ocean. Instead, fog formation of the second type was related to thermal breeze systems, which produced shallow clouds containing less water than those of type 1. In general, such small-scale fog events were not captured well by existing remote sensing products but could be detected with the proposed new high-resolution product which provided promising results. Both fog types were important water resources for the BSCs, with approximately 8\% to 24\% of the fog water flux available to the BSCs at the surface. The results indicated the feasibility of the proposed methods' pool to estimate the water budget of BSCs with a high spatial resolution in the future.}, language = {en} } @misc{BendixFriesZarateetal., author = {Bendix, J{\"o}rg and Fries, Andreas and Z{\´a}rate, Jorge and Trachte, Katja and Rollenbeck, R{\"u}tger and Pucha-Cofrep, Franz and Paladines, Renzo and Palacios, Ivan and Orellana-Alvear, Johanna and O{\~n}ate-Valdivieso, Fernando and Naranjo, Carlos and Mendoza, Leonardo and Mejia, Diego and Guallpa, Mario and Gordillo, Francisco and Gonzalez-Jaramillo, Victor and Dobbermann, Maik and C{\´e}lleri, Rolando and Carrillo, Carlos and Araque, Augusto and Achilles, Sebastian}, title = {RadarNet-Sur First Weather Radar Network in Tropical High Mountains}, series = {Bulletin of the American Meteorological Society}, volume = {98}, journal = {Bulletin of the American Meteorological Society}, number = {6}, doi = {10.1175/BAMS-D-15-00178.1}, pages = {1235 -- 1254}, abstract = {Weather radar networks are indispensable tools for forecasting and disaster prevention in industrialized countries. However, they are far less common in the countries of South America, which frequently suffer from an underdeveloped network of meteorological stations. To address this problem in southern Ecuador, this article presents a novel radar network using cost-effective, single-polarization, X-band technology: the RadarNet-Sur. The RadarNet-Sur network is based on three scanning X-band weather radar units that cover approximately 87,000 km2 of southern Ecuador. Several instruments, including five optical disdrometers and two vertically aligned K-band Doppler radar profilers, are used to properly (inter) calibrate the radars. Radar signal processing is a major issue in the high mountains of Ecuador because cost-effective radar technologies typically lack Doppler capabilities. Thus, special procedures were developed for clutter detection and beam blockage correction by integrating ground-based and satelliteborne measurements. To demonstrate practical applications, a map of areas frequently affected by intense rainfall is presented, based on a time series of one radar that has been in operation since 2002. Such information is of vital importance to, for example, infrastructure management because rain-driven landslides are a major issue for road maintenance and safety throughout Ecuador. The presented case study of exceptionally strong rain events during the recent El Ni{\~n}o in March 2015 highlights the system's practicality in weather forecasting related to disaster management. For the first time, RadarNet-Sur warrants a spatial-explicit observation of El Ni{\~n}o-related heavy precipitation in a transect from the coast to the highlands in a spatial resolution of 500 m.}, language = {en} } @misc{MakowskiGiannoniTrachteRollenbecketal., author = {Makowski Giannoni, Sandro and Trachte, Katja and Rollenbeck, R{\"u}tger and Lehnert, Lukas W. and Fuchs, Julia and Bendix, J{\"o}rg}, title = {Atmospheric salt deposition in a tropical mountain rainforest at the eastern Andean slopes of south Ecuador - Pacific or Atlantic origin?}, series = {Atmospheric Chemistry and Physics}, volume = {16}, journal = {Atmospheric Chemistry and Physics}, number = {15}, doi = {10.5194/acp-16-10241-2016}, pages = {10241 -- 10261}, abstract = {Sea salt (NaCl) has recently been proven to be of the utmost importance for ecosystem functioning in Amazon lowland forests because of its impact on herbivory, litter decomposition and, thus, carbon cycling. Sea salt deposition should generally decline as distance from its marine source increases. For the Amazon, a negative east-west gradient of sea salt availability is assumed as a consequence of the barrier effect of the Andes Mountains for Pacific air masses. However, this generalized pattern may not hold for the tropical mountain rainforest in the Andes of southern Ecuador. To analyse sea salt availability, we investigated the deposition of sodium (Na+) and chloride (Cl-), which are good proxies of sea spray aerosol. Because of the complexity of the terrain and related cloud and rain formation processes, sea salt deposition was analysed from both, rain and occult precipitation (OP) along an altitudinal gradient over a period between 2004 and 2009. To assess the influence of easterly and westerly air masses on the deposition of sodium and chloride over southern Ecuador, sea salt aerosol concentration data from the Monitoring Atmospheric Composition and Climate (MACC) reanalysis data set and back-trajectory statistical methods were combined. Our results, based on deposition time series, show a clear difference in the temporal variation of sodium and chloride concentration and Na+ ∕ Cl- ratio in relation to height and exposure to winds. At higher elevations, sodium and chloride present a higher seasonality and the Na+ ∕ Cl- ratio is closer to that of sea salt. Medium- to long-range sea salt transport exhibited a similar seasonality, which shows the link between our measurements at high elevations and the sea salt synoptic transport. Although the influence of the easterlies was predominant regarding the atmospheric circulation, the statistical analysis of trajectories and hybrid receptor models revealed a stronger impact of the north equatorial Atlantic, Caribbean, and Pacific sea salt sources on the atmospheric sea salt concentration in southern Ecuador. The highest concentration in rain and cloud water was found between September and February when air masses originated from the north equatorial Atlantic, the Caribbean Sea and the equatorial Pacific. Together, these sources accounted for around 82.4 \% of the sea salt budget over southern Ecuador.}, language = {en} } @misc{LehnertWescheTrachteetal., author = {Lehnert, Lukas W. and Wesche, Karsten and Trachte, Katja and Reudenbach, Christoph and Bendix, J{\"o}rg}, title = {Climate variability rather than overstocking causes recent large scale cover changes of Tibetan pastures}, series = {Scientific Reports}, volume = {6}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/srep24367}, abstract = {The Tibetan Plateau (TP) is a globally important "water tower" that provides water for nearly 40\% of the world's population. This supply function is claimed to be threatened by pasture degradation on the TP and the associated loss of water regulation functions. However, neither potential large scale degradation changes nor their drivers are known. Here, we analyse trends in a high-resolution dataset of grassland cover to determine the interactions among vegetation dynamics, climate change and human impacts on the TP. The results reveal that vegetation changes have regionally different triggers: While the vegetation cover has increased since the year 2000 in the north-eastern part of the TP due to an increase in precipitation, it has declined in the central and western parts of the TP due to rising air temperature and declining precipitation. Increasing livestock numbers as a result of land use changes exacerbated the negative trends but were not their exclusive driver. Thus, we conclude that climate variability instead of overgrazing has been the primary cause for large scale vegetation cover changes on the TP since the new millennium. Since areas of positive and negative changes are almost equal in extent, pasture degradation is not generally proceeding.}, language = {en} } @misc{CampozanoCelleriTrachteetal., author = {Campozano, Lenin and C{\´e}lleri, Rolando and Trachte, Katja and Bendix, J{\"o}rg and Samaniego, Esteban}, title = {Rainfall and Cloud Dynamics in the Andes: A Southern Ecuador Case Study}, series = {Advances in Meteorology}, volume = {2016}, journal = {Advances in Meteorology}, doi = {10.1155/2016/3192765}, pages = {15}, abstract = {Mountain regions worldwide present a pronounced spatiotemporal precipitation variability, which added to scarce monitoring networks limits our understanding of the generation processes involved. To improve our understanding of clouds and precipitation dynamics and cross-scale generation processes in mountain regions, we analyzed spatiotemporal rainfall patterns using satellite cloud products (SCP) in the Paute basin (900-4200 m a.s.l. and 6481 km2) in the Andes of Ecuador. Precipitation models, using SCP and GIS data, reveal the spatial extension of three regimes: a three-modal (TM) regime present across the basin, a bimodal (BM) regime, along sheltered valleys, and a unimodal (UM) regime at windward slopes of the eastern cordillera. Subsequently, the spatiotemporal analysis using synoptic information shows that the dry season of the BM regime during boreal summer is caused by strong subsidence inhibiting convective clouds formation. Meanwhile, in UM regions, low advective shallow cap clouds mainly cause precipitation, influenced by water vapor from the Amazon and enhanced easterlies during boreal summer. TM regions are transition zones from UM to BM and zones on the windward slopes of the western cordillera. These results highlight the suitability of satellite and GIS data-driven statistical models to study spatiotemporal rainfall seasonality and generation processes in complex terrain, as the Andes.}, language = {en} } @misc{TrachteRollenbeckBendix, author = {Trachte, Katja and Rollenbeck, R{\"u}tger and Bendix, J{\"o}rg}, title = {Nocturnal convective cloud formation under clear-sky conditions at the eastern Andes of south Ecuador}, series = {Journal of Geophysical Research Atmospheres}, volume = {115}, journal = {Journal of Geophysical Research Atmospheres}, number = {D24}, doi = {10.1029/2010JD014146}, pages = {15}, abstract = {[1] The formation of nocturnal convective clouds at the eastern Andes of south Ecuador and the adjacent Peruvian Amazon basin was investigated in a numerical model study. Their formation is expected to be an interactive procedure of nocturnal downslope flows in the Andean terrain, which forms a concave drainage system in the target area. Satellite imagery were used for both the identification of a sample case with a nocturnal cold cloud appearance and for the verification of the simulated results. The cloud patterns were distinguished on the basis of IR temperatures. A comparison of the data demonstrated the occurrence of a cold cloud shield in the target area, although the modeled cluster is significantly smaller. Further analysis of the development of the convective cells confirmed the assumed underlying processes. A strong current in the lower atmosphere, presumably a drainage flow, was recognizable in association with strong moisture convergence using a cross section through the cluster. Their presence was confirmed on the basis of their characteristic features and the surface energy fluxes as the driving force for thermally induced downslope flows.}, language = {en} } @misc{TrachteNaussBendix, author = {Trachte, Katja and Nauss, Thomas and Bendix, J{\"o}rg}, title = {The Impact of Different Terrain Configurations on the Formation and Dynamics of Katabatic Flows: Idealised Case Studies}, series = {Boundary-Layer Meteorology}, volume = {134}, journal = {Boundary-Layer Meteorology}, number = {2}, doi = {10.1007/s10546-009-9445-8}, pages = {307 -- 325}, abstract = {Impacts of different terrain configurations on the general behaviour of idealised katabatic flows are investigated in a numerical model study. Various simplified terrain models are applied to unveil modifications of the dynamics of nocturnal cold drainage of air as a result of predefined topographical structures. The generated idealised terrain models encompass all major topographical elements of an area in the tropical eastern Andes of southern Ecuador and northern Peru, and the adjacent Amazon. The idealised simulations corroborate that (i) katabatic flows develop over topographical elements (slopes and valleys), that (ii) confluence of katabatic flows in a lowland basin with a concave terrainline occur, and (iii) a complex drainage flow system regime directed into such a basin can sustain the confluence despite varying slope angles and slope distances.}, language = {en} } @misc{BendixTrachteCermaketal., author = {Bendix, J{\"o}rg and Trachte, Katja and Cermak, Jan and Rollenbeck, R{\"u}tger and Nauß, Thomas}, title = {Formation of Convective Clouds at the Foothills of the Tropical Eastern Andes (South Ecuador)}, series = {Journal of Applied Meteorology and Climatology}, volume = {48}, journal = {Journal of Applied Meteorology and Climatology}, number = {8}, doi = {10.1175/2009JAMC2078.1}, pages = {1682 -- 1695}, abstract = {This study examines the seasonal and diurnal dynamics of convective cloud entities—small cells and a mesoscale convective complex-like pattern—in the foothills of the tropical eastern Andes. The investigation is based on Geostationary Operational Environmental Satellite-East (GOES-E) satellite imagery (2005-07), images of a scanning X-band rain radar, and data from regular meteorological stations. The work was conducted in the framework of a major ecological research program, the Research Unit 816, in which meteorological instruments are installed in the Rio San Francisco valley, breaching the eastern Andes of south Ecuador. GOES image segmentation to discriminate convective cells and other clouds is performed for a 600 × 600 km2 target area, using the concept of connected component labeling by applying the 8-connectivity scheme as well as thresholds for minimum blackbody temperature, spatial extent, and eccentricity of the extracted components. The results show that the formation of convective clouds in the lowland part of the target area mainly occurs in austral summer during late afternoon. Nocturnal enhancement of cell formation could be observed from October to April (particularly February-April) between 0100 and 0400 LST (LST = UTC - 5 h) in the Andean foothill region of the target area, which is the relatively dry season of the adjacent eastern Andean slopes. Nocturnal cell formation is especially marked southeast of the Rio San Francisco valley in the southeast Andes of Ecuador, where a confluence area of major katabatic outflow systems coincide with a quasi-concave shape of the Andean terrain line. The confluent cold-air drainage flow leads to low-level instability and cellular convection in the warm, moist Amazon air mass. The novel result of the current study is to provide statistical evidence that, under these special topographic situations, katabatic outflow is strong enough to generate mainly mesoscale convective complexes (MCCs) with a great spatial extent. The MCC-like systems often increase in expanse during their mature phase and propagate toward the Andes because of the prevailing upper-air easterlies, causing early morning peaks of rainfall in the valley of the Rio San Francisco. It is striking that MCC formation in the foothill area is clearly reduced during the main rainy season [June-August (JJA)] of the higher eastern Andean slopes. At a first glance, this contradiction can be explained by rainfall persistence in the Rio San Francisco valley, which is clearly lower during the time of convective activity (December-April) in comparison with JJA, during which low-intensity rainfall is released by predominantly advective clouds with greater temporal endurance.}, language = {en} } @misc{RollenbeckTrachteBendix, author = {Rollenbeck, R{\"u}tger and Trachte, Katja and Bendix, J{\"o}rg}, title = {A New Class of Quality Controls for Micrometeorological Data in Complex Tropical Environments}, series = {Journal of Atmospheric and Oceanic Technology}, volume = {33}, journal = {Journal of Atmospheric and Oceanic Technology}, number = {1}, doi = {10.1175/JTECH-D-15-0062.1}, pages = {169 -- 183}, abstract = {Quality control is a particularly demanding problem for micrometeorological studies in complex environments. With the transition to electronic sensing and storage of climate data in high temporal resolution, traditional approaches of homogenization are insufficient for addressing the small-scale variability and spatial heterogeneity of the data. This problem can be successfully addressed by introducing a new class of control procedures based on the physical and climatological relations between different climate variables. The new approach utilizes knowledge about the interdependency of air temperature, precipitation, radiation, relative air humidity, cloud cover, and visibility to develop empirical functions for determining the probability margins for the co-occurrence of specific conditions in tropical mountains and deserts. It can also be applied to other geographic settings by adjusting the parameters derived from the data itself. All procedures are integrated into a processing chain with feedback loops and combined with conventional logical and statistical checks, which enables it to detect small errors that normally pass unnoticed. The algorithms are also adapted to incorporate the short time steps of the original data to retain the potential for detailed process analyses.}, language = {en} } @misc{MakowskiGiannoniRollenbeckTrachteetal., author = {Makowski Giannoni, Sandro and Rollenbeck, R{\"u}tger and Trachte, Katja and Bendix, J{\"o}rg}, title = {Natural or anthropogenic? On the origin of atmospheric sulfate deposition in the Andes of southeastern Ecuador}, series = {Atmospheric Chemistry and Physics}, volume = {14}, journal = {Atmospheric Chemistry and Physics}, number = {20}, doi = {10.5194/acp-14-11297-2014}, pages = {11297 -- 11312}, abstract = {Atmospheric sulfur deposition above certain limits can represent a threat to tropical forests, causing nutrient imbalances and mobilizing toxic elements that impact biodiversity and forest productivity. Atmospheric sources of sulfur deposited by precipitation have been roughly identified in only a few lowland tropical forests. Even scarcer are studies of this type in tropical mountain forests, many of them megadiversity hotspots and especially vulnerable to acidic deposition. In these places, the topographic complexity and related streamflow conditions affect the origin, type, and intensity of deposition. Furthermore, in regions with a variety of natural and anthropogenic sulfur sources, like active volcanoes and biomass burning, no source emission data has been used for determining the contribution of each source to the deposition. The main goal of the current study is to evaluate sulfate (SO-4) deposition by rain and occult precipitation at two topographic locations in a tropical mountain forest of southern Ecuador, and to trace back the deposition to possible emission sources applying back-trajectory modeling. To link upwind natural (volcanic) and anthropogenic (urban/industrial and biomass-burning) sulfur emissions and observed sulfate deposition, we employed state-of-the-art inventory and satellite data, including volcanic passive degassing as well. We conclude that biomass-burning sources generally dominate sulfate deposition at the evaluated sites. Minor sulfate transport occurs during the shifting of the predominant winds to the north and west. Occult precipitation sulfate deposition and likely rain sulfate deposition are mainly linked to biomass-burning emissions from the Amazon lowlands. Volcanic and anthropogenic emissions from the north and west contribute to occult precipitation sulfate deposition at the mountain crest Cerro del Consuelo meteorological station and to rain-deposited sulfate at the upriver mountain pass El Tiro meteorological station.}, language = {en} } @misc{YiZhangThiesetal., author = {Yi, L. and Zhang, S.P. and Thies, B. and Shi, X.M. and Trachte, Katja and Bendix, J{\"o}rg}, title = {Spatio-temporal detection of fog and low stratus top heights over the Yellow Sea with geostationary satellite data as a precondition for ground fog detection — A feasibility study}, series = {Atmospheric Research}, volume = {151}, journal = {Atmospheric Research}, issn = {0169-8095}, doi = {10.1016/j.atmosres.2014.03.020}, pages = {212 -- 223}, abstract = {An accurate cloud top retrieval from geostationary (GEO) and low earth orbit (LEO) platforms is still a pending problem. This particularly holds for low level clouds. Furthermore, cloud top height is a crucial parameter to calculate cloud immersion of underlying terrain from GEO/LEO data and thus, for the discrimination between low level stratus and ground fog, where the latter is a main obstruction for air, land and sea traffic. All problems are particularly evident for ocean areas such as the Yellow Sea where no ground observations are available. In this paper, a novel method is presented to retrieve low stratus/fog top heights with special reference to the Yellow Sea and its surroundings, based on GEO data of MTSAT-1 and MTSAT-2 (JAMI sensor) and LEO data (MODIS sensor on Terra and Aqua) using the infrared (IR) water vapor and split-window bands. Two cases with very good data coverage are discussed where the retrieved low stratus/fog heights are compared to CALIPSO cloud top heights, and simulated data using the mesoscale model WRF. The comparison of JAMI retrievals with the spatial data sources used shows an encouraging accuracy (root-mean-square error, RMSE, around 300 m) in comparison to other retrieval schemes base on IR data hitherto published. A validation of the retrievals for the position of two radiosonde stations using available sounding data of seven foggy days revealed an even better performance with an average deviation of 184 m (standard deviation of 132 m). However, the validation revealed that the application of the underlying equations to retrieve inversion strength and thickness under foggy conditions would need some adjustments because the equations taken from the work of Liu and Key (2003) were originally developed for clear sky situations. Thus, the adaptation of the original scheme during future work should especially address cloudy conditions under moderate inversion strengths which could lead to an improvement of the retrieval accuracy.}, language = {en} } @misc{JuhlkeGeldernBarthetal., author = {Juhlke, Tobias R. and Geldern, Robert van and Barth, Johannes A. C. and Bendix, J{\"o}rg and Br{\"a}uning, Achim and Garel, Emilie and H{\"a}usser, Martin and Huneau, Fr{\´e}d{\´e}ric and Knerr, Isabel and Santoni, S{\´e}bastien and Szymczak, Sonja and Trachte, Katja}, title = {Temporal offset between precipitation and water uptake of Mediterranean pine trees varies with elevation and season}, series = {Science of the Total Environment}, volume = {755}, journal = {Science of the Total Environment}, number = {2}, doi = {10.1016/j.scitotenv.2020.142539}, pages = {12}, abstract = {For climate models that use paleo-environment data to predict future climate change, tree-ring isotope variations are one important archive for the reconstruction of paleo-hydrological conditions. Due to the rather complicated pathway of water, starting from precipitation until its uptake by trees and the final incorporation of its components into tree-ring cellulose, a closer inspection of seasonal variations of tree water uptake is important. In this study, branch and needle samples of two pine species (Pinus pinaster and Pinus nigra subsp. laricio) and several water compartments (precipitation, creek, soil) were sampled over a two-year period and analyzed for the temporal variations of their oxygen and hydrogen stable isotope ratios (δ18O and δ2H) at five sites over an elevation gradient from sea level to around 1600 m a.s.l. on the Mediterranean island of Corsica (France). A new model was established to disentangle temporal relationships of source water uptake of trees. It uses a calculation method that incorporates the two processes mostly expected to affect source water composition: mixing of waters and evaporation. The model results showed that the temporal offset from precipitation to water uptake is not constant and varies with elevation and season. Overall, seasonal source water origin was shown to be dominated by precipitation from autumn and spring. While autumn precipitation was a more important water source for trees growing at mid- (~800-1000 m a.s.l) and high-elevation (~1600 m a.s.l.) sites, trees at coastal sites mostly took up water from late winter and spring. These findings show that predicted decreases in precipitation amounts during the wet season in the Mediterranean can have strong impacts on water availability for pine trees, especially at higher elevations.}, language = {en} } @misc{UrgilesCelleriTrachteetal., author = {Urgil{\´e}s, Gabriela and C{\´e}lleri, Rolando and Trachte, Katja and Bendix, J{\"o}rg and Orellana-Alvear, Johanna}, title = {Clustering of Rainfall Types Using Micro Rain Radar and Laser Disdrometer Observations in the Tropical Andes}, series = {Remote Sensing}, volume = {13}, journal = {Remote Sensing}, number = {5}, doi = {10.3390/rs13050991}, pages = {22}, abstract = {Lack of rainfall information at high temporal resolution in areas with a complex topography as the Tropical Andes is one of the main obstacles to study its rainfall dynamics. Furthermore, rainfall types (e.g., stratiform, convective) are usually defined by using thresholds of some rainfall characteristics such as intensity and velocity. However, these thresholds highly depend on the local climate and the study area. In consequence, these thresholds are a constraining factor for the rainfall class definitions because they cannot be generalized. Thus, this study aims to analyze rainfall-event types by using a data-driven clustering approach based on the k-means algorithm that allows accounting for the similarities of rainfall characteristics of each rainfall type. It was carried out using three years of data retrieved from a vertically pointing Micro Rain Radar (MRR) and a laser disdrometer. The results show two main rainfall types (convective and stratiform) in the area which highly differ in their rainfall features. In addition, a mixed type was found as a subgroup of the stratiform type. The stratiform type was found more frequently throughout the year. Furthermore, rainfall events of short duration (less than 70 min) were prevalent in the study area. This study will contribute to analyze the rainfall formation processes and the vertical profile.}, language = {en} } @misc{TrachteBendix, author = {Trachte, Katja and Bendix, J{\"o}rg}, title = {Katabatic Flows and Their Relation to the Formation of Convective Clouds—Idealized Case Studies}, series = {Journal of Applied Meteorology and Climatology}, volume = {51}, journal = {Journal of Applied Meteorology and Climatology}, number = {8}, doi = {10.1175/JAMC-D-11-0184.1}, pages = {1531 -- 1546}, abstract = {The formation of a convective cloud system as a result of a katabatic-induced surface cold front at the eastern Andes Mountains of South America was investigated in a numerical model study. The occurrence of this cloud system is hypothesized to be a consequence of converging cold-air drainage from slopes and valleys resulting from the concave shape of the terrain. Simplified terrain configurations were applied to three different atmospheric experiments to determine the influence of the terrain and the ambient stratification on the underlying processes. The simulation demonstrated the occurrence of a convective cloud, but not in every simulation. The initial stable stratification experiment did not initiate convective activity. Further analysis of the development of the convective cells confirmed the terrain's impact, but it also showed a dependence on atmospheric conditions. The katabatic flows and the surface fluxes from which they are induced are sensitive to the ambient stratification, which was seen when only a weak cold front developed in response to a decrease in the surface inversion and the downslope velocity. On the basis of specific characteristics of katabatic flows and the heat-exchange budget, the presence of these flows and their significance as the driving force behind the cloud-formation process were confirmed.}, language = {en} } @misc{SzymczakBarthBendixetal., author = {Szymczak, Sonja and Barth, Johannes A. C. and Bendix, J{\"o}rg and Huneau, Fr{\´e}d{\´e}ric and Garel, Emilie and H{\"a}usser, Martin and Juhlke, Tobias R. and Knerr, Isabel and Santoni, S{\´e}bastien and Mayr, Christoph C. and Trachte, Katja and Geldern, Robert van and Br{\"a}uning, Achim}, title = {First indications of seasonal and spatial variations of water sources in pine trees along an elevation gradient in a Mediterranean ecosystem derived from δ18O}, series = {Chemical Geology}, volume = {2020}, journal = {Chemical Geology}, number = {549}, doi = {10.1016/j.chemgeo.2020.119695}, abstract = {Water availability is the most important factor for the vitality of forest ecosystems, especially in dry environments. The Mediterranean region is one of the hotspots of future climate change; therefore, data on the water cycle are urgently needed. We measured oxygen isotope compositions in creek water, precipitation, stem water, needle water, and tree-ring cellulose over one growing season to establish the relationship between isotope compositions in different compartments along a fractionation pathway. We analyzed plant material from pine trees (Pinus nigra J.F. Arn subsp. laricio (Poiret) Maire var. Corsicana Hyl. and Pinus pinaster Aiton) at five locations along an elevation gradient from sea level to 1600 m asl. We traced back the oxygen isotope composition from source to sink in tree-ring cellulose in order to identify the water sources used by the trees, and to quantify the extent of isotope fractionation processes. Our results showed that the trees used different water sources over the course of the growing season, ranging from winter snow meltwater to summer precipitation at higher sites and deep soil water reservoirs at coastal sites. Needle water enrichment was higher at higher elevation sites than at coastal locations, highlighting the importance of site-specific climate conditions on the isotopic composition values in tree material. Water availability seems to be most restricted at the highest site, making these trees most vulnerable to climate change.}, language = {en} } @misc{SzymczakHaeusserGareletal., author = {Szymczak, Sonja and H{\"a}usser, Martin and Garel, Emilie and Santoni, S{\´e}bastien and Huneau, Fr{\´e}d{\´e}ric and Knerr, Isabel and Trachte, Katja and Bendix, J{\"o}rg}, title = {How Do Mediterranean Pine Trees Respond to Drought and Precipitation Events along an Elevation Gradient}, series = {Forests}, volume = {7}, journal = {Forests}, number = {11}, doi = {10.3390/f11070758}, pages = {17}, abstract = {Drought is a major factor limiting tree growth and plant vitality. In the Mediterranean region,the length and intensity of drought stress strongly varies with altitude and site conditions. We usedelectronic dendrometers to analyze the response of two native pine species to drought and precipitationevents. The five study sites were located along an elevation gradient on the Mediterranean islandof Corsica (France). Positive stem increment in the raw dendrometer measurements was separatedinto radial stem growth and stem swelling/shrinkage in order to determine which part of the trees'response to climate signals can be attributed to growth. Precipitation events of at least 5 mm anddry periods of at least seven consecutive days without precipitation were determined over a periodof two years. Seasonal dynamics of stem circumference changes were highly variable among thefive study sites. At higher elevations, seasonal tree growth showed patterns characteristic for coldenvironments, while low-elevation sites showed bimodal growth patterns characteristic of droughtprone areas. The response to precipitation events was uniform and occurred within the first six hoursafter the beginning of a precipitation event. The majority of stem circumference increases were causedby radial growth, not by stem swelling due to water uptake. Growth-induced stem circumferenceincrease occurred at three of the five sites even during dry periods, which could be attributed tostored water reserves within the trees or the soils. Trees at sites with soils of low water-holdingcapacity were most vulnerable to dry periods.}, language = {en} } @misc{BendixAguireBecketal., author = {Bendix, J{\"o}rg and Aguire, Nicolay and Beck, Erwin and Br{\"a}uning, Achim and Brandl, Roland and Breuer, Lutz and B{\"o}hning‑Gaese, Katrin and Paula, Mateus Dantas de and Hickler, Thomas and Homeier, J{\"u}rgen and Inclan, Diego and Leuschner, Christoph and Neuschulz, Eike L. and Schleuning, Matthias and Suarez, Juan P. and Trachte, Katja and Wilcke, Wolfgang and Windhorst, David and Farwig, Nina}, title = {A research framework for projecting ecosystem change in highly diverse tropical mountain ecosystems}, series = {Oecologia}, volume = {195}, journal = {Oecologia}, number = {3}, issn = {0029-8549}, doi = {10.1007/s00442-021-04852-8}, pages = {589 -- 600}, abstract = {Tropical mountain ecosystems are threatened by climate and land-use changes. Their diversity and complexity make projections how they respond to environmental changes challenging. A suitable way are trait-based approaches, by distinguishing between response traits that determine the resistance of species to environmental changes and effect traits that are relevant for species' interactions, biotic processes, and ecosystem functions. The combination of those approaches with land surface models (LSM) linking the functional community composition to ecosystem functions provides new ways to project the response of ecosystems to environmental changes. With the interdisciplinary project RESPECT, we propose a research framework that uses a trait-based response-effect-framework (REF) to quantify relationships between abiotic conditions, the diversity of functional traits in communities, and associated biotic processes, informing a biodiversity-LSM. We apply the framework to a megadiverse tropical mountain forest. We use a plot design along an elevation and a land-use gradient to collect data on abiotic drivers, functional traits, and biotic processes. We integrate these data to build the biodiversity-LSM and illustrate how to test the model. REF results show that aboveground biomass production is not directly related to changing climatic conditions, but indirectly through associated changes in functional traits. Herbivory is directly related to changing abiotic conditions. The biodiversity-LSM informed by local functional trait and soil data improved the simulation of biomass production substantially. We conclude that local data, also derived from previous projects (platform Ecuador), are key elements of the research framework. We specify essential datasets to apply this framework to other mountain ecosystems.}, language = {en} } @misc{LimbergerHomeierFarwigetal., author = {Limberger, Oliver and Homeier, J{\"u}rgen and Farwig, Nina and Pucha-Cofrep, Franz and Fries, Andreas and Leuschner, Christoph and Trachte, Katja and Bendix, J{\"o}rg}, title = {Classification of Tree Functional Types in a Megadiverse Tropical Mountain Forest from Leaf Optical Metrics and Functional Traits for Two Related Ecosystem Functions}, series = {Forests}, volume = {12}, journal = {Forests}, number = {5}, issn = {1999-4907}, doi = {10.3390/f12050649}, abstract = {Few plant functional types (PFTs) with fixed average traits are used in land surface models (LSMs) to consider feedback between vegetation and the changing atmosphere. It is uncertain if highly diverse vegetation requires more local PFTs. Here, we analyzed how 52 tree species of a megadiverse mountain rain forest separate into local tree functional types (TFTs) for two functions: biomass production and solar radiation partitioning. We derived optical trait indicators (OTIs) by relating leaf optical metrics and functional traits through factor analysis. We distinguished four OTIs explaining 38\%, 21\%, 15\%, and 12\% of the variance, of which two were considered important for biomass production and four for solar radiation partitioning. The clustering of species-specific OTI values resulted in seven and eight TFTs for the two functions, respectively. The first TFT ensemble (P-TFTs) represented a transition from low to high productive types. The P-TFT were separated with a fair average silhouette width of 0.41 and differed markedly in their main trait related to productivity, Specific Leaf Area (SLA), in a range between 43.6 to 128.2 (cm2/g). The second delineates low and high reflective types (E-TFTs), were subdivided by different levels of visible (VIS) and near-infrared (NIR) albedo. The E-TFTs were separated with an average silhouette width of 0.28 and primarily defined by their VIS/NIR albedo. The eight TFT revealed an especially pronounced range in NIR reflectance of 5.9\% (VIS 2.8\%), which is important for ecosystem radiation partitioning. Both TFT sets were grouped along elevation, modified by local edaphic gradients and species-specific traits. The VIS and NIR albedo were related to altitude and structural leaf traits (SLA), with NIR albedo showing more complex associations with biochemical traits and leaf water. The TFTs will support LSM simulations used to analyze the functioning of mountain rainforests under climate change.}, language = {en} } @misc{KnerrTrachteEglietal., author = {Knerr, Isabel and Trachte, Katja and Egli, Sebastian and Barth, Johannes A. C. and Br{\"a}uning, Achim and Garel, Emilie and H{\"a}usser, Martin and Huneau, Fr{\´e}d{\´e}ric and Juhlke, Tobias R. and Santoni, S{\´e}bastien and Szymczak, Sonja and Geldern, Robert van and Bendix, J{\"o}rg}, title = {Fog - low stratus (FLS) regimes on Corsica with wind and PBLH as key drivers}, series = {Atmospheric Research}, volume = {261}, journal = {Atmospheric Research}, issn = {0169-8095}, doi = {10.1016/j.atmosres.2021.105731}, abstract = {The French Mediterranean island of Corsica is already today confronted with a clear tendency towards water shortage, leading not only to socio-economical, but also to ecological problems. A potential, but not very widespread source of water is the presence of near-ground clouds, mostly fog. In this study, we investigate fog-low stratus (FLS) frequencies in Corsica, derived from a data set of Meteosat Second Generation SEVIRI, whereby a distinction between fog and low stratus is hardly feasible using remote sensing data. The FLS frequency was studied with respect to its interaction with distinct locally-generated wind and its dependence on the planetary boundary layer height (PBLH) obtained by ERA5 reanalysis (the fifth generation of the European Centre for Medium-Range Weather Forecasts, ECMWF). Results show that radiation FLS is formed in coastal areas at sunrise, with low PBLH. On the other hand, in the interior of the island at sunset, a maximum of advection FLS is formed, fostered by locally-generated and related transport of moisture. On the east side of the island, FLS frequency is lower throughout the year due to frequent lee situations. This situation is reinforced by reduced synoptic moisture transport by westerly winds, so that westerly exposed slopes benefit from moisture input by FLS formation.}, language = {en} } @misc{HaeusserAryalBarthetal., author = {H{\"a}usser, Martin and Aryal, Sugam and Barth, Johannes A. C. and Bendix, J{\"o}rg and Garel, Emilie and Geldern, Robert van and Huneau, Fr{\´e}d{\´e}ric and Juhlke, Tobias R. and Knerr, Isabel and Santoni, S{\´e}bastien and Szymczak, Sonja and Trachte, Katja and Br{\"a}uning, Achim}, title = {Xylem formation patterns from Mediterranean to subalpine climate conditions reveal high growth plasticity of pine species on Corsica}, series = {Trees}, volume = {37}, journal = {Trees}, number = {4}, publisher = {Springer Berlin Heidelberg}, issn = {0931-1890}, doi = {10.1007/s00468-023-02402-8}, pages = {1027 -- 1039}, abstract = {Investigating seasonal wood formation is crucial to understand tree growth responses to climate impact. The present study quantifies the variability of xylogenesis along an elevation gradient on the Mediterranean island of Corsica, where two native pine species (Pinus nigra Arnold ssp. laricio Maire and Pinus pinaster Aiton) grow from the upper tree line to sea level, partly in sympatry. We extracted microcores from 35 trees at 5 sites along an East-West transect from the coasts (10 m asl) to the island's central mountain ridge (1600 m asl) during bi-weekly sampling campaigns between 2017 and 2019. We applied generalised additive models to detect radial growth differences in elevation and species along with minimum temperatures for growth initiation. We found that trees in low elevations experienced over 2 months longer growth periods with higher maximum growth rates than in high elevations. The results show a 1-month delay for the beginning of tracheid formation between the low, mid and high-elevation belts but comparable timing for its termination. At the sites where both species co-occur, P. nigra accumulates more radial cells in a shorter time than P. pinaster. Trees at the two contrasting coastal sites have similar growth period lengths, but exhibit a time shift of over a month. Minimum temperatures around growth initiation vary between 3.1 °C for P. nigra and 9.9 °C for P. pinaster. These findings emphasise the high plasticity in the growth behaviour of one of the most widespread tree genera in Mediterranean and temperate zones.}, language = {en} } @misc{MurkuteSayeedPuchaCofrepetal., author = {Murkute, Charuta and Sayeed, Mostafa and Pucha-Cofrep, Franz and Carrillo-Rojas, Galo and Homeier, J{\"u}rgen and Limberger, Oliver and Fries, Andreas and Bendix, J{\"o}rg and Trachte, Katja}, title = {Turbulent energy and carbon fluxes in an Andean Montane Forest—energy balance and heat storage}, series = {Forests}, volume = {15}, journal = {Forests}, number = {10}, publisher = {MDPI}, issn = {1999-4907}, doi = {10.3390/f15101828}, abstract = {High mountain rainforests are vital in the global energy and carbon cycle. Understanding the exchange of energy and carbon plays an important role in reflecting responses to climate change. In this study, an eddy covariance (EC) measurement system installed in the high Andean Mountains of southern Ecuador was used. As EC measurements are affected by heterogeneous topography and the vegetation height, the main objective was to estimate the effect of the sloped terrain and the forest on the turbulent energy and carbon fluxes considering the energy balance closure (EBC) and the heat storage. The results showed that the performance of the EBC was generally good and estimated it to be 79.5\%. This could be improved when the heat storage effect was considered. Based on the variability of the residuals in the diel, modifications in the imbalances were highlighted. Particularly, during daytime, the residuals were largest (56.9 W/m 2 on average), with a clear overestimation. At nighttime, mean imbalances were rather weak (6.5 W/m 2 ) and mostly positive while strongest underestimations developed in the transition period to morning hours (down to -100 W/m 2 ). With respect to the Monin-Obukhov stability parameter ((z - d)/L) and the friction velocity (u*), it was revealed that the largest overestimations evolved in weak unstable and very stable conditions associated with large u* values. In contrast, underestimation was related to very unstable conditions. The estimated carbon fluxes were independently modelled with a non-linear regression using a light-response relationship and reached a good performance value (R 2 = 0.51). All fluxes were additionally examined in the annual course to estimate whether both the energy and carbon fluxes resembled the microclimatological conditions of the study site. This unique study demonstrated that EC measurements provide valuable insights into land-surface-atmosphere interactions and contribute to our understanding of energy and carbon exchanges. Moreover, the flux data provide an important basis to validate coupled atmosphere ecosystem models.}, language = {en} } @misc{GrigusovaLimbergerMurkuteetal., author = {Grigusova, Paulina and Limberger, Oliver and Murkute, Charuta and Pucha-Cofrep, Franz and Gonzalez-Jaramillo, Victor Hugo and Fries, Andreas and Windhorst, David and Breuer, Lutz and Dantas de Paula, Mateus and Hickler, Thomas and Trachte, Katja and Bendix, J{\"o}rg}, title = {Radiation partitioning in a cloud-rich tropical mountain rain forest of the S-Ecuadorian Andes for use in plot-based land surface modelling}, series = {Dynamics of atmospheres and oceans : planetary fluid, climatic and biogeochemical systems}, volume = {110}, journal = {Dynamics of atmospheres and oceans : planetary fluid, climatic and biogeochemical systems}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0377-0265}, doi = {10.1016/j.dynatmoce.2025.101553}, pages = {1 -- 16}, abstract = {Understanding the partitioning of downward shortwave radiation into direct and diffuse components is essential for modeling ecosystem energy fluxes. Accurate partitioning functions are critical for land surface models (LSMs) coupled with climate models, yet these functions often depend on regional cloud and aerosol conditions. While data for developing semi-empirical partitioning functions are abundant in mid-latitudes, their performance in tropical regions, particularly in the high Andes, remains poorly understood due to scarce ground-based measurements. This study analyzed a unique dataset of shortwave radiation components from a tropical mountain rainforest (MRF) in southern Ecuador, developing and testing a locally adapted partitioning function using Random Forest Regression. The model achieved high accuracy in predicting the percentage of diffuse radiation (\%Dif; R²=0.95, RMSE = 5.33, MAE = 3.74) and absolute diffuse radiation (R²=0.99, RMSE = 5.30, MAE = 14). When applied to simulate upward shortwave radiation, the model outperformed commonly used partitioning functions achieving the lowest RMSE (8.62) and MAE (5.82) while matching the highest R² (0.97). These results underscore the importance of regionally adapted radiation partitioning functions for improving LSM performance, particularly in complex tropical environments. The adapted LSM will be further utilized for studies on heat fluxes and carbon sequestration.}, language = {en} } @misc{BendixLimburgerBreueretal., author = {Bendix, J{\"o}rg and Limburger, Oliver and Breuer, Lutz and Dantas de Paula, Mateus and Fries, Andreas and Gonzalez-Jaramillo, Victor Hugo and Grigusova, Paulina and Hickler, Thomas and Murkute, Charuta and Pucha-Cofrep, Franz and Trachte, Katja and Windhorst, David}, title = {Simulation of latent heat flux over a high altitude pasture in the tropical Andes with a coupled land surface framework}, series = {The science of the total environment}, volume = {981}, journal = {The science of the total environment}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1879-1026}, doi = {10.1016/j.scitotenv.2025.179510}, pages = {1 -- 21}, abstract = {Latent heat flux is a central element of land-atmosphere interactions under climate change. Knowledge is particularly poor in the biodiversity hotspot of the Andes, where heat flux measurements using eddy covariance stations are scarce and land surface models (LSMs) often oversimplify the complexity of the ecosystems. The main objective of this study is to perform latent heat flux simulations for the tropical South Eastern (SE) Ecuadorian Andes using a coupled LSM framework, and to test the performance with heat flux and soil moisture data collected from a tropical high-altitude pasture. Prior to testing, we applied multi-criteria model calibration of sensitive model parameters, focusing on improving simulated soil water conditions and radiation fluxes as a prerequisite for proper heat flux simulations. The most sensitive parameters to improve soil moisture and radiation flux simulations were soil porosity, saturated hydraulic conductivity, leaf area index, soil colour and NIR (Near Infrared) leaf optical properties. The best calibrated model run showed a very good performance for half-hourly latent heat flux simulations with an R² of 0.8 and an RMSE of 34.0 W m⁻², outperforming simulations with uncalibrated and uncoupled LSM simulations in comparable areas. The slight overall overestimation in the simulated latent heat flux can be related to (i) simulation uncertainties in the canopy heat budget, (ii) an imbalance in the observed flux data and (iii) slight overestimations in the simulated soil moisture. Although our study focuses on latent heat fluxes and their relation to simulated radiation fluxes and soil moisture, model outputs of sensible heat fluxes were also discussed. The systematic overestimation of sensible heat flux in the model seems to be mainly a result of overestimated canopy temperatures. The improved simulation for latent heat flux has a high translational potential to support land use strategies in the tropical Andes under climate change.}, language = {en} } @misc{LimbergerHomeierGonzalezJaramilloetal., author = {Limberger, Oliver and Homeier, J{\"u}rgen and Gonzalez-Jaramillo, Victor and Fries, Andreas and Murkute, Charuta and Trachte, Katja and Bendix, J{\"o}rg}, title = {Foliar trait retrieval models based on hyperspectral satellite imagery perform well in a biodiversity hotspot of the SE Ecuadorian Andes}, series = {International journal of remote sensing}, journal = {International journal of remote sensing}, publisher = {Taylor \& Francis}, address = {London}, issn = {1366-5901}, doi = {10.1080/01431161.2025.2511211}, pages = {1 -- 19}, abstract = {The determination of the spatial distribution of canopy traits is crucial for understanding the spatio-temporal dynamics of ecosystem functions, such as carbon sequestration, water and energy fluxes in tropical montane forests. Especially in remote areas such as the Andes of south-east Ecuador, remote sensing using satellites has been proven to provide valuable information on canopy traits. However, the performance of the multispectral models to date is limited. Here, we analyse the potential of DESIS (DLR Earth Sensing Imaging Spectrometer) hyperspectral surface reflectance data for the prediction of specific leaf area (SLA), foliar toughness, nitrogen (N) and phosphorus (P) content by calibrating a PLSR model for each foliar trait. Model validation showed a high explanation of variance (R2 : 0.78-0.92) and a low model error (mean-normalized RMSE: 8-13\%) for all traits, showing an improved performance compared to models based on multispectral imagery and ancillary data within the same forest type. Hyperspectral models predicting foliar traits from individual tree crowns showed a lower performance for most traits, probably related to the difference in spatial resolution compared to this study. Given the high species richness of the Andean biodiversity hotspot and the complex topography, the high quality of the DESIS models is remarkable, considering that the multispectral models from the region require topographic predictors in addition to reflectances to achieve a good performance. The spatial trait maps generated by our models based on the reflectances only show clear relationships with terrain elevation. Thus, the hyperspectral trait maps from satellite orbit are capable of supporting large-scale ecological analyses between features, diversity and ecosystem functions.}, language = {en} }