@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{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{TrachteObregonBissollietal., author = {Trachte, Katja and Obregon, Andre and Bissolli, Peter and Nitsche, Helga and Parker, David and Kennedy, John and Kendon, Michael and Trigo, Ricardo M. and Barriopedro, David and Ramos, A. and Sensoy, Serhat and Hovhannisyan, Diana}, title = {Regional climates. Europe and the Middle East}, series = {State of the Climate in 2013, Bulletin of the American Meteorological Society}, volume = {95}, journal = {State of the Climate in 2013, Bulletin of the American Meteorological Society}, number = {7}, doi = {10.1175/2014BAMSStateoftheClimate.1}, pages = {181 -- 193}, abstract = {In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns around the world. This follows several years dominated by the effects of either La Ni{\~n}a or El Ni{\~n}o events. According to several independent analyses, 2013 was again among the 10 warmest years on record at the global scale, both at the Earth's surface and through the troposphere. Some regions in the Southern Hemisphere had record or near-record high temperatures for the year. Australia observed its hottest year on record, while Argentina and New Zealand reported their second and third hottest years, respectively. In Antarctica, Amundsen-Scott South Pole Station reported its highest annual temperature since records began in 1957. At the opposite pole, the Arctic observed its seventh warmest year since records began in the early 20th century. At 20-m depth, record high temperatures were measured at some permafrost stations on the North Slope of Alaska and in the Brooks Range. In the Northern Hemisphere extratropics, anomalous meridional atmospheric circulation occurred throughout much of the year, leading to marked regional extremes of both temperature and precipitation. Cold temperature anomalies during winter across Eurasia were followed by warm spring temperature anomalies, which were linked to a new record low Eurasian snow cover extent in May. Minimum sea ice extent in the Arctic was the sixth lowest since satellite observations began in 1979. Including 2013, all seven lowest extents on record have occurred in the past seven years. Antarctica, on the other hand, had above-average sea ice extent throughout 2013, with 116 days of new daily high extent records, including a new daily maximum sea ice area of 19.57 million km2 reached on 1 October. ENSO-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific had the largest impacts on the global sea surface temperature in 2013. The North Pacific reached a historic high temperature in 2013 and on balance the globally-averaged sea surface temperature was among the 10 highest on record. Overall, the salt content in nearsurface ocean waters increased while in intermediate waters it decreased. Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 mm yr-1 over the past two decades. A portion of this trend (0.5 mm yr-1) has been attributed to natural variability associated with the Pacific decadal oscillation as well as to ongoing contributions from the melting of glaciers and ice sheets and ocean warming. Global tropical cyclone frequency during 2013 was slightly above average with a total of 94 storms, although the North Atlantic Basin had its quietest hurricane season since 1994. In the Western North Pacific Basin, Super Typhoon Haiyan, the deadliest tropical cyclone of 2013, had 1-minute sustained winds estimated to be 170 kt (87.5 m s-1) on 7 November, the highest wind speed ever assigned to a tropical cyclone. High storm surge was also associated with Haiyan as it made landfall over the central Philippines, an area where sea level is currently at historic highs, increasing by 200 mm since 1970. In the atmosphere, carbon dioxide, methane, and nitrous oxide all continued to increase in 2013. As in previous years, each of these major greenhouse gases once again reached historic high concentrations. In the Arctic, carbon dioxide and methane increased at the same rate as the global increase. These increases are likely due to export from lower latitudes rather than a consequence of increases in Arctic sources, such as thawing permafrost. At Mauna Loa, Hawaii, for the first time since measurements began in 1958, the daily average mixing ratio of carbon dioxide exceeded 400 ppm on 9 May. The state of these variables, along with dozens of others, and the 2013 climate conditions of regions around the world are discussed in further detail in this 24th edition of the State of the Climate series.}, 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{WilckeLeimerPetersetal., author = {Wilcke, Wolfgang and Leimer, Sophia and Peters, Thorsten and Emck, Paul and Rollenbeck, R{\"u}tger and Trachte, Katja and Valarezo, Carlos}, title = {The nitrogen cycle of tropical montane forest in Ecuador turns inorganic under environmental change}, series = {Global Biogeochemical Cycles}, volume = {27}, journal = {Global Biogeochemical Cycles}, number = {4}, doi = {10.1002/2012GB004471}, pages = {1194 -- 1204}, abstract = {[1] Water-bound nitrogen (N) cycling in temperate terrestrial ecosystems of the Northern Hemisphere is today mainly inorganic because of anthropogenic release of reactive N to the environment. In little-industrialized and remote areas, in contrast, a larger part of N cycling occurs as dissolved organic N (DON). In a north Andean tropical montane forest in Ecuador, the N cycle changed markedly during 1998-2010 along with increasing N deposition and reduced soil moisture. The DON concentrations and the fractional contribution of DON to total N significantly decreased in rainfall, throughfall, and soil solutions. This inorganic turn of the N cycle was most pronounced in rainfall and became weaker along the flow path of water through the system until it disappeared in stream water. Decreasing organic contributions to N cycling were caused not only by increasing inorganic N input but also by reduced DON production and/or enhanced DON decomposition. Accelerated DON decomposition might be attributable to less waterlogging and higher nutrient availability. Significantly increasing NO3-N concentrations and NO3-N/NH4-N concentration ratios in throughfall and litter leachate below the thick organic layers indicated increasing nitrification. In mineral soil solutions, in contrast, NH4-N concentrations increased and NO3-N/NH4-N concentration ratios decreased significantly, suggesting increasing net ammonification. Our results demonstrate that the remote tropical montane forests on the rim of the Amazon basin experienced a pronounced change of the N cycle in only one decade. This change likely parallels a similar change which followed industrialization in the temperate zone of the Northern Hemisphere more than a century ago.}, 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} } @incollection{BreuerExbrayatPlescaetal., author = {Breuer, Lutz and Exbrayat, Jean-Fran{\c{c}}ois and Plesca, Ina and Buytaert, Wouter and Ehmann, Theresa and Peters, Thorsten and Timbe, Edison and Trachte, Katja and Windhorst, David}, title = {Global Climate Change Impacts on Local Climate and Hydrology}, series = {Ecosystem Services, Biodiversity and Environmental Change in a Tropical Mountain Ecosystem of South Ecuador}, booktitle = {Ecosystem Services, Biodiversity and Environmental Change in a Tropical Mountain Ecosystem of South Ecuador}, edition = {1}, publisher = {Springer-Verlag GmbH}, address = {Berlin [u.a.]}, isbn = {978-3-642-38137-9}, doi = {10.1007/978-3-642-38137-9_19}, pages = {265 -- 274}, abstract = {An interdisciplinary research unit consisting of 30 teams in the natural, economic and social sciences analyzed biodiversity and ecosystem services of a mountain rainforest ecosystem in the hotspot of the tropical Andes, with special reference to past, current and future environmental changes. The group assessed ecosystem services using data from ecological field and scenario-driven model experiments, and with the help of comparative field surveys of the natural forest and its anthropogenic replacement system for agriculture. The book offers insights into the impacts of environmental change on various service categories mentioned in the Millennium Ecosystem Assessment (2005): cultural, regulating, supporting and provisioning ecosystem services. Examples focus on biodiversity of plants and animals including trophic networks, and abiotic/biotic parameters such as soils, regional climate, water, nutrient and sediment cycles. The types of threats considered include land use and climate changes, as well as atmospheric fertilization. In terms of regulating and provisioning services, the emphasis is primarily on water regulation and supply as well as climate regulation and carbon sequestration. With regard to provisioning services, the synthesis of the book provides science-based recommendations for a sustainable land use portfolio including several options such as forestry, pasture management and the practices of indigenous peoples. In closing, the authors show how they integrated the local society by pursuing capacity building in compliance with the CBD-ABS (Convention on Biological Diversity - Access and Benefit Sharing), in the form of education and knowledge transfer for application.}, 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} } @incollection{TrachteAhmadpour, author = {Trachte, Katja and Ahmadpour, Somayeh}, title = {Europe and the Middle East}, series = {Regional Climates}, volume = {105 (2024)}, booktitle = {Regional Climates}, number = {8}, publisher = {American Meteoroligal Society}, doi = {10.1175/2024BAMSStateoftheClimate_Chapter7.1}, pages = {371 -- 484}, language = {en} } @misc{Trachte, author = {Trachte, Katja}, title = {Recent progress in atmospheric modeling over the Andes - part II: projected changes and modeling challenges}, series = {Sec. Atmospheric Science}, volume = {12 (2024)}, journal = {Sec. Atmospheric Science}, publisher = {Frontiers in Earth Science}, doi = {10.3389/feart.2024.1427837}, pages = {1 -- 21}, language = {en} } @misc{Trachte, author = {Trachte, Katja}, title = {Recent progress in atmospheric modeling over the Andes - part I: review of atmospheric processes}, series = {Atmospheric Science}, volume = {12 (2024)}, journal = {Atmospheric Science}, publisher = {Frontiers in Earth Science}, doi = {10.3389/feart.2024.1427783}, pages = {1 -- 23}, language = {en} } @article{AhmedZaforTrachte, author = {Ahmed, Rezwan and Zafor, Md. Abu and Trachte, Katja}, title = {Land-use and land-cover changes in Cottbus City and Spree-Neisse District, Germany, in the last two decades: a study using remote sensing data and Google Earth Engine}, series = {Remote Sensing}, volume = {16}, journal = {Remote Sensing}, number = {15}, edition = {2nd edition}, publisher = {MDPI AG}, issn = {2072-4292}, doi = {10.3390/rs16152773}, pages = {1 -- 16}, abstract = {Regular detection of land-use and land-cover (LULC) changes with high accuracy is necessary for natural resources management and sustainable urban planning. The produced LULC maps from Google Earth Engine (GEE) also illustrate the transformation of the LULC for the respective landscape over time. The selected study area, Cottbus City and the Spree-Neisse district in northeastern Germany, has undergone significant development over the past decades due to various factors, including urbanization and industrialization; also, the landscape has been converted in some areas for post-mining activities. Detection of LULC changes that have taken place over the last few decades thus plays a vital role in quantifying the impact of these factors while improving the knowledge of these developments and supporting the city planners or urban management officials before implementing further long-term development initiatives for the future. Therefore, the study aims to (i) detect LULC changes for the time slices 2002 and 2022, testing machine learning (ML) algorithms in supervised and unsupervised classification for Landsat satellite imageries, and (ii) validate the newly produced LULC maps with the available regional database (RDB) from the federal and state statistical offices, Germany, and the Dynamic World (DW) near real-time 10 m global LULC data set powered by artificial intelligence (AI). The results of the Random Forest (RF) and the Smilecart classifiers of supervised classification using Landsat 9 OLI-2/TIRS-2 in 2022 demonstrated a validation accuracy of 88\% for both, with Kappa Index (KI) of 83\% and 84\%, respectively. Moreover, the Training Overall Accuracy (TOA) was 100\% for both years. The wekaKMeans cluster of the unsupervised classification also illustrated a similar transformation pattern in the LULC maps. Overall, the produced LULC maps offered an improved representation of the selected region's various land-cover classes (i.e., vegetation, waterbodies, built areas, and bare ground) in the last two decades (20022 to 2022).}, language = {en} }