TY - GEN A1 - Makowski Giannoni, Sandro A1 - Trachte, Katja A1 - Rollenbeck, Rütger A1 - Lehnert, Lukas W. A1 - Fuchs, Julia A1 - Bendix, Jörg T1 - Atmospheric salt deposition in a tropical mountain rainforest at the eastern Andean slopes of south Ecuador – Pacific or Atlantic origin? T2 - Atmospheric Chemistry and Physics N2 - 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. Y1 - 2016 U6 - https://doi.org/10.5194/acp-16-10241-2016 VL - 16 IS - 15 SP - 10241 EP - 10261 ER - TY - GEN A1 - Lehnert, Lukas W. A1 - Wesche, Karsten A1 - Trachte, Katja A1 - Reudenbach, Christoph A1 - Bendix, Jörg T1 - Climate variability rather than overstocking causes recent large scale cover changes of Tibetan pastures T2 - Scientific Reports N2 - 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. Y1 - 2016 U6 - https://doi.org/10.1038/srep24367 VL - 6 IS - 1 ER - TY - GEN A1 - Campozano, Lenin A1 - Célleri, Rolando A1 - Trachte, Katja A1 - Bendix, Jörg A1 - Samaniego, Esteban T1 - Rainfall and Cloud Dynamics in the Andes: A Southern Ecuador Case Study T2 - Advances in Meteorology N2 - 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. Y1 - 2016 U6 - https://doi.org/10.1155/2016/3192765 VL - 2016 ER - TY - GEN A1 - Trachte, Katja A1 - Bissolli, Peter A1 - Nitsche, H. A1 - Parker, David A1 - Kennedy, John A1 - Kendon, Mike T1 - Regional climates. Europe and the Middle East T2 - State of the Climate in 2014, Special Supplement to the Bulletin of the American Meteorological Society, Vol. 96, No. 7, July 2015 N2 - Most of the dozens of essential climate variables monitored each year in this report continued to follow their long-term trends in 2014, with several setting new records. Carbon dioxide, methane, and nitrous oxide—the major greenhouse gases released into Earth’s atmosphere—once again all reached record high average atmospheric concentrations for the year. Carbon dioxide increased by 1.9 ppm to reach a globally averaged value of 397.2 ppm for 2014. Altogether, 5 major and 15 minor greenhouse gases contributed 2.94 W m–2 of direct radiative forcing, which is 36% greater than their contributions just a quarter century ago. Accompanying the record-high greenhouse gas concentrations was nominally the highest annual global surface temperature in at least 135 years of modern record keeping, according to four independent observational analyses. The warmth was distributed widely around the globe's land areas, Europe observed its warmest year on record by a large margin, with close to two dozen countries breaking their previous national temperature records; many countries in Asia had annual temperatures among their 10 warmest on record; Africa reported above-average temperatures across most of the continent throughout 2014; Australia saw its third warmest year on record, following record heat there in 2013; Mexico had its warmest year on record; and Argentina and Uruguay each had their second warmest year on record. Eastern North America was the only major region to observe a below-average annual temperature. But it was the oceans that drove the record global surface temperature in 2014. Although 2014 was largely ENSO-neutral, the globally averaged sea surface temperature (SST) was the highest on record. The warmth was particularly notable in the North Pacific Ocean where SST anomalies signaled a transition from a negative to positive phase of the Pacific decadal oscillation. In the winter of 2013/14, unusually warm water in the northeast Pacific was associated with elevated ocean heat content anomalies and elevated sea level in the region. Globally, upper ocean heat content was record high for the year, reflecting the continued increase of thermal energy in the oceans, which absorb over 90% of Earth’s excess heat from greenhouse gas forcing. Owing to both ocean warming and land ice melt contributions, global mean sea level in 2014 was also record high and 67 mm greater than the 1993 annual mean, when satellite altimetry measurements began. Sea surface salinity trends over the past decade indicate that salty regions grew saltier while fresh regions became fresher, suggestive of an increased hydrological cycle over the ocean expected with global warming. As in previous years, these patterns are reflected in 2014 subsurface salinity anomalies as well. With a now decade-long trans-basin instrument array along 26°N, the Atlantic meridional overturning circulation shows a decrease in transport of –4.2 ± 2.5 Sv decade–1. Precipitation was quite variable across the globe. On balance, precipitation over the world’s oceans was above average, while below average across land surfaces. Drought continued in southeastern Brazil and the western United States. Heavy rain during April–June led to devastating floods in Canada’s Eastern Prairies. Above-normal summer monsoon rainfall was observed over the southern coast of West Africa, while drier conditions prevailed over the eastern Sahel. Generally, summer monsoon rainfall over eastern Africa was above normal, except in parts of western South Sudan and Ethiopia. The south Asian summer monsoon in India was below normal, with June record dry. Across the major tropical cyclone basins, 91 named storms were observed during 2014, above the 1981–2010 global average of 82. The Eastern/Central Pacific and South Indian Ocean basins experienced significantly above-normal activity in 2014; all other basins were either at or below normal. The 22 named storms in the Eastern/Central Pacific was the basin's most since 1992. Similar to 2013, the North Atlantic season was quieter than most years of the last two decades with respect to the number of storms, despite the absence of El Niño conditions during both years. In higher latitudes and at higher elevations, increased warming to be visible in the decline of glacier mass balance, increasing permafrost temperatures, and a deeper thawing layer in seasonally frozen soil. In the Arctic, the 2014 temperature over land areas was the fourth highest in the 115-year period of record and snow melt occurred 20–30 days earlier than the 1998–2010 average. The Greenland Ice Sheet experienced extensive melting in summer 2014. The extent of melting was above the 1981–2010 average for 90% of the melt season, contributing to the second lowest average summer albedo over Greenland since observations began in 2000 and a record-low albedo across the ice sheet for August. On the North Slope of Alaska, new record high temperatures at 20-m depth were measured at four of five permafrost observatories. In September, Arctic minimum sea ice extent was the sixth lowest since satellite records began in 1979. The eight lowest sea ice extents during this period have occurred in the last eight years. Conversely, in the Antarctic, sea ice extent countered its declining trend and set several new records in 2014, including record high monthly mean sea ice extent each month from April to November. On 20 September, a record large daily Antarctic sea ice extent of 20.14 × 106 km2 occurred. The 2014 Antarctic stratospheric ozone hole was 20.9 million km2 when averaged from 7 September to 13 October, the sixth smallest on record and continuing a decrease, albeit statistically insignificant, in area since 1998. Y1 - 2015 U6 - https://doi.org/10.1175/2015BAMSStateoftheClimate.1 VL - 96 IS - 7 SP - 191 EP - 200 ER - TY - GEN A1 - Trachte, Katja A1 - Obregon, Andre A1 - Bissolli, Peter A1 - Kennedy, John A1 - Parker, David E. A1 - Trigo, Ricardo M. A1 - Barriopedro, D. E. T1 - Regional climates. Europe and the Middle East T2 - State of the Climate in 2011, Bulletin of the American Meteorological Society N2 - Large-scale climate patterns influenced temperature and weather patterns around the globe in 2011. In particu-lar, a moderate-to-strong La Niña at the beginning of the year dissipated during boreal spring but reemerged during fall. The phenomenon contributed to historical droughts in East Africa, the southern United States, and northern Mexico, as well the wettest two-year period (2010 –11) on record for Australia, particularly remarkable as this follows a decade-long dry period. Precipitation patterns in South America were also influenced by La Niña. Heavy rain in Rio de Janeiro in January triggered the country’s worst floods and landslides in Brazil’s history. The 2011 combined average temperature across global land and ocean surfaces was the coolest since 2008, but was also among the 15 warmest years on record and above the 1981–2010 average. The global sea surface temperature cooled by 0.1°C from 2010 to 2011, associ-ated with cooling influences of La Niña. Global integrals of upper ocean heat content for 2011 were higher than for all prior years, demonstrating the Earth’s dominant role of the oceans in the Earth’s energy budget. In the upper atmosphere, tropical stratospheric temperatures were anomalously warm, while polar temper atures were anomalously cold. This led to large spring time stratospheric ozone reductions in polar latitudes in both hemispheres. Ozone concentrations in the Arctic strato-sphere during March were the lowest for that period since satellite records began in 1979. An extensive, deep, and persistent ozone hole over the Antarctic in September indicates that the recovery to pre-1980 conditions is proceeding very slowly.Atmospheric carbon dioxide concentrations increased by 2.10 ppm in 2011, and exceeded 390 ppm for the first time since instrumental records began. Other greenhouse gases also continued to rise in concentration and the combined effect now represents a 30% increase in radia-tive forcing over a 1990 baseline. Most ozone depleting substances continued to fall. The global net ocean carbon dioxide uptake for the 2010 transition period from El Niño to La Niña, the most recent period for which analyzed data are available, was estimated to be 1.30 Pg C yr-1, almost 12% below the 29-year long-term average. Relative to the long-term trend, global sea level dropped noticeably in mid-2010 and reached a local minimum in 2011. The drop has been linked to the La Nina conditions that prevailed throughout much of 2010–11. Global sea level increased sharply during the second half of 2011. Global tropical cyclone activity during 2011 was well-below average, with a total of 74 storms compared with the 1981–2010 average of 89. Similar to 2010, the North Atlantic was the only basin that experienced above-normal activity.For the first year since the widespread introduction of the Dvorak intensity-estimation method in the 1980s, only three tropical cyclones reached Category 5 intensity level—all in the Northwest Pacific basin.The Arctic continued to warm at about twice the rate compared with lower latitudes. Below-normal summer snowfall, a decreasing trend in surface albedo, and above-average surface and upper air temperatures resulted in a continued pattern of extreme surface melting, and net snow and ice loss on the Greenland ice sheet. Warmer-than-normal temperatures over the Eurasian Arctic in spring resulted in a new record-low June snow cover extent and spring snow cover duration in this region. In the Canadian Arctic, the mass loss from glaciers and ice caps was the greatest since GRACE measurements began in 2002, continuing a negative trend that began in 1987. New record high temperatures occurred at 20 m below the land surface at all permafrost observatories on the North Slope of Alaska, where measurements began in the late 1970s. Arctic sea ice extent in September 2011 was the second-lowest on record, while the extent of old ice (four and five years) reached a new record minimum that was just 19% of normal.On the opposite pole, austral winter and spring tem-peratures were more than 3°C above normal over much of the Antarctic continent.However, winter temperatures were below normal in the northern Antarctic Peninsula, which continued the downward trend there during the last 15 years. In summer, an all-time record high tempera-ture of -12.3°C was set at the South Pole station on 25 December, exceeding the previous record by more than a full degree. Antarctic sea ice extent anomalies increased steadily through much of the year, from briefly setting a record low in April, to well above average in December. The latter trend reflects the dispersive effects of low pres-sure on sea ice and the generally cool conditions around the Antarctic perimeter.Unauthenticated | Downloaded 05/07/21 10:23 AM UTC Y1 - 2012 U6 - https://doi.org/10.1175/2012BAMSStateoftheClimate.1 VL - 93 IS - 7 SP - 186 EP - 199 ER - TY - GEN A1 - Bendix, Jörg A1 - Trachte, Katja A1 - Palacios, Enrique A1 - Rollenbeck, Rütger A1 - Göttlicher, Dietrich A1 - Nauss, Thomas A1 - Bendix, Astrid T1 - El Niño meets La Niña – anomalous rainfall patterns in the “traditional” El Niño region of Southern Ecuador T2 - Erdkunde N2 - 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 Niño3 and 1+2 regions, and simulations with the Weather Research and Forecasting (WRF) model. It can be shown that El Niño-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 Niño-like conditions in the El Niño1+2 region during the 2008 La Niña 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 Niño circulation and rainfall patterns as observed during previous El Niño events for the coastal area and La Niña-like conditions for the highlands. The spreading of Pacific instability in the Niño1+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 Niño-like conditions in the eastern tropical Pacific during a La Niña state in the central Pacific is the newest indicator for an impact mode shift regarding severe rainfall anomalies during El Niño/La Niña events in the traditional El Niño area of southern Ecuador since the end of the last century. Since 2000, El Niño events unexpectedly provide below average rainfall while central Pacific La Niña 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 Niño events since 2000 could be due to natural decadal oscillations in the El Niño 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. KW - El Nino KW - La Nina KW - ENSO KW - South Ecuador KW - rainfall anomalies KW - sea surface temperature anomalies Y1 - 2011 U6 - https://doi.org/10.3112/erdkunde.2011.02.04 VL - 65 IS - 2 SP - 151 EP - 167 ER - TY - GEN A1 - Trachte, Katja A1 - Rollenbeck, Rütger A1 - Bendix, Jörg T1 - Nocturnal convective cloud formation under clear‐sky conditions at the eastern Andes of south Ecuador T2 - Journal of Geophysical Research Atmospheres N2 - [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. KW - nocturnal convective clouds KW - downslope winds KW - eastern Andes Y1 - 2010 U6 - https://doi.org/10.1029/2010JD014146 VL - 115 IS - D24 ER - TY - GEN A1 - Trachte, Katja A1 - Nauss, Thomas A1 - Bendix, Jörg T1 - The Impact of Different Terrain Configurations on the Formation and Dynamics of Katabatic Flows: Idealised Case Studies T2 - Boundary-Layer Meteorology N2 - 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. KW - Confluence KW - Katabatic flows KW - Numerical simulation KW - Terrain configuration Y1 - 2010 U6 - https://doi.org/10.1007/s10546-009-9445-8 VL - 134 IS - 2 SP - 307 EP - 325 ER - TY - GEN A1 - Bendix, Jörg A1 - Trachte, Katja A1 - Cermak, Jan A1 - Rollenbeck, Rütger A1 - Nauß, Thomas T1 - Formation of Convective Clouds at the Foothills of the Tropical Eastern Andes (South Ecuador) T2 - Journal of Applied Meteorology and Climatology N2 - 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. KW - Convective clouds KW - Mountain meteorology KW - Diurnal effects Y1 - 2009 U6 - https://doi.org/10.1175/2009JAMC2078.1 VL - 48 IS - 8 SP - 1682 EP - 1695 ER - TY - GEN A1 - Rollenbeck, Rütger A1 - Trachte, Katja A1 - Bendix, Jörg T1 - A New Class of Quality Controls for Micrometeorological Data in Complex Tropical Environments T2 - Journal of Atmospheric and Oceanic Technology N2 - 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. KW - Geographic location/entity KW - South America KW - Physical Meteorology and Climatology KW - Climate variability KW - Observational techniques and algorithms KW - Data processing KW - Data quality control KW - Quality assurance/control KW - Mathematical and statistical techniques KW - Error analysis Y1 - 2015 U6 - https://doi.org/10.1175/JTECH-D-15-0062.1 VL - 33 IS - 1 SP - 169 EP - 183 ER - TY - GEN A1 - Makowski Giannoni, Sandro A1 - Rollenbeck, Rütger A1 - Trachte, Katja A1 - Bendix, Jörg T1 - Natural or anthropogenic? On the origin of atmospheric sulfate deposition in the Andes of southeastern Ecuador T2 - Atmospheric Chemistry and Physics N2 - 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. Y1 - 2014 U6 - https://doi.org/10.5194/acp-14-11297-2014 VL - 14 IS - 20 SP - 11297 EP - 11312 ER - TY - GEN A1 - Yi, L. A1 - Zhang, S.P. A1 - Thies, B. A1 - Shi, X.M. A1 - Trachte, Katja A1 - Bendix, Jörg T1 - 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 T2 - Atmospheric Research N2 - 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. KW - Fog/low stratus top heights KW - Sea fog KW - Yellow Sea KW - Satellite retrieval KW - MTSAT KW - MODIS Y1 - 2014 U6 - https://doi.org/10.1016/j.atmosres.2014.03.020 SN - 0169-8095 VL - 151 SP - 212 EP - 223 ER - TY - GEN A1 - Trachte, Katja A1 - Obregon, Andre A1 - Bissolli, Peter A1 - Nitsche, Helga A1 - Parker, David A1 - Kennedy, John A1 - Kendon, Michael A1 - Trigo, Ricardo M. A1 - Barriopedro, David A1 - Ramos, A. A1 - Sensoy, Serhat A1 - Hovhannisyan, Diana T1 - Regional climates. Europe and the Middle East T2 - State of the Climate in 2013, Bulletin of the American Meteorological Society N2 - 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 Niña or El Niño 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. Y1 - 2014 U6 - https://doi.org/10.1175/2014BAMSStateoftheClimate.1 VL - 95 IS - 7 SP - 181 EP - 193 ER - TY - GEN A1 - Juhlke, Tobias R. A1 - Geldern, Robert van A1 - Barth, Johannes A. C. A1 - Bendix, Jörg A1 - Bräuning, Achim A1 - Garel, Emilie A1 - Häusser, Martin A1 - Huneau, Frédéric A1 - Knerr, Isabel A1 - Santoni, Sébastien A1 - Szymczak, Sonja A1 - Trachte, Katja T1 - Temporal offset between precipitation and water uptake of Mediterranean pine trees varies with elevation and season T2 - Science of the Total Environment N2 - 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. KW - Oxygen isotopes KW - Hydrogen isotopes KW - Mediterranean KW - Soil water KW - Water uptake KW - Pine trees Y1 - 2021 U6 - https://doi.org/10.1016/j.scitotenv.2020.142539 VL - 755 IS - 2 ER - TY - GEN A1 - Urgilés, Gabriela A1 - Célleri, Rolando A1 - Trachte, Katja A1 - Bendix, Jörg A1 - Orellana-Alvear, Johanna T1 - Clustering of Rainfall Types Using Micro Rain Radar and Laser Disdrometer Observations in the Tropical Andes T2 - Remote Sensing N2 - 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. KW - rainfall types KW - k-means KW - micro rain radar KW - laser disdrometer KW - rainfall characteristics KW - tropical Andes Y1 - 2021 U6 - https://doi.org/10.3390/rs13050991 VL - 13 IS - 5 ER - TY - GEN A1 - Wilcke, Wolfgang A1 - Leimer, Sophia A1 - Peters, Thorsten A1 - Emck, Paul A1 - Rollenbeck, Rütger A1 - Trachte, Katja A1 - Valarezo, Carlos T1 - The nitrogen cycle of tropical montane forest in Ecuador turns inorganic under environmental change T2 - Global Biogeochemical Cycles N2 - [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. KW - nitrogen deposition KW - climate change KW - dissolved organic nitrogen KW - nitrogen turnover KW - ecosystem solutions Y1 - 2013 U6 - https://doi.org/10.1002/2012GB004471 VL - 27 IS - 4 SP - 1194 EP - 1204 ER - TY - GEN A1 - Trachte, Katja A1 - Bendix, Jörg T1 - Katabatic Flows and Their Relation to the Formation of Convective Clouds—Idealized Case Studies T2 - Journal of Applied Meteorology and Climatology N2 - 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. KW - South America KW - Convection KW - Density currents KW - Downslope winds KW - Topographic effects KW - Cumulus clouds Y1 - 2012 U6 - https://doi.org/10.1175/JAMC-D-11-0184.1 VL - 51 IS - 8 SP - 1531 EP - 1546 ER - TY - GEN A1 - Szymczak, Sonja A1 - Barth, Johannes A. C. A1 - Bendix, Jörg A1 - Huneau, Frédéric A1 - Garel, Emilie A1 - Häusser, Martin A1 - Juhlke, Tobias R. A1 - Knerr, Isabel A1 - Santoni, Sébastien A1 - Mayr, Christoph C. A1 - Trachte, Katja A1 - Geldern, Robert van A1 - Bräuning, Achim T1 - First indications of seasonal and spatial variations of water sources in pine trees along an elevation gradient in a Mediterranean ecosystem derived from δ18O T2 - Chemical Geology N2 - 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. KW - Oxygen isotopes KW - Pinus nigra KW - Pinus pinaster KW - Needle water enrichment KW - Xylem water KW - Water source Y1 - 2020 U6 - https://doi.org/10.1016/j.chemgeo.2020.119695 VL - 2020 IS - 549 ER - TY - GEN A1 - Szymczak, Sonja A1 - Häusser, Martin A1 - Garel, Emilie A1 - Santoni, Sébastien A1 - Huneau, Frédéric A1 - Knerr, Isabel A1 - Trachte, Katja A1 - Bendix, Jörg T1 - How Do Mediterranean Pine Trees Respond to Drought and Precipitation Events along an Elevation Gradient T2 - Forests N2 - 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. KW - dendrometer; stem circumference changes; climate response; Mediterranean;Pinus nigra;Pinus pinaster Y1 - 2020 U6 - https://doi.org/10.3390/f11070758 VL - 7 IS - 11 ER - TY - GEN A1 - Bendix, Jörg A1 - Aguire, Nicolay A1 - Beck, Erwin A1 - Bräuning, Achim A1 - Brandl, Roland A1 - Breuer, Lutz A1 - Böhning‑Gaese, Katrin A1 - Paula, Mateus Dantas de A1 - Hickler, Thomas A1 - Homeier, Jürgen A1 - Inclan, Diego A1 - Leuschner, Christoph A1 - Neuschulz, Eike L. A1 - Schleuning, Matthias A1 - Suarez, Juan P. A1 - Trachte, Katja A1 - Wilcke, Wolfgang A1 - Windhorst, David A1 - Farwig, Nina T1 - A research framework for projecting ecosystem change in highly diverse tropical mountain ecosystems T2 - Oecologia N2 - 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. KW - Biodiversity-land surface model KW - Functional traits KW - High mountains KW - Research framework KW - Response-effect-framework Y1 - 2021 U6 - https://doi.org/10.1007/s00442-021-04852-8 SN - 0029-8549 SN - 1432-1939 VL - 195 IS - 3 SP - 589 EP - 600 ER -