Das Projekt "Water and global Change (WATCH)" wird vom Umweltbundesamt gefördert und von Potsdam-Institut für Klimafolgenforschung e.V. durchgeführt. Der globale Wasserkreislauf ist ein integraler Teil des Erdsystems. Er spielt eine zentrale Rolle in der globalen atmosphärischen Zirkulation, kontrolliert den globalen Energiekreislauf (mittels der latenten Wärme) und hat einen starken Einfluss auf die Kreisläufe von Kohlenstoff, Nährstoffen und Sedimenten. Global gesehen ist das Angebot an Frischwasser bei weitem größer als die menschlichen Bedürfnisse. Allerdings ist davon auszugehen, dass gegen Ende des 21. Jahrhunderts diese Bedürfnisse die gleiche Größenordnung erreichen werden wie das gesamte verfügbare Wasser. Für diverse Regionen jedoch übersteigt der Wasserbedarf (u.a. für die Landwirtschaft sowie die Nutzung in der Industrie und in den Haushalten) schon heute das regionale Angebot. Ansteigende CO2-Konzentrationen und Temperaturen führen zu einer Intensivierung des globalen Wasserkreislaufs und somit zu einem generellen Anstieg von Niederschlag, Abfluss und Verdunstung. Obwohl die Vorhersagen von zukünftigen Niederschlagsänderungen relativ unsicher sind, gibt es deutliche Hinweise, dass einige Regionen, wie z.B. der Mittelmeerraum, mit einer Abnahme des Niederschlags zu rechnen haben, während in einigen äquatornahen Regionen, wie z.B. Indien und der Sahelzone, der Niederschlag zunehmen wird. Hinzu kommt, dass sich auch jahreszeitliche Verläufe ändern könnten, die neue und manchmal auch unerwartete Probleme und Schäden verursachen können. Eine Intensivierung des Wasserkreislaufs bedeutet wahrscheinlich auch einen Anstieg in dessen Extremen, d.h. vor allem Überschwemmungen und Dürren. Es gibt Vermutungen, dass sich auch die interannuale Variabilität erhöhen wird und zwar einhergehend mit einer Intensivierung der El Nino und NAO-Zyklen, was zu mehr Dürren und großskaligen Hochwassersituationen führen würde. Diese Zyklen sind globale Phänomene, die diverse Regionen gleichzeitig beeinflussen, wenngleich dies oft auf verschiedene Art und Weise passiert.
Das Projekt "Ground-based remote sensing measurements of CO2 and CH4 using the moon as light source during the polar night" wird vom Umweltbundesamt gefördert und von Universität Bremen, Institut für Umweltphysik durchgeführt. Throughout the last years measurement techniques have been developed to measure total columns of atmospheric CO2 and CH4 with sufficient precision using the ground-based solar absorption remote sensing spectrometry in the near-infrared spectral region. These observations are internationally organized in the Total Column Carbon Observing Network (TCCON). These observations have been initiated for the satellite validation, because they sample the atmosphere in a similar way as satellites. However, the measurements itself have been found extremely valuable to investigate the sources and sinks of the trace gases, because the interpretation of the ground-based total column data depend to a less extent on assumptions on the vertical mixing in the atmosphere compared to surface in-situ data. We perform such observations at our site in the high Arctic on Spitsbergen (79°N). However, during the polar night from October until mid-March no observations can be performed, because the sun is below the horizon. Since the seasonal cycle of CO2 is largest in the high northern latitudes the lack of total column data for the winter period limits our understanding of the carbon budget. Within this project we plan to modify the measurement and analysis technique to measure the total columns of CO2 and CH4 in the near-infrared using the moon as light source during the polar night. This will allow us to perform observations on +-3 days around full moon, and thus, obtain data throughout the polar night for about three full moon periods. This allows measuring the complete seasonal cycle of total column measurements of CO2 and CH4 in the high Arctic, which is not known so far. Finally, the whole set of data will be compared to the existing in-situ surface data at that site and both data sets, in-situ and total column, will be compared with appropriate models.
Das Projekt "Role of geomagnetic field in atmospheric escape from Earth" wird vom Umweltbundesamt gefördert und von Deutsche Forschungsgemeinschaft durchgeführt. The geomagnetic field prevents the Earth from having its atmosphere swept away by the solar wind. But due to the partial ionization of the upper atmosphere by the sun's short-wavelength radiation electrodynamic forces can move the charged particles upward, against gravity, along open field lines. Already in the early space age it was recognized that considerable amounts of ionospheric ions populate the magnetosphere. In this study we will investigate the acceleration mechanisms of the up-welling ions at source regions altitude. For the first time the role of the neutral particles in the thermosphere are also included in the considerations. For our studies we will make use of data from the satellites CHAMP (400km), GRACE (500km) and DMSP (830km). The space observations shall be augmented by suitable EISCAT radar measurements. As a result the total rates of the different out-flow regions, polar cap, cusp, and auroral region will be quantified and their dependence on geophysical conditions determined.
Das Projekt "Forest dynamics following windthrow in 10 forest districts in Bavaria" wird vom Umweltbundesamt gefördert und von Technische Universität München, Fachgebiet Geobotanik durchgeführt. The storms Vivian and Wiebke, that crossed Central Europe in early spring 1990 (26.2. to 1.3. 1990) destroyed many forest stands in Bavaria. In order to obtain information about the development of natural and planted tree regeneration and vegetation development following windthrow more than fifty permanent observation plots were established in the more heavily affected forest regions of Bavaria. The first record took place in 1991, the second in 1995, and the third in 2000. Data of the development of ground layer vegetation and tree regeneration were recorded together with information on site conditions and structure of the stands. Final analysis of the data will start after finishing the year 2000-record.
Das Projekt "SOLEIL: Solar variability and trend effects in layers and trace gasesin the upper atmosphere" wird vom Umweltbundesamt gefördert und von Leibniz-Institut für Atmosphärenphysik e.V. an der Universität Rostock durchgeführt. In der wissenschaftlichen Klimadiskussion steht der Einfluss des Anstiegs anthropogener Treibhausgase auf die globale Änderung unserer Atmosphäre in den untersten Kilometern im Vordergrund. Allerdings ist die bisher eingetretene mittlere globale Temperaturerhöhung mit 0.85 K von 1880 bis 2012, dies entspricht 0.06 K pro Dekade, jedoch klein. In der Atmosphäre oberhalb von etwa 8 km kehrt sich das Vorzeichen des Treibhauseffekts um: ein Anstieg der Konzentration von infrarot-aktiven Gasen führt zu einer Abkühlung durch eine gesteigerte Emission von Strahlung in den Weltraum. Die globale Veränderung der Atmosphäre findet besonders stark in einem Höhenbereich von 50-75 km statt. Antworten auf die Fragen nach den Ursachen für diese rapiden Änderungen in der mittleren Atmosphäre können uns nur numerische Atmosphärenmodelle (z.B. LIMA) geben. Letztere zeigen, dass die Strahlungsbilanz der mittleren Atmosphäre weitgehend bestimmt wird durch die Spurengase CO2 und O3. Die multivariate Trendanalyse erlaubt nun eine Aussage über den Beitrag am Gesamttrend der einzelnen Spurengase O3 und CO2. Die Spurengase CO2 und O3 tragen jeweils 2/3 bzw. 1/3 zum Trend bei. Die größten Trends liegen im Drucksystem mit 1.3 K/Dekade bei ca. 60 km, während auf geometrischen Höhen der Kontraktionseffekt der Atmosphäre die maximalen Trends auf bis zu 1.8 K/Dekade bei 70 km verstärkt. In den Höhen 80-90 km sind die Trendwerte am kleinsten und können sogar das Vorzeichen wechseln. Dieses Verhalten ist bedingt durch die sehr niedrigen Absoluttemperaturen in 80-90 km Höhe, die sehr empfindlich auf Variationen in den Strahlungsflüssen aus der Stratopausenregion reagieren. Weiterhin konnte in 'SOLEIL' gezeigt werden, dass Temperaturtrends zeitlich variabel sind. So zeigen im Teilzeitraum 1980-1996 die Temperaturen ihren stärksten Abfall aufgrund der Ozonabnahme: die Temperaturtrends können Werte bis zu 4 K pro Dekade erreichen. Im Zeitraum 1995-2009 sind die Durchschnittstemperaturen nahezu unverändert, weil sich hier das stratosphärische Ozon wieder aufbaut ('ozone recovery'). Diese Phasen starker und schwacher Abkühlung zwischen 1961 bis 2008 sind konsistent mit abgeleiteten Temperaturtrends aus französischen Lidarbeobachtungen und Phasenhöhenmessungen am Institut für Atmosphärenphysik (IAP) Kühlungsborn. Der Höhenbereich 80-90 km ist auch die Region, in der Eiswolken seit mehr als 100 Jahren beobachtet werden. Diese Eiswolken (NLC/PMC) existieren in der Sommermesopausenregion polwärts ab 50°N und können sich nur unter sehr kalten Temperaturen unterhalb von etwa 150 K ausbilden. Obwohl der Wasserdampfgehalt in der Mesopausenregion mit 1-7 ppmv sehr gering ausfällt, ist diese Feuchtekonzentration ausreichend für die Bildung von Eisteilchen. Die Nukleation und das Wachstum dieser Eispartikel reagiert sehr empfindlich auf Änderungen der Temperatur und des Wasserdampfes. Aus diesem Grund werden NLC/PMC auf ihre Rolle als potentieller Indikator für Klimaänderungen der globalen Atmosph
Das Projekt "DOAS Messungen von der NASA Global Hawk während des NASA-ATTREX Projektes" wird vom Umweltbundesamt gefördert und von Universität Heidelberg, Institut für Umweltphysik durchgeführt. The present project addresses differential optical absorption spectrometry (DOAS) measurements in scanning limb geometry from aboard the unmanned high-flying aircraft NASA Global Hawk (GH). The DOAS measurements are made within the NASA sponsored ATTREX (Airborne Tropical TRopopause EXperiment) project, by a 3 channel (UV/vis/nearer) optical spectrometer financed by NASA, but mostly built in Heidelberg. In fall 2011 and winter 2012/13 successful flights were already successfully performed and the DOAS instrument peformed. Within ATTREX three field campaigns are planned to take place in the Western Pacific (from EAFB, GUAM, and Darwin) in the years 2013 to 2014 (Jan./Feb. 2013, Jan./Feb. 2014 and June/July 2014). The field campaigns comprise about 50 GH sorties with 600 flight hours spent air-borne. Major scientific foci of the NASA-ATTREX project are the photochemistry, the microphysics of aerosols and cloud particles, and air mass transport into and within the tropical tropopause layer (TTL). The DOAS measurements aim to measure the vertical profiles in the TTL of ozone relevant species such as O3, HONO, NO2, C2H2O2, CH2O, O4, BrO, OClO, IO, and OIO, and of some microphysical properties aerosols and clouds, i.e., the particle phase function, Mie scattering extinction coefficient, the ice water path (IWP) and probably the ice water content (IWC). Together with complementary observations made by other instruments aboard the GH, the DOAS measurements may serve to particularily provide new insights into (a) the photochemistry of halogen oxides (OClO, BrO and IO) in the TTL, in particular on the contribution of so called halogenated Very Short Lived Species (VSLS) to the budgets of stratospheric halogens, (b) the impact of lightning produced NOx and HOx (NO2, and HONO) and other of radicals (c.f. CH2O, BrO, IO) to the oxidation capacity of air in the outflow region of deep convection, and (c) to the abundance and micro-physical properties of frozen aerosols and cloud particles in the upper tropical troposphere and TTL.
Das Projekt "AURORa - Investigation of the Radar Backscatter of Rain Impinging on the Ocean Surface" wird vom Umweltbundesamt gefördert und von Universität Hamburg, Zentrum für Meeres- und Klimaforschung, Institut für Meereskunde (IfM) durchgeführt. Over land, observations of rain rates are more or less operational. To obtain information about precipitation at the coastal zones, weather radars are used. However, over the oceans, especially away from the main shipping routes, no direct precipitation measurements are performed. In these regions, satellite data can provide information about precipitation events. Satellites deploying passive and active microwave sensors can operate independently of cloud cover and time of day. Passive microwave sensors give crude estimates of rain rates over large areas but cannot resolve small-scale rain events of short duration as are often observed in the tropics, for example. Active microwave sensors with high resolutions, such as synthetic aperture radars can provide more reliable information. Though the effect of rain on the atmosphere is a very topical area of research, the radar backscattering mechanisms at the water surface during rain events combined with wind are still not well understood. The purpose of this project is to investigate the radar backscattering from the water surface in the presence of rain and wind in order to interpret satellite radar data produced by active microwave sensors. Furthermore, the results should be embedded into models of the radar backscattering from the water surface to allow for estimating rain rates by using satellite data. Research topics: Rain impinging on a water surfaces generates splash products including crowns, cavities, stalks and secondary drops, which do not propagate, and ring waves and subsurface turbulence. We are investigating this phenomena at the wind-wave tank of the University of Hamburg. The tank is fitted with an artificial rain simulator of 2.3 m2 area mounted 4.5 m over the water surface. Rain drops of 2.1 and 2.9 mm in diameter with rain rates up to 100 mm/h have been produced. Wind with speeds 10 m/s and monomolecular slicks act on the water surface. The influence of the rain on the water surface is measured with a resistance type wire gauge, a two dimensional laser slope gauge and an coherent 9.8 GHz (x band) continuous wave scatterometer operating at VV-, HH- and HV-polarization. The influence of rain below the water surface is measured with colored raindrops which are observed with a video camera to investigate the turbulent motion and the depth of the mixed layer. At the North Sea Port of Buesum in Germany, a scatterometer operating at all polarizations and five frequencies will be mounted during summer of this year. The radar backscatter of the sea surface during rain events will be measured in combination with meteorological observations. With help of these measurements, existing radar backscatter models of the water surface will be improved for the presence of rain events. To validate the improved models, ERS-2 SAR-images will be compared with weather radar data.
Das Projekt "Cirrus-LEWIZ : Cirrus clouds in polewared breaking Rossby waves" wird vom Umweltbundesamt gefördert und von Leibniz-Institut für Atmosphärenphysik e.V. an der Universität Rostock durchgeführt. Aim: - observe cirrus clouds in poleward breaking Rossby waves with LIDAR, - characterised their pathway in the given synoptic situation using analysis data and backward trajectories, - develop a conceptual model for the transport of water vapor in poleward breaking Rossby waves. Activities: - Launching of several field campaigns such as Cirrus-K1, Cirrus-K2 and Cirrus-K3 including radiosonde and LIDAR observations, - Review of Historical LIDAR data. Results: Poleward Rossby wave breaking events have been often observed over the North Atlantic - European region in the upper troposphere in winter time. During a measuring campaign from 13 to 15 February 2006 a special Rossby wave breaking event was investigated with radiosondes and LIDAR observations. The connected horizontal and vertical transport of water vapour in the upper troposphere / lower stratosphere was analysed with backward trajectories. We found that during this poleward Rossby wave breaking event an air mass body has ben formed over central Europe with an extreme low temperature an a very high specific humidity in the tropopause region. The formation is characterised by a strong adiabatic nort-eastward and upward transport of water vapour on the western flank of a stagnation point over Mecklenburg (North German Lowlands). The radiosonde soundings show layers of supersaturated water vapour with respect to ice, but isolated patches of very high cirrus clouds have been clearly identified by LIDAR measurements over Kühlungsborn (54 Grad CN, 11 Grad CE). Based on formed LIDAR measurements from 1997 to 2002 and similar analysis we established the hypothesis that poleward Rossby wave breaking events are connected with north-eastward and upward tropospheric transport of water vapour, forming of supersaturated water vapour over ice and formation of very high cirrus clouds.
Das Projekt "How is the Brewer-Dobson circulation affected by climate change, and which processes are relevant? (SHARP-BDC)" wird vom Umweltbundesamt gefördert und von Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Institut für Physik der Atmosphäre, Abteilung Dynamik der mittleren Atmosphäre durchgeführt. This project aims to identify and quantify dynamical, physical and chemical processes as well as feedback effects affecting the stratospheric circulation (Brewer-Dobson circulation, BDC), which is responsible for transport of stratospheric air masses from tropical to higher latitudes. Climate change is expected to modify the motion and mass exchange rates of air within the stratosphere and therefore the residence time and distribution of chemical substances. Although substantial progress has been achieved in recent years regarding understanding relevant processes affecting the Brewer-Dobson circulation, there are still open issues about atmospheric processes and feedbacks impacting the long-term changes of the BDC. So far, common analyses of observations and results from numerical model simulations do not indicate a consistent picture. Therefore, multi-decadal transient simulations with Atmospheric General Circulation Models, climate models and Chemistry-Climate Models together with assembled, consistent long-term observations (especially derived from space-borne-, balloon-, aircraft- and ground-based instruments) will be further used to investigate atmospheric processes affecting the BDC. Supplementary numerical sensitivity studies with the different models will be performed and interpreted to establish cause and effect relationships. It will be investigated how the relevant processes are going to alter in a changing climate, modifying stratospheric dynamics.
Das Projekt "Tropical High Altitude Clouds and their Impact on Stratospheric Humidity" wird vom Umweltbundesamt gefördert und von Leibniz-Institut für Troposphärenforschung e.V. durchgeführt. Clouds play a key role in the Earth's climate system by regulation of the incoming and outgoing radiation, chemical and dynamical processes. Ice clouds at high altitudes in the tropics, the so called tropical tropopause layer, are particularly important since this is the main region where air ascends slowly from the troposphere into the dry stratosphere. Thus, these ice clouds affect the stratospheric water vapour content which in itself is a main driver of radiative and chemical processes, e.g. ozone depletion, there. These clouds can either be of convective nature, or occur in convective overshooting cloud turrets, or they form in situ by large scale upwelling and cooling as subvisible cirrus. Although the latter occur frequently, little is known about the exact microphysical formation mechanisms and how they can be maintained. Previous modelling efforts using various different mechanisms, however, have failed to agree with the observed properties. This project aims to improve our knowledge of the impact clouds in the tropical tropopause layer have on stratospheric humidity, by studying their formation, maintenance, and occurrence frequencies.A set of state-of-the-art numerical models will be used to simulate the clouds in the tropical tropopause layer, taking advantage of their particular strengths. These models are the Weather Research and Forecasting (WRF) Model, the GLObal Model of Aerosol Processes (GLOMAP), and the Australian Community Climate and Earth-System Simulator (ACCESS). First, the questions related to the formation and maintenance of subvisible cirrus will be addressed. In a second step the impact of subvisible cirrus and overshooting convection on the stratospheric humidity will be assessed. Both the direct effects (e.g. injection of ice particles into the stratosphere) and indirect effects (e.g. change in dynamical processes) will be studied. In order to estimate the net effect, occurrence frequencies of both cloud types will be derived from a complementary set of ground based remote sensing observations from the Darwin site and satellite observation from the International Satellite Cloud Climatology Project. The data of airborne in situ measurements which I analyzed during my PhD will help to constrain and test the model simulations. A better understanding of the complex processes related to the clouds in the tropical tropopause layer will improve their representation in numerical models and thus, enhance the quality of model predictions. This will improve our ability to constrain climate predictions due to highly uncertain ice cloud processes. Additionally, knowing the impact of these clouds on stratospheric humidity will enable an improved quantification of their climate impact.
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