Fluorescence from atmospheric aerosol detected by a lidar indicates biogenic particles in the stratosphere

International audienceWith a lidar system that was installed in Lindenberg/Germany, we observed in June 2003, an extended aerosol layer at 13 km altitude in the lowermost stratosphere. This layer created an inelastic backscatter signal which we interpret as laser induced fluorescence from aerosol particles. Also, we find evidence for inelastic scattering in a smoke plume from a forest fire that we observed in the troposphere. Fluorescence from ambient aerosol had not yet been considered detectable by lidar. However, organic compounds such as polycyclic aromatic hydrocarbons sticking to the aerosol particles, or bioaerosol such as bacteria, spores or pollen fluoresce when excited with UV-radiation in a way that is detectable by our lidar system. Therefore, we conclude that fluorescence from organic material released by biomass burning creates the inelastic backscatter signal that we measured with our instrument and thus demonstrate a new and powerful way to characterize aerosols by a remote sensing technique. The stratospheric aerosol layer that we have observed in Lindenberg for three consecutive days is likely to be a remnant from Siberian forest fire plumes lifted across the tropopause and transported around the globe

Die Fertigung als Versuchsfeld fuer die qualitaetsgerechte Produktoptimierung

Available from TIB Hannover: RN 2441(95) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Ship-borne FTIR measurements of CO and O3 in the Western Pacific from 43°N to 35°S: an evaluation of sources

Carbon monoxide (CO) and ozone (O3) have been measured in the Western Pacific (43° N to 35° S) during a ship campaign with Research Vessel Sonne in fall 2009. Observations have been performed using ship-based solar absorption Fourier Transform infrared spectrometry, flask sampling, balloon sounding, and in-situ Fourier Transform infrared analysis. The results obtained are compared to the GEOS-Chem global 3-D chemistry transport model for atmospheric composition. In general, a very good agreement is found between the GEOS-Chem model and all instruments. The CO and O3 distributions show a comparable variability suggesting an impact from the same source regions. Tagged-CO simulations implemented in the GEOS-Chem model make it possible to differentiate between different source processes and source regions. The source regions are verified with HYSPLIT backward trajectory calculations. In the Northern Hemisphere fossil fuel combustion in Asia is the dominant source. European and North American fossil fuel combustion also contribute to Northern Hemispheric CO pollution. In the Southern Hemisphere contributions from biomass burning and fossil fuel combustion are dominant; African biomass burning has a significant impact on Western Pacific CO pollution. Furthermore, in the tropical Western Pacific enhanced upper tropospheric CO within the tropical tropopause layer mainly originates from Indonesian fossil fuel combustion and can be transported into the stratosphere. The source regions of the measured O3 pollution are simulated with a tagged-O3 simulation implemented in the GEOS-Chem model. Similar source regions compared to the tagged-CO simulations are identified by the model. In the Northern Hemisphere contributions from Asia, Europe, and North America are significant. In the Southern Hemisphere emissions from South America, south-east Africa, and Oceania significantly contribute to the measured O3 pollution

First ground-based FTIR observations of methane in the inner tropics over several years

Total column concentrations of methane have been retrieved from ground-based solar absorption FTIR spectra in the near-infrared recorded in Paramaribo (Suriname). The methane FTIR observations are compared with TM5 model simulations and satellite observations from SCIAMACHY, and represent the first validation of SCIAMACHY retrievals in the inner tropics using ground-based remote sensing techniques. Apart from local biomass burning features, our methane FTIR observations agree well with TM5 model simulations. The comparison of the direct measured CH<sub>4</sub>/CO<sub>2</sub> ratios by FTIR and satellite reveals that the satellite can hardly detect methane emissions of tropical biomass burning due to the used retrieval method

Subvisible cirrus clouds in the upper troposphere: a comparison of lidar observations with ECMWF operational analysis data

With the Mobile Aerosol Raman Lidar (MARL) of the AlfredWegener Institute (AWI) we participated in a field campaign at mid latitudes (Lindenberg/Germany, 53°N, 15°E) from May to October 2003. During the frequent good weather periods of that unusual summer we observed a relatively high fraction (55 %) of coverage with thincirrus. By means of a video camera we kept track of persistent contrails which occurred simultaneously with subvisible cirrus and which were often embedded inside the clouds. The cloudiness and the ice water content calculated by the ECMWF operational analysis agree in many cases remarkably well with the lidar observations. This is surprising since the ECMWF cloud formation scheme does not account for high supersaturation. As recently shown, such high supersaturations occur frequently in the upper troposphere. We will present an assessment of the most likely formationpath for ice clouds in the upper troposphere based on backward trajectories, model data and our lidar observations