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UP: Fachverband Umweltphysik

UP 6: Remote sensing and data analysis methods

UP 6.3: Vortrag

Mittwoch, 20. März 2019, 15:00–15:15, HS 22

Impact of three-dimensional cloud-structures on atmospheric trace gas retrievals — •Claudia Emde¹, Arve Kylling², Huan Yu³, Michel van Roozendael³, Bernhard Mayer¹, and Kerstin Stebel² — ¹Meteorological Institute, LMU, Munich — ²Norwegian Institute for Air Research (NILU), Oslo, Norway — ³Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium

Operational retrievals of tropospheric trase gases from space-borne spectrometers are based on one-dimensional radiative transfer models in combination with simplified cloud correction schemes, which do not consider effects like cloud scattering into neighboring pixels or cloud shadowing.

To study the impact of three-dimensional (3D) cloud structures, we have developed the Absorption Lines Importance Sampling (ALIS) method and implemented it into the Monte Carlo radiative transfer model MYSTIC. ALIS allows efficient simulations of radiances in high spectral resolution for 3D model atmospheres including realistic clouds. Furthermore we implemented 3D box-airmass-factor calculations.

Based on 3D cloud fields as model input we simulate spectral radiances for regions relevant for NO2 retrievals: The spectrum between 400 and 500nm includes characteristic NO2 absorption features, and the O2A absorption band between about 755 and 775nm is used for cloud correction. We apply a DOAS retrieval algorithm including a simple cloud correction scheme on the simulated data and by comparing the retrieved NO2 column with the model input, we estimate the error due to cloud scattering.