Comparison of two distinct earthcare multi spectral imager simulators

Kurzfassung

The Earth Cloud-Aerosol-Radiation Explorer (EarthCARE) is a multi-instrument satellite mission of the ESA Earth Explorer Core missions, which will be launched in 2013. EarthCARE will observe the atmosphere in order to better understand the interactions between clouds and aerosols with respect to solar radiation and to their feedbacks on the climate system. One of the four instruments onboard the EarthCARE satellite, the Multi Spectral Imager (MSI), will passively observe the atmosphere using 7 channels at visible and thermal infrared wavelengths. This imager observes with a swath-width of 150 km and a pixel resolution of 0.5 km. The MSI observations will produce the data needed for describing the horizontal spatial distribution of cloud optical and microphysical properties. In order to prepare for the EarthCARE mission configuration and for the required retrieval algorithms, ESA developed the EarthCare SIMulator (ECSIM). ECSIM is a tool capable to simulate the four instruments onboard EarthCARE for the same cloud scene simultaneously. For the evaluation of the ECSIM-MSI, we present a comparison of the ECSIM 3-Dimensional MSI simulations against simulations of the well tested ”Monte Carlo code for the Physically correct tracing of photons in the cloudy atmosphere” (MYSTIC), which is part of the libRadtran radiative transfer package. Both simulations are based on an identical input provided by the Numerical Weather Prediction (NWP) model COSMO-DE developed at the German Weather Service. Differences in the radiative transfer models and in the simulated radiances will be discussed. The two simulators show good ability in simulating the reflectances coming from the modelled cloud scene. Furthermore, with this work we show that both simulators, ECSIM and LibRadtran/MYSTIC, are also suitable to simulate large cloud scenes with high spatial resolution.