Distinction between clouds and ice/snow covered surfaces in the identification of cloud-free observations using SCIAMACHY PMDs J. M. Krijger, I. Aben, and H. Schrijver SRON, National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
Abstract. SCIAMACHY on ENVISAT allows measurement of different
trace gases including those most abundant in the troposphere (e.g.
CO2, NO2, CH4, BrO, SO2).
However, clouds in the observed scenes can severely hinder the
observation of tropospheric gases.
Several cloud detection algorithms have been developed for GOME on
ERS-2 which can be applied to SCIAMACHY.
The GOME cloud algorithms, however, suffer from the inadequacy of
not being able to distinguish between clouds and ice/snow covered
surfaces because GOME only covers the UV, VIS and part of the NIR
wavelength range (240-790 nm).
As a result these areas are always flagged as clouded, and therefore often not used.
Here a method is presented which uses the SCIAMACHY measurements in
the wavelength range between 450 nm and 1.6 µm to make a
distinction between clouds and ice/snow covered surfaces.
The algorithm is developed using collocated MODIS observations.
The algorithm presented here is specifically developed to identify cloud-free
The SCIAMACHY Polarisation Measurement Devices (PMDs) are used for
this purpose because they provide higher spatial resolution
compared to the main spectrometer measurements.
Citation: Krijger, J. M., Aben, I., and Schrijver, H.: Distinction between clouds and ice/snow covered surfaces in the identification of cloud-free observations using SCIAMACHY PMDs, Atmos. Chem. Phys., 5, 2729-2738, doi:10.5194/acp-5-2729-2005, 2005.