A cloud climatology based on GOME
Diego Loyola(1), Thomas Ruppert(2), Werner Thomas(3) and Peter Albert(4)
(1) DLR, Oberpfaffenhofen, 82234 Wessling, Germany
(2) DLR, Oberpfaffenhofen, D-82234 Wessling, Germany
(3) DWD, P.O. Box 10 04 65, D-63004 Offenbach , Germany
(4) DWD, P.O. Box 10 04 65 , D-63004 Offenbach , Germany
The precise knowledge of cloud parameters is essential for reliable trace gas measurements. Clouds influence the backscattered solar radiation and prevent the retrieval of trace constituents below them.
Accurate GOME derived cloud parameters are needed for further interpretation and correction of retrieved trace gas results.
The cloud information provided with the operational GOME level 2 products is used to create a global cloud database covering more than 10 years of continuous measurements. The GOME cloud database include the following parameters:
- Cloud Fraction
- Cloud-Top Height (Pressure)
- Cloud-Top Albedo (Optical Thickness)
- Cloud Type
Cloud Fraction represents the GOME pixel area covered by clouds and it is estimated from the GOME Polarization Measurement Devices (PMDs).
Cloud-Top Height and Albedo represent the mean location (km) of the top of the cloud above sea level and the mean cloud albedo at that location. These parameters are estimated from the GOME oxygen A-Band measurements.
Cloud-top pressure and optical thickness are computed from the GOME retrieved cloud-top height and cloud-top albedo respectively. This information is used to assign a cloud type to each GOME pixel following the ISCCP cloud classification scheme:
- High cloud types: Cirrus, Cirrostratus, Deep convective
- Middle cloud types: Altocumulus, Altostratus, Nimbostratus
- Low cloud types: Cumulus, Stratocumulus, Stratus
The GOME derived cloud parameters are compared with ISCCP and MSG data showing an excellent agreement. GOME and MSG data from 2004 show an average difference for cloud fraction of -0.08, for cloud-top height of -0.64 km, and for cloud-top albedo of 0.09. Seasonal patterns of GOME derived cloud type agree well with the ISCCP climatology.
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,