Discriminating raining from non-raining clouds at mid-latitudes using meteosat second generation daytime data B. Thies, T. Nauss, and J. Bendix Laboratory of Climatology and Remote Sensing, University of Marburg, Germany
Abstract. A new method for the delineation of precipitation during daytime using multispectral
satellite data is proposed. The approach is not only applicable to the detection
of mainly convective precipitation by means of the commonly used relation between
infrared cloud top temperature and rainfall probability but enables also the detection
of stratiform precipitation (e.g. in connection with mid-latitude frontal systems).
The presented scheme is based on the conceptual model that precipitating clouds are
characterized by a combination of particles large enough to fall, an adequate
vertical extension (both represented by the cloud water path; cwp), and the
existence of ice particles in the upper part of the cloud. The technique considers
the VIS0.6 and the NIR1.6 channel to gain information about
the cloud water path. Additionally, the brightness temperature differences ΔT8.7-10.8
and ΔT10.8-12.1 are considered to supply information about the cloud phase.
Rain area delineation is realized by using a minimum threshold of the rainfall
confidence. To obtain a statistical transfer function between the rainfall
confidence and the four parameters VIS, NIR1.6, Δ T8.7-10.8
and Δ T10.8-12.1, the value combinations of these four variables
are compared to ground based radar data. The retrieval is validated against independent
radar data not used for deriving the transfer function and shows an encouraging
performance as well as clear improvements compared to existing optical retrieval
techniques using only IR thresholds for cloud top temperature.
Citation: Thies, B., Nauss, T., and Bendix, J.: Discriminating raining from non-raining clouds at mid-latitudes using meteosat second generation daytime data, Atmos. Chem. Phys., 8, 2341-2349, doi:10.5194/acp-8-2341-2008, 2008.