1. INTERNATIONAL INSTITUTE FOR GEO-INFORMATION SCIENCE AND EARTH OBSERVATION Ben Maathuis Department of Water Resources ITC-Enschede The Netherlands From Cloud Top Temperature to Rainfall; Blending MSG and TRMM

2. From temperature to rainfall (1)  Use TRMM to calibrate Meteosat Cloud Top Temperature (10.8 micron band) and transform a time series of MSG images into Precipitation.

3.  View TRMM data using Orbit Viewer and select area, export data to lat/long/rainfall intensity table From temperature to rainfall (2) Available from http://tsdis.gsfc.nasa.gov

4.  Import time series of MSG data using the MSG Data Retriever, converted to TOA Temperature From temperature to rainfall (3) Some Key-features:  Based on open source GDAL drivers;  Fully controlled geometry & radiometry, conversions to diff. data formats: DN, radiances, reflectance, temperature;  Diff. user defined output formats and resolutions (interpolation);  Easy date/time range selection and series construction.

5.  Import of tabular TRMM observations, linking the point map and corresponding MSG image using ILWIS  Large number of TRMM rainfall observations From temperature to rainfall (4)

6.  Low correlation due to spatial and temporal offsets when aligning geostationary IR and LEO PMW datasets on a per-pixel basis;  Improvement of correlation by averaging procedure. From temperature to rainfall (5) After: “Validation of an operational global precipitation analysis at short time scales”. By: F. Joseph Turk, et al Marine Meteorology Division, Naval Research Laboratory, Monterey, California 93943

7.  TRMM rainfall pixels are averaged based on MSG–IR temperature class intervals (in classes of 0.5 or 1 degree K) to obtain for a temperature range (e.g. from 180 to 260 Kelvin) for each temperature class the average corresponding rainfall intensity From temperature to rainfall (6)

8.  Develop an improved relationship between averaged rainfall intensity and temperature From temperature to rainfall (7)

9.  Transform temperature time series to rainfall by single statement From temperature to rainfall (8) rain08sept:=maplistapplic(t_2005 09080000_ir_108.mpl, "iff((##)<260,4.3505278e- 005*(exp(2550.0127/(##))),0)") Can also be displayed as animation

10.  Rainfall per time step  Accumulated 24 hour rainfall From temperature to rainfall (9)

11.  TRMM observations can be used for MSG-IR calibration after an averaging procedure but needs better cloud mask and type determination;  For validation synoptic station data has to be used (at appropriate temporal resolution -> tipping bucket);  Low cost ground receiving station and free software sources make such a near real-time system suitable for e.g. National Hydrological Services and Basin Authorities;  Especially suitable for short duration rainfall events, e.g. for flash floods. Conclusion