INTERNATIONAL INSTITUTE FOR GEO-INFORMATION SCIENCE AND EARTH OBSERVATION

Ben MaathuisDepartment of Water

ResourcesITC-Enschede

The Netherlands

From Cloud Top Temperature to Rainfall; Blending MSG and TRMM

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.

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

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.

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)

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

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)

Develop an improved relationship between averaged rainfall intensity and temperature

From temperature to rainfall (7)

Transform temperature time series to rainfall by single statement

From temperature to rainfall (8)

rain08sept:=maplistapplic(t_200509080000_ir_108.mpl, "iff((##)<260,4.3505278e-005*(exp(2550.0127/(##))),0)")

Can also be displayed as animation

Rainfall per time step Accumulated 24 hour rainfall

From temperature to rainfall (9)

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