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Evaluation and application of SEVIRI rainfall retrievals over West Africa

Evaluation and application of SEVIRI rainfall retrievals over West Africa. Erwin Wolters 1 Bart van den Hurk 1,2 Rob Roebeling 1. 1: Royal Netherlands Meteorological Institute (KNMI), de Bilt, Netherlands 2: Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht, Netherlands.

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Evaluation and application of SEVIRI rainfall retrievals over West Africa

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  1. Evaluation and application of SEVIRIrainfall retrievals over West Africa Erwin Wolters1 Bart van den Hurk1,2 Rob Roebeling1 1: Royal Netherlands Meteorological Institute (KNMI), de Bilt, Netherlands 2: Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht, Netherlands

  2. Motivation Precipitation of great importance to hydrological cycle Precipitation observations are sparse over West Africa SEVIRI precipitation algorithm daytime only multispectral physically based high spatial/temporal resolution

  3. CPP Precipitation Properties algorithm SEVIRI R0.6, R1.6 =f(R0.6 μm) ΔH=f(CTT) re=f(R1.6 μm) CWP=f(,re) PRP=f(CWP,ΔH)

  4. Evaluation: comparison with CMORPH Seasonal evolution (2005) over West Africa Diurnal cycle during daytime (7:30 – 16:30)

  5. Seasonal cycle 2005 Rainrate CPP-PP CMORPH coastline

  6. Latitudinal cross section May Jul Sep 2005 2006

  7. Daytime cycle June Semi-arid savannah Rain forest

  8. Soil moisture-precipitation interaction • Is rain occurrence and intensity different over wet and dry soils? • -Focus on May (pre-monsoon) and Sep (post-monsoon) • -No rain at 7:30 UTC to avoid nighttime MCS remnants • -Anomalies of previous-day AMSR-E soil moisture (thanks to Richard de Jeu, Free University of Amsterdam)

  9. Methodology SEVIRI precipitation class “dry” class “wet” Normalized soil moisture AMSR-E Soil moisture anomalies

  10. Results May and Sep 2005 Rain rate [mm h-1] Rain occurrence [%]

  11. Conclusions/outlook CPP in good agreement with CMORPH (and TRMM) Applicable at various time scales (seasonal, daytime cycle) Unprecedented temporal resolution To be extended with nighttime scheme using WV and IR channels

  12. Thank you!

  13. CPP-PP retrieval algorithm 1) Based on Wentz and Spencer (1998) (Parameterization developed for SSM/I) 2) Roebeling and Holleman (2009) (Parameterization modified for SEVIRI) CWP : Condensed Water Path [g m-2]R : Rain Rate [mm h-1] H : Thickness of precipitating column [km] CTT : Cloud Top Temperature [K] dH : Offset thickness rain column [km]

  14. CPP-PP retrieval algorithm SEVIRI Cloud TopTemperature [K] Cloud Phase Thickness liquid column Particle size Condensed Water Path re (water) > 16 m Precipitation Algorithm CWP > 150 g m-2 Output Rain Rate (RR) [mm h-1]

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