1. Evaluation and application of SEVIRI rainfall 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
EGU General Assembly, 6 April 2011

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)
EGU General Assembly, 6 April 2011

4. Evaluation: comparison with CMORPH
Seasonal evolution (2005) over West Africa
Diurnal cycle during daytime (7:30 – 16:30)
EGU General Assembly, 6 April 2011

5. Seasonal cycle 2005 Rain rate CPP-PP CMORPH coastline
EGU General Assembly, 6 April 2011

6. Latitudinal cross section
May
Jul
Sep
2005
2006
EGU General Assembly, 6 April 2011

7. Daytime cycle June Semi-arid savannah Rain forest
EGU General Assembly, 6 April 2011

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)
EGU General Assembly, 6 April 2011

9. Methodology SEVIRI precipitation class “dry” class “wet”
Normalized soil moisture
AMSR-E
Soil moisture anomalies
EGU General Assembly, 6 April 2011

10. Results May and Sep 2005 Rain occurrence [%] Rain rate [mm h-1]
EGU General Assembly, 6 April 2011

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
EGU General Assembly, 6 April 2011

12. Thank you!
EGU General Assembly, 6 April 2011

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]
EGU General Assembly, 6 April 2011

14. CPP-PP retrieval algorithm
SEVIRI
Cloud Phase
Cloud Top Temperature
[K]
Condensed Water Path
Particle size
Thickness liquid column
re (water) > 16 m
Precipitation Algorithm
CWP > 150 g m-2
Output
Rain Rate (RR)
[mm h-1]
EGU General Assembly, 6 April 2011