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| Titel |
Evaluation of rainfall retrievals from SEVIRI reflectances over West Africa using TRMM-PR and CMORPH |
| VerfasserIn |
E. L. A. Wolters, B. J. J. M. Hurk, R. A. Roebeling |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 15, no. 2 ; Nr. 15, no. 2 (2011-02-03), S.437-451 |
| Datensatznummer |
250012637
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| Publikation (Nr.) |
 copernicus.org/hess-15-437-2011.pdf |
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| Zusammenfassung |
| This paper describes the evaluation of the KNMI Cloud Physical
Properties – Precipitation Properties (CPP-PP) algorithm over West
Africa. The algorithm combines condensed water path (CWP), cloud phase
(CPH), cloud particle effective radius (re), and cloud-top
temperature (CTT) retrievals from visible, near-infrared
and thermal infrared observations of the Spinning Enhanced Visible and Infrared Imager (SEVIRI)
onboard the Meteosat Second Generation (MSG) satellites to estimate rain occurrence
frequency and rain rate. For the 2005 and 2006 monsoon seasons, it is investigated whether the CPP-PP
algorithm is capable of retrieving rain occurrence frequency and rain rate over
West Africa with sufficient accuracy, using Tropical Monsoon
Measurement Mission Precipitation Radar (TRMM-PR) as reference.
As a second goal, it is assessed whether SEVIRI is capable of monitoring the seasonal and
daytime evolution of rainfall during the West African monsoon (WAM), using Climate Prediction Center
Morphing Technique (CMORPH) rainfall observations. The SEVIRI-detected rainfall area agrees well with TRMM-PR,
with the areal extent of rainfall by SEVIRI being ~10% larger than from TRMM-PR. The mean
retrieved rain rate from CPP-PP is about 8% higher than from
TRMM-PR. Examination of the TRMM-PR and CPP-PP cumulative frequency distributions
revealed that differences between CPP-PP and TRMM-PR are generally within
+/−10%. Relative to the AMMA rain gauge observations, CPP-PP shows very
good agreement up to 5 mm h−1. However, at higher rain rates
(5–16 mm h−1) CPP-PP overestimates compared to the rain gauges. With
respect to the second goal of this paper, it was shown that both the
accumulated precipitation and the seasonal progression of rainfall throughout
the WAM is in good agreement with CMORPH, although CPP-PP retrieves higher
amounts in the coastal region of West Africa. Using latitudinal Hovmüller
diagrams, a fair correspondence between CPP-PP and CMORPH was found, which is
reflected by high correlation coefficients (~0.7) for both rain rate and
rain occurrence frequency. The daytime cycle of rainfall from CPP-PP shows
distinctly different patterns for three different regions in West Africa
throughout the WAM, with a decrease in dynamical range of rainfall near the
Inter Tropical Convergence Zone (ITCZ). The dynamical range as retrieved from
CPP-PP is larger than that from CMORPH. It is suggested that this results
from both the better spatio-temporal resolution of SEVIRI, as well as from
thermal infrared radiances being partly used by CMORPH, which likely smoothes
the daytime precipitation signal, especially in case of cold anvils from
convective systems. The promising results show that the CPP-PP algorithm,
taking advantage of the high spatio-temporal resolution of SEVIRI, is of
added value for monitoring daytime precipitation patterns in tropical areas. |
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