Amekudzi, L. K.

Atiah, W. A.

Fink, A. H.

Knippertz, P.

Maranan, M.

Stengel, M.

English

KITopen

EGU21-10649https://doi.org/10.5194/egusphere-egu21-10649EGU General Assembly 2021© Author(s) 2022. This work is distributed underthe Creative Commons Attribution 4.0 License.A Process-Based Validation of GPM IMERG and Its Sources Using aMesoscale Rain Gauge Network in the West African Forest ZoneMarlon Maranan1, Andreas H. Fink1, Peter Knippertz1, Leonard K. Amekudzi2, Winifred A. Atiah2,and Martin Stengel31Karlsruhe Institute of Technology, Karlsruhe, Germany (marlon.maranan@kit.edu)2Kwame Nkrumah University of Science and Technology, Kumasi, Ghana3Deutscher Wetterdienst, Offenbach, GermanyUsing a two-year dataset (2016–17) from 17 one-minute rain gauges located in the moist forestregion of Ghana, the performance of the Integrated Multisatellite Retrievals for GPM, version 6b(IMERG), is evaluated based on a subdaily time scale, down to the level of the underlying passivemicrowave (PMW) and infrared (IR) sources. Additionally, the spaceborne cloud product CloudProperty Dataset Using SEVIRI, edition 2 (CLAAS-2), available every 15 minutes, is used to linkIMERG rainfall to cloud-top properties. Several important issues are identified: 1) IMERG’sproneness to low-intensity false alarms, accounting for more than a fifth of total rainfall; 2)IMERG’s overestimation of the rainfall amount from frequently occurring weak convective events,while that of relatively rare but strong mesoscale convective systems is underestimated, resultingin an error compensation; and 3) a decrease of skill during the little dry season in July and August,known to feature enhanced low-level cloudiness and warm rain. These findings are related to 1) ageneral oversensitivity for clouds with low ice and liquid water path and a particular oversensitivityfor low cloud optical thickness, a problem which is slightly reduced for direct PMW overpasses; 2) apronounced negative bias for high rain intensities, strongest when IR data are included; and 3) alarge fraction of missed events linked with rainfall out of warm clouds, which are inherentlymisinterpreted by IMERG and its sources. This paper emphasizes the potential of validatingspaceborne rainfall products with high-resolution rain gauges on a subdaily time scale, particularlyfor the understudied West African region.Powered by TCPDF (www.tcpdf.org)

A process-based validation of GPM IMERG and its sources using a mesoscale rain gauge network in the West African forest zone

https://publikationen.bibliothek.kit.edu/1000142016/141035690

A process-based validation of GPM IMERG and its sources using a mesoscale rain gauge network in the West African forest zone

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