H217-06
Evaluation of the GPM IMERG-Late precipitation product and its constituents over the Netherlands

Wednesday, 16 December 2020: 20:50
Virtual
Linda Bogerd1,2, Aart Overeem1,2, Hidde Leijnse2 and Remko Uijlenhoet1, (1)Wageningen University and Research, Hydrology and Quantitative Water Management Group, Wageningen, Netherlands, (2)Royal Netherlands Meteorological Institute, De Bilt, Netherlands
Recorded Presentation
Abstract:
Satellite observations can provide global, uniformly distributed and near real-time precipitation estimates. It is crucial that the uncertainty associated with these satellite estimates is well understood for them to be applicable in hydrology and meteorology. This study aims to evaluate the performance of the IMERG-Late V06 precipitation product over the Netherlands between 2015 and 2019.

The Netherlands is chosen as the research area since it has 1) a flat topography, 2) an excellent infrastructure with both in-situ and remotely sensed ground-based precipitation measurements, and 3) frequent occurrences of shallow precipitation events, one of the remaining challenges for satellite-based remote sensing. Because this study aims to assess the performance of satellite-based precipitation estimates, it was decided to focus on the IMERG-Late rather than the (elaboratively studied) Final product. Precipitation estimations from a gauge-adjusted weather radar dataset are used as reference.

Both the seasonal performance of IMERG and the effect of rainfall intensity are studied to provide preliminary insight into which precipitation type (which is strongly seasonally dependent in the study area) is hardest to detect and measure from space. The discrepancies between IMERG and the ground-based measurements are unraveled by evaluating the underlying sources contributing to the IMERG product (i.e. by separating between observations which use direct PMW observations, morphed or PMW/IR-based observations).

Timeseries show that, although IMERG-Late correctly captures the yearly cycle, it consistently overestimates the rainfall depths compared to the gauge-adjusted radar. While overestimation occurs in all seasons, it is especially pronounced in winter and spring. In the five studied years IMERG consistently shows the best performance in fall. The largest overestimations seem to occur when direct PMW observations are used in the IMERG product.

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