Abstract
This paper evaluates Integrated Multi-Satellite Retrievals from GPM (IMERG-F) over Europe for the period 2014–2018 in order to evaluate application of the retrievals to hydrology. IMERG-F is compared with a large pan-European precipitation dataset built on rain gauge stations, i.e., the ENSEMBLES OBServation (E-OBS) gridded dataset. Although there is overall agreement in the spatial distribution of mean precipitation (R2 = 0.8), important discrepancies are revealed in mountainous regions, specifically the Alps, Pyrenees, west coast of the British Isles, Scandinavia, the Iberian and Italian peninsulas, and the Adriatic coastline. The results show that the strongest contributors to poor performance are pixels where IMERG-F has no gauges available for adjustment. If rain gauges are available, IMERG-F yields results similar to those of the surface observations, although the performance varies by region. However, even accounting for gauge adjustment, IMERG-F systematically underestimates precipitation in the Alps and Scandinavian mountains. Conversely, IMERG-F overestimates precipitation in the British Isles, Italian Peninsula, Adriatic coastline, and eastern European plains. Additionally, the research shows that gauge adjustment worsens the spatial gradient of precipitation because of the coarse resolution of Global Precipitation Climatology Centre data.
Highlights
Accurate estimation of precipitation is essential in weather prediction, climate change research, and hydrologic applications [1,2,3]
The first visible/IR (Infrared Radiation) sensors were soon complemented with passive microwave (PMW) instruments, because electromagnetic radiation at microwave frequencies is affected by precipitation-sized particles but not by cloud droplets [15]
This paper evaluates how Integrated Multi SatellitE Retrievals from GPM (IMERG) compares with gauge-derived, high-resolution precipitation products used in climatological research
Summary
Accurate estimation of precipitation is essential in weather prediction, climate change research, and hydrologic applications [1,2,3]. There are three main methods to measure precipitation, rain gauges, weather radars and satellite sensors. In spite of being considered the standard of precipitation measurement, rain gauges are subject to many uncertainties They provide point estimates that may be not fully representative of an area, especially large and complex ones with few stations [6]. The first visible/IR (Infrared Radiation) sensors were soon complemented with passive microwave (PMW) instruments, because electromagnetic radiation at microwave frequencies is affected by precipitation-sized particles but not by cloud droplets [15] These instruments are prone to problems such as limited temporal sampling (which can be alleviated using a constellation) and inherent limitations over land (because soil emissivity masks the rainfall signal) [16].
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