Abstract
The new generation of weather observatory satellites, namely Global Precipitation Measurement (GPM) constellation satellites, is the lead observatory of the 10 highly advanced earth orbiting weather research satellites. Indeed, GPM is the first satellite that has been designed to measure light rain and snowfall, in addition to heavy tropical rainfall. This work compares the final run of the Integrated Multi-satellitE Retrievals for GPM (IMERG) product, the post real time of TRMM and Multi-satellite Precipitation Analysis (TMPA-3B42) and the Era-Interim product from the European Centre for Medium Range Weather Forecasts (ECMWF) against the Iran Meteorological Organization (IMO) daily precipitation measured by the synoptic rain-gauges over four regions with different topography and climate conditions in Iran. Assessment is implemented for a one-year period from March 2014 to February 2015. Overall, in daily scale the results reveal that all three products lead to underestimation but IMERG performs better than other products and underestimates precipitation slightly in all four regions. Based on monthly and seasonal scale, in Guilan all products, in Bushehr and Kermanshah ERA-Interim and in Tehran IMERG and ERA-Interim tend to underestimate. The correlation coefficient between IMERG and the rain-gauge data in daily scale is far superior to that of Era-Interim and TMPA-3B42. On the basis of daily timescale of bias in comparison with the ground data, the IMERG product far outperforms ERA-Interim and 3B42 products. According to the categorical verification technique in this study, IMERG yields better results for detection of precipitation events on the basis of Probability of Detection (POD), Critical Success Index (CSI) and False Alarm Ratio (FAR) in those areas with stratiform and orographic precipitation, such as Tehran and Kermanshah, compared with other satellite/model data sets. In particular, for heavy precipitation (>15 mm/day), IMERG is superior to the other products in all study areas and could be used in future for meteorological and hydrological models, etc.
Highlights
Water is fundamental to life on Earth
In daily scale the results reveal that all three products lead to underestimation but Integrated Multi-satellitE Retrievals for GPM (IMERG) performs better than other products and underestimates precipitation slightly in all four regions
An evaluation of the two recent post real time satellite datasets (IMERG and 3B42) and a common precipitation forecast model dataset (ERA-Interim) in daily, monthly and seasonal scales against rain-gauges for four different topography and climate conditions in Iran from mid-March 2014 to February 2015 shows that IMERG, 3B42 and ERA-Interim lead to underestimation over Iran
Summary
Water is fundamental to life on Earth. Knowing the locations and extents of rain and snowfall is vital to understanding how weather and climate impact our environment and Earth’s water and energy cycles, including effects on agriculture, fresh water availability, and response to natural disasters. Evaluation of satellite precipitation estimates is essential prior to operational use. This is why many previous studies are devoted to the validation of satellite estimation [1,2,3]. The primary requirement in precipitation measurement is to know where and how much precipitation is falling at any given time. Such precipitation characteristics may be determined through traditional ground-based rain-gauges and/or advanced satellite precipitation products. Another important aspect deals with the duration of precipitation. Accumulation products have been evaluated daily (derived from accumulation of half-hourly and 3-hourly basis for IMERG, TMPA-3B42 respectively), monthly and seasonally as well
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