Ground validation of diurnal TRMM 3B42 V7 and GPM precipitation products over the northeast of Iran

Abstract

Water resources planning and design always deal with precipitation estimation and measurements. In arid and semi-arid climates of developing countries with inadequate numbers of rainfall stations, satellite data become increasingly important. The main objective of this research is to assess the daily rainfall data from the Tropical Rainfall Measurement Mission (TRMM-3B42 V7) and Global Precipitation Measurement (GPM) products with rain-gauge data over a semiarid climate. The study was carried out in Khorasan Razavi Province located in northeast of Iran which is relatively very well equipped with synoptic rainfall stations. Daily rainfall data from 13 stations were collected for a period of 4 years, starting from Feb 2015 to Nov 2018 and compared with the available daily GPM and TRMM-3B42 V7 data. The comparison was performed on daily, monthly, and seasonal timescales. All satellite precipitation products (SPPs) correlated well with measurements from rain-gauge data on the monthly timescale, but moderately on the daily timescale. However, the TRMM data were found slightly better than GPM products. On the seasonal scale, it was found that all SPPs correlated well with measurements from gauges in spring, summer, and winter but in fall, TRMM products outperformed GPM. The GPM products slightly overestimated the data in all of the season except fall, but the TRMM products tended to underestimate the values in all of the seasons except spring. It was found that the TRMM data made a significant improvement in precipitation estimation and could potentially be one of the reliable sources of data for daily-based hydrological modeling in northeast of Iran.