Comparison of GPM-IMERG and TRMM 3B43 precipitation products with dense network of rain-gauges for the Northeast monsoon season over Tamil Nadu, India

Abstract:

Assessing the reliability of precipitation product is very important before using instead of ground-based observations for their applications. In this study, the comparison between four satellite precipitation products namely, the newly-released Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG) Final Run product and Tropical Rainfall Measuring Mission (TMPA) daily product (or 3B42) at monthly and seasonal pattern over Tamil Nadu during North-East Monsoon (NEM) season of OND (October, November, and December) for the period from 2015 – 2017. The ground precipitations used for validation were collected from Tamil Nadu Agricultural Weather Network (TAWN) established by Tamil Nadu Agricultural University (TNAU) in Tamil Nadu. Five evaluation indices: Pearson’s Correlation Coefficient (CC), Root Mean Square Error (RMSE) and mean error (ME), mean absolute error (MAE) and percent of the bias (PB) were used to evaluate the performance of products with gauge measurements. The results show that IMERG and TRMM 3B42 rainfall products with rain gauge have a good agreement (CC > 0.6) for all time stages. GPM showed a greater CC (> 0.96) at a monthly time scale. During 2015, TRMM performance is relatively good because minimum mean error (ME = 12.12 mm). The RMSE and MAE, which evaluates the average magnitude error between satellite estimates and ground stations showed the same trend. The negative and positive value of PB confirms that most products overestimated rainfall during all months, except TRMM 3B42 in December 2015. The seasonal precipitation indicates a decreasing trend from east to west, which is consistent in GPM-IMERG and TRMM 3B42 satellite-based precipitation products performed better on a monthly scale than in seasonal scale. The study concluded that both dataset can be a useful substitute for rain-gauge precipitation data.

Keywords: Satellite precipitation; GPM-IMERG; TRMM; Northeast monsoon; Comparison