Reliability of GPM IMERG Satellite Precipitation Data for Modelling Flash Flood Events in Selected Watersheds in the UAE

Abstract

Arid regions are prone to unprecedented extreme rainfall events that often result in severe flash floods. Using near-real-time precipitation data in hydrological modelling can aid in flood preparedness. This study analyzed rainfall data obtained from Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG V. 06) since 2001 to highlight recent trends of extreme rainfall indices for three selected watersheds in the UAE. Additionally, to validate the trends, the present study incorporated CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) into the analysis. Furthermore, for the first time, this study assessed the performance of the three products of IMERG in modelling flash flood events in the selected watersheds of UAE. A physical-based, fully distributed model was used to simulate the heaviest storm event. Also, a sensitivity analysis of the model’s output to variations in the input parameters was conducted using the one-factor-at-a-time method. The result of the trend analysis indicated that IMERG and CHIRPS show similar trends in both datasets, indicating agreement and reliability in their observations. However, there are a few instances where IMERG and CHIRPS show slight discrepancies in the nature of the trend. In general, the trend analysis results indicated an increasing trend of total precipitation (mm) and consecutive wet days, which suggests a rise in the risk of flash floods. The simulation of the flash flood event showed that the IMERG final product outperformed the other two products, closely matching the model output of the gauge rainfall data with mean absolute error (MAE) of 1.5, 2.37, and 0.5 for Wadi Ham, Wadi Taween, and Wadi Maidaq, respectively. The model’s performance was positively correlated with the size of the watershed. The sensitivity analysis results demonstrated that the model’s output was most sensitive to infiltration parameters. The study’s outcomes provide a good opportunity to improve near-real-time impact evaluation of flash flood events in the watersheds of the UAE.

Flash Flood Risk Assessment in the Asir Region, Southwestern Saudi Arabia, Using a Physically-Based Distributed Hydrological Model and GPM IMERG Satellite Rainfall Data

“…Despite these limitations, the study employed a well-established, physically-based, fully distributed model, and achieved satisfactory results. In addition, this model has been successfully implemented by other researchers, achieving satisfactory results (e.g., Hamouda et al [11]). While the derived results provide a valuable initial assessment, further refinement is certainly achievable.…”

“…The IMERG output has a spatial resolution of 0.1 • × 0.1 • and temporal resolution of 30 min. For more details about the IMERG products, we refer the readers to Hamouda et al [11] and Mahmoud et al [24]. A simplified flowchart of our data and used methodology is shown in Figure 4.…”

“…The data also have three products, namely, "IMERG Early", "IMERG Late", and "IMERG Final". For more information about the IMERG products, readers can refer to Hamouda et al [11]. Figures 10 and 11 show the IMERG Early, Late, and Final half-hourly products for most regions of Saudi Arabia and for the Wadi Hail catchment, respectively.…”