Search for: All records

Abstract High temporal and spatial resolution precipitation datasets are essential for hydrological and flood modeling to assist water resource management and emergency responses, particularly for small watersheds, such as those in Hawai‘i in the United States. Unfortunately, fine temporal (subdaily) and spatial (<1 km) resolutions of rainfall datasets are not always readily available for applications. Radar provides indirect measurements of the rain rate over a large spatial extent with a reasonable temporal resolution, while rain gauges provide “ground truth.” There are potential advantages to combining the two, which have not been fully explored in tropical islands. In this study, we applied kriging with external drift (KED) to integrate hourly gauge and radar rainfall into a 250 m × 250 m gridded dataset for the tropical island of O‘ahu. The results were validated with leave-one-out cross validation for 18 severe storm events, including five different storm types (e.g., tropical cyclone, cold front, upper-level trough, kona low, and a mix of upper-level trough and kona low), and different rainfall structures (e.g., stratiform and convective). KED-merged rainfall estimates outperformed both the radar-only and gauge-only datasets by 1) reducing the error from radar rainfall and 2) improving the underestimation issues from gauge rainfall, especially during convective rainfall. We confirmed the KED method can be used to merge radar with gauge data to generate reliable rainfall estimates, particularly for storm events, on mountainous tropical islands. In addition, KED rainfall estimates were consistently more accurate in depicting spatial distribution and maximum rainfall value within various storm types and rainfall structures. Significance StatementThe results of this study show the effectiveness of utilizing kriging with external drift (KED) in merging gauge and radar rainfall data to produce highly accurate, reliable rainfall estimates in mountainous tropical regions, such as O‘ahu. The validated KED dataset, with its high temporal and spatial resolutions, offers a valuable resource for various types of rainfall-related research, particularly for extreme weather response and rainfall intensity analyses in Hawai’i. Our findings improve the accuracy of rainfall estimates and contribute to a deeper understanding of the performance of various rainfall estimation methods under different storm types and rainfall structures in a mountainous tropical setting. 

Abstract With increasing needs for understanding historic climatic events and assessing changes in extreme weather to support natural hazard planning and infrastructure design, it is vital to have an accurate long-term hourly rainfall dataset. In Hawaiʻi, annual, monthly, and daily gauge data have been well-compiled and are accessible. Here, we compiled hourly rainfall data from both gauges and radars. We arranged the metadata from various data sources, acquired data, and applied quality control to each gauge dataset. In addition, we compiled and provided hourly radar rainfall, and filtered out areas with low confidence (larger error). This paper provides (1) a summary of available hourly data from various observation networks, (2) 293-gauge rainfall data from their installation date to the end of 2020, and (3) a 5-year 0.005° by 0.005° (~250 × 250 m²) gridded radar rainfall dataset between 2016 and 2020 across the Hawaiian Islands.