An IMERG based Assessment of the Contribution of Landfalling Tropical Cyclones to Rainfall Climatology in the US Atlantic Basin

Abstract:

Multiple hurricanes make landfall each year in the United States. While the wind damage from hurricanes is the first concern, there is growing need to understand the risk due to rain and associated flooding. Hurricanes affect the coastal regions with copious amount of rain before, during and post-landfall. These rains can impact a region in several ways including: (i) affecting the rainfall climatology, (ii) creating hydrometeorological probabilities for ‘drought-bust’, (iii) recharging groundwater at some locations, and (iv) impacting the flood frequency and associated risk. It is therefore important to characterize and quantify the role of these extreme events over a geographic or climatic region. This study evaluates the recently available gridded GPM IMERG (NASA’s Global Precipitation Mission- Integrated multi-sensor retrievals for GPM Rainfall Product) rainfall datasets, and the Atlantic HURDAT2 data to assess the timing and track of hurricanes (2000 onward) and develop a synthesis related to rainfall occurrence. The precipitation observed from land-falling hurricane in the relatively high-resolution (10 km) merged rainfall product, GPM IMERG for the landfall location and several locations along the hurricane track in the US Gulf and the Atlantic coast, is analyzed. The NCEI and PRISM 30-year normal rainfall is used to represent the climatology and represent the TC-based rainfall relative to the rainfall climatology of the climate divisions. Results for Hurricane Florence (2018) show that the IMERG observed rainfall accumulation was 169 % above the 30-year normal daily precipitation value for the same period. The TC based rainfall was 64 % above than the monthly (September) normal precipitation value and is 8.7 % of the normal annual precipitation value. Similarly, for hurricane Matthew the IMERG rainfall is 12.45% of the annual rainfall climatology. The study findings provide an assessment for using IMERG data into hurricane rainfall climatology framework.