Assessing the influence of large-scale environmental conditions on rainfall structure of Atlantic tropical cyclones: An observational study

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  • 1 School of Earth and Environmental Sciences, Seoul National University, Seoul, Korea
  • 2 NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, NJ 08540, USA
  • 3 Department of Earth Science Education, Kyungpook National University, Daegu, Korea
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Abstract

Understanding the mechanisms related to the variations in the rainfall structure of tropical cyclones (TCs) is crucial in improving forecasting systems of TC rainfall and its impact. Using satellite precipitation and reanalysis data, we examined the influence of along-track large-scale environmental conditions on inner-core rainfall strength (RS) and total rainfall area (RA) for Atlantic TCs during the TC season (July to November) from 1998 to 2019. Factor analysis revealed three major factors associated with variations in RS and RA: large-scale low- and high-pressure systems (F1), environmental flows, sea surface temperature, and humidity (F2), and maximum wind speed of TCs (F3). Results from our study indicate that RS increases with an increase in the inherent primary circulation of TCs (i.e., F3), but is less affected by large-scale environmental conditions (i.e., F1 and F2), whereas RA is primarily influenced by large-scale low- and high-pressure systems (i.e., F1) over the entire North Atlantic and partially influenced by environmental flows, sea surface temperature, humidity, and maximum wind speed (i.e., F2 and F3). A multi-variable regression model based on the three factors accounted for the variations of RS and RA across the entire basin. In addition, regional distributions of mean RS and RA from the model significantly resembled those from observations. Therefore, our study suggests that large-scale environmental conditions over the North Atlantic are important predictors for TC rainfall forecasts, particularly regarding RA.

Corresponding author: Chang-Hoi Ho (hoch@cpl.snu.ac.kr)

Abstract

Understanding the mechanisms related to the variations in the rainfall structure of tropical cyclones (TCs) is crucial in improving forecasting systems of TC rainfall and its impact. Using satellite precipitation and reanalysis data, we examined the influence of along-track large-scale environmental conditions on inner-core rainfall strength (RS) and total rainfall area (RA) for Atlantic TCs during the TC season (July to November) from 1998 to 2019. Factor analysis revealed three major factors associated with variations in RS and RA: large-scale low- and high-pressure systems (F1), environmental flows, sea surface temperature, and humidity (F2), and maximum wind speed of TCs (F3). Results from our study indicate that RS increases with an increase in the inherent primary circulation of TCs (i.e., F3), but is less affected by large-scale environmental conditions (i.e., F1 and F2), whereas RA is primarily influenced by large-scale low- and high-pressure systems (i.e., F1) over the entire North Atlantic and partially influenced by environmental flows, sea surface temperature, humidity, and maximum wind speed (i.e., F2 and F3). A multi-variable regression model based on the three factors accounted for the variations of RS and RA across the entire basin. In addition, regional distributions of mean RS and RA from the model significantly resembled those from observations. Therefore, our study suggests that large-scale environmental conditions over the North Atlantic are important predictors for TC rainfall forecasts, particularly regarding RA.

Corresponding author: Chang-Hoi Ho (hoch@cpl.snu.ac.kr)
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