The figure above displays the annual tropical-cyclone-related percentage of extreme daily precipitation exceeding four inches (>EPD4). The authors found that the proportion of tropical cyclone contributions is higher for more extreme events.
Understanding the frequency and intensity of extreme precipitation events in relation to tropical cyclones is critical to the development of infrastructure in affected areas. Authors Olivier Prat of the Cooperative Institute for Climate and Satellites–North Carolina and Brian Nelson from the National Centers for Environmental Information investigate the relationship between Tropical Cyclones and extreme daily rainfall as defined by precipitation greater than two inches per day and four inches per day. The study concludes with detailed findings on the relative contributions of cyclone-related events to annual precipitation and extreme daily rainfall in the locations observed.
The authors separate areas that experience tropical cyclone activity into five domains: North and Central America, Southeast and East Asia, South and West Asia, Oceania, and East Africa. In the chosen regions, all precipitation related to cyclonic activity, observed via satellite from 1998 to 2012, is considered regardless of whether the system itself underwent landfall. Any precipitation occurring within a 500-kilometer radius of a tropical cyclone’s center point is considered related rainfall. To determine the position of this center point, Prat and Nelson use data from the IBTrACS database (International Best Track Archive for Climate Stewardship).
Among their findings, Prat and Nelson discover that the proportion of extreme events pertaining to tropical cyclones increases as the threshold is raised from 1 inch per day to 4 inches per day, indicating that more severe precipitation events are more likely to be the result of tropical cyclones. Between all five areas considered in their study over the fifteen-year period, cyclones were involved with 13% to 31% of daily precipitation events greater than four inches a day. In certain local areas, however, tropical cyclones are known to contribute to more than 70% and up to nearly 100% of all days involving greater than four inches of precipitation. The authors additionally found that extreme, tropical cyclone-related rainfall is more common later in the season, after the regional peak of cyclonic activity—a phenomena which is potentially reflective of rising sea surface temperatures over the domain late-summer and early fall season.
Prat, O. P., and B. R. Nelson, 2016: On the Link between Tropical Cyclones and Daily Rainfall Extremes Derived from Global Satellite Observations. Journal of Climate, 29, 6127-6135. http://dx.doi.org/10.1175/JCLI-D-16-0289.1