Variations in Pacific Tropical Cyclone Sizes and Precipitation in a GCM

Observations have shown that tropical cyclone (TC) size varies across the North Pacific, with larger and more variable sizes common in the western part of the basin. These size variations are correlated with relative sea surface temperatures (RSST), with the largest storms found where RSST is highest. This project examines TC sizes and their associated precipitation within a global climate model that covers a 25-year period from 1980 to 2005. A filter was applied to the output of a vortex tracking algorithm to isolate the storms that occurred in the North Pacific Ocean during the months of May to November each year. A climatology was created of both sea surface temperature and RSST, to compare how the mean size of 5 m·s^-1 azimuthal wind speed (r₅) varies with respect to variables such as RSST and maximum intensity. We find that storm size varies from west to east in the model as it does in nature, and the relationship with RSST is similar. Storms in the western North Pacific are larger and more variable, but there is less variability in the sizes of the initial vortices. We also find that storms increase in size with latitude within the tropics. An average of the maximum precipitation rate for the duration of each storm is also examined. A strong association of the highest precipitation rates with the highest SST values was found across the North Pacific Ocean.