Parameterizing Sea Surface Temperature Cooling Induced by Tropical Cyclones: 2. Verification by Ocean Drifters

Abstract

This study analyzes sea surface responses to tropical cyclones (TCs), based on sea surface temperature (SST) and ocean surface current (V OS ) data from 57 buoy drifters, together with satellite SST and sea surface height anomaly data, associated with nine TCs during the year of 2016 in order to validate the TC-induced SST cooling (SSTC) parameterization scheme developed in Part 1. Results show that the drifters-measured SSTs compare favorably to the satellite detected, except near the coastline and at high latitudes, and that SSTCs are negatively correlated with sea surface height anomaly. During TC passage, V OS usually rotate clockwise on the right-hand side of TC tracks, but their rotating directions cannot be specified on their left-hand side. After TC passage, most drifters, located on both sides, show clockwise rotation. These results help characterize the responses of SST and V OS to TCs into the following three modes: (i) significant increases in V OS during TC passage, followed by strong SSTC; (ii) decreases or little changes in V OS , followed by SSTC; and (iii) little changes in both V OS and SSTC. All the three response modes are reasonably included in the SSTC parameterization scheme. After optimizing three empirical constants, based on the drifters' data, the scheme's performance is evaluated by comparing the parameterized SSTC to the drifters-measured SSTs, showing satisfactory results in terms of the starting time, duration, strength, and rate of SSTCs. An error analysis shows a mean value of about 20% of the observed SSTC with a small standard deviation, confirming the effectiveness of the SSTC parameterization scheme.