Abstract/Summary

As the climate warms, sea surface temperature (SST) is projected to increase, along with atmospheric variables which may have an impact on tropical cyclone (TC) properties. Climate models have well-known errors in simulating current climate SSTs that will likely affect future TC projections. Therefore, a better understanding of the impact of SST changes will help us identify the largest uncertainty in projecting TC changes. The focus of the study is the Philippines where TCs have a significant annual impact. Using the Weather Research and Forecasting model, a set of experiments were carried out for three observed TCs, Typhoons Haiyan, Bopha, and Mangkhut at a resolution of 5km using ERA5 boundary conditions. Experiments were performed using ERA5 SSTs in control experiments without any changes; then with an imposed uniform SST adjustment of between -4 to +4°C; and finally with a monthly mean SST change derived from a CMIP6 model. Additional experiments with changes in temperature profile were also performed where each of the SST and atmosphere experiments were run in isolation from each other. Changes in SSTs resulted in changes in TC track, intensity, and rainfall. In the positive SST simulations, TCs tended to move northwards and resulted in substantial increases in maximum wind speeds reaching a difference of up to 10, 13, 23 ms-1 for Typhoons Haiyan, Bopha, and Mangkhut, respectively. Analysis of the accumulated rainfall also showed that increased SST results in increased rainfall. Inclusion of atmospheric warming offsets the intensification due to SST change. Moreover, warmer SSTs resulted in slower-moving TCs and increased TC size.