How well do high-resolution Global Climate Models (GCMs) simulate tropical cyclones in the Bay of Bengal?

Abstract

Using six HighResMIP multi-ensemble GCMs (both the atmosphere-only and coupled versions) at 25 km resolution, the Tropical Cyclone (TC) activity over the Bay of Bengal (BoB) is examined in the present (1950–2014) climate. We use the Genesis Potential Index (GPI) to study the large-scale environmental conditions associated with the TC frequency in the models. Although the models struggle to reproduce the observed frequency and intensity of TCs, most models can capture the bimodal characteristics of the seasonal cycle of cyclones over the BoB (with fewer TCs during the pre-monsoon [April–May] than the post-monsoon [October–November] season). We find that GPI can capture the seasonal variation of the TC frequency over the BoB in both the observations and models. After calibrating the maximum sustained windspeeds in the models with IBTrACS, we find that like the observations the proportion of strong cyclones is also higher in the pre-monsoon than the post-monsoon. However, the inter-seasonal contrast of the proportion of strong cyclones between the pre-monsoon and post-monsoon seasons is reduced in almost all the models compared to the observations. The windshear term in GPI contributes the most to the model biases in all models during the post-monsoon season. This bias is caused by weakening of upper-level (200 hPa) easterlies in analysed models. During the pre-monsoon season, the environmental term in GPI dominating the model biases varies from model to model. When comparing the atmosphere-only and coupled versions of the models, a reduction of 0.5 °C in the sea surface temperature (SST) and a lowering of TC frequency occur in almost all the coupled models compared to their atmosphere-only counterparts.

Projected near-future changes in precipitation extremes over Anambra-Imo River Basin inferred from CMIP6 HighResMIP

“…The HighResMIP project attempts to enhance our grasp of climate anomalies through the simulation of more precise and reliable projections [14]. Given the incorporation of more detailed topography, land surface processes, and atmospheric dynamics in these models and their high-resolution structure, it presents a special tool for the prediction of regional-scale extreme precipitation events [11,15].…”

“…Several studies have reported the creditable performance of HighResMIP models in simulating mean precipitation and precipitation extremes in different regions across the world [15][16][17][18][19].However, understanding the potential near-future changes in precipitation extremes will provide the crucial insight required to assist policymakers in establishing essential regulations that will forestall the impact of climate change and its implications on the population [8]. Recent studies have examined the impact of climate change on precipitation extremes in Nigeria [20][21][22][23].…”

Investigation of the Development of Tropical Storm Nicholas based on Global and Regional Climate Data

“…While on land, strong winds are fatal and can destroy buildings, vehicles, as well as other places and objects in their path (Sobel et al, 2021). In addition, tropical cyclones also cause storm surges or sea level rises, such as high tides that come suddenly and are dangerous when they reach land (Akhter et al, 2023).…”