Abstract
Future changes in tropical cyclone (TC) genesis locations and frequency are explored by identifying relationships between TC genesis and dominant daily large-scale patterns, and evaluating the strength of these relationships under a climate change scenario. Self-Organizing Maps (SOMs) are used to characterize the dominant large-scale patterns in reanalysis data and in a regional climate model ensemble simulation of current climate. The main features on the resulting sea level pressure (SLP) SOMs are nodes that resemble both the negative and positive phases of the North Atlantic Oscillation, as well as blocking and ridging regimes. The frequency of the NAO-like nodes is strongly linked to TC genesis frequency and preferred genesis locations. This link is used to develop a statistical relationship between the frequency of large scale SLP patterns and TC genesis. The application of this relationship to an ensemble regional climate simulation under a future climate forcing scenario predicts fewer TCs, which is consistent with the regional climate model that explicitly simulates fewer TCs. This demonstrates the strength of the relationships and their use in assessing future changes in TC genesis locations and frequency.
Highlights
In the climate change debate, tropical cyclones (TCs) receive much attention due to their sensitivity to the global climate and their potential to cause damage. Kunreuther and Michel-Kerjan (2009) and Smith and Katz (2013) indicate that losses due to TCs are currently doubling every 15 years
When comparing the sea surface temperatures (SSTs) anomaly map (Fig. 5a) and TC numbers per node (Fig. 6) with the sea level pressure (SLP) anomaly Self-Organizing Maps (SOMs) feature map (Fig. 4) it is clear that for synoptic conditions where either a strong high or low pressure system is present over the Atlantic Ocean there is a warm SST anomaly in the main development region (MDR: an area located just off the coast of West Africa that is associated with a high level of TC development: Bruy ere et al, 2012)
This paper explored future changes in tropical cyclone (TC) genesis locations and frequency by identifying relationships between TC genesis and dominant daily large-scale patterns, and evaluating the strength of these relationships under a climate change scenario
Summary
In the climate change debate, tropical cyclones (TCs) receive much attention due to their sensitivity to the global climate and their potential to cause damage. Kunreuther and Michel-Kerjan (2009) and Smith and Katz (2013) indicate that losses due to TCs are currently doubling every 15 years. This paper explores how large-scale environmental conditions can be used to un derstand and predict TC genesis with respect to the range of synoptic patterns that occur at the peak of storm season. In this paper the dominant synoptic patterns in the current climate are characterized through a SOM analysis. Research and Forecasting (WRF: Skamarock et al, 2008) regional ensemble simulation of current climate (Bruy ere et al, 2017). This ensemble was designed to create a range of possible synoptic patterns (Prein et al, 2019) and TC responses to these patterns consistent with current climate. Comparison between the statistical prediction of TC genesis and TC genesis explicitly simulated by the regional climate model allows us to understand the strength of the relationships and their utility in assessing potential future changes in TC genesis.
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