Tuesday, January 8, 2013

New paper finds global warming weakens tropical cyclones and steers them away from landfall


The impact of anthropogenic climate change on North Atlantic tropical cyclone tracks

Angela J. Colbert1
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL
Brian J. Soden
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL
Gabriel A. Vecchi
NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, NJ
Ben P. Kirtman
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL

Abstract
We examine the change in tropical cyclone (TC) tracks that result from projected changes in the large-scale steering flow and genesis location due to increasing greenhouse gases. Tracks are first simulated using a Beta and Advection Model (BAM) and NCEP-NCAR Reanalysis winds for all TCs that formed in the North Atlantic main development region (MDR) for the period 1950-2010. Changes in genesis location and large-scale steering flow are then estimated from an ensemble mean of 17 CMIP3 models for the A1b emissions scenario. The BAM simulations are then repeated with these changes to estimate how the TC tracks would respond to increased greenhouse gases. As the climate warms, the models project a weakening of the subtropical easterlies as well as an eastward shift in genesis location. This results in a statistically significant decrease in straight-moving (westward) storm tracks of 5.5% and an increase in recurving (open ocean) tracks of 5.5%. These track changes decrease TC counts over the Southern Gulf of Mexico and Caribbean by 1-1.5 per decade and increase TC counts over the central Atlantic by 1-1.5 per decade. Changes in the large-scale steering flow account for a vast majority of the projected changes in TC trajectories.

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