Journal of Climate 2013 ; e-View
Atlantic Hurricanes and Climate Change. Part II: Role of Thermodynamic Changes in Decreased Hurricane Frequency
Megan S. Mallard,1 Gary M. Lackmann, and Anantha Aiyyer
An ensemble of high-resolution simulations project reductions in ensemble-average TC [tropical cyclone] counts between 18 and 24%, consistent with previous studies. Robust decreases in TC and hurricane counts are simulated with 18- and 6-km grid lengths, for both active and inactive periods. Physical processes responsible for reduced activity are examined through comparison of monthly- and spatially-averaged genesis-relevant parameters, as well as case studies of development of corresponding initial disturbances in current and future thermodynamic conditions. These case studies show that reductions in TC counts are due to the presence of incipient disturbances in marginal moisture environments, where increases in the moist entropy saturation deficits in future conditions preclude genesis for some disturbances. Increased convective inhibition and reduced vertical velocity are also found in the future environment. It is concluded that a robust decrease in TC frequency can result from thermodynamic changes alone, without modification of vertical wind shear or the number of incipient disturbances.