Interannual to Multidecadal variability of vertical shear in the tropics: Relationship with tropical cyclone activity

Vertical shear is a key environmental variable that limits the genesis of tropical cyclones. In this study, we examine the interannual and multidecadal variability of vertical shear within the tropics. Using the dominant empirical orthogonal functions (EOFs) of vertical shear, we extract the spatio-temporal structures that vary on these respective time scales. The corresponding upper- and lower-level circulations are examined and related to forcing by SST and convection. The patterns of tropical cyclone genesis and tracks within the Atlantic and Pacific basins are also examined in relation to the modes of variability of the vertical shear.

The data employed in this study is taken from the NCAR/NCEP reanalysis, Hadley Center SSTs and the GPCP precipitation dataset. Additional analysis of the multidecadal variability is performed using the output of a GCM simulation covering 128 years.