Distribution and variability of CAPE over the tropical oceans

Convection is frequently observed in the global tropics and is a necessary condition for tropical cyclogenesis. A measure of the conditional instability of the atmosphere, convective available potential energy (CAPE), can be used to assess how conducive the atmosphere is for convection in a given region. As it also depends on the moisture content of the lifted air parcel, higher amounts of CAPE can indicate environments conducive to tropical cyclone (TC) development and intensification. CAPE has been examined within individual TCs and within the tropics using radiosonde observations, but few studies have explored large-scale, long-term trends in CAPE in the tropics.

Due to their consistent temporal and spatial coverage over decadal time scales, global reanalysis datasets offer a means to explore global CAPE patterns, regional variability in CAPE within TC basins, and changes and variations over time that may be related to natural climate oscillations or climate change. This study uses pre-calculated CAPE from the Climate Forecast System Reanalysis (CFSR) and calculated CAPE from the Japanese 55-year Reanalysis (JRA-55) to investigate relationships between CAPE and other environmental variables, such as sea surface temperature and vertical wind shear, indices representing established patterns such as the El Niņo-Southern Oscillation (ENSO) and the Pacific decadal oscillation (PDO), as well as seasonal and multidecadal TC activity. Results describing statistical correlations, dominant spatial patterns, and temporal shifts by basin and from a global perspective using monthly CAPE data will be presented. Relationships between 6-hourly CAPE and periods of TC intensity change will also be discussed.