Dropsonde-Derived Moist Static Energy Variability in Atlantic Hurricanes

Interactions between clouds, water vapor, radiation, and mesoscale circulations represent important feedbacks on tropical cyclone (TC) development, such as cloud longwave radiative effects. Understanding and quantifying these interactions requires knowing how moist static energy (MSE) and its column-integral (CMSE) vary spatially around the TC (Wing and Emanuel 2014). Dropsondes from aircraft reconnaissance can directly sample MSE, providing a useful observational tool to address this question. Though dropsondes are limited in number and spatial coverage, recent modeling work suggests that they can faithfully resolve a TC’s radial MSE and CMSE variability. Therefore, this study uses upper-level reconnaissance dropsonde data from North Atlantic TCs spanning from the late 1990s until present to evaluate the spatial variability of MSE and CMSE around TCs. The database contains thousands of dropsondes that sample TCs of different intensity, structure, size, and geographic location across the North Atlantic, which facilitates testing the sensitivity of MSE and CMSE variability to these properties. Ultimately, the objective of this work is to generate a TC-centric climatology of MSE, which is important for understanding TC development.

Despite differences in location, TC intensity, and flight pattern including inner and outer radial coverage, MSE profiles have so far been found to have notably similar structures across TCs. CMSE decreases with distance from the TC center due to the amplified warmth and moisture in the inner core. This decrease is sharper near the inner core, then more gradual at outer radii. The radius-azimuth-height structure of MSE is qualitatively similar when normalized radius, in which radius is scaled by the radius of maximum wind, is instead considered. MSE variability is also partitioned into separate contributions from temperature and moisture. Doing so reveals that moisture variability is dominant throughout the TC. However, the temperature contribution is non-negligible near the TC center, contributing about 25% of the overall MSE anomaly there due to the warm core. Ongoing analysis suggests that the radial variability of CMSE is similar across storms of different intensity, except for tropical depressions which have less CMSE variability.