Spatial Variability of Dropsonde-Derived Moist Static Energy in North Atlantic Tropical Cyclones

The spatial variability of moist static energy (MSE) and its column-integral (CMSE) around tropical cyclones (TCs) are known to help prognose TC development. Though limited in number and spatial coverage per TC, modeling work suggests that dropsondes, when strategically deployed, can reliably capture radial MSE and CMSE variability. This study uses North Atlantic upper-level reconnaissance dropsondes from 1996 to 2021 to produce the most extensive observational analysis of MSE structure in TCs to date. MSE and CMSE decrease with distance from the TC center. MSE spatial variability is larger in Category 1 and 2 hurricanes compared to tropical storms, and generally largest after a TC's lifetime maximum intensity. Moisture dominates the MSE spatial variability but temperature contributes in the upper levels near the TC center. While differences in MSE spatial variability between weakening and intensifying TCs are less clear, raw MSE tends to be greater in intensifying TCs at most radii and vertical levels. Moist static energy (MSE) is a thermodynamic variable combining contributions from temperature, water vapor, and gravity. MSE has been useful in describing processes important for atmospheric convection and tropical cyclone (TC) development. This study investigates the average MSE structure of observed Atlantic TCs using measurements from dropsondes, which are instruments dropped into TCs from Hurricane Hunter aircraft. MSE decreases with distance from the TC center, largely due to reduced moisture at large radii, though reduced temperature is important at higher altitudes. Further analysis was performed according to TC intensity and the rate of TC intensity change. MSE decreases more quickly from the TC center in Category 1 and 2 hurricanes compared to tropical storms. Intensifying and weakening TCs do not show substantial differences in how MSE varies in space. Instead, the MSE itself is larger in intensifying storms at most altitudes and distances, especially farther from the TC center. Moist static energy (MSE) and its column integral decrease with distance from the TC center in observations Moisture dominates the spatial variability of MSE but temperature contributes at upper levels near the TC center MSE spatial variability is larger in Category 1-2 hurricanes than tropical storms and MSE itself is larger in more rapidly intensifying TCs