Novel measurements of Sea Surface Temperature in Tropical Cyclones obtained from GPS dropsonde

Surface heat and moisture fluxes are key boundary conditions for numerical models of tropical cyclones (TCs), as they provide a significant energy source. However, direct measurement of surface fluxes has been difficult given the severe conditions for manned aircraft or fixed ocean surface platforms to survive in strong TCs. As a result, surface enthalpy fluxes are usually computed by a bulk method that requires simultaneous measurements of sea surface temperature (SST) and near-surface (10 m) wind speed, temperature and humidity. GPS dropwindsondes and AXBTs may be simultaneously deployed from aircraft to estimate fluxes, since sondes measure the wind, temperature and humidity profiles to near the sea surface while AXBTs measure the SST. Because the relatively large and heavy AXBTs are limited in their utility due to aircraft weight and balance restrictions, placing SST sensors on the much smaller dropsonde is an attractive alternative for regular SST measurement in high-wind, cloud-covered conditions of TCs that satellites have difficulty observing. This study presents a new technique to include Infrared (IR) sensor to the existing GPS dropsonde system to obtain SST as part of the Sandy Supplemental project funded by NOAA. A large number (>60) of IR sondes were deployed in Hurricane Edouard (2014). Comparisons between SSTs measured by collocated IR sondes and AXBTs show good agreement. Surface fluxes are estimated using the bulk method with the IR sonde measurements. Their role in the intensification of Hurricane Edouard (2014) will be discussed.