Infrared Sea Surface Temperature Measurements from Hurricane Edouard (2014) using GPS Dropsondes

Surface heat and moisture fluxes are key boundary conditions for numerical models of tropical cyclones (TCs) because they provide a significant energy source for storm development and intensification. However, direct measurement of surface fluxes in high-wind hurricane conditions has not been possible due to the severe safety risks associated with manned aircraft and the inability of properly outfitted fixed ocean platforms to survive. As a result, surface enthalpy fluxes are usually computed by a bulk method that requires measurements of sea surface temperature (SST) from Airborne eXpendable BathyThermograph (AXBT) and near-surface (10 m) wind speed, temperature and humidity obtained from GPS dropsondes. These bulk flux parameters can be measured by nearly simultaneous deployment of dropsondes and AXBTs from research aircraft. However, the practicality of relying on bulky ocean expendables for SST observations is limited due to aircraft weight and storage restrictions. Thus, placing SST sensors on the much smaller GPS dropsonde is an attractive alternative for regular SST measurements in the high-wind, cloud-covered conditions of TCs that satellites have difficulty observing. This study presents a new technique to include Infrared (IR) sensor technology onto the GPS dropsonde platform to obtain SST measurements. As part of the Sandy Supplemental project, so-called ‘IRsondes’ were constructed and then deployed during the 2014 hurricane season into Hurricane Edouard. Comparisons between SSTs measured by collocated IRsondes and AXBTs show very good agreement, especially in regions with little to no rain contamination. A description of the IRsonde and discussion of these promising results will be presented.