Climate change research requires knowledge of the temperature of the ocean right at the surface to estimate the transfer of heat between the air and the water. This temperature, known as the skin temperature, can be up to a half degree Celsius (about one degree Fahrenheit) cooler than the temperature immediately below, known as the sub-skin temperature. In practice, models rather than measurements of the skin temperature are used since current technology to measure the skin temperature is expensive and complicated. This technology uses a non-contact sensor known as an infrared radiometer that remotely measures the thermal radiation coming from the ocean. The skin temperature model needs a measure of the temperature just below the surface (known as the sub-skin temperature) in order to accurately predict the skin temperature. When a ship is used, the sub-skin temperature can be measured by towing a thermometer along the surface. In the future, measurements will be made from drones, where towing a thermometer is impractical. This research will use technology improvements and insight from new research to develop an instrument that can measure both the skin and sub-skin temperature from drones, as well as from buoys.
Current models for the cool skin effect provide adequate skin temperature accuracy for ocean surface fluxes required for climate research. However, this level of performance is achieved only when the cool skin model is initialized with a contact measurement of very near surface temperature using a towed sensor known as a sea snake. The advent of reliable unmanned surface vehicles (USVs) has fostered a growing community consensus for the need to make accurate flux measurements autonomously. Since deployment of a sea snake from USVs is impractical, an alternative means of obtaining very near surface temperature (sub-skin) and/or the skin temperature itself is required to ensure the necessary flux accuracy. Recent results indicates that accurate infrared (IR) measurements of skin temperature from USVs should now be practical. Furthermore, these results show that combining an IR camera with a calibrated radiometer system can provide the sub-skin temperature remotely. This project will develop and test IRISS (InfraRed In situ Skin and Subskin), an innovative IR-based sensor system to remotely and simultaneously measure skin and sub-skin temperature under all weather conditions for routine deployment on USVs and buoys. IRISS will be compact, low-power, and cost effective by exploiting the increased stability of commercially-available sensors and will provide measurements with accuracy comparable to current systems. The project will include side-by-side comparisons with an existing ship-based system for each intended platform. Widespread use on USVs and buoys will greatly increase the number and coverage of skin and sub-skin temperature measurements. The resulting improvements to models for the cool skin and near surface temperature stratification will enhance topical oceanographic research such as gas transfer, address current operational forecast priorities, and improve satellite SST algorithm development.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
