Drifting air-sea interface buoy (DrIB): a practical platform for global air-sea observations

Global-scale measurements of air-sea variables and associated boundary-layer processes are crucial for determining ocean surface fluxes, understanding atmosphere-ocean interactions, validating remote sensed data, and enhancing coupled model simulations. Traditional observation platforms like ships and moored buoys face limitations in capturing the spatial-temporal variabilities of air-sea interactions globally. Drifting and autonomous surface vehicles have emerged as promising complements for the air-sea interface observation. We introduce the Drifting air-sea interface buoy (DrIB), a low-cost mini-buoy designed to measure essential climate and ocean variables at the air-sea interface in a free-drifting way, while ensuring the stability of the buoy's attitude. It is capable of surface seawater and 3-meter meteorological observations, including sea surface temperature, air pressure, temperature, humidity and vector wind speed. By the end of 2022, over 74 DrIBs were tentatively deployed in the regions of the Kuroshio Extension, Western Pacific, South China Sea, and Southern Ocean. Comparative data analyses with a moored buoy (Kuroshio Extension Observatory, KEO for short, an Ocean Climate Station operated by NOAA in the Kuroshio Extension) and ship-borne measurements proves the feasibility of DrIB's observation at the air-sea interface. The DrIB-KEO comparison experiment demonstrates statistically consistent across observation parameters (wind speed, air temperature, relative humidity, air pressure and sea surface temperature), with correlation coefficients exceeding 0.95. DrIB demonstrates promising potential in delivering global air-sea interface variables and turbulent heat fluxes. Future regional and global deployments of DrIBs will enhance satellite remote sensing data validation and improve the study of meso/frontal scale air-sea interactions, advancing ocean-atmosphere coupled model simulations.