Radiative Heating Errors in Naturally Ventilated Air Temperature Measurements Made from Buoys*

Abstract

Solar radiative heating errors in buoy-mounted, naturally ventilated air temperature sensors are examined. Data from sensors with multiplate radiation shields and collocated, fan-aspirated air temperature sensors from three buoy deployments during TOGA COARE (Tropical Ocean Global Atmosphere Coupled Ocean?Atmosphere Response Experiment) and the Arabian Sea Mixed Layer Dynamics Experiment are used to describe the errors in the naturally ventilated measurements. The naturally ventilated sensors have mean daytime errors of 0.27°C and maximum instantaneous errors of 3.4°C. The errors are at times larger than the difference between the air and sea surface temperatures. These errors lead to mean daytime biases in sensible and latent heat fluxes of 1?4 W m?2 and instantaneous errors up to 22 W m?2. The heating errors increase with increasing shortwave radiation and diminish with increasing wind speed. The radiative heating is also found to be a function of sun elevation with maximum heating errors occurring at elevations of approximately 45°. A simple model of sensor heating that balances the radiative heating with convective and conductive cooling is presented. This model can be used with empirically determined coefficients and observations of wind speed and shortwave radiation to quantify the radiative heating errors in naturally ventilated air temperature sensors.