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Laura Riihimaki

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Surface broadband shortwave and longwave irradiance are key components of the surface energy budget and give insight on atmospheric constituents like clouds and aerosols as well as provide useful information for model evaluation. Surface irradiance measurements are particularly difficult to make over the ocean where few measurement platforms exist, and where the motion of ships and buoys makes the accuracy of the measurements challenging. During the US DOE ARM Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) field campaign, new shipborne broadband radiation systems (SHIPRAD) were deployed for the first time to test correction. The systems include pyrgeometer measurements for measuring longwave irradiance, an unshaded pyranometer to measure shortwave irradiance, a navigation system measuring pitch/roll/heading, and an SPN1 shortwave radiometer that measures direct and diffuse components with no moving parts. A tilt correction methodology was used to correct 1 second temporal resolution shortwave irradiance data for ship motion, designed to correct tilts of 10 degrees or less to within 10 W/m2. Two SHIPRAD systems were deployed on the port and starboard sides of the ship, and the measurements were combined in order to be able to eliminate measurements shaded by ship structures. The new methodology allows for high-temporal resolution irradiance measurements with higher accuracy. Results will be presented on the accuracy of the tilt correction methodology and the irradiance measurement results throughout the campaign.