Parametrization schemes of incident radiation in the North Water Polynya

Surface incident radiation is a critical component of the Arctic surface energy balance making it important for sea-ice model parametrizations to properly account for these fluxes. In this article, we test the performance of various incident short-wave (K down arrow) and long-wave (L down arrow) flux parametrizations using unique observations from the 1998 International North Water (NOW) Polynya Project between March and July. The dataset includes hourly observations over terrestrial, fast-ice and full marine polynya environments allowing for parametrization comparisons between each environment and determination of any seasonal biases. Performance testing is highly dependent on observed input parameters that contain relative errors, however, significant differences between the marine and fast-ice fluxes are evident. Results are very similar between the terrestrial and fast-ice sites. The best K down arrow clear-sky schemes underestimate fluxes in the colder season and overestimate them in the warm season, with greater biases in the marine setting. The K down arrow cloudy-sky results suggest a similar cold and warm season bias but with greater magnitudes, especially in the marine environment. The K down arrow cloudy-sky schemes require seasonal improvements, especially in the marine atmosphere. The L down arrow clear-sky fluxes were generally overestimated during the colder season. Accounting for a less emissive atmosphere resulted in better flux approximations in all environments. L down arrow cloudy-sky fluxes were generally underestimated. Adjusting the cloudy-sky emissivity improved the estimated fluxes, however, results were very different in the marine setting. The L down arrow cloudy-sky parametrizations may require re-evaluation due to a consistent negative bias as the observed flux increases.