Wednesday, 5 June 2002: 8:30 AM
Performance of Radiative Transfer Codes under Arctic Conditions
Data collected during the SHEBA (Surface Heat Budget of the Arctic Ocean) field experiment and at the Barrow ARM site are used to evaluate shortwave and longwave radiative transfer (RT) codes used in climate models and for remote sensing applications under Arctic conditions. Several characteristics of the Arctic environment make RT difficult. These include low sun angles, high surface albedo with large spectral variations, low temperatures and water contents (in winter), large temporal variations in aerosol optical depth caused by sporadic Arctic Haze events, and the common occurrence of low water paths in clouds. Broadband and spectral radiative fluxes observed at the surface and the TOA are used to evaluate the RT codes under a variety of Arctic conditions including clear-sky low aerosol, clear-sky Arctic Haze, and cloudy-sky (liquid, mixed-phase and cirrus).
Separate components of the codes (e.g., radiative transfer scheme, surface albedo parameterization, cloud and aerosol optical parameterizations) are evaluated individually. The clear-sky, low aerosol cases are used to compare different RT schemes. The clear sky high aerosol and cloud cases are used to test different parameterizations of aerosol and cloud optical properties, respectively. The sensitivity of the simulated surface fluxes to systematic variations in cloud and aerosol properties, surface albedo and precipitable water will be determined. Model to model variations in this sensitivity reveal the differences in their potential response under climate change scenarios.