A New Approach for Obtaining Advection Profiles: Application to the SHEBA Column

Abstract

Time-averaged vertically integrated 3D advections are inferred from heat and moisture budgets obtained from observations at the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment for April, May, June, and July. Advection was a source of heat and moisture in the column budgets during the time period, balanced mostly by precipitation and radiative cooling. These inferred advections are used to evaluate and correct the 3D temperature and water vapor advection profiles obtained from operational forecasts of the ECMWF model. Advections from the ECMWF model are generally too warm and moist, particularly in July. These biases lead to overpredictions of temperature and water vapor mixing ratio, often exceeding 12 K and 50%, respectively, in monthlong single-column model simulations. A correction algorithm is developed that constrains the ECMWF advections to the observed column budgets, thereby eliminating a first-order source of error in the advective forcing. The approach described here differs from other constrained analysis techniques since it does not require a spatial network of observed or analyzed fields. Simulations forced with the corrected advections show significant improvements in the modeled temperature and water vapor profiles and precipitation. It is demonstrated that using the new observationally constrained advection profiles allows for a less ambiguous evaluation of the model's physical parameterizations.