The Role of Non-Local Effects on Surface Sensible Heat Flux Under Different Types of Thermal Structures Over the Arctic Sea-Ice Surface

The effects of atmospheric thermal structure on the surface energy flux are poorly understood over the Arctic sea-ice surface. Here, we explore the mechanism of sensible heat exchange under different types of thermal structures over the Arctic sea-ice surface by using data collected during the Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition. The quadrant analysis indicates that strong surface temperature inversions below 100 m enhance non-local effects on the positive (upward) sensible heat flux ((w'theta') over bar) through entrainment of large eddies from the convective boundary layer aloft. However, strong surface inversions restrict the contributions of large eddies to the negative (downward) (w'theta') over bar due to intensified surface stability. By inspecting the existing parameterization schemes, we found that the European Center for MediumRange Weather Forecasts Integrated Forecasting System scheme fails to predict the impacts of non-local processes on the positive (w'theta') over bar, and an adjustment term to correct the bias of parameterized (w'theta') over bar is proposed. Plain Language Summary Since pre-industrial times, the increase of Arctic near-surface air temperature has been 2-3 times larger than the global average, known as the Arctic amplification. The atmospheric physical processes occurring in the boundary layer are essential for understanding the ongoing climate changes because they modulate the surface energy budget over the Arctic. However, scarce observations limit our understanding of surface heat flux exchange in this area. Recently, the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition was conducted in the central Arctic to support the urgent need for understanding and modeling the rapidly changing Arctic atmosphere-ice-ocean system. Based on the MOSAiC observations, we investigate the role of non-local effects on sensible heat flux under different types of atmospheric thermal structures over the Arctic sea-ice surface. To the best of our knowledge, this study represents the first time that the effects of strong surface inversions on negative and positive sensible heat fluxes over the Arctic sea-ice surface are found to be opposite. In addition, we propose a method for taking non-local effects into account, which can be applied in the European Center for MediumRange Weather Forecasts Integrated Forecasting System flux parameterization or other numerical models to correct the bias in parameterized positive sensible heat flux.