A Surface Radiation Balance Dataset from Siple Dome in West Antarctica for Atmospheric and Climate Model Evaluation

Abstract

A field campaign at Siple Dome in West Antarctica during the austral summer 2019-2020 offers an opportunity to evaluate climate model performance, particularly cloud microphysical simulation. Over Antarctic ice sheets and ice shelves, clouds are a major regulator of the surface energy balance, and in the warm season their presence occasionally induces surface melt that can gradually weaken an ice shelf structure. This dataset from Siple Dome, obtained using transportable and solar-powered equipment, includes surface energy balance measurements, meteorology and cloud remote sensing. To demonstrate how these data can be used to evaluate model performance, comparisons are made with meteorological reanalysis known to give generally good performance over Antarctica (ERA5). Surface albedo measurements show expected variability with observed cloud amount, and can be used to evaluate a model's snowpack parameterization. One case study discussed involves a squall with northerly winds, during which ERA5 fails to produce cloud cover throughout one of the days. A second case study illustrates how shortwave spectroradiometer measurements that encompass the 1.6-micron atmospheric window reveal cloud phase transitions associated with cloud lifecycle. Here, continuously precipitating mixed-phase clouds become mainly liquid water clouds from local morning through the afternoon, not reproduced by ERA5. We challenge researchers to run their various regional or global models in a manner that has the large-scale meteorology follow the conditions of this field campaign, compare cloud and radiation simulations with this Siple Dome dataset, and potentially investigate why cloud microphysical simulations or other model components might produce discrepancies with these observations.

Broadband and filter radiometers at Ross Island, Antarctica: Detection of cloud ice phase versus liquid water influences on shortwave and longwave radiation

“…However, the low-cost, low-power, rugged and readily transportable instruments used in this study can easily be configured to accompany deep-field glaciological or geological expeditions, and this concept was demonstrated recently at Siple Dome in West Antarctica (Lubin et al, 2023). Additionally, some Antarctic research stations have existing atmospheric observation capabilities yielding important climatological results.…”

“…However, there are now compact, lowpower and fully automated digital all-sky imagers such as those manufactured by ALCOR System TM . One of these cameras was successfully deployed at Siple Dome in West Antarctica during the austral summer 2019-20 (Lubin et al, 2023).…”

“…The representative seasonal value is evaluated as the sum over all the optical depth and solar zenith angle bins, weighted by the observation's frequency of occurrence in each bin. As these observations from the CosRay site are not entirely representative of a snow-covered ice sheet or ice shelf, we can make a first order estimate for a snow surface from these observations using representative values of 0.88 for broadband snow albedo under cloud cover (Lubin et al, 2023) and 0.99 for broadband snow emissivity (e.g., Warren, 1982). Table 3 shows that overall, the shortwave differences are more significant than the longwave differences, although both are detectable with statistical significance.…”