科研之友
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摘要
Spectral downwelling shortwave irradiance measurements made beneath overcast stratiform cloud decks at Ross Island, Antarctica (77.5 degrees S, 167 degrees E), are used in conjunction with discrete ordinates-based radiative transfer simulations to examine how mixed-phase clouds influence shortwave irradiance at the surface during austral spring-summer. From 10 October 2012 until 4 February 2013, an Analytical Spectral Devices (ASD, Inc.) spectroradiometer deployed at the Arrival Heights (77.82 degrees S, 166.65 degrees E) laboratory of McMurdo Station measured in 1 min averages the downwelling spectral hemispheric (direct plus diffuse) irradiance spanning visible (VIS) and near-infrared regions of the solar spectrum, from 350 to 2200 nm. Conservative-scattering cloud optical depth c is retrieved in the interval 1022-1033 nm, where the albedo of the snow-covered surface is lower than at VIS wavelengths. The impact of liquid versus mixed-phase cloud properties on the surface shortwave energy budget is discerned using irradiances in the 1.6 m Five case studies employ NASA A-Train satellite and ancillary meteorological data sets to investigate the macrophysical, microphysical, and shortwave radiative characteristics of clouds possessing distinct meteorological histories. Cloud systems within marine air masses arriving at Ross Island after transiting the West Antarctic ice sheet (WAIS) and the Ross Ice Shelf are radiatively dominated by the ice phase. In contrast, moist marine air moving directly onshore from the Ross Sea brings low clouds with a stronger influence of liquid water. Deep cyclonic disturbances over the Ross Sea are seen to be limited in their ability to deliver significant moisture as far south as Ross Island, where clouds are mainly optically thin.
- 出版日期2014-6-16
