Atmospheric water vapor over Antarctica derived from Special Sensor Microwave/Temperature 2 data

Abstract

Abstract. In polar regions, satellite microwave radiometry has not been successful in measuring the total water vapor (TWV) in the atmosphere. The difficulties faced in these regions arise from the very low water vapor burden of the atmosphere and the large and highly variable emissivities of ice surfaces in the microwave frequency range. By exploiting the advantages of the Special Sensor Microwave/Temperature 2 (SSM/T2), a method is developed to retrieve TWV over Antaxctica from satellite data. This method shows very low sensitivities to the change of surface emissivity and to the presence of water clouds. However, ice clouds may have considerable effects. Results of radiative transfer model simulation show that they may cause one to underestimate TWV using the proposed method and that the amount of underestimation is proportional to the ice water path of the ice cloud. Validations using radiosonde measurements and numerical model analyzes suggest that SSM/T2 retrievals have a high accuracy (maximum error < 10%) as long as TWV is <4.0kgm -2. Above this value, retrievals show a systematic overestimation.Presumably, this is a result of the seasonal difference between the validation and the training radiosonde data sets. TWV retrievals of 1 year's SSM/T2 data show clearly the seasonal variation of water vapor over Antarctica. Throughout the year the mean TWV over West Antarctica is nearly twice as high as that over East Antarctica; the temporal fluctuation of TWV over West Antarctica is also significantly stronger than over East Antarctica. This suggests that precipitation and water vapor transport in West Antarctica are more active than in East Antarctica. Using the same year's TWV data, we estimated the mean residence time of atmospheric water vapor over the Antarctica to be merely 3-4 days. This, however, is much shorter than the global mean of 9-10 days.

A microwave satellite water vapour column retrieval for polar winter conditions

“…The retrieval builds on the work of Miao et al (2001) and Melsheimer and Heygster (2008), employing auxiliary information for atmospheric conditions and numerical optimization. It was tested using simulated and actual measurements from the Microwave Humidity Sounder (MHS) satellite instruments.…”

Exceptional Terahertz Transparency and Stability above Dome A, Antarctica

“…The 183 GHz satellite-based measurements are also subject to ice particle scattering, which precludes an accurate measure of the surface temperature. Thus, the satellite measurements tend to underestimate the PWV when ice clouds are present (Miao et al 2001). By combining both measurements, one can even identify the periods during which the Pre-HEAT window was contaminated by snow or frost.…”

“…An independent, year-long assessment of the water vapor content above Dome A can be derived from 183 GHz passive radiometry from the Microwave Humidity Sounder (MHS) on NOAA-18 (Miao et al 2001). In Figure 1, the solutions for precipitable water vapor measured by NOAA-18/MHS in 2008 are zero-point calibrated with and overlaid atop automated Pre-HEAT measurements of submillimeter opacity, which are converted to water vapor column.…”

Surface Emissivity and Hydrometeors Derived from Microwave Satellite Observations and Model Reanalyses

“…However, the spatial and/or temporal coverage of most of these studies, is too limited to allow comprehensive global report of surface emissivity in the long term. For example, sea ice emissivity has been usually deduced for a cold, or ice-melting season over the local areas of the Arctic, rather than over the Antarctic, as in the study of Miao et al (2001).…”

“…During the past three decades, sea ice concentration and extent data have been obtained from several satellite-borne microwave radiometers using multichannels of 10, 19, 24, 37, 50.3, 85, 89, 140, 150, 157, and 220 GHz (e.g., Zwally et al 1983;Comiso 1983;Susskind et al 1984;Hollinger et al 1984;Grenfell and Lohanick 1985;Isaacs et al 1989;Hewison and English 1999;Miao et al 2001). These instruments include the Electronically Scanning Microwave Radiometer (ESMR), the Scanning Multichannel Microwave Radiometer (SMMR), the Special Sensor Microwave/Imager (SSM/I), and the Microwave Sounding Unit (MSU).…”