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The winter time South Pole tropospheric water vapor column: Comparisons of radiosonde and recent terahertz radiometry, use of the saturated column as a proxy measurement; and inference of decadal trends

Published

Author(s)

Richard A. Chamberlin, Erich N. Grossman

Abstract

We use a fifty year record of winter time radiosonde observations at the South Pole to estimate the precipitable water vapor column (PWV) over the entire period. Humidity data from older radiosondes is of limited reliability; however, we think an estimation of PWV is possible using temperature data because the winter time lower troposphere is very close to saturated. From temperature data we derived PWVSAT which is the PWV if the troposphere was saturated over the entire column. Comparisons to recent radiosonde humidity data indicates that PWV ≅ 0.88 PWVSAT. Since 1998 a CMU/NRAO 860GHz atmospheric radiometer has been operating at the South Pole producing zenith opacity data, τo. It is expected that τo ∝ PWV and also τo ∝ PWVSAT since the lower atmospheric column is near to saturation. We compare trends in τo, PWVSAT, and PWV. PWV and PWVSAT showed little trend in the last fifty years, 1961-2010, except perhaps in the last two decades when PWVSAT was below average followed by an increasing trend to above average. This increasing trend in the last decade was also observed in τo except for the final two years when it appears something changed in the instrument response. PWVSAT is a useful metric for estimating PWV in the earlier years of winter time South Pole radiosonde, and it is generally useful for evaluating the winter time performance of radiosonde humidity and atmospheric opacity instrumentation.
Citation
Atmospheric Research
Volume
Vol 117

Keywords

radiosonde, Antarctica, decadal trends, troposphere, water vapor, South Pole, THz radiometry
Created July 7, 2012, Updated February 19, 2017