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Absorption Properties of Supercooled Liquid Water between 31 and 225 GHz: Evaluation of Absorption Models Using Ground-Based Observations

Journal Article · · Journal of Applied Meteorology and Climatology
 [1];  [1];  [1];  [1];  [2];  [3];  [4]
  1. Univ. of Cologne, Cologne (Germany)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. NOAA/National Severe Storms Lab., Norman, OK (United States)
  4. Academiz Sinica Institute of Astronomy and Astrophysics, Taipei (Taiwan)
+ Show Author Affiliations
Microwave radiometers (MWR) are commonly used to quantify the amount of supercooled liquid water (SLW) in clouds; however, the accuracy of the SLW retrievals is limited by the poor knowledge of the SLW dielectric properties at microwave frequencies. Six liquid water permittivity models were compared with ground-based MWR observations between 31 and 225 GHz from sites in Greenland, the German Alps, and a low-mountain site; average cloud temperatures of observed thin cloud layers range from 0° to –33°C. A recently published method to derive ratios of liquid water opacity from different frequencies was employed in this analysis. These ratios are independent of liquid water path and equal to the ratio of αL at those frequencies that can be directly compared with the permittivity model predictions. The observed opacity ratios from all sites show highly consistent results that are generally within the range of model predictions; however, none of the models are able to approximate the observations over the entire frequency and temperature range. Findings in earlier published studies were used to select one specific model as a reference model for αL at 90 GHz; together with the observed opacity ratios, the temperature dependence of αL at 31.4, 52.28, 150, and 225 GHz was derived. The results reveal that two models fit the opacity ratio data better than the other four models, with one of the two models fitting the data better for frequencies below 90 GHz and the other for higher frequencies. Furthermore, these findings are relevant for SLW retrievals and radiative transfer in the 31–225-GHz frequency region.
Research Organization:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Organization:
German Science Foundation; National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
1396302
Journal Information:
Journal of Applied Meteorology and Climatology, Journal Name: Journal of Applied Meteorology and Climatology Journal Issue: 4 Vol. 53; ISSN 1558-8424
Publisher:
American Meteorological SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (2)

Observed relations between snowfall microphysics and triple-frequency radar measurements: TRIPLE-FREQUENCY SIGNATURES OF SNOWFALL journal June 2015
The origin of the Debye relaxation in liquid water and fitting the high frequency excess response journal January 2017

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Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
Absorption
Cloud microphysics
Cloud retrieval
Cloud water/phase
Microwave observations
Radiative transfer