Moisture Profiling of the Cloudy Winter Atmosphere Using Combined Remote Sensors

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  • 1 NOAA Environmental Technology Laboratory, Boulder, Colorado
  • | 2 Research Applications Program, National Center for Atmospheric Research, Boulder, Colorado
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Abstract

A new method for deriving profiles of tropospheric water vapor and liquid water from a combination of ground-based remote sensors was applied and tested under winter conditions in Colorado. The method is an extension of physical retrieval techniques used to derive coarse profiles from passive microwave radiometer measurements. Unlike an earlier method, it does not depend on climatological data for first-guess profile inputs. Instead, information about current cloud conditions aloft, obtained with active remote sensors, is used to determine physically realistic, first-guess vertical distributions of the radiometer's integrated vapor and liquid measurements. In preliminary tests, the retrieved profiles were compared with in situ measurements by aircraft and radiosondes during the Winter Icing and Storms Project. The shape of the retrieved liquid profiles agreed well with the aircraft measurements, but heights, thicknesses, and amplitudes differed considerably in some cases. The derived vapor profiles agreed better with radiosonde measurements than the traditional climatological retrievals, but standard deviations of the dewpoint differences wore still quite large (5°C). In an integrated, unattended instrument design, the new method has the potential to provide continuous real-lime profiles of temperature, wind, humidity, liquid water, and pressure.

Abstract

A new method for deriving profiles of tropospheric water vapor and liquid water from a combination of ground-based remote sensors was applied and tested under winter conditions in Colorado. The method is an extension of physical retrieval techniques used to derive coarse profiles from passive microwave radiometer measurements. Unlike an earlier method, it does not depend on climatological data for first-guess profile inputs. Instead, information about current cloud conditions aloft, obtained with active remote sensors, is used to determine physically realistic, first-guess vertical distributions of the radiometer's integrated vapor and liquid measurements. In preliminary tests, the retrieved profiles were compared with in situ measurements by aircraft and radiosondes during the Winter Icing and Storms Project. The shape of the retrieved liquid profiles agreed well with the aircraft measurements, but heights, thicknesses, and amplitudes differed considerably in some cases. The derived vapor profiles agreed better with radiosonde measurements than the traditional climatological retrievals, but standard deviations of the dewpoint differences wore still quite large (5°C). In an integrated, unattended instrument design, the new method has the potential to provide continuous real-lime profiles of temperature, wind, humidity, liquid water, and pressure.

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