Abstract
AbstractA dataset gathered over 369 days in various midlatitude sites with a 12-frequency microwave radiometric profiler is used to analyze the statistical distribution of tropospheric water vapor content (WVC) in clear and cloudy conditions. The WVC distribution inside intervals of temperature is analyzed. WVC is found to be well fitted by a Weibull distribution. The two Weibull parameters, the scale (λ) and shape (k), are temperature (T) dependent; k is almost constant, around 2.6, for clear conditions. For cloudy conditions, at T < −10°C, k is close to 2.6. For T > −10°C, k displays a maximum in such a way that skewness, which is positive in most conditions, reverses to negative in a temperature region approximately centered around 0°C (i.e., at a level where the occurrence of cumulus clouds is high). Analytical λ(T) and k(T) relations are proposed. The WVC spatial distribution can thus be described as a function of T. The mean WVC vertical profiles for clear and cloudy conditions are well described by a function of temperature of the same form as the Clausius–Clapeyron equation. The WVCcloudy/WVCclear ratio is shown to be a linear function of temperature. The vertically integrated WV (IWV) is found to follow a Weibull distribution. The IWV Weibull distribution parameters retrieved from the microwave radiometric profiler agree very well with the ones calculated from the 15-yr ECMWF reanalysis (ERA-15) meteorological database. The radiometric retrievals compare fairly well to the corresponding values calculated from an operational radiosonde sounding dataset.
Highlights
Water vapor is a component of paramount importance in the atmosphere in relation to weather and climate sensitivity research
In a companion paper analyzing the worldwide integrated WV (IWV) distribution from the ERA-15 database (Jeannin et al 2008), we found that k for tropical environment is negatively skewed, which agrees with Foster et al (2006)
The distribution of the vapor phase of tropospheric water was studied from 369 days of observations collected in various sites of western Europe with a 12-frequency microwave radiometric profiler
Summary
Water vapor is a component of paramount importance in the atmosphere in relation to weather and climate sensitivity research. By inversion of the radiances measured at the different channels through a neural network application, the radiometer retrieves, up to a height of 10 km, the vertical profiles of temperature and water vapor, cloud-base temperature and height, vertically integrated water vapor, and liquid water (ILW).
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