Instantaneous fluctuations of temperature and moisture in the upper troposphere and tropopause region. Part 1: Probability densities and their variability

Abstract

Using nine years (1995--2003) of MOZAIC temperature and humidity data, we analyse the statistics of instantaneous fluctuations of temperature, relative and absolute humidity with various spatial resolutions. We determine the probability density functions (p.d.f.s), their low order moments up to kurtosis, and study how these quantities vary with spatial resolution and with the background mean relative humidity. Seasonal and geographical variations are considered. Bivariate distributions of joint fluctuations of temperature and relative humidity are presented as well. These investigations are thought to provide an observational basis for the validation of statistical cloud schemes for large--scale models. For instance, we can show that temperature fluctuations cannot be neglected in such a scheme and that the bivariate distributions of simultaneous fluctuations of temperature and humidity have to be taken into account.