Spectral Characteristics of the Global Moisture Distribution and Their Importance in Objective Analysis of Moisture for NWP Models.

摘要

Using data sets of observations of atmospheric variables on a global scale, the spectral distribution of atmospheric moisture is compared with that of wind and mass fields. Results show that, spectrally, the wind field has more of its power in higher wave numbers, and temperature and geopotential height have more power in lower wave numbers, than does moisture. Moisture has a shift in its power toward higher wave number with altitude, contrasting with a greater concentration of power in low wave numbers with altitude for geopotential. A baseline against which objective analysis methods for the respective variables may be tested is established, to determine how accurately each method represents the observed field. It is concluded on the basis of the unique characteristics of the moisture spectrum that special attention should be given to the design of a moisture analysis method. (Author)