Retrieval of tropospheric water vapor scale height from horizontal turbulence structure

Abstract

A scale height of the vertical water vapor distribution in the troposphere is shown to be related to the rate at which the total integrated water vapor (IWV) decorrelates with horizontal separation. This relationship is based on the departure from simple Kolmogorov behavior of the turbulence structure of the IWV as the horizontal separation becomes a significant fraction of the scale height of the three dimensional (3D) turbulence. The relationship is demonstrated by comparisons between direct measurements of the vertical water vapor distribution, by radiosondes, and coincident estimates of the horizontal turbulence structure, using the TOPEX Microwave Radiometer (TMR). This provides a new method by which to resolve some of the vertical structure of lower tropospheric water vapor from space. The turbulence structure estimator is applied to a larger body of TMR data to produce a sequence of images describing the dynamics of water vapor scale height across the tropical Pacific Ocean. The cyclical evolution of a basin scale east/west ridge of water vapor with high scale height near 5/spl deg/ north latitude is detected which is consistent with other observations of the Madden and Julian Oscillation. The general technique presented should be applicable to many other existing data sets which image the horizontal distribution of IWV, e.g., those of the Defense Meteorological Satellite Program's special sensor microwave/imagers.