Temperature profile retrieval by two-dimensional filtering

A two-dimensional spatial filter, optimum in the minimum-mean-square error sense, has been used to retrieve atmospheric temperature profiles from TIROS-N and NOAA-6 Microwave Sounding Unit measurements. This approach considers correlations both in the vertical and horizontal (along the orbital track) directions. It is found that lower retrieval errors result from the 2-D technique, compared with the 1-D technique, especially in the troposphere. The additional horizontal information used in the 2-D formulation substantially improves temperature retrievals over a severe cold front where vertical correlations are lessened. The improved results of the 2-D filter in the upper troposphere point to the presence of profile components in the null space of the weighting functions that are horizontally correlated with the observed data.