Abstract
The Nimbus 4 Temperature-Humidity Infrared Radiometer (THIR) monitors radiation in the 6.5–7.2 μm water vapor absorption region with a 23-km spatial resolution at the sub-satelite point. Radiation monitored in this spectral region results primarily from emission in the 250–500 mb region of the upper troposphere. The THIR 6.7μm observations are readily available in photofacsimile imagery form which shows very distinctive patterns associated with spatial variations in atmospheric water vapor.
These radiometric observations have been combined in several instances with moisture values measured in the upper troposphere by the standard radiosonde network. In each instance, the result is a much more consistent analysis showing increased spatial detail that agrees with the radiometric observations and does not compromise the conventional data. The improved moisture analyses show relatively dry and moist tongues that are very difficult or impossible to infer from the conventional data alone. The patterns in the moisture fields can be tracked over 12- and 24-hr periods. In addition, by keeping in mind the advective properties of the moisture field, success has been achieved in improving streamline analyses at the 400-mb level over data-sparse regions on a global scale.
