The TIROS Operational Vertical Sounder (TOVS) data consist of radiance observations at several wavelengths from the NOAA polar orbit satellites. Radiance observations relevant to tropospheric studies are taken by the High-resolution Infrared Spectrometer (HIRS).
TOVS radiance data are archived by NOAA as idealized nadir-viewing clear-sky brightness temperatures after applying corrections to the raw observations for satellite view angle and cloud contamination. (see Chesters and Sharma, 1992 and Salathé and Chesters, 1995).
Chesters and Neuendorfer () developed the data set used in these studies. The brightness temperatures are a linear combination of the TOVS 6.7 and 7.2 micron channels, which enhances the sensitivity to the upper-most levels of the water vapor profile. The peak sensitivity of the composite brightness temperature is at 300 mb; thus, it serves as a better indicator of upper-tropospheric moisture and more rigorous test of model predictions than the 6.7 micron channel alone. To create daily images, the data along the satellite sub-orbital swaths were placed on a polar stereographic grid using the NOAA objective analysis, and then interpolated to a 5degx5deg rectangular grid from 40S to 40N.
To evaluate model simulations of upper-tropospheric moisture using satellite data, the most reliable method is to compute the satellite observation from the model analyses. To compute brightness temperatures corresponding to the TOVS observations, we performed radiative transfer calculations on the daily data using a narrow band molecular absorption model.