Temperature Weighting Functions of Saturated MLS Radiances

Plotted in the following are MLS temperature weighting functions at 18km tangent height as a function of only height/pressure, where horizontal differences of the weighting functions are ignored. The MLS 63GHz radiometer has 15 spectral channels distributed symmetrically around the O₂ lines, and eight altitude layers (28, 33, 38, 43, 48, 53, 61, and 80km) are featured by the saturated radiances in these channels. The channels farther away from the line center have less absorption and therefore produce the saturation layer at lower altitudes. The layer thickness is ~10km for channels 1-7, 9-15, and ~15km for channel 8 that is at the line center. The vertical broadening of the weighting functions is determined mainly by the instrument antanna field-of-view, which is a function of antenna diameter, observation frequency, and satellite altitude. It limits vertical scales of the waves that can be detected by MLS. With higher observation frequencies, such as 118GHz in EOS MLS instrument, the vertical resolution will be improved to allow detection of more small-scale waves.