Figure 3.16. Vertical weighting functions (grey) depicting the layers sampled by satellite MSU measurements and their derivatives, and used also for radiosonde and reanalysis records. The right panel schematically depicts the variation in the tropopause (that separates the stratosphere and troposphere) from the tropics (left) to the high latitudes (right). The fourth panel depicts T4 in the lower stratosphere, the third panel shows T2, the second panel shows the troposphere as a combination of T2 and T4 (Fu et al., 2004a) and the first panel shows T2_LT from the UAH for the low troposphere. Adapted from Karl et al. (2006).