They actually measure a lot of parameters, not only temperatures, and in all the layers of the atmosphere. And they're _very_ sensitive. For some forecast needs

They actually measure a lot of parameters, not only temperatures, and in all the layers of the atmosphere. And they're _very_ sensitive. For some forecast needs (short term forecast, storms, etc.), the conditions under the atmospheric boundary layer (https://en.wikipedia.org/wiki/Planetary_boundary_layer https://en.wikipedia.org/wiki/Planetary_boundary_layer) is what matters most, so the microwave noise near the ground is definitely an issue.