Climatology of upper tropospheric relative humidity from the atmospheric infrared sounder and implications for climate

The observations illustrate many scales of variability in the atmosphere from the seasonal overturning Hadley-Walker circulation to high-frequency transient variability associated with baroclinic storms with high vertical resolution. The Asian monsoon circulation has a strong impact on upper-tropospheric humidity, with large humidity gradients to the west of the monsoon.

The vertical structure of humidity is generally bimodal, with high humidity in the upper and lower troposphere, and a dry middle troposphere. The highest variances in humidity are seen around the midlatitude tropopause. AIRS data are compared to a simulation from a state-of-the-art climate model.