d. Specific Humidity Distribution (Troposphere)
Figure 1 shows the meridional distributions of specific humidity. As an overall trend, the height of the region with high specific humidity over the equatorial region increases with increasing solar constant. This phenomenon matches the occurrence of increasing height of the Hadley circulation, which is caused by the increase of solar constant.
The specific humidity distributions from Experiments S1200 and S1380 are characterized by a pattern in which the maximum value occurs over the equatorial region and high values leak into the surroundings from the maximum value. This pattern is attributable to water vapor transport into upper layers by cumulus convection and horizontal water vapor transport by the Hadley circulation over the equatorial region. In Experiments S1500, S1550, and S1570, the amount of water vapor in the lower layers over the high-latitude regions increases. This result indicates that an increased solar constant causes increased global water vapor content.
Figure 1:Distributions of specific humidity (kg/kg) in equilibrium states.