Evaluation of cloud and water vapor simulations in CMIP5 climate models using NASA "A-Train" satellite observations

We find more than half of the models show improvements from CMIP3 to CMIP5 in simulating column-integrated cloud amount, while changes in water vapor simulation are insignificant.

For the 19 CMIP5 models, the model spreads and their differences from the observations are larger in the upper troposphere (UT) than in the lower or middle troposphere (L/MT). The modeled mean CWCs over tropical oceans range from ~3% to ~15× of the observations in the UT and 40% to 2× of the observations in the L/MT. For modeled H2Os, the mean values over tropical oceans range from ~1% to 2× of the observations in the UT and within 10% of the observations in the L/MT.