The observed relationship between precipitation and precipitable water (PW) over the tropical oceans was examined and showed that all four suites can capture the nonlinear relationship between precipitation and PW. But Suites 1, 2, and 3 generate too much precipitation for a given amount of PW. The figure below also shows a dry bias in the model initialization (day 0) compared to the observation, which contributes to larger dry biases in the forecasts. For this investigation, 0.25º x 0.25º Climate Prediction Center (CPC) morphing technique (CMORPH) precipitation analyses were used for precpitation observations and Special Sensor Microwave Imager/Sounder (SSMIS; f16+f17+f18 satellites) was used for PW observations.

More results can be found at:
GMTB's Final Report
Tar file of results