09/15/2008

Evolution of Clouds in the Tropical West Pacific Fair Weather Clouds Lead to Stormy Days Ahead

Summary

Scientists in the DOE Atmospheric Radiation Measurement (ARM) Program used ground-based radars that penetrate through clouds to provide a more accurate picture of tropical clouds. They found that satellites underestimate cloud heights, especially when multiple cloud layers are present. By combining the satellite and ground-based data, the investigators determined how clouds change as the weather varies from fair and dry to humid and rainy conditions over 30-60 day periods. The ARM radars showed that the low and mid-level clouds that populate the sky under fair weather gradually give way to higher clouds over 1-2 weeks, supporting the theory that the shallow clouds slowly moisten the atmosphere and pave the way for stormy weather to break out later. Climate models simulate this transition poorly, suggesting that this new data can help improve the models representation of clouds and their effect on weather and climate.

References

Chen, Y., and A.D. Del Genio, 2008: Evaluation of tropical cloud regimes in observations and a general circulation model. Climate Dynamics, doi:10.1007/s00382-008-0386-6