Cooperative Institute for Research in Environmental Sciences

Science Rendezvous > 2009 Posters
The presenter is listed in italics. All poster presentations are the property of their respective authors. Please contact the authors for permission to use images, information, or ideas.

Response of hydrologic cycle over the continental US to ENSO forcing: A comparsion between observations and model simulations

Tao Zhang, De-Zheng Sun, Martin P. Hoerling, and Judith Perlwitz

The response of water vapor and clouds to canonical La Nina is examined in this study to understand the differences in the climate response over the continental US to ENSO forcing between observations and model simulations. The results show that the negative surface temperature response in GFDL AM2.1 over the Northwest of US during SON (September-November) to La Nina forcing is accompanied with a negative response in the surface shortwave flux. Consistent with the biases in the shortwave flux, the response in the the middle and low cloud cover over that region in the model is found to be excessive.The excessive response of low cloud in the model over the NW of US is consistent with a positive bias in the response of surface humidity. The lack of response in precipitation over the Northwest of US in the model is accompanied with a deficit in the response of total column precipitable water. The deficit mainly comes from a dry bias in the middle and upper troposphere. The lack of response of water vapor in the middle and upper troposphere is consistent with a weaker response of vertical motion.