Causes of model dry and warm bias over central U.S. and impact on climate projections

Authors:

Yanluan Lin¹, Wenhao Dong¹, Minghua Zhang^2,3, Yuanyu Xie¹, Wei Xue^1,4, Jianbin Huang¹& Yong Luo¹

¹ Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, and Joint Center for Global Change Studies (JCGCS), Tsinghua University, Beijing 100084, China.

² School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000,USA.

³ Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.

⁴ Department of Computer Science and Technology,Tsinghua University, Beijing 100084, China.

Abstract:

Climate models show a conspicuous summer warm and dry bias over the central United States. Using results from 19 climate models in the Coupled Model Intercomparison Project Phase 5 (CMIP5), we report a persistent dependence of warm bias on dry bias with the precipitation deficit leading the warm bias over this region. The precipitation deficit is associated with the widespread failure of models in capturing strong rainfall events in summer over the central U.S. A robust linear relationship between the projected warming and the present-day warm bias enables us to empirically correct future temperature projections. By the end of the 21st century under the RCP8.5 scenario, the corrections substantially narrow the intermodel spread of the projections and reduce the projected temperature by 2.5 K, resulting mainly from the removal of the warm bias. Instead of a sharp decrease, after this correction the projected precipitation is nearly neutral for all scenarios.

Citation:

Yanluan Lin, Wenhao Dong, Minghua Zhang, Yuanyu Xie, Wei Xue, Jianbin Huang & Yong Luo: Causes of model dry and warm bias over central U.S. and impact on climate projections, Nature Communications, DOI: 10.1038/s41467-017-01040-2