GESTAR II Seminar Series, June 8 at 11:00am

Join us for a virtual seminar by Dr. Xianglei Huang, Professor of Climate and Space Sciences and Engineering, University of Michigan. His talk is titled "Including two missing longwave physics into the earth system model."

Date and Time: Thursday, June 8, 2023 at 11:00am

Join us via Teams.

Abstract: 

"Climate models often ignore cloud scattering and surface emissivity in the longwave (LW) for computational efficiency. I will first review why such approximations were made decades ago, when the focus of model developments was not the same as that of today. Such approximations can cause biases in radiative fluxes and affect simulated climate, especially in the Arctic. We implemented treatments to both physics into the DoE Energy Exascale Earth System Model (E3SM) version 2 and assessed their impacts on the simulated mean-state global climate as well as climate sensitivity. By turning on and off the switches in the modified E3SMv2 model, we studied the changes in mean-state climate due to cloud LW scattering and surface emissivity effects. Cloud LW scattering warms the entire global troposphere by ~0.4 K on average; the warming is stronger in the Arctic (~0.8 K) than in the tropics due to the Arctic amplification phenomenon. When realistic emissivity is incorporated into the model, the surface skin temperature increases by 0.36 K instantaneously on a global average. Surface skin temperature, as well as surface air temperature and tropospheric temperature, further increases by 0.19 K due to the inclusion of surface spectral emissivity. The mean-state climate changes due to both effects are linearly additive. We further carried out simulations under the abrupt 4xCO2 scenario and found that total global-mean climate feedback does not change significantly after including either or both physics. Nevertheless, cloud radiative feedback could change as much as 10% when such processes are included. The connections of such modeling activities with NASA and ESA's ongoing missions will be discussed. I will conclude the presentation with further contemplations on the outlook of the surface-atmospheric radiative coupling in the earth system models."

Biography: