PAOC Colloquium: Kathleen Schiro (JPL)
Monday, March 18, 2019 at 12:00pm to 1:00pm
Building 54, 54-915
21 AMES ST, Cambridge, MA 02139
Relationships between tropical ascent and high cloud changes with warming and directions toward model
Tropical ascent area (Aa) and high cloud fraction (HCF) are projected to decrease with surface warming in Coupled Model Intercomparison Project (CMIP5) climate models. Perturbing deep convective parameters in an atmosphere-only version of the Community Earth System Model results in a strikingly similar spread and relation between the HCF and Aa responses to warming compared to the CMIP5 multi-model ensemble, with a narrowing of Aa corresponding to a greater HCF reduction. This similarity suggests that the CMIP5 intermodel spread in the response of HCF and Aa to warming could be attributed to model differences in deep convective parameterization. This stresses the need to inform revisions to convective parameterization with process-oriented studies of deep convection. Efforts to inform revision to convective mixing parameterization and diagnose deep convective onset in GCMs will thus be presented. While differences in cloud physics parameterization could also contribute significantly to the CMIP5 intermodel spread in HCF changes, perturbing cloud physics produces a weaker circulation response and dissimilar HCF-Aa relation to that seen in CMIP5. This can be attributed to the fact that decreases in HCF reduce cloud radiative heating, which opposes Aa narrowing by decreasing atmospheric stability and net energy input. Implications of these results will be discussed and ideas for future exploration will be presented.
About this Series
The PAOC Colloquium [PAOCC] is a weekly interdisciplinary seminar series that brings together the whole PAOC community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, but also talks about e.g. societal impacts of climatic processes. The seminars take place on Monday from 12-1pm in 54-923. Lunch is provided after the seminars to encourage students and post-docs to meet with the speaker. Besides the seminar and lunch, individual meetings with professors, post-docs, and students are arranged. Contact the 2018/2019 Coordinators: paoc-colloquium-comm@mit.edu.
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