57 Understanding Summertime Regional Rainfall Projections through a Hierarchical Modeling Approach

Monday, 26 June 2017
Salon A-E (Marriott Portland Downtown Waterfront)
Patrick Kelly, PNNL, Richland, WA; and J. Lu and L. R. Leung

The summertime asymmetric circulation (or stationary wave pattern) is characterized by continental monsoons and oceanic subtropical highs. Together they play a critical role in the water cycle, both in the seasonal mean monsoon circulation and in the steering of transient tropical cyclones tracks and moisture pathways around the subtropical high. Better understanding of the subtropical stationary wave response to climate change is thus fundamental to advancing prediction of regional mean precipitation as well as extreme events.

A framework for how idealized modeling experiments can fruitfully inform complex projections will be presented. Using both the CMIP5 archive as well as dedicated modeling experiments, we leverage a three tier approach to understand the stationary wave response to CO2 forcing and its role in dictating precipitation changes in summer: (1) comprehensive coupled simulations (2) AMIP-style simulations (3) aquaplanet-slab simulations with idealized stationary wave perturbations. This talk will discuss projected changes in the asymmetric circulation with an emphasis on how summertime stationary waves shape the regional scale precipitation response.

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