Understanding Monsoon Changes Using a Normalized Gross Moist Stability Framework

Tuesday, December 11, 2018 - 09:45
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One of the grand challenges of climate science is understanding the changes of the tropical rain belts and monsoon systems owing to CO2-induced warming. A promising path forward is linking the fluxes of energy and moisture for tropical circulations. To this end we make use of the E3SMv1 model, where the divergence of moist static energy (MSE) and moisture have been calculated online, and a normalized gross moist stability (NGMS) diagnostic framework is employed to understand the linkages between changes in the flow of energy and moisture within the monsoon systems. We focus on the Asian summer monsoon system and utilize a series of coupled atmosphere-land and atmosphere-land-ocean simulations. Over land, decreases in NGMS are a major component of the precipitation increase to both warming and increased CO2 in simulations uncoupled to the ocean model. For the fully coupled experiments, NGMS decreases remain an important contributor to the increase in P-E. Furthermore, the decrease in NGMS contributing to increased precipitation has a non-negligible contribution from transient eddy fluxes of MSE, suggesting a time-mean view of the monsoon circulations is insufficient to quantify the link between future changes in the fluxes of energy and moisture.

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