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The Role of Divergent Flow in the Parameterized and Resolved Convective Precipitation over the Amazon Forest

Presentation Date
Wednesday, December 13, 2017 at 8:00am
New Orleans Ernest N. Morial Convention Center - Poster Hall D-F



The Amazon tropical forest is a key region for the global-scale biogeochemical cycles and associated climate feedback owing to its abundant rainfall. However, realistically simulating the rainfall over the region remains a challenging task for global models. Our previous study focusing on the Community Atmosphere Model version 5 (CAM5) during the wet season suggested inaccurate divergent circulations over the central-western Amazon leads to biased moisture convergence, which then affect the coupling between the tropospheric moisture and parameterized deep convection. The biased mass divergence is likely a dynamic response of the northeasterly flow to the Guiana Highlands that are marginally resolved by 1° grid. Here we test this scenario by comparing CAM5 simulations with the default finite-volume dynamical core and with the Model for Prediction Across Scales (MPAS), a dynamical core that has different characteristics in mesoscale divergent flow, both run at ~1° grids. A convection-permitting (∆x ~ 4km) simulation is also run by using MPAS's regionally refined mesh centered over the Amazon, serving as a reference solution by better resolving the topography and other surface forcings. The simulation period includes GoAmazon's Intensive Operation Period 1 whose observations serve as additional reference. Preliminary results focusing on the divergent circulations, tropospheric moisture, and its influence on the diurnal cycle of deep convection will be presented.

Funding Program Area(s)