Convective-Environmental Interactions in the Tropics

Published: 30 May 2019

Organized convection produces much of the precipitation in the tropics and the heat, moisture, and momentum transports associated with it drive large-scale circulations in the tropics into the extratropics. However, understanding convective organization and representing it in regional and global climate models remains a tremendous challenge in our field. This is in part due to the fact that organized convection encompasses a wide range of processes and scales, with microphysical and turbulent processes (< 100 m) interacting with convective processes (1-10 km), which in turn interact with mesoscale processes (> 100 km). These interactions are further dictated and complicated by the environment in which the organized convection is embedded.

Observing these processes, much less simulating them and their interactions in a numerical framework, is a daunting task, but becoming more possible with ARM and ASR observational and modeling resources. In particular, this proposal will focus on measurements and modeling efforts associated with the GoAmazon2014/5 field campaign that took place in the central Amazon for the entirety of 2014-15 to better understand mesoscale convective organization and its relationship to the environment. Emphasis will be placed on creating radar-based climatologies of factors that impact convective organization, including (i) downdraft and cold pool occurrence, (ii) wind shear and storm propagation, and (iii) heating profiles and how these factors vary diurnally and seasonally in the Amazon. The observational work will utilize innovative and cutting-edge tools, including a “descending arm” over small regions of the large-scale radar domain to quantify downdraft occurrence and strength, cell-tracking algorithms that use both radar and satellite data to quantify convective system propagation and evolution, and multiple estimates of heating profiles to better constrain their uncertainty.

These climatologies will be linked to metrics of mesoscale organization as observed by radar to determine their importance to organized convection. The results will further be compared to regional cloud and climate model runs to ascertain the ability of the models in representing these processes and in producing realistic organized convective structures. The climatologies will provide important convective context for many other observational and modeling efforts associated with GoAmazon2014/5 and the radar-based methods can be extended to other campaigns, such as AMIE, to analyze convective-environmental interactions over tropical ocean compared to tropical land. As most climate models do not parameterize organized convection, this work will provide guidance on ways to incorporate grid-scale environmental factors to predict important features of mesoscale convective organization.

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This work was supported by the U.S. Department of Energy’s Office of Science, through the Biological and Environmental Research program as part of the Atmospheric System Research program.