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The Diurnal Cycle of Precipitation and Organized Convection in a Set of Global Mesoscale Simulations with the NASA GEOS AGCMThe NASA Global Modeling and Assimilation Office (GMAO) has conducted a series of 40-day nonhydrostatic global simulations with horizontal grid spacing ranging from 200 km to 3 km, as part of the DYAMOND model intercomparison project. The Goddard Earth Observing System (GEOS) model was run with the Grell-Freitas scale-aware convection scheme, which smoothly reduces parameterized deep convection with increasing resolution. Here we evaluate the diurnal cycle and other statistics of precipitation and organized convection as a function of resolution. For validation we use the 0.1 degree IMERG precipitation and 4 km Merged IR brightness temperature datasets, focusing on four regions: the continental United States, Amazonia, the equatorial Indian ocean, and the Maritime Continent. Early results indicate good phase agreement but excessive magnitude of the continental diurnal cycle of precipitation at coarser resolutions, with improved magnitude as resolution increases and the role of parameterization is reduced. Convective cloud clusters are identified with a brightness temperature threshold, and we find realistic numbers of the largest clusters (>10^4 km sq) at all resolutions, while the number of smaller clusters increases with resolution, approaching observations when dx=3 km. The observed diurnal cycle in the cluster size distribution is also reproduced, with realistic magnitude in the highest resolution runs. Precipitation characteristics across cluster sizes are also examined. The results show the potential for global mesoscale simulations as a community science resource, and we invite collaboration to explore these runs in greater detail.
Document ID
20190029612
Acquisition Source
Goddard Space Flight Center
Document Type
Presentation
Authors
Arnold, Nathan (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Freitas, Saulo
Putman, William (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 26, 2019
Publication Date
July 29, 2019
Subject Category
Earth Resources And Remote Sensing
Report/Patent Number
GSFC-E-DAA-TN71792
Meeting Information
Meeting: Conference on Mesoscale Processes
Location: Savannah, GA
Country: United States
Start Date: July 29, 2019
End Date: August 1, 2019
Sponsors: American Meteorological Society (AMS-HQ)
Distribution Limits
Public
Copyright
Public Use Permitted.
Technical Review
NASA Technical Management

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