982 Pushing LES and GCM Models to Higher Resolutions to Improve Climate Bias of Low Clouds when Compared with Tethered Balloons Measurements and Retrievals over the North Slope of Alaska

Wednesday, 10 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
Erika L. Roesler, Sandia National Laboratories, Albuquerque, NM; and D. Dexheimer, B. R. Hillman, L. Dennis, and M. McChesney

Prevalent clouds located in the first few kilometers of the Arctic atmosphere play an important role in the heating and cooling of the surface below. Global climate models (GCMs), which are used to understand the climate of the Earth, have a negative bias of these low clouds when compared to observations. To understand this negative low cloud bias as a function of model configuration, we have simulated the Arctic atmosphere with three different models and found spatial resolution to affect the simulated low cloud amount. The resolutions tested with an Atmospheric General Circulation Model (AGCM) are 2-degree, 1-degree, and a variable resolution. The resolutions tested with a Large Eddy Simulation, the System for Atmospheric Modeling (SAM), are 50 m, 100 m, 250 m, 500 m, 1000 m, and 5000 m. The resolutions tested with an embedded Cloud Resolving Model in the AGCM are 1-degree and 2-degree. The next stages of our work are focused on understanding these differences between the configurations and resolutions. The simulated cloud is compared with in situ measurements taken with sensors such as the supercooled liquid water content sensor and sondes strung on a tethered balloon system which was deployed at Oliktok Point on the North Slope of Alaska periodically starting in 2015. We have found the in-situ cloud data acquired from eight field campaigns over the past two years represent a variety of meteorological conditions and cloud regimes, exposing the inter-annual variability of the environment. This has given us insight into the uncertainties of the sensors and bias of the atmospheric models in different atmospheric states. These multi-year datasets are also valuable beginnings to understanding Arctic low cloud climatology. These measurements are used to constrain the simulations. The modeled cloud amounts from the GCMs are also compared with multi-year satellite measurements, which again have shown us that the negative bias of the low clouds can be reduced through alternative model configurations. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2017-7982 A
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