Collaborative Research:  Using SOCRATES Datasets to Improve Simulations of Clouds, Aerosols and their Climate Impacts

GSTDTAP

项目编号	1660538
	Collaborative Research: Using SOCRATES Datasets to Improve Simulations of Clouds, Aerosols and their Climate Impacts
	Stephan Fueglistaler
主持机构	Princeton University
项目开始年	2017
	2017-06-15
项目结束日期	2020-05-31
资助机构	US-NSF
项目类别	Continuing grant
项目经费	77410(USD)
国家	美国
语种	英语
英文摘要	The Southern Ocean (SO), meaning the global ocean of the high latitude Southern Hemisphere, has a well-deserved reputation as the stormiest place on earth. The remoteness of the SO and its unforgiving conditions have severely limited observations of atmospheric processes occurring above it, including cloud processes in the cyclones traveling along the South Polar front. Yet these processes are of interest for a variety of reasons, including the fact that SO clouds are relatively free from the effects of continental and anthropogenic aerosols, and the region is thus a natural laboratory for the study of cloud behavior under pristine conditions. SO clouds also play a significant cooling role in the energy balance of the planet by reflecting incoming sunlight back to space. There is evidence to suggest that this cooling has a long-range effect on the distribution of the low-latitude rainfall associated with the intertropical convergence zone, and that changes in SO cloudiness due to global climate change will affect the location and strength of the Southern Hemisphere jet stream. One indicator of our lack of understanding of SO cloud processes is the inadequate SO cloud cover found in climate model simulations, which is accompanied by excessive absorption of sunlight by the ocean surface which may in turn cause errors in estimates of climate sensitivity. The deficiency in simulated cloud cover is most pronounced in boundary layer and lower-tropospheric clouds (tops below 3km) in the cold, dry sectors of frontal weather systems traveling along the SO storm track. This project is a component of the Southern Ocean Clouds, Radiation, Aerosol, Transport Experimental Study (SOCRATES). The primary activity of the campaign is the deployment of a Gulfstream V (GV) research aircraft maintained by the Earth Observing Laboratory of the National Center for Atmospheric Research. The GV is based in Hobart, Australia and makes multiple flights across the South Polar front collecting data on SO clouds and the meteorological conditions in which they occur. The GV is equipped with dropsondes to record ambient meteorological conditions, radar and lidar to observe the clouds, and instruments mounted on the wings or positioned behind inlets to to sample, collect and analyze aerosols and cloud particles (liquid droplets and ice crystals). The SOCRATES campaign is complementary to SO activities planned internationally and by other US agencies, including surface observations taken on ships and on MacQuarie Island, a small uninhabited island at 54 degrees South. Work supported here uses data collected in the SOCRATES campaign to improve the representation of SO clouds and cloud-aerosol interactions in climate and weather models. Several possible reasons for the cloud deficiencies are addressed, including deficiencies in the representation of cloud microphysics leading to overly rapid freezing of supercooled liquid water (SLW) cloud droplets, excessive precipitation from shallow cumulus clouds, errors in the representation of small-scale turbulent motions and their effects on the distribution of cloud water, and inaccurate representation of aerosols and their role as condensation nuclei for liquid droplets and nucleating particles for cloud ice. Much of the activity in the campaign is focused on the abundance of SLW in SO clouds, which are less glaciated than their Northern Hemisphere counterparts (i.e. they contain more very cold liquid droplets and fewer ice particles), and work in this project uses model simulations to understand this difference. Two categories of models are used, global atmospheric models and large-eddy simulation (LES) models. Global models include the Community Atmosphere Model version 6 (CAM6), developed by and for the research community and hosted at the National Center for Atmospheric Research, and the Atmospheric Model version 4 (AM4), developed by the Geophysical Fluid Dynamics Laboratory. The LES model is the System for Atmospheric Modeling (SAM), developed by researchers at the State University of New York at Stony Brook and the Colorado State University. For the global models, a "nudged meteorology" strategy is used to facilitate comparisons between observations and model simulations. In this strategy the model is subjected to forcing terms which constrain it to remain close wind and temperature values produced by operational weather forecasting centers. The goal is to reproduce the large-scale meteorological conditions in which campaign observations were made, so that the cloud and aerosol observations from the campaign can be reasonably compared to their simulated counterparts. The project uses the understanding developed from these comparisons, and from the LES modeling, to develop a representation for ice nucleating particles in CAM6. The work has broader impacts due to its potential value for improving models used for weather prediction and future climate projections. The work on model improvement also has broader impacts for the scientific research community, as CAM6 and AM4 are widely used tools for scientific research. The nudged meteorology simulations are available for community use as part of the long-term online archive of data collected in the campaign, along with the meteorological analyses used to nudge the models and ancillary cloud and sea surface observations from satellites. In addition to the broader impacts of the work performed, the project provides support and training for two postdocs, thereby providing for the development of the scientific workforce in this research area. The PIs also contribute to campaign outreach activities including a SOCRATES blog.
URL	查看原文
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/71130
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Stephan Fueglistaler.Collaborative Research: Using SOCRATES Datasets to Improve Simulations of Clouds, Aerosols and their Climate Impacts.2017.