Office of Biological and Environmental Research Weekly Report

January 26, 2009

First Ever Long-Term Aircraft Measurements of Clouds. A long-term, aerial field campaign to sample low-altitude, liquid-water clouds will begin January 23 at the Southern Great Plains Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) in Oklahoma. Different from the typical short duration aircraft campaigns, the campaign will run for six months to obtain, for the first time, representative in situ statistics of cloud properties and their seasonal variations, information needed for model improvements. The campaign will obtain representative statistics of the physical and radiative properties of low-level, liquid-water clouds to address aerosol-cloud interactions and improve cloud simulations in climate models. Currently there are large discrepancies in the radiative responses simulated by models in regions dominated by low-level cloud cover, and large areas of the globe are covered by these regions. Further, the properties of thin, low-level clouds are very sensitive to changes in aerosol loading and the aerosol effect on the reflectivity of clouds is a dominant uncertainty in radiative forcing.

Media Interest: No

Contact: Rickey Petty and Wanda Ferrell, SC-23.1, (301) 903-5548 and (301) 903-3281

Roles of Fair-Weather Clouds on Climate Variability. White, puffy cumulus clouds that look like pieces of floating cotton are called fair-weather clouds. Scientists in DOE’s Atmospheric Radiation Measurement (ARM) Program are improving the understanding of fair-weather cloud properties that affect climate change. Fair-weather clouds form over large areas of continents and in trade wind regions over oceans, playing an important role in the Earth’s climate by reflecting the sun’s energy away from the planet. Scientists studied five-years worth of fair-weather cloud data from the ARM Climate Research Facility at the Southern Great Plains site in Oklahoma. The results showed that cloud properties such as cloud-base height, cloud-top height, and cloud cover depend mostly on the time of day and the amount of low-altitude moisture. These findings are helping scientists more accurately characterize and simulate fair-weather clouds in climate models, improving the prediction of climate change and its effects.

Reference:

Berg, L.K., and E.I Kassianov, 2008. Temporal Variability of Fair-Weather Cumulus Statistics at the ACRF SGP Site. Journal of Climate, 21:13: 3344-3358, http://ams.allenpress.com/perlserv/?request=get-document&doi=10.1175%2F2007JCLI2266.1

Media Interest: No

Contact: Kiran Alapaty, SC-23.1, (301) 903-3175