U.S. Department of Energy Office of Biological and Environmental Research

BER Research Highlights

Small Ice Crystals in High-altitude Clouds Do Impact Global Circulations
Published: May 04, 2009
Posted: May 11, 2009

Scientists in DOE's Atmospheric Radiation Measurement (ARM) Program used a global climate model and found that moderate changes in the concentration of small ice crystals in high-altitude clouds, known as Cirrus clouds, had a large impact on the predicted climate.  Using ARM measurements, new mathematical descriptions of ice particle sizes and concentrations, falling speeds, and radiative properties of cirrus clouds were incorporated into a community global climate model.  Moderate increases in small ice crystal concentrations produced lower fall speeds, more cirrus cloud coverage (a 5.5% global increase) and ice content, and warmer atmosphere temperatures (over 3° C) at high altitudes.  In the tropical regions these changes had an overall cooling effect, but a warming effect elsewhere.  Since the present methods to measure concentrations of small ice crystals in cirrus clouds have a high degree of uncertainty, these modeling results underscore the need to improve measurements for better quantification of climate change prediction.

Reference: Mitchell, D.L., P.J. Rasch, D. Ivanova, G.M. McFarquhar, T. Nousiainen (2008), Impact of small ice crystal assumptions on ice sedimentation rates in cirrus clouds and GCM simulations.  Geophys. Res. Lett., 35, L09806, doi:10.1029/2008GL033552 

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

  • Research Area: Earth and Environmental Systems Modeling
  • Research Area: Atmospheric System Research

Division: SC-23.1 Climate and Environmental Sciences Division, BER


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