A contribution by ice nuclei to global warming
- Univ. of Maryland, Baltimore, MD (United States). Goddard Earth Sciences and Technology Center; NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States). Lab. for Atmospheres
- NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States). Lab. for Atmospheres
- Stony Brook Univ., NY (United States). School of Marine and Atmospheric Sciences
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Atmospheric Sciences Division
- National Oceanic and Atmospheric Administration (NOAA), Camp Spring, MD (United States). National Environmental Satellite, Data, and Information Service
Ice nuclei (IN) significantly affect clouds via supercooled droplets, that in turn modulate atmospheric radiation and thus climate change. Since the IN effect is relatively strong in stratiform clouds but weak in convective ones, the overall effect depends on the ratio of stratiform to convective cloud amount. In this paper, 10 years of TRMM (Tropical Rainfall Measuring Mission) satellite data are analyzed to confirm that stratiform precipitation fraction increases with increasing latitude, which implies that the IN effect is stronger at higher latitudes. To quantitatively evaluate the IN effect versus latitude, large-scale forcing data from ten field campaigns are used to drive a CRM (cloud-resolving model) to generate longterm cloud simulations. As revealed in the simulations, the increase in the net downward radiative flux at the TOA (top of the atmosphere) from doubling the current IN concentrations becomes larger at higher latitude, which is attributed to the meridional tendency in the stratiform precipitation fraction. Surface warming from doubling the IN concentrations, based on the radiative balance of the globe, is compared with that from anthropogenic CO2. We found that the former effect is stronger than the latter in middle and high latitudes but not in the Tropics. With regard to the impact of IN on global warming, there are two factors to consider: the radiative effect from increasing the IN concentration and the increase in IN concentration itself. The former relies on cloud ensembles and thus varies mainly with latitude. In contrast, the latter relies on IN sources (e.g., the land surface distribution) and thus varies not only with latitude but also longitude. Global desertification and industrialization provide clues on the geographic variation of the increase in IN concentration since pre-industrial times. Thus, their effect on global warming can be inferred and then be compared with observations. Finally, a general match in geographic and seasonal variations between the inferred and observed warming suggests that IN may have contributed positively to global warming over the past decades, especially in middle and high latitudes.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER); National Aeronautics and Space Administration (NASA)
- DOE Contract Number:
- AC52-07NA27344; AI02-04ER63755; W-7405-Eng-48
- OSTI ID:
- 1253681
- Report Number(s):
- LLNL-JRNL-412332; QJ
- Journal Information:
- Quarterly Journal of the Royal Meteorological Society, Vol. 135, Issue 643; ISSN 0035-9009
- Publisher:
- Royal Meteorological Society
- Country of Publication:
- United States
- Language:
- English
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