P2.31
Global trends (1979 to 2001) in mean and extreme rainfall from a new satellite-gauge merged data set
Scott Curtis, JCET/Univ. of Maryland Baltimore County, Greenbelt, MD; and R. F. Adler, G. J. Huffman, E. J. Nelkin, and D. T. Bolvin
The latest report (2001) of Working Group I to the International Panel on Climate Change (IPCC) states that it is very likely that precipitation has increased 0.5 to 1.0 percent over mid- to high-latitude land areas during the last century. The working group is less confident about a smaller increase in rainfall over tropical land areas, which is not evident in the past few decades. Furthermore, there is insufficient data to assess a trend over the vast oceans. The record of satellite observations, albeit short, is an important contribution to the debate on global warming and its affect on the global hydrologic cycle, especially since it includes rainfall estimates over open ocean. One primary focus of NASA's Earth Science Enterprise over the next ten years is to address the question: How are global precipitation, evaporation, and the cycling of water changing? One possible response to global warming would be an acceleration of the hydrologic cycle. Another response would be a trend towards more intense rainfall events. Data over the United States lends evidence to the latter hypothesis. In this presentation we will address recent changes in the means and extremes of rainfall over the globe using the latest monthly Global Precipitation Climatology Project (GPCP) data set, which covers 1979 to near present. Over the tropics we will show that the trend over the past few decades may be explained by an increase in strong El Niņo and La Niņa events. However, the global integrated precipitation rate shows no trend. Other regional trends will be explored. Finding trends in extreme rainfall events (wet or dry) is somewhat of a challenge. The variance in oceanic rainfall increases substantially with the inclusion of the SSM/I passive microwave data in 1986. An adjustment procedure will be offered and global trends of extreme events will be analyzed.
Poster Session 2, Climatology and Long-term Satellite Studies
Monday, 15 October 2001, 2:15 PM-4:00 PM
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