Trends in Intense Precipitation in the Climate Record

Trends in Intense Precipitation in the Climate Record

13 April 2004, in final form 15 October 2004 | PAVEL YA. GROISMAN, RICHARD W. KNIGHT, DAVID R. EASTERLING, THOMAS R. KARL, GABRIELE C. HEGERL, VYACHESLAV N. RAZUVAEV
The paper presents an overview of changes in intense precipitation, defined as the frequency of very heavy precipitation or the upper 0.3% of daily precipitation events, over more than half of the global land area. The analysis is based on instrumental observations and model projections from transient climate simulations with increasing greenhouse gas concentrations. The findings indicate an increasing probability of intense precipitation events in many extratropical regions, including the United States. While the impact of more frequent heavy precipitation events can be disruptive, the thresholds for these events are not very high, making the changes relatively manageable. However, reliable assertions of very heavy and extreme precipitation changes are only possible for regions with dense networks due to the small radius of correlation for many intense precipitation events. The study uses a regional averaging technique to analyze the frequency and amount of intense precipitation, considering the spatial distribution of stations and the representativeness of the area-averaged time series. The analysis covers several regions, including the European part of the former USSR, Northern Europe, the Pacific coast of northwestern North America, southeastern and southwestern Australia, South Africa, eastern Brazil and Uruguay, central United States, and central Mexico. The results show significant increases in the frequency of very heavy precipitation in many regions, particularly in the last three decades. Model projections from global climate models also indicate an increase in intense precipitation with global warming, consistent with observed trends. However, the spatial patterns of changes in annual precipitation are model-dependent, while the patterns of heavy and very heavy precipitation changes show more similarity between models. The study highlights the importance of dense networks for reliable estimates of intense precipitation changes and the need for further research to understand the physical mechanisms behind these trends.The paper presents an overview of changes in intense precipitation, defined as the frequency of very heavy precipitation or the upper 0.3% of daily precipitation events, over more than half of the global land area. The analysis is based on instrumental observations and model projections from transient climate simulations with increasing greenhouse gas concentrations. The findings indicate an increasing probability of intense precipitation events in many extratropical regions, including the United States. While the impact of more frequent heavy precipitation events can be disruptive, the thresholds for these events are not very high, making the changes relatively manageable. However, reliable assertions of very heavy and extreme precipitation changes are only possible for regions with dense networks due to the small radius of correlation for many intense precipitation events. The study uses a regional averaging technique to analyze the frequency and amount of intense precipitation, considering the spatial distribution of stations and the representativeness of the area-averaged time series. The analysis covers several regions, including the European part of the former USSR, Northern Europe, the Pacific coast of northwestern North America, southeastern and southwestern Australia, South Africa, eastern Brazil and Uruguay, central United States, and central Mexico. The results show significant increases in the frequency of very heavy precipitation in many regions, particularly in the last three decades. Model projections from global climate models also indicate an increase in intense precipitation with global warming, consistent with observed trends. However, the spatial patterns of changes in annual precipitation are model-dependent, while the patterns of heavy and very heavy precipitation changes show more similarity between models. The study highlights the importance of dense networks for reliable estimates of intense precipitation changes and the need for further research to understand the physical mechanisms behind these trends.
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