Summertime Rainfall Events in Eastern Oregon and Washington
Abstract
Wildfire hazard in the Pacific Northwest depends strongly on the fuel moisture level. Occasional moderate to heavy rainfall events during early summer can effectively postpone the onset of the fire season locally; late summer events can end it. With the support of the US Forest Service, the character of these events is being diagnosed, with a focus on their climatology and associated atmospheric circulation patterns. The Daily US Unified Precipitation data set from NOAA’s Climate Prediction Center is the primary means through which precipitation events are identified. This data set provides daily values of precipitation based on station data on a grid with a spacing of 0.25 degree from 1948 through 2008, but this source of information is compromised by the small-scale variations associated with the complex terrain. For that reason, daily values of streamflow from the US Geological Service for selected rivers are also considered. The statistics of events for various thresholds have been assembled. These events are associated with four basic types of atmospheric circulation patterns. The most common pattern features westerly flow aloft and yields widespread precipitation. The second most frequent synoptic situation includes southeasterly flow in a more convective environment. This project is ongoing, and will eventually involve an examination of how global climate change is liable to influence the occurrence of atmospheric circulation patterns favoring precipitation east of the Cascade Mountains during summer.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A13D0241B
- Keywords:
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- 3329 ATMOSPHERIC PROCESSES / Mesoscale meteorology;
- 3354 ATMOSPHERIC PROCESSES / Precipitation