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Changes in Precipitation and Drought

Changes in Precipitation and Drought. Current Weather Finish Surface Temperature Large-Scale Precipitation Snowfall Drought For next class: Read IPCC AR4 Ch. 3 (pp. 265-278) on AsUlearn. Solar Update. http://www.youtube.com/watch?v=6j4bl57D_1U. Precipitation Changes.

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Changes in Precipitation and Drought

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  1. Changes in Precipitation and Drought • Current Weather • Finish Surface Temperature • Large-Scale Precipitation • Snowfall • Drought For next class: Read IPCC AR4 Ch. 3 (pp. 265-278) on AsUlearn

  2. Solar Update • http://www.youtube.com/watch?v=6j4bl57D_1U

  3. Precipitation Changes • No statistically significant linear trends in global precipitation from 1900 to 2005, but considerable variability exists. • Numerous challenges in measuring precipitation due to wind effects and accurate measurement of snowfall • Important changes in spatial patterns of precipitation: • Wetter conditions across Amazon Basin and Patagonia in South America • Drier, then wetter across the African Sahel • Change in rainfall patterns may be tied to 1976-1977 Pacific Climate Shift

  4. Latitude-Time Section of Precipitation Anomalies

  5. Boone Winter (DJF) Precipitation, 1950-2008

  6. Changes in Snowfall • Winter precipitation has increased at high latitudes. • Rising temperatures have generally resulted in rain rather than snow in locations and seasons where climatological average (1961-1990) temperatures were close to 0°C. • Large increases in lake-effect snowfall since 1951 for locations near the Great Lakes, consistent with observed decrease in ice cover since the early 1980s.

  7. Drought Terminology • Drought: “prolonged absence or marked deficiency of precipitation” or “a deficiency of precipitation that results in water shortage” or “a period of abnormally dry weather sufficiently prolonged for the lack of precipitation to cause a serious hydrologic imbalance” (Heim 2002 in IPCC AR4). • Agricultural drought relates to moisture deficits in the root zone of the soil that impacts crops. • Meteorological drought is mainly a prolonged deficit of precipitation. • Hydrologic drought is related to below normal streamflow, lake, and groundwater levels. • PDSI (Palmer Drought Severity Index) is most commonly used drought index, using precipitation, temperature, and water content data to assess soil moisture.

  8. Trends in PDSI 1900 to 2002 Red = Drier Blue = Wetter

  9. U.S. Drought Monitor • http://www.drought.unl.edu/dm/monitor.html

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