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Drought in the Midwest

Drought in the Midwest. by Anthony R. Lupo Department of Soil, Environmental, and Atmospheric Sciences 302 E ABNR Building University of Missouri – Columbia Columbia, MO 65211. Drought in the Midwest. Why is it important to discuss it? Source: NOAA – USDA – Missouri Climate Center.

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Drought in the Midwest

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  1. Drought in the Midwest by Anthony R. Lupo Department of Soil, Environmental, and Atmospheric Sciences 302 E ABNR Building University of Missouri – Columbia Columbia, MO 65211

  2. Drought in the Midwest • Why is it important to discuss it? • Source: NOAA – USDA – Missouri Climate Center

  3. Drought in the Midwest • Anatomy of a warm, dry summer – 2005 • Let’s look at the mid-western drought of 2005 and discern the causes • Spring season (March – May) Avg over mid-MO = 11.6 inches • Actual rain = 7.3 inches, 63% of normal – this was typical across the region.

  4. Drought in the Midwest • It was not particularly warm during the spring, but the lack of precipitation still leaves the ground water supplies low! • A look at the long term record reveals that the current dryness began in Dec. 2004 • In early June 2005, the rains stopped coming ( at least less frequently – which is normal).

  5. Drought in the Midwest • the ground dried out, the temperatures rose, etc… (“drought begets drought”) • A “classical” large-scale ridge (drought pattern) settled over the central USA. • The following map is the mean conditions from 15 June – 10 August average.

  6. Drought in the Midwest

  7. Drought in the Midwest • And what was the assessment?

  8. Drought in the Midwest • Summer 2005 - a year to confound climatologists in the future! • Why? • The summer precipitation across the region was actually above normal!

  9. Drought in the Midwest • Summer precipitation was at 15.3” in mid-Missouri, normal is 11.7 inches. But 10” of this occurred during 14 days in August! • What was the cause? • A rare case of summer blocking!

  10. Drought in the Midwest The jet stream was pushed southward – by 10 August.

  11. Drought in the Midwest • By August 13, rains were falling across the midwest.

  12. Drought in the Midwest • Q: What is blocking? • A: It is a large-scale, persistent, nearly stationary, mid-latitude, dynamically driven ridging in the jet-stream. • The dynamics of blocking are not completely understood, even though the climatological behavior is well-understood (see Lupo and Smith, 1995a,b, Tellus; Weidenmann et al.m 2002, J. Climate; Burkhardt and Lupo, 2005, J. of Atms. Sci.)

  13. Drought in the Midwest • Blocking unusual in August, and when they occur in the Alaska region, they force cooler air into North America. • This event was unusual because prolonged blocking usually CAUSES drought, e.g., Europe 2003, or Alaska, 2004!

  14. Drought in the Midwest • Blocking is one of the keys to understanding seasonal variations in the weather, both observed and for predictive purposes. (El Nino is the other, more later) • This is well-known in the climatological community during the winter, but we sometimes forget about summer season blocking.

  15. Drought in the Midwest • Summer, 2004 – a study in contrast (blocking was favorable to the mid-west). • 2005 2004

  16. Drought in the Midwest • Temperatures for Summer 2004 – 3rd coolest summer on record for mid-MO and a “top 5” for most of the mid-west and plains. (Source of picture: Midwest Regional Climate Center)

  17. Drought in the Midwest • June 2004 July 2004 August 2004

  18. Drought in the Midwest • Summer 2004 upper air pattern.

  19. Drought in the Midwest • Summer 2004 versus Summer 2005 (source Missouri Agricultural Statistics service) • 2004 2005

  20. Drought in the Midwest • Soybeans – trend from 1965 – 2005 (source Missouri Agricultural Statistics service)

  21. Drought in the Midwest • The impact of El Nino. • El Nino, what is it? • El Niño –means literally “the child”, in this case, THE Child as El Niño typically sets in around Christmas on the coast of South America!

  22. Drought in the Midwest • El Niño (or ENSO – El Niño and Southern Oscillation) is the generic term referring to the see-saw of warm (El Niño) and cold (La Niña) sea surface temperature patterns in the eastern Tropical Pacific • This occurs every 2 – 7 years!

  23. Drought in the Midwest • El Nino:

  24. Drought in the Midwest • Currently: (ENSO-neutral) (Source: Climate Prediction Center) • Forecasts persist in projecting neutral conditions for the rest of the year and range from weak La Nina to weak El Nino conditions

  25. Drought in the Midwest • Ratley (Ratley, Baxter, Lupo) et al. 2002 discussed the onset of the summer regime in the mid-west and it’s relation to ENSO. • They noticed that before the summer regime becomes “established”, significant rains (widespread and more than 0.25 inches) fall on average every 7 days. • This becomes every 12 days after the onset of the summer pattern.

  26. Drought in the Midwest • They then found that in summers involving the transition into a (future) El Nino situation, the mean precipitation frequency in spring and summer is 6 days and 10 days, respectively. (e.g., summer 1993, summer 2004) • For the transition into a La Nina situation, the corresponding numbers are 8 days, and 19 days, respectively. (e.g., summer 1983, 1988, 1999, 2005, and historically, the severe dry spell of the 1950’s)

  27. Drought in the Midwest • Thus, they found that in the Missouri region, there is not a significant difference region-wide in precipitation amounts year-to-year, but the frequency of heavy precipitation is markedly different. • It is well-known in the agricultural community that lighter, more frequent (regular) precipitation events are much better for crops.

  28. Drought in the Midwest • The results of Ratley et al. (2002) are based on 30 years worth of data. We’re currently working on extending this analysis back to 1900. • Initial results from this extended work (future Birk and Lupo paper) support the results given here.

  29. Drought in the Midwest • What’s in store for 2006?

  30. Drought in the Midwest • Our group predicted a relatively dry and warm summer regionally based on a few factors. • 1) For 11 of the past 18 months have had precipitation amounts below (3) to well-below normal (8), while only two months have been very wet.

  31. Drought in the Midwest • 2) During the late winter, early spring, weak La Nina conditions persisted in the eastern tropical Pacific. At the time, this was expected to persist through the spring and summer. • 3) We’ve noticed that we’re in the dry portion of a long – term cycle. The Missouri Tree Ring Laboratory bolstered our impressions here.

  32. Drought in the Midwest • 4) we’d also projected a drier spring, which did occur. So far, the summer (June) has also been in-line with our predictions. • 5) one piece of information arguing against this forecast is the recent migration of the Pacific region SSTs back to ENSO-neutral from La Nina conditions.

  33. Drought in the Midwest • What is the role of climate and climate change on drought? • Let’s look at the decadal record for the USA. We had drought years in this part of the country during the 1930s, 1950’s, 1980, 1983, 1988, 1999, 2003, 2005 (but wet years in 1993 and 1995).

  34. Drought in the Midwest • Climate of the USA as measured using temperature (source National Assessment)

  35. Drought in the Midwest Borrowed from Karl and Knight (1998), BAMS Borrowed from Hu et al. (1998), BAMS

  36. Drought in the Midwest • Climate change may impact the temporal and/or spatial distribution and severity of drought, however, drought and pluvials (wet spells) will still occur. • Let’s look at a couple centuries…….

  37. Drought in the Midwest • Temperatures (source: IPCC)

  38. Drought in the Midwest • Borrowed from the Missouri Tree-Ring Laboratory • Stambaugh, M.C. and R.P. Guyette. (in prep). 1000 years of tree-ring reconstructed drought in the Central United States.

  39. Paleoecological understanding 1816, Year without summer 16th Century Megadrought Dust Bowl Maunder Minimum Medieval Warm Period Little Ice Age Stambaugh, M.C. and R.P. Guyette. (in prep). 1000 years of tree-ring reconstructed drought in the Central United States.

  40. Drought in the Midwest • Borrowed from Fye et al. (2003), BAMS

  41. Drought in the Midwest • Precipitation in the Northern Plains (Borrowed from Woodhouse and Overpeck, (1998), BAMS

  42. Drought in the Midwest • Studies have shown that the US climate has been getting wetter. • What does the future hold? Model studies have shown our region may be drier (e.g., IPCC), and some studies have shown it may be wetter (e.g. Semenov et al., 2003, Climate Dynamics).

  43. Drought in the Midwest • Many regions of the country give similar mixed results, but since drought and wet spells are seasonal in nature (and driven by SST and atmospheric variations) they will continue to occur regardless of what the climate does!

  44. Drought in the Midwest • Questions? • Comments? • Criticisms? • LupoA@missouri.edu

  45. Drought in the Midwest

  46. Climate, Climate Change & Hurricanes • 2005 (27) versus 1933 (21)

  47. Drought in the Midwest

  48. Drought in the Midwest

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