Drought in the Midwest

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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

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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

• Anatomy of a warm, dry summer 2005
• Lets 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.

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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).

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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.

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Drought in the Midwest
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Drought in the Midwest

• And what was the assessment?

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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!

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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!

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Drought in the Midwest

• The jet stream was pushed southward by 10
  August.

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Drought in the Midwest

• By August 13, rains were falling across the
  midwest.

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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.)

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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!

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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.

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Drought in the Midwest

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

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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)

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Drought in the Midwest

• June 2004 July 2004 August 2004

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Drought in the Midwest

• Summer 2004 upper air pattern.

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Drought in the Midwest

• Summer 2004 versus Summer 2005 (source Missouri
  Agricultural Statistics service)
• 2004 2005

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Drought in the Midwest

• Soybeans trend from 1965 2005 (source
  Missouri Agricultural Statistics service)

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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!

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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!

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Drought in the Midwest

• El Nino

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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

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Drought in the Midwest

• Ratley (Ratley, Baxter, Lupo) et al. 2002
  discussed the onset of the summer regime in the
  mid-west and its 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.

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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 1950s)

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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.

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Drought in the Midwest

• The results of Ratley et al. (2002) are based on
  30 years worth of data. Were 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.

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Drought in the Midwest

• Whats in store for 2006?

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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.

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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) Weve noticed that were in the dry portion of
  a long term cycle. The Missouri Tree Ring
  Laboratory bolstered our impressions here.

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Drought in the Midwest

• 4) wed 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.

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Drought in the Midwest

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

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Drought in the Midwest

• Climate of the USA as measured using temperature
  (source National Assessment)

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Drought in the Midwest
Borrowed from Karl and Knight (1998), BAMS
Borrowed from Hu et al. (1998), BAMS
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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.
• Lets look at a couple centuries.

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Drought in the Midwest

• Temperatures (source IPCC)

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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.

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

• Borrowed from Fye et al. (2003), BAMS

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Drought in the Midwest

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

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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).

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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!

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Drought in the Midwest

• Questions?
• Comments?
• Criticisms?
• LupoA_at_missouri.edu

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Drought in the Midwest
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Climate, Climate Change Hurricanes

• 2005 (27) versus 1933 (21)

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Drought in the Midwest
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Drought in the Midwest