Modeled Effects of Moderate and Strong Los Nios on North American Crop Productivity and on U'S' Wate

1
Modeled Effects of Moderate and Strong Los Niños
on North American Crop Productivity and on U.S.
Water Resources

• R. César Izaurralde, Norman J. Rosenberg, and
  Allison M. Thomson
• Joint Global Change Research Institute (JGCRI)
• Center for Research on the Changing Earth System
  (CRCES)
• The CRCES Workshop on Societal Impacts of Decadal
  Climate Variability in the United States
• The Hilton Waikoloa Village, Waikoloa, Hawaii
• 26 - 28 April 2007

2
Objectives

• To describe modeling methodologies used in study
  of the impacts of climatic variability on
• Agricultural productivity in North America
• Izaurralde et al. (1999) Agric. Forest Meteor.
  94259-268.
• Water resources in the U.S.
• Thomson et al. (2003) J. Am. Water Resources
  Assoc. 39137-148.
• To analyze the extent to which these
  methodologies can be extended for the study
  decadal climatic variability impacts on natural
  resources

3
Background

• ENSO, the El Niño Southern Oscillation, is an
  interannual ocean-atmosphere phenomenon with
  profound impacts on agriculture, water resources,
  energy production, and economic activity
• The strong El Niño of 1997 - 1998 was significant
  for its
• Strength, which rivaled that of 1982 - 1983
• Successfully forecast
• The methodology reported herein was developed
  with support from NASA and NOAA
• The methodology is based on
• A quantitative understanding of ENSO
• The development and application of ENSO scenarios
  and modeling technologies

4
Classification of ENSO years

• Used Japan Meteorological Agency (JMA) ENSO Index
  to classify each ENSO year (1 October - 30
  September) according to sea surface temperature
  (SST) anomalies
• The JMA Index defines El Niño events based on the
  SST in the region bounded by 4 ºN to 4 ºS
  latitude and 150 ºW to 90 ºW longitude
• ENSO phases are identified based on the 5-month
  running average of SST anomalies
• Neutral ? 0.0 ºC but ? 0.5 ºC
• El Niño ? 0.5 ºC
• La Niña (or El Viejo) ? 0.5 ºC
• Also identified
• Strong El Niño ? 2.0 ºC

5
ENSO scenarios and modeling of agricultural yields

• 30-year weather records of temperature and
  precipitation were used to build ENSO scenarios
• Neutral 15 years
• El Niño 6 years
• Strong El Niño 2
• La Niña (El Viejo) 7
• EPIC, a process-based model built to describe
  climate-soil-management interactions at point or
  small watershed scales
• Key processes simulated in EPIC
• Weather, hydrology
• Plant growth,
• Soil temperature and heat flow
• Carbon, Nitrogen, and Phosphorus cycling
• Tillage, fertilization, irrigation, pesticides
• EPIC was used to model yields of wheat, corn, and
  beans on 140 representative farms in Canada, the
  U.S., and Mexico

Operations
Erosion
Pesticide fate
Representative EPIC modules
Williams (1995) Izaurralde et al. (2006)
6
EPIC-simulated yields vs. historical-district
yields at locations in Canada, the U.S., and
Mexico
Izaurralde et al. (1999)
7
Geographic distribution of temperature and
precipitation anomalies under El Niño (EN) and
strong El Niño (SEN)
Izaurralde et al. (1999)
8
Geographic distribution of corn and wheat yields
under El Niño (EN) and strong El Niño (SEN)
Izaurralde et al. (1999)
9
ENSO scenarios and modeling for water resources

• ENSO scenarios were modeled as explained before
• HUMUS (Hydrological Unit Module for the U.S.) is
  a GIS-modeling system to drive SWAT (Soil Water
  Assessment Tool) (Arnold et al., 2003) at the
  sub-basin scale and aggregate the output into
  larger basins
• Climate and soil type are treated as uniform
  within each 8-digit basin (2101 total)
• Results are aggregated to the scale of the 18
  2-digit Major Water Resource Regions (MWRR)

Major Water Resource Regions
10
Comparison of HUMUS simulated and USGS estimated
annual water yields in the 18 Major Water
Resource Regions of the U.S.
Rosenberg et al. (2003)
11
Seasonal water yield (WY, mm) change from Neutral
under El Niño
Thomson et al. (2003)
12
Seasonal water yield (WY, mm) change from Neutral
under strong El Niño
Thomson et al. (2003)
13
Seasonal water yield (WY, mm) change from Neutral
under La Niña
Thomson et al. (2003)
14
Summary for ENSO impacts on agricultural yields

• Using daily weather records, EPIC accounted for
  87 of the total variation in historical yields
  in a sample of the farms studied
• Yields simulated in EPIC with a stochastic
  weather generator predicted different geographic
  distributions of winner' and loser' regions for
  corn and wheat during EN and SEN years
• Changes in water stress during EN and SEN with
  respect to N years was the variable that
  accounted for a significant proportion in the
  variation of simulated yield changes
• Yields simulated under SEN tended to be more
  variable than under EN
• Further development of the methodology could
  contribute to the near real-time simulation and
  evaluation of El Niño events
• Application of this type of methodology at a
  regional level could improve our understanding of
  the impacts of interannual climatic variability
  on agricultural production

15
Summary for ENSO impacts on water resources

• La Niña conditions increase water yield across
  much of the country
• Water yield increases during El Niño years across
  the southern U.S. while declining in much of the
  rest of the country
• Under strong El Niño conditions, regional water
  yields are much higher than Neutral, especially
  along the West Coast
• The strong El Niño is not simply an amplification
  of El Niño it leads to strikingly different
  patterns of water resource response

16
Concluding thoughts

• ENSO is one manifestation of climatic variability
  but its return period (2 to 7 years) makes it
  different from the PDO, NAO, etc. that are truly
  decadal in nature
• The approach presented here is certainly
  applicable to the study of decadal climatic
  variability impacts on agricultural productivity
  and water resources