Climate Change in the Yaqui Valley David Battisti University of Washington

1. Climate Change in the Yaqui ValleyDavid BattistiUniversity of Washington • Climatological Annual Cycle • Winter vs. Summer • Variability(Winter) • ENSO and Extreme Events • Trends and Climate Change • (wheat yield and climate) • Puzzles

2. 1. The Annual Cycle • Summer • Tropical storms, hurricane debris, (monsoon) • Winter • El Nino/Southern Oscillation (ENSO) • Pacific North American Pattern • More

3. 2. Interannual Variability Precipitation Anomalies • Winter • El Nino/Southern Oscillation (ENSO) • Pacific North American Pattern • More • Summer • Not today • Extreme Events • Extended Drought (Lobell 2003)

4. Temperature Anomalies ENSO • ENSO warms offshore and cools to the east in the Sierra. • ENSO brings winter rainfall to the Yaqui Valley catchment basin (r = 0.55) Precipitation Anomalies (January-April)

5. Precipitaiton Anomalies (January-April) The Pacific North American (PNA) Pattern • The (+) PNA brings winter rainfall to the Yaqui Valley catchment basin (r=.6). • The (+) PNA warms offshore and cools to the east in the Sierra. • Yaqui Valley is on a nodal line for PNA -- no signal. Temperature Anomalies (January-April)

6. Temperature Anomalies (January-April) The West Pacific (WP) Pattern • The mechanisms for the year-to-year variability in this ‘new’ pattern of natural variability are not known. • The WP pattern does bring seasonal temperature and precipitation anomalies to the Yaqui Valley (warm/dry, cold/wet). Precipitation Anomalies (January-April)

7. The West Pacific (WP) Pattern (cont) Temperature Anomalies (January-April) • The WP pattern does bring seasonal temperature and precipitation anomalies to the Yaqui Valley (warm/dry, cold/wet; r=0.5/0.7). • The WP pattern is only weakly correlated to SST in the eastern Pacific.

8. Extreme Drought • The instrument record of Yaqui Valley basin precipitation has been extended using tree ring data. • Correlation of observed and reconstructed Nov-April rainfall is 0.77. Precipitation Anomalies (Nov-April) (Diaz et al. 2002)

9. Extreme Drought • The reconstructed precipitation record extends from 1650 to 1985 AD. • The average return time for a drought similar to the present drought is about 20 years. • Correlation of observed and reconstructed Jan-April rainfall is 0.77. Precipitation Anomalies (November-April)

10. 3. Trends and Climate Change • Annual wheat yield in Yaqui Valley (1983-2002) is highly correlated to the Jan-April average minimum daily temperature. • Is this due to climate or management? • Note: much of the relationship between minimum temperature and yield is interannual (r =0.7) Yield Temp (Lobell et al. 2003)

11. Temperature Anomalies Yield and Climate • Increased yield is related to • Less precipitation (r = 0.8!) • Reduced minimum temperatures • Cold SST immediately offshore • Warm SST in the western Pacific • The PNA and the WP are weakly related to yield (r=-.31 and .42, respectively) Precipitation Anomalies (January-April)

12. 4. Conclusions • Much of the variability in wintertime precipitation in the Yaqui Vally catchment is due to patterns of natural climate variability: ENSO, the PNA and the WP phenomenon. • The local ocean SST conditions are probably not influencing Tmin: • ENSO, remotely forced atmospheric teleconnections (WP) and variability intrinsic to the atmosphere (PNA) are likely to be responsible. • Some of the relationship between yield and climate could be explained by the collection of natural patterns of interannual variability: • The PNA and the WP are weakly related to yield (r =-.31 and .42, respectively) • Another Pattern is worth checking: the North Pacific pattern.

13. 4. Conclusions Warm Pool(WP) Index • The trend (20 year) in yield and minimum temperature are correlated with the 40 year (warming) trend in the western Pacific (WP). • The latter has been argued in several studies to be due to increasing greenhouse gas concentrations (e.g., Hoerling et al. 2003)

14. 4. Conclusions and Puzzles • Problems: If the variability and trend in wheat yield are due to the natural variability in the PNA and WP (and the trend in WP), …. How do drier conditions (r=.7) lead to lower minimum daily temperatures? Does clearing lead to a greater diurnal temperature range, and hence a lower minimum daily temperature, even though the daily mean temperature might be rising? • Summer vs. winter precipitation and reservoir levels

15. ENSO Forecast Forecast Made Sept 2003 Operational forecasts of ENSO from the Univ. of Washington Skill: Forecasts from April Skill: Forecasts for August

16. Summer Precipitation 2003

20. North American Monsoon Experiment

21. Detail of WP and Mexico Temperature

22. 4. Conclusions and Puzzles • Problems: If the variability and trend in wheat yield are due to the natural variability in the PNA and WP (and the trend in WP), …. • How do drier conditions (r=.7) lead to lower minimum daily temperatures? Does clearing lead to a greater diurnal temperature range, and hence a lower minimum daily temperature, even though the daily mean temperature might be rising?