Role of Antecedent Land Surface Conditions on North American Monsoon Rainfall Variability

1. Role of Antecedent Land Surface Conditions on North American Monsoon Rainfall Variability Chunmei Zhu Department of Civil and Environmental Engineering University of Washington Sep, 2005

2. North American Monsoon System (NAMS) North American monsoon is experienced as a pronounced increase in rainfall from extremely dry May to rainy June. North American Monsoon Experiment (NAME): Tier 1,2,3. (http://www.cpc.ncep.noaa.gov/products/precip/monsoon/NAME.html) ( Comrie & Glenn, 1998 )

3. The NAMS concept --- thermal contrast between land and adjacent oceanic regions The importance to explore possible links between NAMS and antecedent surface conditions. ( http://www.ifm.uni-kiel.de )

4. Study Domain Monsoon North Monsoon West Monsoon South Monsoon East Monsoon regions are defined as in Comrie & Glenn (1998)

5. Monsoon West

6. JFM PI 15-year Moving Average Correlation of PI versus MW JJAS rainfall JFM Precipitation Index (PI) Winter Precipitation – Monsoon Relationship

7. Winter Precipitation - Monsoon Rainfall feedback hypothesis Higher (lower) winter precipitation & spring snowpack More (less) spring & early summer soil moisture Lower (higher) spring & early summer surface temperature Weak (strong) monsoon Higher (lower) winter precipitation and spring snowpack More (less) spring or early summer soil moisture lower (higher) spring and early summer surface temperature Weak (strong) monsoon

8. DRY WET WET DRY Wet Monsoon Dry Monsoon JFM Precipitation in extreme monsoon years Apr-May Soil Moisture in extreme monsoon years

9. Soil moisture anomalies persist from spring until June Correlation of June Sm & JFM PI (1965-1999) Correlation: June Sm & June Ts (No significant relationship in MW ) SW Sm has no significant relationship with Ts

10. Wet Monsoon Dry Monsoon June High Low June Low High Z500 (m) anomalies June Ts anomalies

11. Monsoon South

12. Development of a Long-Term Land Surface Data Set for Mexico SMN daily precipitation, surface air temperature data (pre-1940 – 2003 )produced by SMN (Servicio MeterorolÓgico Nacional), over 5000 stations. SMN daily precipitation data (1995 – near realtime) provided courtesy of Miguel Cortez Vázquez of SMN, around 1,000 stations. NW Mexico NAME Event Raingage Network (NERN) precipitation daily data ( 2002 - )provided courtesy of David Gochis, 86 station cross Sierra Madre Occidental

13. Comparison of simulated and observed streamflow 6 1 7 12 2 3 8 13 11 15 4 9 14 5 10 The streamflow dataset is the Mexico acronym BANDAS (CNA and IMTA).

14. Study Domain The Monsoon South domain is divided into 2 sub-regions (Higgins et al 1998, Hu & Song 2002, Englehart and Douglas, 2001) The long-term mean monthly precipitation 1950-1999 MSb MSa

15. Standardized JJAS Rainfall Monsoon onset date anomaly Wet years Early years 1958 1966 1984 1986 1990 1972 1976 1977 1984 1996 Dry years Late years 1951 1969 1973 1979 1987 1995 1953 1957 1979 1989 1992 ? monsoon magnitude or onset

16. Winter Precipitation - Monsoon Rainfall feedback hypothesis From previous study on Southwestern US, we propose a similar … Higher (lower) winter precipitation & spring snowpack More (less) spring & early summer soil moisture Lower (higher) spring & early summer surface temperature Weak (strong) monsoon

17. Winter Precipitation – Monsoon Onset 15-year Moving Average Correlation of PI versus monsoon onset Correlation of JFM Precip and Monsoon Onset Date

18. Winter Snow – Monsoon Onset 15-year Moving Average Correlation of JFM SWE index versus monsoon onset The snow – monsoon onset relationship is only significant from 1960 to 1980

19. Early Late JFM Precipitation in extreme monsoon years Late Early May Soil moisture in extreme monsoon years

20. Winter precipitation – May soil moisture Correlation of JFM Precip and May total column soil moisture Correlation of JFM Precip and May first layer soil moisture

21. Late Early Late Early May Sm in extreme monsoon years May Ts in extreme monsoon years

22. Correlation: May first layer Sm & May Ts Correlation: May Ts & monsoon onset May soil moisture plays some role in pre-monsoon seasonal surface thermal condition

23. Land – sea thermal contrast Late - early Late Early

24. Late Early Atmospheric Circulation effect? May Ts anomalies May Ts – Z500 correlation May Z500 anomalies

25. Feedback to monsoon magnitude Correlation: May first layer Sm & May Ts Correlation: May Ts & monsoon magnitude

26. Summary ● MW monsoon is negatively related with Southwest winter precipitation. NW Mexico summer monsoon onset date is positively related with Southwest winter precipitation and snow especially for extreme late and early years. ● Spring soil wetness conditions in the SW U.S. and northwestern Mexico are strongly determined by the previous winter’s precipitation, this land memory appears to play some role in the surface thermal condition, then influence the NW Mexico monsoon onset, but seems to contribute little to MW summer monsoon. ● May Z500 anomalies shows strong relationship with May Ts anomaly all over the North America continent, which suggesting that the atmospheric circulation condition may contribute more to the pre-monsoon Ts anomalies than land surface conditions.