The Climatology of the Haines Index as Viewed from the North American Regional Reanalysis

1. The Climatology of the Haines Index as Viewed from the North American Regional Reanalysis W. Lu1, J. Charney2, X. Bian2, W. Heilman2 and S. Zhong1, 1Department of Geography, Michigan State University, East Lansing, MI 2USDA Forest Service, Northern Research Station, East Lansing, MI

2. Haines Index(HI) is calculated by combining a lower-atmospheric stability term (A) and a moisture term (B) into a single number that correlates with erratic fire behavior. HI = A + B Haines DA (1988)

3. To account for differences in surface elevation, specific pressure levels are chosen for the low-, mid- and high-elevation variants of the HI. Werth J, Werth P (1998)

5. 28-year HI climatology • 1980-2007 • May to October • 00UTC • Humidity and temperature field from North American Regional Reanalysis (NARR)

6. The greatest spatial variability in Factor A occurs in the western half of the North America. Considerably higher values of the moisture term occur along the front range of the Rockies and in the desert southwest.

7. Mean and standard deviation of HI The HI exhibits more variability and generally higher values in the western United States due to high surface elevations and generally less stable and drier climate.

8. HI frequency and the maximum consecutive number of days above certain thresholds HI≥ 4

9. HI≥ 5

10. HI≥ 6

11. Interannual variation and linear trend of the number of days with HI≥ 4, HI≥ 5, and HI=6 in six climate regions across the United States • Pacific Northwest • Pacific Southwest • Intermountain West • Midwest • Northeast • Southeast a e c d b f

12. The number of days with high HI in the Pacific Northwest and the Pacific Southwest remains virtually constant .

13. Midwest, Intermountain West, Northeast and Southeast all exhibit increases in high HI days in the past 28 years.

14. Conclusion • The NARR climate dataset yields a higher-resolution, spatially complete analysis of the climatological variations of the warm season Haines Index than has previously been available.

15. Analysis of the spatial and temporal variability of the Haines Index enables operational users of the index as well as researchers to decide how best to apply local and regional Haines Index calculation for their needs.

16. This climatology reveals regional and continental trends in the Haines Index that can help provide important input into fire decision-making and future fire-weather research.