Table 1: Squared correlation between indices of frost timing, temperature and circulation, with bold indicating statistical significance and asterisk indicating negative correlation.

From: Observed variations in U.S. frost timing linked to atmospheric circulation patterns

 Spring (March–May)Fall (September–November)
 NorthCentralSouthWestNorthCentralSouthWest
 SNaSCbSScSWdFNeFCfFSgFWh
THi0.16*(0.10)0.14*(0.06)0.09*(0.04)0.08*(0.05)0.27(0.02)0.01(0.00)0.05(0.00)0.17(0.01)
TRj0.06*(0.02)0.06*(0.02)0.27*(0.01)0.44*(0.00)0.16(0.04)0.16(0.03)0.20(0.02)0.26(0.03)
Cxxk0.320.260.380.480.410.250.380.29
 CSNlCSCmCSSnCSWoCFNpCFCqCFSrCFWs
THi0.06*0.11*0.06*0.03*0.400.050.100.37
TRj0.42*0.51*0.55*0.84*0.150.270.310.44
PNAIt0.030.020.190.55*0.21*0.03*0.59*0.18
  1. Numbers in parentheses indicate the fraction of residual frost index variance accounted for by the temperature index after the effect of Cxx was linearly removed.
  2. aDay of year with last spring frost in the North region.
  3. bDay of year with last spring frost in the Central region.
  4. cDay of year with last spring frost in the South region.
  5. dDay of year with last spring frost in the West region.
  6. eDay of year with first fall frost in the North region.
  7. fDay of year with first fall frost in the Central region.
  8. gDay of year with first fall frost in the South region.
  9. hDay of year with first fall frost in the West region.
  10. iNorthern Hemisphere annual mean temperature.
  11. jRegional mean temperature for spring or fall according to column heading.
  12. kCirculation index corresponding to frost timing index in the column heading, meaning CSN for SN, CSC for SC and so on.
  13. lCirculation pattern corresponding to SN.
  14. mCirculation pattern corresponding to SC.
  15. nCirculation pattern corresponding to SS.
  16. oCirculation pattern corresponding to SW.
  17. pCirculation pattern corresponding to FN.
  18. qCirculation pattern corresponding to FC.
  19. rCirculation pattern corresponding to FS.
  20. sCirculation pattern corresponding to FW.
  21. tPacific-North American Pattern Index.