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Jefferson Index

Jefferson_Index.Rd

Estimate the original and modified Jefferson Index

Usage

Jefferson_Index(ta, hus, pa, ta500, ta700, hus700, nthreads = 1)

Arguments

ta

air temperature [lon, lat, time] (K).

hus

specific humidity [lon, lat, time] (g/g).

pa

the pressure level at which ta and hus are on (hPa).

ta500

air temperature [lon, lat, time] at 500 hPa (K).

ta700

air temperature [lon, lat, time] at 700 hPa (K).

hus700

specific humidity [lon, lat, time] at 700 hPa (kg/kg).

nthreads

an integer specifying the number of threads to use for computation (OpenMP). Default is 1.

Value

the computed Jefferson Index [lon, lat, time] (°C).

Details

To estimate the original Jefferson index, ta and hus should be on 850 hPa. For the modified version, ta and hus should be on 925 hPa.

References

  • Jefferson, G.J., 1963a. A modified instability index. Meteorol. Mag. 92, 92–96.

  • Jefferson, G.J., 1963b. A further development of the instability index. Meteorol. Mag. 92, 313–316.

  • Jefferson, G.J., 1966. Letter to the editor. Meteorol. Mag. 95, 381–382.

  • VA van Gastel. Investigating MSG-SEVIRI data as an additional predictor source in the KNMI probabilistic (severe) thunderstorm forecasting system KNMI number: IR-2012-01, Year: 2012, Pages: 65

Examples

data("ERA5_pl")
pa <- ERA5_pl$plev / 100 # convert to hPa
hus <- ERA5_pl$hus
ta <- ERA5_pl$ta

l500 <- which(pa == 500)
l700 <- which(pa == 700)
l850 <- which(pa == 850)
res <- Jefferson_Index(ta[, , l850, ],
  hus[, , l850, ],
  pa = 850.0,
  ta[, , l500, ],
  ta[, , l700, ],
  hus[, , l700, ]
)