Surface Lifted Index (LI)

Usage

Lifted_index_sfc(ta_s, hus_s, pa_s, ta500, nthreads = 1)

Arguments

ta_s: Parcel temperature [lon, lat, time] at 2 meter above the surface (K).
hus_s: Parcel specific humidity [lon, lat, time] at 2 meter above the surface (kg/kg).
pa_s: Surface pressure [lon, lat, time] (hPa).
ta500: air temperature [lon, lat, time] at 500 hPa (K).
nthreads: an integer specifying the number of threads to use for computation (OpenMP). Default is 1.

Value

The surface lifted index [lon, lat, time] (k).

Details

The Lifted Index (LI) is calculated by lifting a surface parcel pseudo-adiabatically to 500 hPa and comparing its temperature to the environmental temperature at that level.

References

Galway, J.G., 1956. The lifted index as a predictor of latent instability. Bull. Am. Meteorol. Soc. 37, 528–529.
Haklander, A. J., & Van Delden, A. (2003). Thunderstorm predictors and their forecast skill for the Netherlands. Atmospheric Research, 67–68, 273–299. doi:10.1016/S0169-8095(03)00056-5 .

Examples

data("ERA5_sfc")
ta_s <- ERA5_sfc$t2m
td_s <- ERA5_sfc$t2d
pa_s <- ERA5_sfc$sp / 100
hus_s <- hus_from_td(td_s, pa_s)
dim(hus_s) <- dim(ta_s)

data("ERA5_pl")
ta <- ERA5_pl$ta
#' convert to hPa
pa <- ERA5_pl$plev / 100
l500 <- which(pa == 500)
res <- Lifted_index_sfc(
  ta_s,
  hus_s,
  pa_s,
  ta[, , l500, ]
)