Most Unstable Lifted Index (LI) after Haklander & Van Delden

Usage

Lifted_index_mu(
  ta_s,
  hus_s,
  pa_s,
  ta_pl,
  hus_pl,
  pa_pl,
  dp = 250,
  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).
ta_pl: air temperature [lon, lat, lev, time] on pressure level (K).
hus_pl: specific humidity [lon, lat, lev, time] on pressure level (kg/kg).
pa_pl: pressure profile [lev] in descending manner (hPa).
dp: Thickness of the layer considered above the surface (hPa). Default is 250 hPa.
nthreads: an integer specifying the number of threads to use for computation (OpenMP). Default is 1.

Value

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

Details

The Lifted Index (LI) is calculated by lifting the most unstable parcel pseudo-adiabatically to 500 hPa and comparing its temperature to the environmental temperature at that level. The most unstable parcel is the parcel with the highest equivalent potential temperature in the layer 250 hPa above the surface.

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$ta
hus <- ERA5_pl$hus
# convert to hPa
pa <- ERA5_pl$plev / 100
res <- Lifted_index_mu(ta_s,
  hus_s,
  pa_s,
  ta,
  hus,
  pa,
  dp = 250
)