Modified K Index — modified_K

The modified K index use logarithmically averaged layer (ln pressure) between the surface and 850 hPa.

Usage

modified_K_Index(
  ta_s,
  hus_s,
  pa_s,
  ta_pl,
  hus_pl,
  pa_pl,
  mod_lev = 850,
  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).
mod_lev: the top level of the logarithmically averaged layer in hPa. Default is 850 hPa. Sometime, 850 hPa is located below the surface in high terrain area. de Coning et.al. (2011) considered 825 hPa for that case.
nthreads: an integer specifying the number of threads to use for computation (OpenMP). Default is 1.

Value

the computed - modified K index (K).

References

Charba, J.P., 1977. Operational system for predicting thunderstorms two to six hours in advance. NOAA Technical Memo. NWS TDL-64. 24 pp. [Techniques Development Laboratory, National Weather Service, Silver Spring, MD.].
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 .
de Coning, E., Koenig, M., & Olivier, J. (2011). The combined instability index: A new very-short range convection forecasting technique for southern Africa. Meteorological Applications, 18(4), 421–439. doi:10.1002/met.234

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 <- modified_K_Index(
  ta_s,
  hus_s,
  pa_s,
  ta,
  hus,
  pa,
  mod_lev = 850
)