aiRthermo (version 1.0)

Sindex: Showalter Instability Index

Description

This function computes Showalter instability index (Celsius) from given parameters from a vertical sounding pressure (Pa), temperature (K) and mixing ratio (kg/kg).

Usage

Sindex(Ps, Ts, ws, deltaP, doLog = 0)

Arguments

Ps

A vector with pressure values in Pa

Ts

A vector with temperature values in Kelvin

ws

A vector with mixing ratio values in kg/kg

deltaP

The width (Pa) of the layers used in the numerical solution of the vertical evolution.

doLog

Use logarithmic vertical interpolation between sounding levels. A default value is 0.

Value

This function returns the Showalter instability index (Celsius)

Details

If the needed levels (850 hPa or 500 hPa) are not exactly found in the input sounding, logarithmic/linear vertical interpolation is run to get the corresponding T/w from the Ps/Ts/ws depending on the value of doLog (TRUE or FALSE).

The evolution of the lifted particle is computed by integrating the dT/dP ordinary differential equation (applying the Runge Kutta 4th order method) that represents the vertical adiabatic evolution from 850 hPa to 500 hPa using a pressure step dP > 0 (Pa). The vertical adiabatic evolution is either dry (before saturation) or pseudoadiabatic at every vertical step with a correction for moisture in the specific heat at constant pressure \(c_p\) during the dry steps (as in Tsonis, eq 7.11).

If the sounding does not enclose the needed levels and the interpolation fails, the function returns -99999999

References

Djuric D. (1994). Weather Analysis, Prentice Hall, New Jersey.

See Also

LIindex

Examples

Run this code
# NOT RUN {
data(RadiosondeA)
aPs<-RadiosondeA[,1]*100
aTs<-C2K(RadiosondeA[,3])
aws<-RadiosondeA[,6]/1000
S<-Sindex(aPs,aTs,aws,5,0)
# }

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