Showalter Index

[Piotr Djaków]

Dnia 2008-09-19, pią o godzinie 09:01 +0200, Davide Sacchetti pisze:

>    'define epres=exp('k15'-'k1'*t-'k2'/t)*'R'/100'
>    'define pom='k15'-log(epres)'
>    'define dewtemp=(pom-sqrt(pom*pom-'k3'))/'k4
>    'define tcp=dewtemp-(t-dewtemp)*('k5'+'k6'/t+'k7'*t)'
>    'define pcp=lev*pow((tcp/t),('Rd'/'Cp'))'
>    'define ww=epres/(lev-epres)'
>    'define pd=(pcp-'P0'+abs(pcp-'P0'))/(2*abs(pcp-'P0'))'
>    if(pd=1)
>     'define
> showalter=t(lev='P0')-t(lev='level')*pow(('P0'/'level'),('Rd'/'Cp'))'
>    else
>     'define showalter=t(lev='P0')-tcp
> +(pcp-'P0')*('k10'+'k11'*ww-'k12'*ww/tcp-'k13'*pcp)'
>    endif
>

Tell me if i'm wrong:
t is tmp2m, and R is rh2m (%)?
So in GFS GRIB files this calculation may be look like this?:

'define epres=exp('k15'-'k1'*tmp2m-'k2'/tmp2m)*Rh2m/100'
'define pom='k15'-log(epres)'
'define dewtemp=(pom-sqrt(pom*pom-'k3'))/'k4
'define tcp=dewtemp-(tmp2m-dewtemp)*('k5'+'k6'/tmp2m+'k7'*tmp2m)'
'define pcp=lev*pow((tcp/tmp2m),('Rd'/'Cp'))'
'define ww=epres/(lev-epres)'
'define pd=(pcp-'P0'+abs(pcp-'P0'))/(2*abs(pcp-'P0'))'
if(pd=1)
'define
showalter=tmpprs(lev='P0')-tmpprs(lev='level')*pow(('P0'/'level'),('Rd'/'Cp'))'
else
'define showalter=tmpprs(lev='P0')-tcp
+(pcp-'P0')*('k10'+'k11'*ww-'k12'*ww/tcp-'k13'*pcp)'
endif

Regards
Piotr Djaków

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