def rh2mr(p,t,rh,Tconvert=None):
"""(w1,w2) = rh2mr(p,t,rh,Tconvert)
determine H2O mixing ratio (w, g/kg) given
reference pressure (mbar), temperature (t,K), and
relative humidity (rh,%)
Two mixing ratios are returned: w1 is with RH defined as the ratio
of water vapor partial pressure to saturation vapor pressure and
w2 is with RH defined as the ratio of water vapor mixing ratio to
saturation mixing ratio.
if input, Tconvert is used as the temperature point to switch
from using saturation vapor pressure over water to over ice.
DCT 3/5/00
"""
# saturation pressure
if (Tconvert is None):
esat = satvap(t) # Goff Gratch formulation, over water
wsat = satmix(p,t) # Goff Gratch formulation, over water
else:
esat = satvap(t,Tconvert) # Goff Gratch formulation, over water/ice
wsat = satmix(p,t,Tconvert) # Goff Gratch formulation, over water/ice
# H2O partial pressure
e = rh/100.0*esat
# H2O mixing ratio
w1 = e2mr(p,e)
# using WMO definition of relative humidity
w2 = rh/100.0*wsat
return(w1,w2)
def rh2e(p, t, rh, Tconvert=None):
"""(e1,e2) = rh2e(p,t,rh,Tconvert)
determine H2O partial pressure (e,mbar) given
pressure (p,mbar), temperature (t,K), and
relative humidity (rh,%)
Two H2O partial pressures are returned: e1 is with RH defined as
the ratio of water vapor partial pressure to saturation vapor
pressure and e2 is with RH defined as the ratio of water vapor
mixing ratio to saturation mixing ratio.
if input, Tconvert is used as the temperature point to switch
from using saturation vapor pressure over water to over ice.
DCT 3/6/00
"""
# ratio of water mass to dry air mass
eps = 0.621970585
# saturation pressure
if (Tconvert is None):
esat = satvap(t) # Goff Gratch formulation, over water
wsat = satmix(p, t) # Goff Gratch formulation, over water
else:
esat = satvap(t, Tconvert) # Goff Gratch formulation, over water/ice
wsat = satmix(p, t,
Tconvert) # Goff Gratch formulation, over water/ice
# H2O partial pressure w/ RH defined as ratio of pressures
e1 = rh / 100.0 * esat
# H2O partial pressure w/ RH defined as ratio of mixing ratios
e2 = (rh / 100.0 * esat / (p - esat) * p) / (rh / 100.0 * esat /
(p - esat) + 1.0)
return (e1, e2)
def rh2mr(p, t, rh, Tconvert=None):
"""(w1,w2) = rh2mr(p,t,rh,Tconvert)
determine H2O mixing ratio (w, g/kg) given
reference pressure (mbar), temperature (t,K), and
relative humidity (rh,%)
Two mixing ratios are returned: w1 is with RH defined as the ratio
of water vapor partial pressure to saturation vapor pressure and
w2 is with RH defined as the ratio of water vapor mixing ratio to
saturation mixing ratio.
if input, Tconvert is used as the temperature point to switch
from using saturation vapor pressure over water to over ice.
DCT 3/5/00
"""
# saturation pressure
if (Tconvert is None):
esat = satvap(t) # Goff Gratch formulation, over water
wsat = satmix(p, t) # Goff Gratch formulation, over water
else:
esat = satvap(t, Tconvert) # Goff Gratch formulation, over water/ice
wsat = satmix(p, t,
Tconvert) # Goff Gratch formulation, over water/ice
# H2O partial pressure
e = rh / 100.0 * esat
# H2O mixing ratio
w1 = e2mr(p, e)
# using WMO definition of relative humidity
w2 = rh / 100.0 * wsat
return (w1, w2)
def mr2rh(p,t,w,Tconvert=None):
"""(rh1,rh2) = mr2rh(p,t,w,Tconvert)
determine relative humidity (%) given
reference pressure (mbar), temperature (t,K), and
water vapor mass mixing ratio (w,g/kg)
Two RHs are returned: rh1 is with RH defined as the ratio
of water vapor partial pressure to saturation vapor pressure and
rh2 is with RH defined as the ratio of water vapor mixing ratio to
saturation mixing ratio.
if input, Tconvert is used as the temperature point to switch
from using saturation vapor pressure over water to over ice.
DCT 3/5/00
"""
# saturation pressure
if ( Tconvert is None):
esat = satvap(t) # Goff Gratch formulation, over water
wsat = satmix(p,t) # Goff Gratch formulation, over water
else:
esat = satvap(t,Tconvert) # Goff Gratch formulation, over water/ice
wsat = satmix(p,t,Tconvert) # Goff Gratch formulation, over water/ice
# H2O partial pressure
e = mr2e(p,w)
# RH using ratios of gas pressures
rh1 = 100.0*e/esat
# RH using WMO definition of relative humidity
rh2 = 100.0*w/wsat
return (rh1,rh2)
def mr2rh(p, t, w, Tconvert=None):
"""(rh1,rh2) = mr2rh(p,t,w,Tconvert)
determine relative humidity (%) given
reference pressure (mbar), temperature (t,K), and
water vapor mass mixing ratio (w,g/kg)
Two RHs are returned: rh1 is with RH defined as the ratio
of water vapor partial pressure to saturation vapor pressure and
rh2 is with RH defined as the ratio of water vapor mixing ratio to
saturation mixing ratio.
if input, Tconvert is used as the temperature point to switch
from using saturation vapor pressure over water to over ice.
DCT 3/5/00
"""
# saturation pressure
if (Tconvert is None):
esat = satvap(t) # Goff Gratch formulation, over water
wsat = satmix(p, t) # Goff Gratch formulation, over water
else:
esat = satvap(t, Tconvert) # Goff Gratch formulation, over water/ice
wsat = satmix(p, t,
Tconvert) # Goff Gratch formulation, over water/ice
# H2O partial pressure
e = mr2e(p, w)
# RH using ratios of gas pressures
rh1 = 100.0 * e / esat
# RH using WMO definition of relative humidity
rh2 = 100.0 * w / wsat
return (rh1, rh2)
def e2rh(p,t,e,Tconvert=None):
"""(rh1,rh2) = e2rh(p,t,e,Tconvert)
determine relative humidity (e,mbar) given
pressure (p,mbar), temperature (t,K), and
H2O partial pressure (e,mbar)
Two RHs are returned: rh1 is with RH defined as the ratio
of water vapor partial pressure to saturation vapor pressure and
rh2 is with RH defined as the ratio of water vapor mixing ratio to
saturation mixing ratio.
if input, Tconvert is used as the temperature point to switch
from using saturation vapor pressure over water to over ice.
DCT 3/6/00
"""
# saturation pressure
if ( Tconvert is None ):
esat = satvap(t) # Goff Gratch formulation, over water
wsat = satmix(p,t) # Goff Gratch formulation, over water
else:
esat = satvap(t,Tconvert) # Goff Gratch formulation, over water/ice
wsat = satmix(p,t,Tconvert) # Goff Gratch formulation, over water/ice
# w/ RH defined as ratio of pressures
rh1 = 100.0*e/esat
# w/ RH defined as a ratio of mass mixing ratios
w = e2mr(p,e)
rh2 = 100.0*w/wsat
return(rh1,rh2)
def rh2e(p,t,rh,Tconvert=None):
"""(e1,e2) = rh2e(p,t,rh,Tconvert)
determine H2O partial pressure (e,mbar) given
pressure (p,mbar), temperature (t,K), and
relative humidity (rh,%)
Two H2O partial pressures are returned: e1 is with RH defined as
the ratio of water vapor partial pressure to saturation vapor
pressure and e2 is with RH defined as the ratio of water vapor
mixing ratio to saturation mixing ratio.
if input, Tconvert is used as the temperature point to switch
from using saturation vapor pressure over water to over ice.
DCT 3/6/00
"""
# ratio of water mass to dry air mass
eps = 0.621970585
# saturation pressure
if (Tconvert is None):
esat = satvap(t) # Goff Gratch formulation, over water
wsat = satmix(p,t) # Goff Gratch formulation, over water
else:
esat = satvap(t,Tconvert) # Goff Gratch formulation, over water/ice
wsat = satmix(p,t,Tconvert) # Goff Gratch formulation, over water/ice
# H2O partial pressure w/ RH defined as ratio of pressures
e1 = rh/100.0*esat
# H2O partial pressure w/ RH defined as ratio of mixing ratios
e2 = (rh/100.0*esat/(p-esat)*p)/(rh/100.0*esat/(p-esat)+1.0);
return(e1,e2)
def e2rh(p, t, e, Tconvert=None):
"""(rh1,rh2) = e2rh(p,t,e,Tconvert)
determine relative humidity (e,mbar) given
pressure (p,mbar), temperature (t,K), and
H2O partial pressure (e,mbar)
Two RHs are returned: rh1 is with RH defined as the ratio
of water vapor partial pressure to saturation vapor pressure and
rh2 is with RH defined as the ratio of water vapor mixing ratio to
saturation mixing ratio.
if input, Tconvert is used as the temperature point to switch
from using saturation vapor pressure over water to over ice.
DCT 3/6/00
"""
# saturation pressure
if (Tconvert is None):
esat = satvap(t) # Goff Gratch formulation, over water
wsat = satmix(p, t) # Goff Gratch formulation, over water
else:
esat = satvap(t, Tconvert) # Goff Gratch formulation, over water/ice
wsat = satmix(p, t,
Tconvert) # Goff Gratch formulation, over water/ice
# w/ RH defined as ratio of pressures
rh1 = 100.0 * e / esat
# w/ RH defined as a ratio of mass mixing ratios
w = e2mr(p, e)
rh2 = 100.0 * w / wsat
return (rh1, rh2)
def dp2rh(p, t, dp, Tconvert=None):
"""(rh1,rh2) = dp2rh(p,t,dp,Tconvert)
compute relative humidity (%) given total pressure p (mb),
air temperature t (K), and dew point temperature (K).
if input, Tconvert is used as the AIR temperature to switch
from using saturation vapor pressure over water to over ice.
Two relative humidities are returned: rh1 is with RH defined as
the ratio of water vapor partial pressure to saturation vapor
pressure and rh2 is with RH defined as the ratio of water vapor
mixing ratio to saturation mixing ratio.
dct 3/6/2000
"""
# vapor pressures computed at dew point temperature over water and ice
e = eswat_goffgratch(dp) # Goff Gratch formulation, over water
# saturation pressure and mixing ratios computed at air temperaure
if (Tconvert is None):
esat = satvap(t)
wsat = satmix(p, t)
else:
esat = satvap(t, Tconvert)
wsat = satmix(p, t, Tconvert)
eice = esice_goffgratch(dp) # Goff Gratch formulation, over ice
ind = num.where(t <= Tconvert)
e[ind] = eice[ind] # over ice for air temperatures <= Tconvert
# water vapor mixing ratio
w = e2mr(p, e)
# corresponding RH (as a ratio of pressures)
rh1 = 100.0 * e / esat
# WMO definition of RH gives a second mixing ratio and RH
rh2 = 100.0 * w / wsat
return (rh1, rh2)