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wet_bulb_potential_temp

PURPOSE ^

WET_BULB_POTENTIAL_TEMP wet bulb potential temperature

SYNOPSIS ^

function theta_w = wet_bulb_potential_temp(rh, T, p)

DESCRIPTION ^

  WET_BULB_POTENTIAL_TEMP wet bulb potential temperature

   wet-bulb potential temperature—(Also called pseudo wet-bulb potential
   temperature.) The temperature an air parcel would have if cooled from
   its initial state adiabatically to saturation, and thence brought to 
   1000 mb by a moist-adiabatic process. This temperature is conservative
   with respect to reversible adiabatic changes. 
   (REF: http://amsglossary.allenpress.com/glossary/)

 FORMAT   theta_w = wet_bulb_potential_temp(Tc, p, w) 
        
 OUT   theta_w  wet bulb potential temperature [K]
 IN    rh  relative humidity [%], rh > 0 and it can be a scalar or a tensor
       T   air temperature [K], a scalar or a tensor
       p   air pressure [Pa], a scalar or a tensor

 EXAMPLE:
       theta_w = wet_bulb_potential_temp(50, 298, 90000)
       theta_w = 295.6460

 ACCURACY: WET_BULB_POTENTIAL_TEMP estimates water vapor pressure according
           to thermodynamic functions without any assumptions. 

 Reference: A short course in cloud physics (Chapter II, water vapor and
            its thermodynamic effects); 1996, By: R. R. Rogers and M. M. Yau
            page: 21

 2009-08-15   Created by Isaac Moradi.

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

DOWNLOAD ^

wet_bulb_potential_temp.m

SOURCE CODE ^

0001 function theta_w = wet_bulb_potential_temp(rh, T, p) 
0002 %  WET_BULB_POTENTIAL_TEMP wet bulb potential temperature
0003 %
0004 %   wet-bulb potential temperature—(Also called pseudo wet-bulb potential
0005 %   temperature.) The temperature an air parcel would have if cooled from
0006 %   its initial state adiabatically to saturation, and thence brought to
0007 %   1000 mb by a moist-adiabatic process. This temperature is conservative
0008 %   with respect to reversible adiabatic changes.
0009 %   (REF: http://amsglossary.allenpress.com/glossary/)
0010 %
0011 % FORMAT   theta_w = wet_bulb_potential_temp(Tc, p, w)
0012 %
0013 % OUT   theta_w  wet bulb potential temperature [K]
0014 % IN    rh  relative humidity [%], rh > 0 and it can be a scalar or a tensor
0015 %       T   air temperature [K], a scalar or a tensor
0016 %       p   air pressure [Pa], a scalar or a tensor
0017 %
0018 % EXAMPLE:
0019 %       theta_w = wet_bulb_potential_temp(50, 298, 90000)
0020 %       theta_w = 295.6460
0021 %
0022 % ACCURACY: WET_BULB_POTENTIAL_TEMP estimates water vapor pressure according
0023 %           to thermodynamic functions without any assumptions.
0024 %
0025 % Reference: A short course in cloud physics (Chapter II, water vapor and
0026 %            its thermodynamic effects); 1996, By: R. R. Rogers and M. M. Yau
0027 %            page: 21
0028 %
0029 % 2009-08-15   Created by Isaac Moradi.
0030 
0031 cp=constants('SPECIFIC_HEAT_CONST_PRES');
0032 cv=constants('SPECIFIC_HEAT_CONST_VOL');
0033 k = (cp - cv) / cp; % also equals constants('GAS_CONST_DRY_AIR') / cp
0034 
0035 % calculate isentropic condensation temperature
0036 Tc = isentr_conden_temp(rh, T, p) ;
0037 
0038 % calculate mixing ratio
0039 r = water_vapor_mixing_ratio(rh, T, p);
0040 
0041 % calculate theta_w
0042 k_m = k .* (1 - 0.2 .* r);
0043 theta_w = Tc .* power((100 ./  (p ./ 1000)), k_m);
0044 
0045

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