Changeset 1715 in lmdz_wrf

Timestamp:

Dec 13, 2017, 10:21:41 PM (7 years ago)

Author:

lfita

Message:

Finally understanding RH formula!

File:

• trunk/tools/diag_tools.py (modified) (1 diff)

trunk/tools/diag_tools.py

@@ -1272 +1272 @@
       [p] = pressure field (assuming in [Pa])
       [q] = mixing ratio in [kgkg-1]
+      ref.: M. G. Lawrence, BAMS, 2005, 225
+    >>> print var_rh(101300., 290., 3.)
+    0.250250256174
     """
     fname = 'var_rh'
 
-    data1 = 10.*0.6112*np.exp(17.67*(t-273.16)/(t-29.65))
-    data2 = 0.622*data1/(0.01*p-(1.-0.622)*data1)
-
-    rh = q/data2
+    # Enthalpy of vaporization [Jkg-1]
+    L = 2.453*10.**6
+    # Gas constant for water vapor [JK-1Kg-1]
+    Rv = 461.5 
+
+    # Computing saturated pressure 
+    #es = 10.*0.6112*np.exp(17.67*(t-273.16)/(t-29.65))
+    #es = 6.11*np.exp(L/Rv*(1.-273./t)/273.)
+
+    # August - Roche - Magnus formula
+    es = 6.1094*np.exp(17.625*(t-273.15)/((t-273.15)+243.04))
+
+    # Saturated mixing ratio [g/kg]
+    ws = 0.622*es/(0.01*p-es)
+
+    rh = q/(ws*1000.)
 
     return rh