FUNCTION f_qv_from_rh (RH, T_K, RH0, T_K0, P_PA0) RESULT (QV_KG) !!!-------------------------------------------------------------------------- !!! !!! FUNCTION F_QV_FROM_RH !!! ************************** !!! !!! PURPOSE: !!! ------- !!! TANGENT LINEAR CODE FOR !!! COMPUTING MIXING RATIO FROM RELATIVE HUMIDITY, TEMPERATURE AND PRESSURE !!! !!! THE ERROR DERIVATION SHOULD USED THE TANGENT LINEAR CODE, NOT THE !!! ORIGINAL NON-LINEAR CODE. !!! !! METHOD: !! ------ !! LINEAR OR LOGARITHMIC VERTICAL INTERPOLATION !! OUT OF BOUND LOCATIONS ARE EXTRAPOLATED !! !! INPUT: !! ----- !! RH: RELAITVE HUMIDITY in % !! P_PA: PRESSURE in Pa !! T_K: TEMPERATURE in K !! !! OUTPUT: !! ------ !! QV_KG: MIXING RATIO IN kg/kg !! !! COMMON: NO !! ------- !! EXTERNAL: NO !! -------- !! !! REFERENCES: !! ----------- !! R. R. ROGERS AND M. K. YAU, 1989: A SHORT COURSE IN CLOUD PHYSICS, !! 3ND EDITION, PERGAMON PRESS, PAGE 14-19. !! !! VERIFICATION SET: !! ----------------- !! T_K = 268.15 K, !! TD_K = 262.55 K !! RH = 65 %, !! P_PA = 80000 Pa, !! QV = 2.11E-03 kg/kg, !! !! MODIFICATIONS: !! ------------ !! Developed by Yong-Run Guo (11/07/00) !!----------------------------------------------------------------------------CC IMPLICIT NONE REAL T_K , RH , QV_KG REAL P_PA0, T_K0, RH0 ! REAL P_MB, W_KG REAL ES , QS REAL P_MB0, ES0, QS0, QV_KG0 !------------------------------------------------------------------------------C !...P in mb P_MB0 = P_PA0 / 100. !...VAPOR PRESSURE in mb ES = 6.112 * 17.67 * 243.5 * T_K / & ((T_K0-273.15+243.5)*(T_K0-273.15+243.5)) * & EXP (17.67*(T_K0-273.15)/(T_K0-273.15+243.5)) ES0 = 6.112 * EXP (17.67*(T_K0-273.15)/(T_K0-273.15+243.5)) !...SATURATION MIXING RATIO in kg/kg QS = 0.622 * (P_MB0 * ES ) / & ((P_MB0 - ES0) * (P_MB0 - ES0)) QS0 = 0.622 * ES0 /(P_MB0-ES0) !...MIXING RATIO in kg/kg QV_KG = 0.01 * (RH0 * QS + RH * QS0) QV_KG0 = 0.01 * RH0 * QS0 !...Mixing ratio must be positive IF (QV_KG0 < 0.) QV_KG = 0. RETURN END FUNCTION f_qv_from_rh