Noah model characteristics

Evapotranspiration

(Figure 1, Chen and Dudhia 2001)

Evaporation components

\[ E_a = E_{dir} + E_c + E_t \]

$E_a$: total evapotranspiration

$E_{dir}$: direct evaporation from the (land) surface

$E_c$: evaporation of intercepted precipitation in the plant canopy

$E_t$: Plant transpiration

\[ E_{dir} = (1 - \sigma_f) \beta E_p \]

where \beta is a soil wetness factor

\[ \beta = \frac{\Theta_1 - \Theta_w}{\Theta_{ref} - \Theta_w} \]

and E_p$ is the potential evaporation, which is calculated by a Penman-based energy balance approach that includes stability-dependent aerodynamic resistance (Mahrt and Ek 1984).

module_sf_noahlsm.F & module_sf_noahdrv.F


!   EC         CANOPY WATER EVAPORATION (W m-2)
!   EDIR       DIRECT SOIL EVAPORATION (W m-2)
!   ET(NSOIL)  PLANT TRANSPIRATION FROM A PARTICULAR ROOT (SOIL) LAYER
!                 (W m-2)
!   ETT        TOTAL PLANT TRANSPIRATION (W m-2)

Urban land cover type

module_sf_noahlsm.F

Soil characteristics


IF(VEGTYP==ISURBAN)THEN
        SHDFAC=0.05
        RSMIN=400.0
        SMCMAX = 0.45  ! POROSITY, I.E. SATURATED VALUE OF SOIL MOISTURE
        SMCREF = 0.42  ! SOIL MOISTURE THRESHOLD WHERE TRANSPIRATION BEGINS TO STRESS
        SMCWLT = 0.40  ! WILTING POINT 
        SMCDRY = 0.40  ! DRY SOIL MOISTURE THRESHOLD WHERE DIRECT EVAP FRM TOP LAYER ENDS
    ENDIF

    ...

L1627~
urban
        IF( VEGTYP == ISURBAN ) then
            CSOIL_LOC=3.0E6
        ELSE
            CSOIL_LOC=CSOIL
        ENDIF

...

L2156~
!urban
      IF ( VEGTYP == ISURBAN ) DF1=3.24

For soil temperature calculation, the diffusion coefficient is fixed to be 3.24, which is furthe reduced