~ ~ ~ PURPOSE ~ ~ ~ this subroutine calculates potential plant transpiration for Priestley- Taylor and Hargreaves ET methods, and potential and actual soil evaporation. NO3 movement into surface soil layer due to evaporation is also calculated.
~ ~ ~ INCOMING VARIABLES ~ ~ ~ name |units |definition ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ canstor(:) |mm H2O |amount of water held in canopy storage ep_max |mm H2O |maximum amount of transpiration (plant et) |that can occur on current day in HRU esco(:) |none |soil evaporation compensation factor ihru |none |HRU number ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~ ~ ~ OUTGOING VARIABLES ~ ~ ~ name |units |definition ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ canev |mm H2O |amount of water evaporated from canopy |storage ep_max |mm H2O |maximum amount of transpiration (plant et) |that can occur on current day in HRU es_day |mm H2O |actual amount of evaporation (soil et) that |occurs on day in HRU snoev |mm H2O |amount of water in snow lost through |sublimation on current day ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ SUBROUTINES/FUNCTIONS CALLED ~ ~ ~ Intrinsic: Exp, Min, Max
~ ~ ~ ~ ~ ~ END SPECIFICATIONS ~ ~ ~ ~ ~ ~
added statements for test of real statement above evaporate canopy storage first canopy storage is calculated by the model only if the Green & Ampt method is used to calculate surface runoff. The curve number methods take canopy effects into account in the equations. For either of the CN methods, canstor will always equal zero. compute potential plant evap for methods other that Penman-Monteith
compute potential soil evaporation make sure maximum plant and soil ET doesn't exceed potential ET adjust es_max and ep_max for impervous urban cover
initialize soil evaporation variables compute sublimation take all soil evap from snow cover take all soil evap from snow cover before taking from soil compute evaporation from ponded water take all soil evap from wetland storage before taking from soil take soil evap from each soil layer depth exceeds max depth for soil evap (esd) calculate evaporation from soil layer adjust soil storage, potential evap compute no3 flux from layer 2 to 1 by soil evaporation update total soil water content calculate actual amount of evaporation from soil