start:hype_model_description:processes_above_ground
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start:hype_model_description:processes_above_ground [2019/03/19 16:12] cpers [Evaporation] |
start:hype_model_description:processes_above_ground [2020/02/13 14:18] cpers [Rainfall and snowfall calculation] |
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| Where <m>{Delta}h</m> is a class's elevation deviation from the subbasin average elevation and //snfrac// is the average fraction of precipitation that falls as snow calculated from subbasin temperature (<m>T_i</m>) and temperature thresholds (see equation below), or from input. | Where <m>{Delta}h</m> is a class's elevation deviation from the subbasin average elevation and //snfrac// is the average fraction of precipitation that falls as snow calculated from subbasin temperature (<m>T_i</m>) and temperature thresholds (see equation below), or from input. | ||
| - | ==== Rainfall and snowfall calculation ==== | + | ==== Rainfall and snowfall separation ==== |
| The rain/snow fraction of precipitation is calculated based on temperature or given as an input time series. Different temperatures can be used in the equation, i.e. basin average or class temperature. When the air temperature (//T//) is around the threshold temperature for mixed precipitation (land-use dependent parameter //ttmp// plus general parameter //ttpd//) both rain and snow. The interval for mixed precipitation is given by the parameter //ttpi//. For temperature below threshold minus //ttpi//, the precipitation is assumed to be in solid form only and is added to the snowpack. If the air temperature is greater than the threshold temperature plus //ttpi//, the precipitation is assumed to be solely in liquid form. For intermediate temperatures, the precipitation is assumed to be a mixture of liquid and solid forms i.e. as both rain and snow. The proportion (<m>a_rain</m>) of precipitation (//P//) that falls as rain depends linearly on the temperature. | The rain/snow fraction of precipitation is calculated based on temperature or given as an input time series. Different temperatures can be used in the equation, i.e. basin average or class temperature. When the air temperature (//T//) is around the threshold temperature for mixed precipitation (land-use dependent parameter //ttmp// plus general parameter //ttpd//) both rain and snow. The interval for mixed precipitation is given by the parameter //ttpi//. For temperature below threshold minus //ttpi//, the precipitation is assumed to be in solid form only and is added to the snowpack. If the air temperature is greater than the threshold temperature plus //ttpi//, the precipitation is assumed to be solely in liquid form. For intermediate temperatures, the precipitation is assumed to be a mixture of liquid and solid forms i.e. as both rain and snow. The proportion (<m>a_rain</m>) of precipitation (//P//) that falls as rain depends linearly on the temperature. | ||
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| === Model 4 - Priestly-Taylor === | === Model 4 - Priestly-Taylor === | ||
| - | The Priestly-taylor potential evaporation depends on net downward radiation (//netrad//), slope of saturated vapour pressure curve (//dsatvap//), latent heat of vaporization (<m>lambda</m>) and a psychrometric constant (<m>gamma</m>). One general parameter (//alfapt//) are used and one land use dependent (crop coefficient //kc4// or //kc//). | + | The Priestly-Taylor potential evaporation depends on net downward radiation (//netrad//), slope of saturated vapour pressure curve (//dsatvap//), latent heat of vaporization (<m>lambda</m>) and a psychrometric constant (<m>gamma</m>). One general parameter (//alfapt//) are used and one land use dependent (crop coefficient //kc4// or //kc//). |
| <m> epot_{base} = MAX(0,kc*alfapt * {dsatvap*netrad/lambda*(dsatvap+gamma)}) </m> | <m> epot_{base} = MAX(0,kc*alfapt * {dsatvap*netrad/lambda*(dsatvap+gamma)}) </m> | ||
| === Model 5 - FAO Penman-Monteith === | === Model 5 - FAO Penman-Monteith === | ||
| - | The FOA Penman-Monteith potential evaporation depends on net downward radiation (//netrad//), slope of saturated vapour pressure curve (//dsatvap//), saturated and actual vapour pressure (//satvap// and //actvap//), temperature (//T//), wind speed (//wind//) and a psychrometric constant (<m>gamma</m>). One land use dependent parameter (crop coefficient //kc5// or //kc//) is used. | + | The FAO Penman-Monteith potential evaporation depends on net downward radiation (//netrad//), slope of saturated vapour pressure curve (//dsatvap//), saturated and actual vapour pressure (//satvap// and //actvap//), temperature (//T//), wind speed (//wind//) and a psychrometric constant (<m>gamma</m>). One land use dependent parameter (crop coefficient //kc5// or //kc//) is used. |
| <m> epot_{base} = MAX(0,kc*{0.408 * dsatvap*netrad + gamma*{{900}/{T+273}}*wind*(satvap-actvap)}/{dsatvap+gamma*(1+0.34*wind)}) </m> | <m> epot_{base} = MAX(0,kc*{0.408 * dsatvap*netrad + gamma*{{900}/{T+273}}*wind*(satvap-actvap)}/{dsatvap+gamma*(1+0.34*wind)}) </m> | ||
start/hype_model_description/processes_above_ground.txt ยท Last modified: 2024/02/21 08:54 by cpers
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