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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 [2019/09/20 12:50] cpers [Alternative potential evaporation models] |
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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> |