5. Evaporation#
Fig. 5.1 Evaporation after a heavy rainfall. Wulai, Taiwan – photo by (Senning Luk, 2020).#
Nomenclature
Symbol |
Quantity |
Quantity name in Dutch |
Dimension |
Widely used unit (if not SI) |
|---|---|---|---|---|
\(A\) |
System area |
Oppervlakte van het systeem |
[L\(^2\)] |
|
\(C\) |
Runoff coefficient |
Afvoercoëfficiënt |
[-] |
|
\(C_e\) |
Empirical constant, equal to 0.65 in the Netherlands |
Empirische constante, gelijk aan 0.65 in Nederland |
[-] |
|
\(c_p\) |
Specific heat of air at constant pressure, equal to 1104 Jkg\(^{-1}\)K\(^{-1}\) |
Soortelijke warmte van lucht bij constante druk, gelijk aan 1104 Jkg\(^{-1}\)K\(^{-1}\) |
[Jkg\(^{-1}\)K\(^{-1}\)] |
|
\(D\) |
Drought index |
Droogte index |
[-] |
|
\(E\) |
Net evaporation per unit area |
Netto verdamping per eenheidsoppervlak |
[L/T] |
|
\(E_a\) |
Actual evaporation per unit area |
Werkelijke verdamping per eenheidsoppervlak |
[L/T] |
|
\(E_i\) |
Interception evaporation per unit area |
Interceptieverdamping per eenheidsoppervlak |
[L/T] |
|
\(E_o\) |
Open water evaporation per unit area |
Openwaterverdamping per eenheidsoppervlak |
[L/T] |
|
\(E_p\) |
Potential evaporation per unit area |
Potentiële verdamping per eenheidsoppervlak |
[L/T] |
|
\(E_{p, crop}\) |
Potential evaporation of a crop |
Potentiële verdamping van een gewas |
[L/T] |
|
\(E_{pan}\) |
Pan evaporation |
Panverdamping |
[L/T] |
|
\(E_{ref}\) |
Reference evaporation |
Referentieverdamping |
[L/T] |
|
\(E_s\) |
Soil evaporation per unit area |
Bodemverdamping per eenheidsoppervlak |
[L/T] |
|
\(E_{sub}\) |
Snow or ice evaporation per unit area |
Sneeuw of ijs verdamping per eenheidsoppervlak |
[L/T] |
|
\(E_t\) |
Transpiration per unit area |
Transpiratie per eenheidsoppervlak |
[L/T] |
|
\(e_a(T)\) |
Actual vapour pressure |
Werkelijke dampspanning |
[ML\(^{-1}\)T\(^{-2}\)] |
|
\(e_s(T)\) |
Saturation vapour pressure |
Verzadigingsdampspanning |
[ML\(^{-1}\)T\(^{-2}\)] |
|
\(G\) |
Ground heat flux |
Bodem warmteflux |
[M/T\(^{3}\)] |
|
\(H\) |
Sensible heat flux |
Voelbare warmtestroom |
[M/T\(^{3}\)] |
|
\(h\) |
Relative humidity |
Relatieve vochtigheid |
[-] |
|
\(h\) |
Water level |
Waterhoogte |
[L] |
|
\(k_c\) |
Crop factor |
Gewasfactor |
[-] |
|
\(k_s\) |
Stress factor |
Stressfactor |
[-] |
|
\(k_{pan}\) |
Pan coefficient |
Pancoëfficiënt |
[-] |
|
\(N\) |
Number of possible hours of sunshine |
Mogelijk aantal uren zon |
[T] |
– |
\(n\) |
Number of actual hours of sunshine |
Werkelijk aantal uren zon |
[T] |
– |
\(P\) |
Net water supply per unit area (precipitation) |
Netto watertoevoer per eenheidsoppervlak (neerslag) |
[L/T] |
|
\(Q\) |
Net water volume entering or leaving the system (discharge) |
Netto watervolume dat het systeem in-of uitstroomt (afvoer) |
[L\(^3\)/T] |
|
\(Q_{in}\) |
Inflow |
Instroom |
[L/T\(^{3}\)] |
|
\(Q_{out}\) |
Outflow |
Uitstroom |
[L/T\(^{3}\)] |
|
\(R_a\) |
Short wave radiation energy received at the outer limits of the atmosphere |
Kortgolvige stralingsenergie die de buitenste lagen van de atmosfeer bereikt |
[M/T\(^{3}\)] |
|
\(R_{in}\) |
Incoming radiation |
Inkomende straling |
[M/T\(^{3}\)] |
|
\(R_l\) |
Longwave radiation |
Langgolvige straling |
[M/T\(^{3}\)] |
|
\(R_n\) |
Net radiation |
Netto straling |
[M/T\(^{3}\)] |
|
\(R_{out}\) |
Outgoing radiation |
Uitgaande straling |
[M/T\(^{3}\)] |
|
\(R_s\) |
Shortwave radiation |
Kortgolvige straling |
[M/T\(^{3}\)] |
|
\(r\) |
Albedo |
Reflectiecoëfficiënt (albedo) |
[-] |
|
\(r_a\) |
Aerodynamic resistance to water vapour transport |
Aerodynamische weerstand tegen transport van waterdamp |
[T/L] |
|
\(r_c\) |
Crop resistance |
Gewasweerstand |
[T/L] |
|
\(S\) |
Storage |
Berging |
[L\(^3\)] |
|
\(T\) |
Temperature |
Temperatuur |
[°C] |
|
\(T_a\) |
Air temperature (dry thermometer) (atmosphere temperature) |
Lucht temperatuur (Drogeboltemperatuur) |
[°C] |
|
\(T_d\) |
Dew temperature |
Dauwpunt |
[°C] |
|
\(T_s\) |
Temperature of the surface |
Temperatuur van het oppervlakte |
[°C] |
|
\(T_w\) |
Wet bulb temperature (wet thermometer) |
Natteboltemperatuur |
[°C] |
|
\(s(T)\) = \(\frac{\textrm{d}e_s}{\textrm{d}T}\) |
Slope of saturation vapour pressure curve |
Helling verzadingingsdampspanningskromme |
— |
[kPa/°C] |
\(u_2\) |
Wind speed (at 2m height) |
Windsnelheid (op 2m hoogte) |
[L/T] |
[m/s] |
\(\rho\) |
Density of water, equal to 1000 kg/m\(^{3}\) |
Dichtheid van water, gelijk aan 1000 kg/m\(^{3}\) |
[kg/m\(^{3}\)] |
|
\(\rho_a\) |
Density of air, equal to 1.205 kg/m\(^{3}\) |
Dichtheid van lucht, gelijk aan 1.205 kg/m\(^{3}\) |
[kg/m\(^{3}\)] |
|
\(\lambda\) |
Latent heat of vaporizationm, equal to 2.45 MJ/kg |
Verdampingswarmte van water, gelijk aan 2.45 MJ/kg |
[J/kg] |
|
\(\rho \lambda E\) |
Latent heat flux |
Latente warmtestroom |
[M/T\(^{3}\)] |
|
\(\gamma\) |
Psychrometer constant, equal to 0.066 kPa/°C |
Psychrometerconstante, gelijk aan 0.066 kPa/°C |
[kPa/°C] |
|
\(\epsilon\) |
Emissivity coefficient |
Emissiviteitscoëfficiënt |
[-] |
|
\(\sigma\) |
Stefan Bolzmann coeficient, equal to 4.9 \(\cdot\) 10\(^{-3}\) J d\(^{-1}\) m\(^{-2}\) K\(^{-4}\) |
Stefan-Boltzmann constante, gelijk aan 4.9 \(\cdot\) 10\(^{-3}\) J d\(^{-1}\) m\(^{-2}\) K\(^{-4}\) |
[J d\(^{-1}\) m\(^{-2}\) K\(^{-4}\)] |