Campbell CS105MD Dokumentacja Pobierz pdf (Strona 64)

Appendix A. Evapotranspiration, Vapor Pressure Deficit, and Crop Water Needs

Table 1. Names, symbols and units of all quantities used in calculations of hourly ET

values.

Symbol Unit

Meteorological Data

Mean hourly temperature Ta

Mean hourly RH RH percent

Mean hourly wind speed at 2 meter height u

m/sec

Total hourly solar radiation Rs MJ/m

/hour

Data Related to Station's Location

Elevation Z meters

Weather station's longitude (user-entered) Lm degrees

Always west of Greenwich line minutes

(with Greenwich line as 0 degrees) seconds

Weather station's latitude (user-entered) phi degrees

minutes

seconds

North or south of the Equator (user-entered) N or S No Units

Standard meridian (midpoint of the time zone) Lz degrees

Anemometer position above the ground level (user-entered) Ht meters

Data Related to Time

Day of the year J or DOY integer

Begin time hour (military time, hour; e.g., 1400) tBegin hour

End time hour (military time, hour; e.g., 1500) tEnd hour

Standard (military) time at step's midpoint (e.g.; 14.5) time hour

Calculated Values

Slope of the vapor pressure curve

kPa/

Specific heat capacity at constant pressure C

=0.001103 MJ/kg/

Ratio of mol weights of water to dry air

ε=0.622

no units

A-10

1 2 ... 59 60 61 62 63 64 65 66 67 68 69 ... 77 78

Brak uwag

Campbell CS105MD Dokumentacja Strona 64