Vapor pressure deficit (kPa)

Vapor pressure deficit (VPD) is the day time mean vapor pressure deficit. calculated from the a day time maxiumum vapor pressure deficit.

VPD = VPDmax · 0.66

Where 0.66 is the ratio of daily VPD_max to daily VPD.

Maximum VPD

The model will attempt to provide a day time maxiumum vapor pressure deficit based on available data:

VPDmax =	ì í î	VPDdewptmax	if dew point temperature is provided
		VPDrelhumidmax	if relative humidity is provided
		VPDtempmax	otherwise (estimated from temperature)

Maximum VPD based on dew point temperature

VPDdewptmax = VPsatTmax - VPsatDewptmax

Maximum VPD based on relative humidity

VPDRelhumidmax = VPsatTmax · ( 1.0 -

Relhumidmin 100

)

Maximum VPD estimated from temperature

VPDTempmax =

VPSatTmax - VPsatTmin 1 - a · [ VPsatTmax - VPsatTmin]

VPD parameters

VPsatTmax	(kPa)	saturated vapor pressure at maximum temperature.
VPsatTmin	(kPa)	saturated vapor pressure at minimum temperature.
VPsatDewptmax	(kPa)	saturated vapor pressure at maximum dew point temperature.
Relhumidmin	%	Is the minimum relative humidity