Vapour Pressure Deficit Calculation

Compute VPD using the provided air temperature, dew point, pressure at MSL and elevation. It is based on Yuan et al. (2019).

Syntax:

VPD = calVPD(Ta,Td,Pmsl,z)
VPD = calVPD(Ta,Td,Pmsl,z,'AVPMethodOption','CC_method')
VPD = calVPD(Ta,Td,Pmsl,z,'AVPMethodOption','RH_method','RHVec',RH)

Input variables:

Ta, Td, Pmsl, z: Near Surface Air Temperature (UNIT: deg. C),

Near Surface Dew Point Temperature (UNIT: deg. C),

Air Pressure at Mean Sea Level(UNIT: hPa), Elevation

(UNIT: m). These four are mandatory inputs.

AVPMethodOption: It takes the Actual Vapour Pressure Calculation Method.

Two option is now permissible: Clausius-Clapeyron based

method (default option) and Relative Humidity based

method

RH: Matrix of relative humidity (UNIT:%)

Output variables:

VPD: Vapour pressure deficit (UNIT: kPa) matrix

Follow the VPD methodlogy explained in Yuan et al. (2019) [Increased atmospheric vapor pressure deficit reduces global vegetation growth | Science Advances] for the equation used.