From a standard micro$-$meteorological station over a cotton field with

instruments installed at zm $=2$ m$,$ the average daily air temperature and the

air relative humidity are observed to be Ta $=20$C and RH $=70\%,$

respectively. The wind speed is recorded as va $=2$ m$/$s$,$ atmospheric pressure

as P $=1000$ mb and the net radiation as Rn $=350$ W$/$m$2$

$.$ The density of air

under these conditions is $1\mathrm{.}19$ kg$/$m$3$

$.$ Constants given: $\backslash$lambda $=2\mathrm{.}44$MJ$/$kg$,$ ca $=$

$1005$ J$/$kg$/$K$,$ Rv $=463$ J$/$kg$/$K

a$.$ Sketch the system, label the known and unknown variables, and identify the

equations needed.

b$.$ Estimate the daily evapotranspiration $($E in mm$/$day$)$ if the vegetation height is

zveg $=1$ m and the total plant stomatal resistance is measured as rs $=30$ s$/$m$.$

Utilize the Penman$-$Monteith equation to estimate evapotranspiration.