In this practical we compute the heat budget using measured quantities. It is ma

Question

In this practical we compute the heat budget using measured quantities. It is made up of incoming short wave and outgoing longwave radiation, sensible heat and evaporation. The total budget can be used to estimate changes in soil temperature. Field data for the calculation are given below Label Variable Value Wind speed m/s 10 m Air Temperature Surface Temperature 10 m Specific Humidity a Surface Spec Humidity 22 ? 26 C 15 g/kg 20 g/kg qs 1. Calculate the solar insolation at 9h00 assuming the season is equinox eg. 21 March and the latitude is Puerto Rico 18°N, with the equation Qs- (sin(d))(S)(insolation fraction) where S is the solar constant 1370 W m-2 d is the sun angle (90 deg latitude - season), and dividing for time of day, the fraction 0.6 insolation

Explanation / Answer

1. Qs = sind* S * insolation factor

d=(90-18-0)/9=8

Qs =sin8*1370*0.6

Qs = 813.25

2. QL = d*(273K+Ts )4 greenhouse factor

            =5.67*10-8 *( 273+26+273)4 *0.4

         =2427.87

3.Qh =U*(Ts- Ta)

        =5(26-22)

        =20

4.Qe=2.5*U*(qs-qa)

      = 2.5*5*(20-15)

       =62.5

5. Qr= Qs-(QL+Qh+Qe)

       =813.25-(2427.87+20+62.5)  

       =-1697.12

6.dT=QrdtMCp

       =-1697.12*4*1.2*103 * 0.8* 103

         = -6.5*108

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