LESSONS OF EASTER ISLAND
March 17th, 2016
Tables B.1 and B.2 show the structure and functions for implementing the DISC (direct insolation simulation code) model in Excel®. Note the cell references rely on the exact structure of rows and columns shown. User values are entered in shaded cells.
TABLE B.1
User Location Input Parameters
Row 
Column A Label/Vali 
1 

2 

3 

4 
USER 
5 
INPUTS 
6 
Latitude 
7 
User Value (+N, – S) 
8 
Longitude 
9 
User Value (+E, – W) 
10 
Time Zone 
11 
User Value (W, +E) 
12 
Stn. Pressure 
13 
User Value mB 
14 
Pstn/P0 
15 
= A13/1013.250 
TABLE B.2
Functions to Be Entered in Row 2, from Columns G to W
Column 
Label (Row 1) 
Value or Function (Rows 28761) 
B 
Month 
1 to 12 
C 
Day 
1 to 28, 30, or 31 
D 
DOY 
1 to 365 
E 
Hr 
1 to 23 
F 
Obs. Hour 
1 to 8760 
G 
ETR 
= 1370*(1.00011+0.034221*COS(H2)+0.00128*SIN(H2)+0.000719 *COS(2*H2) +0.000077*(SIN(2*H2))) 
H 
Day Angle 
= 6.283185*(D21)/365 
I 
DEC 
= (0.0069180.399912*C0S(H2)+0.070257*SIN(H2)0.006758 *COS(2*H2) +0.000907*SIN(2*H2)0.002697 *COS(3*H2)+0.00148 *SIN(3*H2))*(180/3.14159) 
J 
EQT 
= (0.000075+0.001868*C0S(H2)0.032077*SIN(H2)0.014615 *COS(2*H2)0.040849*SIN(2*H2))*(229.18) 
K 
Hour Angle 
= 15*( E212.5+ J2/60 +(($A$9$A$11*15)*4)/60) 
L 
Zenith Ang 
= ACOS(COS(I2/(180/3.14159))*COS($A$7/(180/3.14159)) *COS(K2/(180/3.14159))+SIN(I2/(180/3.14159)) *SIN($A$7/(180/3.14159))) *(180/3.14159) 
M 
Air Mass 
= IF(L2<89,$A$15*(1/(COS(L2/(180/3.14159)) +0.15/(93.885L2)A1.253)),0) 
N 
Global Horizontal 
USER VALUE 
O 
Diffuse (optional) 
USER VALUE 
P 
Direct (Optional) 
USER VALUE 
Q 
Kt 
= IF(L2<80,N2/(COS(L2/(180/3.14159))*G2),0) 
R 
DISC Coeff. A 
= IF(Q2>0,IF(Q2>0.6, 5.743+21.77*Q227.49*Q2A2+11.56 *Q2A3, IF(Q2<0.6,0.5121.56*Q2+2.286*Q2A22.222*Q2A3)),0) 
S 
DISC Coeff. B 
= IF(Q2>0,IF(Q2>0.6, 41.4118.5*Q2+66.05*Q2A2+31.9 *Q2A3, IF(Q2<0.6,0.37+0.962*Q2,0)),0) 
T 
DISC Coeff. C 
= IF(Q2>0,IF(Q2>0.6, 47.01+184.2*Q2222*Q2A2+73.81 *Q2A3, IF(Q2<0.6,0.28+0.932*Q22.048*Q2A2,0)),0) 
U 
DKn 
= IF(Q2>0,(R2+S2*EXP(T2*M2))*$A$15,0) 
V 
Knc 
= IF(Q2>0,(0.8860.122*M2+0.0121*(M2)A20.000653 *(M2)A3+0.000014*(M2)A4),0) 
W 
Model DNI 
= IF(Q2>0,G2*(V2U2),0) 
Note: Columns B to F may use either specific, noncontinuous values or be filled as serially complete to the extent needed. Column N is the required user value for global horizontal total hemispherical irradiance.
Leave a reply