Principal Investigator
Dr. Yousef A. Al-Rumikhani
Natural Resources & Environment Research Institute
King Abdulaziz City for Science and Technology,
P.O.Box 6086, Riyadh-11442, Kingdom of Saudi Arabia
CHAPTER 1 – SOFTWARE DESIGN
INTRODUCTION
The “EVAPO SAUDIA” program provides standardized calculations of reference
evapotranspiration (ET) by ten methods commonly in use. The primary purposes
of this software are to:
 Provide standardized reference ET calculations for the different agroclimatic regions of Saudi Arabia.
 Provide the accurate reference ET by selecting different ETO methods for
different climatic conditions.
 Formation of climatic database, its utilization for the more reliable ET O and
selection of suitable ETO equations for different climatic regions.
 Provide the monthly reference ET contour maps of Saudi Arabia.
 Graphical representation of reference ET and table for a weather station.
 Interpolation of monthly reference ET values for a non-weather station
place.
Whilst every effort has been made to ensure the validity of the algorithms used in
the calculation equations, the accuracy of the calculated evapotranspiration
depends upon the accuracy of the input data measurement, setting of the weather
station and relevance of the chosen evapotranspiration calculation method.
KACST takes no responsibility for matters arising from the application of the
results of this program.
Dr. Yousef A. Al-Rumikhani
The program is designed to use the mean monthly climate data base (Microsoft
access file) of the available weather stations in the Kingdom of Saudi Arabia. The
user can select whole country to see reference ET contour map of Saudi for a
certain month, can select a weather station to see reference ET graphically
through whole year and can enter the coordinates of certain palace away from the
weather stations, to see reference ET for a month. The software can compute
reference ET on monthly basis and computations are presented as mm/day.
The EVAPO SAUDIA is written in Visual Basic Version 6.0, Professional
Edition. It runs on computers that have Windows 95, 98, ME, NT, 2000 or XP
operating systems. The screen resolution must be set to 800 x 600 of higher.
Screen resolutions of 640 x 480 will not show the entire data-tables, bar charts or
contour map screens.
The basic algorithms and routines used in this program are taken from the Food
and Agriculture Organization of the united Nation (FAO) reports FAO-24 and
FAO-56, ASCE and FAO reports/papers available on internet.
1.1.2 Main structure of the program
EVAPO SAUDIA
VERSION 1.0
Location Selection ListBox (LSL)
 Whole Country
0
 Weather Station
1
 Enter Location Coordinates
2
0
LSL
Subroutine EQLIST
1
Weather
Station
Selection
Table
Subroutine
OK
N
Subroutine EQLIST
Contour
Map
Y
Table
2
Enter
o Latitude
o Longitude
Month
Selection
Subroutine EQLIST
Suroutine Msele
Month
Selection
Subroutine
OK
N
Bar
Graph
ETo
Value
Y
Bar
Graph
Subroutine
OK
Contour
Map
Subroutine
OK
Subroutine
OK
Subroutine EQLIST
List Box Selection for Ten
ETo Equation
Must Select one Equation
1
Subroutine PMANFAO24
2
Subroutine PMONT
3
Subroutine PENMODIF
Equation
4
Subroutine HARGREAVES
Equation
5
Subroutine PRIESTLY
Equation
6
Subroutine BLANCRID
Equation
7
Subroutine JENSEN
Equation
Equation
Equation
Equation
8
Subroutine PEVAPO
9
Subroutine RADIATION
Main Database
TABLE NAME: Location
Structure of Table
STATION-NAM
REGION
AGENCY
LONGITUDE
LATITUDE
ALTITUDE
STATION_ID
CODE
Description: The Location Table having eight fields. The station name field contains all the
stations The region field holds all the regions The agency field have name of the agency. There
are two agencies MOA and MET.MOA stands for ministry of Agriculture. MET stands for
Metallurgical department. The table consists the corresponding Longitude, Latitude and
Altitude. For that stations. The Longitude, Latitude defined in degrees where as altitude in
meters. The code was generated based on Latitude, longitude and Agency name
TABLE NAME: PANEVAPO
Structure of Table:
CODE
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
PANM
PAN
CASE
Description: The panevporation table having 15 fields. The code was generated based on
Latitude, longitude and Agency name. The JAN-DEC fields having the mean monthly data of
pan evaporation.
TABLE NAME: Rainfall
Structure of Table:
CODE
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
Description: The Rainfall table having 13 fields. The code was generated based on Latitude,
longitude and Agency name. The JAN-DEC fields having the mean monthly data of rainfall
from January to December
TABLE NAME: RH
Structure of Table:
CODE
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
Description: The RH table having 13 fields. The code was generated based on Latitude,
longitude and Agency name. The JAN-DEC fields having the mean monthly data of Relative
Humidity (%) from January to December
TABLE NAME: SolRadi
Structure of Table:
CODE
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
Description: The SolRadi table having 13 fields. The code was generated based on Latitude,
longitude and Agency name. The JAN-DEC fields having the mean monthly data of Solar
Radiation from January to December
TABLE NAME: SShine
Structure of Table:
CODE
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
Description: The SShine table having 13 fields. The code was generated based on Latitude,
longitude and Agency name. The JAN-DEC fields having the mean monthly data of Relative
Sunshine from January to December
TABLE NAME: Tmx
Structure of Table:
CODE
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
Description: The Tmx table having 13 fields. The code was generated based on Latitude,
longitude and Agency name. The JAN-DEC fields having the mean monthly data of
Temperature Maximum January to December
TABLE NAME: Tmn
Structure of Table:
CODE
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
Description: The Tmn table having 13 fields. The code was generated based on Latitude,
longitude and Agency name. The JAN-DEC fields having the mean monthly data of
Temperature minimum from January to December
TABLE NAME: Wind
Structure of Table:
CODE
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
Description: The Wind table having 13 fields. The code was generated based on Latitude,
longitude and Agency name. The JAN-DEC fields having the mean monthly data of wind from
January to December
1.2.2 Data Structure of Database
Table Name: Location
Field Name
STATION
NAME
REGION
AGENCEY
LONGITUDE
LATITUDE
ALTITUDE
STATION-ID
CODE
Data
Type
Text
Description
Size
Name of the weather station
50 Characters
Text
Text
Region of the Saudi Arabia
MOA= Ministry of Agriculture,
MET=Metallurgical Dept.
Longitude Degrees
Latitude Degrees
Above sea level (m)
Agency Identification number
Generated based on Latitude, Longitude and
50 Characters
50 Characters
Number
Number
Number
Text
Number
Long Integer
Long Integer
Long Integer
50 characters
Long Integer
Agency Identification Number
Description:
The Location table having eight fields. The Station name field contains all the stations .The
region field holds all the regions. The Agency field have name of the agency. There are two
agencies MOA and MET.MOA stands for Ministry of Agriculture, MET stands for
Metallurgical department. The table consists the corresponding Longitude, Latitude and
Altitude for that stations.friday The Longitude, Latitude defined in degrees where as Altitude in
meters. The station identification number optimized from the agency. The code was generated
based on Latitude, Longitude and Agency name.
Table Name: PANEVAPO
Design of the Pan Evaporation Table:
Field Name
CODE
Data Type
Text
JAN
Number
FEB
MAR
APR
MAY
JUN
JUL
AUG
Number
Number
Number
Number
Number
Number
Number
SEP
Number
OCT
Number
NOV
Number
DEC
Number
PANM
PANCASE
Number
Text
Table Name: Rainfall
Description
Generated based on Latitude, Longitude and
Agency Identification Number
January mean monthly data of pan
evaporation
March mean monthly data of pan evaporation
April mean monthly data of pan evaporation
May mean monthly data of pan evaporation
June mean monthly data of pan evaporation
July mean monthly data of pan evaporation
June mean monthly data of pan evaporation
August mean monthly data of pan
evaporation
September mean monthly data of pan
evaporation
October mean monthly data of pan
evaporation
November mean monthly data of pan
evaporation
December mean monthly data of pan
evaporation
PAN Category
PAN Case
Width of Field
50 characters
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
50 Characters
Design of the Rainfall Table:
Field Name
CODE
Data Type
Text
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Number
Number
Number
Number
Number
Number
Number
Number
Number
Number
Number
Number
Description
Generated based on Latitude, Longitude and
Agency Identification Number
January mean monthly data of rainfall
February mean Monthly data of rainfall
March mean Monthly data of rainfall
April mean monthly data of rainfall
May mean Monthly data of rainfall
June mean Monthly data of rainfall
July mean Monthly data of rainfall
August mean mean Monthly data of rainfall
September mean Monthly data of rainfall
October mean Monthly data of rainfall
November mean Monthly data of rainfall
December mean Monthly data of rainfall
Width of Field
50 characters
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Table Name: RH
Design of the Relative Humidity Table:
Field Name
CODE
Data Type
Text
JAN
Number
FEB
MAR
Number
Number
APR
Number
MAY
JUN
JUL
AUG
SEP
Number
Number
Number
Number
Number
OCT
Number
NOV
Number
DEC
Number
Description
Generated based on Latitude, Longitude and
Agency Identification Number
January mean Monthly data of relative
humidity
Monthly mean data of relative humidity
February mean Monthly data of relative
humidity
March mean Monthly data of relative
humidity
April mean Monthly data of relative humidity
May mean Monthly data of relative humidity
June mean Monthly data of relative humidity
July mean Monthly data of relative humidity
August mean Monthly data of relative
humidity
September mean Monthly data of relative
humidity
November mean Monthly data of relative
humidity
December mean Monthly data of relative
humidity
Width of Field
50 characters
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Table Table: SolRadi
Design of the Solar Radiation Table:
Field Name
CODE
Data Type
Text
JAN
FEB
Number
Number
MAR
APR
MAY
JUN
JUL
AUG
SEP
Number
Number
Number
Number
Number
Number
Number
OCT
NOV
Number
Number
DEC
Number
Description
Generated based on Latitude, Longitude and
Agency Identification Number
January mean Monthly data of solar radiation
February mean Monthly data of solar
radiation
March mean Monthly data of solar radiation
April mean Monthly data of solar radiation
May mean Monthly data of solar radiation
June mean Monthly data of solar radiation
July mean Monthly data of solar radiation
August mean Monthly data of solar radiation
September mean Monthly data of solar
radiation
October mean Monthly data of solar radiation
November mean Monthly data of solar
radiation
December mean Monthly data of solar
radiation
Width of Field
50 Characters
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Table Name: SShine
Design of the Sun Shine Table:
Field Name
CODE
Data Type
Text
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
Number
Number
Number
Number
Number
Number
Number
Number
Number
Number
Description
Generated based on Latitude, Longitude and
Agency Identification Number
January mean Monthly data of sunshine
February mean Monthly data of sunshine
March mean Monthly data of sunshine
April mean Monthly data of sunshine
May mean Monthly data of sunshine
June mean Monthly data of sunshine
July mean Monthly data of sunshine
August mean Monthly data of sunshine
September mean Monthly data of sunshine
October mean Monthly data of sunshine
Width of Field
50 characters
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
NOV
DEC
Number
Number
November mean Monthly data of sunshine
December mean Monthly data of sunshine
Long Integer
Long Integer
Table Name: Tmx
Design of Temperature Maximum Table:
Field Name
CODE
Data Type
Text
JAN
Number
FEB
Number
MAR
Number
APR
Number
MAY
Number
JUN
Number
JUL
Number
AUG
Number
SEP
Number
OCT
Number
NOV
Number
DEC
Number
Description
Generated based on Latitude, Longitude and
Agency Identification Number
January mean Monthly data of maximum
temperature
February mean Monthly data of maximum
temperature
March mean Monthly data of maximum
temperature
April mean Monthly data of maximum
temperature
May mean Monthly data of maximum
temperature
June mean Monthly data of maximum
temperature
July mean Monthly data of maximum
temperature
August mean Monthly data of maximum
temperature
September mean Monthly data of maximum
temperature
October mean Monthly data of maximum
temperature
November mean Monthly data of maximum
temperature
December mean Monthly data of maximum
temperature
Width of Field
50 Characters
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Table Name: Tmin
Design of the Temperature Minimum Table:
Field Name
CODE
Data Type
Text
JAN
Number
FEB
Number
MAR
Number
APR
Number
MAY
Number
JUN
Number
JUL
Number
AUG
Number
SEP
Number
OCT
Number
NOV
Number
DEC
Number
Table Name: Wind
Description
Generated based on Latitude, Longitude and
Agency Identification Number
January mean Monthly data of minimum
temperature
February mean Monthly data of minimum
temperature
March mean Monthly data of minimum
temperature
April mean Monthly data of minimum
temperature
May mean Monthly data of minimum
temperature
June mean Monthly data of minimum
temperature
July meanMonthly data of minimum
temperature
August meanMonthly data of minimum
temperature
September mean Monthly data of minimum
temperature
October mean Monthly data of minimum
temperature
November mean Monthly data of minimum
temperature
December meanMonthly data of minimum
temperature
Width of Field
50 Characters
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Design of Wind Table:
Field Name
CODE
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Data Type
Text
Number
Number
Number
Number
Number
Number
Number
Number
Number
Number
Number
Number
Description
January mean Monthly data of wind speed
February mean Monthly data of wind speed
March mean Monthly data of wind speed
April mean Monthly data of wind speed
May mean Monthly data of wind speed
June mean Monthly data of wind speed
July mean Monthly data of wind speed
August mean Monthly data of wind speed
September mean Monthly data of wind speed
October mean Monthly data of wind speed
November mean Monthly data of wind speed
December mean Monthly data of wind speed
Width of Field
50 characters
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
Long Integer
1.2.3 Data structure of subroutine Tables
Data structure of Subroutine Table-B
n/N
0
20
0
0.2
0.4
0.6
0.8
1.0
40
RHmin %
60
80
100
U2 day = 0 m/sec
Refrence: Crop water requirements, FAO24, table 1, page 110, by Pruitt and Doorenbos (1977)
Description:
The values for 'a' and 'b' of the relationship ETo = a + b p(0.46T + 8) are given for 'b' in above
table for different levels of RHmin,n/N,and Uday.The computer program uses the table 'b'
values is included in the program and interpolates between the different ranges of
RHmin,n/N,Uday.
RHmin – Relative Humidity
n/N – Sunshine hour's
Uday - Day time wind conditions
Data structure of subroutine Table-P
Months
Latitude
00
Latitude
50
Latitude
100
Latitude
150
Latitude
200
Latitude
250
Latitude
300
Latitude
350
Latitude
400
Latitude
450
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
NOV
DEC
Reference: Crop water requirements, FAO24, table 1, page 6.
Description:
The value for p of the relationship ETo = a + b p (0.46T + 8).the above table contains mean
daily percentage (P) of annual day time hours for different latitudes
Data Structure of Subroutine Table - C
RHmax = 30%
3
6
9 12
Rs mm/day
Uday m/sec
RHmax = 60%
3
6
9 12
RHmax = 90%
3
6
9 12
Uday/Unight =4.0
0
3
6
9
Uday/Unight =3.0
0
3
6
9
Uday/Unight =2.0
0
3
6
9
Uday/Unight =1.0
Reference: Crop water requirements, FAO24, table 16, page28
Latitude
500
Description: The above table presents the value of 'c' for different conditions of RHmax, Rs,
Uday and Uday/Unight.
Data Structure of Subroutine Table - W
Temperature 0 C 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
W at altitude
m
0
500
1 000
2 000
3 000
4 000
Reference: Crop water requirements, FAO24, table 9, page24
Description: The values of Weighting Factor (w) for the Effect of radiation on ETo different
Temperatures and altitudes
Data Structure of Subroutine Table - C
RHmax = 30%
3
6
9 12
Rs mm/day
Uday m/sec
RHmax = 60%
3
6
9 12
RHmax = 90%
3
6
9 12
Uday/Unight =4.0
0
3
6
9
Uday/Unight =3.0
0
3
6
9
Uday/Unight =2.0
0
3
6
9
Uday/Unight =1.0
Reference: Crop water requirements, FAO24, table 16, page28
Description: The above table presents the value of 'c' for different conditions of RHmax, Rs,
Uday and Uday/Unight.
Data Structure of Subroutine Table - W
Temperature 0 C 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
W at altitude
m
0
500
1 000
2 000
3 000
4 000
Reference: Crop water requirements, FAO24, table 9, page24
Description: The values of Weighting Factor (w) for the Effect of radiation on ETo different
Temperatures and altitudes
1.2.4 Algorithms of subroutine Tables
This subroutine (Table-P) is calling under Balney-Criddle Method.
Open "c:\Table-P.dat" For Input As #1
For i = 1 To 12
For j = 0 To 10
Input #1, P(i, j)
Next j
Next i
Close (1)
This subroutine (Table-B) is calling under Blany-Criddl Methoed
Open "c:\Table-B.dat" For Input As #2
For i = 1 To 36
'Solar Radiations * Wind at 2 m
For j = 0 To 5
'Relative Humidity
Input #2, B(i, j)
Next j
Next i
Close (2)
This Subroutine (Table-W) is calling under Corrected Penman FAO24.
Open "c:\Table-W.dat" For Input As #4
For j = 0 To 4
For i = 1 To 20
Input #4, fW(i, j)
Next i
Next j
Close (4)
This Subroutine (Table-C) is calling under Corrected Penman FAO24.
Open "c:\table-c.dat" For Input As #5
For j = 1 To 16
For i = 1 To 12
Input #5, c(i, j)
Next i
Next j
Close (5)
1.2.5 Flowchart of subroutine Table
1.2.6 Arrangement of used subroutine t in Program
SubRoutine
Subroutine Equations
Month_sele
Main ETo
X
Stn_select
X
CmdExit_click
X
Eqnlist_click
X
PMANFAO24
X
PMONT
X
PENMODIF
X
HARVEGES
X
PRISTELY
X
BLANCRID
X
BLANIModif
X
JENSEN
X
Form_load
X
Mselect_click
X
Interpol
X
Methodsele_click
X
Equation_list
X
LLCmdok_click
X
ERRload
X
Eqn_seled
X
Month_seltd
X
Interpola
X
TxtLati_change
X
TxtLatim_change
X
Txtlong_change
X
TxtlongM_change
X
Cmdok_click
X
X
X
Form_load
X
X
X6
Form_load1
X
ReForm(ea,Eb)
X
X
X
ReFormI(ea,Eb)
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
PMexit_click
X
Old_Form
X
X
Old_Form1
OLD1
Form_OldFo
X
Barchat
Bar chart
X
X
X
X
X
X
X
X
X
Contour Map
X
X
X
X
X
X
X
X
X
Description:
The above Table describing the arrangement of the subroutines in
evaporation pogram. It has subroutine names in rows and subroutine
equations in coloums. The Main ETo file of the pogram calling the 18
subroutines.
The 'X' mark indicates that where the subroutine is calling in
the evaporation program.
1.2.7 Arrangement of used subroutine tables in Program
SubRoutine
Tables
Subroutine Equations
PMANFAO24
PMONT
PENMODIF
Table-P.dat
Table-B.dat
HARVEGES
PRISTELY
BLANCRID
BLANIModif
X
JENSEN
X
PEVAPO
RADIATION
X
Table-W.dat
X
Table-C.dat
X
X
Pantable
X
X
X
Description:
The above Table describing the arrangement of the subroutine Tables in
evaporation pogram. It has subroutine. Tables in rows and subroutine equations in
coloums.The 'X' mark indicates that where the subroutine Table is calling in the
evaporation program.
1.2.8 Arrangements of used database in program
Main
Database
LOCATION
Subroutine Equations
PMANFAO24
PMONT
PENMODIF
HARVEGES
PRISTELY
BLANCRID
BLANIModif
JENSEN
PEVAPO
RADIATION
X
X
X
X
X
X
X
X
X
X
PANEVAPO
X
RH
X
X
X
X
SShine
X
X
X
X
X
Tmx
X
X
X
X
X
X
Tmn
X
X
X
X
SR
X
X
X
X
Wind
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
SAUDIARABIA CONTOURING
1.3.1 Flowchart of subroutine contour map
Subroutine
Contour Map
ETo Equations
Result
Weather Station
Latitude, Longitude,
ETo monthly values
Initialize
Database file
EToSA.dbf
Month Selection
Subroutine
Month List Box
Select a Month
ASCII file GRDdat
Latitude, Longitude,
Selected Month ETo
Database
EToSA.dbf
Rows = 250
Columns = 250
MinX = 12
MaxX = 33
MinY = 34
MaxY = 60
21
SURFER
GrdDat.dat
TO
Temp.grd
Application
Girding
SURFER
Temp.grd
TO
Saudia.grd
Application
Blanking
CONTOUR
Saudia.grd
TO
Temp.dat
VIEW ASCII
FILE
Subroutine
ContourMap
View
Contour
Map
1.3.2 Explanation of the subroutine contour map
Subroutine
Contour Map
This program generates a contour map for the Saudi Arabia with surfer application for the
selected months with the result of ETo equations
ETo Equations Result:
ETo Equations
Result
The monthly ETo results are coming from one out of ten equations and the out put will be in
millimeters. The ten equations are:
a) Corrected Penman Method FAO-24
b) Penman modified (Penman 1948,1963)
c) Penman Monteith FAO-56
d) Hargreaves Temperature Method
e) Jensen-Haise Method
f) Blaney-criddle Method
g) Blaney-Modified FAO-24
h) Priestly-Taylor Method
i) Pan Evaporation FAO-24
j) Radiation Method FAo-24
ETo Calculation by panman Monteith (FAO 56) formula for Kingdom of Saudi Arabia
Latitude
42.39
40.06
Longitude
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
SEP
OCT
A Temporary database file will be created with a Longitude(X), Latitude(Y) and ETo result (Z)
from the stored data base of weather station
Weather Station
Initialize
Database file
EToSA.dbf
Latitude, Longitude,
ETo monthly values
XYZ data files contain the raw data interpreted by Surfer when producing a grid [.GRD] file.
XYZ data files are organized in Column and Row format. By default Surfer expects the X data
to be contained in column A, the Y data in Column B, and the Z data in Column C.
Row 2 Row 3 Row 4 Row 5 Row 6 Row 7 -
D
18.14 1.993 2.045 3.375 4.851 5.460 6.903 6.257 5.717 5.O54 3.600 2.145 1.7
29.47 2.177 3.145 5.030 7.610 8.495 10.35 10.84 9.545 8.282 5.780 3.602 2.0
Initialize Database file:
Row 1
NOV
Column A
Column B
Column C
Longitude(X)
Latitude(Y)
Elevation (Z)
Row 8 -
Month selection subroutine
Month selection is a subroutine pogram to select a month from month list box (January to
December)to create a contour map for Saudi Arabia based on the ETo result
Month Selection
Subroutine
Month List Box
Select a Month
SURFER APPLICATION:
Surfer application converts the location of weather station (X,Y,Z) into Grid Mesh (250rowes
x 250coloums ) and remove the points out side Saudi Arabia boundery Surfer converts X,Y,Z
devided in to 250 x 250 grid points
(MaxX, MinY)
(330, 340)
(MaxX, MaxY
(330, 600)
(MinX, MinY)
(120, 340)
(MaxX, Max
(120, 600)
Latitude (X) = 12 to 33 degrees
Longitude(Y) =34 to 66 degrees
Minimum Latitude=MinX
Maximun Latitude=MaxX
Minimum Longitude=MinY
Minimum Longitude=MaxX
ASCII file GRD.dat
Latitude, Longitude,
Selected month ETo
Database
EToSA.dbf
Rows = 250
Columns = 250
MinX = 12
MaxX = 33
MinY = 34
MaxY = 60
Gridding of Saudi Arabia Map:
Gridding processes which trace from irregular space location data into equally space grid node
of Saudi Arabia. The location data of weather station is not equally spaced. To make a contour
map for weather station gridding is needed. The temporary data of Longitude, Latitude and ETo
result [DAT] file is in ASCII format converts into grid nodes
The density of grid refers to the rows and columns in a grid file. The X, Y, Z values between
Longitude (120 to 350North), Latitude (340 to 600) and converts into (250 rows and 250
columns) equally spaced data. This temporary created GrdDat.dat file converts into binary
format as Temg.ged file.
GrdDat.dat
TO
Temp.grd
SURFER
Application
Girding
Blanking for Saudi Arabia out side boundary:
Blanking application removes the node pointes of the gird out side of the Saudia boundary and
store into new saudia boundary and store into binary format.
The blanking procedure modifies by placing a special blanking value for each grid node that
lines with in the area to be blanked. It uses the Temp.grd file and modified as saudia.grd file
that contain only node points of inside Saudi Arabia.
SURFER
Temp.grd
TO
Saudia.grd
Application
Blanking
Contour converts blanked grid file into the ASCII format. The values uses for the input of
contour subroutine. The contour subprogram uses the saudi.grd file as input and converts
Temp.dat file. The program converting binary format to ASCII format and it is temporary file.
CONTOUR
Saudia.grd
TO
Temp.dat
VIEW ASCII
FILE
Subroutine Contour map of Saudi Arabia:
Contour subroutine map reads the data file and draw a map for Saudi Arabia. The program
generate the contour map for the selected month based on the ETo equation .The program draw
a contour map on screen for the select month estimated by ETo equations .It shows the
variation of the Eto values at different weather stations
View
Contour
Map
CHAPTER2 – EVAPORATION EQUATIONS OF
PROGRAMS
Subroutine PMONT
CropHeight = 12 'Crop Height
TempHumid = 190 'Height temperature and humidity measurements
CropHgtWnd = 200 'Wind speed measured at Crop Height
AerDynResist = Log((CropHgtWnd - 0.667 * CropHeight) / (0.123 * CropHeight)) *
Log((TempHumid - 0.667 * CropHeight) / (0.0123 * CropHeight)) / (0.41) ^ 2
AeroTCoeff = 0.622 * 3.486 * 86400 / (AerDynResist * 1.01)
pi = 3.141592654
SWa = 0.25
'Short Wave Radiations
SWb = 0.5
'Short Wave Radiations
Alpha = 0.23
'Albedo
LWa = 0.9
'LongWave Radiations
LWb = 0.1
'LongWave Radiations
LWal = 0.34
'LongWave Radiations Albedo
LWbl = -0.139 'LongWave Radiations Albedo
'Label1.Caption = "Radiant = " + Format (radiant, "####.####")
'Label2.Caption = "AeroTCoeff = " + Format(AeroTCoeff, "####.##")
For j = 1 To TotalStn
If MainETo.StnAlone = 1 Then
radiant = Lati * pi / 180
Else
radiant = LatiR(j) * pi / 180
End If
If MainETo.StnAlone <> 1 Then
For i = 1 To 12
Tmx(i) = TmxR(j, i)
Tmn(i) = TmnR(j, i)
RHm(i) = RHmR(j, i)
Wnd(i) = WndR(j, i)
SS(i) = SSR(j, i)
SR(i) = SRR(j, i)
RF(i) = RFR(j, i)
PE(i) = PER(j, i)
Next i
Lati = LatiR(j)
Longi = LongiR(j)
Elev = ElevR(j)
End If
For i = 1 To 12
AvgT(i) = (Tmx(i) + Tmn(i)) / 2
Wind(i) = Wnd(i) / 86.4
EaTn(i) = 0.61078 * Exp(17.27 * Tmn(i) / (Tmn(i) + 237.3))
EaTx(i) = 0.61078 * Exp(17.27 * Tmx(i) / (Tmx(i) + 237.3))
EaTxTn(i) = (EaTx(i) + EaTn(i)) / 2
Edew(i) = RHm(i) / (50 / EaTx(i) + 50 / EaTn(i))
RHmean(i) = Edew(i) / EaTx(i) * 100
RHdel(i) = Edew(i) / EaTx(i) / 2 + Edew(i) / EaTn(i) / 2
ETxTn(i) = 2049 * EaTx(i) / (Tmx(i) + 237.3) ^ 2 + 2049 * EaTn(i) / (Tmn(i) + 237.3) ^ 2
Patm(i) = 101.3 * ((293 - 0.0065 * Elev) / 293) ^ 5.253
Lambda(i) = 2.501 - (0.002361 * AvgT(i))
Gamma(i) = 0.0016286 * Patm(i) / Lambda(i)
rc(i) = 70 'For Grass, 86 for Alfalfa (rc-> Canopy resistance
Ra(i) = AerDynResist / Wind(i)
GammaP(i) = Gamma(i) * (1 + rc(i) / Ra(i))
DlGm(i) = ETxTn(i) / (ETxTn(i) + GammaP(i))
GmDgm(i) = Gamma(i) / (ETxTn(i) + GammaP(i))
Aeroterm(i) = GmDgm(i) * Wind(i) * AeroTCoeff * (EaTxTn(i) - Edew(i)) / (AvgT(i) +
273)
Dayno(i) = (30.5 * i - 14.6)
Soldeclin(i) = Sin(((2 * pi * Dayno(i) / 365) - 1.39)) * 0.4093
xx(i) = Sin(Soldeclin(i)) * Sin(radiant)
yy(i) = Cos(Soldeclin(i)) * Cos(radiant)
temp1 = -Tan(Soldeclin(i) * Tan(radiant))
Omega(i) = Atn(-temp1 / Sqr(-temp1 * temp1 + 1)) + 2 * Atn(1) 'ArcCos function define
Dr(i) = (1 + 0.033 * Cos((2 * pi / 365) * Dayno(i)))
RAa(i) = 37.586 * Dr(i) * (Omega(i) * xx(i) + Sin(Omega(i)) * yy(i))
N1(i) = 24 / pi * Omega(i)
NbyN(i) = SS(i) / N1(i)
Rns(i) = (1 - Alpha) * RAa(i) * (SWa + SWb * NbyN(i))
FNbyN(i) = (LWb + LWa * NbyN(i))
Sigma(i) = 0.00000000245 * ((Tmx(i) + 273) ^ 4 + (Tmn(i) + 273.16) ^ 4)
Emissivity(i) = LWal + LWbl * Sqr(Edew(i))
Rbo(i) = 0.00000000245 * (LWal + LWbl * Sqr(Edew(i))) * (((Tmx(i) + 273.16) ^ 4 +
(Tmn(i) + 273.16) ^ 4))
LWR(i) = Rbo(i) * (LWb + LWa * NbyN(i))
RnsRl(i) = Rns(i) - LWR(i)
Next i
AvgT(0) = AvgT(12)
For i = 1 To 12
G(i) = 0.14 * (AvgT(i) - AvgT(i - 1))
RnG(i) = RnsRl(i) - G(i)
RadTm(i) = DlGm(i) * RnsRl(i) / Lambda(i)
RadTmG(i) = DlGm(i) * RnG(i) / Lambda(i)
ETcomb(i) = RadTm(i) + Aeroterm(i)
ETG(i) = RadTmG(i) + Aeroterm(i)
ETGptg(i) = (ETcomb(i) - ETG(i)) / ETcomb(i)
ETos(i) = ETG(i)
EToSA(j, i) = ETG(i)
Next i
Next j
Subroutine PMANFAO24
CropHeight = 12 'Crop Height
TempHumid = 190 'Height temperature and humidity measurements
CropHgtWnd = 200 'Wind speed measured at Crop Height
AerDynResist = Log((CropHgtWnd - 0.667 * CropHeight) / (0.123 * CropHeight)) *
Log((TempHumid - 0.667 * CropHeight) / (0.0123 * CropHeight)) / (0.41) ^ 2
AeroTCoeff = 0.622 * 3.486 * 86400 / (AerDynResist * 1.01)
pi = 3.141592654
SWa = 0.25
'Short Wave Radiations
SWb = 0.5
'Short Wave Radiations
Alpha = 0.23
'Albedo
LWa = 0.9
'LongWave Radiations
LWb = 0.1
'LongWave Radiations
LWal = 0.34
'LongWave Radiations Albedo
LWbl = -0.139 'LongWave Radiations Albedo
radiant = Lati * pi / 180
albedo = 0.25 ' for grass
a0 = 0.6817
A1 = 0.0027864
A2 = 0.0181768
a3 = -0.0682501
a4 = 0.0126514
a5 = 0.0097297
a6 = 0.000043025
a7 = -0.000000092118
k = 0.41
R = 287 'J/kg/K
Gravity = 9.81 ' m/s2
TK0 = 293.16 'K
Azero = 0 'meter
lapserate = 0.0065 'K/m
Pzero = 101.3 'KPa
Open "c:\Table-W.dat" For Input As #4
For j = 0 To 4
For i = 1 To 20
Input #4, fW(i, j)
Next i
Next j
Close (4)
Open "c:\table-c.dat" For Input As #5
For j = 1 To 16
For i = 1 To 12
Input #5, c(i, j)
Next i
Next j
Close (5)
'Open "c:\TestFAO24.txt" For Output As #6
For j = 1 To TotalStn
If MainETo.StnAlone <> 1 Then
radiant = LatiR(j) * pi / 180
Else
radiant = Lati * pi / 180
End If
For i = 1 To 12
AvgT(i) = (Tmx(i) + Tmn(i)) / 2
Wind(i) = Wnd(i) / 86.4
EaTn(i) = 0.61078 * Exp(17.27 * Tmn(i) / (Tmn(i) + 237.3))
EaTx(i) = 0.61078 * Exp(17.27 * Tmx(i) / (Tmx(i) + 237.3))
ea(i) = (EaTx(i) + EaTn(i)) / 2
EaTxTn(i) = (EaTx(i) + EaTn(i)) / 2
Edew(i) = RHm(i) / (50 / EaTx(i) + 50 / EaTn(i))
Ed(i) = Edew(i)
'RHmax
RHmax(i) = Edew(i) / EaTn(i) * 100
RHmean(i) = Edew(i) / EaTx(i) * 100
RHdel(i) = Edew(i) / EaTx(i) / 2 + Edew(i) / EaTn(i) / 2
ETxTn(i) = 2049 * EaTx(i) / (Tmx(i) + 237.3) ^ 2 + 2049 * EaTn(i) / (Tmn(i) + 237.3) ^
2
Patm(i) = 101.3 * ((293 - 0.0065 * Elev) / 293) ^ 5.253
'Lambda(i) = 2.501 - (0.002361 * AvgT(i))
Gamma(i) = 0.006595 * Patm(i)
'Gamma(i) = 0.0016286 * Patm(i) / Lambda(i)
rc(i) = 70 'For Grass, 86 for Alfalfa (rc-> Canopy resistance
Ra(i) = AerDynResist / Wind(i)
GammaP(i) = Gamma(i) * (1 + rc(i) / Ra(i))
DlGm(i) = ETxTn(i) / (ETxTn(i) + GammaP(i))
GmDgm(i) = Gamma(i) / (ETxTn(i) + GammaP(i))
Aeroterm(i) = GmDgm(i) * Wind(i) * AeroTCoeff * (EaTxTn(i) - Edew(i)) / (AvgT(i) +
273)
Dayno(i) = (30.5 * i - 14.6)
Soldeclin(i) = Sin(((2 * pi * Dayno(i) / 365) - 1.39)) * 0.4093
xx(i) = Sin(Soldeclin(i)) * Sin(radiant)
yy(i) = Cos(Soldeclin(i)) * Cos(radiant)
temp1 = -Tan(Soldeclin(i) * Tan(radiant))
Omega(i) = Atn(-temp1 / Sqr(-temp1 * temp1 + 1)) + 2 * Atn(1) 'ArcCos function
define
Dr(i) = (1 + 0.033 * Cos((2 * pi / 365) * Dayno(i)))
RAa(i) = 37.586 * Dr(i) * (Omega(i) * xx(i) + Sin(Omega(i)) * yy(i))
'Uday
N1(i) = 24 / pi * Omega(i)
'UDay/UNight ratio
NbyN(i) = SS(i) / N1(i)
'Rns(i) = (1 - albedo) * SR(i) / 2.45
Rnl(i) = albedo * (Tk ^ 4) * (7.723 - (10 * Edew(i)) ^ 0.5) * (0.1 + 0.9 * NbyN(i))
'RS
Rns(i) = (1 - Alpha) * RAa(i) * (SWa + SWb * NbyN(i))
FNbyN(i) = (LWb + LWa * NbyN(i))
If RHmax(i) > 0 And RHmax(i) < 45 Then RH = 45
If RHmax(i) >= 45.01 And RHmax(i) < 75 Then RH = 60
If RHmax(i) >= 75.01 Then RH = 90
If FNbyN(i) < 1.5 Then Unight = 1
If FNbyN(i) >= 1.5 And FNbyN(i) < 2.5 Then Unight = 2
If FNbyN(i) >= 2.5 And FNbyN(i) < 3.5 Then Unight = 3
If FNbyN(i) >= 3.5 Then Unight = 4
If SR(i) > 0 And SR(i) < 4.5 Then SolR = 3
If SR(i) >= 4.5 And SR(i) < 7.5 Then SolR = 6
If SR(i) >= 7.5 And SR(i) < 10.5 Then SolR = 9
If SR(i) >= 10.5 Then SolR = 12
If N1(i) >= 0 And N1(i) < 1.5 Then Uday = 0
If N1(i) >= 1.5 And N1(i) < 4.5 Then Uday = 3
If N1(i) >= 4.5 And N1(i) < 7.5 Then Uday = 6
If N1(i) >= 7.5 Then Uday = 9
xin = (RH / 30 - 1) * 4 + SolR / 3
yin = (4 - Unight) * 4 + (Uday / 3 + 1)
'************************************
Altitude = Int(Elev / 500) * 500
TempC = Int(AvgT(i) / 2#) * 2
'************************************
FWnd = 0.27 * (1 + Wnd(i) / 100)
'************************************
Rn(i) = Rns(i) - Rnl(i)
'************************************
ETos(i) = c(xin, yin) * (fW(TempC / 2, Altitude / 500) * Rn(i) + (1 - fW(TempC / 2,
Altitude / 500)) * (ea(i) - Ed(i)))
EToSA(j, i) = ETos(i)
Next i
Next j
Subroutine PENMODIF\
CropHeight = 12 'Crop Height
TempHumid = 190 'Height temperature and humidity measurements
CropHgtWnd = 200 'Wind speed measured at Crop Height
AerDynResist = Log((CropHgtWnd - 0.667 * CropHeight) / (0.123 * CropHeight)) *
Log((TempHumid - 0.667 * CropHeight) / (0.0123 * CropHeight)) / (0.41) ^ 2
AeroTCoeff = 0.622 * 3.486 * 86400 / (AerDynResist * 1.01)
pi = 3.141592654
SWa = 0.25
'Short Wave Radiations
SWb = 0.5
'Short Wave Radiations
Alpha = 0.23
'Albedo
LWa = 0.9
'LongWave Radiations
LWb = 0.1
'LongWave Radiations
LWal = 0.34
'LongWave Radiations Albedo
LWbl = -0.139 'LongWave Radiations Albedo
'Label1.Caption = "Radiant = " + Format(radiant, "####.####")
'Label2.Caption = "AeroTCoeff = " + Format(AeroTCoeff, "####.##")
radiant = Lati * pi / 180
albedo = 0.25 ' for grass
a0 = 0.6817
A1 = 0.0027864
A2 = 0.0181768
a3 = -0.0682501
a4 = 0.0126514
a5 = 0.0097297
a6 = 0.000043025
a7 = -0.000000092118
k = 0.41
R = 287 'J/kg/K
Gravity = 9.81 ' m/s2
TK0 = 293.16 'K
Azero = 0 'meter
lapserate = 0.0065 'K/m
Pzero = 101.3 'KPa
If MainETo.StnAlone = 1 Then
TotalStn = 1
MSFlexGrid1.Cols = 3
MSFlexGrid1.Rows = 1
MSFlexGrid1.AllowUserResizing = flexResizeColumns
MSFlexGrid1.ColWidth(1) = 2700
MSFlexGrid1.ColWidth(2) = 1100
s$ = "<Months
|>T.Max(o C)|>T.Min(o C)|>AverageT(o C)|>Mean
RH(%)|>Min.RH(%)|>Wind (km/d)|>SunShine(h)|>DayNight(%)|>ETo (mm/d)"
MSFlexGrid1.FormatString = s$
End If
If MainETo.StnAlone = 0 Then
MSFlexGrid1.Cols = 3
MSFlexGrid1.Rows = 1
MSFlexGrid1.AllowUserResizing = flexResizeColumns
MSFlexGrid1.ColWidth(1) = 2700
MSFlexGrid1.ColWidth(2) = 1100
s$ = "<Station Name
|>April
|>May
|>June
|>Latitude |>Longitude |>January |>February |>March
|>July
|>August
|>December "
MSFlexGrid1.FormatString = s$
End If
Open "c:\Table-W.dat" For Input As #4
For j = 0 To 4
For i = 1 To 20
Input #4, fW(i, j)
Next i
Next j
Close (4)
AvgT(0) = (Tmx(12) + Tmn(12)) / 2
|>September |>October |>November
For j = 1 To TotalStn
If MainETo.StnAlone <> 1 Then
radiant = LatiR(j) * pi / 180
Else
radiant = Lati * pi / 180
End If
If MainETo.StnAlone <> 1 Then
For i = 1 To 12
Tmx(i) = TmxR(j, i)
Tmn(i) = TmnR(j, i)
RHm(i) = RHmR(j, i)
Wnd(i) = WndR(j, i)
SS(i) = SSR(j, i)
SR(i) = SRR(j, i)
RF(i) = RFR(j, i)
PE(i) = PER(j, i)
Next i
Lati = LatiR(j)
Longi = LongiR(j)
Elev = ElevR(j)
End If
For i = 1 To 12
AvgT(i) = (Tmx(i) + Tmn(i)) / 2
Wind(i) = Wnd(i) / 86.4
EaTn(i) = 0.61078 * Exp(17.27 * Tmn(i) / (Tmn(i) + 237.3))
EaTx(i) = 0.61078 * Exp(17.27 * Tmx(i) / (Tmx(i) + 237.3))
ea(i) = (EaTx(i) + EaTn(i)) / 2
EaTxTn(i) = (EaTx(i) + EaTn(i)) / 2
Edew(i) = RHm(i) / (50 / EaTx(i) + 50 / EaTn(i))
Ed(i) = Edew(i)
'RHmax
RHmax(i) = Edew(i) / EaTn(i) * 100
RHmean(i) = Edew(i) / EaTx(i) * 100
RHdel(i) = Edew(i) / EaTx(i) / 2 + Edew(i) / EaTn(i) / 2
ETxTn(i) = 2049 * EaTx(i) / (Tmx(i) + 237.3) ^ 2 + 2049 * EaTn(i) / (Tmn(i) + 237.3) ^
2
Patm(i) = 101.3 * ((293 - 0.0065 * Elev) / 293) ^ 5.253
'Lambda(i) = 2.501 - (0.002361 * AvgT(i))
Gamma(i) = 0.006595 * Patm(i)
'Gamma(i) = 0.0016286 * Patm(i) / Lambda(i)
rc(i) = 70 'For Grass, 86 for Alfalfa (rc-> Canopy resistance
Ra(i) = AerDynResist / Wind(i)
GammaP(i) = Gamma(i) * (1 + rc(i) / Ra(i))
DlGm(i) = ETxTn(i) / (ETxTn(i) + GammaP(i))
GmDgm(i) = Gamma(i) / (ETxTn(i) + GammaP(i))
Aeroterm(i) = GmDgm(i) * Wind(i) * AeroTCoeff * (EaTxTn(i) - Edew(i)) / (AvgT(i) +
273)
Dayno(i) = (30.5 * i - 14.6)
Soldeclin(i) = Sin(((2 * pi * Dayno(i) / 365) - 1.39)) * 0.409
xx(i) = Sin(Soldeclin(i)) * Sin(radiant)
yy(i) = Cos(Soldeclin(i)) * Cos(radiant)
temp1 = -Tan(Soldeclin(i) * Tan(radiant))
Omega(i) = Atn(-temp1 / Sqr(-temp1 * temp1 + 1)) + 2 * Atn(1) 'ArcCos function
define
Dr(i) = (1 + 0.033 * Cos((2 * pi / 365) * Dayno(i)))
RAa(i) = 37.586 * Dr(i) * (Omega(i) * xx(i) + Sin(Omega(i)) * yy(i))
N1(i) = 24 / pi * Omega(i)
NbyN(i) = SS(i) / N1(i)
Rnl(i) = albedo * (Tk ^ 4) * (7.723 - (10 * Edew(i)) ^ 0.5) * (0.1 + 0.9 * NbyN(i))
Rns(i) = (1 - Alpha) * RAa(i) * (SWa + SWb * NbyN(i)) / 41.855
Altitude = Int(Elev / 500) * 500
TempC = Int(AvgT(i) / 2#) * 2
FW1 = fW(TempC / 2, Altitude / 500)
Rn(i) = Rns(i) - Rnl(i)
LatHVap = 595 - 0.51 * AvgT(i)
Pressure = 1013 - 0.1055 * Elev
Delta = 2 * (0.00738 * AvgT(i) + 0.8072) ^ 7 - 0.00116
Gama = 0.386 * Pressure / LatHVap
DoDGamma = Delta / (Delta + Gama)
GoDGamma = Gama / (Delta + Gama)
SoilFden = 0.38 * (AvgT(i) - AvgT(i - 1))
ETos(i) = DoDGamma * Rn(i) + GoDGamma * 15.36 * FW1 * (ea(i) - Ed(i))
EToSA(j, i) = ETos(i)
Next i
Next j
Subroutine Hargreaves
For j = 1 To TotalStn
If MainETo.StnAlone <> 1 Then
radiant = LatiR(j) * pi / 180
Else
radiant = Lati * pi / 180
End If
If MainETo.StnAlone <> 1 Then
For i = 1 To 12
Tmx(i) = TmxR(j, i)
Tmn(i) = TmnR(j, i)
SR(i) = SRR(j, i)
Next i
Lati = LatiR(j)
Longi = LongiR(j)
Elev = ElevR(j)
End If
For i = 1 To 12
AvgT(i) = (Tmx(i) + Tmn(i)) / 2
ETos(i) = 0.0135 * (AvgT(i) + 17.78) * SR(i)
EToSA(j, i) = ETos(i)
Next i
Next j
Subroutine JENSEN
CropHeight = 12 'Crop Height
TempHumid = 190 'Height temperature and humidity measurements
CropHgtWnd = 200 'Wind speed measured at Crop Height
AerDynResist = Log((CropHgtWnd - 0.667 * CropHeight) / (0.123 * CropHeight)) *
Log((TempHumid - 0.667 * CropHeight) / (0.0123 * CropHeight)) / (0.41) ^ 2
AeroTCoeff = 0.622 * 3.486 * 86400 / (AerDynResist * 1.01)
pi = 3.141592654
SWa = 0.25
'Short Wave Radiations
SWb = 0.5
'Short Wave Radiations
Alpha = 0.23
'Albedo
LWa = 0.9
'LongWave Radiations
LWb = 0.1
'LongWave Radiations
LWal = 0.34
'LongWave Radiations Albedo
LWbl = -0.139 'LongWave Radiations Albedo
'Label1.Caption = "Radiant = " + Format(radiant, "####.####")
'Label2.Caption = "AeroTCoeff = " + Format(AeroTCoeff, "####.##")
If MainETo.StnAlone = 1 Then
TotalStn = 1
MSFlexGrid1.Cols = 3
MSFlexGrid1.Rows = 1
MSFlexGrid1.AllowUserResizing = flexResizeColumns
MSFlexGrid1.ColWidth(1) = 2700
MSFlexGrid1.ColWidth(2) = 1100
s$ = "<Months
|>T.Max(o C)|>T.Min(o C)|>AverageT(o C)|>ETo (mm/d)"
MSFlexGrid1.FormatString = s$
End If
If MainETo.StnAlone = 0 Then
MSFlexGrid1.Cols = 3
MSFlexGrid1.Rows = 1
MSFlexGrid1.AllowUserResizing = flexResizeColumns
MSFlexGrid1.ColWidth(1) = 2700
MSFlexGrid1.ColWidth(2) = 1100
s$ = "<Station Name
|>April
|>May
|>June
|>Latitude |>Longitude |>January |>February |>March
|>July
|>August
|>December "
MSFlexGrid1.FormatString = s$
End If
For j = 1 To TotalStn
If MainETo.StnAlone <> 1 Then
radiant = LatiR(j) * pi / 180
Else
radiant = Lati * pi / 180
End If
If MainETo.StnAlone <> 1 Then
For i = 1 To 12
Tmx(i) = TmxR(j, i)
Tmn(i) = TmnR(j, i)
RHm(i) = RHmR(j, i)
Wnd(i) = WndR(j, i)
SS(i) = SSR(j, i)
SR(i) = SRR(j, i)
RF(i) = RFR(j, i)
PE(i) = PER(j, i)
Next i
Lati = LatiR(j)
Longi = LongiR(j)
Elev = ElevR(j)
End If
'-------------------------------------------------------iMaxT = Tmx(1)
iMinT = Tmn(1)
For i = 2 To 12
If Tmx(i) > iMaxT Then
|>September |>October |>November
iMaxT = Tmx(i)
iMinT = Tmn(i)
iMax = i
End If
Next i
SE1 = 7.608353659 - 0.0144517725 * iMaxT + 0.04105626543 * iMaxT ^ 2
SE2 = 7.608353659 - 0.0144517725 * iMinT + 0.04105626543 * iMinT ^ 2
'SE1 = 0.61078 * Exp(17.27 * iMaxT / (iMaxT + 237.3))
'SE2 = 0.61078 * Exp(17.27 * iMinT / (iMinT + 237.3))
Cl = 38# - 2 * Elev / 305#
'Cl = 68# - (3.6 * Elev / 1000)
Ch = 50# / (SE1 - SE2)
'Ct = 1 / (Cl + 7.3 * Ch)
Ct = (Cl + (13# * Ch)) ^ -1
Tx = -2.5 - 0.14 * (SE1 - SE2) - Elev / 550
'Tx = 27.5 - 0.25 * (SE2 - SE1) - Elev / 1000
For i = 1 To 12
AvgT(i) = (Tmx(i) + Tmn(i)) / 2
Wind(i) = Wnd(i) / 86.4
EaTn(i) = 0.61078 * Exp(17.27 * Tmn(i) / (Tmn(i) + 237.3))
EaTx(i) = 0.61078 * Exp(17.27 * Tmx(i) / (Tmx(i) + 237.3))
ea(i) = (EaTx(i) + EaTn(i)) / 2
EaTxTn(i) = (EaTx(i) + EaTn(i)) / 2
Edew(i) = RHm(i) / (50 / EaTx(i) + 50 / EaTn(i))
Ed(i) = Edew(i)
'RHmax
RHmax(i) = Edew(i) / EaTn(i) * 100
RHmean(i) = Edew(i) / EaTx(i) * 100
RHdel(i) = Edew(i) / EaTx(i) / 2 + Edew(i) / EaTn(i) / 2
ETxTn(i) = 2049 * EaTx(i) / (Tmx(i) + 237.3) ^ 2 + 2049 * EaTn(i) / (Tmn(i) + 237.3) ^
2
Patm(i) = 101.3 * ((293 - 0.0065 * Elev) / 293) ^ 5.253
'Lambda(i) = 2.501 - (0.002361 * AvgT(i))
Gamma(i) = 0.006595 * Patm(i)
'Gamma(i) = 0.0016286 * Patm(i) / Lambda(i)
rc(i) = 70 'For Grass, 86 for Alfalfa (rc-> Canopy resistance
Ra(i) = AerDynResist / Wind(i)
GammaP(i) = Gamma(i) * (1 + rc(i) / Ra(i))
DlGm(i) = ETxTn(i) / (ETxTn(i) + GammaP(i))
GmDgm(i) = Gamma(i) / (ETxTn(i) + GammaP(i))
Aeroterm(i) = GmDgm(i) * Wind(i) * AeroTCoeff * (EaTxTn(i) - Edew(i)) / (AvgT(i) +
273)
Dayno(i) = (30.5 * i - 14.6)
Soldeclin(i) = Sin(((2 * pi * Dayno(i) / 365) - 1.39)) * 0.4093
xx(i) = Sin(Soldeclin(i)) * Sin(radiant)
yy(i) = Cos(Soldeclin(i)) * Cos(radiant)
temp1 = -Tan(Soldeclin(i) * Tan(radiant))
Omega(i) = Atn(-temp1 / Sqr(-temp1 * temp1 + 1)) + 2 * Atn(1) 'ArcCos function
define
Dr(i) = (1 + 0.033 * Cos((2 * pi / 365) * Dayno(i)))
RAa(i) = 37.586 * Dr(i) * (Omega(i) * xx(i) + Sin(Omega(i)) * yy(i))
'Uday
N1(i) = 24 / pi * Omega(i)
'UDay/UNight ratio
NbyN(i) = SS(i) / N1(i)
'Rns(i) = (1 - albedo) * SR(i) / 2.45
Rnl(i) = albedo * (Tk ^ 4) * (7.723 - (10 * Edew(i)) ^ 0.5) * (0.1 + 0.9 * NbyN(i))
'RS
Rns(i) = (1 - Alpha) * RAa(i) * (SWa + SWb * NbyN(i))
Altitude = Int(Elev / 500) * 500
TempC = Int(AvgT(i) / 2#) * 2
'************************************
FWnd = 0.27 * (1 + Wnd(i) / 100)
'************************************
Rn(i) = Rns(i) - Rnl(i)
'ETos(i) = ((0.0239001 * SR(i)) + 50) * (AvgT(i) / (AvgT(i) + 15#) * 0.4 / 30)
ETos(i) = Ct * (AvgT(i) - Tx) * Rn(i)
'ETos(i) = ((68# - (36 * Elev / 1000)) + (13# * (50 / (SE1 - SE2)))) * (AvgT(i) - (27.5 0.25 * (SE1 - SE2) - Elev / 1000)) * Rn(i)
EToSA(j, i) = ETos(i)
Next i
Next j
Subroutine PEVAPO
For j = 1 To TotalStn
If EVAPMain.StnAlone = False Then
radiant = LatiR(j) * pi / 180
Else
radiant = Lati * pi / 180
End If
If EVAPMain.StnAlone = False Then
For i = 1 To 12
Tmx(i) = TmxR(j, i)
Tmn(i) = TmnR(j, i)
RHm(i) = RHmR(j, i)
Wnd(i) = WndR(j, i)
SS(i) = SSR(j, i)
SR(i) = SRR(j, i)
RF(i) = RFR(j, i)
PE(i) = PER(j, i)
Next i
Lati = LatiR(j)
Longi = LongiR(j)
Elev = ElevR(j)
End If
KPan = 0.75
For i = 1 To 12
ETos(i) = PE(i) * KPan
EToSA(j, i) = ETos(i)
Next i
Next j
Subroutine RADIATION
CropHeight = 12 'Crop Height
TempHumid = 190 'Height temperature and humidity measurements
CropHgtWnd = 200 'Wind speed measured at Crop Height
AerDynResist = Log((CropHgtWnd - 0.667 * CropHeight) / (0.123 * CropHeight)) *
Log((TempHumid - 0.667 * CropHeight) / (0.0123 * CropHeight)) / (0.41) ^ 2
AeroTCoeff = 0.622 * 3.486 * 86400 / (AerDynResist * 1.01)
pi = 3.141592654
SWa = 0.25
'Short Wave Radiations
SWb = 0.5
'Short Wave Radiations
Alpha = 0.23
'Albedo
LWa = 0.9
'LongWave Radiations
LWb = 0.1
'LongWave Radiations
LWal = 0.34
'LongWave Radiations Albedo
LWbl = -0.139 'LongWave Radiations Albedo
'Label1.Caption = "Radiant = " + Format(radiant, "####.####")
'Label2.Caption = "AeroTCoeff = " + Format(AeroTCoeff, "####.##")
radiant = Lati * pi / 180
albedo = 0.25 ' for grass
a0 = 0.6817
A1 = 0.0027864
A2 = 0.0181768
a3 = -0.0682501
a4 = 0.0126514
a5 = 0.0097297
a6 = 0.000043025
a7 = -0.000000092118
k = 0.41
R = 287 'J/kg/K
Gravity = 9.81 ' m/s2
TK0 = 293.16 'K
Azero = 0 'meter
lapserate = 0.0065 'K/m
Pzero = 101.3 'KPa
If EVAPMain.StnAlone = True Then
TotalStn = 1
MSFlexGrid1.Cols = 3
MSFlexGrid1.Rows = 1
MSFlexGrid1.AllowUserResizing = flexResizeColumns
MSFlexGrid1.ColWidth(1) = 2700
MSFlexGrid1.ColWidth(2) = 1100
s$ = "<Months
|>T.Max(o C)|>T.Min(o C)|>AverageT(o C)|>Mean
RH(%)|>Min.RH(%)|>Wind (km/d)|>SunShine(h)|>DayNight(%)|>ETo (mm/d)"
MSFlexGrid1.FormatString = s$
Else
MSFlexGrid1.Cols = 3
MSFlexGrid1.Rows = 1
MSFlexGrid1.AllowUserResizing = flexResizeColumns
MSFlexGrid1.ColWidth(1) = 2700
MSFlexGrid1.ColWidth(2) = 1100
s$ = "<Station Name
|>April
|>May
|>June
|>Latitude
|>July
|>August
|>December "
MSFlexGrid1.FormatString = s$
End If
Open "c:\Table-W.dat" For Input As #4
For j = 0 To 4
For i = 1 To 20
Input #4, fW (i, j)
Next i
Next j
|>Longitude
|>January |>February |>March
|>September |>October |>November
Close (4)
Open "c:\table-c.dat" For Input As #5
For j = 1 To 16
For i = 1 To 12
Input #5, c (i, j)
Next i
Next j
Close (5)
' Open "c:\Test.txt" For Output As #6
'
'
'
For j = 1 To TotalStn
If EVAPMain.StnAlone = False Then
Radiant = LatiR (j) * pi / 180
Else
Radiant = Lati * pi / 180
End If
If EVAPMain.StnAlone = False Then
For i = 1 To 12
Tmx (i) = TmxR(j, i)
Tmn (i) = TmnR (j, i)
RHm (i) = RHmR (j, i)
Wnd (i) = WndR (j, i)
SS (i) = SSR (j, i)
SR (i) = SRR (j, i)
RF (i) = RFR (j, i)
PE (i) = PER(j, i)
Next i
Lati = LatiR (j)
Longi = LongiR (j)
Elev = ElevR (j)
End If
For i = 1 To 12
AvgT (i) = (Tmx(i) + Tmn(i)) / 2
Wind (i) = Wnd(i) / 86.4
EaTn (i) = 0.61078 * Exp(17.27 * Tmn(i) / (Tmn(i) + 237.3))
EaTx (i) = 0.61078 * Exp(17.27 * Tmx(i) / (Tmx(i) + 237.3))
ea (i) = (EaTx(i) + EaTn(i)) / 2
EaTxTn (i) = (EaTx(i) + EaTn(i)) / 2
Edew (i) = RHm(i) / (50 / EaTx(i) + 50 / EaTn(i))
Ed(i) = Edew(i)
'RHmax
RHmax(i) = Edew(i) / EaTn(i) * 100
RHmean(i) = Edew(i) / EaTx(i) * 100
RHdel(i) = Edew(i) / EaTx(i) / 2 + Edew(i) / EaTn(i) / 2
ETxTn(i) = 2049 * EaTx(i) / (Tmx(i) + 237.3) ^ 2 + 2049 * EaTn(i) / (Tmn(i) + 237.3) ^
2
Patm(i) = 101.3 * ((293 - 0.0065 * Elev) / 293) ^ 5.253
'Lambda(i) = 2.501 - (0.002361 * AvgT(i))
Gamma(i) = 0.006595 * Patm(i)
'Gamma(i) = 0.0016286 * Patm(i) / Lambda(i)
rc(i) = 70 'For Grass, 86 for Alfalfa (rc-> Canopy resistance
Ra(i) = AerDynResist / Wind(i)
GammaP(i) = Gamma(i) * (1 + rc(i) / Ra(i))
DlGm(i) = ETxTn(i) / (ETxTn(i) + GammaP(i))
GmDgm(i) = Gamma(i) / (ETxTn(i) + GammaP(i))
Aeroterm(i) = GmDgm(i) * Wind(i) * AeroTCoeff * (EaTxTn(i) - Edew(i)) / (AvgT(i) +
273)
Dayno(i) = (30.5 * i - 14.6)
Soldeclin(i) = Sin(((2 * pi * Dayno(i) / 365) - 1.39)) * 0.4093
xx(i) = Sin(Soldeclin(i)) * Sin(radiant)
yy(i) = Cos(Soldeclin(i)) * Cos(radiant)
temp1 = -Tan(Soldeclin(i) * Tan(radiant))
Omega(i) = Atn(-temp1 / Sqr(-temp1 * temp1 + 1)) + 2 * Atn(1) 'ArcCos function
define
Dr(i) = (1 + 0.033 * Cos((2 * pi / 365) * Dayno(i)))
RAa(i) = 37.586 * Dr(i) * (Omega(i) * xx(i) + Sin(Omega(i)) * yy(i))
'Uday
N1(i) = 24 / pi * Omega(i)
'UDay/UNight ratio
NbyN(i) = SS(i) / N1(i)
'Rns(i) = (1 - albedo) * SR(i) / 2.45
Rnl(i) = albedo * (Tk ^ 4) * (7.723 - (10 * Edew(i)) ^ 0.5) * (0.1 + 0.9 * NbyN(i))
'RS
Rns(i) = (1 - Alpha) * RAa(i) * (SWa + SWb * NbyN(i))
FNbyN(i) = (LWb + LWa * NbyN(i))
If RHmax(i) > 0 And RHmax(i) < 45 Then RH = 45
If RHmax(i) >= 45.01 And RHmax(i) < 75 Then RH = 60
If RHmax(i) >= 75.01 Then RH = 90
If FNbyN(i) < 1.5 Then Unight = 1
If FNbyN(i) >= 1.5 And FNbyN(i) < 2.5 Then Unight = 2
If FNbyN(i) >= 2.5 And FNbyN(i) < 3.5 Then Unight = 3
If FNbyN(i) >= 3.5 Then Unight = 4
If SR(i) > 0 And SR(i) < 4.5 Then SolR = 3
If SR(i) >= 4.5 And SR(i) < 7.5 Then SolR = 6
If SR(i) >= 7.5 And SR(i) < 10.5 Then SolR = 9
If SR(i) >= 10.5 Then SolR = 12
If N1(i) >= 0 And N1(i) < 1.5 Then Uday = 0
If N1(i) >= 1.5 And N1(i) < 4.5 Then Uday = 3
If N1(i) >= 4.5 And N1(i) < 7.5 Then Uday = 6
If N1(i) >= 7.5 Then Uday = 9
xin = (RH / 30 - 1) * 4 + SolR / 3
yin = (4 - Unight) * 4 + (Uday / 3 + 1)
'************************************
Altitude = Int(Elev / 500) * 500
TempC = Int(AvgT(i) / 2#) * 2
'************************************
FWnd = 0.27 * (1 + Wnd(i) / 100)
'************************************
Rn(i) = Rns(i) - Rnl(i)
'************************************
ETos(i) = c(xin, yin) * (fW(TempC / 2, Altitude / 500) * Rn(i))
'************************************
EToSA(j, i) = ETos(i)
Subroutine BLANCRID
Open "c:\Table-P.dat" For Input As #1
For i = 1 To 12
For j = 0 To 10
Input #1, P(i, j)
Next j
Next i
Close (1)
For j = 1 To TotalStn
If EVAPMain.StnAlone = False Then
radiant = LatiR(j) * pi / 180
Else
radiant = Lati * pi / 180
End If
'--------------------------------------------------------
For i = 1 To 12
AvgT(i) = (Tmx(i) + Tmn(i)) / 2
ETos(i) = P(i, Int(Lati / 5)) * (0.46 * AvgT(i) + 8.13)
EToSA(j, i) = ETos(i)
Next i
Next j
Subroutine BLANCRID
Open "c:\Table-P.dat" For Input As #1
For i = 1 To 12
For j = 0 To 10
Input #1, P(i, j)
Next j
Next i
Close (1)
Open "c:\Table-B.dat" For Input As #2
For i = 1 To 36
For j = 0 To 5
'Solar Radiations * Wind at 2 m
'Relative Humidity
Input #2, B(i, j)
Next j
Next i
Close (2)
Open "C:\Test.txt" For Output As #3
For j = 1 To TotalStn
If EVAPMain.StnAlone = False Then
radiant = LatiR(j) * pi / 180
Else
radiant = Lati * pi / 180
End If
MaxDayHr = 1
For i = 1 To 12
If SS(i) > MaxDayHr Then MaxDayHr = SS(i)
Next i
For i = 1 To 12
AvgT(i) = (Tmx(i) + Tmn(i)) / 2
Wind(i) = Wnd(i) / 86.4
Dh1 = (Int((SS(i) / MaxDayHr) * 10 / 2) * 2 / 10) / 0.2
Dh2 = (Int((Wind(i) + 0.5) / 2) * 2) / 2
Dh3 = (Int((RHm(i) + 5) / 20) * 20) / 20
xin = Dh1 * 6 + Dh2
yin = Dh3
a = 0.0043 * RHm(i) - SS(i) - 1.41
ETos(i) = a + B(xin, yin) * (P(i, Int(Lati / 5)) * (0.46 * AvgT(i) + 8.13))
EToSA(j, i) = ETos(i)
Next i
Next j
Subroutine PRIESTLY
CropHeight = 12 'Crop Height
TempHumid = 190 'Height temperature and humidity measurements
CropHgtWnd = 200 'Wind speed measured at Crop Height
AerDynResist = Log((CropHgtWnd - 0.667 * CropHeight) / (0.123 * CropHeight)) *
Log((TempHumid - 0.667 * CropHeight) / (0.0123 * CropHeight)) / (0.41) ^ 2
AeroTCoeff = 0.622 * 3.486 * 86400 / (AerDynResist * 1.01)
pi = 3.141592654
SWa = 0.25
'Short Wave Radiations
SWb = 0.5
'Short Wave Radiations
Alpha = 0.23
'Albedo
LWa = 0.9
'LongWave Radiations
LWb = 0.1
'LongWave Radiations
LWal = 0.34
'LongWave Radiations Albedo
LWbl = -0.139 'LongWave Radiations Albedo
For j = 1 To TotalStn
If EVAPMain.StnAlone = False Then
radiant = LatiR(j) * pi / 180
Else
radiant = Lati * pi / 180
End If
For i = 1 To 12
AvgT(i) = (Tmx(i) + Tmn(i)) / 2
Wind(i) = Wnd(i) / 86.4
EaTn(i) = 0.61078 * Exp(17.27 * Tmn(i) / (Tmn(i) + 237.3))
EaTx(i) = 0.61078 * Exp(17.27 * Tmx(i) / (Tmx(i) + 237.3))
EaTxTn(i) = (EaTx(i) + EaTn(i)) / 2
Edew(i) = RHm(i) / (50 / EaTx(i) + 50 / EaTn(i))
RHmean(i) = Edew(i) / EaTx(i) * 100
RHdel(i) = Edew(i) / EaTx(i) / 2 + Edew(i) / EaTn(i) / 2
ETxTn(i) = 2049 * EaTx(i) / (Tmx(i) + 237.3) ^ 2 + 2049 * EaTn(i) / (Tmn(i) + 237.3) ^ 2
Patm(i) = 101.3 * ((293 - 0.0065 * Elev) / 293) ^ 5.253
Lambda(i) = 2.501 - (0.002361 * AvgT(i))
Gamma(i) = 0.0016286 * Patm(i) / Lambda(i)
rc(i) = 70 'For Grass, 86 for Alfalfa (rc-> Canopy resistance
Ra(i) = AerDynResist / Wind(i)
GammaP(i) = Gamma(i) * (1 + rc(i) / Ra(i))
DlGm(i) = ETxTn(i) / (ETxTn(i) + GammaP(i))
GmDgm(i) = Gamma(i) / (ETxTn(i) + GammaP(i))
Aeroterm(i) = GmDgm(i) * Wind(i) * AeroTCoeff * (EaTxTn(i) - Edew(i)) / (AvgT(i) +
273)
Dayno(i) = (30.5 * i - 14.6)
Soldeclin(i) = Sin(((2 * pi * Dayno(i) / 365) - 1.39)) * 0.4093
xx(i) = Sin(Soldeclin(i)) * Sin(radiant)
yy(i) = Cos(Soldeclin(i)) * Cos(radiant)
temp1 = -Tan(Soldeclin(i) * Tan(radiant))
Omega(i) = Atn(-temp1 / Sqr(-temp1 * temp1 + 1)) + 2 * Atn(1) 'ArcCos function define
Dr(i) = (1 + 0.033 * Cos((2 * pi / 365) * Dayno(i)))
RAa(i) = 37.586 * Dr(i) * (Omega(i) * xx(i) + Sin(Omega(i)) * yy(i))
N1(i) = 24 / pi * Omega(i)
NbyN(i) = SS(i) / N1(i)
Rns(i) = (1 - Alpha) * RAa(i) * (SWa + SWb * NbyN(i))
FNbyN(i) = (LWb + LWa * NbyN(i))
Sigma(i) = 0.00000000245 * ((Tmx(i) + 273) ^ 4 + (Tmn(i) + 273.16) ^ 4)
Emissivity(i) = LWal + LWbl * Sqr(Edew(i))
Rbo(i) = 0.00000000245 * (LWal + LWbl * Sqr(Edew(i))) * (((Tmx(i) + 273.16) ^ 4 +
(Tmn(i) + 273.16) ^ 4))
LWR(i) = Rbo(i) * (LWb + LWa * NbyN(i))
RnsRl(i) = Rns(i) - LWR(i)
Next i
AvgT(0) = AvgT(12)
For i = 1 To 12
G(i) = 0.14 * (AvgT(i) - AvgT(i - 1))
RnG(i) = RnsRl(i) - G(i)
ETos(i) = Alpha*ETxTn(i)*RnG(i)/((ETxTn(i)+Gamma)*Lambda)
EToSA(j, i) = ETG(i)
Next i
Next j
2.2 LIST OF THE EVAPORATION EQATION
Reference ET Methods Calculated by EVAPO SAUDIA Version 1.0
The EVAPO SAUDIA program offers the user ten alternative methods of
evapotranspiration calculation by combination equations from various sources.
The program provides calculations that are compatible with United Nations Food
and Agriculture Organization (FAO) Irrigation Paper N0. 24 & 56 and with
standardized forms of the ASCE Penman-Monteith equation.
a)
Corrected Penman FAO-24 (Doorenbos and Pruitt, 1975, 1977)
b)
Penman Modified (Penman 1948, 1963)
c)
Penman Monteith FAO-56 (Monteith, 1965 & 1981, Allen et al., 1989)
d)
Hargreaves Temperature Method (Hargreaves and Samani, 1985)
e)
Jensen-Haise Method (Jensen and Haise, 1963)
f)
Blaney-Criddle (Israelsen and Hansen, 1962)
g)
Blaney-Criddle Modified FAO-24 (Doorenbos and Pruitt, 1977)
h)
Priestley-Taylor (Radiation and Temperature Method, 1972)
i)
Pan Evaporation FAO-24 (Doorenbos and Pruitt, 1977)
j)
Radiation Method FAO-24 (Doorenbos and Pruitt, 1977)
2.3 Design of the equations