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JKAU: Met., Env. & Arid Land Agric. Sci., Vol. 22, No. 2, pp: 59-78 (2011 A.D./1432 A.H.)
DOI: 10.4197/Met. 22-2.4
59
Analysis of Rainfall over Saudi Arabia
A. Mashat and H. Abdel Basset
Department of Meteorology, Faculty of Meteorology, Environment,
and Arid Land Agriculture, King Abdulaziz University,
Jeddah, Saudi Arabia
Abstract..In this study, rainfall over the Kingdom of Saudi Arabia
(KSA) is analyzed using data from available meteorological stations.
The analysis of these data shows that the highest amount of rainfall
occurs during the spring over the southwest, middle and east of KSA.
The second highest amount of rainfall occurs during winter over the
east and northeast of KSA. The season of the lowest amount of
rainfall over KSA is summer, when, except in the mountainous area in
the southwest region, the amount of rainfall is very small. While the
horizontal distribution pattern of rainfall during autumn is somewhat
similar to that during spring, the amount of rainfall in autumn is
smaller than that in spring. The most significant synoptic feature
appears in spring when the cold air associated with secondary
Mediterranean depressions meets the moist hot southerly air
associated with Red Sea trough over KSA.
1. Introduction
The amount of rainfall that falls over an area is an important factor in
assessing the amount of water available to meet the various demands of
agriculture, industry, and other human activities. Study of the distribution
of rainfall over time and space is therefore very important for the welfare
of a national economy. Many applications of rainfall data are enhanced
by knowledge of the actual distribution of rainfall over a specified area
rather than relying on simple summary statistics. In recent years, several
studies have been devoted to the interannual and decadal variability of
precipitation on regional, national and international scales. Different
methodological approaches have been used, such as temporal analysis of
60 A. Mashat and H. Abdel Basset
rainfall (Serrano, et al., 1999; De Luís, et al., 2000; Estrela, et al., 2000;
Agnese, et al., 2002; Turkes, et al., 1996), analysis of extreme events in
regional daily precipitation series (Brunetti, et al., 2002 and 2004), and
use of the standardized precipitation index (Delitala, et al., 2000; Lana, et
al., 2001; Bordi, et al., 2001; and Lloyd-Hughes and Saunders, 2002).
Several researchers have analyzed hydro-meteorological time series in
West Africa from Niger to Senegal (Carbonnel and Hubert, 1985 and
1994; Snijders, 1986; Hubert and Carbonnel, 1987; and Paturel, et al.,
1997). They pointed out the non stationarity of the series and suggested a
climatic change between 1965 and 1972, with the majority of the shifts
appearing between 1969 and 1970. Precipitation in the Great Plains of
the United States also changed significantly with an increase since the
late 1960s and the last two decades of the twentieth century being the
wettest of that century (Garbrecht and Rossel, 2000). A report from the
Office of Technology Assessment (1993) pointed out that the anticipated
intensification of the hydrological cycle would increase global rainfall by
7 to 15 % and evapotranspiration between 5 and 10%. An increase in
extreme events that will be disruptive to natural and human systems is
likely to occur (IPCC, 1995). However, whereas in certain areas an
increase of rainfall is expected, other areas will suffer from decreased
rainfall.
The aim of this study is to analyze the climatology of monthly and annual rainfall over the Kingdom of Saudi Arabia (KSA). The remainder of this paper is organized as follows: In Section 2, data from meteorological stations in KSA and the homogeneity of these data are described. Section 3 presents the results of an analysis of monthly, annual and horizontal distributions of rainfall over KSA. Finally, conclusions are offered in Section 4.
2. Data from KSA Meteorological Stations
Because of its low annual precipitation, KSA is commonly
regarded as a dry country. This is a climatic simplification; however,
because precipitation varies over space and time and of the amounts of
precipitation over particular regions of KSA are diverse. Besides spatial
differences, interannual variations of precipitation also occur. The
complexity of the rates of precipitation over KSA derives from the vast
area of the country (about 2,250,000 km2), its wide latitudinal expanse
(15.5°N - 32.5°N) and its pronounced topographical relief. Monthly
Analysis of Rainfall over Saudi Arabia 61
precipitation records are compiled for 28 stations managed by the KSA
Meteorological Organization. The stations are distributed across KSA,
although their spatial density is low and uneven in some parts of the
country. Table 1 gives the name, position, elevation and the available
period of data from each KSA meteorological station.
Studies on data homogeneity are essential to climatology. Homogeneity is manifested differently depending on the climatic element. The values of climatic measures of these climatic elements could be used in estimating daily and monthly averages. Artificial lakes and reservoirs and other man-made changes to the local environment produce sources of inhomogeneity in historical records of climatic data. Homogeneity in rainfall over cities in KSA has been examined by means of the Bartlet test.
Table 1. The name, position, elevation and the available data period for each KSA
meteorological station.
No Name Lat Long Elevation Available Data Years
1 Turaif 31.68 38.73 852.44 1978 --- 2003 26
2 Gurait 31.40 37.28 503.90 1985 --- 2003 19
3 Arar 30.90 41.14 548.88 1979 --- 2003 25
4 Aljouf 29.78 40.98 668.74 1978 --- 2003 26
5 Tabouk 28.37 36.60 444.10 1978 --- 2003 26
6 Hail 27.43 41.69 768.11 1970 --- 2003 34
7 Wejh 26.20 38.47 357.60 1978 --- 2003 26
8 Rafha 29.62 43.49 413.00 1978 --- 2003 26
9 Alqusoma 28.31 46.13 1001.52 1978 --- 2003 26
10 Hafrbaten 27.90 45.53 646.71 1985 --- 2003 19
11 Dhahran 26.25 50.16 16.77 1970 --- 2003 34
12 Ahsa 25.29 49.48 23.73 1985 --- 2003 19
13 Gassim 26.30 43.76 178.17 1978 --- 2003 26
14 New Riyadh 24.92 46.72 613.55 1985 --- 2003 19
15 Old Riyadh 24.71 46.73 619.63 1970 --- 2003 34
16 Wadi Aldwaser 20.50 45.25 635.60 1978 --- 2003 26
17 Madina 24.54 39.69 3.58 1970 --- 2003 34
18 Yenbo 24.14 38.06 1452.75 1978 --- 2003 26
19 Jeddah 21.71 39.18 240.35 1970 --- 2003 34
20 Makkah 21.43 39.79 701.02 1985 --- 2003 19
21 Taif 21.48 40.55 614.39 1970 --- 2003 34
22 Baha 20.29 41.64 1651.88 1985 --- 2003 19
23 Bisha 19.99 42.61 1161.97 1970 --- 2003 34
24 Abha 18.23 42.66 2055.93 1978 --- 2003 26
25 Khamis Mush 18.29 42.80 2093.35 1970 --- 2003 34
26 Najran 17.61 44.41 1212.33 1978 --- 2003 26
27 Sharura 17.46 47.10 724.65 1985 --- 2003 19
28 Gizan 16.90 42.58 7.24 1970 --- 2003 34
62 A. Mashat and H. Abdel Basset
Table 2 presents Bartlet test (short-cut) results for mean annual rainfall at each station. The mean annual rainfall seems to be homogeneous except at the Tabouk and Sharorah stations when
( 2 2
max min/S S ) is used with 95% significance as discussed by Mitchell et al.
(1966). The mean annual rainfall amounts at the Aljouf and Abha stations indicate some inhomogeneities.
Table 2. Bartlet test (short- cut) result for the KSA stations (n is the number of terms in
each subperiod k, and k is the number of the subperiod).
Station N k 95%
Significant point Homogeneity
Turaif 13 2 3.28 1.56
Guriat 9 2 4.43 2.17
Arar 13 2 3.28 3.25
Aljouf 13 2 3.28 3.36
Rafha 13 2 3.28 1.48
Tabouk 13 2 3.28 6.23
Alqaisoma 13 2 3.28 1.55
Hail 11 3 4.85 1.68
Qassim 17 2 2.76 2.69
Dhahran 15 2 3.16 2.33
Alwajh 13 2 3.28 3.17
Alahsa 9 2 4.43 3.25
New Riyadh 9 2 4.43 3.52
Old Riyadh 17 2 2.76 1.32
Madinah 17 2 2.76 1.59
Yanbo 13 2 3.28 2.59
Jeddah 17 2 2.76 1.73
Taif 17 2 2.76 2.77
Makkah 9 2 4.43 3.96
Albaha 9 2 4.43 1.85
Bisha 11 3 4.85 1.92
Khamis Moshet 11 3 4.85 3.62
Abha 13 2 3.28 3.31
Najran 8 3 6.94 1.15
Sharorah 9 2 4.43 6.32
Gizan 11 3 4.85 1.57
3. Results and Discussion
3.1 Monthly Average Rainfall
Figure 1(a) shows the average monthly amounts of rainfall for each
month of the year at the Arar, Turaif, Guriat, Aljouf, Tabouk and Hail
stations. The maximum amount of rainfall at these stations occurs in
January, and the average amounts of rainfall in January at all stations
Analysis of Rainfall over Saudi Arabia 63
exceeds 10 mm except for Tabouk. The second rainiest month at these
stations is December. Hail and Turaif receive the highest amount of
rainfall during the rainy months of the year. The months from June to
September are the dry months of the year, while the winter and spring
months are the wet months at these stations.
Figure 1(b) presents the average monthly amounts of rainfall for each month of the year at the Alwajh, Rafha, Alqaisoma, Hafr Albaten, Dharan and Alahsa stations. The maximum amount of rainfall at these stations occurs during the winter season excluding November, March and April. These stations do not receive any rainfall during the June to September period. The averages of the monthly rainfall at the Hafr Albaten and Dharan stations are more than 30 mm in January and March, respectively. The period from May to October is the dry period at these stations.
Figure 1(c) shows the average monthly rainfall amounts for each month of the year at the Qassim, New Riyadh, Old Riyadh, Wadi Aldwaser, Sulayel and Madinah stations. This figure indicates that the maximum amount of rainfall at the Qassim, New Riyadh, and Old Riyadh stations occurs in March and April. The maximum amounts of rainfall received at the Sulsyel station are at April. The Wadi Aldwaser and Madinah stations recived less than 10 mm of rain during the rainy months of the year. The period from June to October is the dry period at these stations.
Figure 1(d) presents the average monthly rainfall amounts for each month of the year at the Yanbo, Jeddah, Makkah, Taif, Abbaha and Bisha stations. It is clear that the mountain stations (Taif, Abbaha and Bisha) received the maximum amount of rainfall of this group of stations. The highest values of rainfall at these mountain stations occur during the spring especially in April. Considerable amounts of rainfall at the Makkah and Jeddah stations occur in November, December and January. The three mountain stations received rainfall throughout the year with lowest values in February.
Figure 1(e) shows the average monthly rainfall amounts for each month of the year at Abha, Khames Moshet, Najran, Sharorah and Gizan stations. It is clear that the maximum amount of rainfall at these stations occurs at the Abha and Khamis Moshet stations in March, April, May and August. The mountain station of Abha received the greatest amount of rainfall in KSA (more than 55 mm). The minimum amount of rainfall
64 A. Mashat and H. Abdel Basset
occurs during September, October, November and December at these stations.
Fig. 1(a). The average monthly rainfall amounts for each month of the year at the Arar,
Turaif, Guriat, Aljouf, Tabouk and Hail stations.
Fig. 1(b). The average monthly rainfall amounts for each month of the year at the Alwajh,
Rafha, Alqaisoma, Hafrelbaten, Dhahran and Alahsa stations.
0
5
10
15
20
25
30
35
jan feb mar apr may jun jul aug sep oct nov dec
pre
cip
ita
tio
n (
mm
)
Alwajh Rafha Alqaisoma Hafr Albaten Dhahran Alahsa
0
5
10
15
20
25
30
jan feb mar apr may jun jul aug sep oct nov dec
pre
cip
ita
tio
n (
mm
)
Arar Turaif Guriat Aljouf Tabouk Hail
Analysis of Rainfall over Saudi Arabia 65
Fig. 1(c). The average monthly rainfall amounts for each month of the year at the Qassim,
New Riyadh, Old Riyadh, Wadi Aldwaser, Sulayel, and Madinah stations.
Fig. 1(d). The average monthly rainfall amounts for each month of the year at the Yanbo,
Jeddah, Makkah, Taif, Albaha and Bisha stations.
0
5
10
15
20
25
30
35
40
jan feb mar apr may jun jul aug sep oct nov dec
pre
cip
itati
on
(m
m)
Qassim Riyadh new Riyadh Old Wadi Aldwaser Sulayel Madinah
0
5
10
15
20
25
30
35
40
jan feb mar apr may jun jul aug sep oct nov dec
pre
cip
ita
tio
n (
mm
)
Yanbo Jeddah Makkah Taif Albaha Bisha
66 A. Mashat and H. Abdel Basset
Fig. 1(e). The average monthly rainfall amounts for each month of the year at the Abha,
Khamis Moshet, Najran, Sharorah and Gizan stations.
The stations that lie north of 24.5oN do not receive a considerable
amount of rain during the summer months in additions to September. In the winter, the highest amounts of rainfall occur at the stations in the east of the middle of KSA (the Hail, Gassim, new Riyad, old Riyad, Hafr Elbaten and Qaisoma stations). In spring, the southwestern stations and stations to the east of the middle of KSA received higher amounts of rain with the maximum at Abha in March (60 mm). In the autumn, the seven stations of Hafr Elbaten, Qaisoma, Jeddah, Makkah, Taif, Hail and Gizan receive considerable amounts of rain (more than 20 mm). From the seasonal analysis of rainfall, the periods of rainfall over KSA can be divided into two main periods. The first period includes November, December, January, February, March, April and May. About 80% of the total rainfall over KSA occurs during these months. The second period includes the other five months (June through October).
3.2 Annual Rainfall
In this section, the annual amounts of rainfall at 29 meteorological
stations in KSA are discussed. The slopes of the time series trends at
each station were calculated by least squares linear fitting. Figure 2(a)
presents the annual rainfall amounts at the Turaif, Guriat, Arar, Aljouf,
Rafha, Tabouk, Alqaisoma and Hafr Albaten stations for the available
0
10
20
30
40
50
60
70
jan feb mar apr may jun jul aug sep oct nov dec
pre
cip
itati
on
(m
m)
Abha Khamis Moshet Najran Sharorah Gizan
Analysis of Rainfall over Saudi Arabia 67
periods. It is interesting to note that there are two peaks in the rainfall
time series for Turaif. The first one occurs during 1979 and the second
one occurs in 1982. The maximum of the annual mean values at Guriat
occurs in 1988 while the minimum values occur in 1993 and 2000. The
maximum annual rainfall received at Arar is in 1988 while the minimum
amount is in 1996. Negative trends can be observed for these three
stations. Although the annual amount of rainfall received at Aljouf is
small, there is a positive rainfall trend. The highest amount recorded at
Rafha is in 1974. Figure 2(a) also shows that the trend of the annual
rainfall amounts at Tabouk and Alqaisoma is negative and the amount of
rainfall received at Alqaisoma is greater than at Tabouk throughout the
period of this study.
Figure 2(b) shows the annual rainfall amounts at Hail, Qassim, Dhahran, Alwajh, Alahsa, New Riyadh, Old Riyadh and Madinah stations during the available period for each station. It is interesting to note that there are four peaks in the rainfall time series for Hail (greater than 20 mm). The first peak occurred in 1976; the second and third were in 1982 and 1984; while the last in 1993. Large variability in the time series at Hail can be observed with a positive trend. The maximum rainfall amount received at Qassim is in 1982 (40 mm), while the minimum values are recorded in 1990. Considerable variability in the time series for Dhahran can be observed with a positive trend. Three maximum values occurred (greater than 20 mm). The first one was in 1972, the second in 1976, while the last in 1982. Although the trend of the time series for Alwajh is positive, it receives small amounts of rain throughout the period. As at most stations, it is clear that a wave length 4 years is the dominant wave of the time series for the Old Riyadh station. Three peaks (greater than 20 mm) in the annual rainfall appeared for this station, one in 1972, the second in 1976 and the last in 1995. A considerable variability in the annual rainfall time series for Madinah is evident, although the amount of rainfall is small throughout the period for this station. The trend for the time series for Madinah is positive.
Figure 2(c) shows the annual rainfall amounts for the Yanbo, Jeddah, Taif, Makkah, Wadi Aldwaser, Albaha, Bisha and Khmis Moshet stations during the available period for each station. It indicates that higher annual rainfall amounts at Yanbo occur in 1992 and 1993, while a lower amount occurs in 1995. The annual amount of rainfall at Jeddah reached 24 mm in 1996, while this amount in other years does not exceeded 10 mm. The lowest value is recorded in 1982. The time series
68 A. Mashat and H. Abdel Basset
for Taif follows a wave pattern with 5-year wave length. The maximum values occured in 1992 and 1996. Like in Taif, the maximum annual values at Makkah occur in 1992 and 1996. The trend for these four stations is positive. The trends for the time series for Wadi Aldwaser, Albaha, Bisha and Khamis Moshet are negative. The average values of the annual time series for Nisha and Khamis Moshet are 8.5 and 17 mm, respectively. Figure 2(d) shows the annual rainfall amounts for the Abha, Najran, Sharorah and Gizan stations during the available period for each station. It indicates that time series for Abha is very similar to those for Bisha and Khamis Moshet due to the proximity of these stations. The trend of the last three stations that fall in the same area is positive. The mean annual rainfall for the most stations in KSA was highest in 1982. The trend analysis of the mean annual rainfall at KSA stations indicates a positive trend (wet) at 14 stations (Aljouf, Hafr Albaten, Rafha, Dahran, Alwajh, New Riadh, Madinah, Yanbo, Jeddah, Mekkah, Najran, Sharora, and Gizan). There is a negative trend (dry) at 15 stations (Turaif, Guriat, Rafha, Alqaisoma, Tabouk, Hail, Qassim, Albaha, Old Riyadh, Wadi Aldwaser, Albaha, Bisha, Kamis Moshet and Abha).
3.3 The Horizontal Distribution of Rainfall over KSA
Figure 3(a) gives the names and positions of the KSA
meterological stations, while Fig. 3(b) shows the average annual amounts
of rainfall at KSA meterological stations. It is clear that the maximum
annual rainfall occurs in two regions: The first is east of the middle
region (Hail, Gassim, Hafr Albaten, Qaisoma, Riyad and Dharan) and the
second is the southwest region (Taif, Baha, Khamis Meshet, Abha, and
Gizan). The lowest rainfall values occur in the north and northwest areas.
The southeast area does not house a meteorological station but it is
considered a dry area.
Figure 4(a) shows the average mean amounts of rainfall during the winter in KSA, while Fig. 4(b) shows the average mean amounts of rainfall during the spring in KSA. It is clear that the maximum rainfall during the winter occurs in the north and the middle of the eastern area and over the mountainous area in the southwest region. The highest rainfall amounts in KSA occur during the spring. Similar to the annual values (Fig. 3b), there are two regions with maximum rainfall, the first in the northeast and the second is in southwest of KSA. The maximum amount (21.9 mm) occured at Hafr Elbaten, while the maximum amounts during the spring (44.4, 34.1 mm) occured at Abha and
Analysis of Rainfall over Saudi Arabia 69
Khamis Meshet, respectively. Figure 5(a) shows the average amounts of rainfall during the summer in KSA.
Fig. 2(a). Annual rainfall amounts at the Turaif, Guriat, Arar, Aljouf, Rafha, Tabouk,
Alqaisoma and Hafr Albaten stations during the available period for each station.
Turaif
0
5
10
15
20
25
30
1978 1982 1986 1990 1994 1998 2002
Pre
cip
itati
on
(m
m)
Guriat
0
1
2
3
4
5
6
7
8
9
1985 1988 1991 1994 1997 2000 2003
Pre
cip
itati
on
(m
m)
Arar
0
2
4
6
8
10
12
1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
itati
on
(m
m)
Aljouf
0
1
2
3
4
5
6
7
8
9
1978 1981 1984 1987 1990 1993 1996 1999 2002
Pre
cip
itati
on
(m
m)
Rafha
0
2
4
6
8
10
12
14
16
1970 1973 1976 1979 1982 1985 1988 1991 1994
Pre
cip
ita
tio
n (
mm
)
Tabouk
0
1
2
3
4
5
6
7
8
1978 1981 1984 1987 1990 1993 1996 1999 2002
Pre
cip
ita
tio
n (
mm
)
Alqaisoma
0
5
10
15
20
25
1978 1981 1984 1987 1990 1993 1996 1999 2002
Pre
cip
ita
tio
n (
mm
)
Hafr Albaten
0
5
10
15
20
25
30
1990 1992 1994 1996 1998 2000
Pre
cip
ita
tio
n (
mm
)
70 A. Mashat and H. Abdel Basset
Fig. 2(b). Annual rainfall amounts at the Hail, Qassim, Dhahran, Alwajh, Alahsa, New
Riyadh, Old Riyadh and Madinah stations.
Hail
0
5
10
15
20
25
30
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Qassim
0
5
10
15
20
25
30
35
40
45
1978 1981 1984 1987 1990 1993 1996 1999 2002
Pre
cip
ita
tio
n (
mm
)
Dhahran
0
5
10
15
20
25
30
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Alwajh
0
2
4
6
8
10
12
14
1978 1981 1984 1987 1990 1993 1996 1999 2002
Pre
cip
ita
tio
n (
mm
)
Alahsa
0
5
10
15
20
25
1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Riyadh New
0
5
10
15
20
25
30
1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Riyadh Old
0
5
10
15
20
25
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Madinah
0
2
4
6
8
10
12
14
16
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Analysis of Rainfall over Saudi Arabia 71
Fig. 2(c). Annual rainfall amounts at the Yanbo, Jeddah, Taif, Makkah, Wadi Aldwaser,
Albaha, Bisha and Khamis Moshet stations.
Yanbo
0
1
2
3
4
5
6
7
8
1978 1981 1984 1987 1990 1993 1996 1999 2002
Pre
cip
ita
tio
n (
mm
)
Jeddah
0
5
10
15
20
25
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Taif
0
5
10
15
20
25
30
35
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Makkah
0
5
10
15
20
25
1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Wadi Aldwaser
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
1991 1993 1995 1997 1999 2001 2003
Pre
cip
ita
tio
n (
mm
)
Albaha
0
5
10
15
20
25
30
1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Bisha
0
5
10
15
20
25
30
35
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Khamis Moshet
0
5
10
15
20
25
30
35
40
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
72 A. Mashat and H. Abdel Basset
Fig. 2(d). Annual rainfall amounts at the Abha, Najran, Sharorah and Gizan stations.
It indicates that the lowest amount of rainfall in KSA falls is during the summer. Except the southwest area, the amount of rainfall in the summer in the other areas is very low. The maximum amount of rainfall in the summer occurs at Abha (16.3 mm) and Khamis Meshet (23.4 mm). Figure 5(b) presents the average amounts of rainfall during the autumn in KSA. It indicates that six stations have an average amount greater than 10 mm (Hail, Hafr Elbaten, Qaisoma, Makkah, Taif and Gizan). The northwest and the southwest areas may be considered to be drier areas during autumn.
4. Conclusion
In this paper, the climatology of monthly and annual rainfall in the
Kingdom of Saudi Arabia has been analyzed using the available data
from 29 meteorological stations. The mean amount of annual rainfall
seems to be homogeneous except at the Tabouk and Sharorah stations,
according to the Bartlet test with a 95% significance level. Analysis of
these data shows that the highest amounts of rainfall occur during the
Abha
0
5
10
15
20
25
30
35
40
45
50
1978 1981 1984 1987 1990 1993 1996 1999 2002
Pre
cip
ita
tio
n (
mm
)
Najran
0
5
10
15
20
25
1978 1981 1984 1987 1990 1993 1996 1999 2002
Pre
cip
ita
tio
n (
mm
)
Sharora
0
2
4
6
8
10
12
14
16
18
20
1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Gizan
0
5
10
15
20
25
30
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003
Pre
cip
ita
tio
n (
mm
)
Analysis of Rainfall over Saudi Arabia 73
Fig. 3: A) The names and positions of KSA meterological stations, B) The average amounts
of rainfall at KSA stations.
74 A. Mashat and H. Abdel Basset
Fig. 4: A) The average amounts of rainfall during the winter in KSA, B) The average
amounts of rainfall during the spring in KSA.
Analysis of Rainfall over Saudi Arabia 75
Fig. 5: A) The average amounts of rainfall during the summer in KSA, B) The average
amounts of rainfall during the autumn in KSA.
76 A. Mashat and H. Abdel Basset
spring in the southwest, middle and east regions of KSA. The second
highest amounts of rainfall occur during the winter in the east and
northeast of KSA. Summer is the season of lowest rainfall in KSA,
where, except in the mountainous area in the southwest region, the
amount of rainfall is very low. While the horizontal distribution pattern
of rainfall in the autumn is somewhat similar to that of in the spring, the
amount of rainfall in the autumn is less than in spring.
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78 A. Mashat and H. Abdel Basset
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