Extraction of present isothermal lines of the basin:
The current isothermal lines from the data of the studied stations extracted using temperature and height data were obtained for 30 years from 1989 to 2020 in the basin from the Meteorological Organization of Iran via (http://www.irimo.ir) (Fig. 3). The correlation between the average annual temperature and the height of the stations was analyzed using linear regression technique as follows:
y=-0.0041X + 19.529 (3)
In Eq. (3), Y denotes the present temperature in ˚C and X represents the height in meters above sea level from DEM, -0.0041 is the adiabatic laps rate in the Gharaghom basin, and 19.529 shows the constant coefficient of the regression model.
According to the regression model, the temperature would drop by about 0.41 for every hundred meter increase in the studied area. We calculated the average annual temperature for the statistical period of 30 years in the area in each pixel using the raster calculator command in the Arc map environment, and further prepared the map of the present average annual temperature. Based on the available data from stations, the highest average annual temperature is 18.65 ˚C in the lowlands and the lowest temperature is 6.11 ˚C in the mountainous areas of the basin. Binaloud, Bal Havan, Donkh, and Koh Chaman have been fenced off, and seasonal rivers such as Golmkan, Donkh, Kuchak, Daulat Abad originate from these mountains. Figure 4 displays the state of the isothermal lines for the average annual temperature in the region. Thus, the lowest temperatures can be seen in the mountainous areas of the basin.
Reconstruction Of The Late Pleistocene Climatic Condition In Gharaghom Basin:
To reconstruct the Quaternary ELA, we prepared the map of geomorphological units in the study area (Fig. 6). Based on the shape of the curve lines, climatic processes were identified, so the morphological forms of glacial cirques were determined. Glacial cirques can be seen in mountainous areas and their evidence such as glacier tills and moraines are evident in downstream and can be easily identified during field visits. Figure 5 reveals a view of glacier cirques and the evidence of Quaternary glaciers on the slope of the Binaloud Mountain range in the basin.
According to Wright's method, the glacial cirques were identified in the basin (Fig. 6). In this work, we identified 174 cirques in the Gharaghom catchment which include 124 cirques in the northern direction and 50 cirques in the southern direction (Table 5, 6). The ELA in the last glacial period is 2160 m on the northern slopes and 2380 m on the southern slopes. In general, the average ELA for the basin is about 2200 m. This height value for the snow boarder height has been obtained without considering the geographical direction of the glacier cirques. According to the placement of ELA in Eq. (2), it is clear that the present temperature of the border snow line is estimated at 10.5 ˚C based on Wright's method.
The value of 10.5 for the contour of 2200 meters at present and consideration of the temperature of ELA in the late Pleistocene period shows that there is a temperature difference of 10.5 ˚C from the Pleistocene to the present, and the average annual temperature in the basin was 10.5 degrees colder than the present temperature. We reconstructed the average annual temperature in the Pleistocene by subtracting this value of temperature difference from the present temperature of the stations (Table 7). By re-fitting the regression between the temperature of the Pleistocene period and the height of the stations, a regression model (Eq. 4) is obtained. Further, by applying the model into the DEM, the average annual temperature digital model is obtained for the Pleistocene period, and finally isothermal lines are extracted (Fig. 7).
T = -0.0041 H + 9.0293 (4)
T is the paleo air temperature in ˚C and H is the height in meters above sea level.
According to Fig. 7, the present air temperature in the eastern parts of the Gharaghom basin, which are in the form of a plain, is about 10 ˚C higher than in the past, and the ancient air temperature has reached 4 ˚C in these plains. In general, since the mountainous parts are located in the western half of the basin, the present and past air temperatures are increasing from the west to the east of the basin (Fig. 7). Based on data recorded from 1989–2020, the lowest and the highest average annual temperature in the basin is 6.1 and 18.66 ˚C respectively. Thus, the present temperature difference between the western and eastern parts of the basin is about 12.56 ˚C in the basin. On the other hand, based on the reconstruction of past air temperature, the highest average annual temperature was around 8 ˚C and the lowest average annual temperature was − 4 ˚C, so this difference was slightly less around 12 ˚C in the past. Reconstructing the Quaternary ELA by Wright's method and the past temperature in the past as well as comparing the past temperature differences of the eastern and western half of the basin with present temperature differences in the basin indicated that the basin is more affected by global warming in the present compared with the past. Jafari and Hazrati (2020) also estimated the lowest Quaternary ELA for the north and northeast, as well as the highest ELA for the central basin of Iran. The reconstructed ELA in the Gharaghom basin agrees with the results of Jafari and HAzrati (2020).
Table 5
The frequency of glacier cirques based on cirque-floor altitude and elevation ratios
row
|
Elevation
|
Cirque frequency
|
row
|
Elevation
|
Cirque frequency
|
1
|
213–313
|
0
|
14
|
1513–1613
|
2
|
2
|
313–413
|
0
|
15
|
1613–1713
|
9
|
3
|
413–513
|
0
|
16
|
1713–1813
|
15
|
4
|
513–613
|
0
|
17
|
1813–1913
|
19
|
5
|
613–713
|
0
|
18
|
1913–2013
|
10
|
6
|
713–813
|
1
|
19
|
2013–2113
|
21
|
7
|
813–913
|
2
|
20
|
2113–2213
|
20
|
8
|
913–1013
|
0
|
21
|
2213–2313
|
22
|
9
|
1013–1113
|
1
|
22
|
2313–2413
|
15
|
10
|
1113–1213
|
2
|
23
|
2413–2513
|
11
|
11
|
1213–1313
|
5
|
24
|
2513–2613
|
7
|
12
|
1313–1413
|
1
|
25
|
2613–2713
|
2
|
13
|
1413–1513
|
11
|
--
|
--
|
--
|
Table 6
Status of the geographical direction of glacier cirques in the highlands of the Gharaghom basin
FID
|
aspect
|
elevation
|
FID
|
aspect
|
elevation
|
FID
|
aspect
|
elevation
|
FID
|
aspect
|
elevation
|
FID
|
aspect
|
elevation
|
0
|
N-E
|
2720
|
39
|
E-W
|
2240
|
79
|
W-N
|
2300
|
120
|
W-N
|
2440
|
160
|
W-N
|
2520
|
1
|
N-E
|
2840
|
40
|
E-W
|
2320
|
80
|
N
|
2200
|
121
|
W-N
|
2440
|
161
|
E-W
|
2520
|
2
|
N-E
|
2920
|
41
|
E-W
|
2280
|
81
|
W-N
|
2540
|
122
|
W-N
|
2480
|
162
|
W-N
|
2150
|
3
|
W-N
|
2760
|
42
|
W-N
|
2020
|
82
|
S-W
|
2460
|
123
|
W-N
|
3240
|
163
|
E-W
|
2380
|
4
|
N-E
|
2640
|
43
|
E-W
|
1780
|
83
|
W-N
|
2520
|
124
|
W-N
|
2700
|
164
|
W-N
|
2200
|
5
|
E-S
|
2180
|
44
|
W-N
|
1680
|
84
|
W-N
|
2540
|
125
|
E-W
|
2420
|
165
|
N-E
|
2440
|
6
|
N-S
|
2880
|
45
|
N-E
|
1940
|
85
|
N
|
2280
|
126
|
N
|
2620
|
166
|
N
|
2120
|
7
|
W-N
|
3120
|
46
|
N-E
|
1820
|
86
|
E-S
|
2580
|
127
|
W-N
|
2420
|
167
|
W-N
|
2580
|
8
|
W-N
|
2900
|
47
|
N-E
|
1700
|
87
|
W-N
|
2140
|
128
|
E-S
|
2200
|
168
|
E-W
|
2380
|
9
|
E-W
|
1860
|
48
|
N-E
|
1760
|
88
|
W-N
|
2700
|
129
|
S-W
|
2160
|
169
|
E-W
|
2100
|
10
|
N-E
|
1720
|
49
|
W-N
|
1980
|
89
|
N-E
|
2300
|
130
|
E-S
|
2720
|
170
|
W-N
|
2180
|
11
|
W-N
|
1800
|
50
|
E-W
|
1920
|
90
|
S-W
|
2840
|
131
|
E-S
|
2820
|
171
|
W-N
|
1840
|
12
|
N-E
|
1740
|
51
|
W-N
|
1920
|
91
|
S-W
|
2460
|
132
|
E-S
|
2820
|
172
|
W-N
|
1840
|
13
|
N-E
|
1700
|
52
|
N-E
|
1680
|
92
|
W-N
|
1640
|
133
|
E
|
2720
|
173
|
N-E
|
2120
|
14
|
N-E
|
1700
|
53
|
W-N
|
2380
|
93
|
E-W
|
1950
|
134
|
S-W
|
2560
|
174
|
E-W
|
2020
|
15
|
W-N
|
3000
|
54
|
W-N
|
2500
|
94
|
W-N
|
2060
|
135
|
W
|
2460
|
175
|
N-E
|
1900
|
16
|
W-N
|
2460
|
55
|
W-N
|
2440
|
95
|
E-W
|
2000
|
136
|
W-N
|
2420
|
176
|
N-E
|
2020
|
17
|
N-E
|
2700
|
56
|
W-N
|
2480
|
96
|
W-N
|
1960
|
137
|
W-N
|
2400
|
177
|
E-S
|
2420
|
18
|
W-N
|
2700
|
57
|
W-N
|
2240
|
97
|
N-E
|
2000
|
138
|
W-N
|
2180
|
178
|
W-N
|
2320
|
19
|
W-N
|
2700
|
58
|
N-E
|
2400
|
98
|
W-N
|
2100
|
139
|
W-N
|
2400
|
|
|
|
20
|
W-N
|
2620
|
59
|
N-E
|
2240
|
99
|
W-N
|
2080
|
140
|
W-N
|
2360
|
|
|
|
21
|
W-N
|
2560
|
60
|
N-E
|
2340
|
100
|
W-N
|
2020
|
141
|
W-N
|
2200
|
|
|
|
22
|
W-N
|
2340
|
61
|
W-N
|
2240
|
101
|
W-N
|
2060
|
142
|
W-N
|
2140
|
|
|
|
23
|
W-N
|
2220
|
62
|
W-N
|
2060
|
102
|
W-N
|
1960
|
143
|
W-N
|
1820
|
|
|
|
24
|
W-N
|
2620
|
63
|
N-E
|
2520
|
103
|
W-N
|
1840
|
144
|
S-W
|
1760
|
|
|
|
25
|
N-E
|
1740
|
64
|
W-N
|
2420
|
104
|
N-E
|
920
|
145
|
E-W
|
2480
|
|
|
|
26
|
N-E
|
1760
|
65
|
W-N
|
2040
|
105
|
E-W
|
1020
|
146
|
W-N
|
2800
|
|
|
|
27
|
W-N
|
1640
|
66
|
W-N
|
2060
|
106
|
W-N
|
1060
|
147
|
N-E
|
2860
|
|
|
|
28
|
W-N
|
1640
|
67
|
N-E
|
2220
|
107
|
S-W
|
2420
|
148
|
W-N
|
2480
|
|
|
|
29
|
E-W
|
1880
|
68
|
E-W
|
2160
|
108
|
S-W
|
2560
|
149
|
N-E
|
2360
|
|
|
|
30
|
E-W
|
1980
|
69
|
W-N
|
2160
|
109
|
E-S
|
2700
|
150
|
E-W
|
2600
|
|
|
|
31
|
E-W
|
1380
|
70
|
S-W
|
2940
|
110
|
W-N
|
2820
|
151
|
E-W
|
2640
|
|
|
|
32
|
N-E
|
1340
|
71
|
E-S
|
2780
|
111
|
E-S
|
2180
|
152
|
E-W
|
2940
|
|
|
|
33
|
N-E
|
1240
|
72
|
N-E
|
2560
|
112
|
S-W
|
2640
|
153
|
W-N
|
2920
|
|
|
|
34
|
W-N
|
1980
|
74
|
E-W
|
2620
|
114
|
N-E
|
1960
|
155
|
W-N
|
2820
|
|
|
|
35
|
W-N
|
2300
|
75
|
E-W
|
2600
|
115
|
W-N
|
2060
|
156
|
W-N
|
2760
|
|
|
|
36
|
N-E
|
2260
|
76
|
S-W
|
2780
|
116
|
N-E
|
1520
|
157
|
E-W
|
2720
|
|
|
|
37
|
W-N
|
2240
|
77
|
E-S
|
2660
|
117
|
W-N
|
2380
|
158
|
W-N
|
2860
|
|
|
|
38
|
N-E
|
1980
|
78
|
W-N
|
2660
|
118
|
W-N
|
2300
|
159
|
N-E
|
2500
|
|
|
|
Table 7
Reconstruction of the past temperature based on Wright’s method in the stations.
name
|
elevation
|
x
|
y
|
average annual temperature
|
Past temperature (Degree Celsius)
|
Sarakhs
|
225
|
36.53
|
61.16
|
18.37
|
7.87
|
Neyshabour
|
1213
|
36.26
|
58.8
|
14.19
|
3.69
|
Mashhad
|
1280
|
36.6
|
59.65
|
15.84
|
5.34
|
Golmakan
|
1300
|
36.46
|
59.18
|
13.71
|
3.21
|
Baar
|
1746
|
36.48
|
58.7
|
12.32
|
1.82
|
Asadabaad
|
1770
|
35.65
|
59.35
|
11.74
|
1.24
|
According to Porter's method, the highest frequency of glacier cirques has been located in the altitude class of 2213–2313 m (Table 5), and the reconstructed Quaternary ELA is 2235 m using Eq. (1). Based on Eq. (3), the present temperature is 10.36 ˚C in the basin. Thus, the difference between the past temperature and the present temperature at an altitude of 2235 m is equal to 10.36 based on Porter's method (Table 8). The following linear regression model is defined for obtaining the past temperature using altitude based on Porter’s method (Eq. 5):
T = -0.0041H + 9.1693
|
(5)
|
The above linear equation was used to reconstruct the isothermal lines of the past using Porter's method and finally it has been applied to the DEM in the basin. Figure 8 is the output of this digital temperature model.
Table 8
Reconstruction of past annual average temperature based on Porter's method in the stations.
name
|
elevation
|
x
|
y
|
average annual temperature
|
Past temperature
(Degree Celsius)
|
Sarakhs
|
225
|
36.5333
|
61.1667
|
18.37102
|
8.01
|
Neyshabour
|
1213
|
36.2667
|
58.8
|
14.19932
|
3.84
|
Mashhad
|
1280
|
36.6
|
59.65
|
15.84761
|
5.49
|
Golmakan
|
1300
|
36.4667
|
59.18
|
13.71207
|
3.39
|
Baar
|
1746
|
36.48
|
58.7
|
12.32776
|
1.97
|
Asadabaad
|
1770
|
35.65
|
59.35
|
11.74519
|
1.38
|
The temperature differences from the Pleistocene period to the present time using Wright and Porter's methods have been quantitatively very close to each other and show a temperature difference of 10.5 and 10.36 ˚C respectively. Figure 9 illustrates ELA obtained by two methods. The difference between the two Quaternary ELAs by the Wright and Porter method is 35 meters.
Temperature Prediction By Ann Method:
In this work, the artificial neural network model has been created and trained using the air temperature as the input. The model is trained for predicting the temperature in the next 30 years (2021–2051) in the basin. Table 9 presents the sum of square errors of 0.39 for the proposed ANN model. Figure 10 shows that the predicted temperature values fit accurately with the observed values. Hence, the regression model of the network is satisfactory and reveals the linearity of the relationship between the dependent and independent variables.
The regression model showed 0.19°C increase in temperature based on regression Eq. (6).
Y = 0.19 + 0.99X (6)
Y here is the future mean air temperature as the dependent variable and X functions as the independent variable in ANN regression model.
Table 9
Model Summary
|
Training
|
Sum of Squares Error
|
0.39
|
Average Overall Relative Error
|
0.039
|
Relative Error for Scale Dependents
|
0.064
|
mean
|
0.014
|
Holdout
|
Average Overall Relative Error
|
0.067
|
Relative Error for Scale Dependents
|
0.101
|
|
mean
|
0.029
|
Figure 11 depicts the predicted annual mean temperature for the next 30 years. According to the predictions of ANN, the temperature will rise by 0.19°C. The zoom in the graph shows the difference between the observed mean annual temperatures (1991–2021) with the predicted (2021–2051).