In order to have a general understanding of the agricultural climate indicators of the study area, the long-term averages of the indicators used are given in Table 3. As can be seen in the table, regarding the indicators related to cold, the first FFF occurs on October 16 or early November. Of course, the latest time is in early December in Khorram Abad. Matching the locational features of the stations indicates that in high areas and areas exposed to cold masses, the frost starts earlier than in other areas. At the same time, the LSF pattern also indicates that the stations where frost starts earlier, ends later. Accordingly, the length of the NFD frost period in the region is long and more than 100 days (Hamadan, Urmia, Khoi, Saqqez, Shahrekord) and in between, Shahrekord has the frostiest days with 128.2 days. Regarding the FP index, Shahrekord has the highest value with 195.3 days. The pattern of the AF index also follows the same pattern of the NFD and FP indices, which ranges from − 137.8 in Khorramabad due to the low altitude and low geographical latitude and exposure to relatively mild winds from Iraq to -763.8 The degree in Shahrekord differs due to the high altitude, the exposure to cold masses, the wide mountainous area. At the same time, the period of freezing between FFF and LSF in the intermediate and especially mountainous stations of the region is from early October to the end of April in the southern part (Shahrkord) take a long time. Meanwhile, the last frosts in the region end earlier in the parts that occurred late, but in Saqqez it lasts until the third of May. Based on this, the number of frost days also varies from Shahrekord in terms of altitude from 195 days to 119 days in Khorram Abad. Based on this, it can be concluded that there are more restrictions for planting agricultural products in high and mountainous areas, as well as areas exposed to cold winds. Considering that the frequency, intensity and duration of frost are important factors in determining the possibility of growing different agricultural products (Kalma et al. 2012), therefore, based on the described indicators, it can be said that the southern and western regions of the region The supply of necessary agricultural water has more suitable conditions for the development of cultivation and agriculture. At the same time, Maragheh station also shows suitable conditions in terms of the impact of Lake Urmia, which, of course, with the expansion and continued dryness of Lake Urmia and the change in the local climatic conditions, the ability to grow different crops It can change within the limits of this part of the region. Regarding the heating indicators, as can be seen in the relevant table, almost in most of the stations in the region at the temperature threshold of 5 degrees Celsius, the beginning of the growing season starts from early March and lasts until mid-December (in Khorramabad station due to its location in Geographical latitude and low altitude have completely different conditions and even in some years there is actually a continuation of the growing season). At a temperature threshold of 10 degrees, the growing season begins in April and ends in November, and at a threshold of 15 degrees, the growing season begins in May and ends in October, except in Khorramabad and Arak. The only difference between them is related to the occurrence The temperature threshold is in the first to third decades of the mentioned months. In the same way, the length of the growing season also decreases with the increase of the temperature threshold. In examining the duration of the growing season, at the temperature threshold of 5, 10, and 15 degrees, Khorramabad shows the highest number of days, and Mako and Saqqez show the lowest number of days. Based on this, it can be said that Khorramabad has the best conditions in terms of the growing season has been growing. Although, in terms of the base temperature of 5 degrees, all the stations have had the necessary conditions for growing agricultural products for more than 250 days, in the base temperature of 10 degrees, more than 220 days, and in the base temperature of 15 degrees, more than 140 days. In terms of heat stress indicators, as seen in Table 3, the highest heat stress at the threshold of 25 degrees was in Khorramabad with 182 days, at the threshold of 35 degrees it was 143 days, and at the threshold of 35 degrees it was 94 days. The PHSA index has also followed the same conditions. Examining the GDD index at different temperature thresholds shows that Khorramabad has the highest degree-day and Shahrekord has the lowest degree-day.
Table 3
Average indicators of agricultural climate in selected stations during the statistical period
| Makoo | Khoy | Tabriz | Urmia | Mianeh | Maraghe | Mahabad | Zanjan | Ghazvin | Saghez | Sanandaj | Hamedan | Kermanshah | Arak | Alighodarz | Shahrekord | Khorramabad |
NFD | 105.4 | 100.5 | 91.4 | 110.9 | 86.9 | 77.9 | 79.3 | 79.2 | 82.4 | 121.5 | 92.3 | 115.4 | 78.9 | 88.2 | 97.9 | 128.2 | 56.3 |
FFF | 6-Nov | 5-Nov | 15-Nov | 5-Nov | 16-Nov | 17-Nov | 12-Nov | 12-Nov | 14-Nov | 20-Oct | 5-Nov | 25-Oct | 11-Nov | 23-Nov | 12-Nov | 16-Oct | 07-Dec |
Lsf | 3-Apr | 3-Apr | 31-Mar | 10-Apr | 1-Apr | 30-Mar | 2-Apr | 2-Apr | 5-Apr | 3-May | 5-Apr | 10-Apr | 3-Apr | 7-Apr | 10-Apr | 29-Apr | 05-Apr |
Fp | 148.1 | 149.0 | 136.0 | 156.0 | 136.1 | 133.8 | 141.4 | 141.4 | 141.5 | 194.6 | 151.0 | 167.7 | 143.5 | 135.0 | 149.8 | 195.3 | 119.3 |
AF | -611.9 | -505.3 | -405.0 | -507.7 | -414.7 | -327.8 | -337.6 | -337.8 | -317.9 | -742.8 | -398.2 | -640.6 | -300.0 | -400.0 | -447.2 | -763.8 | -137.8 |
Gss5 | 22-Mar | 10-Mar | 11-Mar | 15-Mar | 2-Mar | 9-Mar | 9-Mar | 9-Mar | 28-Feb | 20-Mar | 29-Feb | 17-Mar | 20-Feb | 10-Mar | 14-Mar | 19-Mar | 19-Jan |
Gse5 | 27-Nov | 5-Dec | 6-Dec | 3-Dec | 12-Dec | 10-Dec | 8-Dec | 7-Dec | 15-Dec | 2-Dec | 16-Dec | 6-Dec | 21-Dec | 17-Dec | 11-Dec | 6-Dec | 28-Dec |
Gss10 | 18-Apr | 8-Apr | 11-Apr | 14-Apr | 31-Mar | 8-Apr | 8-Apr | 8-Apr | 1-Apr | 21-Apr | 6-Apr | 13-Apr | 1-Apr | 12-Apr | 16-Apr | 19-Apr | 23-Mar |
Gse10 | 5-Nov | 11-Nov | 13-Nov | 9-Nov | 17-Nov | 15-Nov | 14-Nov | 14-Nov | 20-Nov | 9-Nov | 19-Nov | 12-Nov | 26-Nov | 28-Nov | 15-Nov | 9-Nov | 10-Dec |
Gss15 | 22-May | 6-May | 10-May | 16-May | 29-Apr | 8-May | 9-May | 10-May | 1-May | 25-May | 5-May | 19-May | 2-May | 10-May | 17-May | 21-May | 26-Apr |
Gse15 | 14-Oct | 21-Oct | 26-Oct | 16-Oct | 29-Oct | 26-Oct | 27-Oct | 26-Oct | 30-Oct | 17-Oct | 28-Oct | 18-Oct | 3-Nov | 8-Nov | 23-Oct | 10-Oct | 15-Nov |
Gsl5 | 250.1 | 269.7 | 270.5 | 263.8 | 285.2 | 276.5 | 274.0 | 273.2 | 290.6 | 256.3 | 290.1 | 264.3 | 305.2 | 282.5 | 272.7 | 262.6 | 344 |
Gsl10 | 201.5 | 216.4 | 216.2 | 209.7 | 231.1 | 221.6 | 220.3 | 220.3 | 232.6 | 201.3 | 226.5 | 213.1 | 238.5 | 230.2 | 213.0 | 204.9 | 261.3 |
Gsl15 | 144.9 | 167.8 | 168.9 | 152.9 | 183.4 | 171.0 | 171.1 | 169.3 | 182.3 | 144.4 | 175.3 | 152.4 | 184.6 | 182.1 | 159.0 | 142.0 | 202.6 |
PHSD25 | 98.1 | 134.7 | 133.2 | 121.4 | 155.3 | 132.7 | 138.0 | 138.0 | 156.8 | 133.7 | 161.4 | 139.8 | 169.6 | 153.1 | 133.3 | 141.3 | 182.1 |
PHSD30 | 36.8 | 79.8 | 82.2 | 55.8 | 109.2 | 82.4 | 82.6 | 82.7 | 111.0 | 85.8 | 119.4 | 92.2 | 129.3 | 106.5 | 83.0 | 87.5 | 142.9 |
PHSD35 | 2.5 | 18.3 | 21.1 | 5.8 | 47.6 | 19.5 | 22.7 | 22.7 | 44.1 | 23.0 | 67.7 | 28.8 | 81.3 | 38.7 | 13.7 | 13.0 | 96.4 |
PHSA25 | 2961.2 | 4260.8 | 4241.2 | 3698.1 | 5125.0 | 4231.2 | 4392.1 | 4393.0 | 5153.8 | 4291.0 | 5455.6 | 4502.7 | 5825.3 | 5012.4 | 4211.6 | 4416.2 | 6379.7 |
PHSA30 | 1296.5 | 2770.3 | 2854.2 | 1931.1 | 3879.2 | 2858.0 | 2919.1 | 2920.0 | 3928.7 | 3000.8 | 4320.2 | 3207.9 | 4725.2 | 3746.8 | 2873.4 | 2954.1 | 5331.8 |
PHSA35 | 121.9 | 769.6 | 850.6 | 243.3 | 1896.1 | 808.0 | 935.9 | 935.9 | 1785.4 | 980.7 | 2661.7 | 1168.8 | 3175.4 | 1595.6 | 601.4 | 517.8 | 3820.0 |
GDD5 | 2861.1 | 3317.8 | 3519.9 | 2953.8 | 3812.2 | 3547.2 | 2872.6 | 3417.0 | 3730.2 | 2829.9 | 3505.7 | 3032.1 | 3939.5 | 3742.6 | 3223.1 | 2804.8 | 4412.6 |
GDD10 | 1735.4 | 2090.8 | 2306.2 | 1789.4 | 2541.3 | 2310.3 | 2029.3 | 2163.9 | 2423.1 | 1681.4 | 2231.8 | 1848.6 | 2570.2 | 2452.9 | 2013.8 | 1627.2 | 2917.9 |
GDD15 | 872.7 | 1128.6 | 1341.0 | 895.0 | 1516.6 | 1338.5 | 1186.0 | 1185.7 | 1390.5 | 821.2 | 1233.7 | 941.5 | 1514.3 | 1428.4 | 1081.8 | 756.0 | 1775.8 |
Trend analysis
Cooling indices
Table 4 shows the trend of changes in climatic indicators used in this research according to the Mann-Kendall method and the age slope estimator. As can be seen in the table, the LSF index has a negative trend at the confidence level of more than 95% in Khorramabad (located in the southern part of the region) and this is while in Table 5, at the same confidence level in the ITA method of this station along with other stations Saqqez, Sanandaj, Arak, and Aligudarz also have a negative trend and the decreasing rate (Slope Sense) of the glacial period shows a retrograde between − 0.13 in Kermanshah and − 1.52 days per decade in Khorram Abad. Of course, the trend is positive. It can also be seen in some stations in Table 5 that it has a low rate. At the same time, according to Table 4, the FFF index has a negative trend only in Khorramabad and the rest of the stations show a positive trend. Of course, in the ITA method, Urmia and Shahr Kurd They also show a negative trend, in which Khorramabad has a change slope of -0.93 days per decade. In other stations, there is a positive trend, the highest rate of which is in the northern station of the region, i.e., in Khoi, with a change slope of 0.57 days per decade. The negative trend of this index indicates the progress of the glacial period from autumn to winter, and the positive trend indicates the shift from winter to autumn or early winter. Based on this, the FP index, which is actually the number of days between FFF and LSF, in more than 10 stations in the region at the confidence level of 95% and above, there is a negative trend in the ITA method, and its rate of change varies between − 0.94 in turpentine and − 0.11 in Aligudarz. Of course, the most negative values are in the northern and mountainous part of the region and the middle part. These changes in the Kendall method are significant only in 3 stations, although the rate of change is slightly different from the ITA method. Meanwhile, the highest positive rate of changes in the southern part of the region has occurred in Kurd City at the rate of 0.77 days per decade. Of course, positive values of changes are obtained in high and mountainous areas or in areas exposed to cold masses. The investigation of the NFD index also shows that according to the ITA method, in all stations except Shahrekord, there is a negative trend and the number of changes is between 0.11 in Urmia and It is 1/17 in Arak. These conditions are almost the same according to Mann Kendall's method with a slight difference in the rate of change. In Kendal, it can be seen that there is a positive trend in the stations with a significant trend, and the slope of changes is between 2.66 degrees in Khorramabad to 7.11 degrees in Aligudarz in the south of the region and 3.96 degrees in Qazvin to 9.18 degrees in Mako. Based on this, it indicates an increase in the degree and a decrease in the severity of frost. This index is shown in a more specific way by the ITA method and the slope of the negative trend indicates a decrease in the negative values of this index and indicates the mixing of cooling characteristics, but the amount of its slope change in the north of the region is between 6.65 degrees in the middle (in the north of the region) is up to 7.42 degrees in Aligudarz (in the south of the region). Certainly, these changes are caused by the decrease in NFD and FP indices and indicate a decrease in frost intensity even in the high stations of the region.
Table 4
Changes in agricultural climate indicators in selected stations according to Mann Kendall method and sen’s slope estimator at the confidence level of 95% and above
| | Makoo | Khoy | Tabriz | Urmia | Miyaneh | Maraghe | Mahabad | Zanjan | Qazvin | Saqqez | Sannandaj |
LSF | z | - | - | - | - | - | - | - | - | - | - | - |
Q | - | - | - | - | - | - | - | - | - | - | - |
FFF | z | 2.05* | - | - | - | - | - | - | - | - | - | - |
Q | 0.41 | - | - | - | - | - | - | - | - | - | - |
NFD | z | -3.57*** | -2.65** | -2* | - | -2.76** | -2.08* | - | - | -2.33* | -2.45* | -2.34** |
Q | -0.87 | -0.86 | -0.43 | - | -1 | -0.7 | - | - | -0.7 | -0.85 | -0.61 |
Fp | z | -2.21* | -2.89** | - | - | - | - | - | - | - | - | - |
Q | -0.69 | -1.00 | - | - | - | - | - | - | - | - | - |
AF | z | 3.05* | - | - | - | 2.35* | − | - | - | 2.55* | − | 2.11** |
Q | 9.18 | - | - | - | 8.64 | - | - | - | 3.96 | - | 5.77 |
PHSD25 | z | 2.97** | 3.42** | 3.02** | 3.80*** | 2.56* | 4.65*** | 2.88** | 2.91** | 1.24*** | 2.02* | 2.73** |
Q | 0.56 | 0.55 | 0.57 | 0.79 | 0.41 | 1.00 | 0.60 | 0.60 | 0.62 | 0.30 | 0.53 |
PHSD30 | z | 2.97** | 4.66*** | 3.25** | 4.00*** | 3.69*** | 5.57*** | 4.47*** | 4.49*** | 3.62*** | 2.71** | 3.64*** |
Q | 0.83 | 1.20 | 0.57 | 1.14 | 0.80 | 1.22 | 1.09 | 1.09 | 0.70 | 0.56 | 0.7 |
PHSD35 | z | 3.27** | 4.90*** | 3.37*** | 3.25** | 3.86*** | 4.33*** | 4.02*** | 4.02*** | 3.29*** | 2.49* | 5.55*** |
Q | 0.13 | 1.00 | 0.68 | 0.29 | 1.00 | 0.97 | 0.82 | 0.82 | 0.85 | 0.47 | 1.19 |
PHSA25 | z | 3.12** | 4.18*** | 3.29*** | 4.06*** | 3.73*** | 5.14*** | 3.61*** | 3.61*** | 3.52*** | 2.19* | 3.98*** |
Q | 19.98 | 25.70 | 19.68 | 29.21 | 21.88 | 36.92 | 22.87 | 22.87 | 21.62 | 14 | 24.95 |
PHSA30 | z | 2.87** | 4.54*** | 3.24** | 4.06*** | 3.67*** | 5.34*** | 3.86*** | 3.86*** | 3.38*** | 2.05** | 4.54*** |
Q | 26.13 | 44.19 | 21.29 | 39.29 | 28.92 | 39.50 | 36.77 | 36.75 | 23.41 | 15.92 | 31.4 |
PHSA35 | z | 2.91** | 4.54*** | 2.95** | 2.90** | 3.67*** | 4.06*** | 3.66*** | 3.66*** | 3.21** | - | 5.71*** |
Q | 5.68 | 37.27 | 22.92 | 10.64 | 36.16 | 35.86 | 28.26 | 28.26 | 29.10 | - | 47.99 |
GDD5 | z | 4.2*** | 5.06*** | 3.44*** | 3.64*** | 4.48*** | 5.2*** | 4.09*** | 4.60*** | 4.10*** | 2.53* | 5*** |
Q | 13.98 | 20.42 | 11.65 | 12.38 | 18.66 | 21.86 | 16.27 | 16.33 | 16.36 | 9.84 | 16.83 |
GDD10 | z | 4.23*** | 5.42*** | 3.58*** | 3.75*** | 4.63*** | 5.31*** | 4.15*** | 4.29*** | 4.40*** | 2.41* | 5.2*** |
Q | 11.58 | 17.92 | 9.72 | 9.44 | 15.04 | 18.23 | 13.92 | 13.54 | 13.63 | 8.10 | 15.43 |
GDD15 | z | 4.06*** | 5.42*** | 3.72*** | 3.44*** | 4.51*** | 5.57*** | 4.35*** | 4.35*** | 3.98*** | 2.36* | 5.06*** |
Q | 8.5 | 15.06 | 7.94 | 7.29 | 12.32 | 14.59 | 11.07 | 11.07 | 8.06 | 6.04 | 12.46 |
Gss5 | z | - | -3.22** | -3.31*** | -3.04** | -2.90** | -4.27*** | -3.73*** | -4.08*** | -2.76** | -3.02** | -3.02** |
Q | - | -0.90 | -0.79 | − .70 | -1.07 | -1.31 | -1.04 | -1.10 | -1.00 | -0.89 | -0.89 |
Gse5 | z | - | - | - | - | - | - | - | - | - | − | - |
Q | - | - | - | - | - | - | - | - | - | - | - |
Gss10 | z | - | - | - | -2.80** | -2.7** | - | -2.90** | -2.00* | -2.22* | - | -2.13* |
Q | - | - | - | -0.59 | -0.69 | - | -0.40 | -0.29 | -0.38 | - | -0.31 |
Gse10 | z | - | - | - | - | - | - | - | - | - | − | - |
Q | - | - | - | - | - | - | - | - | - | - | - |
Gss15 | z | - | -2.66** | - | -2.03* | - | -2.39* | - | -2.16* | - | - | - |
Q | - | -0.54 | - | -0.33 | - | -0.42 | - | -0.45 | - | - | - |
Gse15 | z | - | - | - | - | - | 2.05* | - | - | - | - | - |
Q | - | - | - | - | - | 0.25 | - | - | - | - | - |
Gsl5 | z | 2.47* | 3.69*** | 2.53* | 2.14* | - | 4.54*** | 3.39*** | 3.39*** | 2.26* | - | 2.31* |
Q | 0.72 | 1.00 | 0.79 | 0.65 | - | 1.79 | 1.43 | 1.31 | 0.82 | - | 0.83 |
Gsl10 | z | - | - | - | 2.10* | 2.32* | 2.00* | - | - | - | - | 2.40* |
Q | - | - | - | 0.47 | 0.65 | 0.46 | - | - | - | - | 0.4 |
Gsl15 | z | - | 3.10** | - | 2.50* | - | 3.65*** | - | 2.53* | - | - | - |
Q | - | 0.70 | - | 0.40 | - | 0.70 | - | 0.66 | - | - | - |
| | Hamedan | Kermanshah | Arak | Aligudarz | Shahrekord | Khorramabad |
LSF | z | - | - | - | - | - | -4.39*** |
Q | - | - | - | - | - | -1.57 |
FFF | z | 2.53* | 2.21* | - | - | - | -2.42* |
Q | 0.39 | 0.43 | - | - | - | -0.68 |
NFD | z | -3.35*** | -2.77* | -3.81*** | -2.84** | 2.52* | -2.85** |
Q | -0.76 | -0.6 | -1.10 | -0.71 | 0.4 | -0.71 |
Fp | z | -− | - | - | - | 2.15* | -3.13** |
Q | - | - | - | - | 0.73 | -1 |
AF | z | - | 2.13* | - | 2.56* | - | 2.49* |
Q | - | 3.92 | - | 7.11 | - | 2.66 |
PHSD25 | z | 2.40* | 2.34* | 2.7** | 2.13* | 3.37** | - |
Q | 0.36 | 0.48 | 0.53 | 0.38 | 0.55 | - |
PHSD30 | z | 4.22*** | 2.51* | 3.98*** | 3.59*** | 3.61*** | 2.91** |
Q | 0.70 | 0.43 | 0.69 | 0.78 | 0.83 | 0.43 |
PHSD35 | z | 3.49*** | 4.02*** | 4.27*** | - | 2.94** | 4.63*** |
Q | 0.81 | 0.79 | 0.97 | - | 0.48 | 0.81 |
PHSA25 | z | 3.61*** | 2.95** | 3.52*** | 2.16* | 3.98*** | 2.79** |
Q | 14.87 | 18.39 | 21.18 | 11.19 | 20.03 | 17.93 |
PHSA30 | z | 4.43*** | 3.18** | 4.32*** | 3.53*** | 3.44*** | 3.72*** |
Q | 24.30 | 19.27 | 23.80 | 22.03 | 27.08 | 20.67 |
PHSA35 | z | 3.10** | 3.78*** | 3.61*** | - | 3.04** | 4.57*** |
Q | 25.71 | 29.94 | 30.28 | − | 19.2 | 30.76 |
GDD5 | z | 4.74*** | 4.20*** | 4.15*** | 4.06*** | - | 4.97*** |
Q | 13.18 | 16.36 | 14.09 | 11.47 | - | 21.24 |
GDD10 | z | 4.69*** | 4.60*** | 4.46*** | 4.09*** | - | 5.25*** |
Q | 11.08 | 13.63 | 11.09 | 8.75 | - | 19.68 |
GDD15 | z | 5.54*** | 4.52*** | 4.86*** | 4.3*** | - | 5.4*** |
Q | 8.55 | 11.47 | 8.8 | 6.75 | - | 17.18 |
Gss5 | z | -2.61** | -2.16* | -1.66+ | - | - | -1.99* |
Q | -0.83 | -0.72 | -0.75 | - | - | -0.17 |
Gse5 | z | - | - | - | - | - | - |
Q | - | - | - | - | - | - |
Gss10 | z | - | - | - | - | - | -3.2** |
Q | - | - | - | - | - | -0.96 |
Gse10 | z | - | - | - | - | - | -3.05** |
Q | - | - | - | - | - | -0.7 |
Gss15 | z | - | - | - | -2.06* | - | -3.62*** |
Q | - | - | - | -0.3 | - | -1 |
Gse15 | z | - | 2.61** | - | - | - | -2.85** |
Q | - | 0.92 | - | - | - | -0.41 |
Gsl5 | z | - | - | - | - | - | - |
Q | - | - | - | - | - | - |
Gsl10 | z | - | - | - | 2.03* | - | - |
Q | - | - | - | 0.47 | - | - |
Gsl15 | z | 2.29* | - | - | 2.21* | - | 1.97* |
Q | 0.50 | - | - | 0.54 | - | 0.62 |
* 95% confidence level, ** 99% confidence level, *** 99.99% confidence level
Heating indices
Another group of agricultural climate indicators that were used in this research are heating indices. Although there is no specific method for the indicators of the beginning and end of the growing season, and different researchers have used different methods, but in this research, the onset of the growing season It is based on the occurrence of the average temperature in the thresholds of 5, 15, 10 degrees in 6 consecutive days and the end of it is based on the occurrence of the average temperature lower than the above thresholds in 6 consecutive days. Based on this, in the temperature threshold of 5 degrees, most of the stations have a negative trend. In other words, the start date of the growing season has been delayed by a period of 6 days, and its beginning happens earlier. As the value of the age slope is from − 0.17 in Khorram Abad to -1.31 in Maragheh. On the other hand, the index of the end of the growing season at a temperature threshold of 5 degrees is not significant in Kendall's method, but in the ITA method, except for Sanandaj, Kermanshah and Arak stations, which are not significant in the 95% confidence interval, but in other stations and of course, except in the stations that go are negative, it has a positive trend, and the slope of changes is between 0.14 days in Urmia and 0.36 days in Zanjan (0.34 days in Maragheh), which of course is a small rate. The same low rate of changes for stations with There is also a negative trend. Regarding the beginning of the growing season, at a temperature threshold of 10 degrees, it has almost the conditions of GSS5. Although according to Kendall's method, the trend of changes is not significant, but there is a negative trend in Urmia, Mahabad, Zanjan, Miyaneh and Qazvin stations in the northern part of the region and Sanandaj and Shahrekord stations (almost high stations), which indicates that the beginning of the growing season has been pushed back at this threshold. It is a temperature. The same conditions have a negative trend in the ITA method, except for Tabriz. In Kendall's method, the range of changes in the negative trend varies between − 0.29 days in Zanjan and − 0.96 days in Khorramabad. According to the ITA method, the slope of these changes varies between − 0.15 days in Khoi and − 1.35 days in Khorramabad. Perhaps the low latitude of Khorramabad has provided the ground for intensifying this issue. At the same time, the end of the growing season at the above temperature threshold (GSE10) only in Khorramabad according to Kendall's method shows a negative trend with the number of changes in the age gradient of -0.96 It shows that it indicates a time reversal of the end of the growing season at this temperature threshold. At the same time, according to the ITA method, 10 stations show a trend of negative changes with a slope of -0.14 in Mahabad to -0.74 in Khorramabad, while the positive values show a small rate, and in other words, the index The most trend of changes is in Khorram Abad and with a negative trend.
Table 5
Changes in agricultural climate indicators in selected stations according to the ITA method at a confidence level of 95% and above
| | Maku | Khoy | Tabriz | Urmia | Miyaneh | Maragheh | Mahabad | Zanjan | Qazvin | Saqqez |
LSF | D | -0.56 | -0.56 | 0.37 | 0.46 | 0.42 | - | 0.12 | - | 0.038 | -0.64 |
S | -0.31 | -0.31 | 0.19 | 0.26 | 0.23 | - | 0.06 | - | 0.21 | -0.48 |
FFF | D | 0.28 | 0.32 | - | -0.15 | - | - | - | - | 0.18 | 0.27 |
S | 0.51 | 0.57 | - | -0.28 | - | - | - | - | 0.34 | 0.46 |
NFD | D | -1.16 | -1.13 | -0.37 | -0.16 | -1.23 | -0.73 | -1.06 | -1.05 | -1.15 | -1.09 |
S | 0.76 | -0.71 | -0.2 | -0.11 | -0.71 | -0.35 | -0.52 | -0.52 | -0.59 | -0.83 |
Fp | D | -0.9 | -0.96 | 0.26 | 0.61 | 0.19 | - | 0.12 | 0.12 | -0.16 | -0.79 |
S | -0.82 | -0.88 | 0.2 | 0.54 | 0.16 | - | 0.1 | 0.1 | -0.13 | -0.94 |
AF | D | -1.08 | -0.49 | - | 0.6 | -2.25 | - | -0.77 | -0.77 | -2 | -1.4 |
S | 4.01 | 1.48 | - | -1.75 | 6.65 | - | 1.59 | 1.59 | 4.17 | 6.57 |
PHSD25 | D | 0.75 | 0.95 | 0.71 | 1.13 | 0.59 | 1.52 | 0.73 | 0.74 | 0.79 | 0.57 |
S | 0.42 | 0.72 | 0.54 | 0.76 | 0.55 | 1.1 | 0.57 | 0.57 | 0.7 | 0.43 |
PHSD30 | D | 3.54 | 2.88 | 1.55 | 4.19 | 0.97 | 3.09 | 2.97 | 2.98 | 1.17 | 1.14 |
S | 0.64 | 1.17 | 0.69 | 1.12 | 0.63 | 1.28 | 1.25 | 1.25 | 0.72 | 0.54 |
PHSD35 | D | 13.6 | 15.95 | 5.78 | 19.4 | 3.08 | 11.17 | 6.93 | 6.93 | 3.26 | 1.98 |
S | 0.12 | 0.93 | 0.55 | 0.34 | 0.79 | 0.8 | 0.67 | 0.67 | 0.72 | 0.24 |
PHSA25 | D | 0.86 | 1.17 | 0.83 | 1.33 | 0.72 | 1.68 | 0.87 | 0.88 | 0.83 | 0.56 |
S | 14.19 | 27.55 | 19.81 | 27.05 | 22.36 | 38.39 | 21.59 | 21.7 | 24.17 | 13.66 |
PHSA30 | D | 2.96 | 3 | 1.58 | 3.99 | 1.01 | 2.82 | 2.47 | 2.48 | 1.02 | 0.88 |
S | 19.38 | 42.06 | 24.56 | 37.3 | 23.14 | 41.1 | 37.53 | 37.6 | 22.34 | 14.79 |
PHSA35 | D | 9.33 | 13.64 | 4.76 | 13.41 | 2.97 | 9.05 | 5.16 | 5.16 | 2.41 | 0.74 |
S | 4.38 | 35.85 | 19.21 | 11.43 | 30.32 | 28.73 | 22.14 | 22.13 | 22.37 | 4.07 |
GDD5 | D | 0.77 | 1.11 | 0.59 | 0.63 | 0.79 | 1.22 | 1.05 | 0.9 | 0.66 | 0.5 |
S | 12.45 | 20.42 | 11.88 | 10.58 | 18.11 | 24.01 | 16.88 | 17.26 | 13.92 | 8.13 |
GDD10 | D | 0.99 | 1.52 | 0.72 | 0.78 | 0.97 | 1.56 | 1.24 | 1.17 | 0.78 | 0.62 |
S | 9.56 | 17.32 | 9.45 | 7.87 | 14.66 | 19.59 | 13.91 | 14.1 | 10.69 | 5.96 |
GDD15 | D | 1.4 | 2.45 | 0.99 | 1.03 | 1.33 | 2.15 | 1.71 | 1.71 | 1.09 | 0.8 |
S | 6.67 | 14.4 | 7.45 | 5.12 | 11.76 | 15.22 | 10.93 | 10.98 | 8.45 | 3.7 |
Gss5 | D | -0.33 | -1.78 | -1.76 | -1.71 | -2.18 | -2.95 | -2.63 | -2.79 | -2.47 | -0.94 |
S | -0.16 | -0.79 | -0.79 | -0.81 | -0.94 | -1.39 | -1.23 | -1.3 | -0.98 | -0.46 |
Gse5 | D | 0.12 | 0.17 | 0.73 | 0.07 | 0.07 | 0.17 | 0.22 | 0.18 | -0.13 | 0.08 |
S | 0.23 | 0.34 | 0.15 | 0.14 | 0.15 | 0.34 | 0.43 | 0.36 | -0.28 | 0.16 |
Gss10 | D | -0.5 | -0.25 | - | -1.05 | -1.1 | -0.76 | -0.97 | 0.75 | -0.97 | -0.25 |
S | -0.33 | -0.15 | - | -0.65 | -0.65 | -0.46 | -0.58 | 0.44 | -0.54 | -0.14 |
Gse10 | D | - | 0.11 | -0.08 | - | - | 0.04 | -0.07 | -0.07 | -0.13 | -0.15 |
S | - | 0.2 | -0.15 | - | - | 0.08 | -0.14 | -0.14 | -0.25 | -0.28 |
Gss15 | D | -0.14 | -0.64 | - | -0.34 | -0.49 | -0.49 | -0.17 | -0.36 | - | -0.16 |
S | -0.12 | -0.49 | - | -0.28 | -0.37 | -0.38 | -0.13 | -0.28 | - | -0.14 |
Gse15 | D | 0.12 | 0.3 | 0.19 | 0.18 | 0.09 | 0.22 | 0.16 | 0.17 | 0.07 | 0.21 |
S | 0.21 | 0.51 | 0.34 | 0.31 | 0.16 | 0.38 | 0.28 | 0.3 | 0.12 | 0.35 |
Gsl5 | D | 0.27 | 0.74 | 0.61 | 0.63 | 0.63 | 1.14 | 1.08 | 1.09 | 0.42 | 0.42 |
S | 0.39 | 1.13 | 0.94 | 0.95 | 1.09 | 1.74 | 1.65 | 1.66 | 0.7 | 0.62 |
Gsl10 | D | 0.34 | 0.28 | - | 0.56 | 0.46 | 0.42 | 0.35 | 0.24 | 0.22 | -0.12 |
S | 0.39 | 0.35 | - | 0.67 | 0.66 | 0.54 | 0.44 | 0.3 | 0.3 | -0.15 |
Gsl15 | D | 0.39 | 1.07 | 0.36 | 0.67 | 0.48 | 0.79 | 0.41 | 0.61 | 0.19 | 0.59 |
Gsl15 | S | 0.33 | 1 | 0.35 | 0.58 | 0.54 | 0.76 | 0.41 | 0.59 | 0.2 | 0.49 |
| | Sanandaj | Hamedan | Kermanshah | Arak | Aligudarz | Shahrekord | Khorramabad |
اLSF | D | -0.23 | 0.27 | 0.23 | -0.81 | -0.27 | 0.55 | -2.36 |
S | -0.13 | 0.16 | 0.12 | -478 | -0.16 | 0.38 | -1.52 |
FFF | D | - | 0.28 | 0.22 | - | - | -0.13 | -0.45 |
S | - | 0.48 | 0.4 | - | - | -0.23 | -0.93 |
NFD | D | -1.06 | -1 | -1.11 | -2.02 | -0.9 | 0.97 | -1.54 |
S | -0.68 | -0.71 | -0.55 | -1.17 | -0.54 | 0.7 | -0.55 |
Fp | D | -0.13 | -0.32 | -0.32 | -0.6 | -0.12 | 0.69 | -1.03 |
S | -0.12 | -0.32 | -0.28 | -0.5 | -0.11 | 0.77 | -0.76 |
AF | D | -2.15 | -1.22 | -2.16 | -2.57 | -2.61 | 3.26 | -2.21 |
S | 5.64 | 4.89 | 4.28 | 6.94 | 7.42 | -12.6 | 2.02 |
PHSD25 | D | 0.61 | 0.71 | 0.38 | 0.69 | 0.41 | 0.77 | 0.31 |
S | 0.57 | 0.56 | 0.37 | 0.6 | 0.32 | 0.62 | 0.33 |
PHSD30 | D | 1.06 | 1.56 | 0.57 | 1.23 | 1.42 | 1.43 | 0.66 |
S | 0.71 | 0.78 | 0.42 | 0.72 | 0.65 | 0.68 | 0.53 |
PHSD35 | D | 3.39 | 4.87 | 1.56 | 4.87 | 6.48 | 8.38 | 1.65 |
S | 1.14 | 0.66 | 0.69 | 0.87 | 0.39 | 0.43 | 0.86 |
PHSA25 | D | 0.87 | 0.77 | 0.47 | 0.76 | 0.43 | 0.88 | 0.49 |
S | 26.78 | 19.48 | 15.7 | 21.38 | 10.37 | 21.91 | 17.91 |
PHSA30 | D | 1.31 | 1.39 | 0.61 | 1.07 | 1.91 | 1.4 | 0.77 |
S | 30.58 | 24.36 | 16.32 | 22.24 | 19 | 22.52 | 23.15 |
PHSA35 | D | 3.58 | 3.5 | 1.33 | 3.18 | 3.65 | 7.79 | 1.49 |
S | 45.25 | 20.36 | 23.07 | 25.24 | 10.92 | 16.39 | 31.01 |
GDD5 | D | 0.89 | 0.85 | 0.71 | 0.74 | 0.6 | -0.1 | 0.85 |
S | 17.57 | 14.54 | 15.86 | 15.71 | 11.01 | -1.68 | 21.18 |
GDD10 | D | 1.27 | 1.14 | 0.85 | 0.85 | 0.73 | -0.24 | 1.15 |
S | 15.69 | 11.70 | 12.34 | 11.8 | 8.38 | -2.36 | 18.68 |
GDD15 | D | 1.77 | 1.67 | 1.2 | 1.13 | 0.99 | -0.52 | 1.65 |
S | 11.75 | 8.49 | 10.1 | 8.95 | 5.99 | -2.36 | 15.83 |
Gss5 | D | -3.14 | -1.91 | -2.95 | -2.01 | -1.78 | -0.45 | -3.99 |
S | -1.3 | -0.94 | -1.01 | -0.91 | -0.83 | -0.21 | -0.6 |
Gse5 | D | - | 0.1 | - | - | -0.10 | -0.25 | -0.06 |
S | - | 0.2 | - | - | -0.21 | -0.52 | -0.13 |
Gss10 | D | -0.85 | -0.48 | -0.7 | -1.41 | -0.49 | - | -2.42 |
S | -0.5 | -0.3 | -0.39 | -0.91 | -0.31 | - | -1.35 |
Gse10 | D | 0.07 | -0.12 | - | -0.15 | - | -0.09 | -0.36 |
S | 0.14 | -0.23 | - | -0.3 | - | -0.16 | -0.74 |
Gss15 | D | -0.58 | 0.28 | -0.21 | - | -0.35 | 0.21 | -1.38 |
S | -0.44 | -0.23 | -0.15 | - | -0.28 | 0.17 | -1.03 |
Gse15 | D | 0.09 | 0.26 | 0.06 | 0.83 | 0.17 | -0.04 | -0.18 |
S | 0.16 | 0.43 | 0.1 | 0.24 | 0.29 | -0.07 | -0.35 |
Gsl5 | D | 0.74 | 0.76 | 0.59 | 0.56 | 0.4 | -0.19 | 0.23 |
S | 1.22 | 1.14 | 1.03 | 0.90 | 0.63 | -0.3 | 0.47 |
Gsl10 | D | 0.49 | - | 0.36 | 0.46 | 0.3 | -0.11 | 0.4 |
S | 0.64 | - | 0.49 | 0.61 | 0.37 | -0.14 | 0.61 |
Gsl15 | D | 0.6 | 0.77 | 0.24 | 0.28 | 0.63 | -0.28 | 0.58 |
Gsl15 | S | 0.6 | 0.66 | 0.26 | 0.3 | 0.57 | -0.24 | 0.67 |
In relation to the changes in the beginning of the growing season at the temperature threshold of 15 degrees (GSS15) according to Mann Kendall's method, in the stations that have been determined at a significant level of 95% confidence and above (Table 4), the trend is generally negative and the age slope is between 0.3 - In Aligudarz, it is up to -1 in Khorramabad. Of course, the change trend of this index according to the ITA method is generally negative, and the slope of its changes is between − 0.8 in Qazvin and − 1.03 in Khorramabad, which is a good match with the method At the same time, the index of the end of the growing season at the temperature threshold of 15 degrees (GSE15) in the stations with significant changes according to the method of Kendal in Kermanshah station with a positive trend and age slope of 0.92 days and in Khorramabad with a negative trend And the age slope shows − 0.41 days. The mentioned index with the ITA method shows the slope of positive changes with a rate of 0.15 in Qazvin to 0.43 in Hamedan and two stations with a trend of negative changes, Shahrekord and Khorramabad, with the highest slope of changes related to Khorramabad with a rate of 35. It is 0-day. Regarding the growing season length index (GSL) at the thresholds of 5, 10, and 15 degrees, as seen in the table related to Kendall's temperature threshold, the overall trend in the stations is positive (except for a few stations where the trend is not significant). ITA method, except for Shahrekord station, in all stations, the positive trend and the slope of the changes vary from 0.39 days in Mako to 1.74 days in Maragheh. Although the rate of change in both methods is similar. The trend of temperature threshold changes of 10 degrees According to Kendall's method, this index is only significant in a few stations and the range of the age gradient varies between 0.4 days in Sanandaj and 0.65 days in the middle. In the ITA method, except for the high and mountainous stations of Saqqez and Shahr, where the trend of changes is negative, it is positive in other stations. The qualitative comparison of this temperature threshold indicates the occurrence of the most positive changes in the north of the region. At the same time, the temperature threshold of 15 degrees of this index shows a significant positive trend in only a few stations, with an age gradient between 0.4 in Urmia and 0.7 in Maragheh and Khoi, according to the Mann-Kendall method, as well as in the ITA method, except for the Shahrekord station. In other stations, a positive trend can be seen with the slope of changes between 0.2 in Qazvin and 1 day in Khoi. In connection with the number of plant thermal stress days index (PHSD) in temperature thresholds of 25, 30, 35 degrees, as seen in Tables 4 and 5 and in both Man Kendall and ITA methods, the trend is positive and indicates heating stresses. is that increasing the number of days can cause plant growth and activity to stop and cause a threat to the plant. In the meantime, according to Man Kendall's method, at a temperature threshold of 25 degrees, the age gradient is between 0.3 days in Saqqez and 1 day in Maragheh, at a threshold of 30 degrees, between 0.43 days in Kermanshah and 1.22 days in Maragheh, at a threshold of 35 degrees It was between 0.29 days in Urmia and 1.19 days in Sanandaj. An important point that can be expressed in this regard is that the highest thermal stress is not in the southern latitudes but in the middle and northern parts of the region and even in mountain stations such as Saqqez and Sanandaj. In comparing the number of changes between the above three thresholds, the largest changes in the threshold the temperature is 30 degrees. The critical point is related to the temperature threshold of 35 degrees. As in the stations of Tabriz, Miyaneh, Qazvin, Hamadan, Sanandaj, Kermanshah, Arak and Khorramabad, it can indicate climate changes, especially in mountainous areas in the future. Of course, the ITA method also shows the same positive trend and with little changes in the slope of the changes and of course with a lower coefficient. In this regard, the PHSA index is also calculated at the same temperature thresholds as the PHSD, and according to both evaluation methods, it has a positive trend in all stations. Based on this, according to Kendall's method, the value of its age slope at a temperature threshold of 25 degrees is between 11.19 degrees in Aligudarz to 36.92 degrees in Maragheh, at a threshold of 30 degrees it is between 19.27 degrees in Kermanshah and 44.19 degrees in Khoi and at the threshold of 35 degrees, it varies between 5.68 degrees in Mako and 44.99 degrees in Sanandaj. This index also shows high changes at the threshold of 30 degrees in all stations. In the ITA method, the same conditions as PHSD can be seen in this index. These two indicators are important because they have been considered as an important threat to food supply and security (Teixeira et al. 2013). Regarding the GDD index, which is an important index for the growth and development of agricultural products, as can be seen in Table 4, in 3 temperature thresholds, the trend of changes according to Kendall's method is positive and indicates an increase in the degree of growth days. As in Threshold of 5 degrees, the trend of positive changes between 11.47 degrees per day in Aligudarz to 21.86 degrees per day in Maragheh (in Khorramabad 21.24 per day), at the threshold of 10 degrees between 10.8 degrees per day in Saqqez and 19.68 degrees per day Day degree in Khorramabad (in Maragheh 18.23 degrees) and at the temperature threshold of 15 degrees between 6.04 degrees in Saqqez and 17.18 degrees in Khorramabad (14.59 in Maragheh and 15.06 degrees in Khoy Mood changes. The same conditions can be seen in the ITA method, of course, with a slight increase in the slope change rate. Surveys show that the highest trend increase is at the temperature threshold of 5 degrees. Among these, the most important focus of increasing this index is in Maragheh located in the north and Khorramabad in the south of the region.