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0.96). Some of the rivers such as Kheyrood, Kojur and Noor have a convex profile with concavity index of -4, -4, and -11, respectively. A number of other rivers such as Tajen, Babol, Sardabrood and Chalakrood with CI 8, 7.5, 9 and 8, respectively, have more concavity than other rivers.
Based on the relative concavity index (CIrel), 20% of the longitudinal profile of the North Alborz in the convex form (CIrel <0), 53% had a relatively straight or very low concavity (0
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0/005 km ^ (-1) and ( Critical inversion was investigated by the total inversion occurred and the severity of the inversions trends. The results of applying the Mann-Kendall test and the Sen’s Estimator Slope on the data of the severity of critical inversions in different months of the year showed that except for the months of October, November and December at the Mehrabad station, the rate of critical invertebrates was significant at 95 % level. For the rest of the months, the trend of severity of critical inversions has been increasing, but they are not significant at all levels of confidence. In February, the trend of inversion was decreasing in all three stations.
Conclusion
The results indicated that the radiation type inversion occurred in the period 2007-2017 at all three stations decreased significantly. Conversely, the subsidence inversion type showed a significant increase in all three stations. Radiation- Subsidence combined type had a significant increase in all three stations. It can be concluded that the types of inversion in the period of 2007-2017 have changed from pure inversion types to combine and multi-layer types and, specifically, to the Radiation- Subsidence type. The significance of the increasing trend of inversion layers was also confirmed by statistical tests. Despite the increasing trend of the inversions during the statistical period, this trend has not been significant at any confidence level. However, the intensity of inversions other than in the fall of Tehran station at other stations did not have a significant trend, although they have experienced a positive slope for many months. Several factors, including the release of high heat energy, the increase of greenhouse gases, as well as the increase in population and land use change, the change in surface evolution from heat transfer, pollutant emissions, evapotranspiration and land cover due to the impactof wind currents are considered as the reasons for this increased air stability in the boundary layer and the local climate change of these metropolises.]]>
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p. 1−28
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