عنوان مقاله [English]
One of the most interesting research areas of the scientific community in recent years is the study of the behavior and regimes of rainfall at the local, regional and global levels. At the proposal of the Intergovernmental Panel on Climate Change, rainfall changes should be comprehensively addressed in all areas (IPCC, 2007). The zoning and recognition of homogeneous climatic regions is one of the basic needs of planning. Climatic zoning is often based on the use of different climate variables in order to take into account the role of all variables in determining the climate of the regions. The main feature of rainfall in Iran is that the annual precipitation in the country is significant both in spatial and temporal terms. This spatial and temporal distribution of rainfall in Iran is affected by the distribution of global circulation systems, which has the slightest change in its pattern, causing extreme weather abnormalities. Therefore, spatial and temporal abnormalities of rainfall and severe changes in rainfall intensity and rainfall difference are the most important characteristics of rainfall in Iran (Babaei and Farajzadeh, 2002: 52). The temporal and spatial distribution of rainfall in Azerbaijan is also important due to its impact on Iranian water resources. In this study, it has been tried to analyze the cluster statistical methods to identify the zoning and zoning regime in Azerbaijan. To be Cluster analysis is a statistical method that clustering a set of individuals in terms of their similarity. Therefore, each cluster is a group whose constituents have the most similarity. There have been a lot of rainfall related to the parameters that can be mentioned.
Masoudian (2005) determined the cluster analysis method for Iran rainfall and concluded that Iran has three main regimes: first winter precipitation regime, second winter / spring precipitation regime and third winter weather regime. Mohammadi (2011) investigated Iranian precipitation trend using data from 1437 stations of synoptic, climatic and barometric stations during a 40-year period and concluded that in the time series of Iran's precipitation and pixel average, there was a significant increase or decrease in the confidence level is 95 percent (Mohammadi, 2011). In an exploratory study, Younesi (2014) explores the climate of the Republic of Azerbaijan and concludes that the maximum rainfall of Azerbaijan occurs in the northern parts (highlands of Shah dagh and Bazarzdozo), southeast (Lankaran region) and western (Khan Kandi area). Masterzard (2014) study of the terrestrial climate in Afghanistan based on the daily rainfall data of the Aphrodite database. The results of this study have shown that the average rainfall in Afghanistan is 256 mm. The area has a maximum of two parts in the eastern region with 800 mm in terms of rainfall, and another in the northeast with 450 mm. Mefakheri et al. (2017) investigated the time and uniformity of precipitation in Iran. In this research, cluster analysis method for climatic zoning and to estimate the spatial and temporal dispersion of rainfall and spatial data, the coefficient of variation and uniformity of statistics have been used in three decades, years, and seasonal periods. Van et al. (2011) conducted a research entitled Spacecraft spatial trends in the Les Cheson plateau. The results showed that based on the non-parametric Mann-Kendall test, there are no significant changes in the precipitation trend of this region. Theodoro et al. (2016) studied the temporal and spatial variations of monthly rainfall in the Brazilian Mato Grosso region using a cluster analysis. Rao et al. (2017) evaluated the precipitation trend in the central and southern regions of Peru during the statistical period from 1965 to 2010. Using cluster and component analysis, they identified four areas of rainfall and examined the trend of rainfall changes in these areas.
The country of Azerbaijan is important due to its neighbors with our country and because of its historical, cultural, ethnic and natural ties with Iran. Identifying its climate features is also one of the areas that can be of interest to Iranian researchers. This research has been done for this reason.
Materials and methods
The South Caucasus region includes the countries of Azerbaijan, Armenia and Georgia. Azerbaijan is located in the south of the Caucasus Mountains and north of the Aras River, near the Caspian Sea. In this study, the daily rainfall data of the Aphrodite database, which has a spatial resolution of 0.25 * 0.25 degrees, has been used in a statistical period of 60 years (1951-1951) to identify the rainfall regions of Azerbaijan. At first, rainfall data of 263 locations (pixels) located in the territory of Azerbaijan and adjacent regions were prepared from the base of Aphrodite, and then the average daily precipitation was calculated for these points and a 365 × 263 matrix was formed. This matrix was the basis for judging the peripheral regions and perihelion regimes of Azerbaijan. In order to identify the terrestrial and rainy regions of the country, the cluster analysis of the basin was used by integrating into MATLAB software.
Results and discussion
The average annual rainfall of Azerbaijan is 397 mm. The maximum rainfall of Azerbaijan is observed at the northern altitudes of Shah Dagh and Bazarduzu, and low-lying areas in Lankaran with values 600 mm and a minimum rainfall in the central regions of Shirvan and Baku with values 300 mm. As the north and west of the region progress to the central and southern parts, the annual precipitation is also reduced. In Nakhchivan, the maximum rainfall of about 450 mm corresponds to the mountainous areas of the northeast and as far as the south and west of the Nakhchivan area advance, annual rainfall decreases.
Precipitation is a climate whose amount changes continuously. By analyzing the cluster on the average annual rainfall in Azerbaijan, this country is divided into six districts. These areas are different in terms of precipitation and annual distribution. In general, the country of Azerbaijan is divided into two high rainfall (the Lankaran and high Caucasian) and low rainfall (coastal area and Baku). However, each of the high and low rainfall regions was divided into smaller areas and finally six areas were identified in Azerbaijan.
In order to identify the regime of the country of Azerbaijan, a matrix with a size of 363 × 363 was formed, which represented 263 places per day in terms of percentage per day. On this basis, the first Euclidean distance of all spatial precipitation is measured every day. After measuring the Euclidean distance, a cluster analysis was performed by integration method on the interval matrix and 263 points were clustered in accordance with the degree of similarity. In general, the diet regime in Azerbaijan is divided into two types of rainy regimes: spring rainfall regime, which includes three sub-diet regimes (Nakhchivan regime, Northwest regime and central regime), and the most annual rainfall occurs during the spring and the autumn regime - Spring with two regimes (Lankaran regime and East Azarbaijan and Baku regime), in which the share of precipitation falls from the first year of precipitation and the spring precipitation is in the second place.
The seasonal distribution of precipitation in Azerbaijan is as follows: in the west of the country and Nakhchivan, the regions receive the highest percentages of their annual precipitation in the spring, in which more than 38 percent of the annual precipitation falls this season. The regions in the eastern part of Azerbaijan, such as the cities of Baku and Lankaran, receive their most annual precipitation in the fall so that more than 35 percent of the annual rainfall in this season falls. Due to extreme cold weather in the winter season in the region of Azerbaijan and the Caucasus does not drop much, so that an average of 20 percent of the annual precipitation in the region occurs this season. The highest percentage of the country's winter rainfall is located in the east and the inshore peninsula, which is also located in Baku.
In this research, we have tried to investigate the cluster analysis of the regions and rainfall regimes in Azerbaijan. In order to study the regions and slopes of the Republic of Azerbaijan, the daily precipitation data of the Aphrodite database, which has a spatial resolution of 0.25 * 0.25 degrees, has been used for a period of 60 years (1951-2010). In order to identify the terrestrial and rainy regions of the country, the cluster analysis of the basin was used by integrating into MATLAB software. The average precipitation of Azerbaijan is about 397 mm. It is divided into two high and low rainfall regions. The high area is seen in two parts, one in the Lankaran area and one in the mountainous regions of the Caucasus and the small Caucasus in the northeastern and southwest of the country. The average annual rainfall in the low rainfall region (central areas) is about 290 mm, and the average rainfall in high-rise areas (Lankaran and Caucasus heights) is about 565 mm. The low rainfall area also includes central regions and Nakhchivan. In Azerbaijan, the country is divided into two types of rainy regimes: spring rainfall regime, which includes three sub-diet regimes (Nakhchivan regime, Northwest and central regime), and the most annual rainfall in these areas occurs in the spring and autumn diet with two sub-diet regimes (Lankaran regime and East Azarbaijan and Baku regimes), in which the share of precipitation falls from the first year of precipitation and the second in spring.