Dr. Seyed Abolfazl Masoodian,
Volume 0, Issue 0 (3-2007)
Abstract
Variability is inherent in the nature of climate. Temperature variability may be considered as the most evident indicator of climate change. Temperature variation may be randomly, cyclical, trending, or abrupt. Depending on the type of temperature variability, it can lead to diverse environmental, economic, social, and security consequences.
The trend of temperature on a global scale and temperature trend in Iran have been the subject of extensive research. Many researchers have confirmed the increasing temperature trend globally, and global warming has gained nearly universal acceptance. Similarly, the increasing temperature trend in Iran has been reported in numerous studies. However, comparing these results is not straightforward due to differences in the data and methodologies used to analyze temperature trends in Iran. Additionally, since many of these studies have been station-based—meaning they rely on station data—compiling them does not provide a comprehensive image of temperature trends at a national level. Moreover, the findings of these studies sometimes contradict each other.
If we set aside these challenges, while temperature trends have been extensively studied, abrupt shifts (jump changes) in Iran's temperature data have been less frequently examined. In this research, using station data, gridded Asfezari data, IMDAA gridded data, and ERA5 gridded data, we demonstrate that Iran's minimum and maximum temperatures have experienced jumps rather than gradual trends. Notably, the maximum temperature underwent a significant jump in the year 1998. All data sources used in this study confirm that the timing of the jump in minimum and maximum temperatures aligns approximately.
Fakhri Sadat Fateminia, Behrouz Sobhani, Seyed Abolfazl Masoodian,
Volume 18, Issue 48 (3-2018)
Abstract
This study was performed to evaluate the extent of leaf area in Iran from (2002) to (2016) using Remote sensing. For this purpose, we extracted data collection and leaf area index for the Iranian territory from MODIS website. The database was established with programming in MATLAB software to perform mathematical and Statistical calculations repeated. After the analysis of the data in this software a monthly average long-term map was developed. The maps show that the central, East and South-East are almost empty of leaf area or seen very sparse in some areas. In contrast areas of leaves in the northern and western parts of Iran, are good, which generally includes fields, except forest Arasbaran and Hirkany. Precipitation and the temperature, is the main factors for the growth and development of plants, that these two conditions are enumerated in the west due to being on the way of westerly winds. Lowest leaf area index is for January and February and the highest average of leaf area is for May and June. Next, study of 15 years of leaf area index data by cluster analysis based on the calculation of Euclidean distance and Ward method, showed that all 12 months fit in the two main groups and, in fact, divided for two periods of strong and weak vegetation. In this analysis, , April during the cold period and October in the warm period of the year as the transition months and they are located on a separate cluster
