Development and application of a new index for analyzing temperature concentration for Iran’s climate

Spatiotemporal variation of temperature and precipitation helps in classification of type of climate of each region and affects the availability of access of drinking water to the inhabitants in the region. A new index that is called as the temperature concentration index (TCI) was developed in the present study to investigate the concentration of temperature in Iran based on the two known inspiring patterns of Gibbs–Martin (Am Sociol Rev 27:667–677, 1962) and Oliver (Prof Geogr 32:300–309, 1980). The developed index was classified based on three methods, including the Oliver’ classification (1980), the coefficient of variation of temperature data, and coefficient of variation of TCI values. The results show that all the three classification methods represent almost similar classes for the TCI. After the classification of the proposed TCI, two indices of the precipitation concentration index (PCI) and the TCI were applied to the long-term analysis of precipitation and temperature of thirty-four synoptic stations of Iran during the 50-year period (1961–2010). Based on the TCI, highly irregular distributions in temperature were observed during the winter season in the northwest of Iran. In the annual timescale, the calculated TCI values indicated the uniform temperature pattern in the borders of the Persian Gulf, the Gulf of Oman, and the coast of the Caspian Sea. The comparison between the two indices, the PCI and the TCI, reveal that these two indices are inversely related to each other; i.e., reduction in one index will be along with an increase in another index. The irregular distribution of temperature implies higher changes in temperature, and so the conditions for higher precipitation will be provided. The PCI index represents a uniform distribution of the precipitation over the selected stations of Iran.