Over the past five decades, the world has experienced, on average, one weather-, hydrological-, or climate-related disaster per day. During this period, an average of 115 fatalities per day and economic losses exceeding USD 202 million per day have been reported. More than 91% of disaster-related deaths have occurred in developing countries (CRED, 2018).

This study examines and analyzes atmospheric hazards in Tehran Province, including dust storms, hail, heavy snow, thunderstorms, fog, and severe snow blizzards, based on data from seven synoptic stations (Mehrabad, Shemiranat, Varamin, Firuzkuh, Shahriar, Imam Khomeini, and Abali) during the period 2007-2023.

The primary objective of this study is to conduct a preliminary screening of atmospheric hazards and identify the dominant types of atmospheric hazards in Tehran Province, with a particular emphasis on the "hazard" component of the risk framework. This assessment is based on weather codes recorded at meteorological stations and aims to determine the temporal and spatial distribution of hazard occurrence frequencies across the province.



The results of this study have significant applications in regional planning and early warning system management. By producing spatial distribution maps of atmospheric hazards, a more comprehensive understanding of the nature and distribution of these phenomena in Tehran Province can be achieved. Furthermore, the findings contribute to the development of a more accurate characterization of the conditions under which such hazards occur and their associated impacts.

1-Material and Methods

Study Area

Tehran Province, which spans an area of approximately 18,814 km², is located between 34° and 36.5° north latitude and 50° and 53° east longitude. This province is bordered to the north by Mazandaran Province, to the south by Qom Province, to the southwest by Markazi Province, to the west by Alborz Province, and to the east by Semnan Province. The capital of this province is the city of Tehran, and other significant cities include Islamshahr, Damavand, Shahr-e Rey, Kahrizak, and Varamin. Although Tehran Province covers only 0.78% of Iran's total area, it accommodates 16% of the country's population. It is the most populous province in Iran, with a population of 14,033,400 according to 2021 statistical data, of which 13,261,600 reside in urban areas and 771,800 in rural areas. Based on the 2018 United Nations estimate, Tehran ranks as the thirty-fourth most populous city in the world and the most populous city in Western Asia. The metropolis of Tehran is also the second most populous city in the Middle East. In terms of natural topography, Tehran is divided into two regions: the plain and the foothills of the Alborz Mountains, with altitudes ranging from 900 to 1,800 meters above sea level . The northern part of this province has a mountainous climate, while the southern part has a desert climate.

In this study, observational data obtained from synoptic meteorological stations operated by the national meteorological organization were used. To ensure data consistency and adequate spatial coverage, stations with relatively continuous records during the 2007–2023 study period were selected. Ultimately, seven principal synoptic stations, including Mehrabad, Shemiranat, Varamin, Firuzkuh, Shahriar, Imam Khomeini International Airport, and Abali, were chosen as reference stations for analyzing the spatial distribution of atmospheric hazards across the study counties.

Atmospheric hazards were identified and classified according to the present and past weather codes recommended by the World Meteorological Organization (WMO) in WMO Manual No. 306. Based on these codes, six major atmospheric hazard categories were examined in this study:



Dust storms (codes 30–35)

Hail events (codes 27, 87–90, and 93–99)

Heavy snowfall (codes 73–75)

Thunderstorms (codes 92–99)

Fog (codes 40–49)

Severe snowstorms/blizzards (codes 37 and 39)

To avoid overestimation of event frequency, each hazard was defined on a hazard-day basis. Accordingly, regardless of the number of observations or reports recorded within a given day, that day was counted as a single hazardous event occurrence.

Results

The spatial distribution analysis of hazards revealed high frequencies in the northern and northeastern mountainous regions of the province (such as Abali and Firuzkuh), where thunderstorms (with a maximum of 141 cases in Damavand) and heavy snow (202 cases in Damavand) are predominant. In contrast, southern and plain areas (such as Imam Khomeini and Varamin) are more affected by dust storms (7 cases in Imam Khomeini) and fog. Hazard prioritization was conducted based on normalized frequencies, indicating that thunderstorms are the top priority in northern counties (Shemiranat, Tehran, and Firuzkuh), while dust storms are the primary concern in southern regions (Rey, Shahriar, and Varamin). This research demonstrates the impact of topography and geographical location on the spatial distribution of atmospheric hazards in Tehran Province. Therefore, it is recommended that risk management planning be carried out based on these patterns.