Makran-Rain

Monsoon and Its Role in Runoff Generation

The monsoon occurs predominantly in the Indian subcontinent, where land and water bodies are juxtaposed. During summer, as the Earth's rotation reduces the solar angle and makes it nearly vertical, the landmass absorbs significant solar energy. Since the land surface is composed of soil and rock, it absorbs heat and raises its temperature, while water bodies do not, leading to evaporation. This creates a temperature differential between land and water in the Indian subcontinent. The high temperature on land causes a decrease in pressure, facilitating the upward movement of air. This necessitates the replacement of this air with another air mass, which originates from the ocean and water surface, carrying moisture along with it. This moisture transforms into clouds over land, a process known as the release of latent heat. This phenomenon generates explosive clouds over land, also referred to as thunderstorms. This process constitutes the formation of the monsoon.

While the monsoon is most commonly associated with India, it also occurs in other regions, including China. However, the most significant monsoon region encompasses the Indian subcontinent, Pakistan, and to a lesser extent, southeastern Iran. The monsoon in Iran is considerably weaker than in India. Oceanic currents originating from the eastern coast of Somalia, the southernmost part of the Indian Ocean, and extending to the easternmost reaches of the Indian Ocean, play a crucial role in shaping the monsoon phenomenon. These currents transport moisture-laden air towards the Indian subcontinent, leading to the formation of monsoonal rainfall.

Monsoon air mass

In some years, during the warm season, the monsoon from the Indian Ocean penetrates Iran and causes torrential rains in the southeastern parts of the country.

The strength of the monsoon in Iran depends on the amount of moisture that can penetrate from the Indian subcontinent and Pakistan towards Iran. Stronger moisture penetration leads to heavier rainfall in southeastern Iran, as observed in July 2023.

When does the monsoon reach Iran of bluchestan?

Weak northern currents and strong southern currents allow moisture to be transported from the northern Indian Ocean and the Persian Gulf to the Iranian plateau, resulting in afternoon thunderstorms in southern Iran. Rainfall typically occurs between 3 pm and 4 pm, lasts for 20-30 minutes, and is not usually torrential. These afternoon showers generate runoff in mountainous areas.

Climate characteristics

The climate of Southern Balochistan is characterized by long, hot summers and mild winters. Precipitation occurs in two distinct seasons: winter and summer. Due to the hot desert climate, rainfall patterns follow those of dry regions. Most rainfall events are of short duration, relatively high intensity, and limited spatial extent. The majority of annual rainfall occurs during the winter season. Spring and summer rainfall is accompanied by thunderstorms and comprises multiple convective cells.

This rain system moves from the eastern end of the Mediterranean Sea and moving towards east, it enters Iran from the western border and it affects the areas located in the northwest, west, southwest, and the provinces located in the southern slopes of Alborz.