The winds that cause the monsoon winds to blow over India are called the "Northeast Monsoon." They take a northward path and reach India around September. The winds carry regular amounts of dust particles from the Middle East deserts. A new study suggests that these airborne particles help too - directly and indirectly - modulate the Indian monsoon rainfall and its landfall pattern.
Dust is a particulate matter smaller than 10 micrometers. There are 2 sizes of a dust particle, PM10, and PM2.5. Particles between 2.5 to 10 micrometers in diameter are called fine particles or PM2.5 and they have many sources which can include, decaying plants and animals, earth and stone weathering, sea spray, vehicle exhausts and also from human activities such as wood burning and processing of automobiles. Another main source of PM2.5 is the smoke from fires for cooking in open fires and other domestic uses where smoke may be emitted directly into the atmosphere without being collected.
The natural erosion of soil, sand and rock is the most common source of dust. Dust emission is common in urban areas from a range of activities such as gardening, to large scale industrial operations. It is known to influence monsoons, hurricanes and even fertilize rainforests.
The dust emission scheme is extremely sensitive to climate change and understanding these mechanisms and effects of dust can help understand our monsoon systems in the face of global climate change.
Heating of the atmosphere: Dust storms from the desert when lifted by strong winds can absorb solar radiation and become hot. This can cause heating of the atmosphere, change the air pressure, wind circulation patterns, influence moisture transport, and increase precipitation and rainfall.
Effect on Indian Monsoon: The Indian monsoon rainfall and clouds over India are greatly influenced by the emission of dust particles from the deserts. The hot air over the Iranian Plateau can heat the atmosphere over the plateau, strengthen the circulation over the deserts of the Arabian Peninsula and increase dust emission from the Middle East.
The reverse effect of monsoon winds: Monsoon is called as reverse winds. It reverses the direction of the wind from South to South-west during its onset phase. The strength and speed of these winds have a great influence on the climate and weather in West Asia.
Effect of Anthropogenic Dust: Dust can affect climate through changes in radiation budget, tropospheric chemistry, and by affecting cloud droplet number concentration. As a result of dust absorption, scattered radiation is trapped, warming the surface and lower troposphere. There is also evidence that dust scattering can contribute to a weakening of the monsoon circulation, probably due to a reduction in cloud droplet number concentration.
