Hi.

There's a low pressure areas when atmospheric circulations of air up and down remove a small amount of atmosphere from a region: along the boundary between warm and cold air masses by air flows and reduce that temperature contrast. The the colder air flowing under the warmer air mass, and the warmer air flowing over the colder air mass.To india: the Monsoon cycle is emblematic.

In the spring period to the month of May, the continent has warmed more than the sea, and therefore has become a low-pressure zone: the air masses rise and their emptiness is covered by fresh winds and damp coming from the sea, and therefore they arrive huge amounts of rain, which lasts for months (3-4). So contrary six months later, during the winter, the huge Asian landmass cools, while the Indian Ocean and the South Pacific Ocean are kept warm. On the continent it will form a huge area of high pressure (H) on a sea area of low pression (L): the air masses moving from land to the sea, and then in winter and quite cold dry

winds blow from the inside Asia on the ocean.

For Koppen (1932) the area of India is a, Tropical Monsone Climate (Am). This climate is part of the types of the climate of the planet.

Bye, Giorgio Russo (Italy).

Nilendu,

I have been reliably informed that convection is most often the result of chemical rather than physical change. In the case of the atmosphere the chemical change which causes convection is an increase in the water vapour content.

Hot air will not convect. Only hotter air convects. There has to be a source of cold air to replace the hot air for it to rise.

In the centre of the Thar Desert, where there is no water, there will be little convection except when dust devils occur. The heat low is formed because the air adjacent to the surface is heated by the absorption of radiation from the ground, which in turn has been heated by solar radiation. The air expands upwards and the column of air becomes taller. The top of the column spills off, and the column becomes lighter reducing the surface pressure and forming a heat low.

Whether this low pressure area draws in air from the colder sea surface and then convects, or whether the monsoon is caused by sublimation of the Himalayan ice sheets raising the water vapour content there and causing convection, I leave to you to determine.

HTH,

Cheers, Alastair.

Hi

There has been study by T. N. Krishnamuri ( Monthly Weather Review September 1983) on the dynamics of heat low. He studied the dynamics of heat low over Saudi Arabia using MONEX dropsonde and radiation measurements. Heat low is maintained by subsidence from the higher levels. Thar desert dynamics is similar to that. More details can be seen from the paper. 

J. R. Kulkarni

The heat low in the desert for the monsoon is balanced off by the atmospheric Dust Cloud that forms each year and is expanding eastward until last year it covered most of India causing drought.  

The low draws the monsoon westward and unfortunately what I call the "Arabia-Pakistan Dust Cloud" cancels the monsoon.  The Dust Cloud is so strong, that it can cancel any degree of low pressure, including Category-5 cyclones, which it can eat or divert from making landfall.  There are a lot of questions I have posted on Research Gate at https://www.researchgate.net/search.Search.html?type=question&query=Dust+Cloud.  

Also see where the Dust Cloud ate the cyclone GONU at http://www.ecoseeds.com/GONU.html and http://www.ecoseeds.com/newGONU.html

We need to add the daily Dust Cloud locations to our weather and climate models, and when that is done, a much clearer picture of the summer monsoon droughts and flooding is seen, when the daily interaction between the moisture and the Dust Cloud location is monitored. 

The second interaction to the monsoon that is occurring, is the chopping down of the Pseudomonas host trees in SE Asia, that create the monsoon rains in the first place, so storms may come in the future, but without the Pseudomonas bacteria to "seed" the clouds, we may get a lot of clouds following low pressure systems, with very little rainfall being produced.  

I have a lot of questions on Research Gate about that issue also, with images of the Pseudomonas clouds during the monsoon season at https://www.researchgate.net/search.Search.html?query=Pseudomonas%20rain&type=question.