Beyond Kerala, the monsoon gets divided into two parts: the Arabian Sea branch and the Bay of Bengal branch. By the first week of July, monsoon winds reach almost all over India. What are the ways to forecast monsoons? There are three main methods used for forecast of the southwest monsoon here. The first is the statistical method, which uses the historical relationships between the monsoon and various global weather parameters. The data is then used to forecast the onset and the intensity of the monsoon.
The second is the empirical method, which uses time series analysis of past rainfall data to predict monsoon. The third is the dynamical method, which uses general circulation models of the atmosphere and oceans to predict the southwest monsoons. Prediction models based on the statistical approach have so far yielded the most accurate results for the Indian monsoon. Given the plethora of factors involved, its necessary to keep developing new models and refining existing ones. Which method is used by our Met department?
Prior to , the IMD used to issue annual forecasts using a model based on 16 parameters. Jacob Bjerknes, a Norwegian meteorologist, would later recognize that the circulation of winds, rain, and weather was part of a Pacific-wide air circulation pattern he called Walker circulation. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile.
Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Rachelle Oblack. Video: UCAR. The summer monsoon is what people often think of as monsoon conditions: large amounts of rain. But the winter monsoon, where dry conditions prevail, is part of the pattern too. During winter, air descends over tropical continents as the part of the Hadley Circulation that is outside of the ITCZ.
Descending air causes high pressure, and makes clouds and rain uncommon. The dry conditions during winter can even lead to drought if they are too intense or persist for too long. Geography affects the amount of rainfall that an area receives as the ITCZ moves through the seasons. Low-level winds blow south towards the ITCZ, picking up moisture as they move over the warm, tropical ocean. Meanwhile in India, dry air descending over land means there is little precipitation.
During Northern Hemisphere summer, the ITCZ is north of the equator and monsoon rains fall in India and other parts of south Asia as winds blow north from the tropical ocean to the land, while northern Australia experiences very dry conditions as air descends.
When intense summer sunlight hits land, its energy is absorbed and transferred quickly back into the atmosphere. This means that, in summer, air over land is heated more than air over ocean, which shifts the ITCZ toward land regions. In regions where continents lie north or south of the equator, as in Asia and Australia, this causes the ITCZ to shift farther off the equator during the summer season.
There is year-to-year variation in the amount of monsoon rainfall during summer. While this is a general pattern, it cannot be used to indicate exactly how much rain will fall in India in any particular summer. So there must be other influences on the amount of rainfall, too. This is an area of active research. Rains will likely increase in wet regions as climate warms because warm air can hold more water; if the winds do not change, more water vapor in the atmosphere will produce more rain in the ITCZ.
Over ocean, where there is abundant water supply for the atmosphere, this is quite likely, but it is less clear how the amount of rain may change over land as climate warms. Whether or not winds will change enough to have a large effect on the rainfall is also unclear.
During the dry season, land is expected to become drier because evaporation from land will increase in a warmer climate. At the same time that rainfall is changing due to global climate change, natural year-to-year variability is happening as well. Other changes to the amount of rainfall may be caused by air pollution such as tiny particles released as coal, oil, and gas are burned. The amount of monsoon rain that falls each year is highly variable, according to records of rain in India collected since the s.
In parts of India monsoon rainfall has decreased some since Meanwhile, in the Philippines and other areas of the western North Pacific, the amount of monsoon rain has increased. Weak monsoon rains produced drought and famine over large parts of Africa in the s and s, but the West African monsoon rains have recovered somewhat since then. So there is evidence that monsoons are changing, but researchers are still investigating how the amount of monsoon rainfall will be affected by climate change in the future.
Farmers in monsoon regions rely on the wet summer months to grow crops. However the summer monsoon does not always bring the same amount of rainfall, and variations in rain have implications for agriculture and the economy.
For example, in very little rain fell during the summer monsoon in India. In some areas rainfall was half of what is typical during the wet season and farmers could not plant their crops. Farm animals starved; many were sold for a fraction of what they would have normally been worth because farmers were desperate.
From wheat and rice to vegetables, cotton, and tea, Indian farmers grow a wide range of crops and the country uses more land for crops than any other country in the world million acres. Crops depend on rain and, in India, more than three quarters of the annual rainfall occurs during the four months of the summer monsoon season. Secondary schools are located on the mainland and can take up to 1.
But during the rainy season, students need to cross the river by boat to get to school. Despite each of these hurdles, you can help make a lasting difference and change the future of Hatibandha. With your help, Plan will help address some of the challenges that the people of Hatibandha face every year because of their geography.
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