History of monsoon
The initiation of the Southwest monsoon as the prime weather system is often connected to the uplift of the Tibetan Plateau and the Himalayas after the collision of the Indian sub-continent and Eurasia around 50 million years ago. Geologists believe the monsoon first became strong around 8 million years ago based on records from the Arabian Sea and wind-blown dust in the Loess Plateau of China.
What is monsoon?
The Southwest monsoon is largely a four-month period when massive convective thunderstorms dominate India’s weather. The hot low pressure belt works as bait for cooler winds blowing in from the Indian Ocean. The moisture laden winds from the great water body cause rain and thundershowers across the Indian sub-continent.
The monsoon breezes in over the sub-continent via the Bay of Bengal and the Arabian Sea branches. The monsoon first arrives at the Andaman and Nicobar Islands by around 25th May. The Indian mainland is hit by monsoon around 1st June at coastal Kerala. The Southwest monsoon’s typical date for reaching Mumbai is 10th of June.
Meteorology dawns in India
The observations about the surface climate of India were started in the beginning of the 19th Century by the individual attempts of an officer of the East India Company. Between 1850 and 1860 efforts were being made to establish the provincial meteorological system in the Presidencies of Bengal, Punjab, Northwest India and Uttar Pradesh, Central India and Mumbai. But the need was felt to establish the meteorological system in a uniform fashion under a central authority.
The India Meteorological Department was established in January 1875 as result of these efforts. Most of the weather services in the world like USA, UK, France and Germany were established in the period 1865 to 1875. India was part of the same effort and it became a member of the International meteorological system from inception. Between 1875 and 1900, the major effort was to establish a uniform system of instrumentation, time of observations, procedures of scrutiny and storage of this data for climatological uses. Daily weather reports as collected in Shimla, the then headquarters of the India Meteorological Department were being published based on telegraphics messages from 1880’s onwards. The daily weather charts were also being prepared from about the same period. So in a way, the weather forecasting and documentation of information began from 1880’s onwards, i.e. 130 years before the present date.
During the Second World War, the radio sonde system was introduced by which the information about temperature, pressure, humidity and winds is telemetered to a ground station in real time and the data are used for weather analysis in three dimensions that is East, North and vertical. At a regular interval of time, this data was used for weather forecasting, 1 to 3 days in advance by empirical methods as well as dynamical methods. Dynamical methods were introduced in 1960 onwards in the advanced countries and 1980 onwards in India.
The system of forecast 1 to 3 days in advance based on initial observed conditions is known as short range prediction and if the dynamical models are used they are called numerical weather prediction for short range. From 1980 onward, medium range forecasting i.e. 3 to 10 days in advance using global models was introduced in Europe and USA and in India from 1992 onwards. For this, global models are used based on initially observed conditions. The forecast could differ in detail from model to model because of the initial conditions (data receipt, the model resolution-horizontal vertical) and the physical parameterization for the sub-grid scales. India today uses, high resolution mesoscale models for sub-regional prediction, high resolution global models for short to medium range predictions. Since models may differ in detailed forecast on rainfall, India also uses ensemble prediction system for getting a better forecast by judiciously combining the forecast of different models.
There is another scale of forecasting called long range forecast on monthly to seasonal scale. Such forecast began in India in 1884 for the monsoon season and was made more quantitative by applying statistical models from 1904 to 1920 by Sir Gilbert Walker by using surface meteorological data alone from all over the world that had significant statistical correlation with the seasonal rainfall of India. The methods gave mixed results and were continuously improved between 1930 and 1980 by introduction of upper air data and introducing parameters that are found to be significantly related and rejecting those parameters which lost correlation with the monsoon rainfall. After the drought of 1987, a concerted effort was made to introduce a 16 parameter model using non linear statistical regression equations. As no screening of the parameters was made, this model showed mixed results during the period 1988 to 2002 and failed to predict the excess rain in the year of 1994 and the major drought of 2002.
The model was revised in 2003 with only 8 parameters. This model also failed to predict the drought of 2004. In fact, right from the inception of long range forecasting from 1884 to 2009, no drought or excess year has been predicted successfully by any statistical model introduced at different times. In 2006, another modification was made and that to did not succeed in predicting the drought of 2009.
The Arabian Sea branch of Southwest monsoon is 3 times stronger than the Bay of Bengal branch.
Northeast India receives the most precipitation during the reign of the Southwest monsoon.
80% of all rain received by the country is during the four months of monsoon i.e. June to September.
The Indian Southwest monsoon is planet Earth’s most productive wet season.
The United States of America also receives rain and thundershowers from its very own Southwest monsoon also known as the Arizona monsoon. The moisture influx in this case is from the Gulf of Mexico.
Take the mystery out of common weather phenomena with BarCharts’ updated and expanded Meteorology QuickStudy® guide. Now in thr…
Written for the undergraduate, introductory course, the updated Fourth Edition engages students with real-world examples and a cap…
What does it mean when there is a corona around the moon? How do you tell the difference between stratocumulus and nimbostratus cl…
In many parts of the world, the weather forms a daily topic of conversation. In other parts, the weather hardly changes from one w…
This updated and enhanced Fifth Edition of ESSENTIALS OF METEOROLOGY is written by the widely read and authoritative author in int…
Interest in our nation’s weather patterns is rising — as witnessed in the popularity of the Weather Channel — and this guide is …