| <!-- @page { margin: 2cm } P { margin-bottom: | | | | regular interval of time, this data was used for |
| 0.21cm } H1 { margin-bottom: 0.21cm } | | | | weather forecasting, 1 to 3 days in advance by |
| H1.western { font-family: "Liberation Serif", serif } | | | | empirical methods as well as dynamical methods. |
| H1.cjk { font-family: "DejaVu Sans" } H1.ctl { | | | | Dynamical methods were introduced in 1960 |
| font-family: "DejaVu Sans" } H2 { margin-bottom: | | | | onwards in the advanced countries and 1980 |
| 0.21cm } --> | | | | onwards in India. |
| | | | | The system of forecast 1 to 3 days in advance |
| | | | | based on initial observed conditions is known as |
| History of monsoon | | | | short range prediction and if the dynamical models |
| The initiation of the Southwest monsoon as the | | | | are used they are called numerical weather |
| prime weather system is often connected to the | | | | prediction for short range. From 1980 onward, |
| uplift of the Tibetan Plateau and the Himalayas | | | | medium range forecasting i.e. 3 to 10 days in |
| after the collision of the Indian sub-continent and | | | | advance using global models was introduced in |
| Eurasia around 50 million years ago. Geologists | | | | Europe and USA and in India from 1992 onwards. |
| believe the monsoon first became strong around | | | | For this, global models are used based on initially |
| 8 million years ago based on records from the | | | | observed conditions. The forecast could differ in |
| Arabian Sea and wind-blown dust in the Loess | | | | detail from model to model because of the initial |
| Plateau of China. | | | | conditions (data receipt, the model |
| What is monsoon? | | | | resolution-horizontal vertical) and the physical |
| The Southwest monsoon is largely a four-month | | | | parameterization for the sub-grid scales. India |
| period when massive convective thunderstorms | | | | today uses, high resolution mesoscale models for |
| dominate India's weather. The weather system is | | | | sub-regional prediction, high resolution global |
| essentially caused by heating up of Northwest | | | | models for short to medium range predictions. |
| India, creating a low pressure over the region. | | | | Since models may differ in detailed forecast on |
| This hot low pressure belt works as bait for | | | | rainfall, India also uses ensemble prediction system |
| cooler winds blowing in from the Indian Ocean. | | | | for getting a better forecast by judiciously |
| The moisture laden winds from the great water | | | | combining the forecast of different models. |
| body cause rain and thundershowers across the | | | | There is another scale of forecasting called long |
| Indian sub-continent. | | | | range forecast on monthly to seasonal scale. Such |
| The monsoon breezes in over the sub-continent | | | | forecast began in India in 1884 for the monsoon |
| via the Bay of Bengal and the Arabian Sea | | | | season and was made more quantitative by |
| branches. The monsoon first arrives at the | | | | applying statistical models from 1904 to 1920 by |
| Andaman and Nicobar Islands by around 25th May. | | | | Sir Gilbert Walker by using surface meteorological |
| The Indian mainland is hit by monsoon around 1st | | | | data alone from all over the world that had |
| June at coastal Kerala. The Southwest monsoon's | | | | significant statistical correlation with the seasonal |
| typical date for reaching Mumbai is 10th of June. | | | | rainfall of India. The methods gave mixed results |
| Meteorology dawns in India | | | | and were continuously improved between 1930 |
| The observations about the surface climate of | | | | and 1980 by introduction of upper air data and |
| India were started in the beginning of the 19th | | | | introducing parameters that are found to be |
| Century by the individual attempts of an officer | | | | significantly related and rejecting those |
| of the East India Company. Between 1850 and | | | | parameters which lost correlation with the |
| 1860 efforts were being made to establish the | | | | monsoon rainfall. After the drought of 1987, a |
| provincial meteorological system in the | | | | concerted effort was made to introduce a 16 |
| Presidencies of Bengal, Punjab, Northwest India | | | | parameter model using non linear statistical |
| and Uttar Pradesh, Central India and Mumbai. But | | | | regression equations. As no screening of the |
| the need was felt to establish the meteorological | | | | parameters was made, this model showed mixed |
| system in a uniform fashion under a central | | | | results during the period 1988 to 2002 and failed |
| authority. | | | | to predict the excess rain in the year of 1994 |
| The India Meteorological Department was | | | | and the major drought of 2002. |
| established in January 1875 as result of these | | | | The model was revised in 2003 with only 8 |
| efforts. Most of the weather services in the | | | | parameters. This model also failed to predict the |
| world like USA, UK, France and Germany were | | | | drought of 2004. In fact, right from the inception |
| established in the period 1865 to 1875. India was | | | | of long range forecasting from 1884 to 2009, no |
| part of the same effort and it became a member | | | | drought or excess year has been predicted |
| of the International meteorological system from | | | | successfully by any statistical model introduced at |
| inception. Between 1875 and 1900, the major | | | | different times. In 2006, another modification was |
| effort was to establish a uniform system of | | | | made and that to did not succeed in predicting the |
| instrumentation, time of observations, procedures | | | | drought of 2009. |
| of scrutiny and storage of this data for | | | | Monsoon facts |
| climatological uses. Daily weather reports as | | | | The Arabian Sea branch of Southwest monsoon |
| collected in Shimla, the then headquarters of the | | | | is 3 times stronger than the Bay of Bengal |
| India Meteorological Department were being | | | | branch. |
| published based on telegraphics messages from | | | | Northeast India receives the most precipitation |
| 1880's onwards. The daily weather charts were | | | | during the reign of the Southwest monsoon. |
| also being prepared from about the same period. | | | | 80% of all rain received by the country is during |
| So in a way, the weather forecasting and | | | | the four months of monsoon i.e. June to |
| documentation of information began from 1880's | | | | September. |
| onwards, i.e. 130 years before the present date. | | | | The Indian Southwest monsoon is planet Earth's |
| During the Second World War, the radio sonde | | | | most productive wet season. |
| system was introduced by which the information | | | | The United States of America also receives rain |
| about temperature, pressure, humidity and winds | | | | and thundershowers from its very own |
| is telemetered to a ground station in real time and | | | | Southwest monsoon also known as the Arizona |
| the data are used for weather analysis in three | | | | monsoon. The moisture influx in this case is from |
| dimensions that is East, North and vertical. At a | | | | the Gulf of Mexico. |