Analysis of Appreciably above normal maximum temperatures across west and southern parts of India during 13-19 February, 2020

  1.  Introduction

 In this report an attempt is made to analyze the above normal temperatures across west and southern parts of India during 13-19 February, 2020. Middle February is a transition period from winter to summer in southern parts of India. During this period temperatures rises gradually over southern parts of the country. This pattern varies from year to year. This year appreciably above normal maximum temperatures reported over west and southern parts of the country during 13-19 February. Media also reported the same. On 17th February, Santacruz (Mumbai) reported highest maximum temperature in the country that was 38.1°C. 

2.  Observed temperature over West and southern parts of India 13-19 February

Refer table 1 and 2

Table 1:    Report on above normal temperatures over South and West India During 13 to 19 February 2020.

          DateMaximum Temperature Departures (Places)Highest Maximum Temperature in °C
Markedly above normal (5.1°C or more)Appreciably above normal (3.1°C to 5.0°C)Above normal (1.6°C to 3.0°C)
13-02-2020   Many places- Konkan & Goa. Few places- Saurashtra & Kutch.  Most places- Coastal Karnataka. Many places- Gujarat Region, Vidarbha, Kerala & Mahe, Lakshadweep. Isolated places- North Interior Karnataka and Tamilnadu, Puducherry & Karikal.38.4Gulbarga (North Interior Karnataka).  
14-02-2020 Most places- Konkan & Goa. Few places- Saurashtra & Kutch and Coastal Andhra Pradesh & Yanam.Most places- Lakshadweep. Many places- Vidarbha, Odisha, Coastal Karnataka and Tamil Nadu, Puducherry & Karaikal. Few places- Gujarat Region Isolated places- Telangana, South Interior Karnataka.37.7-Vengurla (Konkan & Goa).  
15-02-2020 Isolated places-  Saurashtra & KutchMost places- Coastal Karnataka. Many places- Konkan & Goa, South Interior Karnataka, Kerala & Mahe and Tamil Nadu, Puducherry & Karaikal. Few places- Gujarat Region Isolated places- Madhya Maharashtra, Vidarbha, Coastal Andhra Pradesh & Yanam and Lakshadweep.  37.1-Palakkad (Kerala & Mahe).
16.02.2020 Many places– Saurashtra & Kutch.Most places- East Rajasthan and Gujarat region. Many places- Konkan & Goa, Coastal & North Interior Karnataka and Lakshadweep. Few places- South Interior Karnataka. Isolated places- Telangana, Coastal Andhra Pradesh & Yanam.36.6- Gulbarga (North Interior Karnataka).
17.02.2020Few places- Saurashtra & Kutch and Konkan & Goa.Many places– Gujarat region; Few places– Kerala & Mahe.Few places– Vidarbha, Madhya Maharashtra and Coastal Karnataka. Isolated places– Interior Karnataka and Coastal Andhra Pradesh. 38.1- Santacruz (Mumbai).                               
18.02.2020Many places-Saurashtra & Kutch and Konkan & Goa.Most places- Gujarat Region. Isolated places– Madhya Maharashtra, Vidarbha, Kerala & Mahe.Few places-Coastal & South Interior Karnataka and Tamil Nadu, Puducherry & Karaikal. Isolated places– Lakshadweep.  37.5- Vengurla (Konkan & Goa).
19.02.2020Few places- Saurashtra & Kutch.Many places- Gujarat Region and Konkan & Goa. Isolated places– Vidarbha, Madhya Maharashtra.Many places– Marathawada and Kerala & Mahe. Few places- Coastal Karnataka and Tamil Nadu, Puducherry & Karaikal. Isolated places-North Interior Karnataka.36.6 – Amreli (Saurashtra & Kutch) and Gulbarga (North Interior Karnataka).

Table 2: Stations exceeding 35 °C Maximum Temperature

DateSub-divisionsMaximum Temperature (Stations) in °C
14.02.2020Konkan & Goa Coastal Karnataka North Interior Karnataka Kerala TamilnaduMumbai- 35.1, Ratnagiri-36.6 & Vengurla- 37.7, Karwar -36.5, Gulbarga-35.4, Cannur-35.2, Pallakad-36.4, Thrissur-36.3, Cochin-35.4, Kottyam-36.4, Punalur-37.5, Selem-35.1, K. Paramarthy-35.5, Madurai-35.4
15.02.2020Madhya Maharashtra,  Marathbada Coastal Karnataka, North Interior Karnataka,  Kerala,  TamilnaduAhmednagar-35.4, Solapur-35.2, Karwar-35.4, Gulbarga-36.9,  Cannur-35.4, Pallakad-37.1, Thrissur-36.5, Kottyam-35.5, Punalur-35.5, Selem-36.2, K. Paramarthy-35.8, Madurai-35.6, Tiruchchirapalli-35.2
16.02.2020Saurashtra & Kutch,  Gujarat, Madhya Maharashtra, Coastal Karnataka, North Interior Karnataka, KeralaBhuj-35.1, Surat-35.9, Sanghi-35.2, Shirli-35.1, Manglore-35.7, Gulbarga-36.6, Cannur-36.2, Thrissur-36.5, Kottyam-35.7, Punalur-36.6, Kozhocode-36.0
17.02.2020Saurashtra & Kutch, Gujarat, Madhya Maharashtra, Vidharbha,   Konkan & Goa Coastal Karnataka, North Interior Karnataka, KeralaBhuj-35.8, Nalia-35.4, Kandla-35.2, Rajkot-35.8, Porbandar-36.2, Amerli-36.2, Mahua-35.4, Surat-36.4, Dessa-35.9, Sanghi-35.3, Solapur-36.0, Ahmednagar-35.0, Akola-35.2, Mumbai/Santacuuz-38.1, Ratnagiri-36.8, Vengurla-36.4, Goa-36.5, Karwar-35.3, Manglore-36.8, Gulbarga-36.7 Cannur-37.2, Thrissur-35.7, Kottyam-37.8, Punnalur-36.6, Cochin-36.7
18.02.2020Saurashtra & Kutch, Gujarat Madhya Maharashtra, Vidarbha, Konkan & Goa, Coastal Karnataka, North Interior Karnataka, Kerala.Bhuj-36.8, Nalia-36.0, Kandla-35.4, Rajkot-36.8, Porbandar-36.0, Amerli-36.8, Mahua-36.0, Dwarka-35.3, Sundernagar-35.8, Keshod-36.6),Surat-36.9, Baroda-36.1, Ahmedabad-35.3, Sanghi-35.4, Solapur-35.6, Akola-35.9 Ahmednagar-36.2, Jeur-35.2, Mumbai/Santacuuz-36.5, Ratnagiri-37.0, Vengurla-37.5, Goa-36.3, Kolaba-35.6, Karwar-36.2, Manglore-35.2, Gulbarga-36.2, Cannur-37.2, Thrissur-35.3, Kottyam-35.5, Punnalur-35.5, Cochin-36.0), Tamilnadu (Madurai-36.8
19.02.2020Saurashtra & Kutch, Gujarat, Madhya Maharashtra, Vidarbha, Konkan & Goa, Marathbada, Coastal Karnataka, North Interior Karnataka, Kerala, TamilnaduRajkot-35.3, Amreli-36.6, Sundernagar-35.7, Baroda-35.0,  Jalgaon-35.4, Malegaon-36.0, Sanghi-35.5, Jeur-35.0, Akola-36.2, Brahemapuri-36.0, Mumbai/Santacuuz-34.8, Parbhani-35.1, Solapur-36.4, Ratnagiri-35.1,  Manglore-35.1, Gulbarga-36.6, Cannur-35.4, Thrissur-35.7, Kottyam-35.2, Cochin-36.1, Madurai-36.4

From the above it is observed that about 5 stations in Kerala are reporting maximum temperatures above 35°C daily. It is also observed that   on 17.02.2020 & 18.02.2020 the number of stations more than 35°C increased in Saurashtra & Kutch, Gujarat, Konkan & Goa and Mumbai recorded the highest temperature in that day. Then on 19.02.2020 temperature reduced slightly and the number of stations with maximum temperature more than 35°C reduced. Madurai in Tamilnadu also reporting maximum temperature above 35°C.

3. Associated synoptic features and wind analysis

Figure 1 shows IMD: GFS Model (12 Km) 925 hPa Wind (kt) for 00 UTC of 13th to 19th February, 2020.  

Figure 1(a) shows that on 13th February, strong north-westerly winds were prevailing over north-west India, however south-westerly, easterly winds over south India on that day. Figure 1(b) & (c) show that on 14th & 15th February, strong north-westerly winds were prevailing over north India, however southerly, south-easterly winds were prevailing over west and south India on that day. Figure 1(d) shows that on 16th February, southerly, south-easterly winds were prevailing over west and south India on that day. Figure 1(e) shows that on 17th February, easterly, south-easterly & South-westerly winds were prevailing over west and south India on that day. Figure 1(f) shows that on 18th February, south-easterly & South-westerly winds were prevailing over west and south India on that day. Figure 1(g) shows that on 19th February, southerly & South-easterly winds were prevailing over west and south India on that day.

Table 3: Feb 2020 – List of Western Disturbances (WD)

1. Western Disturbance (30th January, 2020 -02nd February, 2020)
2.  Western Disturbance (02nd February, 2020 -06nd February, 2020)
3. Western Disturbance (05th February, 2020 -08th February, 2020)
4. Western Disturbance (10th February, 2020 – 13th February, 2020)
5. Western Disturbance (11th February, 2020 – 15th February, 2020)
6. Western Disturbance (15th February, 2020 – 17th February, 2020)

7. Western Disturbance (17th February, 2020 –     19th February, 2020)  

Table 3 shows the list of WD affected northern India during 1st fortnight of Feb 2020. It shows total 7 WDs (average is 2 WD) have affected.

Northwesterly winds could not penetrate up to North Tamil Nadu and North Karnataka and Kerala. These winds remained absent as successive Western Disturbances kept inducing cyclonic circulations over Rajasthan and central parts of the country, leading to the occasional formation of confluence that blocked cold northerly winds from reaching southern states. Interaction between easterly and westerly could get rain over eastern India but not over south and west India. Frequent WDs impacted North, Central, east and northeast India.

From the synops of different stations it is found that most of the time week winds up to 5 knots prevailed with no northerly components. Westerly, easterly or south-westerly winds prevailed and this helped for higher temperature over these areas.

Possible reasons for above normal temperature in South India including west coast and Saurashtra & Kutch and Gujarat may be;

1.During past six to seven days no major rainfall activity reported over these areas. Almost weather remained dry over these areas.

2. Transition phase from winter to summer.  Although February is a transition period for southern states from winter season, during this entire winter season, cold wave from the north had not reached the region.

  • Summary

In this report an attempt is made to find out the possible reasons of appreciably above normal maximum temperatures across west and southern part of India during 13-19 February, 2020. Details of the observed maximum temperatures are listed in this report.

During the month of February, 2020 Seven WDs observed and all of them affected North, Central and East and North-East India with good rainfall activities. But such frequent mid latitude WDs resulted westerly pattern to be dominate mode.  Resulting into, no major rainfall activities over the West and South India and mainly dry weather prevailed in most January and February including the period of 13th February to 19th February for these areas. Also, during 13th February to 19th February, no northerly winds prevailed over the region resulting into above normal maximum temperatures during 13th February to 19th February. 

Report Compiled by:

Shashi Kant, Surendra Pratap Singh, R. K. Jenamani

Heat Wave conditions over India

During hot weather period (March to July) surface temperatures over many parts of India abnormally shoot up, particularly over North and central India. Annual cycle of All-India daily maximum and minimum temperatures is as given in the below figure.

Figure 1: Annual cycle of All-India daily maximum and minimum temperatures.

As per the above figure, maximum temperatures are highest in pre-monsoon days and started decreasing in monsoon days.

As per India Meteorological Department’s criteria, Heat Wave conditions are defined as:

 Heat Wave:

It should be based on the actual maximum temperature of a station. Heat Wave is considered when maximum temperature of a station is 400C or more for plains and 30°C or less for Hilly regions. 

Based on Departure

Heat Wave:  Positive Departure from normal is 4.5°C to 6.4°C

Severe Heat Wave:  Positive Departure from normal is more than 6.4°C

Based on Actual Minimum Temperature    (For plain stations only)

Heat Wave:                                 When maximum temperature is ³45°C

Severe Heat Wave:                     When minimum temperature is ³47°C

Heat Wave conditions for coastal stations

When minimum temperature departure is +4.5°C or more over a station, “Heat Wave” may be described if the maximum temperature is 370C or more.

To declare heat wave, the following criteria should be met at least in 2 stations in a Meteorological sub-division for at least two consecutive days and it will be declared on the second day.  Forecasts of heat wave over a sub-division will be issued only if at least two stations in the sub-division are expected to experience such conditions.

  • Heat wave occurs mostly over an interior plain area when dry and warmer air is transported in a region with clear skies and hence maximum isolation during the summer season.
  • Bay islands, Lakshadweep, Tamil Nadu, Kerala, Coastal and South Interior Karnataka are not affected by heat waves due to the occurrence of maritime air over these regions.
  • Heat waves generally develop over Northwest India and spread gradually eastwards & southwards but not westwards (since the prevailing winds during the season are westerly to northwesterly). But on some occasions, heat wave may also develop over any region in situ under the favorable conditions.

Heat wave impacts rural and urban areas, natural habitats like forests, water resources, poultry and a range of sectors like agriculture, health, power etc, Though there is no universally acceptable or uniform definition for a heatwave, they are understood to be periods of abnormally high temperatures, more than the normal maximum temperature that occurs during the pre-monsoon (April to June) summer season. In India heat -waves typically occur between March to June, and in some rare cases even extend till July. Heat waves are more frequent over the Indo-Gangetic plains of India.

Health Impacts of Heat Waves

The health impacts of Heat Waves typically involve dehydration, heat cramps, heat exhaustion and/or heat stroke. The signs and symptoms are as follows:

  • Heat Cramps: Ederna (swelling) and Syncope (fainting) generally accompanied by fever below 39°C i.e.102°F.
  • Heat Exhaustion: fatigue, weakness, dizziness, headache, nausea, vomiting, muscle cramps and sweating.
  • Heat Stroke: body temperatures of 40°C i.e. 104°F or more along with delirium, seizures or coma. This is a potentially fatal condition.

What causes a heat wave?

  • A heat wave is formed when static high pressure generated in the upper atmosphere over a region for several days. This static high pressure generates a hot mass of air, which is stagnant for many days, which resulted the trapping of more heat that also reduce the convection currents. The high pressure acts as a barrier and forces the mass of air to sink to the surface of the land that prevents heat to rise.
  • This hot mass of air accumulates only heat and humidity without any trace of precipitation that causes abnormally high temperatures. It is very often during the summer season, from March to July in the Indian Region.
  • Seasonal climatology map of number of HW days and SHW days over India during the hot weather season (March – July) for the period 1961-2010 is as in Figure 2.
Figure 2: Seasonal climatology map of number of HW days and SHW days over India during the hot weather season (March – July) for the period 1961-2010.

Monitoring and forecasting process:

IMD utilizes all its resources to monitor heat wave round the clock. It issues forecast& warning with a lead period of 05 days against the heat wave to the general public, disaster managers, media and other stake holders using following Impact Based Forecast table as per requirement of Disaster Management.

Figure 3: Impact Based Warning Forecast table followed by India Meteorological Department.

Compiled By: Surendra Pratap Singh, Naresh Kumar.

Cold Wave & Cold Day conditions over North India

Introduction:

The plains of North India experience Cold Wave and Cold Day conditions during winter season (December-February) every year. It is a severe weather phenomenon which causes loss to life and public property. As per India Meteorological Department’s criteria, Cold Wave and Cold Day conditions are defined as:

(A)   Cold Wave:

It should be based on the actual minimum temperature of a station. Cold Wave is considered when minimum temperature of a station is 100C or less for plains and 0°C or less for Hilly regions. 

Based on Departure

        i)          Cold Wave:                           Negative Departure from normal is 4.5°C to 6.4°C

       ii)         Severe Cold Wave:                Negative Departure from normal is more than 6.4°C

Based on Actual Minimum Temperature    (For plain stations only)

  1. Cold Wave:                                 When minimum temperature is ≤ 04°C
  2. Severe Cold Wave:                     When minimum temperature is ≤ 02°C

Cold Wave conditions for coastal stations

When minimum temperature departure is -4.5°C or less over a station, “Cold Wave” may be described if the minimum temperature is 150C or less.

(B)   Cold Day:

It should be considered when minimum temperature is 100C or less for plains and 0°C or less for Hilly regions.

Cold day:                   Maximum Temperature Departure is -4.5°C to -6.4°C

Severe Cold day:       Maximum Temperature Departure is < -6.4°C   

Factors causing Cold Wave Conditions:

  • Cold Wave conditions are associated with fall in minimum temperatures during the Winter season. In this season prevailing winds over the Indo Gangetic Plains (IGP) are northwesterlies. As northwesterlies are the winds from colder regions of Central Asia/Hindukush region, they bring temperature fall over the IGP and hence the Cold Wave Conditions.
  • Whenever a Western Disturbance (WD) approaches clouding develops over IGP bringing fall in Maximum temperatures and rise in minimum temperatures. Thus, Cold Wave conditions over IGP get abated at the approach of a WD.
  • When a WD moves away from the Indian region, clear skies start appearing over the IGP leading to rise in maximum and fall in minimum temperatures.
  • Whenever a WD affects North India, winds in lower levels over the region are either from Arabian Sea or from both Bay of Bengal and Arabian Sea. Given that both types of winds are the moist ones, minimum temperatures rise. At the same time, clouding over the region leads to lesser penetration of solar insolation into the earth and hence fall in maximum temperatures.
  • Formation of an anticyclone in lower and mid tropospheric levels is also a driver of Cold Waves. Such an anti-cyclone gives rise to sinking motion over the IGP leading to fall in minimum temperatures.

Factors causing Cold Day Conditions:

  • Cold Day conditions are associated with fall in maximum temperatures during the Winter season. Cold Day conditions occur when there is persistent low clouding over North Indian plains/IGP in the winter season.
  •  Low clouds prevent solar insolation entering into earth’s surface which causes fall in maximum temperatures.
  • Left entrance and right exit of a Jet core belong to upper level convergence which in turn causes sinking motion over the surface hence causing Cold Wave and Cold Day conditions.
  • If an active WD affects North India in the winter season and causes widespread rain over the region along with isolated hailstorms it leaves behind abundant moisture over the IGP. Now if after the passage of the WD, lower level westerlies (cold and dry) are not strong enough to absorb this abundant moisture it will cause persistent low cloud cover and hence the Severe Cold Day conditions over the region. Similar phenomenon was witnessed during second half of December, 2019. (Figure below)
  • Development of anomalous high over the region causes low cloud cover which in turn leads to preventing the solar heating of the earth surface and hence the severe cold day conditions. (Figure below)
Figure: Ridge and trough lines being shown in 925 hPa mean geopotential height chart for 16-31 December, 2019.

Monitoring and forecasting process:

IMD utilizes all its resources to monitor round the clock forecast with a lead period of 05 days and warn against the adverse weather to the general public, disaster managers, media and other stake holders. For monitoring the weather systems, IMD uses all type of Synoptic charts, INSAT-3D Rapid half hourly imagery, every 10 minutes DWR products for Srinagar, Patiala, Delhi, Lucknow, Jaipur and Bhopal. Various Numerical Prediction Models like IMD GFS, WRF, ECMWF, NCMRWF NCUM, GEFS and various international models are utilized for this purpose. The digitized decision support system known as SYNERGIE was utilized for decision making and for development of consensus forecast.

Compiled by: Krishna Mishra & Naresh Kumar.

Western Disturbances and associated weather

Western disturbances are the weather systems which are seen as extra tropical upper air trough (extended low pressure area) or/and cyclonic circulations (CCs) (winds that circulates anti-clockwise around the low pressure area) in mid- latitude westerlies that move from west to east across Himalayan region. Under the influence of these systems, sometimes CCs develop south of the system at lower levels called induced CC. Sometimes the western disturbances can appear as a low pressure area under favourable condition. A low can sometimes (though rare) intensify into depression, which is called Western Depression. 

These systems originate mostly over Mediterranean Sea & Caspian Sea. However some of the systems come from North Atlantic Ocean also. Thereafter, it moves eastward while causing precipitation over Iraq, Iran, Afghanistan and Pakistan. Subsequently, it causes weather in the form of rain/snow over Western Himalayan region (Jammu & Kashmir, Himachal Pradesh and Uttrakhand) and adjoining northern plains. If this system gets moisture from Arabian Sea, then it causes heavy precipitation over the region, otherwise it causes only light to moderate precipitation.

Sometimes, these systems do not completely weaken over Indian region and move east-northeastwards after getting moisture feed from Arabian Sea and cause precipitation over Nepal, Sikkim and northeastern states & adjoining East India. Sometimes, the WDs can cause rainfall even over Central & adjoining south Peninsular India. The typical example of WD, which causes intense precipitation over Western Himalayan region is given below in Figure 1.

Figure 1: Typical WD trough in mid-tropospheric levels

In the above Figure 1, WD is seen as a cyclonic circulation over north Pakistan & neighbourhood along with a trough running from the centre of the circulation to Arabian Sea at mid-tropospheric levels. Sometimes under the influence of WD, a low or CC develops to the southeast sector of the main system at higher levels. Then, it is called as the ‘Induced low’ or ‘induced CC’. Most of the times, induced CC develop over West Rajasthan & neighbourhood at lower tropospheric levels and move mostly northeastward. In some cases, there is moisture feeding from the Arabian Sea also at lower tropospheric levels over northwest India due to induced CC, moderate to heavy rainfall also occurs over plains of northwest India as shown in following Figure 2.

Figure 2: Moisture feeding caused by anti CC over Bay of Bengal

In the figure 2, there is induced CC over central Pakistan adjoining areas of Punjab & West Rajasthan. Winds are from Arabian Sea indicating moisture feed from the sea. This is an ideal condition for intense rainfall over northwest India. Rainfall along with thunderstorm, lightning and hailstorm over central parts of country due to mixing of two air masses over Central India, one from Arabian Sea and other from Bay of Bengal due to anti-CC over Bay of Bengal.

In addition to above factors, the strength of Jet Stream (upper tropospheric narrow currents having width of a few hundred kms, length thousands of kms and wind speed>60 knot) at 200 hPa level plays very vital role in the intensity of the system. If there is strong Jet Stream wind of order 150 knots or more, it cause high divergence at higher altitudes, as a result system becomes more intense (Figure 3).

Figure 3: Jet Stream of the order 150 kts causing high divergence

Typical example of high divergence due to strong jet stream wind is shown below in Figure 4.

Figure 4: High divergence caused by strong Jet Stream

Generally, high convergence at lower levels & high divergence at higher levels over Western Himalayan Region & adjoining plains are seen before commencement of widespread precipitation along with heavy falls.

Following meteorological features are seen before the approach of WD over a station, in general: 

  • Fall of pressure (can be noticed by P24 P24 values).
  • Rise in minimum temperatures and the dew point. 
  • Approaching cloud sequence: First High clouds, then medium and then low clouds and followed by rain/snow

Following meteorological features are observed after the passage of WD over a station: 

  • Rise in pressure.
  • Fall in minimum temperature, sometimes leading to cold wave condition and fall in dew point indicates dry weather.
  • Clear sky.
  • Fog in rear as well as forward sector of WD 

Compiled by: Naresh Kumar & Anand Sharma.

Celebrating 145th Foundation Day on 15th January 2020 (India Meteorological Department: inheritance of 145 years’ serving the Nation)

India Meteorological Department (IMD) is the National Meteorological Service of the country & the principal Government agency in all matters related to meteorological & allied disciplines. The Department provides weather & climate services for the Public safety and socio-economic benefits.

Vision

 The vision of IMD is to provide efficient Weather and Climate Services for safety of life and property and to contribute towards the National development.

 Mission

 ·  To carry out meteorological observations for current weather information and to issue timely weather forecasts / meteorological information for optimum operation of weather sensitive sectors like agriculture, irrigation, shipping, aviation, offshore oil explorations, tourism, surface transport, power generation and distribution, etc.

 · To warn against severe weather phenomena like tropical cyclones, thunderstorms, dust storms, wind squall, heavy rains, snow, cold and heat waves, etc., which cause destruction of life, property & livelihood.

 · To issue Quantitative precipitation forecast for flood management to Central Water Commission and other agencies.

· To provide Climatological information for planning agriculture, water resource management, industries, oil exploration and other nation building activities.

 · To conduct and promote research in Meteorology and allied disciplines.

Today, the 15th January 2020, when we enter into our 145th year of serving the Nation with weather & Climate information, thought it would be apt to look back a bit and reminisce on the evolution of IMD.

Looking back:

Long ago, in the year 1864, the city of Kolkata (then Calcutta) was devastated by a Cyclone, claiming innumerable lives. The cyclone had crossed this part of the east coast of India to the south of Hooghly River, around 10 AM of 5th October 1864. Huge Tidal waves washed away nearly everything in the City including the harbor (Gastrell & Blanford 1866).

The immediate 7 years that followed also witnessed two severe droughts & famines due to acute shortfall in the monsoon rainfall over India (Hunter, 1886).

These natural calamities led the Government to establish a central agency to organize the monitoring & forecasting of such meteorological & hydrological disasters for the benefit of the people.

India Meteorological Department was established in the year 1875 with its headquarters in Kolkata.

Alipore observatory, Kolkata 1877

The headquarters was shifted to Shimla in 1905, to Pune in 1928, then to Delhi in 1944 and since then it is in Delhi.

IMD, Pune – 1928
IMD, Delhi – 1944

Ancient wisdom

The beginnings of meteorology in India can be traced to ancient times. Early philosophical writings of the 3000 B.C. era, such as the Upanishadas, contain serious discussion about the processes of cloud formation and rain and the seasonal cycles caused by the movement of earth round the sun. Kautilya’s (321 -296 BC) Arthashastra contains records of scientific measurements of rainfall and its application to the country’s revenue and relief work.  Varahamihira’s classical work, the Brihat samhita, written around 500 A.D., provides clear evidence that a deep knowledge of atmospheric processes existed even in those times. It was understood that rains come from the sun (Adityat Jayate Vrishti – embedded in IMD’s emblem) and that good rainfall in the rainy season was the key to bountiful agriculture and food for the people. Kalidasa in his epic, ‘Meghdoot’, written around the seventh century, even mentions the date of onset of the monsoon over central India and traces the path of the monsoon clouds.

Meteorology, as we perceive it now, may be said to have had its firm scientific foundation in the 17th century after the invention of the thermometer and the barometer and the formulation of laws governing the behaviour of atmospheric gases. It was in 1636 that Halley, a British scientist, published his treatise on the Indian summer monsoon, which he attributed to a seasonal reversal of winds due to the differential heating of the Asian land mass and the Indian Ocean.

In India, we have some of the oldest meteorological observatories of the world. The British East India Company established several such stations, for example, those at Calcutta in 1785 and Madras (now Chennai) in 1796 for studying the weather and climate of India. The Asiatic Society of Bengal founded in 1784 in Calcutta, and in 1804 in Bombay (now Mumbai), promoted scientific studies in Meteorology in India. Captain Henry Piddington in Calcutta published 40 papers during 1835-1855 in the Journal of the Asiatic Society dealing with tropical storms and coined the word “cyclone”, meaning the coil of a snake. In 1842 he published his monumental work “The Sailors’ horn-book for the Law of Storms”. In the first half of the 19th century, several observatories began functioning in India under the provincial governments.

The above depicted ancient wisdom laid a strong foundation for the initial activities of IMD since its inception in 1875.

Early years

Evolution of different aspects of the Meteorological & Hydrological services in the early years in its finest details can be read at Hundred Years of Weather Service (1875-1975) view pdf

It may be noted that though the beginning was a humble one, it never fumbled in its duties.

Milestones

  • India has some of the oldest Meteorological Observatories of the world. First Astronomical and Meteorological Unit was started at Madras in 1793.
  • In 1875 all Meteorological work in the country was brought under a central authority with the establishment of India Meteorological Department.
  • Advent of telegraphy enabled centralised data reception and publication of the All India Daily Weather Report since 1878. The first weather charts were printed in the Weather Reports in 1887.
  • Seismological activity started in India with the establishment of the first observatory at Alipore, Calcutta in 1888.
  • First Meteorological observatory in the country was established in Chennai in the year 1792.
  • Upper air measurements of winds started in 1905 by the method of tracking balloons with theodolites.
  • A separate division was created in 1932 for research activities in the field of Agricultural Meteorology.
  • RADARs were pressed into aviation weather service as early as 1954.
  • The positional Astronomy Centre- then known as Nautical Almanac Unit was established in 1955.
  • Environmental Meteorology took shape in India with the first Ozone measurement at Kodaikanal in 1957.
  • IMD started receiving satellite images from US Satellites in 1964.
  • Meteorological training facilities created in 1942 and upgraded to a Directorate in 1969 is now the Regional Meteorological Training Centre of the WMO.
  • Directorate of Telecommunication was set up in 1970 to rapidly exchange information amongst various centres.
  • The Telecom age ushered in the prospects of global data assimilation and numerical weather forecasting in 1973.
  • The National Data Centre at Pune was created in 1977 for scrutinising and archiving all Meteorological data in computerized form.
  • INSAT provided a Geostationary platform for remote sensing of the atmosphere and automatic data collection in 1982.
  • First Meteorological station at Antarctica was established in 1983 by IMD.
  • First Global Seismological Network (GSN) standard broad band seismological observatory was set up at Pune in 1996.
  • The Internet has opened avenues to provide better services. IMD created its official website in 2000.
  • 125 Years of Service to the Nation (1875-2000)  view pdf
  • In 2002 Doppler Weather Radars (DWR) were inducted in the cyclone detection network which enable precise estimate of intensity of cyclone.
  • Meteorological Data and INSAT Imagery were launched through World Space Digital Data Broadcast System in 2003.

From a modest beginning in 1875, IMD has progressively expanded its infrastructure for meteorological observations, communications, forecasting and weather services and it has achieved a parallel scientific growth. IMD has always used contemporary technology. In the telegraph age, it made extensive use of weather telegrams for collecting observational data and sending warnings. Later IMD became the first organisation in India to have a message switching computer for supporting its global data exchange. One of the first few electronic computers introduced in the country was provided to IMD for scientific applications in meteorology. India was the first developing country in the world to have its own geostationary satellite, INSAT, for continuous weather monitoring of this part of the globe and particularly for cyclone warning.

IMD has continuously ventured into new areas of application and service, and steadily built upon its infra-structure in its history of 145 years. It has simultaneously nurtured the growth of meteorology and atmospheric science in India. Today, meteorology in India is poised at the threshold of an exciting future.

References:

  • Gastrell J E., Blanford, H.F, ‘Report on the Calcutta Cyclone of the 5th October 1864’, O.T. Cutter Military Orphan Press, 150 pp.
  • Sir William Wilson Hunter, ‘The Imperial Gazetteer of India’ 1886, vol.8, page 40.