The Indian Meteorological Department (IMD) was formally constituted in 1875. Both before this formal organisation came into being and after its establishment, a series of initiatives were taken in the field of weather observation and their documentation and analysis. Notable examples were the first meteorological observations at the Madras observation in the late 18th century , setting up of a large number of rain gauges in the 19th century and the compilation of their data by Blanford (1886) the first Meteorological Reporter to the Government of India, the formulation of the structure of the tropical cyclone by Paddington (1848) in Calcutta , the meteorological observations relating to the total solar eclipse (1898) organized by Eliot, the introduction of upper air observation with pilot balloon and Dines meteor graph in the early 20th century and the radiosonde observation from the 1940’s.

There were also many field observation campaigns on thunderstorms and nor’wasters in the 1920’s, 30’s and 40’s. In this series of initiatives we can place the acquisition of RADARs (Radio Detection and Ranging) for weather observation in the early 1950’s, making the IMD one of the pioneers in the world in the area of Radar Meteorology.

The History of Radar Meteorology in India can be traced back to the days of the High frequency Ionospheric Sounders. Working with these, Prof S.K. Mitra and his group at the University of Calcutta in the 1930’s discovered a layer of echoes below the D and E regions of the ionosphere and termed it the “C-region of the Ionosphere”. It was shown much later that these echoes were from the un-ionised layers of the atmosphere and occurred due to scattering form refractive index in homogeneities. These are exploited nowadays for various studies of the atmosphere.

Mitra’s work was before the invention of pulsed microwave RADAR which happened during World War II. Radar played a crucial role in the war and the development of radar was hastened by the needs of war.

Meteorologists found that radar gave echo returns from rainfall and took advantage of them for studies in meteorology. In India, during the war, the Royal Air Force used military radars which gave, as a by product, information of meteorological interest, notably on anomalous propagation (a phenomenon related to low- level temperature and humidity profiles in the atmosphere) of radio waves over very long distances across the Bay of Bengal and the Arabian sea.

Soon after the war, IMD acquired war disposal (military) radars for gaining first-hand experience and initiating research in Radar Meteorology. These were the Baby Maggie radars (operating frequency 200 MHz) used to track radio sound balloons for wind measurement, the AN/APQ-13 (10 Ghz, wavelength 3 cm, called X – band )) and SCR-717c (3 GHz, 10 cm, S-band ) for weather observations. The latter was used at Pune effectively in a mobile configuration with horizon to horizon scanning to study the melting band in stratiform monsoon precipitation. The first radar to be acquired for operational use was the Decca Type 41 radar (an aircraft tracking radar adapted for meteorological use) installed at Dum Dum Airport (Kolkata) in 1954. More such radars were installed at other airports, the main purpose being to detect thunderstorms in the vicinity for warning aviators. The first radar designed specifically for meteorology, the AN/CPS-9 (Xband) was obtained through a US aid programme and installed in New Delhi (Safarjang) in 1957.

History of Radar goes much ealier than this. Lot of surplus equipment left by Americans after the World War II were also bought almost by weight with the foresight of officers. Two Radars were sent to Pune and two were kept in Delhi. A special, small building was made on the other side of the Safdarjang Airport. The tower still stands as witness of RADAR. It was the most powerful Radar in entire Asia. China and Japan did not have Radar till then. A large tower of 75 ft was erected. The Radar arrived at Palam Airport and truly brought to the building in bullock carts. It was a problem how to put it on a 75 ft tower. No helicopter took up that job as they were not specialised for this kind of assignments. Cranes to handle this kind of jobs were not available at that time. The standard, indigenous chain pulley system was used by the highly skilled contractors who did the job.

A Japanese X-band radar was installed at Kolkata and a similar one at the Rain and Cloud Research Unit of the National Physical Laboratory at New Delhi. The latter came in due course under the control of the Indian Institute of Tropical Meteorology, Pune. All these were used by various researchers in the IMD and the Rain and Cloud Unit to document and classify convective clouds and thunderstorms notably nor’westers of estern India and associated phenomena (such as and his) and build up useful climatologies of their properties.

The Rain and Cloud Unit radar was also useful in cloud physics and weather modification studies. An important early result from these radars was the finding (supported by high-flying jet aircraft observations) that monsoon clouds in much of north India extended to considerable heights sometimes overshooting the tropopause. This was a new finding because ( in the absence of observations) it was thought by many meteorologists earlier, that monsoon rain is mostly of warm origin and clouds rarely extend much beyond the freezing level. This warm rain hypothesis was largely true of monsoon rain on the west coast of peninsular India, but not necessarily in other parts of India. More quantitative studies such as the size distribution of radar echoes and fractal dimensions, leading to inferences of a more fundamental nature also became possible during the 1970s and later with the installation of new radars. Quantitative estimation of precipitation and comparison with rain gauges were also carried out though these were not operationalised at that time.

In the late sixties, an indigenous capability to manufacture radars was established in Bharat Electronics Ltd (BEL). X – band and later S-band radars were supplied to IMD by BEL.

Considering the importance of detection and tracking of tropical cyclones affecting the Indian coasts, a group of 10 S-band radars was planned. The first one was installed at Visakhapatnam in 1970. Accurate tracking of cyclones leading to more accurate forecasts is probably the greatest contribution weather radar has made in India. Due first impact of the new radars was Ehen a cyclone crossing the Tamil Nadu coast was tracked for over 24 hours in 1972 for the first time in India, leading to a good forecast saving many lives and property damage. This was appreciated by the public and the State Government.

The observation of cyclones also enabled study of the structure and other features of cyclones. The use of multiple radars and the Indian National Satellite (INSAT) which became available in the 1980s led to reliable tracking of cyclones and further improvement of forecasts and timely warnings.

These radars were capable of only mapping the “radar reflectivity factor” and there was no means of determining the velocity of air motion in the echoes. The maximum wind velocity in a cyclone and the radius of maximum winds (RMW) are important parameters for assessment of intensity of the cyclone and prediction of the storm surge which is the most destructive phenomenon in the cyclone. A technique was developed in the IMD for estimating the RMW from radar imagery and implemented in the 1980s. The determination of maximum velocity had to wait for the installation of Doppler radars at the turn of the century.

In the 1990s IMD took a major step forward to introduce digital Doppler Radars in its network gradually replacing the old analog reflectivity-only radars. Imported S-band digital Doppler radars are functioning in the last 10 years at Chennai, Machilipatnam, Viskhapatnam and Kolkata as part of the Cyclone Detection network. Simultaneously under a collaborative programme the Indian Space Research Organisation (ISRO) designed an indigenous Doppler radar for IMD and it has been manufacture a Mark-II version for IMD, ISRO and other organisations.

The digital and Doppler capability increases the versatility of the radars several fold. Besides reflectivity factor which is the basic output of all radars, these give additional output of echo velocity and its variance. Using these outputs it is possible to derive several products of operational meteorological interest. Distribution of rainfall rates, accumulated rain over a period of time, vertical profile of wind, signatures of cyclones and tornadoes, maximum wind in cyclones, wind shear and turbulence, probability of severe weather and hail and the likely size of hailstones are among the important products. These derived products make use of several assumptions and therefore calibration of the radar and validation of products is a continuing process. Radar displays are transmitted by internet and some of these are available to the public.

Digital radar data are being assimilated into Numerical Weather Prediction (NWP) models. This opens up numerous possibilities for weather analysis and forecast of various weather phenomena especially on the “meso-scale”. Besides operational use, meteorological research using radar data in conjunction with other surface- and satellite meteorological data by various organisations is being pursued.

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In a new study, Northeastern earth and environmental sciences professor Jennifer Cole has discussed what causes earthquakes and how one natural disaster can lead to another.

As to what causes earthquakes, Cole says that they result from the movement of tectonic plates.

As tectonic plates slide past each other, energy builds up in the rocks until they can no longer hold the stress.

This causes failure in the form of breaking rocks, sending energy waves outward.

The earthquakes in Haiti, China, Japan, and Chile all happened because of this series of events.

Glaciers may also cause earthquakes.

During the last glacial period, the ice sheet was up to 2.5 miles thick. This pushed down on the Earth’s crust, causing a depression.

When the weight was lifted due to glacial melting, the depressed crust began to stick-slip on its way back to the pre-depressed elevation.

In addition, humans can cause earthquakes by damming rivers, creating a reservoir heavy enough to cause a depression in the earth’s crust.

A massive earthquake is usually followed by a sequence of aftershocks, landslides and tsunamis.

Earthquakes are capable of causing tsunamis.

In the unique case when an earthquake occurs on the ocean floor, a rock is forced up, causing a disturbance in the water column that extends to the ocean surface.

Waves then travel outward in a series of concentric circles at a rapid rate, up to 550 miles per hour, or as fast as a jet airplane travels.

When tsunamis reach shallow water, they slow down and grow taller, forming massive waves.

These waves travel inland and cause flooding and increase the potential of coastal landslides.

Some scientists are making the case that global warming is contributing to an increase in earthquake activity by making the ocean water warmer, and therefore, heavier.

Additionally, melting glaciers take weight off of tectonic plates, which can cause them to pop upwards in those areas, resulting in earthquakes.

At first glance it looks like aliens are using the sun for target practice.

A string of bullet-shaped streaks of light appear to be shooting straight toward the sun.

These are the proverbial snowballs in Hell, plunging 300 miles per second toward a fiery end in the sun’s atmosphere.

The NASA/ESA Solar and Heliospheric Observatory (SOHO) observed the demise of one comet fragment on Friday, March 12.

The wayward comets are called sungrazers. They are a class of comet that likes to live dangerously. Sungrazers can skirt within a few thousand miles of the sun’s roiling photosphere. Many are torn apart or evaporate as they streak along at a blazing 1 million miles per hour. As their orbits are perturbed, surviving sungrazers can collide with the sun on a subsequent passage.

The first recognized sungrazing comet was detected during a total solar eclipse in May 1882. Just imagine the surprise and awe as a glowing streak of light appeared to observers as the sun entered totality. Other sungrazers have been briefly bright enough to be seen in the daytime sky alongside the sun. The most recent, comet Ikeya-Seki in 1965.

Once solar observing satellites were lofted into orbit the sungrazers were easily detected. SOHO, with its coronographs, has cataloged over 1,000 sungrazers in spectacular passages.

But we missed the real fireworks by 4 billion years. The period of late heavy bombardment in the newborn solar system should have seen the sky around the sun ablaze with sungrazers.

Evidence comes from observations of the young Beta Pictoris system that is believed to have recently formed planets. Since the early 1990s astronomers have monitored transient events in the star’s visible spectrum that are interpreted as resulting from evaporating comets skirting Beta Pictoris.