Skymet weather

QBO – NORTHEAST MONSOON INDICATOR

QBOIndian sub-continent has three marked rainy seasons: Southwest Monsoon, Northeast Monsoon and Winter rains. Lots of studies have been done and indicators worked out towards likely performance of Southwest Monsoon and winter rains. However, Northeast Monsoon remains a less rehearsed and researched subject. The period October to December is referred to as Northeast Monsoon season over peninsular India.

Northeast monsoon season is the major period of rainfall activity, particularly in the eastern half of peninsula comprising of the meteorological sub- divisions of Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu- Puducherry. For Tamil Nadu, this is the main rainy season accounting for about 48% of the annual rainfall. Coastal districts of the state get nearly 60% of the annual rainfall and the interior areas of the state get about 40-50% of it.

The increase in rainfall activity along South Andhra Pradesh and Tamil Nadu coast, which takes place sometime in the first half of October, has generally been considered as the setting of Northeast Monsoon

Like the El-Nino, ENSO, MJO etc. are linked with the performance of Southwest Monsoon over the Indian region, QBO(Quasi Biennial Oscillation) has a teleconnection with the Northeast Monsoon rainfall. QBO is a periodic oscillation of equatorial zonal winds between easterlies and westerlies in the tropical stratosphere. Few other noticeable features of this phenomenon are:

  • The average period for change from westerlies to easterlies and vice-versa varies between 25 to 29 months.
  • Easterlies are generally stronger( 30-35m/s) than westerlies (15-20m/s)
  • The amplitude of easterly phase is about twice as strong as that of westerly phase
  • Both, period and amplitude, vary considerably from cycle to cycle
  • Maximum amplitude of both phases typically occur near 20 hPa(20-25km)
  • Waves responsible for this effect remain debatable
  • Probably, Gravity Waves are the major cause/contributor

Some of the effects of QBO are:

  • Responsible for rainfall variation in several regions of the globe
  • Modification of NE monsoon precipitation in India
  • Strength of Jet Stream
  • Severity of winters in the Northern Europe and Eastern USA

Some of the features of QBO with respect to Northeast Monsoon are:

  • Northeast Monsoon is basically a lower tropospheric phenomenon
  • QBO is a lower stratospheric phenomenon
  • Probability of excess rainfall during easterly phase is only 23%
  • Probability of deficit rainfall during westerly phase is only 10%
  • During westerly phase, the probability of NE Monsoon being normal is 55% and its being normal/excess is 90%
  • During easterly phase, the probability of NE Monsoon being normal/excess is 36%

We may infer that probability of NE Monsoon being deficient during the westerly phase and excess during easterly phase is low. The westerly phase of QBO has concluded three months back and it has entered the easterly phase now. We may also conclude that no single factor can sway a large scale phenomenon like monsoon and therefore keep our fingers crossed for a reasonable rainfall during the Northeast Monsoon.

Rajasthan reeling under second summer

rajIf you have been considering a visit to famous Havelis in Jaisalmer and Bikaner during the day time, then you might want to reconsider and instead take up thrilling desert safari or overnight camping!

With the southwest monsoon withdrawing from north India, reversal of temperature and change in weather is resulting in short second summer in many parts of Rajasthan.

Withdrawal of monsoon means rise in temperature, reversal of wind pattern and variation in humidity levels. On account of these parameters, places such as Jaisalmer, Bikaner and Barmer in Rajasthan are witnessing second summer.

For instance, while Jaisalmer was witnessing a maximum temperature of 36°C and minimum of 26⁰C, after withdrawal the maximums have risen to 38⁰C and minimums are 22⁰C. The pattern is similar for Bikaner that is observing rise in day temperature and drop in minimums.

Humidity levels are varying hugely with a drop of almost 20% in most of these parts. In Bikaner where humidity has been at 80%, the levels have come down to 50% after withdrawal of southwest monsoon.

According to Skymet Meteorology Division in India, due to hot, sunny days and cloudless sky, the day temperature will remain high but early mornings and evenings will be cooler in the upcoming days.

Comparison of temperature

City

Max/Min. temp before Monsoon

Max/Min. temp after Monsoon

Jaisalmer

36/26⁰C

36/22⁰C

Bikaner

34/26⁰C

37/23⁰C

Barmer

34/27⁰C

36/25⁰C

 

 

Mars versus other planets

mars and other planetsOn September 24, India created history as India's first Mars mission made its successful entry into the orbit of Mars planet in an epic moment for Indian Space Research Organization (ISRO). Few days back on September 21, NASA's MAVEN spacecraft had also successfully entered Mars' orbit, where it  will now prepare to study the Red Planet's upper atmosphere.

With this, India joins a small group of nations - United States, Russia and Europe - that have successfully sent probes to orbit or land on Mars. Others, however, failed several times initially.  Let us have a look why Mars is the favourite planet for the space scientists across the world.

There are eight planets in our Solar System--Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Each planet has their characteristics and they can be further divided into two parameters- terrestrials and gas and ice giants.

Terrestrials: Planets that are similar to Earth, with bodies largely composed of rock are Mercury, Venus, Earth and Mars.

  • Mercury is the smallest terrestrial and smallest planet in the Solar System. It is also closest to sun, making is too hot and thus it is not even possible to think of visiting this planet.
  • Venus is also called as Earth's "sister planet", due to its similar size, gravity, and bulk composition. It is closest planet to the Earth, but it is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. Venus is by far the hottest planet in the Solar System. It has no carbon cycle to lock carbon back into rocks and surface features, nor does it seem to have any organic life to absorb carbon in biomass.

Gas and Ice giants: This includes Jupiter, Saturn, Uranus and Neptune. These planets are largely composed of gaseous material and significantly more massive than terrestrials.

  • Jupiter is the planet from the sun and is the largest planet in the Solar System. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium. It may also have a rocky core of heavier elements, but it lacks a well-defined solid surface.
  • Saturn is the second largest planet and wind speeds on Saturn can reach 1,800 km/h

Ice giants: This category comprises of Uranus and Neptune and is a sub-class of gas giants. They have significantly lower mass, and are also depleted in hydrogen and helium in their atmospheres together with a significantly higher proportion of rock and ice. Both the planets are too cold to be explored for the chances of life.

Mars have certain factors that make it the most vulnerable planet to be explored by the space scientists.  Following are the few reasons:

  • Mars is at the ideal distance from the Earth, as it is neither too close nor too far
  • Earth is tilted at 23.5 degrees, while Mars is also tilted at 25.2 degrees
  • Length of the day is almost same with 24:39:35 against 2400 hours on the Earth
  • Temperature are also expected to hover between -100°C and 27°C
  • It is believed that Mars possesses several gasses that are similar to the Earth. Some are Carbon Dioxide, Argon, Methane. Traces of Oxygen are also expected on the planet
  • Weather is likely to be similar to the Earth, in terms of extreme cold. However, Mars is much colder than the Earth
  • Signs of frozen water have also been found

 

 

Low pressure brewing in Comorin region, likely to strengthen

Skymet sattelite mapThe Northeast Monsoon season gets manifested by formation of cyclonic systems in the southern latitudes of the Arabian Sea and Bay of Bengal. Presently there is a cyclonic circulation brewing in the India Ocean near Comorin region, which is showing signs of developing in the next 3-4 days into a low pressure area.

Climatological records show that these systems forming over these regions have a tendency to strengthen and move west-northwestwards, away from the Indian coast and head for Yemen/Oman. Such systems set pace for more cyclones to form.

If this system develops into a Cyclonic storm then it will be the first of the season. But we need to wait for 3-4 days before saying anything. However, the system is not going to impact coastal India in any way .

During summer equinox, equatorial region of the India Ocean becomes very active with a series of weather disturbances. At the moment there are some weather disturbances on the either side of the equator in close proximity and the conditions are favourable for these systems to strengthen, provided they gain latitudes.

Why scientists exploring Mars?

Mars MissionIndia triumphed in its maiden Mars Mission as its spacecraft 'Magalyaan' successfully reached the red planet on its very first attempt on Wednesday, elevating country's position at par with elite nations in the global space race. With this, India joins a small group of nations - United States, Russia and Europe - that have successfully sent probes to orbit or land on Mars. Others, however, failed several times initially.

Indian Space Research Organisation’s (ISRO) low-cost mission crowned India as the first country to execute such a project in its first attempt. The Mangalyaan aims to study Mars' surface and mineral composition, and scan its atmosphere for methane, a chemical strongly tied to life on Earth. It cost roughly a tenth of NASA's Mars mission Maven that successfully entered Mars orbit on September 21.

Why Mars?

Mars is supposed to be the best choice for exploration among all the eight planets of our Solar System, as it is similar to the Earth in several manners. Now let us have a look at why the space scientists around the world are only dodging the Mars:

  • Mars is at the ideal distance from the Earth, as it is neither too close nor too far
  • Earth is tilted at 23.5 degrees, while Mars is also tilted at 25.2 degrees
  • Length of the day is almost same with 24:39:35 against 2400 hours on Earth
  • Temperatures are also expected to hover between -100°C and 27°C
  • It is believed that Mars possesses several gasses that are similar to the Earth. Some are Carbon Dioxide, Argon and Methane. Traces of Oxygen are also expected on the planet
  • Weather is likely to be similar to the Earth, in terms of extreme cold. However, Mars is much colder than the Earth
  • Signs of frozen water have also been found

The state-run ISRO successfully ignited the main 440 Newton liquid engine and eight small thrusters that fired for 24-minutes and trimmed the speed of the craft to allow smooth orbit insertion under Mars' shadow.

Indian scientists had successfully tested the main engine of the spacecraft bound for Mars on September 22 and performed a course correction that had put the low-cost project on track to enter the red planet's orbit. It was launched in November last year.

 

Major parts of the country become dry

DROUGHTDry weather conditions are prevailing in the entire country, barring the Northeast region where heavy rains have caused floodings in Assam and Meghalaya. Worst affected regions are Northwest and Central India.

In the last 48 hours, the rainfall deficit in Northwest India is 100% on a daily basis. East Uttar Pradesh is the only region where the deficit is a shade better at 67%. Similar conditions prevail in Central India. Gujarat, Madhya Pradesh Konkan and Goa are 100% deficit, while rest of the areas are 70% deficit on a daily basis.

The southern peninsular is also largely scanty with deficit being close to 100%. Tamil Nadu and Puducherry are the only regions that are marginally better at 70%.

Rainfall in the last 48 hours has been confined to Northeast India only, creating havoc in the states of Assam and Meghalaya. However, the weather in the region is likely to improve in the next 48 hours as the intensity of rain will decrease and become very light.

The country rainfall deficit had recently shot up to 12% but some very good rain in the northeast region over the last 3-4 days pulled it back to 11%. In the remaining days of September the average rainfall is going to be below normal. This will push up the country rainfall deficit by decimal points on a daily basis. Weathermen at Skymet believe that the cumulative deficit is likely to stay close to 11% but stand a chance to touch 12%.

Picture courtesy: thehindu.com







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