Climatology

Statement 1 is incorrect. In Ensemble Forecasting, instead of running just a single forecast, the computer model is run a number of times from slightly different starting conditions. The complete set of forecasts is referred to as the ensemble, and individual forecasts within it as ensemble members.
Statement 2 is correct. Various countries have migrated to ensemble weather forecasting for optimal results. A forecast is an estimate of the future state of the atmosphere. It is created by estimating the current state of the atmosphere using observations, and then calculating how this state will evolve in time using a numerical weather prediction computer model.
The ensemble forecasts give the forecaster a much better idea of what weather events may occur at a particular time. By comparing these different forecasts, the forecaster can decide how likely a particular weather event will be.

Statement 1 is incorrect. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure. As the storm system rotates faster and faster, an eye forms in the center. It is very calm and clear in the eye, with very low air pressure. Higher pressure air from above flows down into the eye.
Statement 2 is correct. The warm, moist air over the ocean rises upward from near the surface. Tropical cyclones usually weaken when they hit land, because they are no longer being “fed” by the energy from the warm ocean waters. However, they often move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely.

Statement 1 is correct. LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30years, 50-years etc.
Current LPA of all India south west monsoon rainfall based on the average rainfall over the period 1961 -2010 is 880.6mm.
Statement 2 is incorrect. India Meteorological Department (IMD) has revised the normal onset and withdrawal dates based on recent data. The normal dates of onset are revised based on data during 1961-2019 and normal dates of withdrawal are revised based on data during 1971-2019.
Monsoon onset over Kerala remains the same, i.e., 1 June. However, new monsoon advance dates over the states like Maharashtra, Gujarat, Madhya Pradesh, Chattisgarh, Telegana, Andhra Pradesh, Odisha, Jharkhand, Bihar and parts of Uttar Pradesh are delayed by 3-7 days compared to existing normal dates. However, over extreme northwest India, the monsoon arrives now little earlier, on 8th July compared to the existing date of 15th July. There are however appreciable changes in the monsoon withdrawal dates, especially over Northwest and Central India. Monsoon withdraws from NW India almost 7-14 days later from the existing dates. There is no change in the final withdrawal date over south India, i.e., 15th October.

Statement 1 is incorrect. The term El Niño refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific.
La Nina episodes represent periods of below-average sea surface temperatures across the east-central Equatorial Pacific. Global climate La Niña impacts tend to be opposite those of El Niño impacts. In the tropics, ocean temperature variations in La Niña also tend to be opposite those of El Niño.
Statement 2 is correct. La Nina results in heavy or better monsoon rains in India, droughts in Peru and Ecuador, heavy floods in Australia, and high temperatures in the Indian Ocean and Western Pacific.
# According to the World Meteorological Organization (WMO), the La Nina weather phenomenon is back in the central and eastern equatorial Pacific Ocean after nearly a decade’s absence.

Typhoon Vamco is currently an active Category 1-equivalent typhoon in northwest Pacific region around Philippines. Vamco originated as a tropical depression northwest of Palau, where it slowly continued its northwest track.
The storm was given the name Vamco by the Japanese Meteorological Agency, but is referred to as Ulysses in the Philippines.

Statement 1 is correct. The Indian southwest monsoon (SWM) season of June to September is the chief rainy season for India and about 75% of the country’s annual rainfall is realized during this season.
Subsequent to the withdrawal of SWM, the northeast monsoon (NEM), a small-scale monsoon confined to parts of southern peninsular India occurs.
Statement 2 is incorrect. The rainfall from the NEM is mostly confines to Tamil Nadu, Puducherry & Karaikal, Kerala & Mahe, Coastal Andhra Pradesh, Rayalaseema and South Interior Karnataka regions.
The northeast monsoon derives its name from the direction in which it travels – from the northeast to the southwest. The normal date of setting in of easterlies over the southeastern peninsular India is 14th October.

Option 1 is incorrectly matched. Super Cyclonic Storm Amphan was a powerful and catastrophic tropical cyclone in Bay of Bengal that caused widespread damage in Eastern India, specifically West Bengal, and also Bangladesh in May 2020.
Option 2 is correctly matched. The India Meteorological Department (IMD) has forecast the development of a cyclone in the Southwest region of the Bay of Bengal, off Tamil Nadu coast.
The Met department has said that it will strengthen into a cyclone. Once intensified, it would acquire its name ‘Nivar’, proposed by Iran.

There are six regional specialised meteorological centres (RSMCs) and five regional Tropical Cyclone Warning Centres (TCWCs) across the globe to monitor cyclogenesis, issue advisories and name cyclones.
IMD’s RSMC in New Delhi is one among them that provide advisories to 13 countries in the north Indian Ocean basin: Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, United Arab Emirates and Yemen. RSMC, New Delhi is also responsible for naming cyclones over the Bay of Bengal and the Arabian Sea.
In 2020, a new list of cyclone names was issued by IMD, following WMO guidelines. The new list comprises 13 names of cyclones each for the 13 member countries, totalling to 169. The names for India include Gati, Tej, Murasu, Aag, Vyom, Jhar, Probaho, Neer, Prabhanjan, Ghurni, Ambud, Jaladhi and Vega.
Cyclone Nivar’s name is among the names submitted by Iran.

Statement 1 is incorrect. 2019 was the 2nd warmest year on record. The past five years have been the hottest five.

Statement 2 is incorrect. About 29 percent of the solar energy that arrives at the top of the atmosphere is reflected back to space by clouds, atmospheric particles, or bright ground surfaces like sea ice and snow. About 23 percent of incoming solar energy is absorbed in the atmosphere by water vapor, dust, and ozone, and 48 percent passes through the atmosphere and is absorbed by the surface. Thus, about 71 percent of the total incoming solar energy is absorbed by the Earth system.
# New Zealand’s government will decide next week if a climate emergency should be declared in the country or not.

The Fujiwhara effect refers to tendency of two nearby tropical cyclones to rotate cyclonically about each other.

When two hurricanes spinning in the same direction pass close enough to each other, they begin an intense movement around their common center. If one hurricane is a lot stronger than the other, the smaller one will orbit it and eventually come crashing into its vortex to be absorbed.

Two storms closer in strength can gravitate towards each other until they reach a common point and merge, or merely spin each other around for a while before shooting off on their own paths. In rare occasions, the effect is additive when the hurricanes come together, resulting in one larger storm instead of two smaller ones.

# Two tropical storms named Marco and Laura forming in the western Atlantic Ocean at nearly the same time are likely to impact the Gulf of Mexico sparking concerns of the rare Fujiwhara effect.

Statement 1 is correct. LPA of rainfall is the rainfall recorded over a particular

region for a given interval (like month or season) average over a long period like 30years,

50-years etc.

Current LPA of all India south west monsoon rainfall based on the average rainfall over the

period 1961 -2010 is 880.6mm.

Statement 2 is incorrect. India Meteorological Department (IMD) has revised the normal

onset and withdrawal dates based on recent data. The normal dates of onset are revised

based on data during 1961-2019 and normal dates of withdrawal are revised based on data

during 1971-2019.

Monsoon onset over Kerala remains the same, i.e., 1 June. However, new monsoon

advance dates over the states like Maharashtra, Gujarat, Madhya Pradesh, Chattisgarh,

Telegana, Andhra Pradesh, Odisha, Jharkhand, Bihar and parts of Uttar Pradesh are

delayed by 3-7 days compared to existing normal dates. However, over extreme northwest

India, the monsoon arrives now little earlier, on 8th July compared to the existing date of

15th July. There are however appreciable changes in the monsoon withdrawal dates,

especially over Northwest and Central India. Monsoon withdraws from NW India almost 7-

14 days later from the existing dates. There is no change in the final withdrawal date

over south India, i.e., 15th October.

Statement 1 is incorrect. Cyclones are characterized by inward spiraling

winds that rotate about a zone of low pressure. As the storm system rotates faster and

faster, an eye forms in the center. It is very calm and clear in the eye, with very low air

pressure. Higher pressure air from above flows down into the eye.

Statement 2 is correct. The warm, moist air over the ocean rises upward from near the

surface. Tropical cyclones usually weaken when they hit land, because they are no longer

being “fed” by the energy from the warm ocean waters. However, they often move far inland,

dumping many inches of rain and causing lots of wind damage before they die out

completely.

Storm Surge.

• Storm surge is the abnormal rise in seawater level during a storm, measured as

the height of the water above the normal predicted astronomical tide.

• The surge is caused primarily by a storm’s winds pushing water onshore.
• The amplitude of the storm surge at any given location depends on the orientation

of the coast line with the storm track;

• The intensity, size, and speed of the storm; and the local bathymetry.

All clouds are made up of basically the same thing: water droplets or ice

crystals that float in the sky.

But all clouds look a little bit different from one another, and sometimes these differences

can help us predict a change in the weather.

• Cirrus clouds are delicate, feathery clouds that are made mostly of ice crystals.

Their wispy shape comes from wind currents which twist and spread the ice crystals

into strands.

• Altocumulus clouds have several patchy white or gray layers, and seem to be made

up of many small rows of fluffy ripples. They are lower than cirrus clouds, but still

quite high. They are made of liquid water, but they don’t often produce rain.

• Cumulus clouds look like fluffy, white cotton balls in the sky. They are beautiful

in sunsets, and their varying sizes and shapes can make them fun to observe!

• Stratocumulus clouds are patchy gray or white clouds that often have a dark

honeycomb-like appearance.

The prefix “nimbo-” or the suffix “-nimbus” are low-level clouds that have their bases below 2,000 meters (6,500 feet) above the Earth.

 Clouds that produce rain and snow fall into this category. (“Nimbus” comes from the Latin word for “rain.”) Two examples are the nimbostratus or cumulonimbus clouds.

 Nimbostratus clouds bring continuous precipitation that can last for many hours. These low-level clouds are full of moisture.

 Cumulonimbus clouds are also called thunderheads. Thunderheads produce rain, thunder, and lightning.

 Many cumulonimbus clouds occur along cold fronts, where cool air is forced under warm air.

 They usually shrink as evening approaches, and moisture in the air evaporates. Cumulonimbus clouds gradually become stratocumulus clouds, which rarely produce rain.

The Roaring Forties take shape as warm air near the equator rises and moves toward the poles.

 Warm air moving pole-ward (on both sides of the equator) is the result of nature trying to reduce the temperature difference between the equator and at the poles created by uneven heating from the sun.

 This process sets up global circulation cells, which are mainly responsible for global-scale wind patterns.

 The air descends back to Earth’s surface at about 30 degrees’ latitude north and south of the equator. This is known as the high-pressure subtropical ridge, also known as the horse latitudes.

 Here, as the temperature gradient decreases, air is deflected toward the poles by the Earth’s rotation, causing strong westerly and prevailing winds at approximately 40 degrees. These winds are the Roaring Forties.

 The Roaring Forties in the Northern Hemisphere don’t pack the same punch that they do in the Southern Hemisphere.

 This is because the large land masses of North America, Europe, and Asia obstructing the airstream, whereas, in the southern hemisphere, there is less land to break the wind in South America, Australia, and New Zealand.

 While the Roaring Forties may be fierce, 10 degrees south are even stronger gale-force winds called the Furious Fifties.

 And 10 degrees south of the Furious Fifties lay the Screaming Sixties! We can thank the intrepid sailors of yore for these wildly descriptive terms

The hot deserts lie astride the Horse Latitudes or the sub-tropical high pressure belts where the air is descending, a condition is least favourable for precipitation of any kind to take place.

The periodical rise and fall of the sea level, once or twice a day, mainly due to the attraction of the sun and the moon, is called a tide.

Movement of water caused by meteorological effects (winds and atmospheric pressure changes) is called surges. Surges are not regular like tides.

The term monsoon has been derived from the Arabic word mausin or from the Malayan word monsin meaning ‘season’.

Monsoons are seasonal winds (Rhythmic wind movements – Periodic Winds) which reverse their direction with the change of season.

Factors affecting monsoon in India–

 The differential heating of the landmass of Asia and the Indian Ocean.

 The existence of the Himalayan ranges and the Tibetan Plateau.

 The occurrence of heavy-light snow over the Tibetan Plateau

• The existence and circulation of the upper air jet stream in the troposphere.

 Changes in the equatorial Atlantic Ocean have been known to have an inverse relationship with the Indian summer monsoon rainfall. This means if there is a cold phase in the Atlantic, it can bring more rainfall to India and vice versa.

The effects of climate change are at our doorsteps.

 Cyclones such as Thane, Vardah, Ockhi and Gaja have affected Tamil Nadu in recent times;

 Chennai saw terrible floods in 2015.

• Floods wreaked havoc in Assam, Himachal Pradesh and Bihar this year, and Mumbai received record monsoon rains.

 Kerala witnessed floods for the second consecutive year.

 Cyclone Fani devastated Odisha, Cyclone Vayu ravaged Gujarat this year. All these are because of climate change.