What is the importance of wet-bulb temperatures in a warming world?

The summer is here and the heat is upon us. Much of India experiences hot weather, exposing over a billion people to tough conditions. While you might be tracking the daily temperatures of your region that can be seen in weather forecasts, that might not be a fair reflection of the conditions.

The temperatures we see in weather forecasts are called air temperatures, also referred to as dry-bulb temperatures by meteorologists. Humidity, which plays a big role in how we experience heat, is not factored into air temperatures.

What is wet-bulb temperature?

Wet-bulb temperatures, on the other hand, combine the dry air temperature that we can see on a thermometer with humidity. It is for this reason that wet-bulb temperatures are a better measure of heat-stress conditions on humans in direct sunlight.

The name is a reflection of how this temperature is measured. When a wet cloth is slid over the bulb of a thermometer, the thermometer cools down due to water evaporating from the cloth. This lower temperature is the wet-bulb temperature and cannot go above air temperature.

The evaporating water cooling down the thermometer is akin to how our hodu temperature is lowered when we sweat. The sweating helps, however, only when the humidity in the surrounding air is low.

Sweating and humidity

If the humidity is high then it means that the air is already more saturated with water. As a result, less evaporation will occur and the wet-bulb temperature will be closer to the dry temperature. In such a scenario where the humidity is very high, sweating might not cool you as the sweat needs to evaporate off our skin for cooling to occur.

While it was long believed that a wet-bulb temperature of 35 degree Celsius was the maximum a human could endure for extended durations, a study in ?0?? suggested that it could he much lower - around 31 degree Celsius. With the world's temperatures fast rising, extreme weather events, including heatwaves, are being encountered far more often in a warming world.

When the wet-bulb temperature in your region is high, it is important to take good care of yourself. If you are forced to be outside for a considerable length of time, then it is recommended that you wear a hat and lightweight, loose-fitting, light-coloured clothes. It goes without saying that you should try to take frequent breaks in areas with shade and keep yourself hydrated by taking plenty of fluids.

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When strong winds storm across sandy deserts, they lift huge amounts of sand into the air and blow it about forcefully in what is called a sandstorm. The force and speed of the wind can carry the sand for thousands of kilometres before depositing it again. The coarseness of the particles can make a sandstorm really devastating. Smaller grains can remain suspended in the air for a long time.

A sandstorm is described as a natural phenomenon that occurs when a strong wind, such as a gust front, blows fine sand particles and dust from a dry surface. These particles become suspended in the air, causing erosion where they initially were. The wind drops these particles in another place where silt is formed.

Also known as a dust storm, a sandstorm is common in arid and semi-arid regions. The primary terrestrial sources of airborne dust include the drylands around the Arabian Peninsula and North Africa. The Takla Makan and Gobi desert of China, and the Sahara desert also experience sandstorms.

A sandstorm is usually confined to the lowest ten feet. It rarely rises to more than fifty feet above the ground. The sand particles which are picked up by the sandstorm are larger than dust particles. They usually fall out of the storm more rapidly, causing it to launch not far from where the sand was initially at.

It is thought that the particles also fall to the ocean, significantly affecting the marine ecosystem. It is worth noting that the frequency of sandstorms has been increasing, albeit a well-known meteorological phenomenon since the ancient times. It has raised several health and environmental concerns due to the gravity of its surge.

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Rounded or mound-shaped hills created by glacial ice, drumlins are often found in clusters. They are largely made up of sediment deposited by a glacier and can vary greatly in size. The name derives from a Gaelic word droimin meaning ‘smallest ridges’.

Drumlin's meaning is quite simple. Drumlins are elongated, oval-shaped or say teardrop-hills of rock, sand, and gravel. A drumlin is by and large made up of glacial drift, formed underneath an ice sheet or moving glacier and oriented in the direction of ice flow. There are no strict specifications with respect to the size of a drumlin but they tend to be up to a few kilometers up to 2 kilometers long and up to 50m in relief.

Drumlin glacier develops in the form of clusters apparently close to the terminus of glaciers. The mechanisms of formation are though disputed. They seemingly have significant interpretive value for rate and direction of glacial movement.

Drumlins are usually found in wide-ranging lowland regions, with their long axes approximately parallel to the path of glacial flow. Though they are observed in a multitude of shapes, the glacier side is always steep and high, while the lee side is tapered and smooth mildly in the direction of ice movement. Drumlins can hugely differ in size, with lengths from 1 to 2 km, heights from 50 to 100 feet, and widths from 400 to 600 m.

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Sometimes a stream cuts a channel under a slow-moving glacier, creating a long, winding ridge of sand and gravel that is called an esker. Before the glacier melted, the banks of these streams were defined by glacier ice. The deposited gravel now stands high above the surrounding land.

An esker is an attractive landform formed through fluvioglacial deposition. It is a winding ridge of low-lying stratified sand or gravel dominating the terrain and providing the vintage point and dry routes. An esker occurs in a glaciated area or a formerly glaciated region, especially in Europe and North America. The esker lies on valley floor within the ice margins marked by a moraine system suggesting that the eskers are formed beneath the glacier. The word esker is an Irish word meaning a ridge or an elevation which separates two plains. The term is also used to refer to ridges which are deposits of fluvioglacial material. Eskers vary in size and shapes with most of them being sinuous. The longest eskers are continuous and measure few kilometers while most of them are short and discontinuous.

Eskers are formed on washed sands and gravel. Most eskers are formed within ice-walled tunnel by streams which flow under and within glaciers. When the ice wall melts away, water deposits remain as winding ridges. Eskers can also be formed above the glacier through the accumulation of sediments in supraglacial channels. Eskers are formed at the terminal zones of glaciers where the ice is flowing relatively slowly. The melt water collects and flows through a network of tunnels. This water carries highly charged with debris which is composed of coarse-grained gravel which are stratified and sorted. The shape and size of the subglacial tunnel are determined by the flow and melting of the ice. The form of the tunnel then determines the shape and structure of an esker.

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Sometimes, the rocks along a coastline have a crevice or hole just above the low-tide mark. When the high tide rushes in, the crevice fills up with water, which tries to escape through this narrow hole. The build-up of pressure sprays out the water as an upward plume with a loud sound. This is a blowhole. Over time, a blowhole can create caves or even a pool of water near the coast.

When sea caves grow towards the land and upwards creating a vertical shaft that exposed on the surface, it results in a blowhole. Water often gushes out at the top part of the landform when waves move to the sea cave with significant force. The activities of the blowhole depend on the sea conditions as well as its geometry and that of the sea cave. A blowhole is characterized by an opening on the ground and a connection to an opening which interacts with the sea, mostly a cave.

Sea Caves are a common feature along the coasts and are formed through mechanical erosion of cliffs. Parts of weakness in the cliffs are weathered out by wave action thereby forming large cavities known as sea caves. These caves are regularly exposed to waves. Hydraulic pressure, built up by a succession of waves, eventually carves out a hole at the top of the cave to create an opening for water pressure to be expelled as a jet of spray. A blowhole can also be formed when lava flows make openings in the ground which extend towards the sea. The landform manifests as a crack or fissure once formed.

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What is a spit?

A spit is a narrow, extended piece of land that develops where a coastline sharply turns in towards the landmass. Attached to the coast at one end, the spit seems to grow out of it, as the movement of waves and tides deposits sand and pebbles at the angle of the landmass. The other end extends out into the sea, growing longer over time as more debris accumulates along it.

Spit is a landform in geography that is created from the deposition of the sand by the tide movements. One end of the spit remains attached to the mainland while the other end is open out in the water. It is narrow and elongated. Also known as sandspit, this type of landform is found off the coasts or the lake shores.

Spits are usually formed when re-entrance takes place by the longshore drift process from longshore currents. When waves at an oblique angle meet the beach, drift occurs. There is a deposit of sediment in a narrow strip in zigzag pattern moving down the beach. The same waves also cause longshore currents that complement the formation of the spit.

At the re-entrance, the longshore current spreads out or dissipates and not being able to carry the full load, drops much of the sediment which is called deposition. The longshore or littoral drift continues to transport sediment with the help of this submerged bar of deposit into the open waters alongside the beach in the direction the waves are breaking

This process forms an above-water spit. The formation of spit will continue out into the sea until the water pressure obstructs in the deposition of sand. As it grows, it becomes stable and often fertile; vegetation starts to grow and supports habitation.

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There have been at least five major ice ages in Earth’s history: the Huronian,  Cryogenian, Andean-Saharan, late Palaeozoic and Quaternary. The study of rocks dates the Huronian around 2.1 billion years ago. The Cryogenic, around 700 million   years ago may have seen Earth almost totally frozen, like a snowball. The Andean-Saharan Ice Age happened around 400 million years ago. The late Palaeozoic, around 360 million years ago, had extensive polar ice caps. The Quaternary Age began around

2.5 million years ago. At present, Earth is in an interglacial period it is between ice ages.

There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation, in progress since 2.58 million years ago.

Within ice ages, there exist periods of more severe glacial conditions and more temperate conditions, referred to as glacial periods and interglacial periods, respectively. The Earth is currently in such an interglacial period of the Quaternary glaciation, with the last glacial period of the Quaternary having ended approximately 11,700 years ago. The current interglacial is known as the Holocene epoch. Based on climate proxies, paleoclimatologists study the different climate states originating from glaciation.       

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The rotation and revolution of Earth, the amount of solar radiation and the amount of carbon dioxide in the atmosphere are all factors that contribute to a warming up of Earth, which ends an ice age. Changes in ocean currents also have a major effect on temperatures on Earth.

Over thousands of years, the amount of sunshine reaching Earth changes by quite a lot, particularly in the northern latitudes, the area near and around the North Pole. When less sunlight reaches the northern latitudes, temperatures drop and more water freezes into ice, starting an ice age. When more sunlight reaches the northern latitudes, temperatures rise, ice sheets melt, and the ice age ends.

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In today’s world, the ice sheets of Antarctica and Greenland. An ice sheet is a continuous mass of ice covering more than 50,000 km2. The ice sheet in Antarctica covers 14 million km2. It is 1.6 to 6.4 km thick and holds 30 million km2 of ice. The Greenland ice sheet covers about 1.7 million km2.

The Antarctic ice sheet is the largest block of ice on Earth. It covers more than 14 million square kilometers (5.4 million square miles) and contains about 30 million cubic kilometers (7.2 million cubic miles) of water.

The Antarctic ice sheet is about 2 kilometers (1.2 miles) thick. If it melted, sea level would rise by about 60 meters (200 feet).

The Greenland ice sheet is much smaller than the Antarctic Ice sheet, only about 1.7 million square kilometers (656,000 square miles). It is still the second-largest body of ice on the planet.

The Greenland ice sheet interacts much more dynamically with the ocean than the Antarctic ice sheet. The annual snow accumulation rate is more than double that of Antarctica. Glacial melt happens across about half of the Greenland ice sheet, whereas it is much more isolated on the far western part of Antarctica. Greenland's ice shelves break up much faster than those surrounding Antarctica.

Both the Antarctic and Greenland ice sheets have caused the land under them to sink. Eastern Antarctica is about 2.5 kilometers (1.6 miles) below sea level because of the colossal weight of the ice sheet above it.

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A desert is defined by the amount of precipitation (rain, snow, mist and fog) in an area. A region that receives very little precipitation is classified as a desert. There are many types of deserts, including subtropical, coastal and polar deserts. What they all have in common is a barren, windswept landscape, which makes it difficult for plants and animals alike to gain a foothold on land. This all certainly applies to Antarctica.

The average yearly rainfall at the South Pole over the past 30 years was a tiny 10 mm (0.4 in). Most of the continent is covered by ice fields carved by the wind, and craggy mountains covered in glaciers. While Antarctica is home to wonderful forests of low-lying mosses and lichens, there are only two flowering plants that can survive the harsh conditions. And most of the animals we encounter – penguins, seals, whales and seabirds – rely on seafood for sustenance.

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The Antarctic ice cap contains about 91% of all the ice in the world and about 86% of all freshwater that occurs in the form of ice. But despite all this freshwater, Antarctica is considered one of the most arid places on Earth.

Antarctica is the highest, coldest, driest, and windiest of the world’s continents. It is also “tallest” in terms of average height above sea level. Nearly 99% of this land mass is covered with an ice cap with an average altitude of around 2 200 metres above sea level. The area of this vast continent – some 14 million square kilometres – doubles in the winter, when sea ice can stretch as much as 1000 km outwards from the coastline.

Most of the continent of Antarctica lies south of 70°S, although the Antarctic Peninsula stretches northward as far as 60°S. The continent is surrounded by the Southern Ocean, a circumpolar sea that isolates Antarctica from the other continents.

Most of Antarctica is covered with ice, but in many places mountain peaks (nunataks) stick up out of the ice. The Vinson Massif in West Antarctica, with an elevation of 5 140 m, is the highest peak in Antarctica. In addition to the nunataks, there are large ice-free regions called oases where the ice has retreated and where melting outstrips accumulation of new snow. Other areas, known as dry valleys, are free of ice because essentially no precipitation falls there.

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When the movement of waves deposits gravel and sand in a manner that prevents access to a bay, it builds up a baymouth bar. The existence of the bar creates a shallow lake known as a lagoon that is separated from the sea by a beach.

A baymouth bar is a depositional feature as a result of longshore drift. It is a spit that completely closes access to a bay, thus sealing it off from the main body of water. These bars usually consist of accumulated gravel and sand carried by the current of longshore drift and deposited at a less turbulent part of the current. Thus, they most commonly occur across artificial bay and river entrances due to the loss of kinetic energy in the current after wave refraction.

In most cases, a Sand Bypass System is built to prevent these bars forming across the entrance of man-made seaway's, eliminating the danger posed to commercial and recreational boat owners passing through.

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Man-made, shore protection measures to reduce erosion. Constructed of wood or stone, groynes control the movement of water rushing onto the beach and prevent sand from being swept away by the waves. A number of groynes usually run perpendicular to the shore and extend up to the sea.

A groyne is a rigid hydraulic structure built perpendicularly from an ocean shore (in coastal engineering) or a river bank, interrupting water flow and limiting the movement of sediment. It is usually made out of wood, concrete, or stone. In the ocean, groynes create beaches, prevent beach erosion caused by longshore drift where this is the dominant process and facilitate beach nourishment. There is also often cross-shore movement which if longer than the groyne will limit its effectiveness. In a river, groynes slow down the process of erosion and prevent ice-jamming, which in turn aids navigation.

Groynes run generally perpendicular to the shore, extending from the upper foreshore or beach into the water. All of a groyne may be underwater, in which case it is a submerged groyne. They are often used in tandem with seawalls and other coastal engineering features. Groynes, however, may cause a shoreline to be perceived as unnatural. Groynes are generally straight but could be of various plan view shapes, permeable or impermeable, built from various materials such as wood, sand, stone rubble, or gabion, etc.

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The Kiama Blowhole is a blowhole in the town of Kiama, New South Wales, Australia. The name ‘Kiama’ has long been translated as “where the sea makes a noise”. It is one of the town's major tourist attractions. Under certain sea conditions, the blowhole can spray 50 litres of water up to 25 metres (82 ft) in the air, in quantities that thoroughly drench any bystanders. There is a second, less famous blowhole in Kiama, commonly referred to as the "Little Blowhole" by locals. It is much smaller than the other (called the "Big Blowhole"), but due to its narrow shape, it is more reliable than the Big Blowhole, and in the right conditions can be equally spectacular.

The blowhole attracts 900,000 tourists a year. Kiama Blowhole is just a few metres beyond the coastline. The "little blowhole" is located at the Little Blowhole Reserve, Tingira Crescent, Kiama, 2km south of the main blowhole.

The blowhole was formed from basalt lava flows approximately 260 million years ago and was first discovered by local Aboriginals who named it 'Khanterinte'. The blowhole was first written about by George Bass on 6 December 1797. Bass had captained a crew of six and set out on an open whaleboat to explore the south coast of Australia. He noticed the blowhole after anchoring his boat in a sheltered bay.

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Tombolo, one or more sandbars or spits that connect an island to the mainland. A single tombolo may connect a tied island to the mainland, as at Marblehead, Mass. A double tombolo encloses a lagoon that eventually fills with sediment; fine examples of these occur off the coast of Italy. The shallower waters that occur between an island and the mainland are the loci of such features because sandbars form there.

Adam’s Bridge, which connected Sri Lanka (Ceylon) with India across the 33-mile (53-kilometre) wide Palk Strait, was formerly the world’s largest tombolo. It was destroyed several thousand years ago by a slight change in mean sea level, and only a chain of sandbanks that seriously hinder navigation exists there today.

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