Category: Geography Notes PPT

The study of the formation of rocks is classified as geology. It is basically a science that deals with the study of solid matter such as rock or rock strata. And the rock strata conveys the history of the earth and its life, especially what is recorded in it. This can be categorized into stratum geology. The rock strata meaning can be better understood by studying the stratum that is formed from deposits or piles of layers for many years. Stratum is used when there is a single rock consisting of many (several parallel layers) layers. And the term strata is used as a plural noun for stratum to describe a giant pile of the deposited sediments. 

Rock Strata and Stratification

Rock Strata Meaning- The term ‘rock strata’ is often used by geologists when referring to many rock layers in a generic sense that appears over large areas. The singular form stratum, which is derived from a Latin word that means spread out, can be used for a single layer, but individual rock layers or even rock beds are more commonly referred to using this specific name as a stratum. Now that you have understood the rock strata meaning, let us understand the formation and features. Rock strata are formed via stratification. 

Stratification – A bed or layer of sedimentary rock which is formed by the accumulation or deposition of mineral or organic particles at the Earth’s surface, and is then followed by cementation of the deposits naturally over time that is visually distinguishable from adjacent beds or layers and this layering of such rocks or sediment is called stratification. Stratigraphy can be considered a sub-discipline of geology that involves the study of rock strata. A sequence of sedimentary layers stacked one atop the other is known as a stratigraphic section and though this is the basic layer of foundation its arrangement and sequence can completely vary according to Steno’s law of stratigraphy. Something that is formed in layers is referred to as a stratiform deposit by geologists. And the term stratification planes are referred to the planes of parting, or separation between individual rock layers. 

Features of Stratum from Stratification

• Formed from the igneous rocks on the earth’s surface, sedimentary rocks, from the volcanic lava flows and its fragments deposits.

• The layers vary greatly in shape and thickness ranging from several millimetres to metres.

• The strata can be a lenslike thick body that only extends a few metres.

• The layers can also be very thin sheets that spread up to several kilometres horizontally.

• The layers are horizontally aligned and a few inclinations are seen on the deposition sites.

• The texture of the stratum changes and with time, some coarser particles become finer, colour changes are seen due to change in mineral composition as time passes. 

• The thickness of the rock strata is independent of the time of deposition; an inch or 2.5 centimetres of stratum layer may take longer to form than strata with a 3-metre thickness.

• The prominence and the details of the strata can vary vastly even within the same strata.

• Rock strata are only a feature of strata formed by sedimentary rocks while the volcanic rocks formation can differ in a few ways as it is influenced by gravity, sea, liquid lava flow and wind. 

Variants in Formation of Rock Strata

There are many factors that can influence, interrupt and change the course of rock strata formation and all these variants help are of primary importance when studying to interpret the geological events and transformation that occurred on the Earth. They are:

• Transporting ability of the depositing agent

• Water

• Wind flow direction

• Size and weight of the mineral agents

• The shape of the deposits

• Homogeneity of the sediments that are deposited

Stratigraphy Laws

1. Steno’s laws describe the patterns of rock layers formation of strata. The first law is the superposition law which states that the younger layers or the new deposits sit atop the older layers and this pauses the change of their growth and texture.

2. The second law is the law of original horizontality that states the original deposition of sedimentary rock layers are flat but orientation may change and even can be found to be tilted when they are heavily influenced by variants.

3. The Law of cross-cutting is the third law of stratigraphy which states that there is a disruption in the rock layers formed wherein there is no particular pattern and younger ones overlap with the older layers of deposition.

4. The law of lateral continuity is the fourth law which states that the deposition to form rock layers continues laterally without any opposition till they encounter other solid-body matter and no deposition is possible. 

Uses of Rock Strata 

• To study the stratification of volcanic rocks, especially the layered ones.

• Used to study the preserved movements of the earth’s surface through the deformed surface.

• Through the interpretation of geologic events, one can gain such practical results that can be helpful in tracing the petroleum fields, the location of mineral deposits, and groundwater reservoirs. 

• The branch of geology that deals with stratification are also called biostratigraphy which uses fossils to study the earth ages.

• Fossils are a great way to determine the relative ages of the rocks.

• Fossils interpretation is helpful in correlating the successions of sedimentary rocks within and between depositional basins.

Conclusion

Stratum geology is a great way of understanding the eras gone by and the endurance of the planet earth through various seasonal changes. It is also a great way to predict what is possible ahead if there are repeating patterns of depositing nature. The Grand Canyon is a pandora’s box for studying the rock strata. It is remarkable that the stratification process that preserves so much information about the past earth’s movement still endures and sustains as new movements are also being recorded. And these recordings are extremely helpful to study earth patterns throughout their history since their formation and that can provide interesting details and help find missing pieces in historical studies. 

The ultimate source of heat and energy is the Sun. The divergent heat received from the sun on the different regions on Earth is the utmost reason behind the different climate features. So understanding the pattern of temperature distribution on Earth in different seasons is important for understanding different climatic features such as precipitation, wind system, pressure system, etc.  

In this article, we will discuss the horizontal and vertical distribution of temperatures along with the factors affecting and factors controlling the temperature distribution on Earth. 

Horizontal Distribution of Temperature

The distribution of temperature across latitude over the Earth’s surface is known as the horizontal distribution of temperatures. The horizontal distribution of temperature on Earth is shown by Isotherms. Isotherms are the line joining points that have an equal temperature. When the isotherm map is analyzed, it can be observed that the horizontal distribution of temperature is uneven. 

Following are the Factors Accountable for the Uneven Horizontal Distribution of Temperature is:

• Latitude

• Altitude

• Land And Sea Contrast

• Ocean Currents

• Passage of Air Masses

• Vegetation Cover

Vertical Distribution of Temperature

As we are aware, the temperature in the troposphere decreases with an increase in altitudes but the rate of decrease in the temperature changes according to seasons. The decrease of temperatures is known as the vertical temperature gradient or normal lapse rate which is 1000 times more than the horizontal lapse rate. The decrease of temperature upward in the atmosphere proves the fact that the atmosphere gets heat from the Earth’s surface through the process of conduction, radiation, and convection. Hence, as the distance from the Earth’s surface ( the source of direct heat energy to the atmosphere) increases ( i.e as the altitude increases ), the air temperature decreases.

Factors Affecting Temperature Distribution

Some of the factors affecting the temperature distribution are:

1. Latitude: The temperature of the surface water decreases from the equator towards the poles because the sun rays become more and more inclined and hence the amount of insolation minimizes poleward.

2. Unequal Distribution of Land And Water: The oceans in the northern hemisphere receive more heat because of their contact with the larger extent of land than the equivalent parts in the southern hemisphere.

3. Prevailing Winds: The winds blowing from the land towards the ocean drive surface water away from the coasts resulting in an upwelling, in which deep cold water rises into the surface.

4. Ocean Current: Warm ocean current increases the temperature in cold areas whereas the cold current decreases the temperature in the warm ocean. For example: in a gulf stream, a warmer current increases the temperature of the Eastern coast of North America and the west coast of Europe.

5. Other factors affecting the temperature distribution are local weather conditions like storms and cyclones.

Factors Controlling Temperature Distribution

The factors controlling the temperature distribution on the Earth’s surface are discussed below:

• The latitude of the Place

• The altitude of the Place

• Distance From The Sea

• The presence of warm and cold ocean Currents

• Local Aspects

Global Distribution of Temperature

The global distribution of temperature can be effectively understood by considering the temperature distribution for January and July. The distribution of temperature is usually shown on the map using the isotherms. The isotherms are line joining places of equal temperature. Generally, the effects of latitude are well shown on the map as isotherms are generally parallel to the latitudes. The deviation from this trend is more generally observed in January rather than in July, especially in the northern hemisphere. The land surface is much larger in the northern hemisphere than in the southern hemisphere. Hence, the effects of land masses and ocean currents are well observed.

Temperature Distribution – January

• In January, there is winter in the Northern hemisphere and summers in the southern hemisphere.

• The western margins of continents in January are much higher than the Eastern counterparts as the westerlies can carry high temperatures into the landmasses.

• The temperature gradient is much closer to the Eastern margins of continents. The isotherms observe more steady behavior in the southern hemisphere.

Temperature Distribution – July

• During July, it is winter in the Southern hemisphere and summers in the Northern hemisphere. The isotherm behavior is the opposite of what it was in January.

• The isotherms are generally parallel to the latitudes in July. The equatorial oceans record warmer temperatures more than 27 degrees celsius. More than 30 degrees celsius is noticed over the land in the subtropical continent region of Asia, along the 30 ° N latitude.

Conclusion

notes enable students to be sufficiently prepared for the Geography exam and guarantee that students will score good marks.

Triangulation is the method of calculating a dot’s direction from either end of a fixed baseline, by only measuring angles to the dot, rather than measuring distances explicitly as in the trilateration process. And the point may be set as the third point of a triangle with two known angles and one known side. That being said, Triangulation methods are mostly used for measuring the scale of the earth and the distances between different sites.

History Associated with Triangulation Trigonometry

Current triangulation is used for many applications, including surveys, navigation, metrology, astrometry, binocular vision, missile modelling, and arms guidance.

In the region, triangulation techniques were not appreciably employed in medieval Spain by Arabic astrolabe treaties like that of Ibne Al-Saffar by Roman land surveyors, agrimensores (d. 1035). Triangulation methods for measuring the scale of the earth and the distances between different sites were also used by Abu Rayhan Biruni (d.1048).

Simplified Roman methods then seem to have coexisted with more advanced techniques used by skilled inspectors. But it was seldom to translate these practices into Latin (the geometry textbook, the uncertain Geomatria Auctoris of the eleventh century is a notable exception), and these approaches seem only slowly to have been percolated into the rest of Europe.

The medieval Jacob’s staff, primarily used for measurement angles, dating from about 1300, and the presence of precisely monitored shorelines in the Portolan maps, the earliest of which is dated 1296, can demonstrate increased knowledge and usage of such techniques in Spain.

Theory of Triangulation Trigonometry by Gemma Frisius

In a new version of the best-selling 1524 Cosmographica by Peter Apian, on-site, the cartographer Gemma Frisius suggested the precise use of triangulation to position far-away plazas for maps in his booklet Libellus de Locorumratione in 1533 (booklet for a describing place). The technology distributed through Germany, Austria, and the Netherlands has been very influential. The Scandinavian astronomer Tycho Brahe used the technique to complement the extensive triangulation, in 1579, of the island of Hven, where he was located on his observatory, which produced a property plan for the island in 1584 concerning the main sites on both sides of Øresund.

Theory of Triangulation Trigonometry by Willebrord Snell

The Dutch mathematician’s work, Willebrord Snell, examined the distance from Alkmaar to Breda in 1615 by a total of approximately 116 kilometers (72 miles) using a chain of 33 triangles is based on the current method of the use of triangulation networks. The gap was quickly underestimated by 3.5%. The two villages had been divided by a degree on the meridian so that he could derive a value from his calculation of the earth’s diameter – an achievement praised by his book Eratosthenes batavus, published in 1617. Snell measured how to correct the planar formula to account for the earth’s curvature.

He also demonstrated how the location of the point within a triangle can be resected or calculated using the angels cast between the unknown spots. These may be much more precisely determined than vertical bearings depending on a compass. This led to the fundamental idea to first survey and subsequently locate secondary subsidiary points within a vast primary network of control points.

Principle of Triangulation Trigonometry

Calculation

We have l being the distance from A to B:

l = d/tanα + d/tanβ

Using the trigonometric identities tan α = sin α / cos α and sin(α + β) = sin α cos β + cos α sin β, this is equivalent to:

l = d(cosα/sinα + cosβ/sinβ)

l = d (sin(α+β)/sinαsinβ)

therefore:

d = l (sinαsinβ/sin(α+β))

The distance of the unknown point from any point of observation, the north/south, east/west offsets of the point of observation, and the full coordinates of the point are also simple to calculate.

 

Theodolite

Theodolite, the essential instrument used to calculate horizontal and vertical angles, dates back to Leonard Digges, an English mathematician from the 16th century. It consists, in its present form, of a horizontal and vertical fixed telescope. The levelling is achieved using a spiritual degree, crosshairs in the telescope allow for precise synchronization with the sighted object. The corresponding two measurements, vertical and horizontal, are read while the telescope is precisely calibrated.

The Volcanic eruptions might be a spectacular event to watch but it is really dangerous to encounter one. The volcanic eruptions explode when the lava and the gas are discharged from the volcanic vent. One of the most common consequences of this eruption is the population movements. A large crowd is often forced to flee as the molten lava from the volcano flows. Volcanic eruptions are often caused temporary food shortages and also leads to volcanic ash landslides known as Lahar.

We will know about six basic types of volcanic eruptions which are sure to amaze us. It has different variants and nature which will be worthy to learn. 

Six Types of Volcanic Eruptions 

In the Volcanic landforms, we have learned the classification of volcanoes by their size and shape. While in this section we will also classify the volcanoes by their eruptive habits. To note, the type of volcanic eruption which occurs plays a prior role in the evolving a volcanic landform, which forms a significant link between the eruptive habit and between the volcanic structure. 

Generally speaking, the eruptions can be categorized as being effusive or being explosive. 

The Effusive eruptions involve outpouring of the basaltic magma which has a lower viscosity and gaseous content. Explosive eruptions are generally involved with magma and have more viscosity with higher gaseous content. This magma is often broken down into pyroclastic fragments which are caused by explosive gas expansion at the time of expansion.

Based on the eruption behaviour of the volcano, volcanic activity is generally divided into six major types. The types are:

1. Icelandic

2. Hawaiian

3. Strombolian

4. Vulcanian

5. Pelean

6. Plinian

The Icelandic type is characterized by effusions of molten basaltic lava that flow from long and parallel fissures.  After it is cooled down these outpourings get to build into lava plateaus.

The Hawaiian type of volcano eruption is a lot similar to the Icelandic type. In Hawaiian eruption type, however, the fluid lava which flows from the volcano’s summit and the radial fissures to create the shield volcanoes, are very large and have gentle slopes on them.

Strombolian eruptions, yet another type of eruption which involves moderate bursts of the expanding gases, ejects clots of incandescent lava in the cyclical or moreover by continuous small eruptions. These are known as the “lighthouse of the Mediterranean” as they have small frequent outbursts on the Stromboli Island, located on the northeast coast of Italy.

The Vulcanian eruption type is named after the Vulcano Island, located near Stromboli, this eruption generally involves moderate explosions of the gas laden accompanied with volcanic ash. The mixture forms dark, turbulent eruption clouds which rapidly ascend and thus expand in folded shapes.

Next type, Pelean eruption. This type of eruption is associated with explosive outbursts which also release the pyroclastic flows, a dense mixture of the hot volcanic fragments, and the gas that is described as lava, gas, or other hazardous substances. These eruptions are named after the destructive eruption of Mount Pelée which is located on the Caribbean island in the year 1902. The fluids produced by these volcanic eruptions are heavier than air but are of low viscosity and thus pour down from the valleys and sloped with higher velocity. Thus, causing extreme damage. 

Last on the list is the Plinian type of eruption which is an intensely violent kind of volcanic eruption that is illustrated by the outburst of Mount Vesuvius in Italy. In this type of volcanic eruption, the gases boiling out of the gas-rich magma produces an enormous and nearly continuous jetting blast. 

Fun Fact

1. Some volcanic eruptions are quite explosive while others are spectacular and relatively harmless.

• The reason for this out, there are at least four factors .

• The number of gaseous constituents dissolved in the magma.

• The thickness or the viscosity of the magma coming out.

• Rate of decompression of the magma as it proceeds onto the surface. 

• The number of nucleation sites on which the gases form bubbles. 

2. A volcanic eruption occurs when?

When the hot materials from the Earth’s interior surface are thrown out from a volcano, eruptions take place. Eruptions can explode from the side branches or the top vent of the volcano. Even there are some eruptions that are very terrible and thus throw out huge amounts of rock and volcanic ash which can kill many people.

Earth is the planet in our solar system that has the capability to provide life. The surface of the earth is a zone where three main components of the environment meet, overlap as well as interact. 

There are four major domains of the Earth as follows-  lithosphere, atmosphere, hydrosphere, and the biosphere. The atmosphere is further divided into four layers based on composition, temperature, and other properties that are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. 

There are Two Main Divisions of the Surface of the Earth

1. Continents: Continents are large landmasses.

The Highest Mountain Peak on this planet is Mount Everest. 

2. Ocean Basins: Oceans are huge water bodies.

Mariana Trench is the deepest Oceanic trench on this Earth which derives its name from the nearby Mariana Islands.

The Four Major Domains of the Earth

The four major domains of the earth interact with each other as well as affect each other in some way or the other.

Lithosphere: The solid portion of this planet is called the Lithosphere. 

Atmosphere: The gaseous layers that surround the earth are called the atmosphere.

Hydrosphere: Water covers a very big area of the earth’s surface that is called the Hydrosphere.

Biosphere: Biosphere is the zone where land, water, and air together are found.

1. Lithosphere – The Domain of Land

The very outermost portion of the Earth which consists of the Upper Mantle and also the Crust of the Earth is known as the Lithosphere.

Lithosphere has very rigid mechanical properties. The uppermost part of the lithosphere is called the pedosphere. The tectonic plates are a subdivision of the Lithosphere. The major changes in these tectonic plates had created a total of seven continents on the planet earth. These continents are – Asia, America, Europe, Africa, Antarctica and Australia. Asia is the largest continent and the smallest continent is Australia.

2. Hydrosphere – The Domain of Water

The domain of water is called the hydrosphere. It comprises different sources of water and also various types of water bodies like rivers, lakes, seas, oceans, etc. Water is very essential for all living organisms in the world. 

The hydrosphere comprises water on earth in Oceans, Seas, Rivers, Lakes, and even in frozen forms where 2.5% is freshwater and in this 2.5%; approximately 69% is in snow and ice form. The other 97.5% of Earth’s water is salt water and 71% of the surface of the Earth is covered by oceans. Earth got a total of seven oceans namely – the Arctic, North Atlantic, South Atlantic, North Pacific, South Pacific, Indian, and Southern oceans

3. Atmosphere – The Domain of Air

The atmosphere is divided into five layers and they are:

1. Troposphere (0 – 12 km): It is the lowermost layer of the earth’s atmosphere, and extends to an average of 12 km from the surface of the earth. Nearly all the water vapour and moisture found in the atmosphere lie in this section – the “troposphere”.

2. Stratosphere (12 – 50 km): It is the second-lowest section of the atmosphere, just after the troposphere, and is separated by the troposphere via the tropopause. The ozone layer of the earth is also included in this layer, the Ozone layer is filled with a high concentration of Ozone gas.

3. Mesosphere (50 – 85 km): Mesosphere is in the middle of the other atmospheric layers. In the mesosphere, the temperature dropped down by the increase in the altitude, this trend will then be followed by all the layers above it. It can be said to be one of the coldest places on the planet earth, with a temperature of – 85 °C (- 120 °F; 190 K). 

4. Thermosphere (80 km to 500 – 1000 km): This layer is the second-highest in the five atmospheric layers. It expands from the mesopause (which separates it from the mesosphere) all the way above to the thermopause (which cuts it from the exosphere). This is sometimes referred to as the exobase, as it lies just under the exosphere.

5. Exosphere (700 km to ~10,000 km): It is the outermost layer of the earth. It extends to 10,000 km outside the earth’s surface, after that it disappears in the solar wind. The main composition of this layer consists of extremely low densities of hydrogen and helium, some other molecules like traces of Nitrogen gas are also present in this layer.

About 99 per cent of the atmosphere is composed of nitrogen and oxygen where Nitrogen is 78 percent, oxygen is 21 per cent, and other gases comprise 1 per cent.

4. Biosphere – The Domain of Life

The biosphere is the zone of contact between land, water, and air. It is the zone where life exists and that is what makes this planet unique.

The organisms in the biosphere are divided into:

1. Plant kingdom

2. Animal kingdom

Before we discuss “What is Absolute Humidity?”, let’s learn about water vapour and Humidity. Water vapour is a highly variable element of the atmosphere that plays an important role in the hydrologic cycle. High rates of evaporation of water from the earth’s surface keeps the lower atmosphere almost constantly saturated in wet, humid tropical rain forests. In dry, hot deserts, there is typically no water to evaporate, and the amount of water vapour in the atmosphere is almost non-existent. Water vapour in the atmosphere is described by several parameters, including vapour pressure, relative humidity, dew point temperature, water vapour density, and Absolute Humidity. The most familiar is possibly relative humidity.

Humidity

The Earth’s atmosphere is made up of gases kept together by gravity. It protects the Earth and all living things from the sun’s rays. It is made up of different layers with various pressure, thickness, density, and mass. Changes in the atmosphere can cause variations in the atmosphere’s conditions, which can have a significant impact on the Earth and its inhabitants. Humidity is one of the factors that can affect these changes in the air.

The concentration of water vapour in the air is referred to as humidity. Water vapour, or water in its gaseous state, is normally transparent to the naked eye. Humidity suggests the possibility of snow, dew, or fog. Humidity is affected by the temperature and pressure of the device under consideration. Cold air has more humidity than warm air because it contains the same amount of water vapour. The dew point is a related parameter. When the temperature rises, the amount of water vapour needed to achieve saturation rises as well. As a parcel of air’s temperature falls, it will gradually achieve saturation without adding or losing water mass. The amount of water vapour within a parcel of air can vary significantly. 

Humidity is commonly measured using three methods: absolute, relative, and specific.

Absolute Humidity Definition

Let’s define absolute humidity, it is the mass of water vapour divided by the mass of dry air in a certain volume of air at a specific temperature. The warmer the air is, the more water it can absorb. Absolute humidity is the measure of water vapour or moisture in the air, regardless of temperature. It is expressed as grams of moisture per cubic meter of air (g/m3).

Absolute and Relative Humidity

The water vapour (in grams) present in 1 m3 of air is weighed to determine absolute humidity. This isn’t a very useful parameter in meteorology, even then, it’s more important to know how much water can be obtained in the form of rain from a given volume of air. Another metric, relative humidity, is used for this. Air may contain a fixed amount of water vapour at a given temperature and pressure, if this amount is reached, the air becomes saturated with vapour, and any slight change in pressure or temperature, or any addition of vapour, causes the air to become oversaturated, the excess water vapour condenses as small drops of liquid water. The temperature at which condensation occurs for a given amount of water vapour present in the air at a given pressure is known as condensation temperature or dew point temperature. The percentage ratio between the amount of water vapour present in the air and the amount of vapour needed to make the air saturated with moisture at the same temperature is known as relative humidity.  Relative humidity of 100% means that the air is saturated with vapour and on the verge of condensing the water vapour into drops of water, from a meteorological perspective, this is a state that is theoretically conducive to precipitation. Low relative humidity, on the other hand, means dry air that is not conducive to precipitation.

Specific Humidity

The ratio of the mass of water vapour to the total mass of the air parcel is known as specific humidity (or moisture content). The mixing ratio, which is defined as the ratio of the mass of water vapour in an air parcel to the mass of dry air in the same parcel, is roughly equal to specific humidity. As the temperature drops, so does the amount of water vapour needed to reach saturation. As the temperature of a parcel of airdrops below a certain level, it will gradually reach saturation without adding or losing water mass.

How to Measure Absolute Humidity

The density of water vapour in the air (kg/m3) is known as absolute humidity. To measure absolute humidity, first, calculate vapour pressure in millibars using the dewpoint temperature and formula number. Then multiply the vapour pressure in millibars by 100 to get Pa. Once you have the vapour pressure in Pa, you can use the gas law to measure water vapour density (i.e. absolute humidity) by substituting Rw for R in the gas law formula and using the vapour pressure instead of the total atmospheric pressure used to calculate air density.

Air Density and Volume

Humidity is determined by water vaporization and condensation, all of which are primarily influenced by temperature. As a result, when more pressure is applied to a gas saturated with water, the volume of all components decreases at first, roughly in accordance with the ideal gas law. However, some of the water can condense until it reaches nearly the same humidity as before, resulting in a total volume that differs from that expected by the ideal gas law. Conversely, as the temperature drops, some water condenses, causing the final volume to deviate from what the ideal gas law predicts. As a result, gas volume can also be expressed as dry volume, which excludes the humidity content. This fraction adheres to the ideal gas law more closely. The saturated number, on the other hand, is the volume that a gas mixture would have if the humidity was applied before it reached saturation (or 100 percent relative humidity).

The number of molecules present in a given volume of any gas is constant at a given temperature and pressure (see ideal gas law). So, if the temperature and pressure remain constant, as water molecules (vapour) are added into the volume of dry air, the number of air molecules in the volume must decrease by the same number.  (Adding water molecules to a gas without removing an equivalent number of other molecules would inevitably result in a shift in temperature, pressure, or total volume; that is, a change in at least one of these three parameters.) If the temperature and pressure remain constant, the volume increases, and the displaced dry air molecules move out into the extra volume at first, until the mixture gradually becomes uniform by diffusion.)

Global Climate

Humidity has two main effects on the energy budget and, as a result, on temperature. Water vapour in the atmosphere, for example, contains “latent” energy. This latent heat is absorbed from the surface liquid during transpiration or evaporation, cooling the earth’s surface. At the surface, this is the largest non-radiative cooling effect. It accounts for around 70% of the average net radiative warming at the surface.

Second, of all greenhouse gases, water vapour is the most concentrated. Water vapour is a “selective absorber,” similar to a green lens that allows green light to pass through but absorbs red light. Water vapour, like other greenhouse gases, is invisible to most solar radiation, as can be seen. However, it absorbs the infrared radiation released (radiated) upward by the earth’s surface, which is why humid areas have no nocturnal cooling while desert regions cool significantly. The greenhouse effect is caused by this selective absorption. It increases the surface temperature well above its potential radiative equilibrium temperature with the sun, and water vapour is the primary cause of this warming.

Water, unlike most other greenhouse gases, is not only below its boiling point anywhere on the planet but also below its freezing point at certain altitudes. It precipitates as a condensable greenhouse gas, with a far lower scale height and a far shorter atmospheric lifetime — weeks rather than decades. The Earth’s blackbody temperature, which is below the freezing point of water, would allow water vapour to be removed from the atmosphere if no other greenhouse gases were present.

Conclusion

Water vapour is a highly variable element of the Earth’s atmosphere. It plays an important role in the hydrologic cycle. Humidity suggests the possibility of snow, dew, or fog. Cold air has more humidity than warm air because it contains the same amount of water vapour. Absolute and relative humidity. The water vapour (in grams) present in 1 m3 of air is weighed to determine absolute humidity. Relative humidity of 100% means that the air is saturated with vapour. This is theoretically conducive to precipitation. Low relative humidity, on the other hand, means dry air that is not conducive to rain.