Weather and Climate - UPSC World Geography Notes

Weather and climate play pivotal roles in shaping the environment around us, influencing everything from daily activities to global ecosystems. While weather refers to the short-term atmospheric conditions in a specific area, such as temperature, precipitation, humidity, and wind patterns, climate encompasses the long-term patterns and averages of these elements over extended periods, typically spanning decades to centuries. Both weather and climate are dynamic and interconnected phenomena driven by complex interactions between the atmosphere, oceans, land surfaces, and various natural and human-induced factors. Understanding the intricacies of weather and climate is crucial for predicting natural disasters, managing resources, and addressing climate change challenges that impact societies worldwide.

Weather

Temperature, pressure, wind, humidity, and precipitation collectively interact within the Earth’s atmosphere.
Their interaction significantly shapes various atmospheric conditions, such as wind direction and speed, solar radiation intake, cloud formation, and precipitation levels. These elements are considered the building blocks of both weather and climate.
The influence of these elements is dynamic, varying from one location to another and over different periods. This influence can be localised to a small area and exist for a brief duration.
Weather represents the short-term atmospheric conditions of a specific location, considering one or more of these elemental components.
Consequently, two nearby places might experience contrasting weather conditions simultaneously, reflecting the dynamic and localised nature of weather patterns.

SEASONS

Seasons signify distinct periods within a year that feature consistent weather conditions. The cycle of seasons results from the Earth’s axial tilt and its orbit around the sun, repeating yearly.
In temperate regions, four primary seasons are typically observed, each lasting for around three months: spring, summer, autumn, and winter.
However, in our country, India, three distinct seasons are experienced: summer, winter, and monsoons.

The Indian Meteorological Department recognizes four main seasons:
- Cold weather season (December to February)
- Hot weather season (March to May)
- Advancing monsoon season or rainy season (June to September)
- Retreating monsoon season (October to November)

Regions near the equator receive relatively direct sunlight throughout the year, resulting in consistent temperatures. Hence, these equatorial areas do not experience significant seasonal variations.

Coastal regions often experience reduced seasonal variations due to the moderating influence of the nearby oceans.

In polar regions, only two seasons occur: a prolonged winter and a brief summer, reflecting the extreme differences in sunlight exposure due to the Earth’s tilt.

PRIMARY ELEMENTS OF WEATHER AND CLIMATE

TEMPERATURE

Temperature is the measure of the kinetic energy present in the air, which translates into the perception of heat or cold.
The commonly used scales to quantify temperature are Celsius, Fahrenheit, and Kelvin. Thermometers are instruments employed to gauge temperature.
Temperature directly corresponds to the kinetic energy generated by the movement or vibration of particles in the air.
When particles move or rotate at a higher speed, the temperature increases, and conversely, as these particles slow down, the temperature drops.

ATMOSPHERIC PRESSURE

Air pressure is a crucial aspect of weather and plays a significant role in establishing and altering atmospheric conditions, making it a vital element in accurate weather prediction.
Air pressure refers to the force exerted by the weight of air in the Earth’s atmosphere.
Commonly known as barometric pressure, it’s named after the device used to measure it. While air might seem weightless, it contains various gases like nitrogen, oxygen, argon, and carbon dioxide in tiny particles, resulting in a degree of weight.
The gravitational force of the Earth causes these particles to create pressure, and as there is more air above the surface, the air pressure at ground level is higher. Understanding air pressure variations is crucial for weather forecasting.

WIND

Winds play a crucial role in various weather phenomena, including the formation of cold and warm fronts, cloud movement, thunderstorms, and hurricanes.
Wind is essentially the movement of air across the atmosphere from areas of high pressure to those of low pressure.
The wind’s speed and strength are determined by the difference in air pressure and the distance between high and low-pressure regions.
Wind speed is measured using a device called an anemometer, while the wind’s direction can be determined by a weather vane, also known as a wind vane.

PRECIPITATION

Precipitation is the result of water vapour condensing into its liquid or solid forms and falling to the Earth’s surface when it becomes too heavy to stay suspended in the atmosphere.
It encompasses various forms such as rain, snow, hail, and graupel.
The process of evaporation and subsequent condensation is the primary mechanism behind precipitation formation.
As water vapour cools and condenses, it forms into droplets or ice crystals, leading to precipitation.
To measure rainfall, meteorologists use a rain gauge, a device designed to collect and measure the quantity of rain that falls over a specific period. This instrument helps in understanding the amount of rainfall received in a given area.

HUMIDITY

Humidity refers to the amount of water vapour in the atmosphere, and it is a crucial factor in weather formation and human comfort levels.
It doesn’t usually have a direct connection with wind speed measurement.
The device used to measure humidity is a hygrometer, not wind speed.

VISIBILITY

visibility and its importance due to conditions like mist, haze, and fog.
However, the instrument or device used to measure visibility typically includes various devices like transmissometers, nephelometers, and forward scatter sensors, among others.
These tools are used to detect and measure visibility under different weather conditions. The forward scatter sensor is just one of the tools used for this purpose.

CLOUDS

Clouds form as water vapour condenses into water droplets or ice crystals.
Identifying different cloud types and understanding the associated weather patterns can be invaluable in gauging weather conditions visually.
Weather satellites and radar systems are essential modern tools used by meteorologists to observe clouds comprehensively. These technologies allow meteorologists to analyse various cloud attributes, including density, moisture content, temperature, and movement, aiding in accurate weather forecasting and analysis.

DURATION OF SUNSHINE

Sunshine duration refers to the duration of direct exposure of the Earth’s surface to solar radiation, commonly measured as sunshine hours within a specific period (typically per day or year).
This measure significantly impacts various meteorological factors, influencing the overall weather patterns.
Instruments such as sunshine recorders, particularly Campbell–Stokes recorders, are used to measure the duration of sunshine.
These devices focus sunlight through a spherical lens onto specific tape, recording the length of time the sun is visible.

CLIMATE

Climate refers to the typical weather patterns prevailing over a significant area across different seasons in a year.
It’s derived from long-term data, typically spanning about 35 years, collected from a broader region.
Different regions have distinct climate types based on their typical weather conditions. For instance, Rajasthan exhibits a hot and arid climate, Kerala experiences a tropical rainy climate, while Greenland showcases a cold desert climate, and Central Asia features a temperate continental climate.
Climate, unlike weather, is relatively stable and considered to be more enduring in a specific area.

FAQs related to weather and climate:

1-What is Weather?

Weather is the current state of the atmosphere in a specific place and time. It encompasses conditions like temperature, humidity, wind speed, precipitation, and cloud cover.

2-What Causes Different Weather Patterns?

Several factors cause diverse weather patterns, including the Earth’s tilt, proximity to oceans, elevation, latitude, and wind patterns.

3-What is Climate?

Climate refers to long-term average weather patterns in a particular region. It’s determined by analysing weather data over an extended period, typically around 30 years or more.

4-How Do Weather and Climate Differ?

Weather refers to short-term atmospheric conditions, while climate represents long-term weather patterns. Weather changes day to day, while climate remains relatively stable over extended periods.

5-What Tools Are Used to Measure Weather Elements?

Meteorologists use various instruments such as thermometers for temperature, anemometers for wind speed, barometers for air pressure, and rain gauges for precipitation.

6-Why Are Seasons Different in Various Regions?

Seasonal variations depend on a region’s location, such as proximity to the equator, the presence of mountains, or the influence of ocean currents. These factors determine the timing and characteristics of seasons.

7-How Does Climate Change Affect Weather?

Climate change can influence weather patterns by causing shifts in temperature, precipitation, and extreme weather events like heat waves, storms, or droughts.

8-What Are the Different Climate Types?

There are several climate types worldwide, including tropical, arid, temperate, polar, Mediterranean, continental, and more, each characterised by distinct weather patterns.

9-How Does Human Activity Impact Climate?

Human activities, particularly greenhouse gas emissions from burning fossil fuels, deforestation, and industrial practices, significantly contribute to climate change and global warming.

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Weather and Climate – UPSC World Geography Notes