(Written by Ayesha Salim): -

 

Weather and Climate

Climate is the totality of the meteorological conditions and variations over a broad area for a long period of time as opposed to weather, which describes the state of the atmosphere over an area at any given time (more than 30 years).

The atmosphere's current state, known as the weather, changes swiftly (over a day or a week), whereas climate changes slowly and may only be noticed following fifty years or even longer.

Air pressure, temperature, humidity, wind, and precipitation are the same components of both weather and climate.

The year is split into seasons, such as winter, summer, or rainy, on the basis of the monthly averaged atmospheric conditions.

 

The climate of India 

 

The "monsoon" type of climate that characterises India is primarily found in South and South-East Asia. The Arabic term "mausim," which denotes seasons, is the source of the English word "monsoon." The term "monsoon" was first used by Arab navigators several centuries ago to refer to a system of seasonal wind reversals along the Indian Ocean shorelines, particularly over the Arabian Sea, in which the winds blow from south-west to north-east during the summer season and from north-east to south-west during the winter season. In other terms, monsoons are periodic (seasonal) winds in which the wind direction completely reverses every six months.

India has a wide range of climates, from the tropics in the south to the continuously snow-capped Himalayas in the north. Four seasons exist in the nation. From December to February, the weather is generally dry and cool; from March to May, it's hot and dry; from June to September, coastal winds from the southwest dominate and bring monsoon rains to most of the nation; and in October and November, there are receding northeastern dry monsoons.

The northwest experiences temperatures between 12.5 and 30 degrees Celsius, the north and northeast between 17.5 and 30 degrees Celsius, and the south between 22.5 and 30 degrees Celsius. For most of the nation, the average annual rainfall is between 1,000 and 1,500 millimeters, but it can be as low as 150 to 300 millimeters in some northwest regions and as high as 1,500 millimeters along the west coast and in the northeast (1,500 to 2,500 millimeters annually).

South Asia is cut off from the rest of Asia by the Himalayas. While the climate south of these mountains is quite diverse, much like the landscape, some geographers characterize it as violent in general.

Regional variances in temperature can be seen on June days in Churu (Rajasthan), where the mercury may reach 50°C or higher, while it barely reaches 19°C in Tawang (Arunachal Pradesh). On the same day, Drass (Ladakh) may see temperatures as low as -45°C, whereas Thiruvananthapuram or Chennai may experience 20°C or 22°C.

Differences in Rainfall and its Amount by Region - While the remainder of the country experiences rain, the Himalayan regions have snowfall. In contrast to Jaisalmer in Rajasthan, which rarely receives more than 9 cm of precipitation during the same time period, Cherrapunji and Mawsynram there in Hills And mountains in Meghalaya receive over 1080 cm annually.

 

India's climate is determined by a number of factors, thta is-

 

Elements of location and relief

Latitude - From the Rann of Kutch in the western to Mizoram within the east, the Tropic of Cancer runs across the center of the nation. The northern portion of India is located in the semi and temperate zone, while about half of the country's land area southeast of the Tropic of Cancer is in the tropical zone. Due to its proximity to the equator, the tropical zone sees high temperatures all year round with a limited daily and annual temperature range. Due to its distance from the equator, the region north of the tropic of cancer has a harsh environment with a wide range of daily and annual temperatures.

Arrangement of land and water: In the south, India is bordered by bodies of water on three sides, and in the north, it is encircled by a tall, continuous mountain wall. Compared to land, the water warms and cools extremely quickly. Different cabin pressure zones are produced throughout and around the subcontinent depending on the season by this differential heating. The monsoon winds changes as a result of this shift in air pressure.

The Himalayan Range The tall Himalayan mountains in the north effectively provide a climatic barrier. The chilly northern winds that originate close to the Arctic Circle and sweep through central and eastern Asia are protected by these mountains. These mountains are the reason why this subcontinent's winters are less harsh than those of Central Asia. Additionally, these mountains block the monsoon winds, causing them to lose moisture inside the subcontinent.

The sea's influence on climate is moderate, depending on how far away it is. Extreme weather conditions are more common in areas that are farther from the sea because the sea's regulating effect is less. Continentality, or extremely hot summers and extremely frigid winters, is the term used to describe this phenomenon.

Locations in the mountain are often cooler than places in the plains since temperature drops as altitude increases. Despite sharing the same latitude, Agra and Darjeeling experience very different temperatures in January. In Agra, it's 16°C, while in Darjeeling is only 4°C.

Reprieve - India's physiography, or relief, has an impact on a variety of weather factors, including temperature, air pressure, wind speed and direction, and the quantity and distribution of rain. Because to its leeward location along the Western Ghats, the southern plateau stays dry during the months of June and September while the windward portions of the Western Ghats and Assam experience considerable rainfall.

 

Factors affecting wind and air pressure

 

Ground wind and pressures

In the winter, pressure patterns in Central and Western Asia have a significant impact on the weather in India.

A high-pressure center forms in the area to the north of the Himalayas during the winter. The movement of air at a low level from the north toward the Indian subcontinent is caused by this high-pressure system (south of the Himalayan mountain range).

Through Central Asia, those high-pressure surface winds go to India as a dry continental air mass. Over north-western India, these continental winds meet up with trade winds.

On rare occasions, the contact zone may move from the middle Ganga valley toward the east.

As a result, dry northwestern winds affect the whole region of northwest and northern India down to the mid-Ganga valley.

 

Upper air circulation and the jet stream

Westerly winds are the main source of upper air circulation.

Westerly winds that blow from west to east along the troposphere's altitude range of 9 to 13 km continue to have an impact on Western and Central Asia.

These winds circulate across Asia at latitudes that are categorized into two to Tibetan Highlands and north of the Himalayas.

These are also referred to as subtropical westerly air currents because they are found above 27° to 30° North latitude.

Due to the Himalayas and Tibetan Plateau's physical blockage, westerly jet streams in the upper atmosphere split into two branches throughout the winter.

While one branch winds eastward, south of the Himalayas, the southern branch blows north of the Tibetan highlands. The heavy snow in India is significantly influenced by such a southern branch of a jet stream. (Jet Streams are the tropospheric tropopause's slender bands of high-elevation westerly winds. They go at a range of speeds (about 110 km/hr in the summer and 184 km/hr in the winter).

 

Tropical cyclones and the Western Cyclonic Disturbance

The western flow of the Mediterranean region is responsible for the wintertime weather phenomenon known as the western cyclonic disturbances.

Typically, they have an impact just on north and north-western regions' weather.

Tropical cyclones develop across the Indian Ocean and the Bay of Bengal.

These turbulences, which are a result of the easterly flow, affect the nation's coastal areas (Tamil Nadu, Andhra Pradesh, and Odisha coast).

Due to their associated torrential rainfall and tremendous wind speeds, the majority of these cyclones are extremely damaging.

 

Indian seasons

 

The cold weather season (Winter season)

It occurs between December and February. The coldest months of the year include December and January, with average temperatures in the northwest of the country hovering at 10-15 °C (50-59 °F). As one moves closer to the equator, temperatures rise, reaching a peak near mainland India's southeast of 20-25 °C (68-77 °F).

 

The hot weather season (Summer season)

Extending through March to May. The hottest month throughout western and southern India is April, followed by the first few days of May, while May is the warmest time in northern India. Throughout the majority of the interior, May temperatures range from 32 to 40 °C (90 to 104 °F).

 

The south-west monsoon season (Rainy season)

Spanning June through September. This period is dominated by the muggy southwest monsoon season, which begins in May or early June and steadily moves across the nation. Beginning early October, monsoon rains stop falling in North India. Rainfall is often higher in south India.

 

The retreating monsoon season

Between October and November. The months of October and November are usually typically cloudless inside the northwest of India. The northeastern monsoon season brings the majority of the annual precipitation to Tamil Nadu.