Climate is the sum total of the weather conditions and their variations of an area over a large period of time. Large period refers to periods ranging to 30 years or more.
Temperature, pressure, humidity, wind and precipitation are the elements of climate. The climate of a region depends on several factors such as latitude, altitude, relief features, pressure and wind system, distance from sea and ocean currents,etc.
Uttar Pradesh broadly comes under tropical monsoon climate. However, regional variations in the elements of climate are found over the vast area of the state. The regions of homogenous climatic conditions are classified into climatic zones.
Climate of Uttar Pradesh
Several scholars have identified different climatic zones in Uttar Pradesh. Important Among them are given below:
According to Koppen’s classification Uttar Pradesh comes under Monsoon type with dry winter climate (Cwg)/ Gangetic plain type.
According to Threwarta’s classification, Uttar Pradesh comes under the Humid Subtropical Climate (Caw).
According to R.L. Singh, Uttar Pradesh has the following climatic regions:
Sub-humid Continental Climate– Upper Gangetic plain region comes under it. This type of climatic region has an average July temperature between 25°C and 40°C and average January temperature between 17°C and 25 C. The average annual rainfall ranges between 75 and 150cm.
Sub-humid Transitional Climate– It includes the eastern part of Uttar Pradesh. It has average rainfall between 100 and 200 cm. Average temperature ranges between 25°C and 40°C in July and between 10°C and 25°C in January.
Humid South East-Southern part of Sonbhadra district comes under Humid South-East climate. Average temperature ranges between 25°C and 35°C in July, and 12°C and 27°C in January. Average annual rainfall ranges between 100 and 200 cm.
Semi-arid Tropical –Lalitpur district of Uttar Pradesh comes under this type of climate. Annual rainfall ranges between 50 and 100 cm. Temperature ranges between 26°C and 40°C in July to 15°C and 28°C in January.
Semi-arid Sub-tropical – Western parts of districts along the western border of Uttar Pradesh come under this type of climate. Western parts of Saharanpur, Shamli, Ghaziabad, Gautam Buddha Nagar, Bagpat, Aligarh, Mathura and Agra are included in this. Annual rainfall ranges between 25 and 75 cm. Temperature ranges between 25°C and 28°C in July and 15°C and 25°C in January.
Factors Affecting Climate of Uttar Pradesh
Following factors are responsible for providing Uttar Pradesh with a tropical monsoon climate:
Latitude
Uttar Pradesh is situated north of the tropic of cancer.
Its latitudinal position provides it an extreme climate with high daily and annual range of temperature.
Continentality Effect
Uttar Pradesh is at a significant distance from the sea.
Thus it does not get the moderating effect of the sea and remains very hot during summers and very cold during winters.
Presence of Himalayas
Presence of Himalayas in the north prevents thecold winds from central Asia to enter into the Indian Subcontinent.
Thus winters in Uttar Pradesh, as well as the subcontinent, are milder compared to central Asia.
Himalayas also provide rainfall to the northern plains by obstructing the monsoonal winds.
Pressure and Winds
Development of low-pressure region in Northern Plain during summers and reversal of winds are responsible for the monsoonal climate of India along with Uttar Pradesh.
Upper air circulations also play a very important role in the onset of monsoon.
The subtropical westerly jet stream is responsible for bringing western disturbances in Northern India.
Seasons of Uttar Pradesh
Metrologists identified four distinct seasons in India. All of these four distinct seasons exist in the state. These are given below:
Cold weather season
Hot weather season
Southwest monsoon season
Retreating monsoon season
Cold Weather Season
The season starts in mid November.January is the coldest month. The mean monthly temperature is less than 15°C. Diurnal temperature range is high and reaches up to 15°C.
Northwestern parts of the state are the coldest and experience cold waves along with fog and frost.
Temperature decreases from south to north. Sun is positioned over the tropic of Capricorn by the end of December. High-pressure conditions exist over Uttar Pradesh during the cold weather season.
The southern branch of the subtropical jet stream is positioned over northern plains. Light winds blow from Northern plains towards the ocean.
Clear skies, dry and stable air are the characteristic features of this season. Small amounts of rainfall is brought by the western disturbances during this season.
This rainfall is beneficial for Rabi crops.
Hot Weather Season
This season starts from March and remains till mid-June. During the summer season, the sun apparently moves towards the tropic of cancer. The temperature starts increasing and the mean-maximum temperature reaches 42°C in May. Diurnal temperature range remains between 10°C and 14°C.
Low-pressure conditions exist over the northern plains. Hot and dry winds known as loo blow in the afternoon.
Dust storms are also prevalent during the evening. Dust storms also bring some rains.
Some amount of convectional rainfall is also received. The average rainfall is between 10 and 25 cm.
Summer season is the severest in Bundelkhand region in Uttar Pradesh due to proximity with the tropic of cancer. Agra and Jhansi are the hottest in the state. Bareilly has minimum temperatures.
South West Monsoon
Due to high temperatures during summer, the low-pressure belt over Northern Plains further intensifies and attracts the trade winds from the southern hemisphere. These trade winds enter India as South-west monsoons.
Monsoonal winds enter Kerala by 1 June and reach Gangetic plain by 15 June. South-west Monsoons is divided into Arabian Sea Branch and Bay of Bengal ( BoB) Branch. The BoB branch enters Uttar Pradesh from the eastern side and Arabian sea branch from the western side. Uttar Pradesh receives most of the rainfall from the BoB branch. BoB branch is conjoined by Arabian sea branch in the Gangetic plain.
Amount of rainfall decreases from the Eastern parts of Uttar Pradesh to the western part. However, the variability of rainfall increases from the eastern part to the western part. The average range of rainfall in the east is 100-200 cm and 60-100 cm in the western part.
Retreating Monsoon
By the end of September low-pressure zone starts shifting southwards from the Gangetic Plains.
This brings the end of monsoon in Gangetic plains including Uttar Pradesh. Retrieval of monsoon is rapid in comparison to the onset of monsoon.
Rainfall Distribution in Uttar Pradesh
Uttar Pradesh receives most of the rainfall (approx. 90%) through south-west monsoons. Due to rainfall being concentrated in four months of June-September the state receives subsequent cycles of flood and droughts.
Eastern parts of the state receive more rainfall compared to the western parts. The eastern region receives highest annual rainfall, followed by the central region, western region and Bundelkhand respectively.
The eastern Uttar Pradesh has a rainfall variability below 25% and the rest of Uttar Pradesh has variability between 25% and 50%.
Uttar Pradesh comes into regions of medium rainfall and areas of low rainfall.
Areas of Medium Rainfall- These regions receive rainfall in the range of 100-200cm.The northern part of Uttar Pradesh including Bhabar and Terai region comes into this category.
Northern Saharanpur, Maharajganj, Kushinagar, Balrampur, etc. are included in this.
Areas of Low Rainfall– These regions receive rainfall in the range of 50-100 cm.Western Uttar Pradesh is included in this.
The districts of Mathura, Aligarh, Gautam Buddha Nagar and Ghaziabad receive very less rainfall.
