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Monsoon trough is the name given to the region in the inter tropical convergence zone which has low pressure.

The duration of monsoon in India is 120 days.

Places with highest temperature Barmer, Jodhpur. Places with lowest temperature Dras, Kargil.

Wheat crop is winter rainfall is useful.

Rajasthan region has high pressure in winter.

Correct option is (c) Dras

Correct option is (c) Barmer

The coldest place in India Dras.

The cause of winter rain in’ Punjab is Cyclones.

The Rainiest place in India Mawsynram.

Aravallis lie parallel to S.W. monsoons and fail to check monsoons.

The Monsoon winds from Arabian Sea and Bay of Bengal meet in Punjab and Himachal Pradesh.

(i) Chennai and Madurai

(ii) July, August.

The western part of Rajasthan is desert. It gets an annual rainfall less than 20 cms. This is due to the following reasons:

1. Rajasthan is under the influence of S.W. summer monsoons. The Aravallis system lies parallel to the direction of S.W. monsoons coming from Arabian Sea. So this mountain system is unable to check these winds. So western Rajasthan is practically dry. The southern part gets some rainfall.
2. This area lies at a great distance from the Bay of Bengal. The Bay of Bengal monsoons become dry and lose their moisture when they reach Rajasthan.
3. This area is away from the Himalayan region. So it does not come under the influence of monsoons giving rain in Sub-Himalayan region.

1. The area of low pressure is replaced by high pressure air.
2. Monsoons withdraw from Northern plains by the end of October.

The months of October and November are known for retreating monsoons:

1. The monsoon low pressure trough becomes weaker and is replaced by high pressure.
2. The effect of monsoons over Indian landmass begins to shrink.
3. The direction of surface winds starts reversing.

In Rajasthan, Aravallis lying parallel to S.W. monsoons fail to check these. So they do not give rainfall. Deccan plateau is situated in rain shadow of western ghats. In this area, the descending winds become dry and do not give rainfall.

High mountains act as barriers for cold or hot winds. The Himalayas check the cold winds from Siberia from entering in India. High mountains like Himalayas cause rainfall by checking moist winds. The leeward side of a mountain remains in Rainshadow and is dry.

El Nino is a periodic warm current blowing along the coast of Peru in Pacific Ocean. It is a Spanish word which means child. It increases the surface temperatures and weakens the trade winds. The difference between pressure in Pacific Ocean and Indian Ocean is used to compute the intensity of Monsoons; early or late monsoons.

The month of October forms a period of transition from the hot rainy season to dry winter conditions. The retreat of monsoons is marked by clear skies and rise in temperature. Day temperatures are high, but nights are cool and pleasant. The land is still moist. Owing to conditions of high temperature and humidity the weather is rather oppressive during the day. This is known as ‘October Heat’.

The direction of summer monsoons is South-west.

Kharif crop depending on rains is Rice.

The leeward dry slope of mountain.

Deccan plateau.

Jet streams are high velocity winds at high altitudes. A jet stream is a narrow tubular shaped flow of wind along the troposphere. These have a velocity of 500 kms per hour and are located at 5 to 12 kms with an average location between 20°S to 40°N latitudes.

Loos are hot dusty winds caused by low pressure in hot season. These are very hot and dry winds. These are called ‘Loo’ in local language.

The driest places of the country are: Leh, Jodhpur, Delhi while Shillong, Mumbai, Kolkata and Trivandrum are the wettest areas.

The period of rainy season is from June to September. 75% to 90% of rainfall occurs in this period.

The climate of India is mainly based on the following facts:

1. Distance from the equator: The places which are situated near the equator have high temperature whereas the places away from the equator do not have high temperature.

2. Height above sea level: The higher you go, the cooler it is. That is why the mountainous regions are cooler than plains.

3. Distance from the sea: The places near the sea have equable climate. Neither the summers are very hot nor the winters are cold, whereas in the parts away from the sea the summers are hot and winters are cold.

4. Winds: The winds have a great affect on the climate of India. The winds coming from the sea are full of moisture and they cause heavy rain. On the other hand, the winds that come from the land are dry winds and cause no rain.

5. Direction of the mountains: Wherever the mountains are located in the way of the winds, the winds are forced to rise against the mountains and cause rainfall. For example, when the moisture laden monsoon winds strike against Himalayas they cause heavy rain in West Bengal and Assam. On the other hand, the Aravali mountains run parallel to the direction of the monsoons that blow from the Arabian Sea and there is no rain in Rajasthan.

6. Nature of the soil: Sand gets heated and cooled quickly. The land is sandy in Rajasthan. That is why, the temperature is of extreme type there.

7. Slope of the land: If the land slopes towards the sun the rays of the sun will fall vertically and the temperature will be high. On the contrary if the land slopes away from the sun the rays of the sun will be slanting and the temperature will be low.

8. Forests: The regions with dense forests receive heavy rain, because the winds blowing over these forests gain moisture from the leaves of the trees, lose temperature and cause rain.

The Indian Weather: The Indian sub-continent has a tropical monsoon climate. Monsoons dominate the climate of the sub-continent. Monsoons exercise a unifying influence on the weather conditions of India making it a single meteorological unit. India has a broad unity of monsoon type of climate having the same rhythm of season. The advance and retreat of monsoon divide the weather into different seasons.

(A) Seasons of N.E. Monsoons.

1. The Cold Season. December to February.
2. The Hot Season. March to May.

(B) Season of S.W. Monsoons.

1. The Rainy Season. June to September
2. The Season of Retreating Monsoon. October to November.

1. The Cold Season: The cold season lasts from December to February.
(a) Temperature. The sun is overhead at Tropic of Capricorn. The Indian sub-continent has winter season. January is the coldest month. The southern parts have warm conditions. (20°C) while low temperatures (10°C) are found in N.W. India.

(b) Pressure and Winds. High pressure is developed over N.W. part while a low pressure exists over the Indian Ocean with the result winds blow from land to sea. The out-blowing winds are Westerly in Northern plain and North Easterly over the rest of the country.

Rainfall. The N.E. Monsoons are off-shore winds and are dry. But these winds pick up some moisture crossing Bay of Bengal and give rain to S.E. coast of India. Some cyclones from Mediterranean Sea also bring a small amount of rain (10 to 20 cms.) to Northern plains. Night Frost is common in the N.W. parts.

2. The Hot Season. The hot season lasts from March to May.

(а) Temperature: As the sun’s rays fall vertical over Tropic of Cancer, the temperature begins to rise. The average temperature is above 30 C; the maximum temperature rises to 50°C in Banner (Rajasthan). The daily range of temperature rises in inland areas.

(b) Pressure and Winds: Intense heat results in the development of low pressure over N.W. India and Pakistan. A high pressure exists over Indian Ocean. S.W. Monsoons begin to blow from sea to land. ‘Norwesters’ and ‘Loo’ blow over Northern plains.

(c) Rainfall: Some areas receive convectional rainfall. The west coast also starts receiving rainfall. Most of the country is dry in the pre-Monsoon period.

3. The Rainy Season: The rainy season lasts from June to September.

(а) Temperature: The sun shines vertical over Tropic of Cancer. The temperatures are more than 30°C. With the onset of monsoon, there is a drop in temperature (5° to 10°C) with the result July is not the hottest month.

(b) Pressure and Winds: S.W. Monsoons blow from sea to land with a “burst’ on the West coast. It blows in two currents.

1. The Arabian Sea Current,
2. The Bay of Bengal Current

(c) Rainfall: S.W. Monsoons are rain giver as most of the sub-continent gets rainfall in this season. The Arabian Sea branch gives heavy rainfall on the West Coast, but Deccan plateau lies in rain shadow of Western Ghats. The Bay of Bengal branch gives heavy rainfall in Eastern Himalayas. The rainfall goes on decreasing up the Ganges valley with the decrease in moisture. Rajasthan is practically a desert.

4. The Season of Retreating Monsoon: S.W. Monsoons begin to withdraw from the sub-continent during the first week of October. The sun begins to move towards equator. There is a decrease in temperature. Hot and sticky weather is found. Some tropical cyclones are developed which give heavy rainfall in coastal areas. Cool-weather begins in N.W. India, but the Southern parts have an equable climate.

Characteristics of rainfall in India: The average annual rainfall in India is about 110 cms. It is estimated that more than 85% of this rainfall is received in summer. The main characteristics of summer rainfall are given below:

1. Monsoonal rainfall. Most of the rain is received from S.W. summer monsoons during the period mid-June to mid-September. It is seasonal rainfall.
2. Uncertain rainfall. Summer rainfall is quite uncertain. Some times monsoons start early resulting in floods. Often the onset of monsoons is delayed resulting in drought. The early or late retreat of monsoons also results in serious droughts.
3. Unequal distribution. The rainfall is Unevenly distributed over the country. About 10% of the country gets more than 200 cms of rain while 25% of the country gets less than 75 cms of rain.
4. Heavy rainfall. Indian rainfall is heavy and downpouring type. It is often said, “It pours, it never rains in India.”
5. Relief rainfall. The amount of rainfall is determined by the presence of mountains. High mountains force monsoons to rise and cause rain.
6. No continuity of rainfall. Summer rain is characterised by breaks or dry spells.
7. Variable rainfall. Most of the areas have variable rainfall, as much as 30 cms. plus or minus. Due to variability in areas of low rain, famines occur.

The destructive cyclones are called Kal Baisakhis in West Bengal.

Elnino current flows along the coast of Chile. It is studied for the reasons causing Monsoon.

Monsoons are seasonal winds.

The dry period between monsoons is called Break.

The word Monsoon is said to be derived from the Arabic word ‘Mausam’ meaning season. This word was first applied to the winds blowing over the Arabian sea. Monsoon implies seasonal reversal of the wind pattern over the years. Monsoon winds are those seasonal or periodic winds which changes their direction with the season. These winds blow from sea to land of six months during summer and from land to see during winter. Thus with the change of season the pattern of winds, temperature and rainfall changes.

The monsoon winds blow in south-west direction on the west coast. These are highly charged with water vapour. I’; advances rapidly over west coast. The rains begin rather suddenly in the first week of June. This sudden onset of rain is often termed as ‘Monsoon Burst’. This rainfall is heavily accompanied by thunder and lighting. The rain is so sudden and heavy that it appears as if a balloon of water has been burst.