Effect of Relief The rain-laden winds from Arabian Sea bring orographic rainfall in Konkan coast and Western Ghats (about 250 em). The leeward side receives only 3775 em rainfall as it falls in the rain-shadow area. Thus TamilNadu gets no rain.
Distribution of Rainfall Except for Thar, north-west region of Jammu and Kashmir and some areas of Tamil Nadu, the rest of the country receives rainfall from southwest monsoon. 200 cm and above-Western Ghats and North-eastern region. 100-200 cm-West Bengal, Orissa, Bihar, Jharkhand, Andhra Pradesh, Kashmir foothills, Tamil Nadu coast. Less than 100 cm-Rajasthan, Punjab, western Uttar Pradesh, western Madhya Pradesh and Deccan plateau.
Variability of Annual Rainfall One of the important characteristic features of the monsoon is its variability. There may be a deviation by 20 to 50 per cent in the actual rainfall of a place in a year.
The variability of rainfall may be calculated with the help of the following formula:
C = (Standard deviation/Mean) x 100
where C is coefficient of variation.
The value of C indicates the deviation from the mean value of rainfall. In India, the coefficient of variation generally ranges between 15 and 30 per cent. The coefficient of ~ariation in places such as Mangalore, Sikkim, Arunachal Pradesh, Nagaland, Manipur and Mizoram is less than 15 per cent. On the other hand, it may be as high as 30 per cent in the interior regions of Maharashtra, Andhra Pradesh and Karnataka. So is the case with southern Gujarat, western Madhya Pradesh and central parts of Uttar Pradesh. The variability of rainfall over Rajasthan and Gujarat is over 40 per cent, while the desert areas of Rajasthan and parts of Kutch and Gujarat may have a rainfall variability ranging between 50 and 80 per cent.
Variability of rainfall plays a crucial role in Indian agriculture. Areas having high variability of rainfall suffer from a chronic water scarcity. Crop failures are common in such areas. These areas also experience spells of drought frequently.
Showing posts with label Wheather. Show all posts
Showing posts with label Wheather. Show all posts
Friday, October 30, 2009
SEASONS IN INDIA
SEASONS IN INDIA
On the basis of monsoonal variations there are four seasons in India.
THE COLD WEATHER SEASON It starts in early December. The mean January temperature in Chennai and Thiruvananthapuram is about 24°-25°C, while in the Northern Plains it is about 10°-15°C. A high pressure area is developed over the plains in the north-west. Sometimes weather is disturbed by cyclonic depressions which originate over the Mediterranean and travel eastwards and reach north-west India. These western disturbances bring rainfall in Punjab region. The Tamil Nadu coastland also receives rainfall during this season from retreating northeastern winds.
THE HOT-WET WEATHER SEASON It starts in March and continues upto June. The Inter-Tropical Convergence (ITC) belt shifts from south to north. Along with it moist equatorial air is drawn from the Indian Ocean due to the anticyclone located around Malagasy. The highest temperature in March is about 38°C in the Deccan plateau. In April, Gujarat and Madhya Pradesh become more hot. The day temperature ranges from 38°C to 43°C. It increases upto 48°C in north-west India in May-June.
Due to increase in temperature the air pressure decreases. A low pressure belt develops by the end of May in Thar desert. Mango showers (pre-monsoon showers) occur in the Malabar Coast. A high pressure belt located in Deccan plateau checks the advance of the monsoon in northern regions. Assam and Bengal receive some rainfall through evening thunderstorms called knl baisakhi. Loa is the dry local wind that occurs in,the north-western region.
THE SOUTH-WEST MONSOON SEASON Due to the intense low pressure belt developed in the north-western plains, the south-west monsoon enters the Indian subcontinent. It blows from the Bay of Bengal and the Arabian Sea.
The normal dates of the onset of monsoon are-May 20 in Andaman and Nicobar Islands, May 29 in Kerala, June 15 at Kolkata and July 1 at Delhi. Cherrapunji (1,070 em)
in Khasi hills receives the maximum amount of rainfall in the world due to local relief factors. Due to the Himalayan and Purvanchal Hills, the rain-laden winds move in northwest direction and cause rainfall in the plains (due to easterly current).
Easterly Depression means a series of depressions which originate in Bay of Bengal. It travels in north-westerly direction and causes rainfall.
On the basis of monsoonal variations there are four seasons in India.
THE COLD WEATHER SEASON It starts in early December. The mean January temperature in Chennai and Thiruvananthapuram is about 24°-25°C, while in the Northern Plains it is about 10°-15°C. A high pressure area is developed over the plains in the north-west. Sometimes weather is disturbed by cyclonic depressions which originate over the Mediterranean and travel eastwards and reach north-west India. These western disturbances bring rainfall in Punjab region. The Tamil Nadu coastland also receives rainfall during this season from retreating northeastern winds.
THE HOT-WET WEATHER SEASON It starts in March and continues upto June. The Inter-Tropical Convergence (ITC) belt shifts from south to north. Along with it moist equatorial air is drawn from the Indian Ocean due to the anticyclone located around Malagasy. The highest temperature in March is about 38°C in the Deccan plateau. In April, Gujarat and Madhya Pradesh become more hot. The day temperature ranges from 38°C to 43°C. It increases upto 48°C in north-west India in May-June.
Due to increase in temperature the air pressure decreases. A low pressure belt develops by the end of May in Thar desert. Mango showers (pre-monsoon showers) occur in the Malabar Coast. A high pressure belt located in Deccan plateau checks the advance of the monsoon in northern regions. Assam and Bengal receive some rainfall through evening thunderstorms called knl baisakhi. Loa is the dry local wind that occurs in,the north-western region.
THE SOUTH-WEST MONSOON SEASON Due to the intense low pressure belt developed in the north-western plains, the south-west monsoon enters the Indian subcontinent. It blows from the Bay of Bengal and the Arabian Sea.
The normal dates of the onset of monsoon are-May 20 in Andaman and Nicobar Islands, May 29 in Kerala, June 15 at Kolkata and July 1 at Delhi. Cherrapunji (1,070 em)
in Khasi hills receives the maximum amount of rainfall in the world due to local relief factors. Due to the Himalayan and Purvanchal Hills, the rain-laden winds move in northwest direction and cause rainfall in the plains (due to easterly current).
Easterly Depression means a series of depressions which originate in Bay of Bengal. It travels in north-westerly direction and causes rainfall.
Thursday, October 29, 2009
Climate
CLIMATE
The average weather condition and variations in these conditions in both space and time over a large area is called the climate of a place. If weather information deals with a specific event, then climate represents the generalisation of the weather. Weather conditions over a specific length of time, usually a period of at least 30 years, are taken into consideration. The main elements of climate are tempera
19. Saline and alkali soils 20.
(iv)ture, atmospheric pressure, wind and humidity (including precipitation).
INFLUENCES ON CLIMATE On a large scale, the climate of a particular region is determined by: (i) latitude and tilt of the earth's axis, which determines the amount of solar radiation received by the area; (ii) the distribution of land and sea and proximity of ocean currents; (iii) the altitude and topography of the area; (iv) the location of the area in relation to the main circulation belts of the earth.
The average weather condition and variations in these conditions in both space and time over a large area is called the climate of a place. If weather information deals with a specific event, then climate represents the generalisation of the weather. Weather conditions over a specific length of time, usually a period of at least 30 years, are taken into consideration. The main elements of climate are tempera
19. Saline and alkali soils 20.
(iv)ture, atmospheric pressure, wind and humidity (including precipitation).
INFLUENCES ON CLIMATE On a large scale, the climate of a particular region is determined by: (i) latitude and tilt of the earth's axis, which determines the amount of solar radiation received by the area; (ii) the distribution of land and sea and proximity of ocean currents; (iii) the altitude and topography of the area; (iv) the location of the area in relation to the main circulation belts of the earth.
WEATHER
WEATHER
Weather is the state of atmosphere as determined by the meteorological phenomena that are occurring at any one place and time. The meteorological phenomena include temperature, precipitation, winds, clouds, sunshine, pressure and visibility.
Weather is the state of atmosphere as determined by the meteorological phenomena that are occurring at any one place and time. The meteorological phenomena include temperature, precipitation, winds, clouds, sunshine, pressure and visibility.
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