Shaktichakra, the wheel of energies

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Posts Tagged ‘Arabian Sea

Winds of monsoon India

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This panel of four images shows: top left, winds at around sea level; top right, winds at about 1,460 metres altitude (around 4,780 feet); lower left, winds at 3,010 metres (9,880 feet); lower right, winds at 5,570 metres (18,280 feet).

These are the wind patterns that are bringing the monsoon to us from just above the equator, as they travel east-north-eastwards towards the Indian peninsula, and earlier north-north-westwards as they travelled from near Madagascar and the Mascarene Islands, which lie about 21 degrees south of the equator.

RG_India_monsoon_winds_20150613_bIn the top two images, the south-west (from our point of view) winds sweeping across the Arabian Sea are the dominant feature, with the winds at the higher of the two altitudes (right, at 850 millibars, or mb, which is around 1,460 metres) rushing in at just the direction and velocity they ought to. Winds at near-sea level are less powerful, and in both the two top images winds are also seen travelling due north up the Bay of Bengal.

In the lower two images, the vortex of Cyclone Ashobaa is clearly seen, with wind trails running due east across the Arabian Sea, then across peninsular India and out over the Bay of Bengal towards Burma. More markdly with the winds in the lower left image, which are at 700 mb or 3,010 metres, they scarcely touch central and north-western India and the Gangetic belt (whereas the winds at lower altitudes, as seen in the upper two images, do).

Finally, in the lower right image are the winds at 500 mb, or 5,570 metres. Here we see them streaming powerfully down from the Hindu Kush-western Himalaya, across north India and thence right across the Gangetic belt, through Assam and the north-east. These are the major wind patterns we have now in mid-July, and they will change in strength, direction and intent as El Nino changes and also as the Northern hemisphere summer continues over the Eurasian land mass.

These wonderful images are taken from the ‘earth’ weather observation visualisation which skillfully employs the forecasting by supercomputers of current weather data from the Global Forecast System (GFS) and the NOAA/NCEP climate and weather modelling programmes.

Written by makanaka

June 13, 2015 at 21:54

At water’s edge in India

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Nearly 250 million people live within 50 km of India’s 8,000 km coastline. Eighty-seven cities and towns located in these coastal areas together dump 5.5 billion litres of wastewater into the sea every day. Less than a tenth of this water is treated, making the scale of pollution of our coastal ecosystems daunting.

India's coastal districts

India's coastal districts

Just as it is with worldwide species diversity, so it is with India’s coastal ecosystems and habitats — the growth in knowledge and understanding of both runs simultaneous with their destruction. Only from the early-1990s, when the oceanographic sciences became stronger in the country’s scientific matrix, and when multi-sectored studies and research began to be attempted as a means — perhaps the only way — of figuring out complex problems, has there been a general understanding of the large-scale dynamics of coastal circulation in the Arabian Sea and the Bay of Bengal.

To understand our coasts, the physical sciences combine with social sciences. Both work together: the anthropocentric social science view of global change complements the geocentric natural sciences view. Coastal zones are important for both, and it is in the last decade that such a convergence of understanding has begun to be explained. The trouble is, this understanding has come at a time of widespread economic growth and industrial expansion, so that as knowledge of India’s coasts (and our human impact on them) increases so too does the intensity and scale of the impact.

The scale is daunting. Most of India’s 8,000-km-long coastal regions are low-lying and densely populated, with nearly 250 million people living within 50 km of the coast, many of them in the 130 cities and towns that together form the engine of India’s economy, including Mumbai, Kolkata, Chennai, Goa, Surat, and Thiruvananthapuram (see map). Between 20-60% of the population in these individual settlement zones live in slums where they pursue their livelihood, and this section is automatically located in areas most vulnerable to natural disasters; areas that are already subject to periodic flooding.

At the same time, they are surrounded by a web of infrastructure that is becoming denser and more valuable every year: transport and freight networks, road and rail corridors, industrial zones and parks, maritime and port facilities, petroleum industries and refineries, import-based industrial and commercial domains — all located in coastal areas and competing for land and water with villages that have long depended on coastal resources for survival. That survival has always been relatively easy since coastal regions are home to a rich and varied biodiversity, they have had abundant rain-fed and groundwater resources, and they depended commercially on old trading centres. As the settlement mix changed, and as land use did too, India’s coastal talukas, tehsils and blocks either merged with a creeping mantle of urbanisation or warred with it. Either way, complex coastal ecosystems suffered.

Municipal wastewater constitutes the largest single source of coastal marine pollution. The Central Pollution Control Board estimates that 87 cities and towns located in India’s coastal areas in nine states together emit more than 5.5 billion litres of wastewater per day, which is almost 80% of their total water supply (the estimate in million litres per day, or MLD, which is the measure that water resource and pollution control authorities use, is 5,560.99 MLD).

This is a staggering volume of fluid, equivalent to a third of the total quantity of wastewater generated by 644 Class I cities and Class II towns in the entire country. It is also 2.5 times the volume of wastewater (about 2.2 billion litres/day) that the same 87 cities generated two decades ago. Of the 5.5 billion litres/day — less than a tenth (521.51 MLD) — is treated to any level before being released into coastal waters. The three states of Maharashtra (45%), West Bengal (26%) and Tamil Nadu (9%) account for the bulk of wastewater flushed into our coastal seas, while about 3.22 billion litres/day of wastewater flow into the Arabian Sea and about 2.33 billion litres/day flow into the Bay of Bengal.

The full article is part of the latest Agenda journal on coastal communities. Agenda is the theme-based irregular journal of Infochange India, which I write for regularly.