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Here is why Rain-bearing Clouds have been thinning out across India in last 50 Years!

India gets around 70 per cent of its annual rainfall and snowfall during the monsoon, from June to September

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Monsoon Clouds,. Wikimedia
  • The study has found that the decline during the monsoon has been 1.22 per cent per decade on an average
  • IMD defines a rainy day as a day when total precipitation is 2.5 mm or more
  • According to the study, the number of rainy days is also declining during the monsoon season at an average rate of 0.23 days for every decade

June 12, 2017: The India Meteorological Department (IMD) has predicted that this year’s monsoon rainfall will be around 98 per cent of the long-period average, which is good news in this drought-prone era. But another study by the same IMD shows a more worrying trend. It has found that rain-bearing clouds have been thinning out across the country over the last 50 years.

The study, published in the IMD journal Mausam, shows that between 1960 and 2010, annual mean low cloud cover (responsible for the bulk of the rainfall) over India has been decreasing by 0.45 per cent per decade on average. Low clouds are declining over various seasons as well, the most significant one being during the monsoons. The study has found that the decline during the monsoon has been 1.22 per cent per decade on an average.

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India gets around 70 per cent of its annual rainfall and snowfall during the monsoon, from June to September.

According to the study, the number of rainy days is also declining during the monsoon season at an average rate of 0.23 days for every decade. This means that the country has lost approximately one rainy day over the last five decades. IMD defines a rainy day as a day when total precipitation is 2.5 mm or more.

“It is for the first time that low cloud cover has been studied in India, so it is a first-of-its-kind study,” A.K. Jaswal, retired scientist from IMD and leader of the study, told indiaclimatedialogue.net. “We have on an average lost one rainy day at each location that was studied across India, and that is of significance.”

As expected, the study found a strong correlation between low cloud cover and the number of rainy days. A thinning of this cloud cover also seems to lead to rising maximum temperature.

“Since monsoon season alone contributes to approximately 70 per cent of annual rainfall, the significant decrease in LCC (low cloud cover) as well as NRD (number of rainy days) in monsoon season during 1961-2010 obtained in this study is a cause of worry,” says the paper.

For the study, observations of cloud cover were made at 215 surface meteorological stations by trained observers who can distinguish low clouds from medium and high ones. Annual low cloud cover was found to have decreased at 61 per cent of the stations studied.

During the monsoon season, the thickest low cloud cover was recorded in 1961 (46.7 per cent), and the thinnest in 2009 (33.5 per cent).

The study found there has been an increase in the low cloud cover over the Indo-Gangetic plains and northeast India, while it has decreased over the rest of the country. The authors say more studies are needed to account for these regional differences.

Rainfall and temperature data was also obtained for all the stations to find out their correlations with the low cloud cover.

Around 60 per cent of the earth’s surface is covered by clouds. They play a critical role in weather and climate by reflecting sunlight, blocking outgoing longwave radiation and producing rain and snow, recycling water vapour and in global energy balance. Cloud cover variability is one of the most uncertain aspects of climate model predictions.

The study says, “At present, it is not known whether changes in cloudiness will exacerbate, mitigate, or have little effect on the increasing global surface temperature caused by anthropogenic greenhouse radiative forcing. Due to their high albedo, low clouds have cooling effect, whereas high clouds trap outgoing infrared radiation contributing to warming of earth’s surface.”

Given that agriculture in India is hugely dependent on monsoon rainfall, there is a strong case for learning to adapt to a thinning low cloud cover.

“We are seeing so many farmer suicides. Agriculture is in lot of stress. And farmers have to adapt to the changing climate by storing water through traditional methods, changing crop patterns, creating ponds to augment groundwater depletion,” said Jaswal.

The study found that while the number of rainy days is decreasing, there is not much change in the total amount of rainfall. This shows a trend towards shorter, heavier bursts of rain. That is bad news, because heavier raindrops can dislodge wheat and rice grains from their stalks. It also means rainwater flows down a slope that much faster instead of percolating underground.

Globally, various factors are being blamed for declining cloud cover — climate change, aerosols and other pollutants. But given the complexities of multiple factors impacting weather, more studies are needed to find the cause.

Though the study does say, “One factor causing decrease in low cloud cover may be the direct effect of aerosols. As aerosols can cool the earth’s surface by reflecting sunlight and warm the aerosol layer by absorbing downward longwave radiation, the lapse rate will decrease and atmospheric stability will increase, suppressing cloud formation and reducing the cloudiness.”

Jaswal however points out that in some studies in other parts of the world, it has been found that aerosols (which form the skeleton of the clouds) can also have a positive impact on the cloud cover. “I hope that someone will take up the logical second part of the study to see what kind of changes are happening within the low cloud cover itself,” he said. Wwhether stratus clouds are increasing or the non-rain making clouds are increasing in the low cloud cover.” (IANS)

Next Story

Students Worldwide Skip School to Protest Government’s Failure against Global Warming

They're angry at their elders, and they're not taking it sitting down

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global warming, climate change
Students from different institutions hold placards and banners as they participate in a climate protest in New Delhi, India, March 15, 2019. VOA

They’re angry at their elders, and they’re not taking it sitting down.

Students worldwide are skipping class Friday to take to the streets to protest their governments’ failure to take sufficient action against global warming.

The coordinated “school strikes,” being held from the South Pacific to the edge of the Arctic Circle, were inspired by 16-year-old Swedish activist Greta Thunberg, who began holding solitary demonstrations outside the Swedish parliament last year.

Since then, the weekly protests have snowballed from a handful of cities to hundreds, driven by social media-savvy students and dramatic headlines about the impact of climate change.

climate change, global warming
Students attend a protest ralley of the “Friday For Future Movement” in Berlin, Germany, March 15, 2019. VOA

Thunberg, who was recently nominated for the Nobel Peace Prize, was cheered for her blunt message to leaders at the World Economic Forum in Switzerland this year, when she told them: “I want you to panic. I want you to feel the fear I feel every day.”

Friday’s rallies are expected to be one of the biggest international actions yet. Protests were under way or planned in cities in more than 100 countries, including Hong Kong; New Delhi; Wellington, New Zealand; and Oulo, Finland.

In Berlin some 10,000 protesters, most of them young students, gathered in a downtown square, waving signs with slogans such as “There is no planet B” and “Climate Protection Report Card: F” before a march through the capital’s government quarter. The march was to end with a demonstration outside Chancellor Angela Merkel’s office.

Organizer Carla Reemtsma, a 20-year-old university student, said social media had been key in reaching people directly to coordinate the massive protests in so many different locations, noting that she was in 50 WhatsApp groups and fielding some 30,000 messages a day.

“It’s really important that people are getting together all over the world, because it’s affecting us all,” she said.

Critics, supporters

Some politicians have criticized the students, suggesting they should be spending their time in school, not on the streets.

“One can’t expect children and young people to see all of the global connections, what’s technically reasonable and economically possible,” said the head of Germany’s pro-business Free Democratic Party, Christian Lindner. “That’s a matter for professionals.”

climate change, global warming
Students hold signs during a rally for global climate strike for future in Seoul, South Korea, March 15, 2019. VOA

But scientists have backed the protests, with thousands signing petitions in support of the students in Britain, Finland and Germany.

“We are the professionals and we’re saying the young generation is right,” said Volker Quaschning, a professor of engineering at Berlin’s University of Applied Sciences.

“We should be incredibly grateful and appreciative of their bravery,” said Quaschning, one of more than 23,000 German-speaking scientists to sign a letter of support this week. “Because in a sense, it’s incredibly brave not to go to school for once.”

Scientists have warned for decades that current levels of greenhouse gas emissions are unsustainable, so far with little effect. In 2015, world leaders agreed in Paris to a goal of keeping the Earth’s global temperature rise by the end of the century well below 2 degrees Celsius (3.6 degrees Fahrenheit).

Yet at present, the world is on track for an increase of 4 degrees Celsius, which experts say would have far-reaching consequences for life on the planet.

“As a doctor, I can say it makes a big difference whether you’ve got a fever of 41 degrees Celsius (105.8 Fahrenheit) or 43 C (109.4 F),” said Eckart von Hirschhausen, a German scientist who signed the call supporting striking students. “One of those is compatible with life, the other isn’t.”

Other action

German Chancellor Angela Merkel and French President Emmanuel Macron have publicly welcomed the student protests, even as their policies have been criticized as too limited by environmental activists.

In France, activist groups launched legal action this week for failing to do enough to fight climate change, citing a similar successful effort in the Netherlands.

climate change, global warming
Hundreds of schoolchildren take part in a climate protest in Hong Kong, March 15, 2019. VOA

In Germany, environmental groups and experts have attacked government plans to continue using coal and natural gas for decades to come. Activists say that countries like Germany should fully “decarbonize” by 2040, giving less-advanced nations a bit more time to wean themselves off fossil fuels while still meeting the Paris goal globally.

Other changes needed to curb greenhouse gas emissions include ramping up renewable energy production, reining in over-consumption culture now spreading beyond the industrialized West and changing diets, experts say.

“The fight against climate change is going to be uncomfortable, in parts, and we need to have a society-wide discussion about this,” said Quaschning.

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That conversation is likely to get louder, with several U.S. presidential hopefuls planning to campaign on climate change.

Luisa Neubauer, one of the Berlin group organizing Fridays for Future, said politicians should take note of the young.

“For the European elections in May, we’re urging everyone to think about whether they want to give their vote to a party that doesn’t have a plan for the future and the climate,” she said. (VOA)