The heat is on: It’s rock and roll in the skies
12 Aug 2007, 0040 hrs IST,Shobha John ,TNN
t could well be a harbinger of things to come. Increasing storms, violent thunderclaps, greater wind speeds — the din unleashed in the heavens by the weather gods between April and September (pre-monsoons to end of season) over the last two-three years has surprised and alarmed even veteran aviators. And as they struggle to steady their big metallic birds and stay calm lest it unnerve their passengers, the niggling question on their minds is: Are these severe climatic changes a sign of global warming? Scientists, in fact, predict that global warming is ominously near and will be greater after 2009.
“It’s been a rock and roll up there, especially during the last 2-3 monsoons,” says a veteran commander. If it rains, aircraft get lashed more furiously. If there are sharp winds, they’re more cutting. Calicut airport is an ideal example. “My plane is buffeted so violently by crosswinds, it’s difficult to control it. It’s like a ship in stormy seas. It wasn’t like this before. Wind speeds during approach can sometimes go up to 65-70 kmph as against the normal of 35-40 kmph,” he says.
INTENSE STORMS: Arthur M Greene, associate research scientist, International Research Institute for Climate and Society, the Earth Institute, Columbia University, says via email, “There are theoretical grounds to expect that storms may become more intense (producing more rainfall) in warmer climates. Studies have confirmed this, at least in mid-latitudes.”
Are these signs of global warming? Akhilesh Gupta, scientific adviser, minister for science and technology, says, “Global warming shows up in extreme weather conditions, including heavy rainfall. While monsoon rainfall in our country hasn’t shown a decline, certain pockets in central and western India have witnessed increase in heavy rainfall, but a decrease in the number of rainy days. These include Chhattisgarh, MP, Konkan and Gujarat.” And no, Mumbai’s 2005 floods weren’t part of this phenomenon. “Other areas in India such as Lakshadweep and HP have received that much rainfall too — 94.4 cm,” he says.
These climatic changes have also been recorded by R K Jenamani, director, Met Office, Indira Gandhi International Airport, Delhi. In a recent study published in Current Science, he says that while sulphur content is controlled in Delhi’s atmosphere, nitrous oxide and SPM (suspended particulate matter) isn’t. This, coupled with increased moisture content due to irrigation in Haryana and Punjab, has led to increase in frequency and intensity of fog. “Pilots in the mid 1960s faced visibility greater than 5 km for 17 hours daily in winter. Now, it’s almost nil. In January, one hardly gets a visibility of over 2 km. Fog hours (visibility less than 800 m) have gone up 20-30 times since the mid-60s from 20 minutes average per day to 10.3 hours daily, severely disrupting flight operations,” he says.
Incidentally, the aviation industry is seen as one of the main contributors of increasing pollutants and global warming.
THIS IS UNTIMELY: Even pilots flying trans-continental have found extreme weather changes in the last few years. Says a 747 pilot with AI, “Surface weather (on the ground) has been extreme and untimely in many places and 90% of accidents occur during take-off and landing. So we had rainfall and very cold weather in April-May in Frankfurt, Paris and London, along with low visibility — that’s very unusual.” The intensity of snowfall too in New York, Chicago, Paris and London, has been more. “Strong winds, irrespective of the season, have increased by 5-10 knots,” he says. An auto landing is generally done then.
Gupta says the increase in number and intensity of weather events has been gradual over the last 25 years. “The last 17 years, in fact, have been the warmest in the whole century,” says Gupta. The warmest 12 have been: 1990, 1995, 1997, 1998, 2000, 2001-06. In the Atlantic Ocean, for example, there’s been an increase in hurricanes. “Statistics show there’s been a slight increase in tropical cyclones in the Indian region too, especially between October-December over the last 25 years. The number of heat waves too has increased, while frost days and cold waves have declined,” he says.
An international study, he says, found that global warming leads to increased number of tropical cyclones due to increase in sea surface temperature. Due to this, vertical sheer of wind increases, leading to turbulence during flights. Vertical sheer is the difference in temperature and other environmental factors between one layer and another.
Veteran pilots know how to avoid the turbulent patches, seen as red and amber on their radar screens. “If the red patch is say, over 10 miles, we ask for a deviation of 20-30 miles, left and right,” says Capt Rajiv Kothiyal, chief pilot, Air Deccan.
RECIPE FOR DISASTER?: And these extreme conditions, coupled with wet, slippery and short runways are a sure-fire recipe for disaster. Is it any wonder then that between May and July this year, some five planes overshot runways or skidded on them? “Airports which have short runways (less than 7,000 ft for an A-320) include Indore, Bhopal, Patna, Jammu, Madurai, Agartala and Dibrugarh,” explains a commander. Restrictions are also imposed on co-pilots during monsoons; they’re not supposed to land and take-off, especially on a wet runway. Training is restricted to simulators.
Even dare-devil pilots admit sheepishly they now prefer to avoid places such as Kolkata and N-E as monsoon activity is more violent and severe there. “Despite 25 years of experience, I’m not too comfortable flying there. I would prefer to give these places a miss,” says another commander. Anyway, there are limits under which a plane can land, says Kothiyal. “Crosswinds of over 20 knots should be avoided by A-320s,” he says. “We divert then.”
Extremes in summer too affect planes. Delhi saw a temperature of 48 degree centigrade this summer. “Increased temperatures in future would affect the efficiency of planes; payload gets restricted as engines get more stressed,” says a commander. “In fact, 48 degrees even crosses the limit set by manufacturers of planes. At such high temperatures, flights are stopped. Refuelling too is delayed till the last minute as fuel temperatures go up faster and this can be dangerous.”
So what’s the way out? “Junk old, fuel-inefficient planes,” stresses P R P Rao, aviation advisor, Mumbai airport. “As the burnout of fuel is incomplete in them, they emit carbon-di-oxide and nitrous oxide fumes.”
Boeing’s 787 Dreamliner, in fact, shows the green way. It uses 20% less fuel and pumps out fewer greenhouse gases. It uses high-tech plastic composites instead of aluminium and upto 50% of the structure is made of carbon fibre, making it stronger and lighter, leading to greater fuel efficiency. Talk about a lean, mean, green machine.