EDITED: Secret of the scent: MIT scientists figure out where earthy after-rain odor comes from

I could’ve EMBEDDED this video, but they wanted my PASSWORD
AND we’d probably start seeing ads from them here too

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Monday, January 19, 2015, 1:18 PM – It can be the best thing after a good summer rain: That rich, earthy smell that pervades the air.

It has a specific name, ‘petrichor’, but until recently the way it spreads has eluded scientists. Now, it seems, researchers at the Massachusetts Institute of Technology have at last unlocked the mystery, and it lies in aerosol generation.

In a new paper published in Nature Communications, the researchers took high-speed video of raindrop impacts on porous surfaces such as soil (the beautiful shots are in MIT’s video, above).

They found the raindrops, when striking the surface, trap tiny air bubbles beneath them, which then shoot back out in a fizz of tiny aerosols, possibly carrying the scent of earth with them, blown about by the wind.

But it can also carry soil-borne bacteria, and one of the report’s authors, Youngsoo Joung, told MIT News the new findings might explain how some diseases are spread.

“Until now, people didn’t know that aerosols could be generated from raindrops on soil,” Joung said. “This finding should be a good reference for future work, illuminating microbes and chemicals existing inside soil and other natural materials, and how they can be delivered in the environment, and possibly to humans.”

Oddly, the researchers’ findings noted more aerosols were released after light or moderate rain, rather than heavy rain.

Thanks to MJS

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weather

I LOVE this: image AND words;
I was cold going to the doctor’s yesterday – back in my winter coat, hat and gloves!

Thanks to JC

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Why It’s So Freakin’ Cold: Here’s the Science

https://ca.news.yahoo.com/why-freakin-cold-heres-science-000607036.html

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Monster Winter Storm Spotted from Space (Photo, Video)

https://ca.news.yahoo.com/monster-winter-storm-spotted-space-photo-video-004616456.html

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Nor’easters: What they are and how they form

Cold Arctic air meets warm Gulf Stream off coast of U.S. to create powerful storms

The storm expected to bring as much as 60 to 90 centimetres of snow from northern New Jersey to southern Maine is a nor’easter, a weather system commonly seen on the East Coast and known for bringing heavy precipitation and powerful winds.

The storms, so named because of the strong northeasterly winds that herald their arrival, can happen at any time of the year, but are more common and powerful between September and April. Along with the wind, rain and snow, nor’easters can lead to flooding and coastal erosion.

They can also cause power outages and travel chaos.

Thousands of flights were cancelled on Monday as the storm bore down on the East Coast.

Governors and mayors declared emergencies and ordered the shutdown of highways, streets and mass transit systems to prevent travellers from getting stranded and to enable plows and emergency vehicles to get through.

Nor’easters a ‘nasty event’

The storms usually head in a north or northeasterly direction along the U.S. East Coast and into Atlantic Canada. They typically form within 160 kilometres of the coast in an area stretching from Georgia to New Jersey.

Nor’easters typically form within 160 kilometres of the coast in an area stretching from Georgia to New Jersey.

“During winter, the polar jet stream transports cold Arctic air southward across the plains of Canada and the U.S., and eastward toward the Atlantic Ocean, as warm air from the Gulf of Mexico and the Atlantic tries to move northward,” according to a U.S. National Oceanic and Atmospheric Administration website detailing the dangers of nor’easters.

It is where these two systems meet that nor’easters are born, says David Phillips, senior climatologist with Environment Canada.

“When that warm, moist air from the south bumps into the cold air to the north — a low-pressure area meets a high-pressure area — wow, you get some strong winds,” said Phillips.

The warm, moist air from the Gulf Stream is forced upward by the denser, colder air, he said. As it rises, it cools and becomes precipitation.

“It really is a nasty event, because of the fact of the copious amounts of precipitation, and most of it looks like it’s going to be, because the cold air is so dominant, will be snow and not rain,” he said of the storm bearing down on the U.S. East Coast.

“So it was intensified, it got lots of moisture and energy from the ocean and then it carried on in its regular northeastern pattern,” he said.

‘Going to pile up very quick’

Nor’easters can be slow-moving storms, providing lots of time for significant precipitation.

“This could be five-centimetre-an-hour kind of snowfall, so it’s going to pile up very quick,” said Chris Murphy from The Weather Network.

Nor’easters can also be quite large, with a radius of up to 1,600 kilometres, according to a 2013 hazard mitigation plan from Massachusetts. Sustained wind speeds of 30 to 65 km/h are common, with gusts reaching between 80 and 95 km/h or higher.

A number of powerful nor’easters have struck the East Coast, and the current one could become of the one worst to hit the region since record keeping began in 1872.

The so-called “perfect storm” in 1991 caused almost $1 billion in damage, according to the NOAA.

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Environment Canada’s poetic weather alerts

http://www.cbc.ca/news/canada/british-columbia/environment-canada-s-poetic-weather-alerts-1.2890585

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Canada winter forecast: El Nino should keep polar vortex at bay

Warmer Pacific temperatures should mean a warmer winter than last year, forecaster predicts

Environment Canada is expecting the next three months to be average or warmer than normal in almost the entire country, thanks in part to El Nino, a senior climatologist says.

“The good news for all Canadians is that there’s no area of significant population where we’re showing colder than normal,” Dave Phillips told CBC News on Tuesday.

Environment Canada’s supercomputer in Montreal has run the numbers, and Phillips said that except for a small area around Lake Superior and part of Nunavut, the winter will be warm in contrast to last year’s — one of the longest and coldest on record.

• Find your regional weather
• The Weather Network’s take: another deep freeze for most of Canada
• What is a polar vortex?

Phillips said the forecast model for December, January and February shows warmer than normal temperatures from Vancouver Island almost to Lake Superior, including in Yukon and the Northwest Territories. Much of Atlantic Canada is also expected to be warmer than normal.

Ontario and Quebec are expected to have a more typical winter than last year — less consistent snow and cold, more abrupt weather changes from day to day.

The main reason for the warmer forecast is El Nino, the warming of Pacific sea-surface temperatures that occurs ever four to 12 years.

The Australian Bureau of Meteorology said Tuesday that temperatures in the Pacific have already exceeded the El Nino threshold, but measures of Pacific air pressure fluctuations have yet to breach it.

Or as Phillips puts it, the water and the atmosphere typically dance together. So far the atmosphere is shrugging the water off.

Polar vortex had ‘no predators’

The apparent arrival of El Nino increases the odds that the polar vortex will be less of a factor this winter — either keeping it in the north or making it less intense.

El Nino also makes the forecast more likely to be accurate — pushing its certainty from 60-something to as high as 80 per cent, Phillips said.

He said the forecast is useful to farmers or groups that need to plan responses to floods or forest fires, but that it would be unwise for anybody to bet the family farm on it.

Phillips said Environment Canada — whose one-day forecasts are 93 per cent accurate — could keep the relatively uncertain seasonal forecast to itself, but that Canadians love it.

“For the general public, my god, it is the most sought after thing,” he said. “They wait for it with bated breath. And what are they going to do with it? Nothing.”

Phillips said he remembers when the seasonal forecast involved people sitting in a room and hashing out a best guess based on previous winters. With improved data, he expects forecasting to continue to improve.

“The oceans can’t burp without us knowing about it now,” he joked.

The agency will never be able to do a daily forecast far into the future, but he said it should be able to fine-tune its seasonal forecasts to the point where there would be five possible categories, instead of the current three (below average, average, above average).

The Weather Network released its long-term forecast last week, predicting colder temperatures than Environment Canada is but less frigid temperatures than last winter. 

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