Thursday, July 14, 2011
Aircraft punch holes in clouds, leave snow in their wake
We've seen recently that air travel can have an oversized impact on the atmosphere, at least relative to emission of things like greenhouse gasses, because they seed clouds that can persist for hours. Now, researchers have taken a detailed look at what happens when aircraft fly through clouds that already exist. Under many circumstances, it turns out that the aircraft have the opposite effect, causing pressure changes that trigger the formation of large holes in the cloud, with the missing water falling out as snow.
Holes in clouds, like the one shown above, have been associated with the passage of aircraft since the 1940s, but it hasn't been clear how significant this process is. By the 1980s, researchers had found that propeller-driven aircraft produce large pressure changes in their wake, which produce a lot of ice crystals if they pass through supercooled clouds. More recent work showed just how large this effect can be: propellers can induce temperature drops of up to 30°C, while the wings of jets can lower the temperature by 20°C. If a cloud is already in the area of -10 to -20°C, that means the airplane should cause ice to crystalize out of clouds.
The new paper shows what happens as a result of these crystals. Modeling indicates that the heat released by ice formation causes an updraft in the immediate vicinity of where an aircraft passes. This carries most of the ice crystals back upward, with the exception of the heaviest, which fall through the updraft as snow. On the periphery of the updraft, a corresponding downdraft causes evaporation of the water in the cloud, which gradually expands the hole. This self-sustaining cycle should cause the hole to expand for up to an hour after the aircraft passes, and vastly expands the area affected by the aircraft's passage.
The researchers looked at satellite and radar imagery to see whether they could spot the equivalent of what their model was showing. Could they ever. Radar near a Denver airport showed lines of snow formation that followed curved paths typical of airliners. Clouds over the continental US showed extended trains of holes and channels that followed flight paths verified on air transportation records. "Some holes reached lengths of >100 km and were detected for four or more hours," the authors note. From the point where they were detected on radar, the holes would double their area within a half hour, and continued to expand out to a full hour.
The authors don't expect that the formation of snow is significant enough to do much more than cause small amounts of localized snow in the immediate vicinity of the airport. But the satellite imagery suggests that heavy air travel can cause a measurable drop in the total area covered by clouds under the right conditions. Along with the earlier results, the new work indicates that, although aircraft only disturb a small area of the atmosphere, the disturbances they cause can persist and propagate long enough to have an unexpectedly large impact on our planet.
When looking over recent statistics, it may seem as if the economy is improving. But some experts say those stats are misleading, and there's more to the story as to why home foreclosure filings are declining.
Foreclosures come in all shapes and sizes, and for buyers, they're a bargain. “Bank owned properties are priced to sell. They want multiple offers in the first week, they want to sell within 30-60 days, and they want to be the lowest price on the market for what's similar,” says Brooke O'Malley, Owner/Broker at Club Realty.
O'Malley says the Suncoast's housing market is actually quite good. “We're at about a 6 month inventory, which is a very healthy market. We're running into multiple offer situations across the board, in all price ranges, probably about 80% of the time.”
In Sarasota County, only 236 home foreclosures were filed last month, compared to 364 in June 2010. But despite those encouraging numbers, Judge Lee Haworth, who is the Administrative Judge over foreclosure cases, says that news isn't so good. “The cases are not able to get through the court system, so they can be put back into inventory, and that's really one of the issues we're struggling with.”
State funding ran out, and the Rocket Docket, which expedited foreclosure proceedings, ended last month. Judge Haworth says that will stagnate cases. “Before we could get a hearing time 30-40 days out pretty easily, because we had the 3 judges and the 4 case managers to process the paper and get things ready. We don't have them anymore, so that means we're looking at 3-4 months out to get those cases resolved.”
O'Malley says in the end, that could hamper the progress the housing market has made. “Over the time the prices have come down more and more than they may have if they would have just foreclosed quickly.”
Judge Haworth and the Chief Judge plan to approach lawmakers in our area to request additional support for the programs needed to process the foreclosure filings. In the meantime, Judge Haworth is putting on free seminars for homeowners who need help with foreclosures. The next “Hope for Homeowners” seminar is on Saturday at the Venice Community Center.