Quick Preview of this Month’s Contents

• Humbert and Humidity: Know Your Relatives!
• Tech Tips: Anemometer Cup or Spider Condo?
• It's Raining, It's Pouring, We are Definitely Not Snoring
• South Pole is a Moving Target
• Vantage Pro Draws Crowds at Maritime Museum
• You’re Brilliant! Answers to Quiz Questions
• Who You Gonna Call? Davis!

Humbert and Humidity: Know Your Relatives!
Some of you are still unclear on the concept of relative humidity. You seem to get it confused with another relative, Uncle Humbert. Uncle Humbert, who gets flustered easily and tends to perspire even when the air conditioner is set at 50°F, does remind us of relative humidity, so we understand your confusion. Just as Uncle Humbert's copious perspiration and cries of "Whoo-oo-eee, it is hot as Hades in here!" do not indicate the actual temperature in the room, relative humidity does not indicate the actual amount of water vapor in the air.

Instead, RH tells us how close the air is to being saturated. RH, which is what your weather station reports, is expressed as a percentage that indicates the amount of water vapor actually in the air compared to the amount of water vapor required for saturation at that particular pressure and temperature. Absolute humidity, on the other hand, is a measure of the actual water vapor density in a fixed volume of air - dewpoint is an indication of this.

Uncle Humbert, on a warm, muggy day is often heard to sigh, as he sits in the shade of his oak tree and mops his brow with a soggy handkerchief, "I don't mind the heat. I just can't take this goll-darned humidity." He is explaining the difference, in human terms, between relative and absolute humidity. When we are warm, we perspire. The moisture evaporates into the air and cools the skin. If the RH is low, this evaporation happens very quickly and we perceive a lower air temperature. But when the RH is high and the air is approaching saturation, evaporation slows or halts and we sense higher air temperatures. Uncle Humbert is right. With his very effective perspiration system, he would be more comfortable sitting in the shade of a cactus on an even warmer day in the desert!

Relative humidity changes during the course of a day, but not because the amount of water vapor in the air changes much. It is the changing of air temperature that changes RH. As the air cools, RH increases. As it warms, RH decreases.

But when Uncle Humbert waddles over to your thermostat and thumbs it far to the left, he effectively lowers the RH, not increases it! When the air conditioner cools the air, it increases its RH up to the point of saturation. The water vapor then condenses into liquid and drains out of the system. The cooled and dried air is then pumped into the house. In the winter, your heating system also dehumidifies the air. The cold arctic air outside has little water vapor. When this air is pulled into the house and heated, the vapor capacity of the air rises dramatically, and so the RH plummets. You end up with desert-dry conditions inside the house. Any perspiration evaporates very quickly, leading to the famous winter dry skin, scratchy throat, and dry mucus membranes.

So remember, while Uncle Humbert is a relative, he's not, we repeat, NOT, relative humidity

Weather Check Quiz Question 1: Bad news! Uncle Humbert has been admitted to the hospital suffering from heatstroke. "I can't imagine how it could happen," he tells us. "I was just napping in my hammock - the air temperature was just 88°F!" How could this happen to our favorite Uncle?

Extra Credit: If the air temperature and the dewpoint are equal, what is the relative humidity?

"I did try running piece of wire from the pole to the cross piece," Bill wrote. "This has lessened the problem but the spiders seem very intent on anchoring their web to the cups."

Our Technical Expert, Brett, tells us that Bill isn't the only one to discover that spiders just love those anemometer cups. (Personally, we can't imagine what they are thinking. We prefer our living rooms stationary!) Usually this is a spring-time woe, but maybe Bill's summer spiders are just more creative.

Regardless of whether spiders are bugging you or not, you should check your anemometer frequently. The cups should spin freely unless there is some friction causing them to slow down or stop. Remove the anemometer and clear out any bugs, debris, or webs. Then turn the shaft the cups attach to. If it seems gritty or stiff, give our Technical Support department a call at (510) 732-7814 or email them at support@davisnet.com.

Bill would like to hear of any spider-web solutions you have come up with. Let us know how you deal with the eight-legged interlopers!

Weather Check Quiz Question 2: We know a very brilliant arachnologist. He would be more popular if he didn't walk around with his pet tarantula, Tammie Sue, on his shoulder and even more popular if he wasn't a pathological liar. He told us the following stories about spider webs. Unfortunately, one is a big fat lie. Which one?
1. Spider silk has strong antibacterial properties. Studies show that wounds treated only with poultices of spider webs resulted in the same rate of infection and scarring as similar wounds that were cleaned, treated with topical antibiotics, and bandaged.
2. A cable of dragline spider silk as thick as a pencil could stop a 747 in mid-flight.
3. It won't be long before policemen wear light, bullet-proof vests made of man-made spider silk from the milk of Nigerian Dwarf goats.

It's Raining, It's Pouring, We are Definitely Not Snoring
Ben Faber's experience with a dramatic rain storm in Phoenix, AZ, has everybody watching their rainfall data. Alparslan Tansug read his August E-News to the pitter-patter of an Istanbul drenching. He reports that his rainstorm beat Ben's 8.5 inches/hour almost fourfold. His reading at 11:09 a.m. on August 17 was 36 inches/hour! Alparslan's data is on his website.

Gary Green was interested in Ben's data too, because he was watching the same microburst cell from his home in Scottsdale, just a mile or so east of Phoenix.

"I got far less rain while he got soaked," Gary reported. Gary told us that the area gets a lot of microburst activity in July and August, and the weather is highly localized. "That's the best reason I can think of to gather your own weather data," he said. He even posts his data to a website so he can monitor it from work throughout the day!

And, Ben, Gary disagrees with you about the "boring" weather in Phoenix! He wrote, "If it's not 66°F with 3% humidity, dewpoints of 75°F, or 41 mph winds (all of which I have recorded in the last four months), then it's catching your own microburst. It's not hurricane weather, but who wants that anyway?"

Meteorologist Jan Null chimed in with his favorite maximum rainfall data, that of 12 inches of rain in 42 minutes at Holt, MO in June 1947.

Another one of our favorite experts, retired atmospheric scientist G. David Thayer, told us that the one-minute rainfall record from Unionville, MD, on July 4, 1956 is probably one of the most-quoted weather records of all time.

"Unfortunately," he added, "it's also wrong." Apparently, a study done in the 1960's showed that the reading was the result of clogged funnel on the tipping bucket. The blockage suddenly cleared, allowing much more than one-minute's worth of rain to fall into the tipping bucket. David told us that the officially recognized one-minute rainfall record for the US is 0.80 inches, but he can't recall where it was recorded. (He thinks it was somewhere in Pennsylvania.)

David underscored the care we must take in looking at one-minute peaks. His own, personal 10-minute record for Salem, Oregon, was 0.33 inches (or a relatively modest 2 inches per hour), recorded by his Davis weather station during a November 1994 thunderstorm. He told us that one-minute peaks are typically some 10 times higher than peak 10-minute figures, "so one could estimate a maximum one-minute rate of about 20 inches per hour. Not too shabby!" Not too shabby at all, David.

Weather Check Quiz Question 3: G. David Thayer wrote that the highest recorded dew points were recorded in the Persian Golf, and went on to give us an excellent Weather Check Quiz question. "Back in the 50's and 60's, we were working with radiosonde data and had a station on Bahrain Island in the Persian Gulf. We were amazed to find rawinsonde traces showing temperatures close to 50°C and relative humidities of about 45%, which corresponds to a dewpoint around 35°C. These readings typically occurred near the top of shallow convective layers of air. Can the humidity at the top of such a layer exceed that near the surface?"

South Pole is a Moving Target
Mike Parker found that our story about Antarctica piqued his curiosity about just where the magnetic South Pole is.

"We've all seen at one time or another," he wrote, "a map showing the magnetic North Pole way up in northern Canada. But where is the magnetic South Pole? And is it exactly opposite (if you know what I mean) the magnetic North Pole?"

After a bit of mouse clicking, we can assure Mike that the geographic South Pole is on the Antarctic ice sheet, about 1230 km from the nearest coast. Since the ice on which it sits moves, the marker flag has to be repositioned annually. But that doesn't answer Mike's question about the magnetic South Pole, which is about 2,600 km from the geographic pole.

Here's what the British Antarctic Survey's informative website has to say:

"The magnetic South Pole was first reached during Shackleton's British Antarctic Expedition (1907-1909) by Professor Edgeworth David and Sir Douglas Mawson (Australian geologists) and Alistair Mackay who claimed the surrounding Victoria Land for the British Crown. At that time the magnetic pole lay within the Antarctic continent at latitude 71.6°S and longitude 152°E. Today it lies far out to sea at latitude 65°S and longitude 139°E and travels 10 to 15 km north-westerly each year. Electric currents and the rolling motion of the liquid iron core of the Earth dictate the position of the magnetic poles. The pole wanders daily in a roughly elliptical path around this average position, and may be as far as 80 km away from this position when the Earth's magnetic field is disturbed."

The site has a nice clear description of what happens when you hold a normal compass parallel to the ground as you approach the magnetic pole. Check it out before you sail off in search of the pole!


Vantage Pro Draws Crowds at Maritime Museum
Jerry Ostermiller calls the Colombia River Maritime Museum "the finest maritime museum on the west coast." As its Executive Director, we thought he might be a tiny bit prejudiced. But when he added that his museum uses its Davis Vantage Pro weather station in an interactive exhibit that draws thousands of visitors, we realized that this is a man who knows what he is talking about.

Located in Astoria, Oregon, on the mouth of the Columbia River, the museum "preserves and interprets the rich maritime heritage of the Pacific Northwest." The 40,000 square foot museum on seven acres of riverfront, recently celebrated its 40th anniversary. It annually welcomes over 100,000 visitors.

The museum's location couldn't be more dramatic. The museum boasts 10,000 square feet of glass which allow visitors to look out over the five-mile wide river. And right there on the dock, they'll see the spinning cups of the Vantage Pro's anemometer. Jerry told us that the Vantage Pro console, connected to a large flat screen display, is located in the Great Hall, and is one of the museums most popular exhibits.

The Columbia Maritime Museum's weather exhibit gives visitors a view of the river and the weather station. (Put on your strong glasses and look at the far right end of the dock. There's our Vantage Pro!)

"Visitors can look out at the river's white caps and watch the dials at the same time. They love it!" Jerry told us. "Many of our exhibits are more complicated, and we find that visitors, especially kids, gravitate to the weather station exhibit." Jerry is not really surprised by the interest museum visitors have in weather. A weather watcher since the fifth grade, Jerry still has his first Weather Wizard III. He has even installed a repeater for the Vantage Pro so he can keep a console on his desk at the museum.

Jerry said that while white caps and rain showers are frequent, more dramatic weather is also often served up by the river environment. "We get some hellacious storms off the Pacific," he said, with the enthusiasm of a true weather buff. "Hurricane force winds whip in from the sea at the headlands. We are 12 miles inland, so the winds usually calm down somewhat by the time they reach us, but those wind cups can really get moving."

The Columbia is the largest river in the Northwest, second nationally only to the Mississippi, and it is an artery to the Pacific Rim. Its important role in commercial shipping is underscored by the fact that Astoria, with its 10,000 citizens, is the oldest American settlement west of the Rockies. It was Astoria where Lewis and Clark ended their hike across the Northwest.

Jerry's good judgment was demonstrated again when he told us how much he appreciated the quality and price of his Vantage Pro. "I know good products when I see them, and the Vantage Pro is great stuff. And it was so affordable. We didn't have to work up a fundraising campaign or even write up a proposal to buy it."

Located just two hours from Portland, the museum itself was named among the top three in the nation. Jerry Ostermiller would love to show you their Vantage Pro, as well as over 7,000 artifacts and the lightship Columbia, a national monument.

"Come by sometime," he suggests. We think we may just take that suggestion. For now, be sure to check out the museum's website.

Weather Check Quiz Question 4: The Columbia River Basin drains a vast area, dumping an annual volume of 160 million acre feet of water into the Pacific. Its home in the Pacific Northwest is known for being a pretty watery place! But is Oregon the wateriest state? Where does it rank by percentage of the state that is covered in water? (We're not talking about rain or ocean here, just inland water, not including the Great Lakes.) Rank the following states by wateriest to driest: Arizona, Minnesota, New Mexico, Oregon, Rhode Island, and Texas. (From the US Geological Survey. See answer for link.)

You’re Brilliant! Answers to Quiz Questions

Question 1: Uncle Humbert, honey, it's not the heat, it's the humidity! The RH on that day was a very muggy 80%. That led to an apparent temperature of 105°F, which is hot enough to cause heatstroke with prolonged exposure and physical activity. (For Uncle, getting in that hammock is pretty extreme physical activity…)

Extra Credit: 100%. Dewpoint, by definition, is that temperature at which saturation occurs.

Question 2: If you get this right, Tammie Sue will give you a kiss on the nose. The fabrication is number one. Spider web is not particularly good for treating wounds. Story number two demonstrates the amazing strength of spider silk, which is even stronger than moth silk. It has a tensile strength of 300,000 pounds per square inch, is almost three times stronger than Kevlar, and 12 times as flexible. This leads to story number three, wherein our friend told us about Nexia, a Canadian company which, along with the U.S. Army, has genetically engineered some goats to produce spider silk in their milk. Apparently, the milk of ruminant animals is rather similar to spider silk. The milk the goats produce looks and tastes like normal milk, but the silk protein can be isolated and woven into a fabric. While the manmade silk is not quite as strong as the natural thing, goats are much easier to farm than cannibalistic, territorial spiders! Nexia hopes to use the stuff they call Bio-Steel® for sutures, prosthetic ligaments and bullet proof vests. Nexia's website will tell you all you want to know about the subject. And a click here will get a very cool, very close-up picture of spinnerets doing their thing.

Question 3: Yesiree, says David, and here's why. Water vapor, with a molecular weight of 18, is considerably lighter than dry air, which is a mixture of molecular oxygen (m.w. 32) and nitrogen (m.w. 28). As a result, parcels of humid air are lighter than parcels of drier air, and thus rise faster than the drier ones. This results in the humidity becoming concentrated near the top of the convective layer. David added this afterthought: "Needless to say, Bahrain Island is one of the most hideously hot and humid places in the world!"

Question 4: Little Rhode Island comes in first of all 50 states with 13.0% water. Then comes Minnesota in 8th place with 5.8%; Texas in 29th with 1.8%; Oregon is way down in 40th position at 0.9%; and Arizona and New Mexico come in dead last at 0.4% and 0.2% respectively. Source: The United States Geological Survey's Water Science for Schools.

Who You Gonna Call?
Each month after the E-News goes out, we receive messages back. Sometimes the messages are in response to a story we shared; other times they are a request for help of some kind. We read all the emails, answer those we can, and pass the rest on to the appropriate departments.

We think you should know, though, that if you're interested in the fastest possible reply, news@davisnet.com may not be the best place to send your message. Questions about how things work should be addressed to tech support directly at support@davisnet.com. For general information about the products, such as how much cable comes with a station contact sales@davisnet.com. To request a catalog, you’ll find links for catalog requests on our web site at http://www.davisnet.com/contact/catalog.asp

Please continue to send your comments, weather URLs, and story suggestions to news@davisnet.com. We look forward to getting your comments and any responses you have to the E-News. Member participation is what keeps the E-News alive and kicking.

Well, that’s it for this edition. You’ll be hearing from us again next month!


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