November 18, 2009
A UV Workshop will be held in Queenstown New Zealand between 7-9 April 2010. The meeting will be organised along similar lines to the previous workshops held in 2002 and 2006. Go here for more details. If you encounter difficulties downloading the “Registration Form” or the “Titles Received” from that site, they can alternatively be accessed from here. The draft program is also available here …
Registration form (pdf): UV Workshop Registration Form_v2
Registration form (doc): UV Workshop Registration Form_v2
Titles received to date: UV Workshop Titles for Web
Draft Programme : UV Workshop Programme
October 4, 2009
I’m happy to report that, according to the UV meter in my wrist watch, the UV Index at window seat 12A, with the sensor pointing towards the sun at 11 am on 4 October as we landed in Hong Kong this morning was, wait for it …… zero. I’d heard the aeroplane windows don’t tranmsit UV-B, but this was a nice confirmation. Though I doubt if the UVI outside was much above 3 anyway. The surface of the Earth was invisble from 30,000 feet. Still, I wouldn’t advise spending too long in the sun in HK. Far too hot, for one thing.
August 21, 2009
There’s been a lot of publicity about sunbeds in recent months. I used one once to see if it helped me to increase my vitamin D. Indeed it did. Sunbeds can also help give you a tan. But at what cost? They also increase your risk of sunburn, and skin cancer – and possibly other unknown effects. The trouble is that the spectrum of radiation that they emit is quite different from sunlight, which our skins have evolved to cope with. The UV-A component of sun beds (wavelengths from 315-400 nm), which is the part that makes your skin wrinkle, and which may also be implicated in melanoma, is several times brighter than ever occurs in natural sunlight. But the most scary thing about it is that there is a lot more dangerous UV-B radiation (wavelengths from 280-315 nm) that has been implicated in dna-damage and all forms of skin cancer.
The graph below compares the UV part spectrum of sunlight at mid-latitudes (45S) for midday in summer and winter with that from a typical sunbed. Note that it’s plotted with a logarithmic scale on the y-axis so you can see the differences in the UV-B region where intensities are much lower than in the UV-A region. The grey curve shows the relative importance of these wavelengths in causing sunburn. The curve is called the “erythemal weighting function” (“erythema” is just a fancy word for “skin reddening”). The shortest wavelengths shown are far more damaging than the longer wavelengths.
The graph below shows what happens when you weight the spectra above by multiplying them with this erythemal weighting function. The total erythemally-weighted UV is just the area under each of these curves, which is usually expressed in terms of the UV Index (UVI). The areas under the curve for winter sunlight corresponds to a UVI of about 1. The areas under the curves for summer sunlight and the sunbed are about the same, and correspond to a UVI of about 12. But the distribution of energy with wavelength is dramatically different. Who knows how our bodies are supposed to cope with such abuse?
August 17, 2009
Too much UV is bad for you. But so is too little UV. You can now estimate the time you should stay in the sun each day to receive adequate UV for vitamin D production, but without receiving so much UV that you get sunburnt. The optimum exposure time depends on the UV Index (UVI). It also depends on your skin type and how much of your skin you expose. At mid-latitude sites like the South Island of New Zealand the times range from less than 1 minute, if wearing swimming suits in summer when the UVI exceeds 10; to more than 3 hours if you’re rugged up in winter when the UVI is less than 1 . See this article for more details, including tips on how to estimate the UVI at any time.
August 17, 2009
The banner picture for this blog site is a panoramic photo taken from our place, showing several iconic Central Otago landmarks: the Shakey Bridge over the Manuherikea River, the Shakey Bridge Cafe and vineyard,the Alexandra hills with the Clock-on-the-hill, and the road winding around to Graveyard Gully. The distinctive Central Otago tree colours show that the photo was taken in the autumn – and it also shows cross which is erected near the clock each Easter. The photo was taken by my clever photographer brother Greg. He has plenty more pics here or here. A view from the other side of the river is shown here. Check out that site for more information about Alexandra, including the current weather conditions. Here’s why I live there.
August 10, 2009
UVI Display at the Alexandra Blossom Festival
Anybody out there interested in UV radiation? Take a look at the web site we set up at work that tells you all you need to know (if you happen to live in New Zealand or the South Pacific region that is). It includes definitions of UVI, climatolgies, measurements from the previous day, forecasts for tomorrow, and much much more ….
