UV index

[J07]

Hi all,

Today I was looking at the UV index, and apart from thinking "gosh that's high" and I started musing over records, and the effect of altitude.

If you look at the first photo, there's a cluster of three mountains at the bottom. The UV index for the nearest town is 13. UVI in NZ tends to be 40% greater than corresponding latitudes in the USA or Europe. This is for clear sky of course. I've also attached a "cloudy sky" UV forecast. I got these from www.sunsmart.org.nz and www.niwa.cri.nz/services/free/uvozone (both free for all).

For most areas cloud has not been having much effect.

Anyway, one of those cartoony mountains gets up to 2800m* , and at this time of the year, going up there is quite popular for serious climbers. There's also the most popular one-day walk in NZ which gets up to 2000m**, and in mid summer I expect it's like Oxford Street. You can bet your bottom dollar a number of people who go up there are not prepared for any mountain hazards, including high UV...as it is sold as an "easy" walk for everyone to do.

So, my question is, what sort of UV are these people exposing themselves to? Is there a simple way of calculating how it changes as you move upwards? Or even just an average approximation would be helpful. eg we can estimate lapse rate in the atmosphere under "normal" conditions to be between 0.6C and 1C....does something similar exist for UV?

This comes onto, what is the record UV index ever recorded? Wikipedia claims 17 for Carnarvon, Western Australia. I assume this is a sea level record. For an extreme example, surely if you go up the mountains in the northern Andes, you are going to be hit seriously hard.....even harder than 17 I would guess.

Or is there some kind of limiting factor on our planet which prevents the UV increasing without bound?

I suppose if we were looking for the place with the highest UV, it would be in the Southern Hemisphere, and at altitude. I would guess at the mountains of New Guinea.

Any input appreciated.

cheers

* Rumour has it that some people still think in "old money". I have looked this up and it is 9200 ft.

** Likewise about 6000 ft

[Supercell]

Hi,

I read in a Times column, a while back, that the highest levels of UV occur in Peru. I remember viewing this UV chart for Australia and seeing a 19 - http://www.bom.gov.au/weather/national/charts/UV.shtml

I sometimes look through the UV measurements in the UK to see what we can achieve in the summer months. http://www.hpa.org.uk/radiation/understand..._data/index.htm Camborne peaked at 9 a couple of years ago.

http://environment.newscientist.com/channe...-city-peru.html Found it...Cuzco, that's the one. A high of 25 where 300 000 people live up in the Peruvian andes.

Not too sure on all the calculations, sorry can't help you there. I have always just focused on the records.

[J07]

Hi,

I read in a Times column, a while back, that the highest levels of UV occur in Peru. I remember viewing this UV chart for Australia and seeing a 19 - http://www.bom.gov.au/weather/national/charts/UV.shtml

I sometimes look through the UV measurements in the UK to see what we can achieve in the summer months. http://www.hpa.org.uk/radiation/understand..._data/index.htm Camborne peaked at 9 a couple of years ago.

http://environment.newscientist.com/channe...-city-peru.html Found it...Cuzco, that's the one. A high of 25 where 300 000 people live up in the Peruvian andes.

Not too sure on all the calculations, sorry can't help you there. I have always just focused on the records.

Great links, thanks. The HPA site was good for a look, the sun really is extremely weak in the UK isn't it.

That reading of 25! :lol:

Wow....I can't imagine what that feels like. And, as you say, a decently populated area. Yikes.

On the subject, here is an interesting development:

Real-time UV Index display

First prototype at NIWA Lauder before installation at Alexandra swimming pool

Second prototype in use at the Goldrush Multisport Event in Central Otago

NIWA has developed a real time UV display in consultation with the Cancer Society and Sunsmart. The first prototype is currently installed at the new Molyneux Aquatic centre in Alexandra. Current UV intensities are sensed by a detector designed to measure the sun burning UV from the sun and sky that is incident on a horizontal surface. The signal is amplified and then displayed by means of servo technology that is used in model aircraft.

A large pointer displays the current intensity of UV, in terms of the internationally agreed UV Index scale. The scale is subdivided into 5 different regions corresponding to 5 different behavioural responses. For UVI values less than 3, the risk is “low” and the colour code is green. UVI values exceeding 10 are designated as “extreme” and colour-coded purple.

The display is solar powered, making it useful for outdoor sporting events (e.g., tennis, cricket, athletics, etc). We are seeking sponsors to cover the costs of calibrations. The UVI scale was originally used in Canada, where its maximum value was designed to reach 10. In New Zealand, the peak UVI can exceed 13 near midday in summer.

Basic units like the one shown here would cost about $3000. We are currently investigating other options including larger versions and double sided versions, and solar powered versions. All units would be offered with the option of an additional maintenance contract, which would include calibration of the display. All units would include the NIWA and Sunsmart logos, but there are spaces for two other advertisers (to effectively pay for the maintenance fee).

For more information please contact Dr Richard McKenzie at r.mckenzie@niwa.co.nz with a subject line containing the text “UVI Display”.

http://www.niwa.cri.nz/services/free/uvozone/uvi_display

Seems like a good idea to me. Who really checks the UV forecast before heading to the beach? To have something there it might perk people's attention to the danger....of course the onus would still be on them to act.

Edited January 30, 2008 by J07