UV Workshop 2018

The 2018 edition of the ongoing series of NIWA UV Workshops, was held between 6 and 8 April, in Wellington New Zealand. Proceedings of the event, including a workshop summary, are now available here.


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Interview with Kim Hill

On the morning of Saturday 3 September 2016, I was interviewed by Kim Hill at Radio New Zealand. She is the master interviewer in New Zealand, and we had a lot of fun. We discussed optimal exposure times to achieve vitamin d sufficiency without getting sunburnt – which is to be avoided as it can be a precursor to the development of skin cancer. I emphasised that to make sensible decisions on this you need to know the UV index (UVI), which is now available in real time everywhere through the development of apps such as “uv2Day”  (restricted to the South Pacific region), and “GlobalUV”. The apps also give appropriate  behavioural advice based on the current UVI and the skin type. Both apps are available for free on iphone and android systems.  For more information, listen to the full interview (about 15 minutes long).

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Time to Make Climate Action Count

As published in the Mirror, and Stuff, Dec 2015

Tens of thousands of New Zealanders took to the streets last weekend to express their concern about climate change, and to show support for strong action at the Paris Sustainable Innovation forum (COP21). The action, part of a series of international marches co-ordinated by the environmental organisation 350.org, wasn’t confined to just the main centres. In Alexandra (population 5,000), where I was one of the march’s organisers, more than 125 people showed up at 9am on a Saturday to make their voices heard.


Intrepid marchers relaxing at the Courthouse Café in Alexandra.

The aim of 350.org is to ensure we leave our planet in good condition for our grandchildren. To do that, we need to limit the global temperature rise to no more than 2°C. To achieve that, we have to reduce the concentration of carbon dioxide in the atmosphere from its current level of 400 ppm to 350 ppm (hence 350.org) – still far above its pre-1950 level of 280 ppm. To meet the 350 ppm target, 80% of all the fossil fuel reserves that we know are still in the ground must stay there. To achieve that, we need to replace fossil fuels with renewables. And it needs to happen now.
On a per capita basis, New Zealand’s carbon footprint is among the world’s worst – it’s more than twice that of China, the world’s biggest polluter. Despite promises made in Kyoto, our net emissions soared by 42% between 1990 and 2013, second only to Turkey.
But we are well placed to make a difference. With over 70% of our electricity already from renewable sources, it would be easy to serve our remaining needs from solar energy without the need for any further capital investment from the government. The public will switch to solar anyway because the panels pay for themselves within a decade, but the transition needs to happen faster.
Any excess energy produced from small rooftop solar systems will go towards powering a new generation of electric vehicles that will inevitably replace the current fleet of petrol cars. Of course, multinational oil corporations such as Exxon Mobil will want to continue to slow down that transition, as they stand to lose billions. As recent reports have shown, they have known about the climate problem and its end-game for the last 25 years. But, rather than cut their profits, they instead responded with disinformation campaigns that have duped so many, stalling the needed transition. Unfortunately, our own government cannot escape similar conflicts of interest – it still owns 50% of our existing power stations, and it receives $800 million per year from oil and gas revenues.
Even with a strong commitment in Paris, the government will need mechanisms to implement it. A good place to start would be by shutting off subsidies for exploration and exploitation of fossil fuels. The government should also enforce a price on carbon, either via an Emissions Trading Scheme (ETS) or an emissions tax coupled with a credit for sequestration. Charging $50 per ton of carbon dioxide for all sectors of the economy would increase our petrol bills by $10 per 1,000 kilometres, but it would also provide a huge incentive to reforest the country. Together, these actions will simultaneously encourage smart personal choices, such as installing solar panels, insulating homes, or driving electric cars.
With the right attitude and commitment, we can ensure our grandchildren have a decent life on this planet, but we can’t continue down the path we’ve been treading. Last weekend, from Alexandra to Auckland, the people of New Zealand made their message clear: it’s time for serious climate action.


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Calculation of UVI for Smartphone Apps

The linked document Calculation-of-UVI-for-Smartphone-Apps (revised July 2017) describes in detail how the UV Index (UVI) is calculated in the recently released GlobalUV app.

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uv2Day available on iPhone

The uv2Day app is now available (for free!!) on iPhone as well as Android smartphones. Enjoy!!


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Climate March, Alexandra

Please follow the link below, and register.


The event will include a question and answer session, which will involve some of New Zealand top atmospheric research scientists, as well as any other concerned members of the public. I hope there will also be a media presence. By scheduling the event for 9 am on Saturday, I had hoped it would be the first one in the world, but I see a group in Auckland has beaten us to the punch by 1 hour. I’m hoping that after the meeting, we can adjourn for coffee at a nearby café. Please let me know if you can help with organising posters or banners. Also, please help by circulating this email in your contact circles, and through social media such Facebook and Twitter (where I am deliberately inactive).

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A friend and I have been working on a smartphone app (Uv2Day), which provides UV information for 

New Zealand, Australia, and the Pacific region …..

UVI App Icon14launch icon

The UV Index (UVI) is a measure of skin-damaging ultraviolet radiation. This App provides an estimate of the current UVI, and how it is expected to vary throughout this day at your current location (or at other selectable locations). Although small amounts of UV radiation are beneficial to health, overexposure can lead to skin cancer. New Zealand and Australia have the highest rates of skin cancer in the world, and the Cancer Societies of both countries recommend that you take protection whenever the UVI is greater than 3. The main determinant of UVI is the sun’s elevation angle, so UVI values are greatest in the summer, especially near solar noon (typically around 1:30 pm in the NZ summer). In winter, peak UVI values are generally less than 2, but in summer they can exceed 12. These peak values are about twice as high as in the UK, but the highest values in the world occur in the high altitude altiplano region of Peru, where they can exceed UVI=25. In New Zealand and Australia, UVI values are considered “extreme” when they exceed 10. For that UVI value, skin damage in fair-skinned people occurs in about 15 minutes, so it is important to take steps to protect yourself by avoiding direct sunlight, or by liberally applying a sunscreen with a high SPF factor to exposed skin.

Why do we need the app?
The app helps us to plan our daily activities to optimise sun exposure: to minimise the risk of sunburn (which is a risk factor for skin cancer) in summer, and to provide information on when it is safe to expose ourselves to sunlight in winter to help maintain sufficient levels of vitamin D. At present, this information is available only through the NIWA web pages. The only information provided by the media to the New Zealand public is the daily “alert period” (when the UVI exceeds 3), with no information about actual UVI values. Further, these alert periods are only provided during summer months. The app was developed in response to a request from a medical colleague who wanted to provide quantitative information on UVI levels for melanoma patients.


What does the App tells us?
The App provides current UVI values, and peak UVI values for the day, along with corresponding behavioural messages for the town nearest to the current location, as determined from a GPS fix. Corrections are applied to account for seasonal changes in Sun-Earth separation, and also for changes in altitude, mean aerosol optical depth, (and for surface reflectivity in the case of ski fields). Geographical coverage is currently limited to New Zealand, Australia, and the Pacific region, including Antarctica. Other locations with these regions can be selected with drop-down menus. A subsequent screen shows the variations in the clear-sky UVI forecast for the day, along with appropriate behavioural messages, using an interactive display. UV alert periods are displayed at the top of the graph. For locations that fall within the domain of NIWA cloud forecast model, cloudy sky forecasts are also provided. Warnings are issued if the forecast data are out of date.


 At present, the App is available only for Android phones at present. We are currently working with the Cancer Society of New Zealand to provide an iPhone version. The app, which is free, will be available soon on from iTunes. It may also be downloaded from here. Another UVI App, with global coverage, is also under development.

The UVI data used in this app are provided by NIWA. Clear-sky UVI values are calculated using a radiative transfer model. The ozone fields used as inputs to the model are forecasts that are based on global measurement from NOAA polar orbiting satellites. In the NZ region, estimates of UVI that include cloud effects are derived from a regional climate model that is run daily at NIWA.
For more information, see https://www.niwa.co.nz/our-services/online-services/uv-ozone. The app was developed by JGR Burke (jgrburke@gmail.com).

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