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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