A. Heikkilä

• PhD
• Senior Researcher at Finnish Meteorological Institute

The protection of Earth’s stratospheric ozone (O 3 ) is an ongoing process under the auspices of the universally ratified Montreal Protocol and its Amendments and adjustments. A critical part of this process is the assessment of the environmental issues related to changes in O 3 . The United Nations Environment Programme’s Environmental Effects Ass...

This Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) considers the interactive effects of solar UV radiation, global warming, and other weathering factors on plastics. The Assessment illustrates the significance of solar UV radiation in decreasing the durability of plastic ma...

The deleterious effects of solar ultraviolet (UV) radiation on construction materials, especially wood and plastics, and the consequent impacts on their useful lifetimes, are well documented in scientific literature. Any future increase in solar UV radiation and ambient temperature due to climate change will therefore shorten service lifetimes of m...

We modelled the impact of selected meteorological factors on the daily number of new cases of the coronavirus disease 2019 (COVID-19) at the Hospital District of Helsinki and Uusimaa in southern Finland from August 2020 until May 2021. We applied a DLNM (distributed lag non-linear model) with and without various environmental and non-environmental...

The Environmental Effects Assessment Panel of the Montreal Protocol under the United Nations Environment Programme evaluates effects on the environment and human health that arise from changes in the stratospheric ozone layer and concomitant variations in ultraviolet (UV) radiation at the Earth’s surface. The current update is based on scientific a...

This study introduces an Earth observation (EO)-based system which is capable of operationally estimating and continuously monitoring the ultraviolet index (UVI) in Europe. UVIOS (i.e., UV-Index Operating System) exploits a synergy of radiative transfer models with high-performance computing and EO data from satellites (Meteosat Second Generation a...

The Montreal Protocol and its Amendments have been highly effective in protecting the stratospheric ozone layer and preventing global increases in solar ultraviolet‐B radiation (UV‐B; 280‐315 nm) at Earth’s surface (McKenzie et al., 2019). This international agreement has also been one of the most important societal actions to mitigate global warmi...

An empirical model of global solar irradiance (EMGSI) under all sky conditions was developed by using solar radiation and meteorological parameters at Sodankylä. The calculated hourly global solar irradiance is in agreement with that observed at the ground during 2008–2011 and at the top of the atmosphere (TOA). This model is used to calculate the...

Large-scale retrievals of the Ultraviolet Index(UVI) in real-time by exploiting the modern Earth Observation data and techniques, are capable of forming operational early warning systems that raise awareness among citizens of the health implications of high UVI doses. To this direction a novel UVI operating system, the so called UVIOS, was introduc...

This assessment by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) provides the latest scientific update since our most recent comprehensive assessment (Photochemical and Photobiological Sciences, 2019, 18, 595–828). The interactive effects between the stratospheric ozone layer, solar ultraviolet...

The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite was launched on 13 October 2017 to provide the atmospheric composition for atmosphere and climate research. The S5P is a Sun-synchronous polar-orbiting satellite providing global daily coverage. The TROPOMI swath is 2600 km wide, and the ground resolut...

Plants rely on spectral cues present in their surroundings, generated by the constantly changing light environment, to guide their growth and reproduction. Photoreceptors mediate the capture of information by plants from the light environment over a wide range of wavelengths, but despite extensive evidence that plants respond to various light cues,...

The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite was launched on 13 October 2017 to provide the atmospheric composition for atmosphere and climate research. The S5P is a sun-synchronous polar-orbiting satellite providing global daily coverage. The TROPOMI swath is 2600 km wide, and the ground resolut...

This assessment, by the United Nations Environment Programme (UNEP) Environmental Effects Assessment Panel (EEAP), one of three Panels informing the Parties to the Montreal Protocol, provides an update, since our previous extensive assessment (Photochem. Photobiol. Sci., 2019, 18, 595–828), of recent findings of current and projected interactive en...

Microplastics (MP) are defined as “any synthetic solid particle or polymeric matrix, with regular or irregular shape and with size ranging from 1 μm to 5 mm, of either primary or secondary manufacturing origin, which are insoluble in water”.

Changes in stratospheric ozone and climate over the past 40-plus years have altered the solar ultraviolet (UV) radiation conditions at the Earth’s surface. Ozone depletion has also contributed to climate change across the Southern Hemisphere. These changes are interacting in complex ways to affect human health, food and water security, and ecosyste...

Solar UV radiation adversely affects the properties of organic materials used in construction, such as plastics and wood.

Measurements of diffuse erythemally weighted UVB radiation were started in Helsinki, Finland, in March 2017, to collect experimental evidence on the potential of shades in reducing human exposure to harmful solar UVB radiation. The data produced by the setup over the first 17 months of measurements are reported. Combined with the on-site measuremen...

Non-ideal angular response of a spectroradiometer is a well-known error source of spectral UV measurements and for that reason instrument specific cosine error correction is applied. In this paper, the performance of the cosine error correction method of Brewer spectral UV measurements in use at the Finnish Meteorological Institute (FMI) is studied...

Evergreen plants in boreal biomes undergo seasonal hardening and dehardening adjusting their photosynthetic capacity and photoprotection; acclimating to seasonal changes in temperature and irradiance. Leaf epidermal ultraviolet (UV)-screening by flavonols responds to solar radiation, perceived in part through increased ultraviolet-B (UV-B) radiatio...

At high northern latitudes in the boreal forest, winter precipitation in the form of snow has decreased and is predicted to continue to do so in the future (Jylhä et al., 2008). Reduced snow cover exposes plants to temperature fluctuations at may delay the spring recovery of photosynthesis. Such a change has potentially negative consequences for ne...

The TROPOspheric Monitoring Instrument (TROPOMI) is the only payload of the Sentinel-5 Precursor (S5P), which is a polar-orbiting satellite mission of the European Space Agency (ESA). TROPOMI is a nadir-viewing spectrometer measuring in the ultraviolet, visible, near-infrared, and the shortwave infrared that provides near-global daily coverage. Amo...

The Environmental Effects Assessment Panel (EEAP) is one of three Panels of experts that inform the Parties to the Montreal Protocol. The EEAP focuses on the effects of UV radiation on human health, terrestrial and aquatic ecosystems, air quality, and materials, as well as on the interactive effects of UV radiation and global climate change. When c...

The performance of the cosine error correction method used at the Finnish Meteorological Institute (FMI) for correcting spectral UV measurements of the Brewer spectroradiometer (Brewer) was studied. An instrument specific cosine error correction has to be applied due to the non ideal angular response of the Brewer. The correction depends on the act...

A new method has been developed to estimate the global and direct solar irradiance in the UV-A and UV-B at ground level in cloud-free conditions. It is based on a resampling technique applied to the results of the k-distribution method and the correlated-k approximation of Kato et al. (1999) over the UV band. Its inputs are the aerosol properties a...

Spectral measurements of global UV irradiance recorded by Brewer spectrophotometers can be significantly affected by instrument-specific optical and mechanical features. Thus, proper corrections are needed in order to reduce the associated uncertainties to within acceptable levels. The present study aims to contribute to the reduction of uncertaint...

The UV Index was established more than 20 years ago as a tool for sun protection and health care. Shortly after its introduction, UV Index monitoring started in several countries either by newly acquired instruments or by converting measurements from existing instruments into the UV Index. The number of stations and networks has increased over the...

A new method has been developed to estimate the global and direct solar irradiance in the UV-A and UV-B, at ground level in cloud-free conditions. It is based on a resampling technique applied to the results of the k-distribution method and the correlated-k approximation of Kato et al. (1999) over the UV band. Its inputs are the aerosol properties,...

The TROPOspheric Monitoring Instrument (TROPOMI) is the only payload of the Sentinel-5 Precursor (S5P), which is a polar orbiting satellite mission of the European Space Agency (ESA). TROPOMI is a nadir-viewing spectrometer measuring in the ultraviolet, visible, near-infrared and the shortwave infrared that provides near-global daily coverage. Amon...

UV Index is a measure for UV radiation harmful for the human skin, developed and used to promote the sun awareness and protection of people. Monitoring programs conducted around the world have produced a number of longterm time series of UV irradiance. One of the longest time series of solar spectral UV irradiance in Europe has been obtained from t...

We report on a study focusing on UV exposure conditions in three different types of chambers used for accelerated ageing of materials. The first chamber is equipped with four 300-W UVA/UVB mercury vapour lamps (Ultra-Vitalux/Osram). The second chamber uses four 40-W UVA fluorescent lamps (QUV-340/Q-Lab). The third chamber is Weather-Ometer Ci3000+...

UV Index is a measure for UV radiation harmful for the human skin, developed and used to promote the sun awareness and protection of people. Monitoring programs conducted around the world have produced a number of long-term time series of UVirradiance. One of the longest time series of solar spectralUVirradiance in Europe has been obtained from the...

At Sodankylä (67°N), spectra of solar ultraviolet radiation (UVR) have been measured with a Brewer spectroradiometer since 1990. The time series is one of the longest in the European Arctic region. In this work, the time series 1990-2014 was homogenized, and the data were corrected with respect to known error sources using laboratory characterizati...

This study examines the adequacy of the existing Brewer network to supplement other networks from the ground and space to detect SO2 plumes of volcanic origin. It was found that large volcanic eruptions of the last decade in the Northern Hemisphere have a positive columnar SO2 signal seen by the Brewer instruments located under the plume. It is sho...

The two Brewer spectrophotometers of the Finnish Meteorological Institute at Jokioinen and Sodankylä have been operated according to the highest levels of the WMO∕GAW (World Meteorological Organization∕Global Atmosphere Watch) recommendations with rigorous quality control and quality assurance. The calibration of the instruments is based on annual...

Databases gathering atmospheric data have great potential not only as data storages but also in serving as platforms for coherent quality assurance (QA). We report on the flagging system and QA tools designed for and implemented in the European UV DataBase (EUVDB; http://uv.fmi.fi/uvdb/) for measured data on solar spectral UV irradiance. We confine...

This paper demonstrates that SO2 columnar amounts have significantly increased following the five largest volcanic eruptions of the past decade in the Northern Hemisphere. A strong positive signal was detected by all the existing networks either ground based (Brewer, EARLINET, AirBase) or from satellites (OMI, GOME-2). The study particularly examin...

The data flow involved in a long-term continuous solar spectral UV irradiance monitoring program is investigated and structured to provide an overall view on the multiphase process from data acquisition to the final products. The program employing Brewer spectrophotometers as measuring instruments is maintained by the Finnish Meteorological Institu...

Soot has a pronounced effect on the cryosphere and experiments are still needed to reduce the associated uncertainties. This work presents a series of experiments to address this issue, with soot being deposited onto a natural snow surface after which the albedo changes were monitored. The albedo reduction was the most pronounced for the snow wi...

We have developed an ultraviolet (UV) ageing facility consisting of a spectrograph which can be used to expose material samples with spectrally dispersed UV radiation at the wavelength range 273 – 423 nm, and an automated, high-resolution laser-based setup for measuring the induced color changes in the transmittances of the exposed samples. The sam...

The two Brewer spectrometers of the Finnish Meteorological Institute at Jokioinen and Sodänkylä have been maintained and calibrated according to the highest levels of the WMO/GAW recommendations, with rigorous quality control and quality assurance. However, the WMO/GAW recommendations are ambiguous on a number of decisions which need to be made whe...

We describe the steps that are used at the Finnish Meteorological Institute (FMI) to process spectral ultraviolet (UV) radiation measurements made with its three Brewer spectrophotometers, located in Sodankylä (67° N) and Jokioinen (61° N). The spectrum is measured many times a day, following a pre-programmed schedule. Multiple corrections are made...

Databases gathering atmospheric data have great potential not only as data storages but also in serving as platforms for coherent quality assurance (QA). We report on the flagging system and QA tools designed for and implemented in the European UV DataBase EUVDB (http://uv.fmi.fi/uvdb/) for measured data on solar spectral UV irradiance. Spectra sca...

Databases gathering atmospheric data have great potential not only as data storages but also in serving as platforms for coherent quality assurance (QA). We report on the flagging system and QA tools designed for and implemented in the European UV DataBase (EUVDB; http://uv.fmi.fi/uvdb/) for measured data on solar spectral UV irradiance. We confine...

Polystyrene and many other materials turn yellow when exposed to ultraviolet (UV) radiation. All photodegradation mechanisms including photoyellowing are functions of the exposure wavelength, which can be described with an action spectrum. In this work, a new high-resolution transmittance measurement setup based on lasers has been developed for mea...

The Dutch-Finnish Ozone Monitoring Instrument (OMI) on board NASA's Aura spacecraft provides estimates of erythemal (sunburning) ultraviolet (UV) dose rates and ery-themal daily doses. These data were compared with ground-based measurements at 13 stations located throughout the Arctic and Scandinavia from 60 to 83 • N. The study 5 corroborates resu...

The Dutch–Finnish Ozone Monitoring Instrument (OMI) on board NASA's Aura spacecraft provides estimates of erythemal (sunburning) ultraviolet (UV) dose rates and erythemal daily doses. These data were compared with ground-based measurements at 13 stations located throughout the Arctic and Scandinavia from 60 to 83° N. The study corroborates results...

Light-absorbing impurities affect snow and ice via a decrease in albedo and a consequent disturbance to the radiative energy balance. Experimentally, these matters have only been examined in a few studies. Here we present results from a series of experiments in which we deposited different soot concentrations onto natural snow in different 5 region...

This study analyzes changes in solar ultraviolet (UV) irradiances at 305 and 325 nm at selected sites located at high latitudes of both hemispheres. Site selection was restricted to the availability of the most complete UV spectroradiometric datasets of the past twenty years (1990–2011). The results show that over northern high latitudes, between 5...

Greatly increased levels of ultraviolet (UV) radia-tion were observed at thirteen Arctic and sub-Arctic ground stations in the spring of 2011, when the ozone abundance in the Arctic stratosphere dropped to the lowest amounts on record. Measurements of the noontime UV Index (UVI) dur-ing the low-ozone episode exceeded the climatological mean by up t...

The link between stratospheric ozone decline and ultraviolet (UV) radiation increase at the Earth's surface is well established. In the Northern Hemisphere extratropics, stratospheric ozone is accumulated from autumn to spring as a result of transport from its source region in the tropics. The amount of accumulated ozone varies from year to year du...

For the first time in serveral years, the El Nino-Southern Oscillation did not dominate regional climate conditions around the globe. A weak La Ni a dissipated to ENSOneutral conditions by spring, and while El Nino appeared to be emerging during summer, this phase never fully developed as sea surface temperatures in the eastern conditions. Neverthe...

Greatly increased levels of ultraviolet (UV) radiation were observed at thirteen Arctic and sub-Arctic ground stations in the spring of 2011 when the ozone abundance in the Arctic stratosphere dropped to the lowest amounts on record. Measurements of the noontime UV Index (UVI) during the low-ozone episode exceeded the climatological mean by up to 7...

A Brewer spectrophotometer MK II measures UV irradiances since 1990 at Sodankylä (67.4°N, 26.6°E), Finland. In this work, the observed spectral features of the time series 1990-2011 are studied. The data have been corrected for temperature, cosine, noise spike and the wavelength-shift. The long-term spectral responsivity is scaled to the irradiance...

Improved methodology for deriving action spectrum of photoyellowing induced by UV radiation on a polymeric material is reported. Facility designed and constructed for exposing materials with narrow-band UV radiation has been used for ageing newspaper samples for time periods of 1, 2, 4, and 8 h. Radiometric characterization of the facility has been...

Greatly increased levels of ultraviolet (UV) radia-tion were observed at thirteen Arctic and sub-Arctic ground stations in the spring of 2011, when the ozone abundance in the Arctic stratosphere dropped to the lowest amounts on record. Measurements of the noontime UV Index (UVI) dur-ing the low-ozone episode exceeded the climatological mean by up t...

Quantification of material degrading solar UV radiation exposure is an issue insufficiently and controversially handled in the field of outdoor material testing thus far. A majority of the experiments rely on broadband estimates of exposing UV doses, despite the knowledge on vast spatial and temporal differences in spectral distribution of solar UV...

This study examines the long-term variability of UV solar irradiances at 305 nm and 325 nm over selected sites in Canada, Europe and Japan. Site selection was restricted to the availability of the most complete UV spectroradiometric datasets during the period 1990-2011. The analysis includes the long-term variability of total ozone, aerosol optical...

This study examines the UV variability at 305 nm and 325 nm over selected sites in Canada, Europe and Japan. Site selection was based by the availability of UV spectroradiometric datasets longer than 15 yr. The analysis of UV variability was conducted in combination to total ozone, aerosol optical depth and cloud variability. The results suggest th...

A heat transfer model is constructed to derive the surface temperature of specimens in outdoor weathering. Data on thermal properties of materials and routinely collected weather data are used as inputs for the model. The model is validated against surface temperature data measured on samples of 11 different materials exposed to natural outdoor wea...

A facility for exploring wavelength dependencies in ultraviolet (UV) radiation induced degradation in materials has been designed and constructed. The device is essentially a spectrograph separating light from a lamp to spectrally resolved UV radiation. It is based on a 1 kW xenon lamp and a flat-field concave holographic grating 10 cm in diameter....

Modern polymeric materials possess an ever increasing potential in a large variety of outdoor objects and structures offering an alternative for many traditional materials. In outdoor applications, however, polymers are subject to a phenomenon called weathering. This is primarily observed as unwanted property changes: yellowing or fading, chalking,...

UV radiation exerts several effects concerning life on Earth, and spectral information on the prevailing UV radiation conditions is needed in order to study each of these effects. In this paper, we present a method for reconstruction of solar spectral UV irradiances at the Earth's surface. The method, which is a further development of an earlier pu...

UV radiation conditions in a UV chamber equipped with four 300-W mercury vapour lamps have been characterized to assess the exposure received by the specimens aged in the chamber. Spectrally resolved measurements were performed on UV radiation emitted by new lamps and lamps operated for 4850 h in the chamber. An intensity decrease of as much as 75%...

The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67°22'...

The quality assurance of the two Brewer spectrophotometers of the Finnish Meteorological Institute is discussed in this paper. The complete data processing chain from raw signal to high quality spectra is presented. The quality assurance includes daily maintenance, laboratory characterizations, calculation of long-term spectral responsivity, data p...

The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67.37° N, 2...

The quality assurance of the two Brewer spectrophotometers of the Finnish Meteorological Institute is discussed in this paper. The complete data processing chain from raw signal to high quality spectra is presented. The quality assurance includes daily maintenance, laboratory characterizations, calculation of long term spectral responsivity, data p...