Ultraviolettkiirguse sõltuvus kliimateguritest. Eesti varasemate UV-kiirguse dooside arvutamine

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Looduslik ultraviolettkiirgus (UV-kiirgus) on päikesekiirguse osa, millest maapinnani jõuab UVB (280–315 nm) ning UVA (315–400 nm) kiirgus. Suure energia tõttu avaldab UV-kiirgus mõju elusorganismidele, materjalidele ning atmosfääri keemiale. Enim pakub ühiskonnale huvi UV-kiirguse mõju inimestele – ohustatud on nii nahk, silmad kui immuunsüsteem, samal ajal osaleb UV-kiirgus D vitamiini sünteesis. UV-kiirguse võimaliku toime hindamiseks on vajalik teada maapinnani jõudva kiirguse spektraalset koostist (lühema lainepikkusega kiirgus on üldiselt ohtlikum), saadud energiat ning kuidas neid mõjustavad keskkonnatingimused. Väitekirja peamiseks eesmärgiks on uurida maapinnani jõudva UV-kiirguse ajalist muutlikust Eestis ning millises ulatuses mõjutavad seda pilved, osoon ning aerosoolid. Andmestik põhineb Tartu Observatooriumis alates 2004. aastast registreeritud UV-kiirguse spektritel ning Tõravere ilmajaama vaatlusandmetel. Suvel selge ilma korral võivad Tõraveres UVA päevadoosid ületada 1500 kJ/m2 ning UVB omad 30 kJ/m2. Selliste suurte päevaste dooside korral ulatub UV indeks keskpäeval üle 7, esmaseid päikesekaitsevahendeid peab kasutama juba UV indeksi 3 korral. UVA ja UVB suhe spektris sõltub eelkõige päikese kõrgusest ning osooni hulgast, muutudes suvise päeva jooksul üle 10 korra. Paksud pilved peavad kinni aga vaid kuni 2/3 UV-kiirgusest. Lisaks mõõdetud andmete uurimisele koostati töö käigus ka mudelid UV-kiirguse päevaste dooside arvutamiseks. Mudeleid rakendati UV-kiirguse rekonstrueerimiseks perioodil 1955–2003. Mudelid on jätkuvalt kasutusel ka instrumendi riketest põhjustatud mõõtepauside täitmiseks. Päevadooside katkematu aegrida on loodud ajavahemikule 1955–2015. Minimaalsed UV-doosid olid Tõraveres 1970ndate lõpus ja 1980ndate alguses. Hiljem UV-kiirguse hulk tõusis ja saavutas maksimumi 2011. aasta. Viimasel ajal on aastased doosid olnud taas languses. Väitekirja valmimist toetas oluliselt EU teadusprojekt „Eesti kiirguskliima“.Natural ultraviolet (UV) radiation, reaching the ground, is a part of solar radiation and is divided to UVB (280–315 nm) and UVA (315–400 nm) ranges. Due to high energy UV radiation can influence living organisms, materials as well as atmospheric photochemistry. The public is most interested in the influence of UV radiation on humans, including damage of skin, eyes and immune system. At the same time UV radiation participates in vitamin D synthesis. To evaluate the possible risk of damage or benefit it is important to know the spectral composition (shorter wavelengths are generally more dangerous), received energy and how they are influenced by environmental conditions. The main objective of this work was to investigate the variability of UV radiation reaching the ground in Tõravere, Estonia and how it is influenced by clouds, ozone and aerosols. The dataset is based on measurements conducted at Tartu Observatory since 2004 and on data from Tõravere meteorological station. It was found that in summer in clear conditions the daily dose of UVA can reach over 1500 kJ/m2 and of UVB over 30 kJ/m2. In these high radiation conditions UV index can be over 7. First sun protection is needed in case of UV index 3. The ratio of UVA and UVB can change more than 10 times during a day in summer. Heavy cloudiness decreases irradiance only by 2/3 during the summer. In addition to data analysis models for calculating daily doses were created and reconstruction of UVB and UVA radiation for period 1955–2003 was made. These models are continuously used for filling measurement gaps. Continuous dataset of daily doses from 1955–2015 is now available. Minimum yearly doses in Tõravere were at the end of the 1970s and at the beginning of the 1980s. Since then the yearly doses increased and maximum level was met in 2011. Recently UV doses have decreased. The thesis was supported by EU scientific project "Estonian radiation climate"

Validation of TROPOMI Surface UV Radiation Product

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 resolution for most data products is 7.2x3.5 km2 (5.6x3.5 km2 since 6 August 2019) at nadir. The Finnish Meteorological Institute (FMI) is responsible for the development and processing of the TROPOMI Surface Ultraviolet (UV) Radiation Product which includes 36 UV parameters in total. Ground-based data from 25 sites located in arctic, subarctic, temperate, equatorial and antarctic areas were used for validation of TROPOMI overpass irradiance at 305, 310, 324 and 380 nm, overpass erythemally weighted dose rate / UV index and erythemally weighted daily dose for the period from 1 January 2018 to 31 August 2019. The validation results showed that for most sites 60–80% of TROPOMI data was within ±20% from ground-based data for snow free surface conditions. The median relative differences to ground-based measurements of TROPOMI snow free surface daily doses were within ±10% and ±5% at two thirds and at half of the sites, respectively. At several sites more than 90% of clear sky TROPOMI data were within ±20% from ground-based measurements. Generally median relative differences between TROPOMI data and ground-based measurements were a little biased towards negative values, but at high latitudes where nonhomogeneous topography and albedo/snow conditions occurred, the negative bias was exceptionally high, from -30% to -65%. Positive biases of 10–15% were also found for mountainous sites due to challenging topography. The TROPOMI Surface UV Radiation Product includes quality flags to detect increased uncertainties in the data due to heterogeneous surface albedo and rough terrain which can be used to filter the data retrieved under challenging conditions

Solar UV radiation measurements in Marambio, Antarctica, during years 2017–2019

In March 2017, measurements of downward global irradiance of ultraviolet (UV) radiation were started with a multichannel GUV-2511 radiometer in Marambio, Antarctica (64.23∘ S; 56.62∘ W), by the Finnish Meteorological Institute (FMI) in collaboration with the Servicio Meteorológico Nacional (SMN). These measurements were analysed and the results were compared to previous measurements performed at the same site with the radiometer of the Antarctic NILU-UV network during 2000–2008 and to data from five stations across Antarctica. In 2017/2018 the monthly-average erythemal daily doses from October to January were lower than those averaged over 2000–2008 with differences from 2.3 % to 25.5 %. In 2017/2018 the average daily erythemal dose from September to March was 1.88 kJ m−2, while in 2018/2019 it was 23 % larger (2.37 kJ m−2). Also at several other stations in Antarctica the UV radiation levels in 2017/2018 were below average. The maximum UV indices (UVI) in Marambio were 6.2 and 9.5 in 2017/2018 and 2018/2019, respectively, whereas during years 2000–2008 the maximum was 12. Cloud cover, the strength of the polar vortex and the stratospheric ozone depletion are the primary factors that influence the surface UV radiation levels in Marambio. The lower UV irradiance values in 2017/2018 are explained by the high ozone concentrations in November, February and for a large part of October. The role of cloud cover was clearly seen in December, and to a lesser extent in October and November, when cloud cover qualitatively explains changes which could not be ascribed to changes in total ozone column (TOC). In this study, the roles of aerosols and albedo are of minor influence because the variation of these factors in Marambio was small from one year to the other. The largest variations of UV irradiance occur during spring and early summer when noon solar zenith angle (SZA) is low and the stratospheric ozone concentration is at a minimum (the so-called ozone hole). In 2017/2018, coincident low total ozone column and low cloudiness near solar noon did not occur, and no extreme UV indices were measured

Copernicus Cal/Val Solution: Systematic Ground-Based Measurements

Ülevaate raport olemasolevatest regulaarselt töötavatest kalibreerimise ja valideerimise mõõtejaamadest ja võrgustikest Euroopas ja mujal maailmas. Raportis kirjeldatakse valitud jaamasid ja võrgustikke – üldine informatsioon, andmehaldus, määramatus, arendustegevus, mõõdetavad suurused.This document aims to map different existing ground-based and air-borne instrumented Cal/Val sites and networks acquiring measurements in a systematic manner, in Europe and worldwide. It does not include all available Cal/Val networks but only those that we interviewed or had enough information available online to include in this report. To meet the needs of satellite Cal/Val, measurements one must adhere to the definition for a Fiducial Reference Measurement (FRM)(Giuseppe Zibordi et al. 2014) and to the principles of the Quality Assurance framework for Earth Observation (QA4EO 2010)

Copernicus Cal/Val Solution: Recommendations for R&D activities on instrumentation technologies

Raport Euroopa Liidu kaugseire programmi Copernicus raames kasutusel olevatest kalibreerimise ja valideerimise tehnoloogiatest ja puudujääkidest. Raportis antakse soovitusi uurimis- ja arendustegevusteks tehnoloogia valdkonnas ja esitletakse arenduses olevaid instrumente, mis võiksid seniseid puudujääke tulevikus lahendada.The Document identifies the gaps in instrumentation technologies for pre-flight characterisation, on board calibration and Fiducial Reference Measurements (FRM) used for calibration and validation (Cal/Val) activities for the current Copernicus missions. It also addresses the measurement needs for future Copernicus missions and gives a prioritised list of recommendations for R&D activities on instrumentation technologies

Validation of the TROPOspheric Monitoring Instrument (TROPOMI) surface UV radiation product

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 resolution for most data products is 7.2×3.5 km2 (5.6×3.5 km2 since 6 August 2019) at nadir. The Finnish Meteorological Institute (FMI) is responsible for the development of the TROPOMI UV algorithm and the processing of the TROPOMI surface ultraviolet (UV) radiation product which includes 36 UV parameters in total. Ground-based data from 25 sites located in arctic, subarctic, temperate, equatorial and Antarctic areas were used for validation of the TROPOMI overpass irradiance at 305, 310, 324 and 380 nm, overpass erythemally weighted dose rate/UV index, and erythemally weighted daily dose for the period from 1 January 2018 to 31 August 2019. The validation results showed that for most sites 60 %–80 % of TROPOMI data was within ±20 % of ground-based data for snow-free surface conditions. The median relative differences to ground-based measurements of TROPOMI snow-free surface daily doses were within ±10 % and ±5 % at two-thirds and at half of the sites, respectively. At several sites more than 90 % of cloud-free TROPOMI data was within ±20 % of ground-based measurements. Generally median relative differences between TROPOMI data and ground-based measurements were a little biased towards negative values (i.e. satellite data < ground-based measurement), but at high latitudes where non-homogeneous topography and albedo or snow conditions occurred, the negative bias was exceptionally high: from −30 % to −65 %. Positive biases of 10 %–15 % were also found for mountainous sites due to challenging topography. The TROPOMI surface UV radiation product includes quality flags to detect increased uncertainties in the data due to heterogeneous surface albedo and rough terrain, which can be used to filter the data retrieved under challenging conditions

UV Index monitoring in Europe

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 years. Currently, 160 stations in 25 European countries deliver online values to the public via the Internet. In this paper an overview of these UV Index monitoring sites in Europe is given. The overview includes instruments as well as quality assurance and quality control procedures. Furthermore, some examples are given about how UV Index values are presented to the public. Through these efforts, 57% of the European population is supplied with high quality information, enabling them to adapt behaviour. Although health care, including skin cancer prevention, is costeffective, a proportion of the European population still doesn’t have access to UV Index information