Air pollution is a global cause of concern due to the severe environmental impacts such as acid rain, smog, damage to crops and infrastructure; and wide-ranging health impacts like eye irritation, nasal irritation or chronic respiratory illness, depending on factors like type of pollutant, its concentration and exposure duration. It is leading contributor to the global burden of diseases and deaths. According to the World Health Organization (WHO), globally 4.2 million people die due to ambient (outdoor) air pollution while 3.8 million die of indoor air pollution (from cookstoves and domestic fuels). Results from our air quality monitoring stations put Rwanda among the country having air pollution levels that exceed WHO air quality especially on PM2.5 and PM10. This high level of air pollution concentration contributed to more than 5500 deaths in 2017 in Rwanda. Thus, assessing the air quality is of extreme importance to develop policy interventions and pollution control measures to safeguard the environmental and human wellbeing in a particular area. To address this, in 2019 Rwanda started it first ever air quality monitoring system with 22 Real-time, Affordable, Multi-Pollutant (RAMP) air quality monitors and one reference station to provide a complete picture of air quality in the Rwanda. Stations are installed country-wide focusing on the City of Kigali and Secondary cities in the country and measure criteria pollutants like Particulate matter, Sulphur Dioxide, Oxides of nitrogen, Carbon monoxide, and secondary pollutants like Ozone. The monitoring of pollutants is carried out for 24 hours every day and is continuous along the year to have annual trend of air pollution in Rwanda. The data obtained are also used to calculate the Air Quality Index (AQI), a comprehensive and easy to interpret value, representing the air quality status and disseminated through a web-based portal(https://aq.rema.gov.rw/). To improve air quality management in Rwanda, the government of Rwanda and the government of Finland has started a partnership through FINKERAT Project. In its different capacity building programs FINKERAT has helped in integrating satellite data into Rwanda's air quality monitoring framework to address limitations in spatial coverage. This integration not only expands the geographical reach of monitoring but also enhances the granularity of information available. Satellite data, with its broad coverage and high temporal resolution, will complements ground-based measurements by providing a holistic view of air quality dynamics, especially in remote or challenging to reach areas. Through this FINKERAT project Rwanda’s air quality monitoring is building the capacity in air quality modelling that will lead to air quality forecasting. Forecasting air pollution will help in providing early warnings to communities and authorities to minimize health risks, it will also optimize resource allocation, supports evidence-based policies, and helps businesses adapt operations, fostering resilience and sustainability in the face of pollution challenges.

Spectral ultraviolet (UV) radiation measurements have been performed with a Brewer spectroradiometer at Sodankylä (67°N) since 1990. The site is located in the Arctic and affected by stratospheric ozone depletion during spring. The UV time series includes years of strong ozone depletion, which led to increased UV levels since the beginning of the 1990s. In this work, we have analyzed the time series of the time period 1990–2021. Spectral changes are analyzed in steps of 1 nm for wavelengths between 300 and 325 nm. We performed sensitivity tests by varying the start and end year of the analysis and found that results are strongly dependent on the chosen time period. Due to the high year-to-year variability in monthly means, no significant trend was found. Typical maximum values, UV index 5, occur during summer time, because the Sun is still low in the sky during the Arctic ozone depletion period, leading to UV index values lower than in the summer. However, at Marambio (64°S), Antarctica, measurements with a GUV multichannel radiometer show that UV levels can exceed those of summer time also during the ozone depletion period. The Finnish Meteorological Institute (FMI) has started Marambio’s UV measurements in 2017 in collaboration with Servicio Meteorológico Nacional, Argentina. Here we show results for the first four years of measurements 2017-2021. The maximum UV index measured during that time period, UV index 13, was measured in November-December in 2020 as a consequence of the strong and long-lasting polar vortex of that year.

Solar ultraviolet (UV) radiation has a broad range of effects concerning life on Earth. Because of its high photon energy, UV radiation influences human health, terrestrial and aquatic ecosystems, air quality, and materials in various ways. The Sentinel 5 Precursor (S5P) mission on a sun-synchronous orbit with an ascending node equatorial crossing at 13:30, which in conjunction with a wide swath of 2600 km provides near-global daily coverage. S5P’s TROPOMI instrument measures radiation backscattered from the Earth–atmosphere system and provides observations of atmospheric composition with the best spatial resolution presently. Among other things, TROPOMI measurements are used for calculating the UV radiation reaching the Earth's surface over the sunlit part of the globe. This UV-radiation product is processed at the Finnish Meteorological Institute Copernicus Collaborative Ground segment. The product was released via FinHUB in summer 2020. The TROPOMI L2 UV product contains 36 UV parameters in total, including irradiances at four different wavelengths and dose rates for erythemal and vitamin D synthesis action spectra. All parameters are calculated for overpass time, for solar noon time, and for theoretical clear-sky conditions with no clouds or aerosols. Daily doses and accumulated irradiances are also calculated by integrating over the sunlit part of the day. In addition to UV parameters, quality flags related to the UV product and processing are generated.Validation with ground based instruments have shown that the agreement is very good, typically within 10%. The S5P is the first Copernicus mission dedicated to atmospheric observations, and it will be complemented by Sentinel 4 with geostationary orbit and Sentinel 5 on Sun-synchronous morning orbit with planned launches in the coming years. It is expected that surface UV-radiation products from these instruments will continue the present time series. The TROPOMI surface UV radiation product responds to the increasing need for information regarding the tropospheric chemistry and biologically active wavelengths of the solar spectrum reaching the surface. In this presentation we introduce the TROPOMI UV radiation product and future developments, discuss about the quality of the product and demonstrate the usefulness of the satellite UV-data by showing resent applications including among others the exceptionally high UV-radiation conditions in mid latitudes due to persistent Antarctic ozone hole in December 2020 and modeling of seasonal cycle of COVID-19. By combining the TROPOMI UV data with observations of trace gases from the same instrument, there is also a potential for new kind of applications, where satellite data can be used in novel ways to study photochemical processes in the troposphere.

We describe NASA’s Applied Sciences Disasters Program, which is a collaborative project between the Direct Readout Laboratory (DRL), ozone processing team, Jet Propulsion Laboratory, Geographic Information Network of Alaska (GINA), and Finnish Meteorological Institute (FMI), to expedite the processing and delivery of direct readout (DR) volcanic ash and sulfur dioxide (SO2) satellite data. We developed low-latency quantitative retrievals of SO2 column density from the solar backscattered ultraviolet (UV) measurements using the Ozone Mapping and Profiler Suite (OMPS) spectrometers as well as the thermal infrared (TIR) SO2 and ash indices using Visible Infrared Imaging Radiometer Suite (VIIRS) instruments, all flying aboard US polar-orbiting meteorological satellites. The VIIRS TIR indices were developed to address the critical need for nighttime coverage over northern polar regions. Our UV and TIR SO2 and ash software packages were designed for the DRL’s International Planetary Observation Processing Package (IPOPP); IPOPP runs operationally at GINA and FMI stations in Fairbanks, Alaska, and Sodankylä, Finland. The data are produced within 30 min of satellite overpasses and are distributed to the Alaska Volcano Observatory and Anchorage Volcanic Ash Advisory Center. FMI receives DR data from GINA and posts composite Arctic maps for ozone, volcanic SO2, and UV aerosol index (UVAI, proxy for ash or smoke) on its public website and provides DR data to EUMETCast users. The IPOPP-based software packages are available through DRL to a broad DR user community worldwide.

Abstract. 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 x 3.5 km2 (5.6 x 3.5 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 non-homogeneous 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.

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.

In this work we present evidence that quasi-cyclical perturbations in total ozone (quasi-biennial oscillation – QBO, El Niño–Southern Oscillation – ENSO, and North Atlantic Oscillation – NAO) can be used as independent proxies in evaluating Global Ozone Monitoring Experiment (GOME) 2 aboard MetOp A (GOME-2A) satellite total ozone data, using ground-based (GB) measurements, other satellite data, and chemical transport model calculations. The analysis is performed in the frame of the validation strategy on longer time scales within the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility on Atmospheric Composition Monitoring (AC SAF) project, covering the period 2007–2016. Comparison of GOME-2A total ozone with ground observations shows mean differences of about -0.7±1.4 % in the tropics (0–30∘), about +0.1±2.1 % in the mid-latitudes (30–60∘), and about +2.5±3.2 % and 0.0±4.3 % over the northern and southern high latitudes (60–80∘), respectively. In general, we find that GOME-2A total ozone data depict the QBO–ENSO–NAO natural fluctuations in concurrence with the co-located solar backscatter ultraviolet radiometer (SBUV), GOME-type Total Ozone Essential Climate Variable (GTO-ECV; composed of total ozone observations from GOME, SCIAMACHY – SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY, GOME-2A, and OMI – ozone monitoring instrument, combined into one homogeneous time series), and ground-based observations. Total ozone from GOME-2A is well correlated with the QBO (highest correlation in the tropics of +0.8) in agreement with SBUV, GTO-ECV, and GB data which also give the highest correlation in the tropics. The differences between deseazonalized GOME-2A and GB total ozone in the tropics are within ±1 %. These differences were tested further as to their correlations with the QBO. The differences had practically no QBO signal, providing an independent test of the stability of the long-term variability of the satellite data. Correlations between GOME-2A total ozone and the Southern Oscillation Index (SOI) were studied over the tropical Pacific Ocean after removing seasonal, QBO, and solar-cycle-related variability. Correlations between ozone and the SOI are on the order of +0.5, consistent with SBUV and GB observations. Differences between GOME-2A and GB measurements at the station of Samoa (American Samoa; 14.25∘ S, 170.6∘ W) are within ±1.9 %. We also studied the impact of the NAO on total ozone in the northern mid-latitudes in winter. We find very good agreement between GOME-2A and GB observations over Canada and Europe as to their NAO-related variability, with mean differences reaching the ±1 % levels. The agreement and small differences which were found between the independently produced total ozone datasets as to the influence of the QBO, ENSO, and NAO show the importance of these climatological proxies as additional tool for monitoring the long-term stability of satellite–ground-truth biases.

This overview paper highlights the successes of the Ozone Monitoring Instrument (OMI) on board the Aura satellite spanning a period of nearly 14 years. Data from OMI has been used in a wide range of applications and research resulting in many new findings. Due to its unprecedented spatial resolution, in combination with daily global coverage, OMI plays a unique role in measuring trace gases important for the ozone layer, air quality, and climate change. With the operational very fast delivery (VFD; direct readout) and near real-time (NRT) availability of the data, OMI also plays an important role in the development of operational services in the atmospheric chemistry domain.

The three Global Ozone Monitoring Experiment-2 instruments will provide unique and long data sets for atmospheric research and applications. The complete time period will be 2007–2022, including the period of ozone depletion as well as the beginning of ozone layer recovery. Besides ozone chemistry, the GOME-2 (Global Ozone Monitoring Experiment-2) products are important e.g. for air quality studies, climate modelling, policy monitoring and hazard warnings. The heritage for GOME-2 is in the ERS/GOME and Envisat/SCIAMACHY instruments. The current Level 2 (L2) data cover a wide range of products such as ozone and minor trace gas columns (NO2, BrO, HCHO, H2O, SO2), vertical ozone profiles in high and low spatial resolution, absorbing aerosol indices, surface Lambertian-equivalent reflectivity database, clear-sky and cloud-corrected UV indices and surface UV fields with different weightings and photolysis rates. The Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) processes and disseminates data 24/7. Data quality is guaranteed by the detailed review processes for the algorithms, validation of the products as well as by a continuous quality monitoring of the products and processing. This paper provides an overview of the O3M SAF project background, current status and future plans for the utilisation of the GOME-2 data. An important focus is the provision of summaries of the GOME-2 products including product principles and validation examples together with sample images. Furthermore, this paper collects references to the detailed product algorithm and validation papers.

This paper shows the results of the comparison of satellite SO2 observations from OMI (Ozone Monitoring Instrument) and OMPS (Ozone Mapping Profiler Suite) with ground-based measurements during the Icelandic Holuhraun fissure eruption in September 2014. The volcanic plume reached Finland on several days during the month of September. The SO2 total columns from the Brewer direct sun (DS) measurements in Sodankylä (67.42° N, 26.59° E), northern Finland, are compared to the satellite data. The operational satellite SO2 products are evaluated for high latitude conditions (e.g. large solar zenith angle, SZA). The results show that the best agreement can be found for lowest SZAs, close-to-nadir satellite pixels, cloud fraction below 0.3 and small distance between the station and the centre of the pixel. Under good retrieval conditions, the difference between satellite data and Brewer measurements remains mostly below the uncertainty on the satellite SO2 retrievals (up to about 2 DU at high latitudes). The satellite products assuming a priori profile with SO2 predominantly in the planetary boundary layer give total column values with the best agreement with the ground-based data. The analysis of the SO2 surface concentrations at four air quality stations in northern Finland shows that the volcanic plume coming from Iceland was located very close to the surface. This is connected to the fact that this was a fissure eruption and most of the SO2 was emitted into the troposphere. This is an exceptional case because the SO2 volcanic emissions directly affect the air quality levels at surface in an otherwise pristine environment like northern Finland. The time evolution of the SO2 concentrations peaks during the same days when large SO2 total column values are measured by the Brewer in Sodankylä and enhanced SO2 signal is visible over northern Finland from the satellite maps. Thus, the satellite retrievals were able to detect the spatiotemporal evolution of the volcanic plume as compared to the surface observations. Furthermore, direct-broadcast SO2 satellite data (from both OMI and OMPS instruments) are compared for the first time against ground-based observations.

Abstract. This paper shows the validation results of the satellite SO2 observations from OMI (Ozone Monitoring Instrument) and OMPS (Ozone Mapping Profiler Suite) during the Icelandic Holuhraun fissure eruption in September 2014. The volcanic plume reached Finland on several days during the month of September. The SO2 total columns from the Brewer direct sun (DS) measurements in Sodankylä (67.42° N, 26.59° E), northern Finland, are compared to the satellite data. Challenging retrieval conditions at high latitudes (like large solar zenith angle, SZA) are considered in the comparison. The results show that the best agreement can be found for small SZAs, close-to-nadir satellite pixels, cloud fraction below 0.3 and small distance between the station and the centre of the pixel. Under good retrieval conditions, the difference between satellite data and Brewer measurements remains mostly below the uncertainty on the satellite SO2 retrievals (up to about 2 DU at high latitudes). The satellite products assuming a priori profile with SO2 predominantly in the planetary boundary layer give total column values close to the ground-based data, suggesting that the volcanic SO2 plume was located at particularly low altitudes. This is connected to the fact that this was a fissure eruption and most of the SO2 was emitted into the troposphere. The analysis of the SO2 surface concentrations at four air quality stations in northern Finland supports the hypothesis that the volcanic plume coming from Iceland was located very close to the surface. The time evolution of the SO2 concentrations peaks during the same days when large SO2 total column values are measured by the Brewer in Sodankylä and enhanced SO2 signal is visible over northern Finland from the satellite maps. This is an exceptional case because the SO2 volcanic emission directly affect the air quality levels at surface in an otherwise pristine environment like northern Finland. OMI and OMPS SO2 retrievals from direct-broadcast measurements are validated for the first time in this paper.

) and volcanic ash into the atmosphere, posing a substantial risk to aviation safety. Ingesting near-real time and Direct Readout satellite volcanic cloud data is vital for improving reliability of volcanic ash forecasts and mitigating the effects of volcanic eruptions on aviation and the economy. NASA volcanic products from the Ozone Monitoring Insrument (OMI) aboard the Aura satellite have been incorporated into Decision Support Systems of many operational agencies. With the Aura mission approaching its 10th anniversary, there is an urgent need to replace OMI data with those from the next generation operational NASA/NOAA Suomi National Polar Partnership (SNPP) satellite. The data provided from these instruments are being incorporated into forecasting models to provide quantitative ash forecasts for air traffic management. This study demonstrates the feasibility of the volcanic near-real time and Direct Readout data products from the new Ozone Monitoring and Profiling Suite (OMPS) ultraviolet sensor onboard SNPP for monitoring and forecasting volcanic clouds. The transition of NASA data production to our operational partners is outlined. Satellite observations are used to constrain volcanic cloud simulations and improve estimates of eruption parameters, resulting in more accurate forecasts. This is demonstrated for the 2012 eruption of Copahue. Volcanic eruptions are modeled using the Goddard Earth Observing System, Version 5 (GEOS-5) and the Goddard Chemistry Aerosol and Radiation Transport (GOCART) model. A hindcast of the disruptive eruption from Iceland’s Eyjafjallajokull is used to estimate aviation re-routing costs using Metron Aviation’s ATM Tools.

In this paper we present the Modified Onion Peeling (MOP) inversion method, which is for the first time used to retrieve vertical profiles of stratospheric trace gases from Odin/OSIRIS limb scatter measurements. Since the original publication of the method in 2002, the method has undergone major modifications discussed here. The MOP method now uses a spectral microwindow for the NO2 retrieval, instead of the wide UV‐visible band used for the ozone, air, and aerosol retrievals. We give a brief description of the algorithm itself and show its performance with both simulated and real data. Retrieved ozone and NO2 profiles from the OSIRIS measurements were compared with data from the GOMOS and HALOE instruments. No more than 5% difference was found between OSIRIS daytime and GOMOS nighttime ozone profiles between 21 and 45 km. The difference between OSIRIS and HALOE sunset NO2 mixing ratio profiles was at most 25% between 20 and 40 km. The neutral air density was compared with the ECMWF analyzed data and around 5% difference was found at altitudes from 20 to 55 km. However, OSIRIS observations yield as much as 80% greater aerosols number density than GOMOS observations between 15 and 35 km. These validation results indicate that the quality of MOP ozone, NO2, and neutral air is good. The new version of the method introduced here is also easily expanded to retrieve additional species of interest.

The Dragon-Star project work has concentrated on the studies of the middle atmosphere in global and local scale using satellite and ground based measurements as well modelling. In this article we present results from analy- sis of measurements of ozone profiles from GOMOS on ENVISAT and total ozone measurements from OMI on EOS-Aura. The ozone layer above China has been shown to display both characteristics of the tropical ozone layer and the more dynamic polar ozone layer. The annual variation in the northern part of China is large whereas the southern part situation is relatively stable. On daily scale ozone can show large variations because of plane- tary wave disturbances and more local weather patterns. A peculiar low ozone values are evident above the Ti- betan plateau.