Papers by Anders Lindfors
Atmospheric Measurement Techniques, 2020
The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite... more 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 km 2 (5.6 × 3.5 km 2 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 groundbased 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.
Solar Energy, 2020
Abstract As the share of photovoltaics (PV) in electricity production increases, accurate modelin... more Abstract As the share of photovoltaics (PV) in electricity production increases, accurate modeling and forecasting of its output becomes critical. PV output is however affected by multiple factors, making accurate modeling of these systems a non-trivial task. This study provides new insight on the performance of a popular parametric PV output model in a Nordic context. The model and its subcomponents – including estimations on plane-of-array radiation, PV module temperature, and PV output – are here evaluated against dedicated measurements at two Finnish sites. In addition, a novel Quality Control (QC) approach is introduced for handling calculated direct normal irradiance (DNI) values. All reviewed methods show good agreement with the references. The proposed QC efficiently filters unrealistic calculated DNI data, providing a potential approach for DNI QC implementation. In snow-free conditions, the selected PV module temperature scheme has a mean absolute error (MAE) around 2 °C, while the bias is below 1 °C. The plane-of-array radiation model has a MAE of 10–15 W/m2 with a bias of smaller than ±10 W/m2, depending on the site location and available input data. Altogether, the PV model is shown to provide relevant PV system performance information while demonstrating precise performance in snow-free conditions. By implementing site-specific parameter optimization, MAE was reduced from 19 to 14 W/kWp and bias lowered from 15 to 7 W/kWp. For the locations studied, the estimated PV output losses due to snow cover for the winter period 2017–2018 are estimated to be up to 1.5 months of summer production.
Journal of Documentation, 2019
Purpose The purpose of this paper is to examine knowledge-creating interaction in developing an i... more Purpose The purpose of this paper is to examine knowledge-creating interaction in developing an innovation in a multidisciplinary research community with hermeneutic phenomenology, to understand how previous experiences and future prospects shape the process and to examine the circumstances, which support or limit knowledge creation. Design/methodology/approach The approach of this study is phenomenological and the empirical case study has been conducted using ethnography. The data consist of field notes, videos, interviews and documents of a BCDC energy consortium, developing energy weather forecast (EWF) in a new type of research environment. Findings The results indicate that the role of actual interactive events was crucial in the development of EWF. Hermeneutic approach illustrated that the roots of that event were in the past experiences of the participants and the circumstances, which promoted the development of the innovation, but the acknowledgment of the future prospects w...
SSRN Electronic Journal, 2018
Previous empirical literature on residential dynamic pricing for the Nordic market has questioned... more Previous empirical literature on residential dynamic pricing for the Nordic market has questioned whether households will in fact appropriately respond, in view of the low price variability and price responsiveness in the Swedish setting. Household demand response is an issue of some importance in view of increasingly smart grids in which high shares of renewable supply are being promoted partly in view of these possibilities. In addition, an important development in the Nordic market relates to increasing thrust on household PV panels. In view of the interaction between RTP-driven and PV generation-driven load changes, an analysis of the combined effects in relation to system timing is important to understand, not least because this can affect the nature of benefits to households and the electric grid. Using a unique and very detailed dataset on household electricity consumption, in combination with simulated solar panel micro-generation data, these aspects are explored in an empirical framework similar to that used in the prior literature. Our findings indicate that even with minimal price responsiveness, household response to dynamic pricing can lead to load changes with sizeable benefits. In addition, the introduction of PV panels, contrary to what may be assumed at a first glance, appear to be beneficial to the electric grid, largely due to the time pattern of winter PV generation. Overall, our empirical findings provide tentative evidence to indicate that RTP, by incentivizing households to provide demand response at appropriate times, can aid in integration of renewables.
Advances in Science and Research, 2018
Downwelling shortwave radiation at the surface (SWDS, global solar radiation flux), given by thre... more Downwelling shortwave radiation at the surface (SWDS, global solar radiation flux), given by three different parametrization schemes, was compared to observations in the HARMONIE-AROME numerical weather prediction (NWP) model experiments over Finland in spring 2017. Simulated fluxes agreed well with each other and with the observations in the clear-sky cases. In the cloudy-sky conditions, all schemes tended to underestimate SWDS at the daily level, as compared to the measurements. Large local and temporal differences between the model results and observations were seen, related to the variations and uncertainty of the predicted cloud properties. The results suggest a possibility to benefit from the use of different radiative transfer parametrizations in a NWP model to obtain perturbations for the fine-resolution ensemble prediction systems. In addition, we recommend usage of the global radiation observations for the standard validation of the NWP models.
Journal of Applied Meteorology and Climatology, 2018
To support the planning of future solar energy production in India, forthcoming changes in incomi... more To support the planning of future solar energy production in India, forthcoming changes in incoming surface solar radiation and the main physical factors contributing to the change were inferred from simulations performed with 27 global CMIP5 climate models. According to the multimodel-mean response, radiation diminishes by 0.5%–4% by the period 2030–59 (relative to 1971–2000), in tandem with strengthening aerosol and water vapor dimming. The largest reduction is anticipated for northern India. The evolution of incident radiation in the mid- and late twenty-first century depends substantially on the emission scenario. According to the representative concentration pathways RCP2.6 and RCP4.5, solar radiation would gradually recover close to the level that prevailed in the late twentieth century. This results from the peaking of aerosol loading before midcentury while the water vapor content continuously increases somewhat. Conversely, under RCP8.5, incident radiation would still decli...
AIP Conference Proceedings, 2017
At Sodankylä (67 • N), spectra of solar ultraviolet radiation (UVR) have been measured with a Bre... more 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 characterizations and theoretical approaches. Methods for cosine correction, temperature correction and determination of long-term changes in spectral responsivity were applied. Bad measurements were identified by using various quality assurance tools including comparisons with reconstructed UV dose rates, synchronous broadband UV dose rates, global radiation and clear sky model calculations. We calculated daily maximum UV indices from the spectral time series. The daily maxima reached on average a value of 5 in midsummer, whereas the maximum UV index value of 6 was measured only twice: in 2011 and in 2013. We calculated the relative spectral changes in measured UV irradiances. An anti-correlation with total ozone was found in April and June, but no statistically significant longterm changes were found. The effect of snow, enhancing the measured UVR due to high albedo, was important during late spring. Short-term variations were mostly due to changes in cloudiness, which was the dominant factor during summertime.
Atmospheric Measurement Techniques Discussions, 2015
Satellite based surface UV product of the Ozone Monitoring Instrument OMI was validated using gro... more Satellite based surface UV product of the Ozone Monitoring Instrument OMI was validated using ground based UV measurements from the two Finnish sites Jokioinen and Sodankylä. The goal was to further investigate the observed positive UV bias of the OMI UV product focusing on how it may be connected to cloudiness during the overpass of the Aura satellite. A total of seven years of summer time data was used to compare OMI UV index to a reference UVI observed on the ground with Solar Light 501 broadband radiometers. Cloudiness during satellite overpass was determined with auxiliary ground based observations on sunshine duration, cloud cover and global radiation as well as the satellite based MODIS cloud cover estimates. The analysis aimed to minimize the error sources from temporal discrepancies and from the differences in the field of view of OMI and its ground based reference data. As a result, OMI UV product was seen to overestimate surface UV index by 21% in average and overcast UV ...
Atmospheric Chemistry and Physics Discussions, 2015
The importance of light absorbing organic aerosols, often called brown carbon (BrC), has become e... more The importance of light absorbing organic aerosols, often called brown carbon (BrC), has become evident in recent years. However, there are relatively few measurement-based estimates for the direct radiative effect of BrC so far. In those earlier studies, the AErosol RObotic NETwork (AERONET) measured Aerosol Absorption Optical Depth (AAOD) and Absorption Angstrom Exponent (AAE) have been exploited. However, these two pieces of information are clearly not sufficient to separate properly carbonaceous aerosols from dust, while imaginary indices of refraction would contain more and better justified information for this purpose. This is first time that the direct radiative effect (DRE) of BrC is estimated by exploiting the AERONET-retrieved imaginary indices. We estimated it for four sites in Indo-Gangetic Plain (IGP), Karachi, Lahore, Kanpur and Gandhi College. We found a distinct seasonality, which was generally similar among all the sites, but with slightly different strengths. The m...
Remote Sensing of Clouds and the Atmosphere Xi, 2006
Backer (2) , A. Bais (3) , A. Curylo (4) , K. Eerme (5) , U. Feister (6) , B. Johnsen (7) , J. Ju... more Backer (2) , A. Bais (3) , A. Curylo (4) , K. Eerme (5) , U. Feister (6) , B. Johnsen (7) , J. Junk (8) , A. Kazantzidis (3) , J. Krzyscin (9) , A. Lindfors (10) , J. A. Olseth (11) , P. den Outer (12) , A. Pribullova (13) , A. W. Schmalwieser (14) , H. Slaper (12) , H. Staiger (15) , J. Verdebout (16) , L. Vuilleumier (17) , P. Weihs (18)
Journal of Climate, 2012
Clear-sky brightness temperature measurements from the High-Resolution Infrared Radiation Sounder... more Clear-sky brightness temperature measurements from the High-Resolution Infrared Radiation Sounder (HIRS) are simulated with two climate models via a radiative transfer code. The models are sampled along the HIRS orbit paths to derive diurnal climatologies of simulated brightness temperature analogous to an existing climatology based on HIRS observations. Simulated and observed climatologies are compared to assess model performance and the robustness of the observed climatology. Over land, there is good agreement between simulations and observations, with particularly high consistency for the tropospheric temperature channels. Diurnal cycles in the middle- and upper-tropospheric water vapor channels are weak in both simulations and observations, but the simulated diurnal brightness temperature ranges are smaller than are observed with different phase and there are also intermodel differences. Over sea, the absence of diurnal variability in the models’ sea surface temperatures causes ...
Journal of Atmospheric and Oceanic Technology, 2011
A climatology of the diurnal cycles of HIRS clear-sky brightness temperatures was developed based... more A climatology of the diurnal cycles of HIRS clear-sky brightness temperatures was developed based on measurements over the period 2002–07. This was done by fitting a Fourier series to monthly gridded brightness temperatures of HIRS channels 1–12. The results show a strong land–sea contrast with stronger diurnal cycles over land, and extending from the surface up to HIRS channel 6 or 5, with regional maxima over the subtropics. Over seas, the diurnal cycles are generally small and therefore challenging to detect. A Monte Carlo uncertainty analysis showed that more robust results are reached by aggregating the data zonally before applying the fit. The zonal fits indicate that small diurnal cycles do exist over sea. The results imply that for a long-lived satellite such as NOAA-14, drift in the overpass time can cause a diurnal sampling bias of more than 5 K for channel 8 (surface and lower troposphere).
Atmospheric Chemistry and Physics, 2008
The quality assurance of the two Brewer spectrophotometers of the Finnish Meteorological Institut... more 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 processing and quality assessment. The cosine correction of the measurements is based on a new method, and included in the data processing software. The results showed that the actual cosine correction factor of the Finnish Brewers can vary between 1.08-1.13 and 1.08-1.12, respectively, depending on the sky radiance distribution and wavelength. The temperature characterization showed a linear temperature dependence between the internal temperature and the photon counts per cycle, and a temperature correction was used for correcting the measurements. The long term spectral responsivity was calculated using time series of several lamps using two slightly different methods. The long term spectral responsivity was scaled to the irradiance scale of the Helsinki University of Technology (HUT) for the whole measurement time periods 1990-2006 and 1995-2006 for Sodankyl ä and Jokioinen, respectively. Both Brewers have participated in many international spectroradiometer comparisons, and have shown good stability. The differences between the Brewers and the portable reference spectroradiometer QASUME have been within 5% during 2002-2007.
Atmospheric Chemistry and Physics, 2013
Pyranometer measurements of the solar surface radiation (SSR) are available at many locations wor... more Pyranometer measurements of the solar surface radiation (SSR) are available at many locations worldwide, often as long time series covering several decades into the past. These data constitute a potential source of information on the atmospheric aerosol load. Here, we present a method for estimating the aerosol optical depth (AOD) using pyranometer measurements of the SSR together with total water vapor column information. The method, which is based on radiative transfer simulations, was developed and tested using recent data from Thessaloniki, Greece. The effective AOD calculated using this method was found to agree well with co-located AERONET measurements, exhibiting a correlation coefficient of 0.9 with 2/3 of the data found within ±20 % or ±0.05 of the AERONET AOD. This is similar to the performance of current satellite aerosol methods. Differences in the AOD as compared to AERONET can be explained by variations in the aerosol properties of the atmosphere that are not accounted for in the idealized settings used in the radiative transfer simulations, such as variations in the single scattering albedo and Ångstr öm exponent. Furthermore, the method is sensitive to calibration offsets between the radiative transfer simulations and the pyranometer SSR. The method provides an opportunity of extending our knowledge of the atmospheric aerosol load to locations and times not covered by dedicated aerosol measurements.
Atmospheric Chemistry and Physics Discussions, 2015
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Plant, Cell & Environment, 2014
Wavelengths in the ultraviolet (UV) region of the solar spectrum, UV-B (280-315 nm) and UV-A (315... more Wavelengths in the ultraviolet (UV) region of the solar spectrum, UV-B (280-315 nm) and UV-A (315-400 nm), are key environmental signals modifying several aspects of plant physiology. Despite significant advances in the understanding of plant responses to UV-B and the identification of signalling components involved, there is limited information on the molecular mechanisms that control UV-B signalling in plants under natural sunlight. Here, we aimed to corroborate the previous suggested role for RADICAL-INDUCED CELL DEATH1 (RCD1) in UV-B signalling under full spectrum sunlight. Wild-type Arabidopsis thaliana and the rcd1-1 mutant were used in an experimental design outdoors where UV-B and UV-A irradiances were manipulated using plastic films, and gene expression, PYRIDOXINE BIOSYNTHESIS1 (PDX1) accumulation and metabolite profiles were analysed in the leaves. At the level of transcription, RCD1 was not directly involved in the solar UV-B regulation of genes with functions in UV acclimation, hormone signalling and stress-related markers. Furthermore, RCD1 had no role on PDX1 accumulation but modulated the UV-B induction of flavonoid accumulation in leaves of Arabidopsis exposed to solar UV. We conclude that RCD1 does not play an active role in UV-B signalling but rather modulates UV-B responses under full spectrum sunlight.
PLANT PHYSIOLOGY, 2013
Photomorphogenic responses triggered by low fluence rates of ultraviolet B radiation (UV-B; 280-3... more Photomorphogenic responses triggered by low fluence rates of ultraviolet B radiation (UV-B; 280-315 nm) are mediated by the UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8). Beyond our understanding of the molecular mechanisms of UV-B perception by UVR8, there is still limited information on how the UVR8 pathway functions under natural sunlight. Here, wild-type Arabidopsis (Arabidopsis thaliana) and the uvr8-2 mutant were used in an experiment outdoors where UV-A (315-400 nm) and UV-B irradiances were attenuated using plastic films. Gene expression, PYRIDOXINE BIOSYNTHESIS1 (PDX1) accumulation, and leaf metabolite signatures were analyzed. The results show that UVR8 is required for transcript accumulation of genes involved in UV protection, oxidative stress, hormone signal transduction, and defense against herbivores under solar UV. Under natural UV-A irradiance, UVR8 is likely to interact with UV-A/blue light signaling pathways to moderate UV-B-driven transcript and PDX1 accumulation. UVR8 both positively and negatively affects UV-A-regulated gene expression and metabolite accumulation but is required for the UV-B induction of phenolics. Moreover, UVR8-dependent UV-B acclimation during the early stages of plant development may enhance normal growth under long-term exposure to solar UV.
Environmental Science & Technology, 2013
We report experimentally determined first-order rate constants of MeHg photolysis in three waters... more We report experimentally determined first-order rate constants of MeHg photolysis in three waters along a Boreal lake-wetland gradient covering a range of pH (3.8-6.6), concentrations of total organic carbon (TOC 17.5-81 mg L(-1)), total Fe (0.8-2.1 mg L(-1)), specific UV254 nm absorption (3.3-4.2 L mg(-1) m(-1)) and TOC/TON ratios (24-67 g g(-1)). Rate constants determined as a function of incident sunlight (measured as cumulative photon flux of photosynthetically active radiation, PAR) decreased in the order dystrophic lake &amp;amp;amp;amp;amp;amp;amp;amp;gt; dystrophic lake/wetland &amp;amp;amp;amp;amp;amp;amp;amp;gt; riparian wetland. After correction for light attenuation by dissolved natural organic matter (DOM), wavelength-specific (PAR: 400-700 nm, UVA: 320-400 nm and UVB: 280-320 nm) first-order photodegradation rate constants (kpd) determined at the three sites were indistinguishable, with average values (± SE) of 0.0023 ± 0.0002, 0.10 ± 0.024 and 7.2 ± 1.3 m(2) E(-1) for kpdPAR, kpdUVA, and kpdUVB, respectively. The relative ratio of kpdPAR, kpdUVA, and kpdUVB was 1:43:3100. Experiments conducted at varying MeHg/TOC ratios confirm previous suggestions that complex formation with organic thiol groups enhances the rate of MeHg photodegradation, as compared to when O and N functional groups are involved in the speciation of MeHg. We suggest that if the photon fluxes of PAR, UVA, and UVB radiation are separately determined and the wavelength-specific light attenuation is corrected for, the first-order rate constants kpdPAR, kpdUVA, and kpdUVB will be universal to waters in which DOM (possibly in concert with Fe) controls the formation of ROS, and the chemical speciation of MeHg is controlled by the complexation with DOM associated thiols.
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Papers by Anders Lindfors