Ground-based Spectroscopic Measurements Research Articles

Complex Validation of Weather Research and Forecasting—Chemistry Modelling of Atmospheric CO2 in the Coastal Cities of the Gulf of Finland

The increase of the CO2 content in the atmosphere caused by anthropogenic emissions from the territories of large cities (~70%) is the critical factor in determining the accuracy of emission estimations. Advanced experiment-based methods of anthropogenic CO2 emission estimation are based on the solution of an inverse problem, using accurate measurements of CO2 content and numerical models of atmospheric transport and chemistry. The accuracy of such models decreases the errors of the emission estimations. The aim of the current study is to adapt numerical weather prediction and atmospheric chemistry model WRF-Chem and validate its capability to simulate atmospheric CO2 for the territories of the two large coastal cities of the Gulf of Finland—St. Petersburg (Russia) and Helsinki (Finland). The research has demonstrated that the WRF-Chem model is able to simulate annual variation, as well as the mean seasonal and diurnal variations of the near-surface CO2 mixing ratio, in Helsinki, at a high spatial resolution (2 km). Correlation between the modelled and measured CO2 mixing ratio is relatively high, at ~0.73, with a mean difference and its standard deviation of 0.15 ± 0.04 and 1.7%, respectively. The differences between the WRF-Chem data and the measurements might be caused by errors in the modelling of atmospheric transport and in a priori CO2 emissions and biogenic fluxes. The WRF-Chem model simulates well the column-averaged CO2 mixing ratio (XCO2) in St. Petersburg (January 2019–March 2020), with a correlation of ~0.95 relative to ground-based spectroscopic measurements by the IR–Fourier spectrometer Bruker EM27/SUN. The error of the XCO2 modelling constitutes ~0.3%, and most likely is related to inaccuracies in chemical boundary conditions and a priori anthropogenic CO2 emissions. The XCO2 time series in St. Petersburg by the WRF-Chem model fits well with global CAMS reanalysis and CarbonTracker-modelled data (the differences are less than ~1%). However, due to much higher spatial resolution (2 vs. over 100 km), the WRF-Chem data are in the best agreement with the ground-based remote measurements of XCO2. According to the study, the modelling errors of XCO2 in St. Petersburg during the whole simulated period are sufficiently minimal to fit the requirement of “Error ≤ 0.2%” in 60% of cases. This requirement should be satisfied to evaluate properly the anthropogenic CO2 emissions of St. Petersburg on a city-scale.

Ground-Based Spectroscopic Measurements of the Total Ammonia Content in the Vicinity of St. Petersburg

Ground-Based Spectroscopic Measurements of the Total Ammonia Content in the Vicinity of St. Petersburg

Polar Stratospheric Clouds Detection at Belgrano II Antarctic Station with Visible Ground-Based Spectroscopic Measurements

By studying the evolution of the color index (CI) during twilight at high latitudes, polar stratospheric clouds (PSCs) can be detected and characterized. In this work, this method has been applied to the measurements obtained by a visible ground-based spectrometer and PSCs have been studied over the Belgrano II Antarctic station for years 2018 and 2019. The methodology applied has been validated by full spherical radiative transfer simulations, which confirm that PSCs can be detected and their altitude estimated with this instrumentation. Moreover, our investigation shows that this method is useful even in presence of optically thin tropospheric clouds or aerosols. PSCs observed in this work have been classified by altitude. Our results are in good agreement with the stratospheric temperature evolution obtained by the global meteorological model ECMWF (European Centre for Medium Range Weather Forecasts) and with satellite PSCs observations from CALIPSO (Cloud-Aerosol-Lidar and Infrared Pathfinder Satellite Observations). To investigate the presence and long-term evolution of PSCs, the methodology used in this work could also be applied to foreseen and/or historical observations obtained with ground-based spectrometers such e. g. those dedicated to Differential Optical Absorption Spectroscopy (DOAS) for trace gas observation in Arctic and Antarctic sites.

Optimization of Procedure for Determining Chlorine Nitrate in the Atmosphere from Ground-Based Spectroscopic Measurements

The procedure for determining the total content of chlorine nitrate (ClONO2) from ground-based measurements of the solar radiation spectra on a Bruker 125HR Fourier spectrometer at the St. Petersburg station (59.88oN, 29.82oE, 20 m above sea level) of the international observational network NDACC is examined. The method was applied to spectra measured in the period from 2009 to 2019, and the results were compared with calculations by the EMAC chemistry-climate model. Good qualitative and quantitative agreement was obtained between the experimental data and the results of numerical modeling. For the period 2009–2017 the average mismatch between model and experiment was 3%, the standard deviation was 43%, and the correlation coefficient was 0.79 ± 0.02, which indicates an adequate description of the variability of the total ClONO2 content by the model. Assessment of the linear trend of the total ClONO2 content showed a significant decrease in the total chlorine nitrate content in the atmosphere over St. Petersburg according both to the ground-based measurements (–2.3 ± 1.9% per year) and to the model (–1.2 ± 0.4% per year).

M-dwarf Eclipsing Binaries with Flare Activity

Abstract The physical properties of 12 eclipsing binaries of M-type dwarfs with superflare activity are characterized by combining the ground-based spectroscopic measurements and the photometric light curves obtained by the Kepler Space Telescope. All of these binary systems have Algol-type orbital configurations. The primary components are mostly of the early M-type dwarfs (M0–M3). Even though the occurrence rate of large flares with energy >1034 erg of the EBs is less than the hyperflaring M dwarfs, the corresponding cumulative flare frequency is in general about a factor of 10 higher than the single M dwarfs with flare activity. This might be the consequence of magnetic interaction between the primary and secondary component of individual binaries. The slow rotators are not as active as the fast rotators, some of which display a possible eclipsing effect in their flare activity.

Europa’s surface water ice crystallinity: Discrepancy between observations and thermophysical and particle flux modeling

Physical processing of Europan surface water ice by thermal relaxation, charged particle bombardment, and possible cryovolcanic activity can alter the percentage of the crystalline form of water ice compared to that of the amorphous form of water ice (the “crystallinity”) on Europa’s surface. The timescales over which amorphous water ice is thermally transformed to crystalline water ice at Europan surface temperatures (80–130 K) suggests that the water ice there should be primarily in the crystalline form, however, surface bombardment by charged particles induced by Jupiter’s magnetic field, and vapor deposition of water ice from Europan plumes, can produce amorphous water ice surface deposits on short timescales. The purpose of this investigation is to determine whether the Europan surface water ice crystallinity derived from ground-based spectroscopic measurements is in agreement with the crystallinity expected based upon temperature and radiation modeling. Using a 1D thermophysical model of Europa’s surface, we calculate an integrated full-disk crystallinity of Europa’s leading hemisphere by incorporating the thermal relaxation of amorphous to crystalline water ice and the degradation of crystalline to amorphous water ice by irradiation. Concurrently, we derive the full-disk crystallinity of Europa’s leading hemisphere using a comparison of near-infrared ground-based spectral observations from Grundy et al. (1999), Busarev et al. (2018), and the Apache Point Observatory in Sunspot, NM, with laboratory spectra from Mastrapa et al. (2008) and the Ice Spectroscopy Lab at the Jet Propulsion Laboratory. We calculate a modeled crystallinity significantly higher than crystallinities derived from ground-based observations and laboratory spectra. This discrepancy may be a result of geophysical processes, such as by vapor-deposited plume material, or it may arise from assumptions and uncertainties in the crystallinity calculations.

Spatial-temporal CO2 variations near St. Petersburg based on satellite and ground-based measurements

The results of studying spatial-temporal CO2 variations near St. Petersburg during 2014–2017 based on satellite measurements (OSO-2 satellite), ground-based spectroscopic and local measurements are presented. According to satellite data the full amplitude of the spatial-temporal variations for the average CO2 mixing ratio (XCO2) amounted to 57.7 ppm (over 14%). The maximal XCO2 spatial variations during one day of observations (17.03.2015) were 46.8 ppm (more than 10%). Comparison of CO2 satellite and ground-based spectroscopic measurements has shown that ground-based measurements in the NDACC observing system after correction of systematic differences from the TCCON system can be used for validation of satellite measurements. Ground-based local measurements of the near-surface CO2 mixing ratio at Peterhof do not correlate with either spectroscopic ground-based or satellite measurements due to both mesoscale CO2 variations and significantly different spatial averaging kernels of direct and remote measurements.

Spatial–Temporal CO2 Variations near St. Petersburg Based on Satellite and Ground-Based Measurements

The results of studying spatial-temporal CO 2 variations near St. Petersburg during 2014–2017 based on satellite measurements (OSO-2 satellite), ground-based spectroscopic and local measurements are presented. According to satellite data the full amplitude of the spatial-temporal variations for the average CO 2 mixing ratio (XCO 2 ) amounted to 57.7 ppm (over 14%). The maximal XCO 2 spatial variations during one day of observations (17.03.2015) were 46.8 ppm (more than 10%). Comparison of CO 2 satellite and ground-based spectroscopic measurements has shown that ground-based measurements in the NDACC observing system after correction of systematic differences from the TCCON system can be used for validation of satellite measurements. Ground-based local measurements of the near-surface CO 2 mixing ratio at Peterhof do not correlate with either spectroscopic ground-based or satellite measurements due to both mesoscale CO 2 variations and significantly different spatial averaging kernels of direct and remote measurements.

Ground-Based Measurements of the Total Column of Freons in the Atmosphere near St. Petersburg (2009–2017)

The results of the first long-term (2009–2017) ground-based spectroscopic measurements of the total content (TC) of a number of freons in Russia are presented. According to measurements in Peterhof, TCs of CFC-11 and CFC-12 decrease at a rate of ~0.6% per year and TC of HCFC-22 grows at a rate of ~2.7% per year, which is in good agreement with independent measurements. The seasonal course of freon TC in the area of St. Petersburg is registered: highs of CFC-11 and CFC-12 are observed in summer and lows are in late winter and spring. For the HCFC-22 TC, the opposite seasonal course is observed, with a maximum in winter and a minimum in summer.

Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star.

The angle between the spin of a star and the orbital planes of its planets traces the history of the planetary system. Exoplanets orbiting close to cool stars are expected to be on circular, aligned orbits because of strong tidal interactions with the stellar convective envelope. Spin-orbit alignment can be measured when the planet transits its star, but such ground-based spectroscopic measurements are challenging for cool, slowly rotating stars. Here we report the three-dimensional characterization of the trajectory of an exoplanet around an M dwarf star, derived by mapping the spectrum of the stellar photosphere along the chord transited by the planet. We find that the eccentric orbit of the Neptune-mass exoplanet GJ 436b is nearly perpendicular to the stellar equator. Both eccentricity and misalignment, surprising around a cool star, can result from dynamical interactions (via Kozai migration) with a yet-undetected outer companion. This inward migration of GJ 436b could have triggered the atmospheric escape that now sustains its giant exosphere.

Study of trends of total CO and CH4 contents over Eurasia through analysis of ground-based and satellite spectroscopic measurements

Trends of total CO and CH4 contents are estimated from satellite AIRS spectrometer data for the Eurasian domain (0–180° E, 0–85° N) for different time periods and seasons. The results are compared with similar estimates, obtained from ground-based spectroscopic measurements at seven stations of the European Network for the Detection of Atmospheric Composition Change (NDACC) and at measurement sites of the Institute of Atmospheric Physics, Russian Academy of Sciences (Zvenigorod Scientific Station (ZSS), Zotto, and Beijing) and St. Petersburg University (Peterhof), located in the study domain. Overall, the total CO decreased over northern Eurasia during the period of 2003–2015 at a rate of 0.05–1.5%/yr, depending on the region; while the total CH4 increased at a rate of 0.16–0.65%/yr. Since 2007, the total CO has been increased during summer and autumn months in most mid- and high-latitude Eurasian background regions, and the total CH4 growth has been accelerated. Changes in the global photochemical system, proceeding against the background of global climate change and, in particular, changes in the “sources/sinks” ratio for minor atmospheric admixtures are suggested as possible causes of this dynamic of trends of the atmospheric CO and CH4 contents.

Ground-based spectroscopic measurements of atmospheric gas composition near Saint Petersburg (Russia)

Since early 2009, high-resolution solar absorption spectra have been recorded at the Peterhof station (59.88°N, 29.82°E) of Saint Petersburg State University located in the suburbs of St. Petersburg. Measurements are made with the Fourier Transform Infrared (FTIR) system, which consists of Bruker IFS 125HR instrument (with maximum spectral resolution of 0.005cm−1) and self-designed solar tracker. We derived total column (TC) of a dozen of atmospheric gases from recorded spectra and performed the error analysis of these retrievals. Furthermore, we analysed the temporal variability of the important climatically active gases, such as H2O, CH4, O3, CO, and NO2 near St. Petersburg and compared our retrievals with independent ground-based and satellite data, as well as with the results of EMAC model numerical simulations. Currently, the results of our measurements and the measuring system are under validation for entering the international Network for the Detection of Atmospheric Composition Change (NDACC).

Comparison results of satellite and ground-based spectroscopic measurements of CO, CH4, and CO2 total contents

A significant amount of satellite and ground-based data on the CO, CO2, and CH4 total contents for 2010–2013 was collected, classified, and analyzed. Transition relations between satellite and groundbased data on the content of impurities under study at different measuring sites (NDACC/ GAW and OIAP RAS stations) with different spatial and temporal resolutions have been found. A high correlation between daily average satellite-measured CO contents (AIRS v6 (R 2 = 0.48–0.96), IASI MetOp-A (R 2 = 0.25–0.86), and MOPITT v6 Joint (R 2 = 0.30–0.83) products, averaging over 1° × 1°) and the ground-based solar spectrometers’ data was ascertained for background conditions. In the case of high pollution of the mixing layer, a significant underestimation of the CO total content (by 1.7–4.7 times, depending on the sensor and observation point) by satellite sensors has been noted. Representative transition relations and correlation coefficients (R 2 ≥ 0.5) between satellite data on daily average CH4 contents and the data from ground-based diffraction spectrometers of A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS) and Fourier spectrometers of GAW stations have been found only for the AIRS sensor. The best correlation with ground-based measurement data on CO2 (R 2 = 0.25 for daily average values, averaging over 1° × 1°) was found for the IASI sensor. The daily average CH4 total contents from the IASI MetOp-A sensor weakly correlate with the ground-based data and with AIRS data.

Consideration of high surface concentrations of hydrochloric acid vapors in ground-based spectroscopic measurements

Spectral measurements show that solar radiation can contain information on extremely high surface concentrations of hydrochloric acid vapors, which leads to the impossibility of estimation of their total content using the background a priori information. An alternative specification of a priori information is suggested, which allows an increase in the number of retrieved values of hydrochloric acid vapor by 10%. The existence of high surface concentrations of the gas is confirmed by the spectral data processing results. A good agreement between estimates of the stratospheric content of hydrochloric acid vapors retrieved from ground-based measurements using the proposed a priori information and independent satellite data is shown: mean differences between data received by the two methods are 4.4%, standard deviation of the differences is 5.7%, and the correlation coefficient is 0.85.

Comparisons of satellite (GOSAT) and ground-based Fourier spectroscopic measurements of methane content near St. Petersburg

The column-average mole fraction of methane measured with hyperspectral methods of ground-based Fourier transform spectroscopy at the Physical Department of St. Petersburg State University (59.9° N, 29.8° E) in 2009–2012 is compared with similar data measured from the Japanese GOSAT satellite. The average mole fraction of methane \(X_{CH_4 } \) from GOSAT data version V01.xx are lower by 17–21 ppb than the corresponding value obtained from ground-based measurements with a standard deviation of about 13 ppb. For the GOSAT data version V02.xx, this difference is about 2 ppb on average, with a standard deviation of about 18 ppb. This corresponds to differences between data on \(X_{CH_4 } \) from the GOSAT satellite and from the TCCON and NDACC networks.

Comparisons of satellite (GOSAT) and ground-based spectroscopic measurements of CO2 content near St. Petersburg

The column-average mole fractions of atmospheric carbon dioxide measured with ground-based Fourier-transform spectroscopy at the Peterhof station of St. Petersburg State University (59.9° N, 29.8° E) in 2009–2011 are compared with similar data obtained with the Japanese GOSAT satellite. The comparison shows that the average mole fractions of CO2 from satellite data version V01.xx are lower by −9.8 ± 3 ppm than the corresponding values obtained from the ground-based measurements. For the GOSAT data version V02.xx, this difference is −4.7 ± 2.6 ppm on the average. Some overestimation of CO2 values in measurements near St. Petersburg in comparison with the ground-based TCCON network data has been revealed indirectly, the causes of which require further explanation.

Ground-based measurements of HF total column abundances in the stratosphere near St. Petersburg (2009–2013)

An analysis of ground-based spectroscopic measurements of hydrogen fluoride total column abundances (HF TCAs) near St. Petersburg for a 4-year period (2009–2013) is performed. The average HF TCA is 1.93 × 1015 cm−2, and the RMS variation (natural variability) for the measurement ensemble is about 20%. The data are in good agreement with measurements collected at the NDACC stations (Bremen and Harestua), taking into account the differences in latitude. The monthly average HF TCAs show seasonal variation with peaks in late winter and early spring and troughs in the period from November to January. The variability of the monthly averages is at a maximum in winter and spring. A comparison of the HF TCAs from ground-based measurements with those from ACE-FTS solar occultation measurements shows that the total abundances from the ground-based data are 12% lower than those from the ACE-FTS data, and the RMS differences depend on the version of the satellite data processing system, being 13 and 16% for versions 2.2 and 3.0, respectively. The calculated ratio between HCl and HF total column abundances is significantly lower in late winter and spring. The linear trend of this ratio is 2.5% per year. Although the trend statistics is insufficient due to the short observation period, the pattern is explained both by the decrease in the stratospheric HCl content and the small increase in HF TCAs over the studied period and is consistent with literature data.

Comparisons of satellite (GOSAT) and ground-based spectroscopic measurements of CH4 content near Saint Petersburg: influence of data collocation

We compared atmospheric column average mole fractions of methane measured with ground-based Fourier transform spectroscopy at the Physical Department of Saint Petersburg State University (59.9° N, 29.8° E) in years 2009–2012 with similar data obtained from the Japanese Greenhouse Gases Observing Satellite (GOSAT) satellite. For the GOSAT data version V02.xx, average and median values of biases between satellite and ground-based methane mole fractions are −(1.7–4.1) ppb and their standard deviations are 10–13 ppb. These values are similar to biases between the GOSAT satellite and the ground-based Total Carbon Column Observation Network and Network for the Detection of Atmospheric Composition Change making Fourier transform spectroscopic observations. Average and median biases for satellite data selected within α = ±1° latitude–longitude vicinity from the ground-based observations site are smaller than those for α = ±3° and α = ±5°.

Ground-based measurements of total column of hydrogen chloride in the atmosphere near St. Petersburg

We present ground-based spectroscopic measurements of the total hydrogen chloride in the atmosphere of Peterhof near St. Petersburg from April 2009 to March 2012. The well-known computer code SFIT-2 (Zephyr-2) was used to interpret the spectra of the solar IR radiation. The random and systematic errors of total column (TC) HCl measurements did not exceed 3.8 and 4.5%. The seasonal behavior of TC HCl in Peterhof is characterized by the presence of a maximum in March–April and a minimum in October–November. There are also extremely small TC HCl values in January–February. The time behavior obtained for Peterhof agrees well with data from nearest stations in the NDACC international network. The ground-based measurements of the TC HCl were compared with satellite measurements with the help of ACE-FTS and MLS instruments. The direct comparisons of coincident (within a day) and collocated (within 500 km) satellite and ground-based measurements showed a correspondence of results within their total errors.

Ground-based spectroscopic measurements of the total nitric acid content in the atmosphere

The results of the first ground-based spectroscopic measurements in Russia of the total content (TC) of nitric acid in the atmosphere near St. Petersburg over the period April 2009–October 2011 are presented. These measurements show a substantial seasonal trend of the HNO3 TC with maximal values in the winter period and early in the spring and minimal values in the summer time. The seasonal trends and variations in the daily mean values of HNO3 TC near St. Petersburg in the winter and spring periods agree well with observations at the Kiruna station of the international NDACC network.