Seasonal variations in the total content of hydrogen fluoride in the atmosphere

The results of ground-based measurements of the total content (TC) of hydrogen fluoride in the atmosphere in Peterhof near St. Petersburg for one year (from April 2009 through April 2010) using a Bruker IFS125 Fourier spectrometer with a high spectral resolution (0.005 cm^?1) are presented. The well-known computer code SFIT2 (Zephyr-2) was used for the radiation data inversion. Random measurement errors were 1–5% and the systematic error was 5–10%. The seasonal trend of the HF TC in Peterhof is characterized by a minimum in summer and a maximum in winter through early spring and is very close to the seasonal HF TC trend obtained at the Harestua Network for the Detection of Atmospheric Composition Change (NDACC) station located at about the same latitude. A comparison of the St. Petersburg State University (SPbSU) ground-based measurements with the data of satellite HF TC measurements (with an ACE-FTS instrument) showed a good quantitative agreement of the results for the entire period of observations. According to our ground-based measurements and the satellite measurements with the ACE-FTS instrument, the mean values of the HF TC and its rms variations during the period under investigation are 1.77 × 10¹⁵ and 1.80 × 10¹⁵ cm^?2 (difference 1.5%) and 21 and 18%, respectively.     

Comparing data obtained from ground-based measurements of the total contents of O<Subscript>3</Subscript>, HNO<Subscript>3</Subscript>,HCl,and NO<Subscript>2</Subscript> and from their numerical simulation

Chemistry climate models of the gas composition of the atmosphere make it possible to simulate both space and time variations in atmospheric trace-gas components (TGCs) and predict their changes. Both verification and improvement of such models on the basis of a comparison with experimental data are of great importance. Data obtained from the 2009–2012 ground-based spectrometric measurements of the total contents (TCs) of a number of TGCs (ozone, HNO₃, HCl, and NO₂) in the atmosphere over the St. Petersburg region (Petergof station, St. Petersburg State University) have been compared to analogous EMAC model data. Both daily and monthly means of their TCs for this period have been analyzed in detail. The seasonal dependences of the TCs of the gases under study are shown to be adequately reproduced by the EMAC model. At the same time, a number of disagreements (including systematic ones) have been revealed between model and measurement data. Thus, for example, the EMAC model underestimates the TCs of NO₂, HCl, and HNO₃, when compared to measurement data, on average, by 14, 22, and 35%, respectively. However, the TC of ozone is overestimated by the EMAC model (on average, by 12%) when compared to measurement data. In order to reveal the reasons for such disagreements between simulated and measured data on the TCs of TGCs, it is necessary to continue studies on comparisons of the contents of TGCs in different atmospheric layers.     

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.     

NO<Subscript>2</Subscript> content variations near St. Petersburg as inferred from ground-based and satellite measurements of scattered solar radiation

An automatic spectral complex developed at the Institute of Physics, St. Petersburg State University, is described. This complex is used for regular ground-based spectroscopic measurements of the total NO₂ content in the vertical column of the atmosphere during the twilight and daylight hours of the day near St. Petersburg (Petrodvorets). In 2004–2006, a number of ground-based twilight measurements of the total NO₂ content were obtained near St. Petersburg, and variations in the NO₂ content in the troposphere were estimated from the results of daytime ground-based measurements. An example of the spatial annual mean distribution of the NO₂ content (central and northern Europe, northwestern Russia) based on the data of satellite measurements over the period 2003–2005 is presented. This example demonstrates the main sources of anthropogenic pollution. An increase in the mean annual contents of tropospheric NO₂ near Moscow and St. Petersburg is preliminarily estimated for the entire period of satellite observations with the GOME instrument at about 30–40% over ten years.     

Nitrogen dioxide in the air basin of St. Petersburg: Remote measurements and numerical simulation

The results of ground-based and satellite spectroscopic measurements of the tropospheric NO₂ content near St. Petersburg in January–March 2006 are presented. It is shown that the increased concentrations of NO₂ observed in St. Petersburg and its vicinities in this period were caused by NO₂ accumulation due to unfavorable weather conditions, which is confirmed by an analysis of meteorological data and the results of a numerical simulation of the dispersion of urban air pollutants. Data from satellite and ground-based measurements agree with each other satisfactorily (a correlation coefficient of 0.5) and with model calculations of tropospheric NO₂ conducted for the coordinates of a station of ground-based measurements (a correlation coefficient of 0.6). The HYSPLIT dispersion model also made it possible to estimate the scale of the NO₂ spatial-temporal variability in the near-surface layer in the vicinities of St. Petersburg.     

Variations in the column-average dry-air mole fractions of CO2 in the vicinity of St. Petersburg

The results obtained from ground-based spectroscopic measurements of column-average dry-air mole fractions of CO₂ in the atmosphere over the St. Petersburg region are given for the period April 2009–October 2011 (～900 measurement runs, 151 measurement days). These results show significant variations in the CO₂ mixing ratio in the atmosphere over the St. Petersburg region. The minimum value of this mixing ratio (373.1 ppm) was observed on April 27, 2011, and its maximum value (420.8 ppm) was observed on February 10, 2010. The typical seasonal behavior of the CO₂ mixing ratio with its summer minimum was observed in 2009. In July 2010 and 2011, the values of the CO₂ mixing ratio increased apparently due to high air temperatures. In 2010 an additional contribution to this increase in the CO₂ mixing ratio could have been made by strong natural fires.     

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.     

Intercomparison of satellite and ground-based ozone total column measurements

Ozone total column (OTC) measurements made in 2009–2012 near St. Petersburg by a Fourier Transform Infrared (FTIR) spectrometer (Peterhof, St. Petersburg State University (SPbSU)), an M-124 filter ozonometer, and a Dobson spectrophotometer (Voeikovo, MGO), as well as measurements made by a spectrometer ozone monitoring instrument (OMI) (onboard the AURA satellite) have been analyzed and compared. Comparisons have been performed both between ensembles of ground-based measurement data, as well as between ground-based and satellite data. It has been shown that the standard deviation for all devices is 2.5–4.5%; here, the FTIR and Dobson instruments measuring the direct sun are in better agreement with OMI than the M-124 ozonometer measuring the zenith-scattered solar radiation as well. A seasonal cycle in discrepancy with amplitude of 1.5% has been detected between two series of OTC measurements made by M-124 and OMI instruments for a total of 850 days. In fall and winter, the ground-based measurements underestimate the OTC values in comparison with satellite data; in spring and summer, the situation is reversed: ground-based data overestimate the OTC values. Also, it has been revealed that FTIR measurements systematically overestimate the OTC values in comparison with other instruments: from 1.4% (for Dobson) to 3.4% (for OMI). Taking into account the spatial and temporal discrepancy of independent ensembles of measurements and an analysis of standard deviations between ground-based and satellite measurement data, the FTIR spectrometer (SPbSU) can be recommended for OTC satellite data validation.     

Comparison of the satellite and ground-based measurements of the hydrogen fluoride content in the atmosphere

Satellite and ground-based measurements of the hydrogen fluoride (HF) total content (TC) are analyzed and compared. The HF profiles measured with an FTS device on the ACE satellite are used to calculate the TC and compare it with the ground-based measurements near St. Petersburg in 2009–2011. A comparison indicated that the seasonal variations in HF TC based on two independent measurements are in good qualitative agreement. Rare (nine) cases of direct comparison between two measurement types coordinated with respect to time (during the day) and site (no farther than 500 km) gave the following characteristics: the average difference is 8% and satellite data predominate over ground data; the standard deviation of a difference is 7%. In two cases of close measurement pairs (closer than 200 km), a comparison gave differences of 1 and 7%. The statistical characteristics of differences between two measurement types are in good agreement with the independent comparison of the ACE-FTS HF TC measurements with the NDACC network data.     

Seasonal features of quasi-biennial variations of NO<Subscript>2</Subscript> stratospheric content derived from ground-based measurements

Seasonal and latitudinal distributions of amplitudes of quasi-biennial variations in total NO₂ content (NO₂ TC), total ozone content (TOC), and stratospheric temperature are obtained. NO₂ TC data from ground-based spectrometric measurements within the Network for the Detection of Atmospheric Composition Change (NDACC), TOC data from satellite measurements, and stratospheric temperature data from ERA-Interim reanalysis are used for the analysis. The differences in the NO₂ TC diurnal cycles are identified between the westerly and easterly phases of the quasi-biennial oscillations (QBO) of equatorial stratospheric wind. The QBO effects in the NO₂ TC, TOC, and stratospheric temperature in the Northern (NH) and Southern (SH) hemispheres are most significant in the winter–spring periods, with essential differences between the NH and SH. The NO₂ TC in the Antarctic is less for the westerly phase of the QBO than that for the easterly phase, and the NO₂ TC quasi-biennial variations in the SH mid-latitudes are opposite of the variations in the Antarctic. In the NH, the winter values of the NO₂ TC are generally less during the westerly QBO phase than during the easterly phase, whereas in spring, on the contrary, the values for the westerly QBO phase exceed those for the easterly phase. Along with NO₂, the features of the quasi-biennial variations of TOC and stratospheric temperature are discussed. Possible mechanisms of the quasi-biennial variations of the analyzed parameters are considered for the different latitudinal zones.     

Analysis of variability of the CO, NO2, and O3 contents in the troposphere near St. Petersburg

The space-time variability of the fields of CO, NO₂, and O₃ concentrations and contents in the troposphere of northwestern Russia is analyzed on the basis of experimental data and the results of numerical modeling. The influence that the St. Petersburg emission has on the concentrations and contents of CO, NO₂, and O₃ in the troposphere is estimated for March 2006. A comparison of the measurements of the total CO content and the tropospheric NO₂ content with the results of modeling showed a qualitative and, in come cases, quantitative agreement between the results of calculations and experimental data. When synoptic conditions are determined, the St. Petersburg train can be detected at a distance of more than 300 km, which can affect the atmospheric air quality in adjacent countries.     

Stratospheric NO2 content according to data from ground-based measurements of solar IR radiation

Atmospheric NO₂ content data obtained from regular ground-based measurements of solar IR radiation in the St. Petersburg region using a spectrometer with a high spectral resolution are analyzed. The absorption spectra of the NO₂ multiplet in the vicinity of ～2915 cm^?1 allow one to obtain data on variations in the stratospheric total content of NO₂ in 2009–2011. The accuracy of these data is estimated from their comparison with data obtained from independent ground-based and satellite measurements. The parameters of the seasonal cycle of the stratospheric content of NO₂ are estimated. The body of data accumulated during these measurements in the IR region made it possible to isolate the component of a daytime photochemical increase in the stratospheric content of NO₂ and estimate its rate.     

Volume transport of the Soya Warm Current revealed by bottom-mounted ADCP and ocean-radar measurement

The vertical structure of the Soya Warm Current (SWC) was observed by a bottom-mounted acoustic Doppler current profiler (ADCP) in the region of the SWC axis near the Soya Strait during a 1-year period from May 2004. The ADCP data revealed a marked seasonal variability in the vertical structure, with positive (negative) vertical shear in summer and fall (winter and spring). The volume transport of the SWC is estimated on the basis of both the vertical structure observed by the ADCP and horizontal structure observed by the ocean radars near the strait. The transport estimates have a minimum in winter and a maximum in fall, with the yearly-averaged values in the range of 0.94–1.04 Sv (1 Sv = 10⁶ m³ s⁻¹). These lie within a reasonable range in comparison to those through other straits in the Japan Sea.     

Seasonal and interannual variability in phytoplankton and nutrient dynamics along Line P in the NE subarctic Pacific

We analysed mixed-layer seasonal and interannual variability in phytoplankton biomass and macronutrient (NO₃ and Si(OH)₄) concentrations from three decades of observations, and nitrogen uptake rates from the 1990s along Line P in the NE subarctic Pacific. Chlorophyll a concentrations near 0.35 mg m⁻³ were observed year-round along Line P except at the nearshore station (P4) where chlorophyll a concentrations in spring were on average 2.4 times the winter values. In contrast, the temporal variability in carbon-to-chlorophyll ratios at the two main end members of Line P (P4 and OSP) was high. Large seasonal and interannual variability in NO₃ and Si(OH)₄ concentration were observed along Line P. Highest upper mixed-layer (top 15 m) nutrient concentrations occurred on the continental shelf in late summer and early fall due to seasonal coastal upwelling. Beyond the shelf, maximum nutrient concentrations increased gradually offshore, and were highest in late winter and early spring due to mixing by winter storms. Interannual variations in upper mixed-layer nutrient concentrations beyond the shelf (>128°W) were correlated with E-W winds and the PDO since 1988 but were not correlated with either climate index between 1973 and 1981. Despite differences in nutrient concentration, nutrient utilization (ΔNO₃ and ΔSi(OH)₄) during the growing season were about 7.5 μM at all offshore stations. Variations in ΔNO₃ were correlated with those of ΔSi(OH)₄. The annual cycle of absolute NO₃ uptake (ρNO₃) and NH₄ uptake (ρNH₄) rates by phytoplankton in the upper mixed-layer showed a weak increasing trend from winter to spring/summer for the period 1992-1997. Rates were more variable at the nearshore station (P4). Rates of ρNO₃ were low along the entire line despite abundant NO₃ and low iron (Fe), at the offshore portion of Line P and sufficient Fe at the nearshore station (P4). As a result, new production contributed on average to only 32 ± 15% of the total nitrogen (N) uptake along Line P. NO₃ utilization in the NE subarctic Pacific is probably controlled by a combination of environmental variables, including Fe, light and ambient NH₄ levels. Elevated ambient NH₄ concentrations seem to decrease the rates of new production (and f-ratios) in surface waters of the oceanic subarctic NE Pacific. Contrary to expectation, phytoplankton biomass, nutrient utilization (ΔNO₃ and ΔSi(OH)₄), and nitrogen uptake (ρNO₃ + ρNH₄) varied relatively little along Line P, despite significant differences in the factors controlling phytoplankton composition assemblages and production. Future studies would benefit from including other variables, especially light limitation, to improve our understanding of the seasonal and interannual variability in phytoplankton biomass and nutrients in this region.     

Integral emission of nitrogen oxides from the territory of St. Petersburg based on the data of mobile measurements and numerical simulation results

The results of spectroscopic measurements of tropospheric NO₂ content performed on a closed route along the circular road around the city of St. Petersburg in 2012, 2014, and 2015 are presented. A procedure for determining the integral emission of NO _x based on the data of measurements on the route enveloping the sources under study is described. An analysis of the experimental data together with the results of a numerical simulation of air pollutant dispersion (the HYSPLIT model) provided an estimate of the total volume of NO _x emitted by all sources located inside the circular road. The average emission rate of NO _x according to the sources of the megacity of St. Petersburg is 57000 t/yr, which correlates satisfactorily with the official data of a municipal inventory of the sources of air pollution (62000–63 000 t/yr).     

Seasonal dissolved inorganic carbon variations in the Greenland Sea and implications for atmospheric CO2 exchange

During the 1993–1995 period of minimal deep convection in the Greenland Sea, the dissolved inorganic carbon concentration within the surface waters varied dramatically on the seasonal time scale, with average summer and winter values of 2064 (±10) and 2150 (±5) μmol kg⁻¹, respectively, indicative of a vigorous annual carbon cycle. In contrast, there was very little interannual variability throughout these three years. While primary production largely depleted the surface nutrient supplies in spring and summer, generating a strong seasonal CO₂ drawdown, a combination of relatively shallow remineralization and mixed-layer deepening brought essentially all of the carbon consumed by photosynthesis back into contact with the atmosphere before winter. This re-release of the inorganic carbon that had been consumed by phytoplankton earlier in the year was more than sufficient to counteract the cooling-induced increase in the carbon carrying capacity of the water during fall and winter, reducing the potential for atmospheric carbon dioxide absorption by the Greenland Sea over the same period.     

Annual cycle of fCO2 under sea-ice and in open water in Prydz Bay, East Antarctica

The annual cycle of dissolved nutrients and the fugacity of CO₂ (fCO₂), calculated from the concentration of dissolved inorganic carbon (DIC) and pH, was studied over a 14-month long period (December 1993 to February 1995) at a site in Prydz Bay near Davis Station, Vestfold Hills, East Antarctica. Significant spring decreases in fCO₂ began under the sea-ice in mid-October, when both water column and sea-ice algal activity resulted in the removal of nutrients and DIC and increased pH. Minimum fCO₂ (<100 μatm) and lowest nutrient and DIC concentrations occurred in December and January. The low summer fCO₂ values were clearly the result of biological activity. The seasonal depletion of dissolved nitrate reached 85% in mid-summer when chlorophyll-a concentrations exceeded 15 mg m⁻³. Oceanic uptake of carbon dioxide from the atmosphere, calculated from the fugacity difference and daily wind speeds, averaged more than 30 mmol m⁻² day⁻¹ during the summer ice-free period. This exchange replaced approximately half of the DIC consumed by biological activity. Apparent nutrient utilisation ratios (C/N/P) were close to Redfield values. In autumn fCO₂ began to rise, continuing slowly well into winter, and reaching a maximum close to modern atmospheric values between July and September. This increase can be attributed to a combination of local remineralisation of organic carbon in the water column and the steady increase in the mixing depth of the water column. At first glance, this suggests that air–sea equilibration occurred in winter despite the sea-ice cover, perhaps by horizontal circulation from regions outside the pack ice, or through openings in the ice. However, the persistent 15 to 20% undersaturation of dissolved oxygen throughout the winter suggests an alternate explanation. The late winter fCO₂ level may represent a characteristic established by global circulation, so that as a result of increasing atmospheric CO₂ concentrations, these Antarctic waters are in transition from being a winter-time source of CO₂ to the atmosphere to becoming a sink. Our fCO₂ observations emphasize the need to address seasonal variations in assessing Antarctic contributions to the oceanic control of atmospheric CO₂.     

Seasonal variability in nitrogenous nutrition of phytoplankton assemblages in the northeastern subarctic Pacific Ocean

Nitrogen uptake rates, and physical, chemical and biological characteristics of the euphotic zone were studied in winter, spring and late summer during the period 1992–1994 along a transect (Line P) extending from the continental slope off the southwest corner of Vancouver Island (British Columbia, Canada; station P4; 49°N, 127°W) to open waters in the NE Pacific (OSP; 50°N, 145°W). Nitrate (NO₃⁻) and silicic acid (Si(OH)₄) concentrations increased offshore during every season. Lowest NO₃⁻ and Si(OH)₄ values were observed during late summer and spring, and highest during winter throughout the euphotic zone. For spring and late summer, surface depletion of NO₃⁻ was observed at the inshore end of the transect, while offshore concentrations were never limiting for phytoplankton growth. Silicic acid was never depleted at any depth or station during the period covered by this study. Ammonium (NH₄⁺) and urea concentrations exhibited a patchy distribution along the transect, with no seasonal variations. Chlorophyll a and particulate nitrogen did not show a consistent longitudinal pattern from year to year. In general, the highest concentrations of chlorophyll a and particulate nitrogen were measured during the late summer cruises, with lower values in spring and lowest in winter. Phytoplankton assemblages were numerically dominated by flagellates <5 μm throughout the water column on each cruise transect. Ammonium, urea and NO₃⁻ uptake rates represented on average 55, 24 and 21% of the depth-integrated total nitrogen uptake, both longitudinally and seasonally; hence, phytoplankton utilized nitrogen in the following order: NH₄⁺>urea>NO₃⁻ along Line P. Ammonium may have inhibited the uptake rates of NO₃⁻ and urea. Urea uptake rates were lower than those of NH₄⁺, but higher values were occasionally observed at a few depths along the transect, particularly during the spring of 1993. Depth-integrated NH₄⁺ uptake rates were generally higher inshore, while NO₃⁻ uptake rates showed higher values offshore during most seasons. In contrast, urea uptake rates did not exhibit a consistent longitudinal trend. The depth-integrated f-ratio ranged from 0.05 to 0.37 with an average of 0.21 for all stations and cruises, and was overestimated on average by 36% when urea was excluded from the calculation. On a yearly basis, primary productivity in the NE subarctic Pacific was based on regenerated nitrogen.     

The three-dimensional structure and seasonal variation of the North Pacific meridional overturning circulation

The three-dimensional structure and the seasonal variation of the North Pacific meridional overturning circulation (NPMOC) are analyzed based on the Simple Ocean Data Assimilation data and Argo profiling float data.The NPMOC displays a multi-cell structure with four cells in the North Pacific altogether.The TC and the STC are a strong clockwise meridional cell in the low latitude ocean and a weaker clockwise meridional cell between 7°N and 18°N,respectively, while the DTC and the subpolar cell are a weaker ...     

Comparison of Ground-Based Measurement Results of Total Ozone near St. Petersburg

Izvestiya, Atmospheric and Oceanic Physics - This paper compares the results of ground-based measurements of the total ozone content (TOC) near St. Petersburg for the period of 2009–2020. The...