Long-term Measurement Data Research Articles

Dissolved Oxygen in a Shallow Ice-Covered Lake in Winter: Effect of Changes in Light, Thermal and Ice Regimes

Oxygen conditions in ice-covered lakes depend on many factors, which, in turn, are influenced by a changing climate, so detection of the oxygen trend becomes difficult. Our research was based on data of long-term measurements of dissolved oxygen (2007–2020), water temperature, under-ice solar radiation, and snow-ice thickness (1995–2020) in Lake Vendyurskoe (Northwestern Russia). Changes of air temperature and precipitation in the study region during 1994–2020 and ice phenology of Lake Vendyurskoe for the same period based on field data and FLake model calculations were analyzed. The interannual variability of ice-on and ice-off dates covered wide time intervals (5 and 3 weeks, respectively), but no significant trends were revealed. In years with early ice-on, oxygen content decreased by more than 50% by the end of winter. In years with late ice-on and intermediate ice-off, the oxygen decrease was less than 40%. A significant negative trend was revealed for snow-ice cover thickness in spring. A climatic decrease of snow-ice cover thickness contributes to the rise of under-ice irradiance and earlier onset of under-ice convection. In years with early and long convection, an increase in oxygen content by 10–15% was observed at the end of the ice-covered period, presumably due to photosynthesis of phytoplankton.

Analysis of the spatial-temporal distribution of lightning discharges in the North Caucasus

The organization of lightning protection measures is based on information about the nature of the distribution of lightning discharges, their number and the current value in the region of the location of the protection objects. Therefore, the most relevant direction of the study is to clarify the existing recommendations in the field of lightning protection. In the article, based on the data of long-term measurements of the LS 8000 lightning direction finding system located in the North Caucasus, the analysis of the registration of lightning parameters is carried out. The revealed regularities of the distribution of lightning discharges over the territory in different periods of the year are the basis for the approximation equations developed by the authors, which are used to describe the space-time density of lightning. Maps of the distribution of the number of lightning discharges per square kilometer obtained from the initial data and constructed according to the developed equations are presented, and the relevance of the results obtained is evaluated.

Annoyance, perception, and physiological effects of wind turbine infrasound.

Even though some individuals subjectively associate various symptoms with infrasound, there are very few systematic studies on the contribution of infrasound to the perception, annoyance, and physiological reactions elicited by wind turbine sound. In this study, sound samples were selected among long-term measurement data from wind power plant and residential areas, both indoors and outdoors, and used in laboratory experiments. In the experiments, the detectability and annoyance of both inaudible and audible characteristics of wind turbine noise were determined, as well as autonomic nervous system responses: heart rate, heart rate variability, and skin conductance response. The participants were divided into two groups based on whether they reported experiencing wind turbine infrasound related symptoms or not. The participants did not detect infrasonic contents of wind turbine noise. The presence of infrasound had no influence on the reported annoyance nor the measured autonomic nervous system responses. No differences were observed between the two groups. These findings suggest that the levels of infrasound in the current study did not affect perception and annoyance or autonomic nervous system responses, even though the experimental conditions corresponded acoustically to real wind power plant areas.

A process-based coal swelling model: Bridging the gaps between localized swelling and bulk swelling

Injection of CO2 and coal seam gas production induce coal swelling/shrinkage. Laboratory tests indicate that coal swelling may go through several stages from localized swelling at fracture surfaces to bulk rock swelling. The coal Langmuir swelling strain constant normally ranges from 0 to 0.04. This study provides a process-based coal swelling model that covers the whole swelling procedure. We account for three swelling strains, videlicet, the matrix swelling strain, fracture swelling strain, and bulk rock swelling strain. Dynamic partial separation coefficients are employed to quantify the contributions of the matrix swelling strain to bulk swelling and the fracture (cleat) aperture reduction, bridge the gaps between localized swelling and bulk swelling, and link the three types of strains. This model is inserted into a permeability model and verified against permeability measurement and rock swelling data. The three samples used for verification are bituminous coals from the Illinois Basin (depth of ~ 200 m) in the US and Henan Province in China (depth of ~ 310 m). In essence, the swelling model is also applicable to other coal types with a linear relationship between the matrix swelling strain and adsorbed gas content. By matching with long-term permeability measurement data, multiple permeability evolution stages are observed due to the swelling transition. Sensitivity analyses show that the matrix block size, matrix swelling properties, and diffusivity control the duration, occurrence, and magnitude of matrix swelling’s contribution to local and bulk swelling during swelling transition, while rock bridge swelling properties have a marginal influence on coal swelling.

Indirect Economic Effects of Vertical Indoor Green in the Context of Reduced Sick Leave in Offices

Low indoor humidity has been shown to influence the transmission of respiratory diseases via air. A certain proportion of sick leave in offices is therefore attributable to dryness of air. An improvement in these conditions thus means a reduction in sick leave, which is accompanied by cost savings for companies. Vertical indoor greening has a verifiable positive effect on air humidity, especially in winter months. In this article, the correlation between improved air humidity in greened rooms and reduction of sick leave due to improved air humidity was described. The resulting indirect economic effect was determined by comparing the costs for construction, green care, and technical maintenance of indoor greenery with savings due to lower sick leave. Based on long-term measurement data on air humidity and temperature, and actual cost values for three buildings, located in Vienna, Austria, with 6 greened and 3 reference rooms without greenery, the correlation of the method was derived and finally formulated in a generalized way using dimensioning factors. Only considering the influence on air humidity, profitability of 6.6 m2 vertical greening installed in an example office with six workplaces equipped with technical ventilation and saving of two sick days already results after about 4.5 years.

Effects of groundwater exploitation and recharge on land subsidence and infrastructure settlement patterns in Shanghai

Abstract Land subsidence is a severe geo-hazard in coastal regions and represents a great threat to infrastructure. Based on long-term measurement data, including that for deep compaction from vertical multipoint extensometers, land subsidence and infrastructural settlement from leveling surveys, groundwater levels in multiple confined aquifers, and hydrogeological conditions, this study investigates the effects of groundwater exploitation and recharge on land subsidence and the settlement of infrastructure in Shanghai, China. Further, groundwater exploitation and the consequent responses of piezometric heads in the multiple confined aquifers of Shanghai soft deposits are discussed. Subsequently, regional land subsidence, local deep-soil deformation, and infrastructural settlement are analyzed in terms of groundwater exploitation. It is found that the subsidence pattern is related to the trend of groundwater exploitation and the variation of piezometric heads in the aquifers, which can be roughly divided into three phases. Subsidence funnels could occur, and could be interpreted according to the differences in groundwater exploitation intensity and the spatial variability of lithology. Since the towers of Nanpu Bridge are located within the area of the subsidence funnel, this could be the main reason for the differential settlement of the bridge.

The influence of cumulus clouds on fluctuations in down welling microwave radiation of the atmosphere in the resonance absorption band of water vapor 18...27 GHz

Problem formulating. The nature of fluctuations in the microwave radiation of the atmosphere remains poorly understood. A number of questions, related to the nature of radiation fluctuations near the lines of resonant absorption of various atmospheric components, the intensity of fluctuations at large spatial and temporal intervals requires further study. The influence of various meteorological factors on the intensity of radiation fluctuations requires a deeper consideration. Goal. The goal is to reveal the spectral features of spatio-temporal fluctuations in downward radiation of the atmosphere in the region of the water vapor resonance 18−27 GHz and to estimate the influence of cumulus clouds of various vertical extent on the intensity of fluctuations. Result. Based on the data of long-term measurements of down welling radiation brightness temperature 18−27.2 GHz, the analysis of the spectra of structural function for wide range of temporal intervals is carried out. It is shown that the spectrum of radiation fluctuations in a cloudless atmosphere is similar to the absorption spectrum in water vapor. The spectra of fluctuations in atmospheric radiation under conditions of cumulus cloud cover of various vertical extent are presented. Practical meaning. Radiation fluctuations should be taken into account when creating systems for remote sensing of the atmosphere and the Earth’s surface. They affect the quality of radiometric measurements and radio astronomy observations. The data on fluctuations in atmospheric radiation gathered during this research can be useful for assessing the spatial and temporal fluctuations in the phase delay, for taking into account the influence of atmosphere during the radio interferometric measurements and when observing radiation sources in the diagrammatic modulation mode.

Study of Trends in Concentrations of Basic Air Pollutants in the Malopolska Province

Abstract The purpose of the paper was to analyse the trends observed at air monitoring stations in the Malopolska Province - one of the most polluted regions in Poland. The study was carried out on the basis of long-term measurement data registered at five selected stations of automatic monitoring of air quality in the Malopolska Province. Trends evaluation was made on the basis of mean annual concentrations, taken from the database of the Chief Inspectorate for Environmental Protection in Poland. Separately for each basic air pollutant, such as SO2, NO2, NOx, CO, PM10 and O3, trend lines and their linear equations were determined to illustrate the direction of changes in concentrations. The obtained equations of the trend lines indicate the threat to the environment in the Malopolska Province. Based on the results obtained it can be concluded that for recent years there has been observed the concentration decrease of main air pollutants, except of tropospheric ozone.

Impact of COVID-19 on environmental noise emitted from the port

Identification of noise sources and their ranking is a crucial part of any noise abatement program. This is a particularly difficult task when a complex source, such as a seaport, is considered. COVID-19 epidemic has had a significant impact on environmental noise related to road, rail, air and ship traffic and provided a unique opportunity to observe immediate noise reduction. In order to identify the noise sources, whose reduction was most effective in reducing noise from the port area, this study compared and quantified noise emissions between the historical and epidemic periods. Environmental noise measurements from three noise monitoring stations at the port boundary were analysed. In addition, noise emissions from ship, road, rail and industry as well as meteorological data in the historical pre – COVID-19 (January 2018–February 2020) and COVID-19 (April 2020) period were analysed in detail. The characteristics of the noise sources mentioned, geographical data and noise measurements were used to develop and validate a noise model of the port area, which was used to calculate noise contour maps. Our results show that the reduction in noise levels observed at all monitoring stations coincides with the reduced shipping traffic. The A weighted equivalent sound pressure levels in the day, evening and night periods were reduced by 2.2 dB to 5.7 dB compared to the long-term averages, and the area of the 55 dB day-evening-night noise contour was reduced by 23%. Compared to the historical period, the number of people exposed to noise levels above 55 dB(A) in the day-evening-night period due to shipping and industrial activities was reduced by 20% in the COVID-19 period. Such results show that environmental noise generated by moored ships is a problem for port cities that should be regulated internationally. In addition, this paper provides precise guidance on noise emission characteristics, ship categorisation and the post-processing of long-term measurement data, taking into account wind conditions and undesired sound events, which can be applied to future research at other locations near shipping ports and used to prepare strategies for noise reduction in ports.

Modeling of Mass Balance Variability and Its Impact on Water Discharge from the Urumqi Glacier No. 1 Catchment, Tian Shan, China

Originating in the Tian Shan mountains, Urumqi River plays a key role in terms of water supply to downstream areas. In its headwaters, Urumqi Glacier No. 1 (UG1) is the largest glacier contributing to water discharge. Assessing its response to the changing climatic conditions in the area is of major importance to quantify future water availability. We here apply COSIPY, a COupled Snowpack and Ice surface energy and mass balance model in PYthon, to UG1, implementing a new albedo parameterization which integrates site-specific bare-ice albedo values on a pixel-by-pixel basis observed by remote sensing. We assess model performance threefold: quantitatively based on long-term measurement data of (1) surface mass balance (SMB) and (2) water discharge as well as qualitatively (3) comparing simulated snow line altitudes to such imated on the basis of time-lapse photography. Comparison of the modeled SMB with annually-averaged data from ablation stakes reveals that COSIPY including the new albedo parameterization accounts for 57.6% of the variance observed in the measurements. The original albedo parameterization performs only slightly inferior (57.1%). Glacier-wide comparison between modeled and glaciological SMB shows high agreement. In terms of discharge prediction, COSIPY reproduces onset and duration of the discharge season well. Estimated discharge from the whole catchment shows shortcomings in exactly matching the measured times series, but interannual variability is captured.

A Study on Live Load Deflection Criteria of Long-Span Steel Bridges

Under-clearance of bridges is one of the major considerations when planning and designing bridges. Especially for sea-crossing bridges, under-clearance is more important for safe passage of ships. Long span cable bridges with steel orthotropic deck usually show relatively large deflections and excessive deflections may be not only disadvantageous to the clearance plan, but also a problem in bridge serviceability. The clearance of sea-crossing bridge is designed with air draft from the waterline to top of mast, ship’s trim, psychological free space, sea level, height of wave and bridge deflection by live loads. At design stage, bridge engineers need a live load deflection limit to ensure adequate clearance. The limitation of live load deflection is also considered for ensuring the serviceability of vibration of bridges. For vibrational serviceability, the live load deflection limit is expressed as a ratio to the span or the formula by natural frequency. On the other hand, some standards specify vibration serviceability limit by peak or root-mean-square (RMS) acceleration. The purpose of this study is to propose new deflection limit criteria for long span steel cable bridges based on analysis and long-term measurement data. Structural analysis was performed on two steel suspension and three steel cable-stayed bridges with more than 200 m of main span under design live load model of DL24 and new live load model KL510 in limit state design code. Also, the deflection limit criterion was evaluated by probabilistic method using the deflection data measured for 1 year. The results of this study are expected to be useful data for bridge engineers designing long span steel cable bridges.

Application of Mathematical Models ROMUL and Romul_Hum for Estimating CO2 Emission and Dynamics of Organic Matter in Albic Luvisol under Deciduous Forest in the South of Moscow Oblast

The aim of this study was to validate the ROMUL and Romul_Hum simulation models based on the data of long-term measurements of soil respiration performed by the Institute of Physicochemical and Biological Problems in Soil Sciences of the Russian Academy of Sciences in the south of Moscow oblast (54°50′ N, 37°34′ E). We estimated the dynamics of carbon stocks and soil CO2 emission for three scenarios of plant litterfall compiled with the account of experimental data on the composition and mass of litterfall entering the gray forest soil (Albic Luvisol) under secondary deciduous forest. The calculations of long-term series of temperature and moisture content in the forest litter and upper organo-mineral soil horizons in simulation experiments are based on the real data on air temperature and precipitation for 1973–2016. The correspondence of simulation results to the data of field measurements was better for the Romul_Hum model, which comprises a description of the effects related to the vital activity of soil fauna, leading to the formation of different fractions of soil organic matter. The best correspondence of simulated values of CO2 emission, carbon stocks, and the C : N ratios in gray forest soil horizons to field data was for the litter scenarios, which excluded the fraction of small branches. The revealed differences between the simulated and real values of soil parameters are explained by specific features of the input and transformation of different litterfall fractions, which are not always taken into account during soil sampling. The results of the study attract the attention to the uncertainties of estimates of carbon budget in forest ecosystems due to the difficulties of accounting both large wood residues (dead tree and coarse branches debris) and smaller wood fractions in the litterfall.

A Study on the Long-Term Measurement Data Analysis of Existing Cable Stayed Bridge Using ARX Model

Various sensors have been installed in cable-stayed bridges to monitor the behavior of structures and external conditions. These sensors alert the administrator to take appropriate action when an abnormal signal is detected. Although inherent meaningful information about the history of structural responses in long-term accumulated measurement data are available, the methodology for utilizing such data in the long-term point of view has not yet been established. Structural response is determined by the mechanical principle of external loads and the structural system characteristics. Assuming that structural responses have a certain pattern in a constant condition, the state of the structure can be estimated to have changed or not through an analysis of the pattern variation of the measured data. This study utilizes the temperature and displacement data of a cable-stayed bridge to analyze the pattern variation of the measurement data. An autoregressive model is used to define the pattern of the time series data. A pattern model is then constructed with the data adopted as a reference for comparison. The compared data are applied to the pattern model to simulate the data reflecting the reference data pattern. Subsequently, the simulated data are compared with the actual data, and the pattern difference is computed through the error discriminant index.

Predicting individual tree growth of high-value timber species in mixed conifer-broadleaf forests in northern Japan using long-term forest measurement data

ABSTRACT Quantifying individual tree growth of economically high-value timber species is important for the simulation and development of forest management options. Long-term permanent plot data provides crucial information of forest stand dynamics that can be used to predict individual tree growth. In this study, we developed individual tree basal area growth models of three high-value timber species: monarch birch (Betula maximowicziana), castor aralia (Kalopanax septemlobus), and Japanese oak (Quercus crispula) in a cool temperate mixed forest in northern Japan using long-term measurement data (1968–2016) collected in permanent plots. Data included species, diameter at breast height, and survival status, and stand management history. We applied linear mixed-effects modelling to predict the individual tree basal area growth as a function of individual tree size, competition, and forest management. Model prediction followed by leave-one-out cross validation revealed a correlation between predicted and observed basal area increments with r values of 0.62, 0.73, and 0.70 and root mean square errors values of 10.44, 7.91, and 11.62 cm2/year for monarch birch, castor aralia, and Japanese oak, respectively. The individual tree growth models developed in this study will provide valuable information for species-specific forest management of economically high-value timber species.

Total column water vapour retrieval from S-5P/TROPOMI in the visible blue spectral range

Abstract. Total column water vapour has been retrieved from TROPOMI measurements in the visible blue spectral range and compared to a variety of different reference data sets for clear-sky conditions during boreal summer and winter. The retrieval consists of the common two-step DOAS approach: first the spectral analysis is performed within a linearized scheme and then the retrieved slant column densities are converted to vertical columns using an iterative scheme for the water vapour a priori profile shape, which is based on an empirical parameterization of the water vapour scale height. Moreover, a modified albedo map was used combining the OMI LER albedo and scaled MODIS albedo map. The use of the alternative albedo is especially important over regions with very low albedo and high probability of clouds like the Amazon region. The errors of the total column water vapour (TCWV) retrieval have been theoretically estimated considering the contribution of a variety of different uncertainty sources. For observations during clear-sky conditions, over ocean surface, and at low solar zenith angles the error typically is around values of 10 %–20 %, and during cloudy-sky conditions, over land surface, and at high solar zenith angles it reaches values around 20 %–50 %. In the framework of a validation study the retrieval demonstrates that it can well capture the global water vapour distribution: the retrieved H2O vertical column densities (VCDs) show very good agreement with the reference data sets over ocean for boreal summer and winter whereby the modified albedo map substantially improves the retrieval's consistency to the reference data sets, in particular over tropical land masses. However, over land the retrieval underestimates the VCD by about 10 %, particularly during summertime. Our investigations show that this underestimation is likely caused by uncertainties within the surface albedo and the cloud input data: low-level clouds cause an underestimation, but for mid- to high-level clouds good agreement is found. In addition, our investigations indicate that these biases can probably be further reduced by the use of improved cloud input data. For the general purpose we recommend only using VCDs with cloud fraction <20 % and AMF >0.1, which represents a good compromise between spatial coverage and retrieval accuracy. The TCWV retrieval can be easily applied to further satellite sensors (e.g. GOME-2 or OMI) for creating uniform, long-term measurement data sets, which is particularly interesting for climate and trend studies of water vapour.

Investigations on Low Frequency Noises of On-Shore Wind Turbines

The expansion of renewable energy usage is one of the major social tasks in Europe and therefore requires acceptance and support from the population. In the case of onshore wind turbines, the complaints of local residents are often interpreted as infrasound disturbances conceivably caused by wind turbine operation. To improve the acceptance for wind energy projects, national standards and regulations need to incorporate such low frequency effects. This contribution presents long-term acoustic measurement data of low frequency noise recorded directly near wind turbines (emission) and inside of residential buildings (immission) with the objectives to identify the signal characteristics and main influential parameters. Different locations (wind farm and individual turbine), wind conditions, and time ranges are evaluated. It is shown that various frequency content below 150 Hz (harmonics of blade passing frequency, etc.) is connected to the rotation of the rotor blade and the operation of the generator. Furthermore, stable atmospheric conditions are determined to be of high importance for the transmission of the characteristic signals. For future research, this work also serves as an example for low frequency sound pressure data during operation and shutdown of wind turbines.

Comprehensive radiofrequency electromagnetic field measurements and assessments: a city center example.

In this study, radiofrequency electromagnetic field (RF-EMF) measurements were carried out between 2016 and 2018 in one the largest provinces of Turkey; measurement results are compared with the limit values determined by International Commission on Non-Ionizing Radiation Protection (ICNIRP) and Turkey's Information and Communication Technologies Authority (ICTA). In the first stage of a three-phase evaluation, short-term RF-EMF measurements were conducted in 500 locations over a 2-year period. In the second stage, short-term RF-EMF measurement results were analyzed to determine selected locations for long-term RF-EMF measurements to be carried out, including variation of RF-EMF during the day. In the last stage, band selective measurements were taken and the main sources of RF-EMF in the environment were determined. Overall, RF-EMF values do not exceed the limits determined by ICNIRP and ICTA, and they are below levels that threaten public health. In the short-term RF-EMF measurements, RF-EMF levels doubled after fourth generation (4G) systems were introduced. In the long-term RF-EMF measurements, RF-EMF values in the day are 35.4% more than at night. The total measured RF-EMF within the city center is 99.3% base station sourced. Among the six main RF-EMF sources, the devices operating in UMTS2100 band have the most contribution to total RF-EMF of medium with 31.2%. Additionally, we found short-term average electric field strength data are best described by the "exponential distribution," while long-term RF-EMF measurement data is best described by the "Burr distribution."

Responses of gaseous sulfuric acid and particulate sulfate to reduced SO2 concentration: A perspective from long-term measurements in Beijing

SO2 concentration decreased rapidly in recent years in China due to the implementation of strict control policies by the government. Particulate sulfate (pSO42−) and gaseous H2SO4 (SA) are two major products of SO2 and they play important roles in the haze formation and new particle formation (NPF), respectively. We examined the change in pSO42− and SA concentrations in response to reduced SO2 concentration using long-term measurement data in Beijing. Simulations from the Community Multiscale Air Quality model with a 2-D Volatility Basis Set (CMAQ/2D-VBS) were used for comparison. From 2013 to 2018, SO2 concentration in Beijing decreased by ~81% (from 9.1 ppb to 1.7 ppb). pSO42− concentration in submicrometer particles decreased by ~60% from 2012–2013 (monthly average of ~10 μg·m−3) to 2018–2019 (monthly average of ~4 μg·m−3). Accordingly, the fraction of pSO42− in these particles decreased from 20–30% to <10%. Increased sulfur oxidation ratio was observed both in the measurements and the CMAQ/2D-VBS simulations. Despite the reduction in SO2 concentration, there was no obvious decrease in SA concentration based on data from several measuring periods from 2008 to 2019. This was supported by the increased SA:SO2 ratio with reduced SO2 concentration and condensation sink. NPF frequency in Beijing between 2004 and 2019 remains relatively constant. This constant NPF frequency is consistent with the relatively stable SA concentration in Beijing, while different from some other cities where NPF frequency was reported to decrease with decreased SO2 concentrations.

Long-term displacement measurement of full-scale bridges using camera ego-motion compensation

Civil infrastructures experience long-term deflection as a result of persistent and transitory loadings, including self-weight, pre-stress, traffic, temperature variation, and stress redistributions due to damage. Thus, long-term displacement is an important safety indicator that can be widely employed in structural health monitoring. However, its measurement is challenging because of the errors induced by the ego-motion of sensors. Researchers have attempted to compensate for the motion-induced error in computer vision-based displacement measurement methods for full-scale civil structures by using fixed objects in the background. Because remotely located objects cannot fully provide six degrees-of-freedom (6-DOF) camera motions, further developments are necessary for complete error compensation. This paper proposes a long-term displacement measurement strategy that uses computer vision-based ego-motion compensation. The proposed system consists of main and sub-cameras attached to each other. While the main camera employs the conventional computer vision-based method for displacement measurement, the sub-camera measures the ego-motions of the dual-camera system from which the motion-induced errors are estimated and compensated for. The proposed long-term displacement measurement algorithm was numerically validated, and the sub-camera was found to provide a noticeable error compensation. A laboratory-scale test showed that the motion-induced error was reduced from 44.1 mm to 1.1 mm. A field application conducted upon a newly constructed railway bridge provided continuous long-term displacement measurement data, which were consistent with LiDAR-based displacement measurements and numerical predictions.

Reconstruction of the diurnal behavior of the concentration of chlorophyll in the surface and bottom water of the coastal zone of Lake Baikal on the basis of empirical calibration of fluorescence characteristics

The paper presents the analysis of comparing the of synchronous measurements of fluorescence characteristics and the concentration of chlorophyll in Baikal water. The empirical coupling coefficient was determined and, according to the data of long-term measurements of fluorescence characteristics, the daily cycle of the concentration of chlorophyll was restored for different seasons of the year.