Changing patterns in aerosol concentrations over the Asian region is well documented with a concurrent increase over India and a marked reduction over China. However, aerosol vertical distribution in ...the changing climate is not fully understood. By combining long-term satellite observations from MODIS and CALIOP, here we show rapid changes in the aerosol vertical distribution over the South and East Asia covering India and China. A statistically significant decreasing (increasing) trend in the boundary layer (free troposphere) aerosol concentrations is noticed over India. ERA-Interim reanalysis model suggests that this increase in free tropospheric aerosol concentrations are due to the lifting of boundary layer pollutants through an increase in convection (and vertical velocity) in a changing climate. In contrast, a consistent decreasing trend is observed over China irrespective of the altitude. Interestingly, a decreasing trend in Aerosol Optical Depth is observed over the northwest India and we relate this to an observed increase in precipitation leading to increase in the vegetation. It is also found that long-term oscillations like QBO, ENSO and solar cycle significantly affect the aerosol concentrations. Thus, it is prudent to conclude that background meteorology and dynamics play an important role in changing patterns of aerosol vertical distribution.
Local emission and long-range transport impacts on the observed concentrations (dry air mole fractions) of CO, CO2, and CH4 have been investigated using three years (April 2016 to April 2019) of ...surface measurements at a tropical rural site, Gadanki (13.5° N, 79.2° E) in Southern peninsular India. Gadanki represents the poor coverage area of Greenhouse Gas (GHG) measurements in India and has both local emission and long-range transport influences on its air masses. All the three gases have shown strong seasonality and diurnal variations. Trend analysis showed a significant decreasing trend in CO (14.3 ± 0.2 ppbv/year) and increasing trends in CO2 (2.5 ± 1.2 ppmv/year) and CH4 (11.1 ± 0.03 ppbv/year). CO2 and CH4 trends are marginally higher than the global trends (2.2 ± 0.004 ppmv/year and 7.0 ± 0.001 ppbv/year, respectively) for the same period highlighting the sustained local emission impact on the observed concentrations. Among the three species, CO has been the most local emission impacted species with local emission contribution (to the total observed concentration) varying between 4 and 25% during different seasons with a median value always lying above 10% irrespective of the season. In the case of CO2 and CH4, the local emission contribution found to vary in the range of 0.8–7% and 0.15–3%, respectively. Long-range transport impact dominance over the local emission is observed in CO2 and CH4 during all the seasons. Analysis using MODIS fire count data, Concentration Weighted Trajectory (CWT) and FLEXPART have reconfirmed the combined effect of local and long-range transport impacts on the observed concentrations. Comparison of the IASI MetOp and AIRS satellite data products with surface measurements showed the significant bias and poor representation of the seasonality demonstrating the limitations on the sensitivity of satellite trace gas measurements within the boundary layer.
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•Local emission and long-range transport impacts on CO, CO2, and CH4 have been investigated at a tropical rural site.•CO has been the most local emission impacted species among the three.•Forest fires, agricultural residue and biomass burning have been the dominant local sources.•Trend analysis showed a significant decreasing trend in CO and increasing trends in CO2 and CH4.•Comparison of satellite data with surface measurements showed a significant difference.
In recent years, the middle atmosphere has evoked great scientific interest as long‐term changes can be clearly captured owing to the large perturbation amplitudes at these altitudes. In the present ...study, more than 25 years of the data are used to investigate the long‐term trends in the middle atmosphere by suitably combining the observations from different techniques (Rocketsonde, High‐Resolution Doppler Imager (HRDI)/Upper Atmosphere Research Satellite (UARS), Halogen Occultation Experiment (HALOE)/UARS, Sounding of the Atmosphere using Broadband Emission Radiometry (SABER)/Thermosphere Ionosphere Mesosphere Energetic Dynamics (TIMED), and Mesosphere‐stratosphere‐troposphere (MST) radar) from Indian region. As different instruments/techniques are used and the time periods are not the same, extreme care has been taken while merging various data sets to obtain meaningful long‐term trends. To understand the observed long‐term trends, Whole Atmosphere Community Climate Model–eXtended model simulations for the Indian low‐latitude regions are also used. A significant cooling trend of ~−1.7 ± 0.5 K/decade between 30 and 80 km is noticed. Large decreasing trend (~5 m/s/decade) in the eastward winds is noticed which is significant between 70 and 80 km only changing from strong eastward wind in 1970s to weak westward wind in recent decade. No significant trends are observed in the meridional wind. These observations are well captured by the Whole Atmosphere Community Climate Model–eXtended model simulations while considering changes in concentrations of greenhouse gases including carbon dioxide (CO2), methane (CH4), water vapor (H2O), and chlorofluorocarbon species that cause depletion of stratospheric ozone (O3). Thus, it is prudent to conclude that long‐term decreasing trends in the zonal winds and cooling trends in the temperature in the middle atmosphere are caused to a large extent by greenhouse gases suggesting the role of anthropogenic changes in the dynamics of the middle atmosphere.
Plain Language Summary
In the changing climate, several studies have shown long‐term trends in troposphere, stratosphere, and mesosphere. In general, long‐term trends in the middle atmosphere (10–100 km) can be clearly captured due to increasing amplitudes with the altitude. However, studies on long‐term trends in the temperature and winds over the low latitudes in the middle atmosphere are sparse. In the present study, long‐term trends observed in the temperature and winds obtained from the observations from multiinstrumental data covering more than 25 years is provided. To explain the observed trends we also used Whole Atmosphere Community Climate Model–eXtended model simulations. Long‐term decreasing trends in the zonal winds and cooling trends in the temperature in the middle atmosphere are observed. These observations are clearly captured in the Whole Atmosphere Community Climate Model–eXtended model simulations that examine the long‐term changes in the atmosphere due to the long‐term changes in concentrations of greenhouse gases, suggesting the role of anthropogenic changes in the dynamics of the middle atmosphere.
Key Points
Long‐term trends in the middle atmosphere temperature and winds over Indian region are presented using multiinstrumental data
To explain the observed trends, WACCM‐X model simulations are used for the Indian region while considering major GHGs
WACCM‐X model is able to simulate these observed trends suggesting the role of anthropogenic change on the middle atmosphere
In this paper, solar fed single-input two-output Converter is discussed in the application of low power. The single-diode model is chosen for the solar panel modelling. The performance of this model ...is better in case of varying solar irradiation. It is operated with Maximum Power Point Tracking (MPPT) algorithm to achieve better efficiency. This paper also discusses the comparative study of two important MPPT algorithms such as Advanced Perturb and Observation (APO) and Incremental Conductance (IC) methods. The characteristics curves between power and voltage as well as between current and voltage are obtained from simulation work and these curves are compared with the actual characteristics curve. The solar-fed Zeta-Buck Boost and SEPIC-Cuk converters are analysed as a two output converter. Moreover, the converter has a DC bipolar output voltage with the ground connected power switch. The ground connected switch reduces the sparks on the switch. The system is simulated and modelled using MATLAB software and its performance is tested using real-time simulator using OP-5142.
The paper presents a highly efficient DC-DC Boost converter meant for utility level photovoltaic systems. Solar photovoltaic cells are highly sought-after for renewable energy generation owing to ...their ability to generate power directly. However, the outputs of solar arrays range in lower DC voltage. It is therefore necessary to make use of DC-DC converters that can boost the output voltage and do so consistently by negating the variations in the outputs of solar panels. The variations arise from inconsistencies in sunlight availability, ambient temperature, and shadows, among other factors. The proposed converter topology is found to offer efficiency that is greater than 95% compared to the traditional DC-DC Boost converter. This configuration’s main feature is the implementation of Advanced Perturb & Observation (APO) MPPT algorithm which basically features multiple iterations of perturbation and observation than in conventional P&O MPPT. APO will also minimize the development of oscillations close to the maximum power point in the P-V characteristics compared to the conventional P&O MPPT. The converter will enable drawing consistent and maximum levels of power from solar panels in a more efficient manner. As such, APO’s usage in solar systems will be able to provide for a broader range of utility-level applications.
The authors propose a smart transmission system islanding scheme during an out-of-step (OOS) condition using PMU data. An OOS condition leads to the formation of electrical centers on a few ...transmission lines. The distance relays on the lines misinterpret it as a bolted three-phase fault and trip leading to an uncontrolled system separation. The load-rich islands can blackout due to massive generation-load imbalance. Recent research has shown that the evolution of electrical centers can be tracked by PMUs and hence, distance relays on these lines can be temporarily blocked from operation. The authors now propose an adaptive islanding scheme wherein (i) the islands contain coherent generators and (ii) overall load shed is minimised. In other words, the authors propose a simple and efficient method for determining the optimal cutset using PMU data. The method does not require explicit coherency determination of generators and can be implemented within the time interval of two PMU frames (40 ms in India). Simulation results on the 16-generator system and the Indian power system demonstrate the efficacy of the proposed method.
A multi-instrument campaign was conducted to investigate the changes in ozone vertical distribution during the annular solar eclipse that occurred in the morning hours (08:10 to 11:15 Indian Standard ...Time) on 26 December 2019 using both in-situ and remote sensing observations over Gadanki (13.5oN,79.2oE), India. A series of ozonesondes were launched before and after the solar eclipse along with continuous observations from the Brewer MKIII spectrophotometer and Mesosphere-Stratosphere-Troposphere (MST) radar. An enhancement (~30–60 ppbv) in upper tropospheric (10–18 km) ozone was observed immediately after the solar eclipse along with a reduction in the total ozone by 20 DU, at the maximum of solar obscuration. The MST radar observations and interpretation of meteorological reanalysis data and backward trajectory simulations suggest that this ozone enhancement was due to a downdraft from the stratosphere which began a few hours before the eclipse, as well as long-range transport associated with the sub-tropical jet. A mid-tropospheric (4–10 km) ozone enhancement which also occurred during the eclipse was also produced by the action of the sub-tropical jet. However, the cold point tropopause was significantly lower in height at the maximum of the eclipse, and this region subsequently warmed over a period of several hours. The observations during this event further highlight that background dynamics need to be taken into consideration when evaluating the atmospheric effects of different solar eclipses at tropical latitudes.
•Upper tropospheric ozone enhancement is not connected with the solar eclipse.•Strong subsidence in MST radar during the morning hours of the solar eclipse day.•Mid-tropospheric enhancement due to background dynamics, but not due to eclipse.•Increase in tropospheric columnar ozone and reduction in total ozone due to eclipse.•Decrease in tropopause altitude during the eclipse, higher than previously reported.
Chromium in its hexavalent oxidation state is carcinogenic and wastewater from the electroplating industry is one of the principal sources of pollution. To reduce this toxicity and pave way towards ...environmental safety, a combination of environmental microbiology and chemistry is quite efficient for developing biosorbents to sequester chromium from waste water. Immobilization of
in sodium montmorillonite provides a conducive environment to capture hexavalent chromium. Various characterization techniques such as FTIR, XPS and SEM-EDAX were performed and batch parameters such as pH variation, adsorbent dosage, concentration of metal ion and temperature were optimized. Pseudo second order kinetics coupled with a higher regression coefficient for Freundlich isotherm and a Langmuir adsorption capacity of 22.22 mg g
was achieved for the adsorption process. The adsorption was enhanced by the charge interactions between the protonated clay-
surface and Cr(vi) ions in acidic medium. The biosorbent was stable and easily regenerated using NaOH. Preliminary column studies were performed to test the efficiency of the developed biosorbent at higher volumes on a laboratory scale.
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