Isotopic composition (δ15N, δ18O) of nitrate in high-frequency precipitation events differentiate atmospheric processes and anthropogenic NOx emissions

2021 ◽  
pp. 105971
Author(s):  
Ioannis Matiatos ◽  
Leonard I. Wassenaar ◽  
Lucilena R. Monteiro ◽  
Stefan Terzer-Wassmuth ◽  
Cedric Douence
Keyword(s):  
Isotopic Composition ◽  
High Frequency ◽  
Nox Emissions ◽  
Atmospheric Processes ◽  
Precipitation Events

Combustion Instability and Emission Control by Pulsating Fuel Injection

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Christian Oliver Paschereit ◽  
Ephraim Gutmark
Keyword(s):  
High Frequency ◽  
Fuel Injection ◽  
Low Frequency ◽  
Nox Emissions ◽  
Modulation Amplitude ◽  
Pulsation Frequency ◽  
Symmetric Mode ◽  
Instability Mode ◽  
Secondary Fuel ◽  
Symmetric Instability

Open-loop control methodologies were used to suppress symmetric and helical thermoacoustic instabilities in an experimental low-emission swirl-stabilized gas-turbine combustor. The controllers were based on fuel (or equivalence ratio) modulations in the main premixed combustion (premixed fuel injection (PMI)) or, alternatively, in the secondary pilot fuel. PMI included symmetric and asymmetric fuel injection. The symmetric instability mode responded to symmetric excitation only when the two frequencies matched. The helical fuel injection affected the symmetric mode only at frequencies that were much higher than that of the instability mode. The asymmetric excitation required more power to obtain the same amount of reduction as that required by symmetric excitation. Unlike the symmetric excitation, which destabilized the combustion when the modulation amplitude was excessive, the asymmetric excitation yielded additional suppression as the modulation level increased. The NOx emissions were reduced to a greater extent by the asymmetric modulation. The second part of the investigation dealt with the control of low frequency symmetric instability and high frequency helical instability by the secondary fuel injection in a pilot flame. Adding a continuous flow of fuel into the pilot flame controlled both instabilities. However, modulating the fuel injection significantly decreased the amount of necessary fuel. The reduced secondary fuel resulted in a reduced heat generation by the pilot diffusion flame and therefore yielded lower NOx emissions. The secondary fuel pulsation frequency was chosen to match the time scales typical to the central flow recirculation zone, which stabilizes the flame in the burner. Suppression of the symmetric mode pressure oscillations by up to 20dB was recorded. High frequency instabilities were suppressed by 38dB, and CO emissions reduced by using low frequency modulations with 10% duty cycle.

scholarly journals What controls the isotopic composition of Greenland surface snow?

2014 ◽  
Vol 10 (1) ◽  
pp. 377-392 ◽  
Author(s):  
H. C. Steen-Larsen ◽  
V. Masson-Delmotte ◽  
M. Hirabayashi ◽  
R. Winkler ◽  
K. Satow ◽  
...  
Keyword(s):  
Water Vapor ◽  
Isotopic Composition ◽  
Air Temperature ◽  
Ice Core ◽  
Snow Surface ◽  
Atmospheric Models ◽  
Near Surface ◽  
Core Data ◽  
Surface Snow ◽  
Precipitation Events

Abstract. Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically enabled atmospheric models. However, post-depositional processes linked with snow metamorphism remain poorly documented. For this purpose, monitoring of the isotopic composition (δ18O, δD) of near-surface water vapor, precipitation and samples of the top (0.5 cm) snow surface has been conducted during two summers (2011–2012) at NEEM, NW Greenland. The samples also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between near-surface vapor δ18O and air temperature (0.85 ± 0.11‰ °C−1 (R = 0.76) for 2012). The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess) is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1–5-day periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and near-surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated using the CROCUS snow model that 6 to 20% of the surface snow mass is exchanged with the atmosphere. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or deposition. Comparisons with atmospheric models show that day-to-day variations in near-surface vapor isotopic composition are driven by synoptic variations and changes in air mass trajectories and distillation histories. We suggest that, in between precipitation events, changes in the surface snow isotopic composition are driven by these changes in near-surface vapor isotopic composition. This is consistent with an estimated 60% mass turnover of surface snow per day driven by snow recrystallization processes under NEEM summer surface snow temperature gradients. Our findings have implications for ice core data interpretation and model–data comparisons, and call for further process studies.

scholarly journals A database of multi-year (2004–2010) quality-assured surface solar hourly irradiation measurements for the Egyptian territory

2015 ◽  
Vol 8 (2) ◽  
pp. 737-758 ◽  
Author(s):  
M. Korany ◽  
M. Boraiy ◽  
Y. Eissa ◽  
Y. Aoun ◽  
M. M. Abdel Wahab ◽  
...  
Keyword(s):  
Quality Control ◽  
High Frequency ◽  
High Temporal Resolution ◽  
Atmospheric Processes ◽  
Reliable Source ◽  
Data Files ◽  
Atmospheric Radiative Transfer ◽  
The Individual ◽  
The Impact

Abstract. A database containing the global and diffuse components of the surface solar hourly irradiation measured from 1 January 2004 to 31 December 2010 at eight stations of the Egyptian Meteorological Authority is presented. For three of these sites (Cairo, Aswan, and El-Farafra), the direct component is also available. In addition, a series of meteorological variables including surface pressure, relative humidity, temperature, wind speed and direction... is provided at the same hourly resolution at all stations. The details of the experimental sites and instruments used for the acquisition are given. Special attention is paid to the quality of the data and the procedure applied to flag suspicious or erroneous measurements is described in details. Between 88 and 99 % of the daytime measurements are validated by this quality control. Except at Barrani where the number is lower (13 500), between 20 000 and 29 000 measurements of global and diffuse hourly irradiation are available at all sites for the 7-year period. Similarly, from 9000 to 13 000 measurements of direct hourly irradiation values are provided for the three sites where this component is measured. With its high temporal resolution this consistent irradiation and meteorological database constitutes a reliable source to estimate the potential of solar energy in Egypt. It is also adapted to the study of high-frequency atmospheric processes such as the impact of aerosols on atmospheric radiative transfer. In the next future, it is planned to complete regularly the present 2004–2010 database, which has been placed on the PANGAEA repository (doi:10.1594/PANGAEA.848804) and contains the individual meteorological and irradiation data files of the 8 stations.

scholarly journals Prediction of Transient NOx Emission from Diesel Vehicles Based on Deep-Learning Differentiation Model with Double Noise Reduction

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1702
Author(s):  
Jiaqiang Li ◽  
Yang Yu ◽  
Yanyan Wang ◽  
Longqing Zhao ◽  
Chao He
Keyword(s):  
Time Series ◽  
Diesel Engines ◽  
High Frequency ◽  
Singular Spectrum Analysis ◽  
Low Frequency ◽  
Ensemble Empirical Mode Decomposition ◽  
Support Vector ◽  
Nox Emissions ◽  
Diesel Vehicles ◽  
Original Time

For diesel engines, accurate prediction of NOx (Nitrogen Oxides) emission plays an essential role in virtual NOx sensor development and engine design under situations of actual road driving. However, due to the randomness and uncertainty in the driving process of diesel vehicles, it is difficult to make predictions about NOx emissions. In order to solve this problem, this paper proposes differential models for noise reductions of NOx emissions in time series. First, according to the internal fluctuation of time series, use SSA (Singular Spectrum Analysis) to reduce the noises of the original time series; second, use ICEEMDAN (Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise) to decompose the noise-reducing data into several relatively stable subsequences; third, use the sample entropy to calculate the complexity of each subsequence, and divide the sequences into high-frequency ones and low-frequency ones; finally, use GRU (Gated Recurrent Unit) to complete the prediction of high-frequency sequences and SVR (Support Vector Regression) for the prediction of low-frequency sequences. To obtain the final models, integrate the prediction results of the subsequences. Make comparisons with five single models, SSA single-processing models, and ICEEMDAN single-processing models. The experimental results show that the proposed model can predict the instantaneous NOx emissions of diesel engines better than the single model and the model processed by SSA, and the differentiated model can effectively improve the execution speed of the model.

scholarly journals Precipitation regime and stable isotopes at Dome Fuji, East Antarctica

2016 ◽  
Vol 16 (11) ◽  
pp. 6883-6900 ◽  
Author(s):  
Anna Dittmann ◽  
Elisabeth Schlosser ◽  
Valérie Masson-Delmotte ◽  
Jordan G. Powers ◽  
Kevin W. Manning ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Annual Cycle ◽  
Source Region ◽  
Precipitation Event ◽  
Deuterium Excess ◽  
Antarctic Plateau ◽  
Moisture Source ◽  
The Antarctic ◽  
The Impact ◽  
Precipitation Events

Abstract. A unique set of 1-year precipitation and stable water isotope measurements from the Japanese Antarctic station, Dome Fuji, has been used to study the impact of the synoptic situation and the precipitation origin on the isotopic composition of precipitation on the Antarctic Plateau. The Antarctic Mesoscale Prediction System (AMPS) archive data are used to analyse the synoptic situations that cause precipitation. These situations are investigated and divided into five categories. The most common weather situation during a precipitation event is an upper-level ridge that extends onto the Antarctic Plateau and causes strong northerly advection from the ocean. Most precipitation events are associated with an increase in temperature and wind speed, and a local maximum of δ18O. During the measurement period, 21 synoptically caused precipitation events caused 60 % of the total annual precipitation, whereas the remaining 40 % were predominantly attributed to diamond dust. By combining the synoptic analyses with 5-day back-trajectories, the moisture source regions for precipitation events were estimated. An average source region around a latitude of 55° S was found. The atmospheric conditions in the source region were used as initial conditions for running a Rayleigh-type isotopic model in order to reproduce the measured isotopic composition of fresh snow and to investigate the influence of the precipitation source region on the isotope ratios. The model represents the measured annual cycle of δ18O and the second-order isotopic parameter deuterium excess reasonably well, but yields on average too little fractionation along the transport/cooling path. While simulations with an isotopic general circulation model (GCM) (ECHAM5-wiso) for Dome Fuji are on average closer to the observations, this model cannot reproduce the annual cycle of deuterium excess. In the event-based analysis, no evidence of a correlation of the measured deuterium excess with the latitude of the moisture source region or the corresponding conditions was identified. Contrary to the assumption used for decades in ice core studies, a more northerly moisture source does not necessarily mean a larger temperature difference between source area and deposition site, thus a more depleted precipitation in heavy isotopes with a higher deuterium excess.

scholarly journals Measurement report: Nitrogen isotopes (δ<sup>15</sup>N) and first quantification of oxygen isotope anomalies (Δ<sup>17</sup>O, δ<sup>18</sup>O) in atmospheric nitrogen dioxide

2020 ◽  
Author(s):  
Sarah Albertin ◽  
Joël Savarino ◽  
Slimane Bekki ◽  
Albane Barbero ◽  
Nicolas Caillon
Keyword(s):  
Isotopic Composition ◽  
Nitrogen Dioxide ◽  
Diurnal Cycle ◽  
Nitrogen Isotopes ◽  
Tropospheric Chemistry ◽  
Peroxyl Radicals ◽  
Nox Emissions ◽  
Night Time ◽  
Nitrogen Exchange ◽  
First Time

Abstract. The isotopic composition of nitrogen and oxygen in nitrogen dioxide (NO2) potentially carries a wealth of information about the dynamics of the nitrogen oxides (NOx = nitric oxide(NO) + NO2) chemistry in the atmosphere. While nitrogen isotopes of NO2 are subtle indicators of emissions, NOx chemistry and isotopic nitrogen exchange between NO and NO2, oxygen isotopes are believed to reflect only the O3/NOx/VOC chemical regime in different atmospheric environments. In order to access this potential tracer of the tropospheric chemistry, we have developed an efficient active method to trap atmospheric NO2 on denuder tubes and measured, for the first time, its multi-isotopic composition (δ15N, δ18O, and Δ17O). The δ15N values of NO2 trapped at our site in Grenoble, France, show little variability (−11.8 to −4.9 ‰) with negligible N isotope fractionations between NO and NO2 due to high NO2/NOx ratios. NOx emissions main sources are estimated using a stable isotope model indicating the predominance of traffic NOx emissions in this area. The Δ17O values, however, reveal an important diurnal cycle peaking in late morning at (39.2 ± 1.7) ‰ and decreasing at night until (20.5 ± 1.7) ‰. On top of this diurnal cycle, Δ17O also has substantial variability during the day (from 29.7 to 39.2 ‰), certainly driven by changes in the O3 to peroxyl radicals ratio. The night-time decay of Δ17O(NO2) appears to be driven by NO2 slow removal, mostly from conversion into N2O5, and its formation from the reaction between O3 and emitted NO. Our Δ17O(NO2) measured towards the end of the night is quantitatively consistent with typical values of Δ17O(O3). These preliminary results are very promising for using Δ17O of NO2 as a probe of the atmospheric oxidative activity and for interpreting NO3− isotopic composition records.

scholarly journals What controls the isotopic composition of Greenland surface snow?

2013 ◽  
Vol 9 (5) ◽  
pp. 6035-6076 ◽  
Author(s):  
H. C. Steen-Larsen ◽  
V. Masson-Delmotte ◽  
M. Hirabayashi ◽  
R. Winkler ◽  
K. Satow ◽  
...  
Keyword(s):  
Water Vapor ◽  
Isotopic Composition ◽  
Air Temperature ◽  
Ice Core ◽  
Data Interpretation ◽  
Snow Surface ◽  
Atmospheric Models ◽  
Core Data ◽  
Surface Snow ◽  
Precipitation Events

Abstract. Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically-enabled atmospheric models. However, post-deposition processes linked with snow metamorphism remain poorly documented. For this purpose, a monitoring of the isotopic composition (δ18O, δD) of surface water vapor, precipitation and samples of top (0.5 cm) snow surface has been conducted during two summers (2011–2012) at NEEM, NW Greenland. The measurements also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between surface vapor δ18O and air temperature (0.85 ± 0.11 ‰ °C−1 (R = 0.76) for 2012). The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess) is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1–5 days periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated that 6 to 20% of the surface snow mass is exchanged with the atmosphere using the CROCUS snow model. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or condensation. Comparisons with atmospheric models show that day-to-day variations in surface vapor isotopic composition are driven by synoptic weather and changes in air mass trajectories and distillation histories. We suggest that, in-between precipitation events, changes in the surface snow isotopic composition are driven by these changes in surface vapor isotopic composition. This is consistent with an estimated 60% mass turnover of surface snow per day driven by snow recrystallization processes under NEEM summer surface snow temperature gradients. Our findings have implications for ice core data interpretation and model-data comparisons, and call for further process studies.

Sign in / Sign up

Export Citation Format

Share Document