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The vertical distribution of the tropospheric ozone column concentration (OCC) in China from 2005 to 2020 was analysed based on the ozone profile product of the ozone monitoring instrument (OMI). The annual average OCC in the lower troposphere (OCC LT ) showed an increasing trend, with an average annual increase of 0.143 DU. The OCC in the middle troposphere showed a downward trend, with an average annual decrease of 0.091 DU. There was a significant negative correlation between the ozone changes in the two layers. The monthly average results show that the peak values of OCC LT occur in May or June, the middle troposphere is significantly influenced by topographic conditions, and the upper troposphere is mainly affected by latitude. Analysis based on multi-source data shows that the reduction in nitrogen oxides (NO x ) and the increase in volatile organic compounds (VOCs) weakened the titration of ozone generation, resulting in the increase in OCC LT . The increase in vegetation is closely related to the increase in OCC LT , with a correlation coefficient of up to 0.875. The near-surface temperature increased significantly, which strengthened the photochemical reaction of ozone. In addition, the increase in boundary layer height also plays a positive role in the increase in OCC LT .

To investigate changes in the ozone (O 3) chemical production regime over the contiguous United States (CONUS) with accurate knowledge of concentrations of its precursors, we applied an inverse modeling technique with Ozone Monitoring Instrument (OMI) tropospheric nitrogen dioxide (NO 2) and total formaldehyde (HCHO) retrieval products in the summers of 2011, 2014, and 2017, years in which United States National Emission Inventory were based. The inclusion of dynamic chemical lateral boundary conditions and lightning-induced nitric oxide emissions significantly account for the contribution of background sources in the free troposphere. Satellite-constrained nitrogen oxide (NO x) and non-methane volatile organic compounds (NMVOCs) emissions mitigate the discrepancy between satellite and modeled columns: the inversion suggested 2.33–2.84 (1.07–1.34) times higher NO x over the CONUS (over urban regions) and 0.28–0.81 times fewer NMVOCs emissions over the southeastern United States. The model-derived HCHO/NO 2 column ratio shows gradual spatial changes in the O 3 production regime near urban cores relative to previously defined threshold values representing NO x and VOC sensitive conditions. We also found apparent shifts from the NO x -saturated regime to the transition regime (or the transition regime to the NO x -limited regime) over the major cities in the western United States. In contrast, rural areas, especially in the east-southeastern United States, exhibit a decreased HCHO/NO 2 column ratio by −1.30 ± 1.71 with a reduction in HCHO column primarily driven by meteorology, becoming sensitive to VOC emissions. Results show that incorporating satellite observations into numerical modeling could help policymakers implement appropriate emission control policies for O 3 pollution. • Top-down estimated NO x and NMVOCs emissions enable us to have accurate knowledge of the ozone chemical regime. • The dynamic lateral boundary conditions and lightning-induced emission improve the model performance in the upper atmosphere. • Many urban regions have shifted to NOx-limited condition, while the southeastern U.S. becomes sensitive to VOC emissions. [ABSTRACT FROM AUTHOR]

We address the lack of temporal information on ship emissions, and report on rapid short-term variations of satellite-derived ship NO _x emissions between 2005 and 2012 over European seas. Our inversion is based on OMI observed tropospheric NO _2 columns and GEOS-Chem simulations. Average European ship NO _x emissions increased by ∼15% from 2005 to 2008. This increase was followed by a reduction of ∼12% in 2009, a direct result of the global economic downturn in 2008–2009, and steady emissions from 2009 to 2012. Observations of ship passages through the Suez Canal and satellite altimeter derived ship densities suggests that ships in the Mediterranean Sea have reduced their speed by more than 30% since 2008. This reduction in ship speed is accompanied by a persistent 45% reduction of average, per ship NO _x emission factors. Our results indicate that the practice of ‘slow steaming’, i.e. the lowering of vessel speed to reduce fuel consumption, has indeed been implemented since 2008, and can be detected from space. In spite of the implementation of slow steaming, one in seven of all NO _x molecules emitted in Europe in 2012 originated from the shipping sector, up from one in nine in 2005. The growing share of the shipping contributions to the overall European NO _x emissions suggests a need for the shipping sector to implement additional measures to reduce pollutant emissions at rates that are achieved by the road transport and energy producing sectors in Europe.

To evaluate the real reductions in sulfur dioxide (SO _2 ) emissions from coal-fired power plants in China, Ozone Monitoring Instrument (OMI) remote sensing SO _2 columns were used to inversely model the SO _2 emission burdens surrounding 26 isolated power plants before and after the effective operation of their flue gas desulfurization (FGD) facilities. An improved two-dimensional Gaussian fitting method was developed to estimate SO _2 burdens under complex background conditions, by using the accurate local background columns and the customized fitting domains for each target source. The OMI-derived SO _2 burdens before effective FGD operation were correlated well with the bottom-up emission estimates ( R = 0.92), showing the reliability of the OMI-derived SO _2 burdens as a linear indicator of the associated source strength. OMI observations indicated that the average lag time period between installation and effective operation of FGD facilities at these 26 power plants was around 2 years, and no FGD facilities have actually operated before the year 2008. The OMI estimated average SO _2 removal equivalence (56.0%) was substantially lower than the official report (74.6%) for these 26 power plants. Therefore, it has been concluded that the real reductions of SO _2 emissions in China associated with the FGD facilities at coal-fired power plants were considerably diminished in the context of the current weak supervision measures.

We have used data from the Ozone Monitoring Instrument (OMI) aboard NASA's Earth Observing System (EOS) Aura satellite over the period 2004–11 to describe the characteristics of surface ultraviolet (UV) irradiance at Escudero Station (62°12′S, 58°57′W). The station is located on King George Island (northern Antarctic Peninsula). Temperatures in summer are frequently above 0°C, and the surrounding ocean is typically ice-free. We found that the UV irradiance at Escudero is driven by the Antarctic ozone hole (which annually in spring leads to significant variations in the ozone) and by clouds (which are more frequent and have a larger optical depth compared with other Antarctic sites). The combined effect of ozone and clouds led to significant variations in the surface UV. The variability (taken as the standard deviation of the UV estimates retrieved from OMI) is typically greater than 30% at Escudero, but may reach values greater than 50% in spring. The consistency of OMI-derived data was checked by using ground-based spectral measurements carried out under controlled conditions in January 2011. [ABSTRACT FROM AUTHOR]

We compare three datasets of high-resolution O3 cross sections and evaluate the effects of using these cross sections on O3 profile retrievals from OMI UV (270–330nm) measurements. These O3 cross sections include Brion–Daumont–Malicet (BDM), Bass–Paur (BP) and a new dataset measured by Serdyuchenko et al. (SGWCB), which is made from measurements at more temperatures and in a wider temperature range than BDM and BP, 193–293K. Relative to the BDM dataset, the SGWCB data have systematic biases of −2 to +4% for 260–340nm, and the BP data have smaller biases of 1–2% below 315nm but larger spiky biases of up to ±6% at longer wavelengths. These datasets show distinctly different temperature dependences. Using different cross sections can significantly affect atmospheric retrievals. Using SGWCB data leads to retrieval failure for almost half of the OMI spatial pixels, producing large negative ozone values that cannot be handled by radiative transfer models and using BP data leads to large fitting residuals over 310–330nm. Relative to the BDM retrievals, total ozone retrieved using original SGWCB data (with linear temperature interpolation/extrapolation) typically shows negative biases of 5–10 DU; retrieved tropospheric ozone column generally shows negative biases of 5–10 DU and 5–20 DU for parameterized and original SGWCB data, respectively. Compared to BDM retrievals, ozone profiles retrieved with BP/SGWCB data on average show large altitude-dependent oscillating differences of up to ±20–40% biases below ~20km with almost opposite bias patterns. Validation with ozonesonde observations demonstrates that the BDM retrievals agree well with ozonesondes, to typically within 10%, while both BP and SGWCB retrievals consistently show large altitude-dependent biases of up to ±20–70% below 20km. Therefore, we recommend using the BDM dataset for ozone profile retrievals from UV measurements. Its improved performance is likely due to its better characterization of temperature dependence in the Hartley and Huggins bands. [ABSTRACT FROM AUTHOR]

Abstract: Satellite observations may improve the areal coverage of particulate matter (PM) air quality data that nowadays is based on surface measurements. Three statistical methods for retrieving daily PM2.5 concentrations from satellite products (MODIS-AOD, OMI-AAI) over the San Joaquin Valley (CA) are compared – Linear Regression (LR), Generalized Additive Models (GAM), and Multivariate Adaptive Regression Splines (MARS). Simple LRs show poor correlations in the western USA (R 2 ≅ 0.2). Both GAM and MARS were found to perform better than the simple LRs, with a slight advantage to the MARS over the GAM (R 2 = 0.71 and R 2 = 0.61, respectively). Since MARS is also characterized by a better computational efficiency than GAM, it can be used for improving PM2.5 retrievals from satellite aerosol products. Reliable PM2.5 retrievals can fill in missing surface measurements in areas with sparse ground monitoring coverage and be used for evaluating air quality models and as exposure metrics in epidemiological studies. [Copyright &y& Elsevier]

The advent of satellite data has provided a source of independent information to monitor trends in tropospheric nitrogen dioxide levels. To interpret these trends, one needs to know the sensitivity of the satellite retrieved NO2 column to anthropogenic emissions. We have applied a chemistry transport model to investigate the sensitivity of the modeled NO2 column, sampled at the OMI (Ozone Monitoring Instrument) overpass time and location and weighted by the OMI averaging kernel, to emission sources across Europe. The most important contribution (∼35%) in Western Europe is made by road transport. Off-road transport and industrial combustion each contribute 10%-15% across continental Europe. In Eastern Europe, power plant contributions are of comparable magnitude as those of road transport. To answer the question if the OMI-NO2 trends can be translated directly into emission changes, we assessed the anticipated changes in OMI-NO2 between 2005 and 2020. Although the results indicated that for many countries, it is indeed possible, for medium- and small-sized coastal countries, the contribution of the increasing shipping emissions in adjacent sea areas may mask a significant part of national emission reductions. This study highlights the need for a combined use of models, a priori emission estimates and satellite data to verify emission trends. [ABSTRACT FROM AUTHOR]

Abstract: High-temperature requirement protein A2 (HtrA2), a serine protease, localizes in the mitochondria and has diverse roles, including maintenance of mitochondrial homeostasis and regulation of cellular apoptosis. HtrA2 (also known as Omi) is associated with many neurodegenerative diseases, including Parkinson disease. By employing agarose gel electrophoresis, a fluorescent dye, PicoGreen, intercalation into mtDNA, and long-range PCR (LR-PCR), we showed that mitochondrial DNA conformational stability is related to HtrA2. Nicked forms of mtDNA were produced through reactive oxygen species generated by loss of HtrA2 protease activity, and mtDNA mutations frequently occurred in HtrA2−/− cells, but not in HtrA2+/+ cells. We found conformational changes in mtDNA from the brain tissue of mnd2 mutant mice that lack the serine protease activity of HtrA2. Overexpression of HtrA2 with protease activity targeted to mitochondria only was able to restore mtDNA conformational stability in HtrA2−/− MEF cells. Nuclear-encoded mtDNA repair genes, including POLG2, Twinkle, and APTX1, were significantly upregulated in HtrA2−/− cells. Electron microscopy showed that mitochondrial morphology itself was not affected, even in HtrA2−/− cells. Our results demonstrate that HtrA2 deficiency causes mtDNA damage through ROS generation and mutation, which may lead to mitochondrial dysfunction and consequent triggering of cell death in aging cells. [Copyright &y& Elsevier]

Abstract: Horizontal and vertical distributions of dust aerosols over northern China were investigated for the period June 2006 to May 2011 using A-Train satellite constellation data and ground-based measurements. Surface observations at 675 meteorological stations showed that dust events occurred most frequently in the Taklamakan and Gobi deserts. In the Taklamakan Desert, the dust aerosol content was high throughout the year, as seen from the distributions of the Moderate-Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) and the Ozone Monitoring Instrument (OMI) UV-absorption aerosol index (AAI). In the Taklamakan and Gobi deserts, the AOD and AAI reached maxima in spring and minima in winter. In the eastern part of northern China, AOD reached a maximum in summer and a minimum in fall, whereas AAI was high in winter and spring and low in summer and fall due to seasonal differences in the main aerosol type. The dust observations revealed strong seasonal variations in dust coverage area and height, with maxima in spring and summer and minima in fall and winter. The transportation of dust aerosols in all seasons was confined largely between 35°N and 45°N. The mean height of the dust layer top varied and showed strong seasonal variation in all regions, with values higher than 4km in spring and about 2km in winter. The Taklamakan Desert experienced higher occurrence of dust events than other regions throughout the year. Dust occurrence decreased dramatically over the eastern part of northern China in summer because of surface vegetation and precipitation. Simulation results by the HYSPLIT model were similar to the distribution of dust aerosols observed by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) during the same period. [Copyright &y& Elsevier]

Abstract: Remote sensing may be a useful tool for exploring spatial variability of air pollution exposure within an urban area. To evaluate the extent to which satellite data from the Ozone Monitoring Instrument (OMI) can resolve urban-scale gradients in ground-level nitrogen dioxide (NO2) within a large urban area, we compared estimates of surface NO2 concentrations derived from OMI measurements and US EPA ambient monitoring stations. OMI, aboard NASA''s Aura satellite, provides daily afternoon (∼13:30 local time) measurements of NO2 tropospheric column abundance. We used scaling factors (surface-to-column ratios) to relate satellite column measurements to ground-level concentrations. We compared 4138 sets of paired data for 25 monitoring stations in the South Coast Air Basin of California for all of 2005. OMI measurements include more data gaps than the ground monitors (60% versus 5% of available data, respectively), owing to cloud contamination and imposed limits on pixel size. The spatial correlation between OMI columns and corrected in situ measurements is strong (r =0.93 for annual average data), indicating that the within-urban spatial signature of surface NO2 is well resolved by the satellite sensor. Satellite-based surface estimates employing scaling factors from an urban model provide a reliable measure (annual mean bias: −13%; seasonal mean bias: <1% [spring] to −22% [fall]) of fine-scale surface NO2. We also find that OMI provides good spatial density in the study region (average area [km2] per measurement: 730 for the satellite sensor vs. 1100 for the monitors). Our findings indicate that satellite observations of NO2 from the OMI sensor provide a reliable measure of spatial variability in ground-level NO2 exposure for a large urban area. [Copyright &y& Elsevier]

Abstract: Daily average total ozone Microtops measurements obtained during several campaigns conducted from 2001 to 2011 at latitudes from 31 to 68°N and in different seasons are compared with satellite observations. The Microtops ozone is derived using different wavelength combinations (Channel I, 305.5/312.5nm; Channel II, 312.5/320nm; and Channel III, 305.5/312.5/320nm). Satellite data from TOMS, OMI, GOME, and GOME-2 are used in the comparison. The three Microtops channels show a high correlation with the satellite retrievals. Channel I shows the best results and produces a mean bias deviation (MBD) less than 2.14% with respect to TOMS, OMI and GOME. The MBD increases to 3% in the comparison against GOME-2, due to the small number of available data. In addition, the total ozone content provided by Channel I displays the more stable behavior during the ten-year period. The Channel III total ozone shows MBD values smaller than those observed for Channel I. However the Channels II and III present a larger variability and show a larger spread of the data. Consequently, Channel I appears as the best option for long term measurements with Microtops. [Copyright &y& Elsevier]

Abstract: Lightning is a particularly significant NO x source in the middle and upper troposphere where it affects tropospheric chemistry and ozone. Because the version-4 Community Multiscale Air Quality Modeling System (CMAQ) does not account for NO x emission from lightning, it underpredicts NO x above the mixed layer. In this study, the National Lightning Detection Network™ (NLDN) lightning data are applied to the CMAQ model to simulate the influence of lightning-produced NO x (LNO x ) on upper tropospheric NO x and subsequent ozone concentration. Using reasonable values for salient parameters (detection efficiency ∼95%, cloud flash to ground flash ratio ∼3, LNO x production rate ∼500 mol N per flash), the NLDN ground flashes are converted into total lightning NO x amount and then vertically distributed on 39 CMAQ model layers according to a vertical-distribution profile of lightning N mass. This LNO x contributes 27% of the total NO x emission during 15 July ∼7 September 2006. This additional NO x reduces the low-bias of simulated tropospheric O3 columns with respect to OMI tropospheric O3 columns from 10 to 5%. Although the model prediction of ozone in upper troposphere improves by ∼20 ppbv due to lightning-produced NO x above the southeastern and eastern U.S.A., the improved ozone prediction is still ∼20–25 ppbv lower than ozonesonde measurements. [Copyright &y& Elsevier]

El Convenio sobre el trabajo marítimo, 2006, que entrará en vigor en agosto de 2013, unifica normas adoptadas por la OIT desde 1920. Constituye el «cuarto pilar» del régimen de reglamentación marítima internacional, junto con tres convenios de la OMI sobre seguridad y control de la contaminación en el mar. Según los autores, el reto consistirá en hacerlo cumplir dentro de los marcos actuales de inspección por el Estado rector del puerto y por el Estado del pabellón. Técnicamente, la responsabilidad recae en el segundo, pero dada la proliferación de pabellones de conveniencia, el papel del primero resultará crucial, al igual que la formación de los inspectores. [ABSTRACT FROM AUTHOR]

Résumé. La convention du travail maritime, 2006, qui entrera en vigueur le 20 août 2013, regroupe des dizaines de normes de l'OIT adoptées depuis les années 1920. Elle a été décrite comme le «quatrième pilier» de la réglementation internationale maritime, aux côtés de trois grandes conventions de l'OMI sur la sécurité en mer et la prévention de la pollution marine. Selon les auteurs, le défi consistera à l'appliquer au moyen des mécanismes réglementaires existants, soit la mise en œuvre par l'Etat du pavillon et le contrôle par l'Etat du port. Techniquement, la responsabilité repose sur les premiers, mais la prolifération des pavillons de complaisance donne à penser que ces derniers joueront également un rôle crucial, tout comme, dans ces deux cas, la formation des inspecteurs. [ABSTRACT FROM AUTHOR]

Objective: To analyze the molecular mechanisms of skeletal muscle cells apoptosis induced by heavy-load exercise with Omi as the entry point., Methods: One hundred and twenty-six adult SD rats were randomly divided into five groups: control group(C), eccentric exercise group (E), simple blocking group (U), DMSO group (D) and exercise block group (EU). In addition to the C group, the other four groups were randomly divided into 0 h after experiment, 12 h after experiment, 24 h after experiment, 48 h after experiment and 72 h after experiment with 6 rats in each group. E and EU group were submitted to a heavy-load exercise on a treadmill down a 16° decline, 16 m/min for 90 minutes. U, D and EU group were one-time intervened with drugs. U and EU groups were intraperitoneally injected with 1.5 μmol/kg ucf-101, D group were intraperitoneally injected with 1.5 μmoL/kg 0.5% DMSO. The rats were sacrificed in batches at different time points after experiment, then the soleus were saved to detect the Caspase-3,-8,-9,-12 activities and protein expressions of Omi and XIAP., Results: Compared with group C, the mitochondrial distribution and morphology appeared the typical ultrastructure pathological changes, the opening degree of MPTP was increased significantly ( P ＜0.01) or ( P ＜0.05), protein expressions of Omi and XIAP were increased significantly ( P ＜0.01 or P ＜0.05), the activities of Caspase-9 and Caspase-3 were increased significantly ( P ＜0.01 or P ＜0.05) in group E. Compared with group C, there was no significant difference in XIAP protein and caspase-9, - 3 activities in group U and Group D. The change trend of XIAP protein and Caspase-9, - 3 activities was the same as those between EU group and E group, but the change range of XIAP protein in EU group was significantly higher than that in E group ( P ＜0.01), and the change ranges of caspase-9, - 3 activities in EU group were significantly lower than those in E group ( P ＜0.01)., Conclusion: A single heavy-load exercise can induce changes in the mitochondria morphology and structure in rats, open the high permeability of MPTP, and improve the expression of Omi protein, then through its downstream XIAP-Caspase pathway, start the mitochondrial apoptosis pathway mediated by caspase-9, and finally lead to myocyte apoptosis. The inhibition of Omi can reduce the cell apoptosis level of motor induced skeletal muscle cells.

The unprecedented increase in anthropogenic activities, coupled with the prevailing climatic conditions, has increased the aerosol load over East Africa (EA). Given this, the present study examined the trends in total, absorption, scattering, and total aerosol extinction optical depth (TAOD, AAOD, SAOD, and TAEOD) over EA, alongside trends in single scattering albedo (SSA). For this purpose, the AOD of different optical properties retrieved from multiple sensors and the Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) model between January 2001 to December 2019 were utilized to estimate trends and assess their statistical significance. The spatial patterns of seasonal mean AOD from the Moderate-resolution Imaging Spectroradiometer (MODIS) sensor and MERRA-2 model were generally characterized with high (>0.35) and low (<0.2) AOD centers over EA observed during the local dry and wet seasons, respectively. Also, the spatial trend analysis revealed a general increase in TAOD, being positive and significant over the arid and semi-arid zones of the northeastern part of EA, which is majorly dominated by locally derived dust. The local dry (wet) months generally experienced positive (negative) trends in TAOD, associated with seasonal cycles of rainfall. High and significant positive trends in AAOD were dominated over the study domain, attributed to an increased amount of biomass burning, variations in soil moisture, and changes in the rainfall pattern. The trends in TAEOD showed a distinct pattern, except over some months that depicted significant increasing trends attributed to changes in climatic conditions and anthropogenic activities. At last, the study domain exhibited decreasing trends in SSA, signifying strong absorption of direct solar radiation resulting in a warming effect. The study revealed patterns of trends in aerosol optical properties and forms the basis for further research in aerosols over EA., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Remotely sensed measurements of sulphur dioxide (SO) emitted by Turrialba Volcano (Costa Rica) are reported for the period September 2009-January 2011. These measurements were obtained using images from Advanced Spaceborne Thermal Emission and Reflexion radiometer, Ozone Monitoring Instrument and a ground-based UV camera. These three very different instruments provide flux measurements in good agreement with each other, which demonstrate that they can be integrated for monitoring SO fluxes. Fluxes from Turrialba increased fourfold in January 2010, following a phreatic explosion that formed a degassing vent in the W crater of Turrialba. Since then, the SO flux has remained high (30-50 kg/s) but seems to be showing a slowly decreasing trend. We interpret this evolution as the start of open vent degassing from a recently intruded magma body. The opening of the degassing vent decreased the confining pressure of the magma body and allowed the gases to bypass the hydrothermal system. [ABSTRACT FROM AUTHOR]

The oxides of nitrogen-NO (NO and NO)-are an important constituent of the troposphere. The availability of relatively higher spatial (0.25° grid) and temporal (daily) resolution data from ozone monitoring instrument (OMI) onboard Aura helps us to better differentiate between the point sources such as thermal power plants from large cities and rural areas compared to previous sensors. The annual and seasonal (summer and winter) distributions shows very high mean tropospheric NO in specific pockets over India especially over the Indo-Gangetic plains (up to 14.2 × 10 molecules/cm). These pockets correspond with the known locations of major thermal power plants. The tropospheric NO over India show a large seasonal variability that is also observed in the ground NO data. The multiple regression analysis show that the influence of a unit of power plant (in gigawatts) over tropospheric NO (×10 molecules/cm) is around ten times compared to a unit of population (in millions) over India. The OMI data show that the NO increases by 0.794 ± 0.12 (×10 molecules/cm; annual) per GW compared to a previous estimate of 0.014 (×10 molecules/cm) over India. The increase of tropospheric NO per gigawatt is found to be 1.088 ± 0.18, 0.898 ± 0.14, and 0.395 ± 0.13 (×10 molecules/cm) during winter, summer, and monsoon seasons, respectively. The strong seasonal variation is attributed to the enhancement or suppression of NO due to various controlling factors which is discussed here. The recent increasing trend (2005-2007) over rural thermal power plants pockets like Agori and Korba is due to recent large capacity additions in these regions. [ABSTRACT FROM AUTHOR]

Abstract: In this work we examine the possibility of using satellite remote sensors for the detection of air traffic emissions produced during the en-route segment of flight in the Upper Troposphere/Lower Stratosphere region (8000–12,000m). NO2 has been considered as the tracer of aircraft plumes with highest possibility of being successfully detected from space. An analysis of the technical potential of the current orbital sensors capable of measuring NO2 in the proximity of the tropopause has been conducted. In order to estimate an upper bound for the NO2 column related to aircraft emissions, the Canary Islands Corridor has been selected for conducting a simple emission calculation exercise based on real air traffic and operational data, assuming an ideal atmospheric scenario. The results obtained in this approximation have been compared to the actual information retrieved from space sensors. An in-depth inspection of the NO2 column data for two particular areas (Canary Islands Corridor and North Atlantic Flight Corridor) obtained in recent years by SCIAMACHY and OMI has also been carried out. The general conclusions of this viability study are not optimistic. The estimated maximum NO2 column value attributable to aircraft emissions at cruise altitudes were lower than the detection limits associated with SCIAMACHY and OMI for NO2 column measurements. As a result, detecting and quantifying the actual NO2 levels in aircraft corridors by space remote sensing is a very challenging task. [Copyright &y& Elsevier]

The 'Black Saturday' fires were a series of devastating forest fires that burned across Victoria, Australia, during February and March of 2009. In this study we have used satellite data made publically available by NASA from the Ozone Monitoring Instrument (OMI) and the Atmospheric InfraRed Sounder (AIRS) to track the smoke plume from the Black Saturday firestorm and explore the chemical aging of the smoke plume in the first days after emission. We also determined emission ratios for formaldehyde and nitrogen dioxide within smoke from fires actively burning across Victoria between 7 and 17 February 2009. The mean emission ratios with respect to carbon monoxide derived for these two tropospheric ozone precursors are (0.016 ± 0.004 mol.mol-1) for formaldehyde and (0.005 ± 0.002 mol.mol-1) for nitrogen dioxide. The mean emission ratio for formaldehyde with respect to CO is in broad agreement with values previously quoted in the literature for temperate forest fires. However, to our knowledge there are no previous measurements of emission ratios for nitrogen dioxide from Australian temperate forest fires. [ABSTRACT FROM AUTHOR]

Abstract: We evaluate the Ozone Monitoring Instrument (OMI) ozone profile retrieval against ozonesonde data and the Environmental Protection Agency (EPA) surface measurements for August 2006. Comparison of individual OMI ozone profile with ozonesonde indicates that OMI ozone profile can explain the general vertical variation of ozone but is limited in observing the boundary layer ozone, due to weak sensitivity to boundary layer ozone and thick lowest layer (∼2.5 km). We made pair-wise comparison between OMI and ozonesondes on 24 OMI vertical layers, as well as the 39 sigma-P vertical layers of the Community Multi-scale Air Quality (CMAQ) modeling system, respectively. OMI shows reasonable agreement with ozonesonde in the lower- to mid-troposphere. In the upper troposphere, while the bias increases, the normalized bias does not show much variation and remains below 10%. Comparison with EPA’s surface-monitoring data indicates that OMI observations at the lowest layer (surface to 2.5 km altitude) represent the mean values. While OMI underestimates elevated ozone concentrations, it explains the larger-scale spatial variation seen in the surface monitors. [Copyright &y& Elsevier]

Abstract: The Ozone Monitoring Instrument (OMI) on the Aura satellite obtains unique measurements for polar mesospheric cloud (PMC) analysis. Its wide cross-track viewing swath and high along-track spatial resolution makes it possible to directly evaluate PMC occurrence frequency and brightness variations between 65° and 85° latitude as a function of local time over a 12–14h continuous period. OMI PMC local time variations are closely coupled to concurrent variations in measurement scattering angle, so that ice phase function effects must be considered when interpreting the observations. Two different phase functions corresponding to bright and faint clouds are examined in this analysis. OMI observations show maximum frequency and albedo values at 8–10h local time in the Northern Hemisphere, with decreasing amplitude at higher latitudes. Southern Hemisphere values reach a minimum at 18–20h LT. Larger variations are seen in Northern Hemisphere data. No statistically significant longitudinal dependence was seen. [Copyright &y& Elsevier]

Abstract: In preparation of the Beijing Summer Olympic and Paralympics Games, strict emission control measures (ECMs) were imposed between July and September 2008 on motor vehicle traffic and industrial emissions to improve air quality. We estimated changes in the chemical sensitivity of ozone production to these ECMs using Ozone Monitoring Instrument (OMI) column measurements of formaldehyde (HCHO) and nitrogen dioxide (NO2), where their ratio serves as a proxy for the sensitivity. During the ECMs, OMI NO2 significantly decreased, subsequently increasing the HCHO/NO2. For the first half of the ECM time period, the ratios maintained values greater than two indicating that ozone production became primarily NO x -limited. In contrast, ozone production was predominantly volatile organic compound (VOC)-limited or mixed VOC-NO x -limited during the same period in the preceding three years. After the ECMs were lifted, NO2 and HCHO/NO2 returned to their previous values. The 2005–2008 OMI record shows that this transition to a predominantly NO x -limited regime during the ECMs was unique. Meteorological factors likely explain the variability in HCHO/NO2, particularly the transition to a mixed NO x -VOC-limitation in mid-August during the Olympics, where ozone production became sensitive to both NO x and VOCs until the end of the ECMs. The mixed VOC-NO x -limited regime observed during the Paralympics is also unique because previous years show that Beijing in September is predominantly VOC-limited. Beijing’s large-scale tree-planting program was expected to increase levels of biogenic VOCs, but this is not supported by OMI HCHO data. However, MODIS vegetation indices show a small increase in vegetation cover from 2003 leading up to the Games in 2008. After the Games, however, there was a downturn in the indices (2009 and 2010) to levels similar to 2006. [Copyright &y& Elsevier]

Abstract: Radiation-induced displacement damage, which has caused the increase of the dark current in the focal plane adopted in the Ozone Monitoring Instrument (OMI), was studied in regards of the primary protons and the secondaries generated by the protons in the orbit. Using the Monte Carlo N-Particle Transport Code System (MCNPX) version 2.4.0 along with the Stopping and Range of Ions in Matter version 2010 (SRIM2010), effects of the primary protons as well as secondary particles, including neutron, electron, and photon were investigated. After their doses and fluxes that reached onto the charge-coupled device (CCD) were examined, displacement damage induced by major sources was presented. [Copyright &y& Elsevier]

Abstract: Enhanced carbon monoxide (CO) in the upper troposphere (UT) is shown by nearly collocated Tropospheric Emission Spectrometer (TES) and Microwave Limb Sounder (MLS) measurements near and down-wind from the known wildfire region of SE Australia from December 12th–19th, 2006. Enhanced ultraviolet (UV) aerosol index (AI) derived from the Ozone Monitoring Instrument (OMI) measurements correlates with these high CO concentrations. The Hybrid Single Particle Langrangian Integrated Trajectory (HYSPLIT) model back trajectories trace selected air parcels, where TES observes enhanced CO in the upper and lower troposphere, to the SE Australia fire region as their initial location. Simultaneously, they show a lack of vertical advection along their tracks. TES retrieved CO vertical profiles in the higher and lower southern latitudes are examined together with the averaging kernels and show that TES CO retrievals are most sensitive at approximately 300–400hPa. The enhanced CO observed by TES in the upper (215hPa) and lower (681hPa) troposphere are, therefore, influenced by mid-tropospheric CO. GEOS-Chem model simulations with an 8-day emission inventory, as the wildfire source over Australia, are sampled to the TES/MLS observation times and locations. These simulations only show CO enhancements in the lower troposphere near and down-wind from the wildfire region of SE Australia with drastic underestimates of UT CO plumes. Although CloudSat along-track ice-water content curtains are examined to see whether possible vertical convection events can explain the high UT CO values, sparse observations of collocated Aura CO and CloudSat along-track ice-water content measurements for the single event precludes any conclusive correlation. Vertical convection that uplifts the fire-induced CO (i.e., most notably referred to as pyro-cumulonimbus (pyroCb)) may provide an explanation for the incongruence between these simulations and the TES/MLS observations of enhanced CO in the UT. [Copyright &y& Elsevier]

Omi, also known as high temperature requirement factor A2 (HtrA2), is a serine protease that was originally identified as a proapoptotic protein. Like Smac/Diablo, it antagonizes inhibitor of apoptosis proteins when released into the cytosol on apoptotic stimulation. Loss of its protease activity in mnd2 (motor neuron degeneration 2) mice is associated with neurodegeneration. However, the detailed mechanisms by which Omi regulates the pathogenesis of neurodegenerative disease remain largely unknown. We report here that Omi participates in the pivotal cellular degradation process known as autophagy. It activates autophagy through digestion of Hax-1, a Bcl-2 family-related protein that represses autophagy in a Beclin-1 (mammalian homologue of yeast ATG6)-dependent pathway. Moreover, Omi-induced autophagy facilitates the degradation of neurodegenerative proteins such as pathogenic A53T α-synuclein and truncated polyglutamine-expanded huntingtin, as well as the endogenous autophagy substrate p62. Knockdown of Omi decreases the basal level of autophagy and increases the level of the above target proteins. Furthermore, S276C Omi, the protease-defective mutant found in mnd2 mice, fails to regulate autophagy. Increased autophagy substrates and the formation of aggregate structures are observed in the brains of mnd2 mice. These results identify Omi as a novel regulator of autophagy and suggest that Omi might be important in the cellular quality control of proteins involved in neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Abstract: The Aerosol Index (AI) observations derived from the Ozone Monitoring Instrument (OMI) on board the Dutch–Finnish Aura satellite are analyzed over Greece covering the period from September 2004 to August 2008. The AI data cover the whole Greek territory (34°–42°N, 20°–28°E) with a spatial resolution of 0.25°×0.25°. The results show significant spatial and temporal variabilities of the seasonal and monthly-mean AI, with higher values at the southern parts and lower values over northern Greece. On the other hand, the AI values do not show significant differences between the western and eastern parts and, therefore, the longitude-averaged AI values can be utilized to reveal the strong south-to-north gradient. This gradient significantly changes from season to season being more intense in spring and summer, while it is minimized in winter. Another significant remark is the dominance of negative AI values over northern Greece in the summer months, indicating the presence of non-UV-absorbing aerosols, such as sulfate and sea-salt particles. The great geographical extent of the negative AI values in the summer months is indicative of long-range transport of such aerosols. In contrast, the high positive AI values over southern Greece, mainly in spring, clearly reveal the UV-absorbing nature of desert-dust particles affecting the area during Saharan dust events. The annual variation of spatial-averaged AI values shows a predominant spring maximum (0.424±0.329, in April) due to dust particles, which dominate this average and a summer minimum due to the negative AI values observed over northern Greece. In the cold period of the year (November to February) the AI values are higher over northern Greece compared to those in south, while in the rest of the year the opposite is true. [Copyright &y& Elsevier]

Abstract: Rhomboids are an ancient and conserved family of intramembrane-cleaving proteases, a small group of proteolytic enzymes capable of hydrolyzing a peptide bond within a transmembrane helix that anchors a substrate protein to the membrane. Mitochondrial rhomboids evolved in eukaryotes to coordinate a critical aspect of cell biology, the regulation of mitochondrial membranes dynamics. This function appears to have required the emergence of a structural feature that is unique among all other rhomboids: an additional transmembrane helix (TMH) positioned at the N-terminus of six TMHs that form the core proteolytic domain of all prokaryotic and eukaryotic rhomboids. This “1+6” structure, which is shared only among mitochondrial rhomboids, defines a subfamily of rhomboids with the prototypical family member being mammalian Parl. Here, we present the findings that in 11 years have elevated mitochondrial rhomboids as the gatekeepers of mitochondrial dynamics and apoptosis; further, we discuss the aspects of their biology that are bound to introduce new paradigm shifts in our understanding of how the organelle uses this unique type of protease to govern stress, signaling to the nucleus, and other key mitochondrial activities in health and disease. [ABSTRACT FROM AUTHOR]

Abstract: We investigated variations in the relative sensitivity of surface ozone formation in summer to precursor species concentrations of volatile organic compounds (VOCs) and nitrogen oxides (NOx) as inferred from the ratio of the tropospheric columns of formaldehyde to nitrogen dioxide (the “Ratio”) from the Aura Ozone Monitoring Instrument (OMI). Our modeling study suggests that ozone formation decreases with reductions in VOCs at Ratios <1 and NOx at Ratios >2; both NOx and VOC reductions may decrease ozone formation for Ratios between 1 and 2. Using this criteria, the OMI data indicate that ozone formation became: 1. more sensitive to NOx over most of the United States from 2005 to 2007 because of the substantial decrease in NOx emissions, primarily from stationary sources, and the concomitant decrease in the tropospheric column of NO2, and 2. more sensitive to NOx with increasing temperature, in part because emissions of highly reactive, biogenic isoprene increase with temperature, thus increasing the total VOC reactivity. In cities with relatively low isoprene emissions (e.g., Chicago), the data clearly indicate that ozone formation became more sensitive to NOx from 2005 to 2007. In cities with relatively high isoprene emissions (e.g., Atlanta), we found that the increase in the Ratio due to decreasing NOx emissions was not obvious as this signal was convolved with variations in the Ratio associated with the temperature dependence of isoprene emissions and, consequently, the formaldehyde concentration. [Copyright &y& Elsevier]

Abstract: Loss of Omi/HtrA2 function leads to nerve cell loss in mouse models and has been linked to neurodegeneration in Parkinson''s and Huntington''s disease. Omi/HtrA2 is a serine protease released as a pro-apoptotic factor from the mitochondrial intermembrane space into the cytosol. Under physiological conditions, Omi/HtrA2 is thought to be involved in protection against cellular stress, but the cytological and molecular mechanisms are not clear. Omi/HtrA2 deficiency caused an accumulation of reactive oxygen species and reduced mitochondrial membrane potential. In Omi/HtrA2 knockout mouse embryonic fibroblasts, as well as in Omi/HtrA2 silenced human HeLa cells and Drosophila S2R+ cells, we found elongated mitochondria by live cell imaging. Electron microscopy confirmed the mitochondrial morphology alterations and showed abnormal cristae structure. Examining the levels of proteins involved in mitochondrial fusion, we found a selective up-regulation of more soluble OPA1 protein. Complementation of knockout cells with wild-type Omi/HtrA2 but not with the protease mutant [S306A]Omi/HtrA2 reversed the mitochondrial elongation phenotype and OPA1 alterations. Finally, co-immunoprecipitation showed direct interaction of Omi/HtrA2 with endogenous OPA1. Thus, we show for the first time a direct effect of loss of Omi/HtrA2 on mitochondrial morphology and demonstrate a novel role of this mitochondrial serine protease in the modulation of OPA1. Our results underscore a critical role of impaired mitochondrial dynamics in neurodegenerative disorders. [Copyright &y& Elsevier]

Abstract: The impact of Hurricanes Katrina and Rita in 2005 on pollution emissions in the Gulf of Mexico region was investigated using tropospheric column amounts of nitrogen dioxide (NO2) from the Ozone Monitoring Instrument (OMI) on the NASA Aura satellite. Around New Orleans and coastal Mississippi, we estimate that Katrina caused a 35% reduction in NOx emissions on average in the three weeks after landfall. Hurricane Rita caused a significant reduction (20%) in NOx emissions associated with power generation and intensive oil refining activities near the Texas/Louisiana border. We also found a 43% decrease by these two storms over the eastern Gulf of Mexico Outer Continental Shelf mainly due to the evacuation of and damage to platforms, rigs, and ports associated with oil and natural gas production. [Copyright &y& Elsevier]

Abstract: A theoretical sensitivity study of the influence of cirrus cloud properties on tropospheric NO2 columns retrieved from the spaceborne Ozone Monitoring Instrument (OMI) measurements is performed. It is conducted within the framework of the synergetic use of A-Train sensors to derive more representative trace gas products. We aim to study the potential effects of cirrus clouds on tropospheric NO2 retrievals using a retrieval algorithm that, unlike the OMI Standard and DOMINO algorithms, does not correct for the effects of clouds. The sensitivity study is based on the radiative transfer code SCIATRAN that performs both simulations of top of atmosphere (TOA) reflectances as measured by an OMI-like band and tropospheric NO2 column retrievals based on the differential optical absorption spectroscopy (DOAS) method. The results of the sensitivity study show that if a correction for cirrus clouds is not included in our simple retrieval that does not account for clouds in the first place, the tropospheric column can be underestimated by 55%. This underestimation depends strongly on cirrus parameters as, in order of importance, cloud fraction, cloud optical depth, asymmetry factor of cirrus cloud phase function and cloud top height. The perspective of the synergy between OMI and cloud information obtained from cloud-derived products of the A-Train is evaluated in two parts by applying a simple cloud correction scheme based on the independent pixel approximation (IPA). Firstly, we evaluated the tropospheric NO2 column retrievals error caused by uncertainties in cirrus cloud properties. Secondly we studied the influence of subpixel cloud optical depth variability on NO2 retrievals. From our simulations, it is demonstrated that the error will be reduced significantly if the cloud fraction is lower or equal to 0.5. In this case, the cloud fraction and the cloud optical depth must be known within accuracy less than 0.05% and 50%, respectively. The cloud top height and the asymmetry factor must be known within uncertainty of at least 1km and less than 0.05, respectively. The latter result shows that the uncertainty of the asymmetry factor is a major source of error in the cloud correction for tropospheric NO2 retrieval in the presence of cirrus. [Copyright &y& Elsevier]