scholarly journals Effect of Lockdown on Pollutant Levels in the Delhi Megacity: Role of Local Emission Sources and Chemical Lifetimes

2021 ◽  
Vol 9 ◽  
Author(s):  
Chinmay Mallik ◽  
Harish Gadhavi ◽  
Shyam Lal ◽  
Rahul Kant Yadav ◽  
R. Boopathy ◽  
...  
Keyword(s):  
Seasonal Changes ◽  
Trace Gases ◽  
Emission Sources ◽  
Air Masses ◽  
The World ◽  
Local Emission ◽  
Maximum Decrease ◽  
Emission Changes

The COVID-19 pandemic resulted in changed emission regimes all over the world. India also imposed complete lockdown on all modes of travel and industrial activities for about 2 months from 25-March-2020 and later unlocked these activities in a phased manner. Here, we study signatures of emissions changes on levels of atmospheric trace gases and aerosols contributing to air pollution over multiple sites in India’s capital Delhi covering various lockdown and unlock phases using satellite data and in-situ observations. The resulting changes in the levels of these species were compared with respect to their average of 2015–2019 to attribute for year to year and seasonal changes. A clear impact of lockdown was observed for AOD, PM, NO2, CO, and SO2 as a result of emission changes, while changed precursor levels led to a change in O3 chemical regimes impacting its concentrations. A detailed analysis of FLEXPART trajectories revealed increased PM levels over Delhi in north-westerly air masses sourced to Punjab region all the way up to Pakistan. Changes in aerosols and NO2 were not only restricted to the surface but transcended the total tropospheric column. The maximum decrease in PM, NO2, CO, and SO2 was observed during the month of total lockdown in April. The lockdown impact varied with species e.g., PM10 and PM2.5 as well as locations even within the periphery of Delhi. While surface level aerosols and NO2 showed significant and almost similar changes, AOD showed much lower decrease than tropospheric column NO2.

scholarly journals Secondary Organic Aerosol Production from Local Emissions Dominates the Organic Aerosol Budget over Seoul, South Korea, during KORUS-AQ

2018 ◽  
Author(s):  
Benjamin A. Nault ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
Jason C. Schroder ◽  
Bruce Anderson ◽  
...  
Keyword(s):  
South Korea ◽  
Flow Reactor ◽  
Organic Aerosol ◽  
The West ◽  
Air Masses ◽  
Regional Sources ◽  
Peroxy Nitrates ◽  
The World ◽  
First Time

Abstract. Organic aerosol (OA) is an important fraction of submicron aerosols. However, it is challenging to predict and attribute the specific organic compounds and sources that lead to observed OA loadings, largely due to contributions from secondary production. This is especially true for megacities surrounded by numerous regional sources that create an OA background. Here, we utilize in-situ gas and aerosol observations collected on-board the NASA DC-8 during the NASA/NIER KORUS-AQ (KORea United States-Air Quality) campaign to investigate the sources and hydrocarbon precursors that led to the secondary OA (SOA) production observed over Seoul. First, we investigate the contribution of transported OA to total loadings observed over Seoul, by using observations over the West Sea coupled to FLEXPART Lagrangian simulations. During KORUS-AQ, the average OA loading advected into Seoul was ~ 1–3 µg sm−3. Second, taking this background into account, the dilution-corrected SOA concentration observed over Seoul was ~ 140 µg sm−3 ppmv−1 at 0.5 equivalent photochemical days. This value is at the high end of what has been observed in other megacities around the world (20–70 µg sm−3 ppmv−1 at 0.5 equivalent days). For the average OA concentration observed over Seoul (13 µg sm−3), it is clear that production of SOA from locally emitted precursors is the major source in the region. The importance of local SOA production was supported by the following observations: (1) FLEXPART source contribution calculations indicate any hydrocarbons with a lifetime less than 1 day, which are shown to dominate the observed SOA production, mainly originate from South Korea. (2) SOA correlated strongly with other secondary photochemical species, including short-lived species (formaldehyde, peroxy acetyl nitrate, sum of acyl peroxy nitrates, dihydroxy toluene, and nitrate aerosol). (3) Results from an airborne oxidation flow reactor (OFR), flown for the first time, show a factor of 4.5 increase in potential SOA concentrations over Seoul versus over the West Sea, a region where background air masses that are advected into Seoul can be measured. (4) Box model simulations reproduce SOA observed over Seoul within 15 % on average, and suggest that short-lived hydrocarbons (i.e., xylenes, trimethylbenzenes, semi- and intermediate volatility compounds) were the main SOA precursors over Seoul. Toluene, alone, contributes 9 % of the modeled SOA over Seoul. Finally, along with these results, we use the metric ΔOA/ΔCO2 to examine the amount of OA produced per fuel consumed in a megacity, which shows less variability across the world than ΔOA/ΔCO.

scholarly journals Quantifying transport into the Arctic lowermost stratosphere

2010 ◽  
Vol 10 (23) ◽  
pp. 11623-11639 ◽  
Author(s):  
A. Werner ◽  
C. M. Volk ◽  
E. V. Ivanova ◽  
T. Wetter ◽  
C. Schiller ◽  
...  
Keyword(s):  
High Latitude ◽  
Trace Gases ◽  
Polar Vortex ◽  
The Arctic ◽  
Late Winter ◽  
Mass Balance Calculation ◽  
Air Masses ◽  
History Of ◽  
Simple Mass

Abstract. In the Arctic winter 2003, in-situ measurements of the long-lived trace gases N2O, CFC-11 (CCl3F), H-1211 (CBrClF2), CH4, O3 and H2O have been performed on board the high-altitude aircraft M55 Geophysica. The data are presented and used to study transport into the lowermost stratosphere (LMS). The LMS can be regarded as a mixture of fractions of air originating in (i) the troposphere, (ii) the extra-vortex stratosphere above 400 K and (iii) the Arctic vortex above 400 K. These fractions are determined using a simple mass balance calculation. The analysis exhibits a strong tropospheric influence of 50% ± 15% or more in the lowest 20 K of the high-latitude LMS. Above this region the LMS is dominated by air masses having descended from above 400 K. Below the Arctic vortex region at potential temperatures above 360 K, air in the LMS is a mixture of extra-vortex stratospheric and vortex air masses. The vortex fraction increases from about 40% ± 15% at 360 K to 100% at 400 K for equivalent latitudes >70° N. This influence of air masses descending through the bottom of the polar vortex increases over the course of the winter. By the end of winter a significant fraction of 30% ± 10% vortex air in the LMS is found even at an equivalent latitude of 40° N. Since the chemical and dynamical history of vortex air is distinct from that of mid-latitude stratospheric air masses, this study implies that the composition of the mid- to high-latitude LMS during late winter and spring is significantly influenced by the Arctic vortex.

scholarly journals Upper tropospheric CH<sub>4</sub> and CO affected by the South Asian summer monsoon during OMO

2018 ◽  
Author(s):  
Laura Tomsche ◽  
Andrea Pozzer ◽  
Narendra Ojha ◽  
Uwe Parchatka ◽  
Jos Lelieveld ◽  
...  
Keyword(s):  
South Asian ◽  
Asian Summer Monsoon ◽  
Trace Gases ◽  
South Asian Summer Monsoon ◽  
The South ◽  
Transport Pathways ◽  
Air Masses ◽  
Upper Troposphere ◽  
Asian Summer

Abstract. The Asian monsoon anticyclone (AMA) is a yearly recurring phenomenon in the northern hemispheric upper troposphere and lower stratosphere. It is connected to the South Asian summer monsoon, and the circulation extends approximately across 20°–120° E and 15°–40° N longitude-latitude. It has a clearly observable signature due to vertical transport of polluted air masses from the surface to the upper troposphere by the monsoon convection. However, the transport pathways and the fate of pollutants in the upper troposphere are not yet fully understood. As pollution emissions in South Asia are increasing, changes in the chemical composition of the AMA can be expected. We performed in situ measurements of carbon monoxide (CO) and methane (CH4) in the region of monsoon outflow and in background air in the upper troposphere (Mediterranean, Arabian Peninsula, Arabian Sea) by optical absorption spectroscopy on board the German High Altitude and Long range (HALO) research aircraft during the OMO (Oxidation Mechanism Observations) mission in summer 2015. We identified the transport pathways and the origin of the trace gases with back trajectories, calculated with the Lagrangian particle dispersion model FLEXPART, and we compared the in situ data with simulations of the atmospheric chemistry general circulation model EMAC. CH4 and CO mixing ratios were found to be enhanced within the AMA, on average by 72.1 ppb and 20.1 ppb, respectively, originating in the South Asian region (Indio-Gangetic Plain, North East India, Bangladesh and Bay of Bengal). It appears that CH4 is an ideal monsoon tracer in the upper troposphere due to its extended lifetime and the strong South Asian emissions. Furthermore, we used the measurements and model results to study the dynamics of the AMA, with an emphasis on the southern and western areas within the upper troposphere. For example, we distinguished four AMA modes based on different meteorological conditions. During one occasion we observed that under the influence of dwindling flow the transport barrier between the anticyclone and its surroundings weakened, expelling air masses from the AMA. The trace gases exhibited a distinct fingerprint of the AMA, and we also found that CH4 accumulated over the course of the OMO campaign.

scholarly journals Quantifying transport into the Arctic lowermost stratosphere

2009 ◽  
Vol 9 (1) ◽  
pp. 1407-1446 ◽  
Author(s):  
A. Werner ◽  
C. M. Volk ◽  
E. V. Ivanova ◽  
T. Wetter ◽  
C. Schiller ◽  
...  
Keyword(s):  
High Latitude ◽  
Trace Gases ◽  
Polar Vortex ◽  
The Arctic ◽  
Late Winter ◽  
Mass Balance Calculation ◽  
Air Masses ◽  
History Of ◽  
Simple Mass

Abstract. In-situ measurements of the long-lived trace gases N2O, CFC-11 (CCl3F), H-1211 (CBrClF2), CH4, O3 and H2O performed in the Arctic winter 2003 on board the high-altitude aircraft M55 Geophysica are presented and used to study transport into the lowermost stratosphere (LMS). Fractions of air in the LMS originating in i) the troposphere, ii) the extra-vortex stratosphere above 400 K and iii) the Arctic vortex above 400 K are determined using a simple mass balance calculation. The analysis exhibits a strong tropospheric influence of 50% or more in the lowest 20 K of the high-latitude LMS. Above this region the LMS is dominated by air masses having descended from above 400 K. Below the Arctic vortex region at potential temperatures above 360 K, air in the LMS is a mixture of extra-vortex stratospheric and vortex air masses. The vortex fraction increases from about 40% at 360 K to 100% at 400 K for equivalent latitudes >70° N. This influence of air masses descending through the bottom of the polar vortex increases over the course of the winter. By the end of winter a significant fraction of 30% vortex air in the LMS is found even at an equivalent latitude of 40° N. Since the chemical and dynamical history of vortex air is distinct from that of mid-latitude stratospheric air masses, this study implies that the composition of the mid- to high-latitude LMS during late winter and spring is significantly influenced by the Arctic vortex.

scholarly journals Pipes to Earth's subsurface: The role of atmospheric conditions in controlling air transport through boreholes and shafts

2018 ◽  
Author(s):  
Elad Levintal ◽  
Nadav G. Lensky ◽  
Amit Mushkin ◽  
Noam Weisbrod
Keyword(s):  
Large Diameter ◽  
Absolute Humidity ◽  
Barometric Pressure ◽  
Atmospheric Temperature ◽  
Air Transport ◽  
Atmospheric Conditions ◽  
Air Masses ◽  
Diurnal Cycles

Abstract. Understanding air exchange dynamics between underground cavities (e.g., caves, mines, boreholes, etc.) and the atmosphere is significant for the exploration of gas transport across the Earth-atmosphere interface. Here, we investigated the role of atmospheric conditions in air transport inside boreholes through in-situ observations. Three geometries were explored: (1) a narrow and deep shaft (0.1 m and 27 m, respectively), ending in a large underground cavity; (2) the same shaft after the pipe was lowered and separated from the cavity; and (3) a deep large-diameter borehole (3.4 m and 59 m, respectively). Absolute humidity was found to be a reliable proxy for distinguishing between atmospheric and cavity air masses and thus to explore air transport through the three geometries. Airflow directions in the first two narrow-diameter geometries were found to be driven by changes in barometric pressure whereas airflow in the large-diameter geometry was correlated primarily to the diurnal cycles of ambient atmospheric temperature. High CO2 concentrations (~ 2000 ppm) were found in all three geometries, which can indicate that the airflow to the atmosphere is also significant to the investigation of greenhouse gas emissions.

scholarly journals Transport of Antarctic stratospheric strongly dehydrated air into the troposphere observed during the HALO-ESMVal campaign 2012

2015 ◽  
Vol 15 (6) ◽  
pp. 7895-7932 ◽  
Author(s):  
C. Rolf ◽  
A. Afchine ◽  
H. Bozem ◽  
B. Buchholz ◽  
V. Ebert ◽  
...  
Keyword(s):  
Water Vapor ◽  
Exchange Process ◽  
Satellite Measurements ◽  
Transport Barrier ◽  
Transport Pathways ◽  
Near Surface ◽  
Air Masses ◽  
The Antarctic

Abstract. Dehydration in the Antarctic winter stratosphere is a well-known phenomenon that is occasionally observed by balloon-borne and satellite measurements. However, in-situ measurements of dehydration in the Antarctic vortex are very rare. Here, we present detailed observations with the in-situ and GLORIA remote sensing instrument payload aboard the new German aircraft HALO. Strongly dehydrated air masses down to 1.6 ppmv of water vapor were observed as far north as 47° S and between 12 and 13 km in altitude, which has never been observed by satellites. The dehydration can be traced back to individual ice formation events, where ice crystals sedimented out and water vapor was irreversibly removed. Within these dehydrated stratospheric air masses, filaments of moister air reaching down to the tropopause are detected with the high resolution limb sounder, GLORIA. Furthermore, dehydrated air masses are observed with GLORIA in the Antarctic troposphere down to 7 km. With the help of a backward trajectory analysis, a tropospheric origin of the moist filaments in the vortex can be identified, while the dry air masses in the troposphere have stratospheric origins. The transport pathways of Antarctic stratosphere/troposphere exchange are investigated and the irrelevant role of the Antarctic thermal tropopause as a transport barrier is confirmed. Further, it is shown that the exchange process can be attributed to several successive Rossby wave events in combination with an isentropic interchange of air masses across the weak tropopause and subsequent subsidence due to radiative cooling. Once transported to the troposphere, air masses with stratospheric origin are able to reach near-surface levels within 1–2 months.

scholarly journals Vertical profile of peroxyacetyl nitrate (PAN) from MIPAS-STR measurements over Brazil in February 2005 and the role of PAN in the UT tropical NO<sub>y</sub> partitioning

2008 ◽  
Vol 8 (2) ◽  
pp. 6983-7016
Author(s):  
C. Keim ◽  
G. Y. Liu ◽  
C. E. Blom ◽  
H. Fischer ◽  
T. Gulde ◽  
...  
Keyword(s):  
Vertical Profile ◽  
Trace Gases ◽  
Remote Sensor ◽  
Research Aircraft ◽  
Careful Handling ◽  
Tropical Troposphere ◽  
Selection Of ◽  
Made In

Abstract. We report on the retrieval of PAN (CH3C(O)OONO2) in the upper tropical troposphere from limb measurements by the remote-sensor MIPAS-STR on board the Russian high altitude research aircraft M55-Geophysica. The measurements were performed close to Araçatuba, Brazil, on 17 February 2005. The retrieval was made in the spectral range 775–820 cm−1 where PAN exhibits its strongest feature but also more than 10 species interfere. Especially trace gases such as CH3CCl3, CFC-113, CFC-11, and CFC-22, emitting also in spectrally broad not-resolved branches, make the processing of PAN prone to errors. Therefore, the selection of appropriate spectral windows, the separate retrieval of several interfering species and the careful handling of the water vapour profile are part of the study presented. The retrieved profile of PAN has a maximum of about 0.14 ppbv at 10 km altitude, slightly larger than the lowest reported values (<0.1 ppbv) and much lower than the highest (0.65 ppbv). Besides the NOy constituents measured by MIPAS-STR (HNO3, ClONO2, PAN), the situ instruments aboard the Geophysica provide simultaneous measurements of NO, NO2, and the sum NOy. Comparing the sum of in-situ and remotely derived NO+NO2+HNO3+ClONO2+PAN with total NOy a deficit of 30–40% (0.2–0.3 ppbv) in the troposphere remains unexplained whereas the values fit well in the stratosphere.

An example of a peat flow near Prince Rupert, British Columbia

1985 ◽  
Vol 22 (2) ◽  
pp. 246-249 ◽  
Author(s):  
O. Hungr ◽  
S. G. Evans
Keyword(s):  
British Columbia ◽  
Moisture Content ◽  
Key Words ◽  
East Coast ◽  
High Potential ◽  
The World ◽  
Undrained Loading ◽  
Potential Mobility

Peat flows, bog flows, or bog bursts consist of a rapid downhill movement of masses of saturated peat. Although this process has been documented from peatlands in other parts of the world, the slope movement described here is the first to be reported from Canadian peatlands. The peat flow took place on the east coast of Kaien Island, near Prince Rupert, British Columbia, and was initiated by a slump in a peat spoil pile. It involved the sudden mobilization of a strip of in situ peat 210 m long and approximately 20 m wide. The peat was fibrous, rich in roots, and had a moisture content of approximately 240%. The flow demonstrates the high potential mobility of natural peat covers and the role of undrained loading in effecting movement of slopes as low as 5°. Key words: peat, flow slide, peat flow, northeast British Columbia.

Deep convective influence on the UTLS composition in the Asian Monsoon Anticyclone region: 2017 StratoClim campaign results

2020 ◽  
Author(s):  
Silvia Bucci ◽  
Bernard Legras ◽  
Pasquale Sellitto ◽  
Francesco D'Amato ◽  
Silvia Viciani ◽  
...  
Keyword(s):  
Asian Monsoon ◽  
Deep Convection ◽  
Direct Injection ◽  
Trace Gases ◽  
Convective Cloud ◽  
Air Masses ◽  
The North ◽  
Transport Condition ◽  
Trajectory System

&lt;p&gt;The StratoClim stratospheric aircraft campaign, taking place in summer over the Nepalese region, provided a wide dataset of observations of air composition inside the Asian Monsoon Anticyclone (AMA). To improve the understanding of the role of penetrating overshoot in the AMA region, we exploit the TRACZILLA Lagrangian simulations, computed on meteorological fields from ECMWF (ERA-Interim and ERA5) at 3h and 1h resolution and using both kinematic and diabatic vertical velocity approaches. The synergy with high-resolution observations of convective cloud top from the MSG1 and Himawari geostationary satellites is used to individuate the convective sources.&lt;/p&gt;&lt;p&gt;To evaluate the capability of the trajectory system to reproduce the transport in the UTLS we compare the simulations with the observed trace gases concentration. The ERA5 simulations appear to provide a higher consistency with observed data than ERA-Interim and show a better agreement between the diabatic and kinematic results. The best performance is given by the ERA5 with diabatic transport and, adopting this setting, we analyze the transport condition during the 8 flights of the campaign.&lt;/p&gt;&lt;p&gt;The aircraft sampled different convective plumes, often carrying pollutant compounds up to the UTLS level. The highest observed concentration of trace gases had been linked to fresh convective air (younger than a few days) coming from China, Pakistan and the North Indian region.&lt;/p&gt;&lt;p&gt;A vertical stratification is observed in the age of air: up to 15 km, the age of air is less than 3 days and these fresh air masses make up nearly the entire totality of the air composition. Above, a transition layer is identified between 15 km and 17 km (close to the tropopause), where the convective influence is still dominant and the ages range from one week to two. Finally, above this layer, the convective influence rapidly decreases toward zero and the mean air age increase to 20 days and more.&lt;/p&gt;&lt;p&gt;This study quantifies the contribution of direct injection of deep convection on the UTLS composition based on the aircraft measurements. Preliminary results of the upscale analysis based on the trajectories-satellites system will also be presented.&lt;/p&gt;

scholarly journals On Turbulence and Mixing in the Free Atmosphere Inferred from High-Resolution Soundings

2008 ◽  
Vol 25 (6) ◽  
pp. 833-852 ◽  
Author(s):  
Carol Anne Clayson ◽  
Lakshmi Kantha
Keyword(s):  
High Resolution ◽  
Trace Gases ◽  
Free Atmosphere ◽  
Turbulent Dissipation ◽  
The Past ◽  
Direct Measurements ◽  
The World ◽  
Radar Measurements ◽  
Turbulence Scaling

Abstract Mixing in the free atmosphere above the planetary boundary layer is of great importance to the fate of trace gases and pollutants. However, direct measurements of the turbulent dissipation rate by in situ probes are very scarce and radar measurements are fraught with uncertainties. In this paper, turbulence scaling concepts, developed over the past decades for application to oceanic mixing, are used to suggest an alternative technique for retrieving turbulence properties in the free atmosphere from high-resolution soundings. This technique enables high-resolution radiosondes, which have become quite standard in the past few years, to be used not only to monitor turbulence in the free atmosphere in near–real time, but also to study its spatiotemporal characteristics from the abundant archives of high-resolution soundings from around the world. Examples from several locations are shown, as well as comparisons with radar-based estimations and a typical Richardson number–based parameterization.

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