scholarly journals Nitrogen oxides in the boundary layer and free troposphere at the Mt. Bachelor Observatory

2010 ◽  
Vol 10 (2) ◽  
pp. 5751-5801 ◽  
Author(s):  
D. R. Reidmiller ◽  
D. A. Jaffe ◽  
E. V. Fischer ◽  
B. Finley
Keyword(s):  
Boundary Layer ◽  
North America ◽  
Gulf Of Alaska ◽  
Aleutian Islands ◽  
Transport Pathways ◽  
North American Continent ◽  
Mixing Ratios ◽  
The North ◽  
Synoptic Conditions ◽  
The Difference

Abstract. Nitrogen oxide (NOx = NO + NO2) observations were made at the Mt. Bachelor Observatory in central Oregon, USA (MBO; 2.73 km above sea level) during one autumn and three springtime (15 April–20 May) periods. This is the first study to discuss interannual variability in NOx for this region. NOx concentrations (mean ±1σ) for spring 2007, 2008 and 2009 were 119±65, 117±65, and 91±54 pptv, respectively. The difference in mean mixing ratios between 2007 and 2008 is not statistically significant, whereas the difference between these years and 2009 is significant (p<0.01). We attribute the decline in NOx from 2007–2008 to 2009 to changes in free tropospheric synoptic conditions over the Northeast Pacific and trans-Pacific transport pathways during spring 2009. In 2009, there were: (1) higher geopotential heights over the Gulf of Alaska, (2) warmer temperatures over the Aleutian Islands/Gulf of Alaska and (3) much weaker winds throughout the North Pacific. During the autumn 2008 campaign, NOx concentrations (mean ±1σ) were 175±548 pptv. The highly non-normal distribution of data (skewness coefficient of 19.1 vs. 2.5, 2.8 and 2.4 in spring 2007, 2008 and 2009, respectively) resulted from periods of very high NOx levels. Using MODIS Rapid Response (Aqua and Terra) results, we show that during autumn our site can be heavily influenced by wildfires in western North America. This is in contrast to springtime, when the smaller positive (i.e., right) tail of the NOx distribution is driven largely by Asian long-range transport (ALRT) events. We developed a novel means of segregating boundary layer (BL)-influenced vs. free tropospheric (FT) air. During spring 2008 we collected "chairlift soundings" of temperature, relative humidity and pressure in an effort to better understand the diurnal pattern of a BL influence at our summit station. Results from this experiment revealed that, on average, a BL influence begins around 10:00 PDT (UTC – 7 h) in spring. Using this information to isolate FT air, we characterize probable pollution sources and synoptic conditions for the top 20 FT NOx events over three spring campaigns. Half (n = 10) of these 20 events were determined to be "Imported" events characterized by anomalously: (1) high geopotential heights off the west coast of North America, (2) warm temperatures stretching from the Aleutian Islands to Baja California, and (3) strong southwesterly winds in the Asian outflow region. Five events exhibited an influence from the North American continent. These events are characterized by very strong cyclonic behavior off the northwestern USA coast.

scholarly journals Nitrogen oxides in the boundary layer and free troposphere at the Mt. Bachelor Observatory

2010 ◽  
Vol 10 (13) ◽  
pp. 6043-6062 ◽  
Author(s):  
D. R. Reidmiller ◽  
D. A. Jaffe ◽  
E. V. Fischer ◽  
B. Finley
Keyword(s):  
Boundary Layer ◽  
North America ◽  
Gulf Of Alaska ◽  
Aleutian Islands ◽  
Transport Pathways ◽  
North American Continent ◽  
Mixing Ratios ◽  
The North ◽  
Synoptic Conditions ◽  
The Difference

Abstract. Nitrogen oxide (NOx=NO+NO2) observations were made at the Mt. Bachelor Observatory in central Oregon, USA (MBO; 2.73 km above sea level) during one autumn and three springtime (15 April–20 May) periods. This is the first study to discuss interannual variability in NOx for this region. NOx concentrations (mean±1σ) for spring 2007, 2008 and 2009 were 119±65, 117±65, and 91±54 pptv, respectively. The difference in mean mixing ratios between 2007 and 2008 is not statistically significant, whereas the difference between these years and 2009 is significant (p<0.01). We attribute the decline in NOx from 2007–2008 to 2009 to changes in free tropospheric synoptic conditions over the Northeast Pacific and trans-Pacific transport pathways during spring 2009. In 2009, there were: (1) higher geopotential heights over the Gulf of Alaska, (2) warmer temperatures over the Aleutian Islands/Gulf of Alaska and (3) much weaker winds throughout the North Pacific. During the autumn 2008 campaign, NOx concentrations (mean±1σ) were 175±548 pptv. The highly non-normal distribution of data (skewness coefficient of 19.1 vs. 2.5, 2.8 and 2.4 in spring 2007, 2008 and 2009, respectively) resulted from periods of very high NOx levels. Using MODIS Rapid Response (Aqua and Terra) results, we show that during autumn our site can be heavily influenced by wildfires in western North America. This is in contrast to springtime, when the smaller positive (i.e., right) tail of the NOx distribution is driven largely by Asian long-range transport (ALRT) events. We developed a novel means of segregating boundary layer (BL)-influenced vs. free tropospheric (FT) air. During spring 2008 we collected "chairlift soundings" of temperature, relative humidity and pressure in an effort to better understand the diurnal pattern of a BL influence at our summit station. Results from this experiment revealed that, on average, a BL influence begins around 10:00 PDT (UTC – 07:00 h) in spring. Using this information to isolate FT air, we characterize probable pollution sources and synoptic conditions for the top 20 FT NOx events over three spring campaigns. Half (n=10) of these 20 events were determined to be "Imported" events characterized by anomalously: (1) high geopotential heights off the west coast of North America, (2) warm temperatures stretching from the Aleutian Islands to Baja California, and (3) strong southwesterly winds in the Asian outflow region. Five events exhibited an influence from the North American continent. These events are characterized by very strong cyclonic behavior off the northwestern USA coast.

scholarly journals Increasing ozone in marine boundary layer inflow at the west coasts of North America and Europe

2009 ◽  
Vol 9 (4) ◽  
pp. 1303-1323 ◽  
Author(s):  
D. D. Parrish ◽  
D. B. Millet ◽  
A. H. Goldstein
Keyword(s):  
Boundary Layer ◽  
North America ◽  
North American ◽  
West Coast ◽  
American West ◽  
Marine Boundary Layer ◽  
North American West ◽  
Mixing Ratios ◽  
The North ◽  
Marine Air

Abstract. An effective method is presented for determining the ozone (O3) mixing ratio in the onshore flow of marine air at the North American west coast. By combining the data available from all marine boundary layer (MBL) sites with simultaneous wind data, decadal temporal trends of MBL O3 in all seasons are established with high precision. The average springtime temporal trend over the past two decades is 0.46 ppbv/yr with a 95% confidence limit of 0.13 ppbv/yr, and statistically significant trends are found for all seasons except autumn, which does have a significantly smaller trend than other seasons. The average trend in mean annual ozone is 0.34±0.09 ppbv/yr. These decadal trends at the North American west coast present a striking comparison and contrast with the trends reported for the European west coast at Mace Head, Ireland. The trends in the winter, spring and summer seasons compare well at the two locations, while the Mace Head trend is significantly greater in autumn. Even though the trends are similar, the absolute O3 mixing ratios differ markedly, with the marine air arriving at Europe in all seasons containing 7±2 ppbv higher ozone than marine air arriving at North America. Further, the ozone mixing ratios at the North American west coast show no indication of stabilizing as has been reported for Mace Head. In a larger historical context the background boundary layer O3 mixing ratios over the 130 years covered by available data have increased substantially (by a factor of two to three), and this increase continues at present, at least in the MBL of the Pacific coast region of North America. The reproduction of the increasing trends in MBL O3 over the past two decades, as well as the difference in the O3 mixing ratios between the two coastal regions will present a significant challenge for global chemical transport models. Further, the ability of the models to at least semi-quantitatively reproduce the longer-term, historical trends may an even greater challenge.

scholarly journals Rapid convective outflow from the U.S. to the upper troposphere over the North Atlantic during the NASA INTEX-NA airborne campaign: flight 13 case study

2007 ◽  
Vol 7 (6) ◽  
pp. 17367-17400
Author(s):  
S. Y. Kim ◽  
R. Talbot ◽  
H. Mao ◽  
D. Blake ◽  
S. Vay ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
The United States ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The North ◽  
Synoptic Conditions ◽  
The North Atlantic ◽  
The U.S

Abstract. A case study of convective outflow from the United States (U.S.) was examined using airborne measurements from NASA DC-8 flight 13 during the Intercontinental Chemical Transport Experiment – North America (INTEX-NA). Mixing ratios of methane (CH4) and carbon monoxide (CO) at 8–11 km altitude over the North Atlantic were elevated to 1843 ppbv and 134 ppbv respectively, while those of carbon dioxide (CO2) and carbonyl sulfide (COS) were reduced to 372.4 ppmv and 411 pptv respectively. In this region, urban and industrial influence was evidenced by elevated mixing ratios and good linear relationships between urban and industrial tracers compared to North Atlantic background air. Moreover, low mixing ratios and a good correlation between COS and CO2 showed a fingerprint of terrestrial uptake and minimal dilution during rapid transport over a 1–2 day time period. Analysis of synoptic conditions, backward trajectories, and photochemical aging estimates based on C3H8/C2H6 strongly suggested that elevated anthropogenic tracers in the upper troposphere of the flight region were the result of fast transport via convective uplifting of boundary layer air over the southeastern U.S. This mechanism is supported by the similar slopes values of linear correlations between long-lived (months) anthropogenic tracers (e.g., C2Cl4 and CHCl3) from the flight region and the planetary boundary layer in the southeastern U.S. In addition, the aircraft measurements suggest that outflow from the U.S. augmented the entire tropospheric column at mid-latitudes over the North Atlantic. Overall, the flight 13 data demonstrate a pervasive impact of U.S. anthropogenic emissions on the troposphere over the North Atlantic.

scholarly journals Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source

2005 ◽  
Vol 5 (11) ◽  
pp. 2927-2934 ◽  
Author(s):  
L. J. Carpenter ◽  
D. J. Wevill ◽  
S. O'Doherty ◽  
G. Spain ◽  
P. G. Simmonds
Keyword(s):  
Boundary Layer ◽  
Wind Direction ◽  
Marine Boundary Layer ◽  
Land Breeze ◽  
Peat Bogs ◽  
Mixing Ratios ◽  
The North ◽  
Prevailing Wind Direction ◽  
Atmospheric Observations ◽  
Summer Minimum

Abstract. In situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001- Dec 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March - mid October) and 1.8+0.8 pptv (December-February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms-1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ΔCHCl3/ΔCHBr3 varied strongly according to the prevailing wind direction; from 0.60+0.15 in south-easterly (100-170° and northerly (340-20°) air to 2.5+0.4 in north-easterly (40-70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however had an immediate fetch inland, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the north-easterly land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 20.4(0.4-948) Gg yr-1, which is approximately 7% of the total global source.

scholarly journals Imperialismo en el siglo XXI

2016 ◽  
Vol 6 (10) ◽  
pp. 49-74
Author(s):  
John Smith ◽  
Keyword(s):  
North America ◽  
Low Income ◽  
Great Part ◽  
Low Income Countries ◽  
Capitalist Development ◽  
Neoliberal Globalization ◽  
The North ◽  
Foreign Labor ◽  
Economic Foundation ◽  
The Difference

The globalization of production and its spread to low-income countries is the most notable transformation of the neoliberal era. Its driving force is the efforts by companies in Europe, North America and Japan to cut costs and raise profits, replacing relatively well-paid domestic labor for cheaper foreign labor. The gap in global wages, in great part the result of the suppression of the free movement of labor, provides a distorted view of the global differences in the rate of exploitation (simply, the difference between the value generated by the workers and what they are paid) upon which profits, prosperity and social peace in Europe, North America and Japan are ever-more reliant. Thus, neoliberal globalization should be seen as a new imperialist stage in capitalist development, where «imperialism» is defined by its economic foundation: the exploitation of labor in the South by capitalists from the North.

AN EVALUATION OF THE GRAVITY CONTROL NETWORK IN NORTH AMERICA

Geophysics ◽  
1961 ◽  
Vol 26 (1) ◽  
pp. 57-76 ◽  
Author(s):  
J. C. Behrendt ◽  
G. P. Woollard
Keyword(s):  
North America ◽  
Geodetic Survey ◽  
Control Network ◽  
Mean Values ◽  
The North ◽  
University Of Wisconsin ◽  
Systematic Correction ◽  
Free Air ◽  
Wide Range ◽  
The Difference

Observations with a LaCoste and Romberg geodetic gravimeter having a very low nearly linear drift rate, a high reading precision, and a world wide range were made at approximately three hundred sites in order to check and extend the gravity control network in North America. The sites occupied were mostly at former gravimeter bases located at airports, harbors, universities, and pendulum stations. The instrument was calibrated against the North American standardization range of pendulum measurements from Paso de Cortes, Mexico, to Fairbanks, Alaska, using the weighted mean values of the observations established with the U. S. Coast and Geodetic Survey, Cambridge University (England), and Gulf‐University of Wisconsin pendulum equipment. A statistical evaluation of the precision of the network based on the reoccupations at 40 major control stations gives an estimated standard deviation of 0.08 mgal. The airport network of bases previously reported by Woollard (1958) that was established with high range Worden gravity meters was found to require a systematic correction of 0.3 mgal per 1,000 mgal change because of the difference in calibration standard used. The adjusted values for the forty airport stations reoccupied agree on the average to 0.2 mgal with the results of this study. The reoccupations of the old pendulum observation sites of the U. S. Coast and Goedetic Survey suggest that much of this network is in error by over 3 mgals. Descriptions of sites occupied and the principal facts for position, elevation, observed gravity, and free‐air and Bouguer anomalies are presented.

scholarly journals Continental outflow from the US to the upper troposphere over the North Atlantic during the NASA INTEX-NA Airborne Campaign

2008 ◽  
Vol 8 (7) ◽  
pp. 1989-2005 ◽  
Author(s):  
S. Y. Kim ◽  
R. Talbot ◽  
H. Mao ◽  
D. Blake ◽  
S. Vay ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Atlantic ◽  
The United States ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The North ◽  
Southeastern Us ◽  
The Us ◽  
The North Atlantic ◽  
Continental Outflow

Abstract. A case of continental outflow from the United States (US) was examined using airborne measurements from NASA DC-8 flight 13 during the Intercontinental Chemical Transport Experiment – North America (INTEX-NA). Mixing ratios of methane (CH4) and carbon monoxide (CO) at 8–11 km altitude over the North Atlantic were elevated to 1843 ppbv and 134 ppbv respectively, while those of carbon dioxide (CO2) and carbonyl sulfide (COS) were reduced to 372.4 ppmv and 411 pptv respectively. In this region, urban and industrial influences were evidenced by elevated mixing ratios and good linear relationships between urban and industrial tracers compared to North Atlantic background air. Moreover, low mixing ratios and a good correlation between COS and CO2 showed a fingerprint of terrestrial uptake and minimal dilution during rapid transport over a 1–2 day time period. Analysis of synoptic conditions, backward trajectories, and photochemical aging estimates based on C3H8/C2H6 strongly suggested that elevated anthropogenic tracers in the upper troposphere of the flight region were the result of transport via convection and warm conveyor belt (WCB) uplifting of boundary layer air over the southeastern US. This mechanism is supported by the similar slope values of linear correlations between long-lived (months) anthropogenic tracers (e.g., C2Cl4 and CHCl3) from the flight region and the planetary boundary layer in the southeastern US. In addition, the aircraft measurements suggest that outflow from the US augmented the entire tropospheric column at mid-latitudes over the North Atlantic. Overall, the flight 13 data demonstrate a pervasive impact of US anthropogenic emissions on the troposphere over the North Atlantic.

The species of Thecaphora on Compositae in North America

1982 ◽  
Vol 60 (8) ◽  
pp. 1512-1522 ◽  
Author(s):  
Rubén Durán
Keyword(s):  
New Species ◽  
North America ◽  
North American ◽  
Morphological Characteristics ◽  
American Continent ◽  
Bright Field ◽  
New Host ◽  
North American Continent ◽  
The North ◽  
Scanning Electron

Five new species of Thecaphora collected in Mexico are described, some of which are parasitic on genera of Compositae not previously reported as hosts. Species of Thecaphora on Compositae for the North American continent now total 11. New species include Thecaphora denticulata, T. heliopsidis, T. hennenea, T. melampodii, and T. neo-mexicana. New host genera for North America include Bidens, Heliopsis, and Melampodium. Morphological characteristics of Thecaphora species and taxonomic criteria to delimit them are discussed. Keys to the species, interpretations of spore ball morphology and spore sculpturing, and scanning electron and bright-field micrographs are presented.

scholarly journals In situ observations of CH<sub>2</sub>Cl<sub>2</sub> and CHCl<sub>3</sub> show efficient transport pathways for very short-lived species into the lower stratosphere via the Asian and North American summer monsoons

2021 ◽  
Author(s):  
Valentin Lauther ◽  
Bärbel Vogel ◽  
Johannes Wintel ◽  
Andrea Rau ◽  
Peter Hoor ◽  
...  
Keyword(s):  
North American ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Late Summer ◽  
Anthropogenic Sources ◽  
North American Monsoon ◽  
Transport Pathway ◽  
Transport Pathways ◽  
Mixing Ratios ◽  
The North

Abstract. Efficient transport pathways for ozone depleting very short-lived substances (VSLS) from their source regions into the stratosphere are a matter of current scientific debate, however they have yet to be fully identified on an observational basis. Understanding the increasing impact of chlorine containing VSLS (Cl-VSLS) on stratospheric ozone depletion is important in order to validate and improve model simulations and future predictions. We report on the first transport study using airborne in situ measurements of the Cl-VSLS dichloromethane (CH2Cl2) and trichloromethane (chloroform, CHCl3) to derive a detailed description of the two most efficient and fast transport pathways from (sub-)tropical source regions into the extratropical lower stratosphere (Ex-LS) in northern hemisphere (NH) late summer. The Cl-VSLS measurements were obtained in the upper troposphere and lower stratosphere (UTLS) above Western Europe and the mid latitude Atlantic Ocean in the frame of the WISE (Wave-driven ISentropic Exchange) aircraft campaign in autumn 2017 and are combined with the results from a three-dimensional simulation of a Lagrangian transport model as well as back-trajectory calculations. Compared to background measurements of similar age we find up to 150 % enhanced CH2Cl2 and up to 100 % enhanced CHCl3 mixing ratios in the Ex-LS. We link the measurements of enhanced mixing ratios to emissions in the region of southern and eastern Asia. Transport from this area to the Ex-LS at potential temperatures in the range of 370–400 K takes about 5–10 weeks via the Asian summer monsoon anticyclone (ASMA). Our measurements suggest anthropogenic sources to be the cause of these strongly elevated Cl-VSLS concentrations observed at the top of the lowermost stratosphere (LMS). A faster transport pathway into the Ex-LS is derived from particularly low CH2Cl2 and CHCl3 mixing ratios in the UTLS. These low mixing ratios reflect weak emission sources and a local seasonal minimum of both species in the boundary layer of Central America and the tropical Atlantic. We show that air masses uplifted by hurricanes, the North American monsoon, and general convection above Central America into the tropical tropopause layer to potential temperatures of about 360–370 K are transported isentropically within 1–5 weeks into the Ex-LS. This transport pathway linked to the North American monsoon mainly impacts the middle and lower part of the LMS with particularly low CH2Cl2 and CHCl3 mixing ratios. In a case study, we specifically analyze air samples directly linked to the uplift by the category 5 hurricane Maria that occurred during October 2017 above the Atlantic Ocean. Regionally differing CHCl3 : CH2Cl2 emission ratios derived from our UTLS measurements suggest a clear similarity between CHCl3 and CH2Cl2 when emitted by anthropogenic sources and differences between the two species mainly caused by additional, likely biogenic, CHCl3 sources. Overall, the transport of strongly enhanced CH2Cl2 and CHCl3 mixing ratios from southern and eastern Asia via the ASMA is the main factor for increasing the chlorine loading from the analyzed VSLS in the Ex-LS during NH late summer. Thus, further increases in Asian CH2Cl2 and CHCl3 emissions, as frequently reported in recent years, will further increase the impact of Cl-VSLS on stratospheric ozone depletion.

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