scholarly journals Impact of convection on the upper-tropospheric composition (water vapor and ozone) over a subtropical site (Réunion island; 21.1° S, 55.5° E) in the Indian Ocean

2020 ◽  
Vol 20 (14) ◽  
pp. 8611-8626 ◽  
Author(s):  
Damien Héron ◽  
Stéphanie Evan ◽  
Jérôme Brioude ◽  
Karen Rosenlof ◽  
Françoise Posny ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Local Maximum ◽  
Reunion Island ◽  
Mixing Ratio ◽  
Southwest Indian Ocean ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Réunion Island ◽  
The Impact

Abstract. Observations of ozonesonde measurements of the NDACC/SHADOZ (Network for the Detection of Atmospheric Composition Change and the Southern Hemisphere ADditional OZonesondes) program and humidity profiles from the daily Météo-France radiosondes at Réunion island (21.1∘ S, 55.5∘ E) from November 2013 to April 2016 were analyzed to identify the origin of wet upper-tropospheric air masses with low ozone mixing ratio observed above the island, located in the southwest Indian Ocean (SWIO). A seasonal variability in hydration events in the upper troposphere was found and linked to the convective activity within the SWIO basin. In the upper troposphere, ozone mixing ratios were lower (mean of 57 ppbv) in humid air masses (RH > 50 %) compared to the background mean ozone mixing ratio (73.8 ppbv). A convective signature was identified in the ozone profile dataset by studying the probability of occurrence of different ozone thresholds. It was found that ozone mixing ratios lower than 45 to 50 ppbv had a local maximum of occurrence between 10 and 13 km in altitude, indicative of the mean level of convective outflow. Combining FLEXPART Lagrangian back trajectories with METEOSAT-7 infrared brightness temperature products, we established the origin of convective influence on the upper troposphere above Réunion island. It has been found that the upper troposphere above Réunion island is impacted by convective outflows in austral summer. Most of the time, deep convection is not observed in the direct vicinity of the island, but it is observed more than 1000 km away from the island, in the tropics, either from tropical storms or the Intertropical Convection Zone (ITCZ). In November and December, the air masses above Réunion island originate, on average, from central Africa and the Mozambique Channel. During January and February the source region is the northeast of Mozambique and Madagascar. Those results improve our understanding of the impact of the ITCZ and tropical cyclones on the hydration of the upper troposphere in the subtropics in the SWIO.

scholarly journals Impact of convection on the upper-tropospheric composition (water vapor/ozone) over a subtropical site (Réunion Island, 21.1° S–55.5° E) in the Indian Ocean

2020 ◽  
Author(s):  
Damien Héron ◽  
Stephanie Evan ◽  
Jerome Brioude ◽  
Karen Rosenlof ◽  
Françoise Posny ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Local Maximum ◽  
Reunion Island ◽  
Mixing Ratio ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
South West Indian Ocean ◽  
Réunion Island ◽  
The Impact

Abstract. Observations of ozonesonde measurements of the NDACC/SHADOZ program and humidity profiles from the daily Météeo-France radiosondes at Réunion Island (21.1° S, 55.5° E) from November 2013 to April 2016 are analyzed to identify the origin of wet upper tropospheric air masses with low ozone mixing ratio observed above the island, located in the South West Indian Ocean (SWIO). A seasonal variability in hydration events in the upper troposphere was found and linked to the convective activity within the SWIO basin. In the upper troposphere, ozone mixing ratios were lower (mean of 57 ppbv) in humid air masses (RH > 50 %) compared to the background mean ozone mixing ratio (73.8 ppbv). A convective signature was identified in the ozone profile dataset by studying the probability of occurrence of different ozone thresholds. It was found that ozone mixing ratios lower than 45 to 50 ppbv had a local maximum of occurrence between 10 and 13 km in altitude, indicative of the mean level of convective outflow. Combining FLEXPART Lagrangian backtrajectories with METEOSAT 7 infrared brightness temperature products, we established the origin of convective influence on the upper troposphere above Réunion island. It has been found that the upper troposphere above Réunion island is impacted by convective outflows in austral summer. Most of the time, deep convection is not observed in the direct vicinity of the island, but more than a thousand of kilometers away from the island, in the tropics, either from tropical storms or the Inter Tropical Convective Zone. In November and December, the air masses above Réunion Island originate, on average, from Central Africa and the Mozambique channel. During January, February the source region is the North-east of Mozambique and Madagascar. Those results improve our understanding of the impact of the ITCZ and tropical cyclones hydration of the upper troposphere in the subtropics in the SWIO.

scholarly journals Carbapenemase-producing Enterobacteriaceae circulating in the Reunion Island, a French territory in the Southwest Indian Ocean

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Guillaume Miltgen ◽  
Pascal Cholley ◽  
Daniel Martak ◽  
Michelle Thouverez ◽  
Paul Seraphin ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Reunion Island ◽  
Southwest Indian Ocean ◽  
Réunion Island

Effects of industrial outfalls on tropical macrobenthic sediment communities in Reunion Island (Southwest Indian Ocean)

2006 ◽  
Vol 52 (8) ◽  
pp. 865-880 ◽  
Author(s):  
Lionel Bigot ◽  
Chantal Conand ◽  
Jean Michel Amouroux ◽  
Patrick Frouin ◽  
Henrich Bruggemann ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Reunion Island ◽  
Southwest Indian Ocean ◽  
Réunion Island

scholarly journals Reactive nitrogen, ozone and ozone production in the Arctic troposphere and the impact of stratosphere-troposphere exchange

2011 ◽  
Vol 11 (24) ◽  
pp. 13181-13199 ◽  
Author(s):  
Q. Liang ◽  
J. M. Rodriguez ◽  
A. R. Douglass ◽  
J. H. Crawford ◽  
J. R. Olson ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Stratospheric Ozone ◽  
Arctic Region ◽  
Ozone Production ◽  
The Arctic ◽  
Subsequent Formation ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Impact

Abstract. We use aircraft observations obtained during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission to examine the distributions and source attributions of O3 and NOy in the Arctic and sub-Arctic region. Using a number of marker tracers, we distinguish various air masses from the background troposphere and examine their contributions to NOx, O3, and O3 production in the Arctic troposphere. The background Arctic troposphere has a mean O3 of ~60 ppbv and NOx of ~25 pptv throughout spring and summer with CO decreasing from ~145 ppbv in spring to ~100 ppbv in summer. These observed mixing ratios are not notably different from the values measured during the 1988 ABLE-3A and the 2002 TOPSE field campaigns despite the significant changes in emissions and stratospheric ozone layer in the past two decades that influence Arctic tropospheric composition. Air masses associated with stratosphere-troposphere exchange are present throughout the mid and upper troposphere during spring and summer. These air masses, with mean O3 concentrations of 140–160 ppbv, are significant direct sources of O3 in the Arctic troposphere. In addition, air of stratospheric origin displays net O3 formation in the Arctic due to its sustainable, high NOx (75 pptv in spring and 110 pptv in summer) and NOy (~800 pptv in spring and ~1100 pptv in summer). The air masses influenced by the stratosphere sampled during ARCTAS-B also show conversion of HNO3 to PAN. This active production of PAN is the result of increased degradation of ethane in the stratosphere-troposphere mixed air mass to form CH3CHO, followed by subsequent formation of PAN under high NOx conditions. These findings imply that an adequate representation of stratospheric NOy input, in addition to stratospheric O3 influx, is essential to accurately simulate tropospheric Arctic O3, NOx and PAN in chemistry transport models. Plumes influenced by recent anthropogenic and biomass burning emissions observed during ARCTAS show highly elevated levels of hydrocarbons and NOy (mostly in the form of NOx and PAN), but do not contain O3 higher than that in the Arctic tropospheric background except some aged biomass burning plumes sampled during spring. Convection and/or lightning influences are negligible sources of O3 in the Arctic troposphere but can have significant impacts in the upper troposphere in the continental sub-Arctic during summer.

scholarly journals Reactive nitrogen, ozone and ozone production in the Arctic troposphere and the impact of stratosphere-troposphere exchange

2011 ◽  
Vol 11 (4) ◽  
pp. 10721-10767 ◽  
Author(s):  
Q. Liang ◽  
J. M. Rodriguez ◽  
A. R. Douglass ◽  
J. H. Crawford ◽  
E. Apel ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Arctic Region ◽  
Tropospheric Chemistry ◽  
Ozone Production ◽  
The Arctic ◽  
Source Attribution ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
The Impact

Abstract. We analyze the aircraft observations obtained during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellite (ARCTAS) mission together with the GEOS-5 CO simulation to examine O3 and NOy in the Arctic and sub-Arctic region and their source attribution. Using a number of marker tracers and their probability density distributions, we distinguish various air masses from the background troposphere and examine their contribution to NOx, O3, and O3 production in the Arctic troposphere. The background Arctic troposphere has mean O3 of ~60 ppbv and NOx of ~25 pptv throughout spring and summer with CO decreases from ~145 ppbv in spring to ~100 ppbv in summer. These observed CO, NOx and O3 mixing ratios are not notably different from the values measured during the 1988 ABLE-3A and the 2002 TOPSE field campaigns despite the significant changes in the past two decades in processes that could have changed the Arctic tropospheric composition. Air masses associated with stratosphere-troposphere exchange are present throughout the mid and upper troposphere during spring and summer. These air masses with mean O3 concentration of 140–160 ppbv are the most important direct sources of O3 in the Arctic troposphere. In addition, air of stratospheric origin is the only notable driver of net O3 formation in the Arctic due to its sustainable high NOx (75 pptv in spring and 110 pptv in summer) and NOy (~800 pptv in spring and ~1100 pptv in summer) levels. The ARCTAS measurements present observational evidence suggesting significant conversion of nitrogen from HNO3 to NOx and then to PAN (a net formation of ~120 pptv PAN) in summer when air of stratospheric origin is mixed with tropospheric background during stratosphere-to-troposphere transport. These findings imply that an adequate representation of stratospheric O3 and NOy input are essential in accurately simulating O3 and NOx photochemistry as well as the atmospheric budget of PAN in tropospheric chemistry transport models of the Arctic. Anthropogenic and biomass burning pollution plumes observed during ARCTAS show highly elevated hydrocarbons and NOy (mostly in the form of NOx and PAN), but do not contribute significantly to O3 in the Arctic troposphere except in some of the aged biomass burning plumes sampled during spring. Convection and/or lightning influences are negligible sources of O3 in the Arctic troposphere but can have significant impacts in the upper troposphere in the continental sub-Arctic during summer.

Pareto Optimization for Rossby Wave Pattern Impacts on MH370 Debris

2020 ◽  
pp. 251-280
Keyword(s):  
Indian Ocean ◽  
Rossby Waves ◽  
Wave Pattern ◽  
Pareto Optimization ◽  
Southern Indian Ocean ◽  
Reunion Island ◽  
Réunion Island ◽  
Ocean Gyres ◽  
Western Side ◽  
The Impact

This chapter censoriously appraises the comprehensive theories that specify that more concepts are needed to bridge the gap found between the dynamic of the Southern Indian Ocean and the actual MH370 vanishing mechanism. Thus, this chapter is devoted to the Rossby waves, which could attribute to the fact that the MH370 flaperon got to Réunion Island. In this view, Rossby waves generate growth of energy in the west of the ocean gyres and create the strengthening currents on the western side of the ocean basins. Pareto optimization algorithm of the impact power of Rossby waves proves that the flaperon could not drift across the Southern Indian Ocean and be positioned on Réunion Island.

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