scholarly journals Tropospheric ozone climatology at two Southern Hemisphere tropical/subtropical sites, (Reunion Island and Irene, South Africa) from ozonesondes, LIDAR, and in situ aircraft measurements

2009 ◽  
Vol 9 (5) ◽  
pp. 1723-1734 ◽  
Author(s):  
G. Clain ◽  
J. L. Baray ◽  
R. Delmas ◽  
R. Diab ◽  
J. Leclair de Bellevue ◽  
...  
Keyword(s):  
South Africa ◽  
Tropospheric Ozone ◽  
Lower Layer ◽  
Austral Summer ◽  
Data Sets ◽  
Positive Trend ◽  
Reunion Island ◽  
Upper Troposphere ◽  
Réunion Island ◽  
Sky Conditions

Abstract. This paper presents a climatology and trends of tropospheric ozone in the Southwestern Indian Ocean (Reunion Island) and South Africa (Irene and Johannesburg). This study is based on a multi-instrumental dataset: PTU-O3 ozonesondes, DIAL LIDAR and MOZAIC airborne instrumentation. The seasonal profiles of tropospheric ozone at Reunion Island have been calculated from two different data sets: ozonesondes and LIDAR. The two climatological profiles are similar, except in austral summer when the LIDAR profiles show greater values in the free troposphere, and in the upper troposphere when the LIDAR profiles show lower values during all seasons. These results show that the climatological value of LIDAR profiles must be discussed with care since LIDAR measurements can be performed only under clear sky conditions, and the upper limit of the profile depends on the signal strength. In addition, linear trends have been calculated from ozonesonde data at Reunion and Irene. Considering the whole tropospheric column, the trend is slightly positive for Reunion, and more clearly positive for Irene. Trend calculations have also been made separating the troposphere into three layers, and separating the dataset into seasons. Results show that the positive trend for Irene is governed by the lower layer that is affected by industrial pollution and biomass burning. On the contrary, for Reunion Island, the strongest trends are observed in the upper troposphere, and in winter when stratosphere-troposphere exchange is more frequently expected.

scholarly journals Tropospheric ozone climatology at two southern subtropical sites, (Reunion Island and Irene, South Africa) from ozone sondes, LIDAR, aircraft and in situ measurements

2008 ◽  
Vol 8 (3) ◽  
pp. 11063-11101
Author(s):  
G. Clain ◽  
J. L. Baray ◽  
R. Delmas ◽  
R. Diab ◽  
J. Leclair de Bellevue ◽  
...  
Keyword(s):  
South Africa ◽  
Tropospheric Ozone ◽  
Seasonal Cycle ◽  
Lower Troposphere ◽  
Ground Level ◽  
Positive Trend ◽  
Reunion Island ◽  
Free Troposphere ◽  
Upper Troposphere ◽  
Réunion Island

Abstract. This paper presents a climatology and trends of tropospheric ozone in the southwestern part of Indian Ocean (Reunion Island) and South Africa (Irene and Johannesburg). This study is based on a multi-instrumental dataset: PTU-O3 radiosoundings, DIAL LIDAR, MOZAIC airborne instrumentation and Dasibi UV ground based measurements. The seasonal profiles of tropospheric ozone at Reunion Island have been calculated from two different data sets: radiosondes and LIDAR. The two climatological profiles are similar, except in austral summer when smaller values for the LIDAR profiles in the free troposphere, and in the upper troposphere for all seasons occur. These results show that the LIDAR profiles are at times not representative of the true ozone climatological value as measurements can be taken only under clear sky conditions, and the upper limit reached depends on the signal. In the lower troposphere, climatological ozone values from radiosondes have been compared to a one year campaign of ground based measurements from a Dasibi instrument located at high altitude site (2150 m) at Reunion Island. The seasonal cycle is comparable for the two datasets, with Dasibi UV values displaying slightly higher values. This suggests that if local dynamical and possibly physico-chemical effects may influence the ozone level, the seasonal cycle can be followed with ground level measurements. Average ground level concentrations measured on the summits of the island seem to be representative of the lower free troposphere ozone concentration at the same altitude (~2000 m) whereas night time data would be representative of tropospheric concentration at a higher altitude (~3000 m) due to the subsidence effect. Finally, linear trends have been calculated from radiosondes data at Reunion and Irene. Considering the whole tropospheric column, the trend is slightly positive for Reunion, and more clearly positive for Irene. Trend calculations have also been made separating the troposphere into three layers, and separating the dataset into seasons. Results shows that the positive trend for Irene is governed by the lower layer most probably by industrial pollution and biomass burning. On the contrary, for Reunion Island, the strongest trends are observed in the upper troposphere, and in winter when stratospheric-tropospheric exchange is more frequently expected.

scholarly journals Tropospheric ozone profiles by DIAL at Maïdo Observatory (Reunion Island): system description, instrumental performance and result comparison with ozone external data set

2017 ◽  
Vol 10 (9) ◽  
pp. 3359-3373 ◽  
Author(s):  
Valentin Duflot ◽  
Jean-Luc Baray ◽  
Guillaume Payen ◽  
Nicolas Marquestaut ◽  
Francoise Posny ◽  
...  
Keyword(s):  
Current System ◽  
Atmospheric Composition ◽  
Integration Time ◽  
Data Sets ◽  
Buffer Gas ◽  
Reunion Island ◽  
Data Set ◽  
Upper Troposphere ◽  
Réunion Island ◽  
Good Agreement

Abstract. In order to recognize the importance of ozone (O3) in the troposphere and lower stratosphere in the tropics, a DIAL (differential absorption lidar) tropospheric O3 lidar system (LIO3TUR) was developed and installed at the Université de la Réunion campus site (close to the sea) on Reunion Island (southern tropics) in 1998. From 1998 to 2010, it acquired 427 O3 profiles from the low to the upper troposphere and has been central to several studies. In 2012, the system was moved up to the new Maïdo Observatory facility (2160 m a.m.s.l. – metres above mean sea level) where it started operation in February 2013. The current system (LIO3T) configuration generates a 266 nm beam obtained with the fourth harmonic of a Nd:YAG laser sent into a Raman cell filled up with deuterium (using helium as buffer gas), generating the 289 and 316 nm beams to enable the use of the DIAL method for O3 profile measurements. The optimal range for the actual system is 6–19 km a.m.s.l., depending on the instrumental and atmospheric conditions. For a 1 h integration time, vertical resolution varies from 0.7 km at 6 km a.m.s.l. to 1.3 km at 19 km a.m.s.l., and mean uncertainty within the 6–19 km range is between 6 and 13 %. Comparisons with eight electrochemical concentration cell (ECC) sondes simultaneously launched from the Maïdo Observatory show good agreement between data sets with a 6.8 % mean absolute relative difference (D) between 6 and 17 km a.m.s.l. (LIO3T lower than ECC). Comparisons with 37 ECC sondes launched from the nearby Gillot site during the daytime in a ±24 h window around lidar shooting result in a 9.4 % D between 6 and 19 km a.m.s.l. (LIO3T lower than ECC). Comparisons with 11 ground-based Network for Detection of Atmospheric Composition Change (NDACC) Fourier transform infrared (FTIR) spectrometer measurements acquired during the daytime in a ±24 h window around lidar shooting show good agreement between data sets with a D of 11.8 % for the 8.5–16 km partial column (LIO3T higher than FTIR), and comparisons with 39 simultaneous Infrared Atmospheric Sounding Interferometer (IASI) observations over Reunion Island show good agreement between data sets with a D of 11.3 % for the 6–16 km partial column (LIO3T higher than IASI). ECC, LIO3TUR and LIO3T O3 monthly climatologies all exhibit the same range of values and patterns. In particular, the Southern Hemisphere biomass burning seasonal enhancement and the ozonopause altitude decrease in late austral winter–spring, as well as the sign of deep convection bringing boundary layer O3-poor air masses up to the middle–upper troposphere in late austral summer, are clearly visible in all data sets.

scholarly journals Ozone profiles by DIAL at Maïdo Observatory (Reunion Island) Part 1. Tropospheric ozone lidar: system description, performances evaluation and comparison with ancillary data

2017 ◽  
Author(s):  
Valentin Duflot ◽  
Jean-Luc Baray ◽  
Guillaume Payen ◽  
Nicolas Marquestaut ◽  
Françoise Posny ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Current System ◽  
Integration Time ◽  
Buffer Gas ◽  
Reunion Island ◽  
Lidar System ◽  
Ancillary Data ◽  
Upper Troposphere ◽  
Réunion Island ◽  
Good Agreement

Abstract. Recognizing the importance of ozone in the troposphere and lower stratosphere in the tropics, a DIAL tropospheric ozone lidar system (LIO3TUR) was developped and installed at the Université de la Réunion campus site (close to the sea) in Reunion Island (southern tropics) in 1998. From 1998 to 2010, it acquired 427 ozone profiles from the low to the upper troposphere and has been central to several studies. In 2012, the system was moved up to the new Maïdo Observatory facility (2160 m above mean sea level – amsl) where it started operation in February 2013. The current system (LIO3T) configuration generates a 266 nm beam obtained with the fourth harmonic of a Nd:YAG laser sent into a Raman cell filled up with deuterium (using helium as buffer gas) generating the 289 and 316 nm beams enabling the use of the DIAL method for ozone profile measurements. Optimal range for the actual system is 6–19 km amsl, depending on the instrumental and atmospheric conditions; for a 1-hour integration time, vertical resolution varies from 0.7 km at 6 km amsl to 1.3 km at 19 km amsl, and mean uncertainty within the 6–19 km range is between 6 and 13 %. Comparisons with 8 electrochemical concentration cell (ECC) sondes simultaneously launched from the Maïdo Observatory show a good agreement between datasets with a 7.7 % mean absolute value of the relative differences with respect to the mean (D) between 6 and 17 km amsl (LIO3T low); comparisons with 37 ECC sondes launched from the nearby Gillot site during day time in a ±24-hour window around lidar shooting result in a 10.3 % D between 6 and 19 km amsl (LIO3T low); comparisons with 11 ground-based Network for Detection of Atmosphere Composition Change (NDACC) Fourier Transform Infrared (FTIR) spectrometer measurements acquired during day time in a ±24-hour window around lidar shooting show a good agreement between datasets with a D of 11.8 % for the 8.5–16 km partial column (LIO3T high); and comparisons with 39 simultaneous Infrared Atmospheric Sounding Interferometer (IASI) observations over Reunion Island show a good agreement between datasets with a D of 11.3 % for the 6–16 km partial column (LIO3T high). ECC, LIO3TUR and LIO3T O3 monthly climatologies all exhibit the same range of values and patterns. In particular, the southern hemisphere biomass burning seasonal enhancement, the ozonopause altitude decrease in late austral winter-spring, as well as the signature of deep convection bringing boundary layer-ozone poor air masses up to the mid-upper troposphere in late austral summer, are clearly visible on all datasets.

scholarly journals Using beryllium-7 to assess cross-tropopause transport in global models

2016 ◽  
Vol 16 (7) ◽  
pp. 4641-4659 ◽  
Author(s):  
Hongyu Liu ◽  
David B. Considine ◽  
Larry W. Horowitz ◽  
James H. Crawford ◽  
Jose M. Rodriguez ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Transport Model ◽  
Meteorological Data ◽  
Data Sets ◽  
High Latitudes ◽  
Chemical Transport Model ◽  
Modeling Framework ◽  
Global Models ◽  
Deposition Fluxes ◽  
Upper Troposphere

Abstract. We use the Global Modeling Initiative (GMI) modeling framework to assess the utility of cosmogenic beryllium-7 (7Be), a natural aerosol tracer, for evaluating cross-tropopause transport in global models. The GMI chemical transport model (CTM) was used to simulate atmospheric 7Be distributions using four different meteorological data sets (GEOS1-STRAT DAS, GISS II′ GCM, fvGCM, and GEOS4-DAS), featuring significantly different stratosphere–troposphere exchange (STE) characteristics. The simulations were compared with the upper troposphere and/or lower stratosphere (UT/LS) 7Be climatology constructed from  ∼  25 years of aircraft and balloon data, as well as climatological records of surface concentrations and deposition fluxes. Comparison of the fraction of surface air of stratospheric origin estimated from the 7Be simulations with observationally derived estimates indicates excessive cross-tropopause transport at mid-latitudes in simulations using GEOS1-STRAT and at high latitudes using GISS II′ meteorological data. These simulations also overestimate 7Be deposition fluxes at mid-latitudes (GEOS1-STRAT) and at high latitudes (GISS II′), respectively. We show that excessive cross-tropopause transport of 7Be corresponds to overestimated stratospheric contribution to tropospheric ozone. Our perspectives on STE in these meteorological fields based on 7Be simulations are consistent with previous modeling studies of tropospheric ozone using the same meteorological fields. We conclude that the observational constraints for 7Be and observed 7Be total deposition fluxes can be used routinely as a first-order assessment of cross-tropopause transport in global models.

scholarly journals Investigation of the short-time variability of tropical tropospheric ozone

2003 ◽  
Vol 21 (10) ◽  
pp. 2095-2106 ◽  
Author(s):  
T. Randriambelo ◽  
J.-L. Baray ◽  
S. Baldy ◽  
A. M. Thompson ◽  
S. Oltmans ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Tropospheric Ozone ◽  
Transition Period ◽  
Meteorological Data ◽  
Tropical Meteorology ◽  
Atmospheric Composition ◽  
Time Variability ◽  
Reunion Island ◽  
Ozone Profile ◽  
Réunion Island

Abstract. Since 1998, a ground-based tropospheric ozone lidar has been running at Reunion Island and has been involved with a daily measurement campaign that was performed in the latter part of the biomass burning season, during November–December 1999. The averaged ozone profile obtained during November–December 1999 agrees well with the averaged ozone profile obtained from the ozonesondes launch at Reunion during November–December (1992– 2001). Comparing weekly sonde launches (part of the Southern Hemisphere Additional Ozonesondes: SHADOZ program) with the daily ground-based lidar observations shows that some striking features of the day-to-day variability profiles are not observed in the sonde measurements. Ozone profiles respond to the nature of disturbances which vary from one day to the next. The vertical ozone distribution at Reunion is examined as a function of prevailing atmospheric circulation. Back trajectories show that most of the enhanced ozone crossed over biomass burning and convectively active regions in Madagascar and the southern African continent. The analyses of the meteorological data show that ozone stratification profiles are in agreement with the movement of the synoptic situations in November–December 1999. Three different sequences of transport are explained using wind fields. The first sequence from 23 to 25 November is characterized by northerly transport; during the second sequence from 26 to 30 November, the air masses are influenced by meridional transport. The third sequence from 2 to 6 December is characterized by westerly transport associated with the sub-tropical jet stream. The large, standard deviations of lidar profiles in the middle and upper troposphere are in agreement with the upper wind variabilities which evidence passing ridge and trough disturbances. During the transition period between the dry season and the wet season, multiple ozone sources including stratosphere-troposphere exchanges, convection and biomass burning contribute to tropospheric ozone at Reunion Island through sporadic events characterized by a large spatial and temporal variability.Key words. Atmospheric composition and structure (troposphere-composition and chemistry) – Meteorology and atmospheric dynamics (climatology; tropical meteorology)

scholarly journals Exploration for olive fruit fly parasitoids across Africa reveals regional distributions and dominance of closely associated parasitoids

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xingeng Wang ◽  
Vaughn M. Walton ◽  
Kim A. Hoelmer ◽  
Charles H. Pickett ◽  
Arnaud Blanchet ◽  
...  
Keyword(s):  
South Africa ◽  
Canary Islands ◽  
Interspecific Interactions ◽  
Fruit Fly ◽  
Sub Saharan Africa ◽  
Olive Fruit Fly ◽  
Reunion Island ◽  
Olive Fruit ◽  
Réunion Island ◽  
Sub Saharan

AbstractThe olive fruit fly, Bactrocera oleae, has been a key pest of olives in Europe and North America. We conducted the largest exploration for parasitoids associated with the fly across Sub-Saharan Africa (Kenya, Namibia, and South Africa) including some of the fly’s adjoining regions (Canary Islands, Morocco, Réunion Island and Tunisia). From Sub-Saharan regions, four braconids were collected: Bracon celer, Psytallia humilis, P. lounsburyi, and Utetes africanus. Results showed that their regional dominance was related to climate niches, with P. humilis dominant in hot semi-arid areas of Namibia, P. lounsburyi dominant in more tropical areas of Kenya, and U. africanus prevalent in Mediterranean climates of South Africa. Psytallia concolor was found in the Canary Islands, Morocco and Tunisian, and the Afrotropical braconid Diachasmimorpha sp. near fullawayi on Réunion Island. Furthermore, we monitored the seasonal dynamics of the fly and parasitoids in Cape Province of South Africa. Results showed that fruit maturity, seasonal variations in climates and interspecific interactions shape the local parasitoid diversity that contribute to the low fly populations. The results are discussed with regard to ecological adaptations of closely associated parasitoids, and how their adaptations impact biocontrol.

scholarly journals Ground-based FTIR and MAX-DOAS observations of formaldehyde at Réunion Island and comparisons with satellite and model data

2009 ◽  
Vol 9 (4) ◽  
pp. 15891-15957 ◽  
Author(s):  
C. Vigouroux ◽  
F. Hendrick ◽  
T. Stavrakou ◽  
B. Dils ◽  
I. De Smedt ◽  
...  
Keyword(s):  
Large Scale ◽  
Dispersion Model ◽  
Sensitivity Study ◽  
Particle Dispersion ◽  
Data Sets ◽  
Reunion Island ◽  
Source Regions ◽  
Réunion Island ◽  
Transport Patterns ◽  
Good Agreement

Abstract. Formaldehyde (HCHO) columns have been retrieved from ground-based Fourier transform infrared (FTIR) campaign measurements in 2004 and 2007 and from UV-Visible MAX-DOAS measurements in 2004–2005 at the NDACC site of Réunion Island (21° S, 55° E). The FTIR and MAX-DOAS daily mean formaldehyde total columns are intercompared in their common measurement period, from August to October 2004. The ground-based data are also compared to correlative SCIAMACHY data. The comparisons account for the vertical sensitivity differences of the data sets, by including their respective averaging kernels. Complete error budgets are also presented. The FTIR and MAX-DOAS daily mean total columns agree very well: no significant bias is observed and the standard deviation of the comparisons is only 8%. Both FTIR and MAX-DOAS HCHO total columns are in good agreement with SCIAMACHY values in the 2004–2005 period, with standard deviations of 21% and 31%, respectively. The same seasonal cycle is observed by the different instruments, with a minimum in austral winter and a maximum in February–March. The FTIR and MAX-DOAS data are confronted with HCHO columns calculated by a global CTM, the IMAGES model. The model underestimates the HCHO columns by 23–29% in comparison with FTIR, and by 15% in comparison with DOAS. This bias might have multiple causes, including an underestimation of OH concentrations in the model (as indicated by a sensitivity study using prescribed OH fields) and/or an underestimated contribution of large-scale transport of HCHO precursors from Madagascar. The latter hypothesis is comforted by the large observed day-to-day variability of HCHO columns, and by the observation that the peak values of FTIR columns can often be associated with free tropospheric transport patterns from source regions over Madagascar to Réunion Island, according to simulations performed with the Lagrangian particle dispersion model FLEXPART.

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