scholarly journals Ground-based solar absorption FTIR Spectroscopy at the Reunion Island

2003 ◽  
Author(s):  
P. Coheur ◽  
M. Bach ◽  
M. Carleer ◽  
C. Clerbaux ◽  
R. Colin ◽  
...  
Keyword(s):  
Ftir Spectroscopy ◽  
Reunion Island ◽  
Solar Absorption ◽  
Réunion Island

scholarly journals CFC-11, CFC-12 and HCFC-22 ground-based remote sensing FTIR measurements at Réunion Island and comparisons with MIPAS/ENVISAT data

2016 ◽  
Vol 9 (11) ◽  
pp. 5621-5636 ◽  
Author(s):  
Minqiang Zhou ◽  
Corinne Vigouroux ◽  
Bavo Langerock ◽  
Pucai Wang ◽  
Geoff Dutton ◽  
...  
Keyword(s):  
Michelson Interferometer ◽  
Species Group ◽  
Reunion Island ◽  
Solar Absorption ◽  
Trace Species ◽  
Réunion Island ◽  
Peak Sensitivity ◽  
Random Uncertainties ◽  
Absorption Measurements ◽  
Good Agreement

Abstract. Profiles of CFC-11 (CCl3F), CFC-12 (CCl2F2) and HCFC-22 (CHF2Cl) have been obtained from Fourier transform infrared (FTIR) solar absorption measurements above the Saint-Denis (St Denis) and Maïdo sites at Réunion Island (21° S, 55° E) with low vertical resolution. FTIR profile retrievals are performed by the well-established SFIT4 program and the detail retrieval strategies along with the systematic/random uncertainties of CFC-11, CFC-12 and HCFC-22 are discussed in this study. The FTIR data of all three species are sensitive to the whole troposphere and the lowermost stratosphere, with the peak sensitivity between 5 and 10 km. The ground-based FTIR data have been compared with the collocated Michelson Interferometer for Passive Atmospheric Sounding (MIPAS/ENVISAT) data and found to be in good agreement: the observed mean relative biases and standard deviations of the differences between the smoothed MIPAS and FTIR partial columns (6–30 km) are (−4.3 and 4.4 %), (−2.9 and 4.6 %) and (−0.7 and 4.8 %) for CFC-11, CFC-12 and HCFC-22, respectively, which are within the combined error budgets from both measurements. The season cycles of CFC-11, CFC-12 and HCFC-22 from FTIR measurements and MIPAS data show a similar variation: concentration is highest in February–April and lowest in August–October. The trends derived from the combined St Denis and Maïdo FTIR time series are −0.86 ± 0.12 and 2.84 ± 0.06 % year−1 for CFC-11 and HCFC-22, respectively, for the period 2004 to 2016, and −0.76 ± 0.05 % year−1 for CFC-12 for 2009 to 2016. These measurements are consistent with the trends observed by the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Division's (GMD) Halocarbons & other Atmospheric Trace Species Group (HATS) measurements at Samoa (14.2° S, 170.5° W) for CFC-11 (−0.87 ± 0.04 % year−1), but slightly weaker for HCFC-22 (3.46 ± 0.05 %) year−1 and stronger for CFC-12 (−0.60 ± 0.02 % year−1).

scholarly journals FTIR time-series of biomass burning products (HCN, C<sub>2</sub>H<sub>6</sub>, C<sub>2</sub>H<sub>2</sub>, CH<sub>3</sub>OH, and HCOOH) at Reunion Island (21° S, 55° E) and comparisons with model data

2012 ◽  
Vol 12 (21) ◽  
pp. 10367-10385 ◽  
Author(s):  
C. Vigouroux ◽  
T. Stavrakou ◽  
C. Whaley ◽  
B. Dils ◽  
V. Duflot ◽  
...  
Keyword(s):  
Time Series ◽  
Biomass Burning ◽  
Transport Model ◽  
Chemical Species ◽  
Global Scale ◽  
Reunion Island ◽  
Chemical Transport Model ◽  
Solar Absorption ◽  
Réunion Island ◽  
The Indian Ocean

Abstract. Reunion Island (21° S, 55° E), situated in the Indian Ocean at about 800 km east of Madagascar, is appropriately located to monitor the outflow of biomass burning pollution from Southern Africa and Madagascar, in the case of short-lived compounds, and from other Southern Hemispheric landmasses such as South America, in the case of longer-lived species. Ground-based Fourier transform infrared (FTIR) solar absorption observations are sensitive to a large number of biomass burning products. We present in this work the FTIR retrieval strategies, suitable for very humid sites such as Reunion Island, for hydrogen cyanide (HCN), ethane (C2H6), acetylene (C2H2), methanol (CH3OH), and formic acid (HCOOH). We provide their total columns time-series obtained from the measurements during August–October 2004, May–October 2007, and May 2009–December 2010. We show that biomass burning explains a large part of the observed seasonal and interannual variability of the chemical species. The correlations between the daily mean total columns of each of the species and those of CO, also measured with our FTIR spectrometer at Reunion Island, are very good from August to November (R &amp;geq; 0.86). This allows us to derive, for that period, the following enhancement ratios with respect to CO: 0.0047, 0.0078, 0.0020, 0.012, and 0.0046 for HCN, C2H6, C2H2, CH3OH, and HCOOH, respectively. The HCN ground-based data are compared to the chemical transport model GEOS-Chem, while the data for the other species are compared to the IMAGESv2 model. We show that using the HCN/CO ratio derived from our measurements (0.0047) in GEOS-Chem reduces the underestimation of the modeled HCN columns compared with the FTIR measurements. The comparisons between IMAGESv2 and the long-lived species C2H6 and C2H2 indicate that the biomass burning emissions used in the model (from the GFED3 inventory) are probably underestimated in the late September–October period for all years of measurements, and especially in 2004. The comparisons with the short-lived species, CH3OH and HCOOH, with lifetimes of around 5 days, suggest that the emission underestimation in late September–October 2004, occurs more specifically in the Southeastern Africa-Madagascar region. The very good correlation of CH3OH and HCOOH with CO suggests that, despite the dominance of the biogenic source of these compounds on the global scale, biomass burning is their major source at Reunion Island between August and November.

scholarly journals CFC-11, CFC-12 and HCFC-22 ground-based remote sensing FTIR measurements at Reunion Island and comparisons with MIPAS/ENVISAT data

2016 ◽  
Author(s):  
Minqiang Zhou ◽  
Corinne Vigouroux ◽  
Bavo Langerock ◽  
Pucai Wang ◽  
Geoff Dutton ◽  
...  
Keyword(s):  
Michelson Interferometer ◽  
Species Group ◽  
Reunion Island ◽  
Solar Absorption ◽  
Trace Species ◽  
Réunion Island ◽  
Peak Sensitivity ◽  
Random Uncertainties ◽  
Absorption Measurements ◽  
Good Agreement

Abstract. Profiles of CFC-11 (CCl3F), CFC-12 (CCl2F2) and HCFC-22 (CHF2Cl) have been obtained from Fourier transform infrared (FTIR) solar absorption measurements above the Saint-Denis (St Denis) and Maïdo sites at Reunion Island (21º S, 55º E) with low vertical resolution. FTIR profile retrievals are performed by the SFIT4 program and the detail retrieval strategies along with the systematic/random uncertainties of CFC-11, CFC-12, and HCFC-22 are discussed in this study. The FTIR data of all three species are sensitive to the whole troposphere and the lowermost stratosphere, with the peak sensitivity between 5 and 10 km. The trends derived from the combined St Denis and Maïdo FTIR time-series are −0.86 ± 0.12 % and 2.75 ± 0.12 % for CFC-11 and HCFC-22, respectively, for the period 2004 to 2016 , and −0.76 ± 0.05 % for CFC-12 for 2009 to 2016. These measurements are consistent with the trends observed by the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Division’s (GMD) Halocarbons &amp; other Atmospheric Trace Species Group (HATS) measurements at Samoa (14.2° S, 170.5° W) for CFC-11 (−0.87 ± 0.04 %), but slightly weaker for HCFC-22 (3.46 ± 0.05 %) and stronger for CFC-12 (-0.60 ± 0.02 %). The ground-based FTIR data have also been compared with the collocated Michelson Interferometer for Passive Atmospheric Sounding (MIPAS/ENVISAT) data, and found to be in good agreement: the observed mean relative biases and standard deviations of the differences between the smoothed MIPAS and FTIR partial columns (6−30 km) are (−4.3 % and 4.4 %), (−2.9 % and 4.6 %) and (−0.7 % and 6.0 %) for CFC-11, CFC-12, and HCFC-22, respectively, which are within the combined error budgets from both measurements.

scholarly journals FTIR time-series of biomass burning products (HCN, C<sub>2</sub>H<sub>6</sub>, C<sub>2</sub>H<sub>2</sub>, CH<sub>3</sub>OH, and HCOOH) at Reunion Island (21° S, 55° E) and comparisons with model data

2012 ◽  
Vol 12 (6) ◽  
pp. 13733-13786 ◽  
Author(s):  
C. Vigouroux ◽  
T. Stavrakou ◽  
C. Whaley ◽  
B. Dils ◽  
V. Duflot ◽  
...  
Keyword(s):  
Time Series ◽  
Biomass Burning ◽  
Transport Model ◽  
Chemical Species ◽  
Global Scale ◽  
Reunion Island ◽  
Chemical Transport Model ◽  
Solar Absorption ◽  
Réunion Island ◽  
The Indian Ocean

Abstract. Reunion Island (21° S, 55° E), situated in the Indian Ocean at about 800 km east of Madagascar, is appropriately located to monitor the outflow of biomass burning pollution from Southern Africa and Madagascar, in the case of short-lived compounds, and from other Southern Hemispheric landmasses such as South America, in the case of longer-lived species. Ground-based Fourier transform infrared (FTIR) solar absorption observations are sensitive to a large number of biomass burning products. We present in this work the FTIR retrieval strategies, suitable for very humid sites such as Reunion Island, for hydrogen cyanide (HCN), ethane (C2H6), acetylene (C2H2), methanol (CH3OH), and formic acid (HCOOH). We provide their total columns time-series obtained from the measurements during August–October 2004, May–October 2007, and May 2009–December 2010. We show that biomass burning explains a large part of the observed seasonal and interannual variability of the chemical species. The correlations between the daily mean total columns of each of the species and those of CO, also measured with our FTIR spectrometer at Reunion Island, are very good from August to November (R≥0.86). This allows us to derive, for that period, the following enhancement ratios with respect to CO: 0.0047, 0.0078, 0.0020, 0.012, and 0.0046 for HCN, C2H6, C2H2, CH3OH, and HCOOH, respectively. The HCN ground-based data are compared to the chemical transport model GEOS-Chem, while the data for the other species are compared to the IMAGESv2 model. We show that using the HCN/CO ratio derived from our measurements (0.0047) in GEOS-Chem reduces the underestimation of the modelled HCN columns compared with the FTIR measurements. The comparisons between IMAGESv2 and the long-lived species C2H6 and C2H2 indicate that the biomass burning emissions used in the model (from the GFED3 inventory) are probably underestimated in the late September–October period for all years of measurements, and especially in 2004. The comparisons with the short-lived species, CH3OH and HCOOH, with lifetimes of around 5 days, suggest that the emission underestimation in late September–October 2004, occurs more specifically in the Southeastern Africa-Madagascar region. The very good correlation of CH3OH and HCOOH with CO suggests that, despite the dominance of the biogenic source of these compounds on the global scale, biomass burning is their major source at Reunion Island between August and November.

scholarly journals Cloud Radar Observations of Diurnal and Seasonal Cloudiness over Reunion Island

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 868
Author(s):  
Jonathan Durand ◽  
Edouard Lees ◽  
Olivier Bousquet ◽  
Julien Delanoë ◽  
François Bonnardot
Keyword(s):  
Sea Breeze ◽  
Satellite System ◽  
Research Infrastructure ◽  
Weather Data ◽  
Reunion Island ◽  
Wet Season ◽  
Trade Winds ◽  
Cloud Radar ◽  
Réunion Island ◽  
Global Navigation Satellite

In November 2016, a 95 GHz cloud radar was permanently deployed in Reunion Island to investigate the vertical distribution of tropical clouds and monitor the temporal variability of cloudiness in the frame of the pan-European research infrastructure Aerosol, Clouds and Trace gases Research InfraStructure (ACTRIS). In the present study, reflectivity observations collected during the two first years of operation (2016–2018) of this vertically pointing cloud radar are relied upon to investigate the diurnal and seasonal cycle of cloudiness in the northern part of this island. During the wet season (December–March), cloudiness is particularly pronounced between 1–3 km above sea level (with a frequency of cloud occurrence of 45% between 12:00–19:00 LST) and 8–12 km (with a frequency of cloud occurrence of 15% between 14:00–19:00 LST). During the dry season (June–September), this bimodal vertical mode is no longer observed and the vertical cloud extension is essentially limited to a height of 3 km due to both the drop-in humidity resulting from the northward migration of the ITCZ and the capping effect of the trade winds inversion. The frequency of cloud occurrence is at its maximum between 13:00–18:00 LST, with a probability of 35% at 15 LST near an altitude of 2 km. The analysis of global navigation satellite system (GNSS)-derived weather data also shows that the diurnal cycle of low- (1–3 km) and mid-to-high level (5–10 km) clouds is strongly correlated with the diurnal evolution of tropospheric humidity, suggesting that additional moisture is advected towards the island by the sea breeze regime. The detailed analysis of cloudiness observations collected during the four seasons sampled in 2017 and 2018 also shows substantial differences between the two years, possibly associated with a strong positive Indian Ocean Southern Dipole (IOSD) event extending throughout the year 2017.

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