The fine-scale structure of the trade wind cumuli over Barbados &ndash; an introduction to the CARRIBA project

Abstract. The CARRIBA (Cloud, Aerosol, Radiation and tuRbulence in the trade wInd regime over BArbados) project, focused on high resolution and collocated measurements of thermodynamic, turbulent, microphysical, and radiative properties of trade wind cumuli over Barbados, is introduced. The project is based on two one-month field campaigns in November 2010 (climatic wet season) and April 2011 (climatic dry season). Observations are based on helicopter-borne and ground-based measurements in an area of 100 km2 off the coast of Barbados. CARRIBA is accompanied by long-term observations at the Barbados Cloud Observatory located at the East coast of Barbados since early in 2010 and which provides a longer-term context for the CARRIBA measurements. The deployed instrumentation and sampling strategy are presented together with a classification of the meteorological conditions. The two campaigns were influenced by different air masses advected from the Caribbean area, the Atlantic Ocean, and the African continent which led to distinct aerosol conditions. Pristine conditions with low aerosol particle number concentrations of ~100 cm3 were alternating with periods influenced by Saharan dust or aerosol from biomass burning resulting in comparably high number concentrations of ~ 500 cm3. The biomass burning aerosol was originating from both the Caribbean area and Africa. The shallow cumulus clouds responded to the different aerosol conditions with a wide range of mean droplet sizes and number concentrations. Two days with different aerosol and cloud microphysical properties but almost identical meteorological conditions have been analyzed in detail. The differences in the droplet number concentration and droplet sizes appear not to show any significant change for turbulent cloud mixing, but the relative roles of droplet inertia and sedimentation in initiating coalescence, as well as the cloud reflectivity, do change substantially.

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The fine-scale structure of the trade wind cumuli over Barbados – an introduction to the CARRIBA project

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-28609-2012 ◽

2012 ◽

Vol 12 (10) ◽

pp. 28609-28660 ◽

Cited By ~ 4

Author(s):

H. Siebert ◽

J. Bethke ◽

E. Bierwirth ◽

T. Conrath ◽

K. Dieckmann ◽

...

Keyword(s):

Sampling Strategy ◽

Saharan Dust ◽

Trade Wind ◽

Wet Season ◽

Cumulus Clouds ◽

Air Masses ◽

Wide Range ◽

Caribbean Area ◽

Droplet Sizes ◽

The Caribbean

Abstract. The CARRIBA (Cloud, Aerosol, Radiation and tuRbulence in the trade wInd regime over BArbados) project with focus on trade wind cumuli over Barbados is introduced. The project is based on two one-month field campaigns in November 2010 (climatic wet season) and April 2011 (climatic dry season). Observations are based on helicopter-borne and ground-based measurements in a square of 100 km2 off the coast of Barbados. CARRIBA is accompanied by long-term observations at the Barbados Cloud Observatory located at the East coast of Barbados since early in 2010 and which provides longer-term context for the CARRIBA measurements. Deployed instrumentation and sampling strategy are presented together with a classification of the meteorological conditions. The two campaigns were influenced by different air masses advected from the Caribbean area, the Atlantic Ocean, as well as the African continent which led to distinct aerosol conditions. Therefore, pristine conditions with low aerosol particle number concentrations of ~100 cm3 were alternating with periods influenced by Saharan dust or aerosol from biomass burning resulting in comparable high number concentrations ~500 cm3. The later was originating from both, the Caribbean area and Africa. The shallow cumulus clouds responded to the different aerosol conditions with a wide range of mean droplet sizes and number concentrations. Effective radii in the range of 7 to 18 μm have been observed. Finally, the four leading topics of CARRIBA – Clouds, Aerosol, Radiation and tuRbulence – are motivated and illustrated by selected findings and measurement examples.

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Long range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the Western Mediterranean basin

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-32323-2015 ◽

2015 ◽

Vol 15 (22) ◽

pp. 32323-32365 ◽

Cited By ~ 5

Author(s):

G. Ancellet ◽

J. Pelon ◽

J. Totems ◽

P. Chazette ◽

A. Bazureau ◽

...

Keyword(s):

Long Range ◽

Biomass Burning ◽

North American ◽

Western Mediterranean ◽

Saharan Dust ◽

Trade Wind ◽

Long Range Transport ◽

Range Transport ◽

Aerosol Sources ◽

Aerosol Source

Abstract. Long range transport of biomass burning (BB) aerosols between North America and the Mediterranean region took place in June 2013. A large number of ground based and airborne lidar measurements were deployed in the Western Mediterranean during the Chemistry-AeRosol Mediterranean EXperiment (ChArMEx) intensive observation period. A detailed analysis of the potential North American aerosol sources is conducted including the assessment of their transport to Europe using forward simulations of the FLEXPART Lagrangian particle dispersion model initialized using satellite observations by MODIS and CALIOP. The three dimensional structure of the aerosol distribution in the ChArMEx domain observed by the ground-based lidars (Menorca, Barcelona and Lampedusa), a Falcon-20 aircraft flight and three CALIOP tracks, agree very well with the model simulation of the three major sources considered in this work: Canadian and Colorado fires, a dust storm from Western US and the contribution of Saharan dust streamers advected from the North Atlantic trade wind region into the Westerlies region. Four aerosol types were identified using the optical properties of the observed aerosol layers (aerosol depolarization ratio, lidar ratio) and the transport model analysis of the contribution of each aerosol source: (I) pure BB layer, (II) weakly dusty BB, (III) significant mixture of BB and dust transported from the trade wind region (IV) the outflow of Saharan dust by the subtropical jet and not mixed with BB aerosol. The contribution of the Canadian fires is the major aerosol source during this episode while mixing of dust and BB is only significant at altitude above 5 km. The mixing corresponds to a 20–30 % dust contribution in the total aerosol backscatter. The comparison with the MODIS AOD horizontal distribution during this episode over the Western Mediterranean sea shows that the Canadian fires contribution were as large as the direct northward dust outflow from Sahara.

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Cloud macrophysical properties from airborne observations during EUREC4A

10.5194/egusphere-egu2020-11106 ◽

2020 ◽

Author(s):

Heike Konow ◽

Marcus Klingebiel ◽

Felix Ament

Keyword(s):

Deep Convection ◽

Dry Season ◽

Trade Wind ◽

Special Focus ◽

Wet Season ◽

Diurnal Cycles ◽

Cloud Radar ◽

Wide Range ◽

Macrophysical Properties ◽

Different Response

Trade wind cumulus clouds are the predominant cloud type over the tropical Atlantic east of the island of Barbados. Parameters describing their macroscopic shape can help characterizing and comparing general features of clouds. This characterizing will indirectly help to constrain estimates of climate sensitivity, because models with different structures of trade wind cumuli feature different response to increased CO2 contents.Two aircraft campaigns with the HALO (High Altitude LOng range) aircraft took place in the recent past in this region: NARVAL-South (Next-generation Aircraft Remote-Sensing for VALidation studies) in December 2013, during the dry season, and NARVAL2 in August 2016, during the wet season. During these two campaigns, a wide range of cloud regimes from shallow to deep convection were sampled. This past observations are now extended with observations from this year&#8217;s measurement campaign EUREC4A, again during the dry season. EUREC4A is endorsed as WCRP capstone experiment and the synergy of four research aircraft, four research vessels and numerous additional observations will provide comprehensive characterizations of trade wind clouds and their environment.Part of the NARVAL payload on HALO is a 35 GHz cloud radar, which has been deployed on HALO on several missions since 2013. These cloud radar measurements are used to segment individual clouds entities by applying connected component analysis to the radar cloud mask. From these segmented individual clouds, macrophysical parameters are derived to characterize each individual cloud. This presentation will give an overview of the cloud macrophysics observed from HALO during EUREC4A. Typical macrophysical parameters, i.e. cloud depth, cloud length, cloud fraction, are analyzed. We will relate these to observations from past campaigns and assess the representativeness of EUREC4A. As special focus of the EUREC4A campaign, measurements will be performed during different times of the day to detect diurnal cycles. Macrophysical parameters can be used to characterize changes over the day and cloud scenes of similar clouds types can be identified.

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New insights in the global cycle of acetonitrile: release from theocean and dry deposition in the tropical savanna of Venezuela

Atmospheric Chemistry and Physics ◽

10.5194/acp-4-275-2004 ◽

2004 ◽

Vol 4 (1) ◽

pp. 275-280 ◽

Cited By ~ 20

Author(s):

E. Sanhueza ◽

R. Holzinger ◽

B. Kleiss ◽

L. Donoso ◽

P. J. Crutzen

Keyword(s):

Boundary Layer ◽

Biomass Burning ◽

Dry Deposition ◽

Mixed Boundary ◽

Deposition Velocity ◽

Caribbean Sea ◽

Proton Transfer Reaction ◽

Wet Season ◽

Mixing Ratios ◽

The Caribbean

Abstract. Using the proton transfer reaction mass spectrometry (PTR-MS) technique, acetonitrile was measured during the wet season in a Venezuelan woodland savanna. The site was located downwind of the Caribbean Sea and no biomass burning events were observed in the region. High boundary layer concentrations of 211±36pmol/mol (median, ±standard deviation) were observed during daytime in the well mixed boundary layer, which is about 60pmol/mol above background concentrations recently measured over the Mediterranean Sea and the Pacific Ocean. Most likely acetonitrile is released from the warm waters of the Caribbean Sea thereby enhancing mixing ratios over Venezuela. Acetonitrile concentrations will probably still be much higher in biomass burning plumes, however, the general suitability of acetonitrile as a biomass burning marker should be treated with care. During nights, acetonitrile dropped to levels typically around 120pmol/mol, which is consistent with a dry deposition velocity of 0.14cm/s when a nocturnal boundary layer height of 100m is assumed.

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Long-range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the western Mediterranean basin

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-4725-2016 ◽

2016 ◽

Vol 16 (7) ◽

pp. 4725-4742 ◽

Cited By ~ 32

Author(s):

Gerard Ancellet ◽

Jacques Pelon ◽

Julien Totems ◽

Patrick Chazette ◽

Ariane Bazureau ◽

...

Keyword(s):

Long Range ◽

Biomass Burning ◽

North American ◽

Western Mediterranean ◽

Saharan Dust ◽

Trade Wind ◽

Long Range Transport ◽

Range Transport ◽

Aerosol Sources ◽

Aerosol Source

Abstract. Long-range transport of biomass burning (BB) aerosols between North America and the Mediterranean region took place in June 2013. A large number of ground-based and airborne lidar measurements were deployed in the western Mediterranean during the Chemistry-AeRosol Mediterranean EXperiment (ChArMEx) intensive observation period. A detailed analysis of the potential North American aerosol sources is conducted including the assessment of their transport to Europe using forward simulations of the FLEXPART Lagrangian particle dispersion model initialized using satellite observations by MODIS and CALIOP. The three-dimensional structure of the aerosol distribution in the ChArMEx domain observed by the ground-based lidars (Minorca, Barcelona and Lampedusa), a Falcon-20 aircraft flight and three CALIOP tracks, agrees very well with the model simulation of the three major sources considered in this work: Canadian and Colorado fires, a dust storm from western US and the contribution of Saharan dust streamers advected from the North Atlantic trade wind region into the westerlies region. Four aerosol types were identified using the optical properties of the observed aerosol layers (aerosol depolarization ratio, lidar ratio) and the transport model analysis of the contribution of each aerosol source: (i) pure BB layer, (ii) weakly dusty BB, (iii) significant mixture of BB and dust transported from the trade wind region, and (iv) the outflow of Saharan dust by the subtropical jet and not mixed with BB aerosol. The contribution of the Canadian fires is the major aerosol source during this episode while mixing of dust and BB is only significant at an altitude above 5 km. The mixing corresponds to a 20–30 % dust contribution in the total aerosol backscatter. The comparison with the MODIS aerosol optical depth horizontal distribution during this episode over the western Mediterranean Sea shows that the Canadian fire contributions were as large as the direct northward dust outflow from Sahara.

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Dust transport and horizontal fluxes measurement with spaceborne lidars ALADIN, CALIOP and model reanalysis data

10.5194/acp-2021-219 ◽

2021 ◽

Author(s):

Guangyao Dai ◽

Kangwen Sun ◽

Xiaoye Wang ◽

Songhua Wu ◽

Xiangying E ◽

...

Keyword(s):

Optical Properties ◽

Atlantic Ocean ◽

Caribbean Sea ◽

Saharan Dust ◽

Trade Wind ◽

Development Phase ◽

Dust Event ◽

Dust Transport ◽

The Caribbean ◽

Emission Phase

Abstract. In this paper, a long-term large-scale Sahara dust transport event occurred during 14 June and 27 June 2020 is tracked with the spaceborne lidars ALADIN and CALIOP observations and the models ECMWF and HYSPLIT analysis. We evaluate the performance of the ALADIN and CALIOP on the observations of dust optical properties and wind fields and explore the capability in tracking the dust events and in calculating the dust horizontal mass fluxes with the combination of measurement data from ALADIN and CALIOP coupled with the products from ECMWF and HYSPLIT. Compared with the traditional assessments based on the data from CALIOP and models, the complement of Aeolus-produced aerosol optical properties and wind data will significantly improve the accuracy of dust horizontal flux estimations. The dust plumes are identified with AIRS/Aqua Dust Score Index and with the Vertical Feature Mask products from CALIPSO. The emission, dispersion, transport and deposition of the dust event are monitored using the data from HYSPLIT, CALIPSO and AIRS/Aqua. With the quasi-synchronization observations by ALADIN and CALIOP, combining the wind vectors and relative humidity, the dust horizontal fluxes are calculated. From this study, it is found that the dust event generated on 14 and 15 June 2020 from Sahara Desert in North Africa, and then dispersed and transported westward over the Atlantic Ocean, and finally deposited in the Atlantic Ocean, the Americas and the Caribbean Sea. During the transport and deposition processes, the dust plumes are trapped in the Northeasterly Trade-wind zone between the latitudes of 5° N and 30° N and altitudes of 0 km and 6 km (in this paper we name this space area as “Saharan dust eastward transport tunnel”). From the measurement results on 19 June 2020, influenced by the hygroscopic effect and mixing with other types aerosols, the backscatter coefficients of dust plumes are increasing along the transport routes, with 3.88 × 10−6 ± 2.59 × 10−6 m−1 sr−1 in “dust portion during emission phase”, 7.09 × 10−6 ± 3.34 × 10−6 m−1 sr−1 in “dust portion during development phase” and 7.76 × 10−6 ± 3.74 × 10−6 m−1 sr−1 in “dust portion during deposition phase”. Finally, the horizontal fluxes at different dust parts and heights on 19 June and on entire transport routine during transportation are computed. On 19 June, the dust horizontal fluxes are about 2.17 ± 1.83 mg m−2 s−1 in dust portion during emission phase, 2.72 ± 1.89 mg m−2 s−1 in dust portion during development phase and 3.01 ± 2.77 mg m−2 s−1 in dust portion during deposition phase. In the whole life-time of the dust event, the dust horizontal fluxes are about 1.30 ± 1.07 mg m−2 s−1 on 15 June 2020, 2.62 ± 1.88 mg m−2 s−1 on 16 June 2020, 2.72 ± 1.89 mg m−2 s−1 on 19 June 2020, 1.98 ± 1.41 mg m−2 s−1 on 24 June 2020 and 2.11 ± 1.74 mg m−2 s−1 on 27 June 2020. From this study, it is found that the minimum of the fluxes appears when the dust event is initially generated on 15 June. During the dust development stage, the horizontal fluxes gradually increase and reach to the maximum value on 19 June with the enhancement of the dust event. Then, the horizontal fluxes gradually decrease since most of the dust deposited in the Atlantic Ocean, the Americas and the Caribbean Sea. Combining the Chlorophyll concentrations data provided by MODIS-Aqua, the Saharan Dust is found transported across the oligotrophic regions Atlantic Ocean towards the Americas and Caribbean Sea, which are also oligotrophic regions. The mineral dust delivers micronutrients including soluble Fe and P to the deposition zones and has the potential to fertilizing the ocean and increase the primary productivity in the Atlantic Ocean and Caribbean Sea.

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New insights in the global cycle of acetonitrile: release from the ocean and acetonitrile: release from the ocean and Venezuela

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-3-5275-2003 ◽

2003 ◽

Vol 3 (5) ◽

pp. 5275-5288 ◽

Cited By ~ 1

Author(s):

E. Sanhueza ◽

R. Holzinger ◽

B. Kleiss ◽

L. Donoso ◽

P. J. Crutzen

Keyword(s):

Boundary Layer ◽

Biomass Burning ◽

Mixed Boundary ◽

Deposition Velocity ◽

Caribbean Sea ◽

Proton Transfer Reaction ◽

Wet Season ◽

Boundary Layer Height ◽

Mixing Ratios ◽

The Caribbean

Abstract. CUsing the proton transfer reaction mass spectrometry (PTR-MS) technique, acetonitrile was measured during the wet season in a Venezuelan woodland savanna. The site was located downwind of the Caribbean Sea and no biomass burning events were observed in the region. High boundary layer concentrations of 211 ±36 pmol/mol (median, ± standard deviation) were observed during daytime in the well mixed boundary layer, which is about 60 pmol/mol above background concentrations recently measured over the Mediterranean Sea and the Pacific Ocean. Most likely acetonitrile is released from the warm waters of the Caribbean Sea thereby enhancing mixing ratios over Venezuela. Acetonitrile concentrations will probably still be much higher in biomass burning plumes, however, the general suitability of acetonitrile as a biomass burning marker should be treated with care. During nights, acetonitrile dropped to levels typically around 120 pmol/mol, which is consistent with a dry deposition velocity of ~0.14 cm/s when a nocturnal boundary layer height of 100 m is assumed.

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