Airborne lidar observations of long-range transport in the free troposphere

1984 ◽  
Vol 18 (10) ◽  
pp. 749-756 ◽  
Author(s):  
Scott T. Shipley ◽  
Edward V. Browell ◽  
David S. McDougal ◽  
Brian L. Orndorff ◽  
Philip. Haagenson
2008 ◽  
Vol 8 (11) ◽  
pp. 2999-3014 ◽  
Author(s):  
A. van Donkelaar ◽  
R. V. Martin ◽  
W. R. Leaitch ◽  
A. M. Macdonald ◽  
T. W. Walker ◽  
...  

Abstract. We interpret a suite of satellite, aircraft, and ground-based measurements over the North Pacific Ocean and western North America during April–May 2006 as part of the Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign to understand the implications of long-range transport of East Asian emissions to North America. The Canadian component of INTEX-B included 33 vertical profiles from a Cessna 207 aircraft equipped with an aerosol mass spectrometer. Long-range transport of organic aerosols was insignificant, contrary to expectations. Measured sulfate plumes in the free troposphere over British Columbia exceeded 2 μg/m3. We update the global anthropogenic emission inventory in a chemical transport model (GEOS-Chem) and use it to interpret the observations. Aerosol Optical Depth (AOD) retrieved from two satellite instruments (MISR and MODIS) for 2000–2006 are analyzed with GEOS-Chem to estimate an annual growth in Chinese sulfur emissions of 6.2% and 9.6%, respectively. Analysis of aircraft sulfate measurements from the NASA DC-8 over the central Pacific, the NSF C-130 over the east Pacific and the Cessna over British Columbia indicates most Asian sulfate over the ocean is in the lower free troposphere (800–600 hPa), with a decrease in pressure toward land due to orographic effects. We calculate that 56% of the measured sulfate between 500–900 hPa over British Columbia is due to East Asian sources. We find evidence of a 72–85% increase in the relative contribution of East Asian sulfate to the total burden in spring off the northwest coast of the United States since 1985. Campaign-average simulations indicate anthropogenic East Asian sulfur emissions increase mean springtime sulfate in Western Canada at the surface by 0.31 μg/m3 (~30%) and account for 50% of the overall regional sulfate burden between 1 and 5 km. Mean measured daily surface sulfate concentrations taken in the Vancouver area increase by 0.32 μg/m3 per 10% increase in the simulated fraction of Asian sulfate, and suggest current East Asian emissions episodically degrade local air quality by more than 1.5 μg/m3.


2008 ◽  
Vol 8 (1) ◽  
pp. 4017-4057 ◽  
Author(s):  
A. van Donkelaar ◽  
R. V. Martin ◽  
W. R. Leaitch ◽  
A. M. Macdonald ◽  
T. W. Walker ◽  
...  

Abstract. We interpret a suite of satellite, aircraft, and ground-based measurements over the North Pacific Ocean and western North America during April–May 2006 as part of the Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign to understand the implications of long-range transport of East Asian emissions to North America. The Canadian component of INTEX-B included 33 vertical profiles from a Cessna 207 aircraft equipped with an aerosol mass spectrometer. Long-range transport of organic aerosols was insignificant. Measured sulfate plumes in the free troposphere over British Columbia exceeded 1 μg/m3. We update the global anthropogenic emission inventory in a chemical transport model (GEOS-Chem) and use it to interpret the observations. Trends in Aerosol Optical Depth (AOD) retrieved from two satellite instruments (MISR and MODIS) for 2000–2006 are analyzed with GEOS-Chem to estimate an annual growth in Chinese sulfur emissions of 6.2% and 9.6%, respectively. Analysis of aircraft sulfate measurements from the NASA DC-8 over the central Pacific, the NSF C-130 over the east Pacific and the Cessna over British Columbia indicates most Asian sulfate over the ocean is in the lower free troposphere (800–600 hPa), with a decrease in pressure toward land due to orographic effects. We calculate that 63% of the measured sulfate at 600 hPa over British Columbia is due to East Asian sources. Simulation of INTEX-B and May 1985 aircraft measurements off the northwest coast of the United States reveals a 2.4–3.4 fold increase in the relative contribution of East Asian sulfate to the total burden. Campaign-average simulations indicate anthropogenic East Asian sulfur emissions increase mean springtime sulfate in Western Canada at the surface by 0.14–0.19 μg/m3 (~30%) and account for 40% of the overall regional sulfate burden between 1 and 5 km. Mean measured daily surface sulfate concentrations taken in the Vancouver area increase by 0.27 μg/m3 per 10% increase in the simulated fraction of Asian sulfate, suggesting current East Asian emissions degrade local air quality.


2013 ◽  
Vol 13 (15) ◽  
pp. 7511-7529 ◽  
Author(s):  
A. D. Clarke ◽  
S. Freitag ◽  
R. M. C. Simpson ◽  
J. G. Hudson ◽  
S. G. Howell ◽  
...  

Abstract. Airborne aerosol measurements in the central equatorial Pacific during PASE (Pacific Atmospheric Sulfur Experiment) revealed that cloud condensation nuclei (CCN) activated in marine boundary layer (MBL) clouds were strongly influenced by entrainment from the free troposphere (FT). About 65% entered at sizes effective as CCN in MBL clouds, while ~25% entered the MBL too small to activate but subsequently grew via gas to particle conversion. The remaining ~10% were inferred to be sea salt aerosol. FT aerosols at low carbon monoxide (CO) mixing ratios (< 63 ppbv) were mostly volatile at 360 °C with a number mode peak of around 30–40 nm dry diameter and tended to be associated with cloud outflow from distant (3000 km or more) deep convection. Higher CO concentrations were commonly associated with trajectories from South America and the Amazon region (ca. ~10 000 km away) and occurred in layers indicative of combustion sources (biomass burning season) partially scavenged by precipitation. These had number modes near 60–80 nm dry diameter with a large fraction of CCN.2 (those activated at 0.2% supersaturation and representative of MBL clouds) prior to entrainment into the MBL. Flight averaged concentrations of CCN.2 were similar for measurements near the surface, below the inversion and in the FT just above the inversion, confirming that subsidence and entrainment of FT aerosol strongly influenced MBL CCN.2. Concurrent flight-to-flight variations of CCN.2 at all altitudes below 3 km also imply MBL CCN.2 concentrations were in quasi-equilibrium with the FT over a 2–3 day timescale. The observed FT transport over thousands of kilometers indicates teleconnections between MBL CCN and cloud-scavenged sources of both natural and/or residual combustion origin. Nonetheless, in spite of its importance, this source of CCN number is not well represented in most current models and is generally not detectable by satellite because of the low aerosol scattering in such layers as a result of cloud scavenging. In addition, our measurements confirm nucleation in the MBL was not evident during PASE and argue against a localized linear relation in the MBL between dimethyl sulfide (DMS) and CCN suggested by the CLAW hypothesis. However, when the FT is not impacted by long-range transport, sulfate aerosol derived from DMS pumped aloft in the ITCZ (Inter-Tropical Convergence Zone) can provide a source of CCN to the boundary layer via FT teleconnections involving more complex non-linear processes.


Author(s):  
Zhaoyan Liu ◽  
Ali Omar ◽  
Mark Vaughan ◽  
Johnathan Hair ◽  
Chieko Kittaka ◽  
...  

2018 ◽  
Author(s):  
Andreas Foth ◽  
Thomas Kanitz ◽  
Ronny Engelmann ◽  
Holger Baars ◽  
Martin Radenz ◽  
...  

Abstract. Within this publication, lidar observations of the vertical aerosol distribution above Punta Arenas, Chile (53.2° S and 50.9° W) which have been performed with the Raman lidar PollyXT from December 2009 to April 2010 are presented. Pristine marine aerosol conditions related to the prevailing westerly circulation dominated the measurements. Lofted aerosol layers could only be observed eight times during the whole measurement period. Two case studies are presented showing long-range transport of smoke from biomass burning in Australia and regionally transported dust from the Patagonian Desert, respectively. The aerosol sources are identified by trajectory analyses with HYSPLIT and FLEXPART. However, seven of the eight analysed cases with lofted layers show an aerosol optical thickness of less than 0.05. From the lidar observations a mean planetary boundary layer (PBL) top height of 1150 ± 350 m was determined. An analysis of particle backscatter coefficients confirms that the majority of the aerosol is attributed to the PBL while the free troposphere is characterized by a very low background aerosol concentration. The ground-based lidar observations at 532 and 1064 nm are supplemented by the AERONET Sun photometers and the space-borne lidar CALIOP on board of CALIPSO. The averaged AOT determined by CALIOP was 0.02 ± 0.01 at Punta Arenas from 2009 to 2010.


2017 ◽  
Author(s):  
Franziska Rittmeister ◽  
Albert Ansmann ◽  
Ronny Engelmann ◽  
Annett Skupin ◽  
Holger Baars ◽  
...  

Abstract. Continuous vertically resolved monitoring of marine aerosol, Saharan dust, and marine/dust aerosol mixtures was performed with multiwavelength polarization/Raman lidar aboard the German research vessel R/V Meteor during a one-month transatlantic cruise from Guadeloupe to Cabo Verde over 4500 km (from 61.5° W to 2&amp;deg W, mostly along 14.5° N) in April–May 2013, as part of SALTRACE (Saharan Aerosol Long-range Transport and Aerosol–Cloud Interaction Experiment). An overview of measured aerosol optical properties over the tropical Atlantic is given in terms of spectrally resolved particle backscatter and extinction coefficients, lidar ratio, and linear depolarization ratio. Height profiles from the marine boundary layer (MBL) up to the top of the Saharan Air Layer (SAL) are presented. MBL and SAL mean lidar ratios were around 20 and 40 sr. These values indicate clean marine conditions in the MBL and entrainment of marine particles into the lower part of the SAL. In the central and upper parts of the SAL, the lidar ratios were most frequently 50–60 sr and thus typical for Saharan dust. The MBL and SAL mean depolarization ratios were close to 0.05 and between 0.2–0.3, respectively, which reflects almost dust-free conditions in the MBL and the occurrence of a mixture of marine and dust particles in the SAL. The conceptual model, describing the long-range transport and removal processes of Saharan dust over the North Atlantic, is discussed and confronted with the lidar observations along the west-to-east track of the slowly moving research vessel. The role of turbulent downward mixing as an efficient dust removal process is illuminated. In a follow-up article (Rittmeister et al., 2017), the lidar observations of dust extinction coefficient and derived mass concentration profiles are compared with respective dust profiles simulated with three well-established European atmospheric aerosol and dust prediction models (MACC, NMMB/BSC-Dust, SKIRON).


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