scholarly journals Ambient aerosol properties in the remote atmosphere from global-scale in situ measurements

2021 ◽  
Vol 21 (19) ◽  
pp. 15023-15063
Author(s):  
Charles A. Brock ◽  
Karl D. Froyd ◽  
Maximilian Dollner ◽  
Christina J. Williamson ◽  
Gregory Schill ◽  
...  
Keyword(s):  
Optical Properties ◽  
Global Scale ◽  
In Situ Measurements ◽  
Sea Salt ◽  
Size Distributions ◽  
Global Models ◽  
Air Masses ◽  
Aerosol Types ◽  
Aerosol Properties

Abstract. In situ measurements of aerosol microphysical, chemical, and optical properties were made during global-scale flights from 2016–2018 as part of the Atmospheric Tomography Mission (ATom). The NASA DC-8 aircraft flew from ∼ 84∘ N to ∼ 86∘ S latitude over the Pacific, Atlantic, Arctic, and Southern oceans while profiling nearly continuously between altitudes of ∼ 160 m and ∼ 12 km. These global circuits were made once each season. Particle size distributions measured in the aircraft cabin at dry conditions and with an underwing probe at ambient conditions were combined with bulk and single-particle composition observations and measurements of water vapor, pressure, and temperature to estimate aerosol hygroscopicity and hygroscopic growth factors and calculate size distributions at ambient relative humidity. These reconstructed, composition-resolved ambient size distributions were used to estimate intensive and extensive aerosol properties, including single-scatter albedo, the asymmetry parameter, extinction, absorption, Ångström exponents, and aerosol optical depth (AOD) at several wavelengths, as well as cloud condensation nuclei (CCN) concentrations at fixed supersaturations and lognormal fits to four modes. Dry extinction and absorption were compared with direct in situ measurements, and AOD derived from the extinction profiles was compared with remotely sensed AOD measurements from the ground-based Aerosol Robotic Network (AERONET); this comparison showed no substantial bias. The purpose of this work is to describe the methodology by which ambient aerosol properties are estimated from the in situ measurements, provide statistical descriptions of the aerosol characteristics of different remote air mass types, examine the contributions to AOD from different aerosol types in different air masses, and provide an entry point to the ATom aerosol database. The contributions of different aerosol types (dust, sea salt, biomass burning, etc.) to AOD generally align with expectations based on location of the profiles relative to continental sources of aerosols, with sea salt and aerosol water dominating the column extinction in most remote environments and dust and biomass burning (BB) particles contributing substantially to AOD, especially downwind of the African continent. Contributions of dust and BB aerosols to AOD were also significant in the free troposphere over the North Pacific. Comparisons of lognormally fitted size distribution parameters to values in the Optical Properties of Aerosols and Clouds (OPAC) database commonly used in global models show significant differences in the mean diameters and standard deviations for accumulation-mode particles and coarse-mode dust. In contrast, comparisons of lognormal parameters derived from the ATom data with previously published shipborne measurements in the remote marine boundary layer show general agreement. The dataset resulting from this work can be used to improve global-scale representation of climate-relevant aerosol properties in remote air masses through comparison with output from global models and assumptions used in retrievals of aerosol properties from both ground-based and satellite remote sensing.

scholarly journals Ambient aerosol properties in the remote atmosphere from global-scale in-situ measurements

2021 ◽  
Author(s):  
Charles A. Brock ◽  
Karl D. Froyd ◽  
Maximilian Dollner ◽  
Christina J. Williamson ◽  
Gregory Schill ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Global Scale ◽  
In Situ Measurements ◽  
Sea Salt ◽  
Size Distributions ◽  
Global Models ◽  
Air Masses ◽  
Aerosol Types ◽  
Aerosol Properties

Abstract. In situ measurements of aerosol microphysical, chemical, and optical properties were made during global-scale flights from 2016–2018 as part of the Atmospheric Tomography Mission (ATom). A NASA DC-8 aircraft flew from ~84 °N to ~86 °S latitude over the Pacific, Atlantic, Arctic, and Southern oceans while profiling nearly continuously between altitudes of ~160 m and ~12 km. These global circuits were made once each season. Particle size distributions measured in the aircraft cabin at dry conditions and with an underwing probe at ambient conditions were combined with bulk and single-particle composition observations and measurements of water vapor, pressure and temperature to estimate aerosol hygroscopicity and hygroscopic growth factors and calculate size distributions at ambient relative humidity. These reconstructed, composition-resolved ambient size distributions were used to estimate intensive and extensive aerosol properties, including single scatter albedo, asymmetry parameter, extinction, absorption, Ångström exponents, and aerosol optical depth (AOD) at several wavelengths, as well as CCN concentrations at fixed supersaturations and lognormal fits to four modes. Dry extinction and absorption were compared with direct, in situ measurements, and AOD derived from the extinction profiles was compared with remotely sensed AOD measurements from the ground-based Aerosol Robotic Network (AERONET); these calculated parameters were in agreement with the direct observations within expected uncertainties. The purpose of this work is to describe the methodology by which ambient aerosol properties are estimated from the in situ measurements, provide statistical descriptions of the aerosol characteristics of different remote air mass types, examine the contributions to AOD from different aerosol types in different air masses, and provide an entry point to the ATom aerosol database. The contributions of different aerosol types (dust, sea salt, biomass burning, etc.) to AOD generally align with expectations based on location of the profiles relative to continental sources of aerosols, with sea salt and aerosol water dominating the column extinction in most remote environments and dust and biomass burning (BB) particles contributing substantially to AOD, especially downwind of the African continent. Contributions of dust and BB aerosols to AOD were also significant in the free troposphere over the North Pacific. Comparisons of lognormally fitted size distribution parameters to values in a database commonly used in global models show significant differences in the mean diameters and standard deviations for accumulation-mode particles and coarse-mode dust. In contrast, comparisons of lognormal parameters derived from the ATom data with previously published ship-borne measurements in the remote marine boundary layer show general agreement. The dataset resulting from this work can be used to improve global-scale representation of climate-relevant aerosol properties in remote air masses through comparison with output from global models and with assumptions used in retrievals of aerosol properties from both ground-based and satellite remote sensing.

scholarly journals Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model

2011 ◽  
Vol 4 (4) ◽  
pp. 3623-3690 ◽  
Author(s):  
T. Bergman ◽  
V.-M. Kerminen ◽  
H. Korhonen ◽  
K. J. Lehtinen ◽  
R. Makkonen ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Scale ◽  
Good Choice ◽  
Sea Salt ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
Computationally Efficient ◽  
Model Studies ◽  
Aerosol Module ◽  
Aerosol Properties

Abstract. We present the implementation and evaluation of a sectional aerosol microphysics model SALSA within the aerosol-climate model ECHAM5-HAM. This aerosol microphysics module has been designed to be flexible and computationally efficient so that it can be implemented in regional or global scale models. The computational efficiency has been achieved by keeping the number of variables needed to describe the size and composition distribution to the minimum. The aerosol size distribution is described using 20 size sections with 10 size sections in size space which cover diameters ranging from 3 nm to 10 μm divided to three subranges each having distinct optimised process and compound selection. The ability of the module to describe the global aerosol properties was evaluated by comparison against (1) measured continental and marine size distributions, (2) observed variability of continental modal number concentrations, (3) measured sulphate, organic carbon, black carbon and sea salt mass concentrations, (4) observations of AOD and other aerosol optical properties from satellites and AERONET network, (5) global aerosol budgets and concentrations from previous model studies, and (6) model results using M7 which is the default aerosol microphysics module in ECHAM5-HAM. The evaluation shows that the global aerosol properties can be reproduced reasonably well using the coarse resolution of 10 size sections in size space. The simulated global aerosol budgets are within the range of previous studies. Surface concentrations of sea salt, sulphate and carbonaceous species have an annual mean within a factor of five of the observations, while the simulated sea salt concentrations reproduce the observations less accurately and show high variability. Regionally, AOD is in relatively good agreement with the observations (within a factor of two). At mid-latitudes the observed AOD is captured well, while at high-latitudes as well as in some polluted and dust regions the modeled AOD is significantly lower than the observed. Regarding the most investigated aerosol properties, the performances of SALSA and the modal aerosol module M7 against observations are comparable. However, SALSA reproduces the observed number concentrations and the size distributions of CCN sized particles much more accurately than M7, and is therefore a good choice for aerosol-cloud interaction studies in global models. Our study also shows that when including activation type nucleation process in the boundary layer, the modeled concentrations of particles under 50 nm in diameter are reproduced much better compared to when only binary nucleation is assumed.

scholarly journals In situ measurements of aerosols optical properties and number size distributions in a subarctic coastal region of Norway

2011 ◽  
Vol 11 (12) ◽  
pp. 32921-32964
Author(s):  
S. Mogo ◽  
V. E. Cachorro ◽  
J. F. Lopez ◽  
E. Montilla ◽  
B. Torres ◽  
...  
Keyword(s):  
Optical Properties ◽  
Single Scattering ◽  
Mean Value ◽  
The Arctic ◽  
Optical Parameters ◽  
Size Distributions ◽  
Air Mass ◽  
Air Masses ◽  
Particle Sizer

Abstract. In situ measurements of aerosol optical properties were made in the summer of 2008 at the ALOMAR station facility (69°16 N, 16°00 E), located at a rural site in the north of the island of Andøya (Vesterålen archipelago), approximately 300 km north of the Arctic Circle. The extended three-month campaign was part of the POLARCAT Project (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) of the International Polar Year (IPY-2007-2008). Its goal was to characterize the aerosols of this sub-Arctic area, which are frequently transported to the Arctic region. The ambient light-scattering coefficient, σs (550 nm), at ALOMAR had a measured hourly mean value of 5.41 Mm−1 (StD = 3.55 Mm−1), and the light-absorption coefficient, σa (550 nm), had a measured hourly mean value of 0.40 Mm−1 (StD = 0.27 Mm−1). The scattering/absorption Ångström exponents, αs,a, are used for a detailed analysis of the variations of the spectral shape of σs,a. Whereas αs demonstrates the presence of two particle sizes corresponding to two types of aerosols, the αa demonstrates only one type of absorbing aerosol particles. Values of αa above 1 were not observed. The single-scattering albedo, ω0, ranged from 0.62 to 0.99 (mean = 0.91, StD = 0.05), and the relationships of this property to the absorption/scattering coefficients and the Ångström exponents are presented. The concentration of the particles was monitored using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS) and an ultrafine condensation particle counter (UCPC). The shape of the median size distribution of the particles in the submicrometer fraction was bimodal, and the submicrometer, micrometer and total concentrations presented hourly mean values of 1277 cm3 (StD = 1563 cm3), 1 cm3 (StD = 1 cm3) and 2463 cm3 (StD = 4251 cm3), respectively. The modal correlations were investigated, and the concentration of particles sized between 30 and 100 nm (Aitken mode) are presented as a function of the concentration of the particles sized between 100 and 390 nm (accumulation mode). The optical and the microphysical parameters are related to each other, and the results are presented. The origins and pathways of air masses were examined by computing the back-trajectories in a trajectory model (HYSPLIT). Six geographical sectors were defined to classify the air masses, and, based on the sector classification, the linkage between the air mass origin and the optical parameters was established. Aerosol size distributions were also evaluated in relation to the air masses. The relationships between the air mass origins and other parameters, especially those related to the single scattering albedo, allow us to describe two characteristic situations: northern and western air masses, which had predominantly marine aerosols, presented lower optical parameter values, indicating predominantly coarser and non-absorbent particles; and eastern and southern air masses, in which continental aerosols were predominant, presented higher values for all optical parameters, indicating the presence of smaller absorbent particles.

scholarly journals Supplementary material to "Ambient aerosol properties in the remote atmosphere from global-scale in-situ measurements"

2021 ◽  
Author(s):  
Charles A. Brock ◽  
Karl D. Froyd ◽  
Maximilian Dollner ◽  
Christina J. Williamson ◽  
Gregory Schill ◽  
...  
Keyword(s):  
Global Scale ◽  
In Situ Measurements ◽  
Ambient Aerosol ◽  
Supplementary Material ◽  
Aerosol Properties

scholarly journals Synergetic monitoring of Saharan dust plumes and potential impact on surface: a case study of dust transport from Canary Islands to Iberian Peninsula

2011 ◽  
Vol 11 (7) ◽  
pp. 3067-3091 ◽  
Author(s):  
C. Córdoba-Jabonero ◽  
M. Sorribas ◽  
J. L. Guerrero-Rascado ◽  
J. A. Adame ◽  
Y. Hernández ◽  
...  
Keyword(s):  
Iberian Peninsula ◽  
Particle Deposition ◽  
Ground Level ◽  
In Situ Measurements ◽  
Saharan Dust ◽  
Dust Transport ◽  
Air Masses ◽  
Potential Impact

Abstract. The synergetic use of meteorological information, remote sensing both ground-based active (lidar) and passive (sun-photometry) techniques together with backtrajectory analysis and in-situ measurements is devoted to the characterization of dust intrusions. A case study of air masses advected from the Saharan region to the Canary Islands and the Iberian Peninsula, located relatively close and far away from the dust sources, respectively, was considered for this purpose. The observations were performed over three Spanish geographically strategic stations within the dust-influenced area along a common dust plume pathway monitored from 11 to 19 of March 2008. A 4-day long dust event (13–16 March) over the Santa Cruz de Tenerife Observatory (SCO), and a linked short 1-day dust episode (14 March) in the Southern Iberian Peninsula over the Atmospheric Sounding Station "El Arenosillo" (ARN) and the Granada station (GRA) were detected. Meteorological conditions favoured the dust plume transport over the area under study. Backtrajectory analysis clearly revealed the Saharan region as the source of the dust intrusion. Under the Saharan air masses influence, AERONET Aerosol Optical Depth at 500 nm (AOD500) ranged from 0.3 to 0.6 and Ångström Exponent at 440/675 nm wavelength pair (AE440/675) was lower than 0.5, indicating a high loading and predominance of coarse particles during those dusty events. Lidar observations characterized their vertical layering structure, identifying different aerosol contributions depending on altitude. In particular, the 3-km height dust layer transported from the Saharan region and observed over SCO site was later on detected at ARN and GRA stations. No significant differences were found in the lidar (extinction-to-backscatter) ratio (LR) estimation for that dust plume over all stations when a suitable aerosol scenario for lidar data retrieval is selected. Lidar-retrieved LR values of 60–70 sr were obtained during the main dust episodes. These similar LR values found in all the stations suggest that dust properties were kept nearly unchanged in the course of its medium-range transport. In addition, the potential impact on surface of that Saharan dust intrusion over the Iberian Peninsula was evaluated by means of ground-level in-situ measurements for particle deposition assessment together with backtrajectory analysis. However, no connection between those dust plumes and the particle sedimentation registered at ground level is found. Differences on particle deposition processes observed in both Southern Iberian Peninsula sites are due to the particular dust transport pattern occurred over each station. Discrepancies between columnar-integrated and ground-level in-situ measurements show a clear dependence on height of the dust particle size distribution. Then, further vertical size-resolved observations are needed for evaluation of the impact on surface of the Saharan dust arrival to the Iberian Peninsula.

Sign in / Sign up

Export Citation Format

Share Document