scholarly journals Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites

2008 ◽  
Vol 8 (4) ◽  
pp. 12625-12663 ◽  
Author(s):  
N. A. Marley ◽  
J. S. Gaffney ◽  
T. Castro ◽  
A. Salcido ◽  
J. Frederick
Keyword(s):  
Mexico City ◽  
Diffuse Radiation ◽  
Ground Level ◽  
Forward Direction ◽  
Single Scattering ◽  
Field Campaign ◽  
Clear Sky ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
Solar Noon

Abstract. Measurements of aerosol absorption and scattering were obtained in Mexico City during the MILAGRO (Megacity Initiative: Local and Global Research Observations) field campaign in March 2006. A comparison of aerosol absorption and scattering was obtained in Mexico City at site T0 located in the northern part of Mexico City at the Instituto Mexicano del Petróleo Laboratories and at site T1 located at the Universidad Tecnológica de Tecamac, 18 miles northwest of T0. Hourly averages of aerosol absorption were similar at both sites, ranging from 6–93 Mm−1 with an average of 31 Mm−1 at T0; and from 2–104 Mm−1 with an average of 19 Mm−1 at T1. Aerosol scattering at T0 ranged from 16–344 Mm−1 with an average of 105 Mm−1; while the scattering values at T1 were lower than T0 ranging from 2–136 with an average of 53 Mm−1. Aerosol single scattering albedos (SSAs) were determined at both sites using these data. SSAs at T1 ranged from 0.44–0.90 with an average 0.75 as compared to hose at T0, range 0.51–0.93 with an average of 0.77. Broadband UV-B intensity was found to be higher at site T0, with an average of 64 μW/cm2 at solar noon, than at site T1, which had an average of 54 μW/cm2 at solar noon. Comparisons of clear-sky modeled UV-B intensities with the simultaneous UV-B measurements obtained at site T0 and at site T1 for cloudless days indicate a larger diffuse radiation field at site T0 than at site T1. The determination of aerosol scattering Ångstrom coefficient at T0 suggests the larger diffuse radiation is due to the predominance of submicron aerosols at T0 with aerosol scattering of UV-B radiation peaked in the forward direction, leading to the enhancement observed at ground level.

scholarly journals Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites

2009 ◽  
Vol 9 (1) ◽  
pp. 189-206 ◽  
Author(s):  
N. A. Marley ◽  
J. S. Gaffney ◽  
T. Castro ◽  
A. Salcido ◽  
J. Frederick
Keyword(s):  
Radiation Field ◽  
Mexico City ◽  
Diffuse Radiation ◽  
Uvb Radiation ◽  
Field Campaign ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
Fine Mode ◽  
Solar Noon ◽  
A Site

Abstract. In March 2006, a multiagency field campaign was undertaken in Mexico City called the Megacities Initiative: Local and Global Research Observations (MILAGRO). Two of the five field components of the MILAGRO study focused a major part of their efforts on atmospheric particulate emissions from the Mexico City basin and their effects on radiative balance as a function of time, location and processing conditions. As part of these two MILAGRO components, measurements of aerosol optical properties were obtained at a site located in the northern part of Mexico City (T0) and also at a site located 29 km northwest (T1) to estimate the regional effects of aerosol emissions from the basin. Measurements of aerosol absorption and scattering for fine mode aerosols were obtained at both sites. Aerosol absorption at 550 nm was similar at both sites, ranging from 7–107 Mm−1 at T0 and from 3–147 Mm−1 at T1. Aerosol scattering measured at 550 nm at T0 ranged from 16–344 Mm−1 while the aerosol scattering values at T1 were much lower than at T0 ranging from 2–136 Mm−1. Aerosol single scattering albedos (SSAs) were calculated at 550 nm for the fine mode aerosols at both sites using these data. The SSAs at T0 ranged from 0.47–0.92 while SSAs at T1 ranged from 0.35–0.86. The presence of these highly absorbing fine aerosols in the lower atmosphere of the Mexico City area will result in a positive climate forcing and a local warming of the boundary layer in the region. Broadband UVB intensity was found to be higher at site T0, with an average of 64 μW/cm2 at solar noon, than at site T1, which had an average of 54 μW/cm2 at solar noon. Comparisons of clear-sky modeled UVB intensities with the simultaneous UVB measurements obtained at sites T0 and T1 for cloudless days indicate a larger diffuse radiation field at site T0 than at site T1. The determination of aerosol Ångstrom scattering coefficients at T0 suggests that this is due to the predominance of aerosols in the size range of 0.3 micron, which leads to scattering of UVB radiation peaked in the forward direction and to an enhanced UVB radiation observed at ground level. This enhancement of the UVB diffuse radiation field would explain the enhanced photochemistry observed in the Mexico City area despite the reduction in UVB anticipated from light absorbing species.

scholarly journals Vertical profiles of sub-micron aerosol single scattering albedo over Indian region immediately before monsoon onset and during its development: Research from the SWAAMI field campaign

2019 ◽  
Author(s):  
Mohanan R. Manoj ◽  
Sreedharan K. Satheesh ◽  
Krishnaswamy K. Moorthy ◽  
Hugh Coe
Keyword(s):  
Active Phase ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Development Research ◽  
Aerosol Absorption ◽  
South West ◽  
Aerosol Scattering ◽  
First Time ◽  
Geographical Locations

Abstract. Vertical structures of aerosol single scattering albedo (SSA), from near the surface through the free troposphere, have been estimated for the first time at distinct geographical locations over the Indian mainland and adjoining oceans, using in-situ measurements of aerosol scattering and absorption coefficients aboard the FAAM BAe-146 aircraft during the South West Asian Aerosol Monsoon Interactions (SWAAMI) campaign from June to July 2016. These are used to examine the spatial variation of SSA profiles and also to characterize its transformation from just prior to the onset of Indian Summer Monsoon (June 2016) to its active phase (July 2016). Very strong aerosol absorption, with SSA values as low as 0.7, persisted in the lower altitudes (

scholarly journals Seasonal differences in the vertical profiles of aerosol optical properties over rural Oklahoma

2011 ◽  
Vol 11 (4) ◽  
pp. 11939-11957 ◽  
Author(s):  
E. Andrews ◽  
P. J. Sheridan ◽  
J. A. Ogren
Keyword(s):  
Seasonal Variability ◽  
Seasonal Cycle ◽  
Gulf Coast ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Vertical Profiles ◽  
Seasonal Differences ◽  
Aerosol Loading ◽  
Aerosol Absorption ◽  
Aerosol Scattering

Abstract. A small airplane made more than 450 aerosol optical property (light absorption and light scattering) vertical profile measurements (up to 4 km) over a rural Oklahoma site between March 2000 and July 2005. These profiles suggest significant seasonal differences in aerosol properties. The highest amounts of scattering and absorbing aerosol are observed during the summer, while the relative contribution of aerosol absorption is highest in the winter (i.e., single scattering albedo is lowest in winter). Aerosol absorption generally decreased with altitude below ∼1.5 km and then was relatively constant above that. Aerosol scattering decreased sharply with altitude below ∼1.5 km but, unlike absorption, also decreased at higher altitudes, albeit less sharply. The seasonal variability observed for aerosol loading is consistent with other aerosol measurements in the region including AERONET aerosol optical depth (AOD), CALIPSO vertical profiles, and IMPROVE aerosol mass. The column averaged single scattering albedo derived from in situ airplane measurements shows a similar seasonal cycle as the AERONET single scattering albedo inversion product, but a comparison of aerosol asymmetry parameter from airplane and AERONET platforms suggests differences in seasonal variability. The observed seasonal cycle of aerosol loading corresponds with changes in air mass back trajectories: the aerosol scattering was higher when transport was from polluted areas (e.g., the Gulf Coast) and lower when the air came from cleaner regions and/or the upper atmosphere.

scholarly journals Seasonal differences in the vertical profiles of aerosol optical properties over rural Oklahoma

2011 ◽  
Vol 11 (20) ◽  
pp. 10661-10676 ◽  
Author(s):  
E. Andrews ◽  
P. J. Sheridan ◽  
J. A. Ogren
Keyword(s):  
Seasonal Variability ◽  
Gulf Coast ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Ambient Conditions ◽  
Seasonal Differences ◽  
Aerosol Loading ◽  
Aerosol Absorption ◽  
Aerosol Scattering

Abstract. A small airplane made 597 aerosol optical property (light absorption and light scattering) vertical profile measurements over a rural Oklahoma site between March 2000 and December 2007. The aerosol profiles obtained during these 8 yr of measurements suggest significant seasonal differences in aerosol loading (scattering and absorption). The highest amounts of scattering and absorbing aerosol are observed during the summer and the lowest loading occurs during the winter. The relative contribution of aerosol absorption is highest in the winter (i.e., single scattering albedo is lowest in winter), particularly aloft. Aerosol absorption generally decreased with altitude below ~1.5 km and then was relatively constant or decreased more gradually above that. Aerosol scattering decreased sharply with altitude below ~1.5 km but, unlike absorption, also decreased at higher altitudes, albeit less sharply. Scattering Ångström exponents suggest that the aerosol was dominated by sub-micron aerosol during the summer at all altitudes, but that larger particles were present, especially in the spring and winter above 1 km. The seasonal variability observed for aerosol loading is consistent with AERONET aerosol optical depth (AOD) although the AOD values calculated from in situ adjusted to ambient conditions and matching wavelengths are up to a factor of two lower than AERONET AOD values depending on season. The column averaged single scattering albedo derived from in situ airplane measurements are similar in value to the AERONET single scattering albedo inversion product but the seasonal patterns are different – possibly a consequence of the strict constraints on obtaining single scattering albedo from AERONET data. A comparison of extinction Ångström exponent and asymmetry parameter from the airplane and AERONET platforms suggests similar seasonal variability with smaller particles observed in the summer and fall and larger particles observed in spring and winter. The observed seasonal cycle of aerosol loading corresponds with changes in air mass back trajectories: the aerosol scattering was higher when transport was from polluted areas (e.g., the Gulf Coast) and lower when the air came from cleaner regions and/or the upper atmosphere.

scholarly journals Long term trends in aerosol optical characteristics in the Po Valley (IT)

2014 ◽  
Vol 14 (7) ◽  
pp. 9041-9065
Author(s):  
J. P. Putaud ◽  
F. Cavalli ◽  
S. Martins dos Santos ◽  
A. Dell'Acqua
Keyword(s):  
Radiative Forcing ◽  
Mass Concentration ◽  
Measurement Data ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Po Valley ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
The One

Abstract. Aerosols properties have been monitored by ground-based in situ and remote sensing measurements at the station for atmospheric research located in Ispra on the edge of the Po Valley for almost one decade. In-situ measurements are performed according to Global Atmosphere Watch recommendations, and quality is assured through the participation in regular inter-laboratory comparisons. Sunphotometer data are produced by AERONET. Data show significant decreasing trends over 2004–2010 for a number of variables including particulate matter (PM) mass concentration, aerosol scattering, backscattering and absorption coefficients, and aerosol optical thickness (AOT). In-situ measurement data show no significant trend in the aerosol backscatter ratio, but a significant decreasing trend of about −0.7 ± 0.3% in the aerosol single scattering albedo in the visible light range. Similar trends are observed in the aerosol single scattering albedo retrieved from sunphotometer measurements. Correlations appear between in situ PM mass concentration and aerosol scattering coefficient on the one hand, and elemental carbon (EC) and aerosol absorption coefficient on the other hand, however, no increase in the EC / PM ratio was observed, which could have explained the decrease in SSA. The application of a simple approximation to calculate the direct radiative forcing by aerosols suggests a significant diminution in their cooling effect, mainly due to the decrease in AOT. Applying the methodology we present to those sites where the necessary suite of measurements is available would provide important information to inform future policies for air quality enhancement and fast climate change mitigation.

scholarly journals Aerosol spectral absorption in the Mexico City area: results from airborne measurements during MILAGRO/INTEX B

2010 ◽  
Vol 10 (13) ◽  
pp. 6333-6343 ◽  
Author(s):  
R. W. Bergstrom ◽  
K. S. Schmidt ◽  
O. Coddington ◽  
P. Pilewskie ◽  
H. Guan ◽  
...  
Keyword(s):  
Optical Properties ◽  
Gulf Of Mexico ◽  
Mexico City ◽  
Optical Depth ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Gas Absorption ◽  
Aerosol Optical Properties ◽  
City Area ◽  
Aerosol Absorption

Abstract. This paper presents estimates of the spectral solar absorption due to atmospheric aerosols during the 2006 MILAGRO/INTEX-B (Megacity Initiative-Local And Global Research Observations/Phase B of the Intercontinental Chemical Transport Experiment) field campaign. The aerosol absorption was derived from measurements of the spectral solar radiation and the spectral aerosol optical depth made on the J31 aircraft flying over the Gulf of Mexico and over Mexico City. We present the spectral single scattering albedo (SSA) and aerosol absorption optical depth (AAOD) for two flights over the Gulf of Mexico and three flights over Mexico City for wavelengths from 350 to approximately 1650 nm. The spectral aerosol optical properties of each case are different and illustrate the variability of the aerosol optical properties in the Mexico City area. The results can be described in terms of three different wavelength regions: The 350–500 nm region where the aerosol absorption often falls off sharply presumably due to organic carbonaceous particles and windblown dust; the 500–1000 nm region where the decrease with wavelength is slower presumably due to black carbon; and the near infrared spectral region (1000 nm to 1650 nm) where it is difficult to obtain reliable results since the aerosol absorption is relatively small and the gas absorption dominates. However, there is an indication of a small and somewhat wavelength independent absorption in the region beyond 1000 nm. For one of the flights over the Gulf of Mexico near the coastline it appears that a cloud/fog formation and evaporation led to an increase of absorption possibly due to a water shell remaining on the particles after the cloud/fog had dissipated. For two of the Mexico City cases, the single scattering albedo is roughly constant between 350–500 nm consistent with other Mexico City results. In three of the cases a single absorption Angstrom exponent (AAE) fits the aerosol absorption optical depth over the entire wavelength range of 350 to 1650 nm relatively well (r2> 0.86).

scholarly journals Aerosol absorption measurements and retrievals in shadow2 campaign

2018 ◽  
Vol 176 ◽  
pp. 10003
Author(s):  
Qiaoyun Hu ◽  
Philippe Goloub ◽  
Thierry Podvin ◽  
Igor Veselovskiy ◽  
Anton Lopatin ◽  
...  
Keyword(s):  
West Africa ◽  
Ground Level ◽  
Absorption Profile ◽  
Field Campaign ◽  
Microphysical Properties ◽  
Aerosol Absorption ◽  
Dust Absorption ◽  
Absorption Measurements

Dust, maritime and dust-smoke mixture events observed during SHADOW2 (SaHAran Dust Over West Africa) field campaign are selected and analyzed by using Raman and GARRLiC retrievals. The derived aerosol optical and microphysical properties will be shown. Dust absorption profile and on ground level are derived from GARRLiC retrievals and Aethalometer measurements, respectively. Our results provide a closer insight about dust absorbing properties.

scholarly journals Long-term trends in aerosol optical characteristics in the Po Valley, Italy

2014 ◽  
Vol 14 (17) ◽  
pp. 9129-9136 ◽  
Author(s):  
J. P. Putaud ◽  
F. Cavalli ◽  
S. Martins dos Santos ◽  
A. Dell'Acqua
Keyword(s):  
Radiative Forcing ◽  
Mass Concentration ◽  
Measurement Data ◽  
Single Scattering ◽  
Po Valley ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
Sun Photometer ◽  
The One

Abstract. Aerosol properties have been monitored by ground-based in situ and remote sensing measurements at the station for atmospheric research located in Ispra, on the edge of the Po Valley, for almost one decade. In situ measurements are performed according to Global Atmosphere Watch recommendations, and quality is assured through the participation in regular inter-laboratory comparisons. Sun-photometer data are produced by the Aerosol Robotic Network (AERONET). Data show significant decreasing trends over the 2004–2010 period for a number of variables, including particulate matter (PM) mass concentration, aerosol scattering, backscattering and absorption coefficients, and aerosol optical thickness (AOT). In situ measurement data show no significant trends in the aerosol backscatter ratio, but they do show a significant decreasing trend of about −0.7 ± 0.3% yr−1 in the aerosol single scattering albedo (SSA) in the visible light range. Similar trends are observed in the SSA retrieved from sun-photometer measurements. Correlations appear between in situ PM mass concentration and aerosol scattering coefficient, on the one hand, and elemental carbon (EC) concentration and aerosol absorption coefficient, on the other hand. However, no increase in the EC / PM ratio was observed, which could have explained the decrease in SSA. The application of a simple approximation to calculate the direct radiative forcing by aerosols suggests a significant diminution in their cooling effect, mainly due to the decrease in AOT. Applying the methodology we present to those sites, where the necessary suite of measurements is available, would provide important information to inform future policies for air-quality enhancement and fast climate change mitigation.

scholarly journals Transmissivity of solar radiation within a <i>Picea sitchensis</i> stand under various sky conditions

2015 ◽  
Vol 12 (14) ◽  
pp. 4195-4207 ◽  
Author(s):  
S. Dengel ◽  
J. Grace ◽  
A. MacArthur
Keyword(s):  
Management Practice ◽  
Diffuse Radiation ◽  
Picea Sitchensis ◽  
Vertical Profiles ◽  
Area Index ◽  
Clear Sky ◽  
Forestry Management ◽  
Solar Noon ◽  
Sky Conditions ◽  
Horizontal Pattern

Abstract. We tested the hypothesis that diffuse radiation from cloudy and overcast skies penetrates the canopy more effectively than direct radiation from clear skies. We compared the flux density and spectral properties of direct and diffuse radiation (around solar noon (±1 h)) above, within and below a forest stand under sunny, cloudy and overcast conditions in a thinned Sitka spruce (Picea sitchensis (Bong.) Carr.) forest (28 years old, with a leaf area index of approximately 5.2 m2 m−2). We recorded vertical profiles of radiation penetration (from 350 to 1050 nm), and we also explored the horizontal pattern of radiation along a 115 m transect. We showed that in "clear sky" conditions, the photosynthetically active radiation in the lower parts of the canopy was substantially attenuated, more so than under cloudy and overcast skies. It was particularly depleted in the blue part of the spectrum, but only slightly blue-depleted when the sky was overcast or cloudy. Moreover, the red : far-red ratio under clear skies fell to values less than 0.3 but only to 0.6 under cloudy or overcast skies. Near the ground, the light climate was strongly influenced by the thinning pattern (carried out in accordance with standard forestry management practice).

scholarly journals Variability of aerosol optical properties in the Western Mediterranean Basin

2011 ◽  
Vol 11 (5) ◽  
pp. 14091-14125
Author(s):  
M. Pandolfi ◽  
M. Cusack ◽  
A. Alastuey ◽  
X. Querol
Keyword(s):  
Optical Properties ◽  
Sea Breeze ◽  
Single Scattering ◽  
Western Mediterranean ◽  
Aerosol Optical Properties ◽  
Air Masses ◽  
Aerosol Absorption ◽  
Western Mediterranean Basin ◽  
Aerosol Scattering ◽  
The Mean

Abstract. Aerosol light scattering, black carbon (BC) and particulate matter (PM) concentrations were measured at Montseny, a regional background site in the Western Mediterranean Basin (WMB) which is part of the European Supersite for Atmospheric Aerosol Research (EUSAAR). Off line analyses of 24 h PM filters collected with Hi-Vol instruments were performed for the determination of the main chemical components of PM. Measurements of BC were used to calculate the light absorption properties of atmospheric particles. Single Scattering Albedo (SSA) at 635 nm was estimated starting from aerosol scattering and absorption measurements, while Ångström exponents were calculated by means of the three wavelengths (450 nm, 525 nm, 635 nm) aerosol light scattering measurements from Nephelometer. Mean scattering and hemispheric backscattering coefficients (@ 635 nm) were 26.8 ± 23.3 Mm−1 and 4.3 ± 2.7 Mm−1, respectively and the mean aerosol absorption coefficient was 2.8 ± 2.2 Mm−1. Mean values of Single Scattering Albedo (SSA) and Ångström exponent (calculated from 450 nm to 635 nm) at MSY were 0.90 ± 0.05 and 1.2 ± 0.6, respectively. A clear relationship was observed between the PM1/PM10 and PM2.5/PM10 ratios as a function of the calculated Ångström exponents. Mass scattering cross sections for fine mass and sulfate at 635 nm were calculated in 2.8 ± 0.5 m2 g−1 and 11.8 ± 2.2 m2 g−1 respectively, while the mean aerosol absorption cross section was estimated around 10.4 ± 2.0 m2 g−1. The variability in aerosol optical properties in the WMB were largely explained by the origin and ageing of air masses over the measurement site. The sea breeze played an important role in transporting pollutants from the developed WMB coastlines towards inland rural areas, changing the optical properties of aerosols. Aerosol scattering and backscattering coefficients increased by around 40 % in the afternoon when the sea breeze was fully developed while the absorption coefficient increased by more than 100 % as a consequence of the increase in BC concentration at MSY observed under sea breeze circulation. The analysis of the Ångström (Å) exponent as a function of the origin the air masses revealed that polluted winter anticyclonic conditions and summer recirculation scenarios typical of the WMB led to an increase of fine particles in the atmosphere (Å = 1.4 ± 0.1) while the aerosol optical properties under Atlantic Advection episodes and Saharan dust outbreaks were clearly dominated by coarser particles (Å = 0.7 ± 0.3).

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