Cluster analysis: A technique for estimating the synoptic meteorological controls on air and precipitation chemistry—Method and applications

Dorling, Stephen; Davies, Trevor; Pierce, C.E.

doi:10.1016/0960-1686(92)90110-7

Cited by 289 publications

(177 citation statements)

References 17 publications

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“…This technique has been previously applied to air quality studies to investigate source origins of air pollutants (e.g. Slanina et al, 1983;Dorling et al, 1992;Tong et al, 2005;Van Curen, et al, 2002). As discussed earlier, dust episodes are usually extraordinary events with large perturbations in both aerosol concentrations and chemical composition compared to those during non-dusty periods.…”

Section: Approach To Identify Local Dust Recordsmentioning

confidence: 99%

Long-term dust climatology in the western United States reconstructed from routine aerosol ground monitoring

Tong

Wang

et al. 2012

Atmos. Chem. Phys.

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Abstract. This study introduces an observation-based dust identification approach and applies it to reconstruct longterm dust climatology in the western United States. Longterm dust climatology is important for quantifying the effects of atmospheric aerosols on regional and global climate. Although many routine aerosol monitoring networks exist, it is often difficult to obtain dust records from these networks, because these monitors are either deployed far away from dust active regions (most likely collocated with dense population) or contaminated by anthropogenic sources and other natural sources, such as wildfires and vegetation detritus. Here we propose an approach to identify local dust events relying solely on aerosol mass and composition from general-purpose aerosol measurements. Through analyzing the chemical and physical characteristics of aerosol observations during satellite-detected dust episodes, we select five indicators to be used to identify local dust records: (1) high PM 10 concentrations; (2) low PM 2.5 /PM 10 ratio; (3) higher concentrations and percentage of crustal elements; (4) lower percentage of anthropogenic pollutants; and (5) low enrichment factors of anthropogenic elements. After establishing these identification criteria, we conduct hierarchical cluster analysis for all validated aerosol measurement data over 68 IMPROVE sites in the western United States. A total of 182 local dust events were identified over 30 of the 68 locations from 2000 to 2007. These locations are either close to the four US Deserts, namely the Great Basin Desert, the Mojave Desert, the Sonoran Desert, and the Chihuahuan Desert, or in the high wind power region (Colorado). During the eight-year study period, the total number of dust events displays an interesting four-year activity cycle (one in 2000- The monthly frequency of dust events shows a peak from March to July and a second peak in autumn from September to November. The large quantity of dust events occurring in summertime also suggests the prevailing impact of windblown dust across the year. This seasonal variation is consistent with previous model simulations over the United States.

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Section: Approach To Identify Local Dust Recordsmentioning

confidence: 99%

Long-term dust climatology in the western United States reconstructed from routine aerosol ground monitoring

Tong

Wang

et al. 2012

Atmos. Chem. Phys.

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“…Three-day back trajectories (every six hours) created by the Canadian Meteorological Centre for the period of 2001-2005 were run through a K-means clustering technique for each site. They were organized into six common clusters based on the commonality of Euclidian distance from trajectory to trajectory (Dorling, 1992). Figure 2 shows the six clusters at the eight sites where the fourteen campaigns were conducted.…”

Section: Back Trajectory Cluster Analysismentioning

confidence: 99%

Characterization of the size-segregated water-soluble inorganic ions at eight Canadian rural sites

et al. 2008

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Abstract. Size-segregated water-soluble inorganic ions, including particulate sulphate (SO 2− 4 ), nitrate (NO − 3 ), ammonium (NH + 4 ), chloride (Cl − ), and base cations (K + , Na + , Mg 2+ , Ca 2+ ), were measured using a Micro-Orifice Uniform Deposit Impactor (MOUDI) during fourteen short-term field campaigns at eight locations in both polluted and remote regions of eastern and central Canada. The size distributions of SO 2− 4 and NH + 4 were unimodal, peaking at 0.3-0.6 µm in diameter, during most of the campaigns, although a bimodal distribution was found during one campaign and a trimodal distribution was found during another campaign made at a coastal site. SO 2− 4 peaked at slightly larger sizes in the cold seasons (0.5-0.6 µm) compared to the hot seasons (0.3-0.4 µm) due to the higher relative humidity in the cold seasons. The size distributions of NO − 3 were unimodal, peaking at 4.0-7.0 µm during the warm-season campaigns, and bimodal, with one peak at 0.3-0.6 µm and another at 4-7 µm during the cold-season campaigns. A unimodal size distribution, peaking at 4-6 µm, was found for Cl − , Na + , Mg 2+ , and Ca 2+ during approximately half of the campaigns and a bimodal distribution, with one peak at 2 µm and the other at 6 µm, was found during the rest of the campaigns. For K + , a bimodal distribution, with one peak at 0.3 µm and the other at 4 µm, was observed during most of the campaigns. Seasonal contrasts in the size-distribution profiles suggest that emission sources and air mass origins were the major factors controlling the size distributions of the primary aerosols while meteorological conditions were more important for the secondary aerosols.The dependence of the particle acidity on the particle size from the nucleation mode to the accumulation mode was not consistent from site to site or from season to season. Particles in the accumulation mode were more acidic than those in the Correspondence to: L. Zhang (leiming.zhang@ec.gc.ca) nucleation mode when submicron particles were in the state of strong acidity; however, when submicron particles were neutral or weakly acidic, particles in the nucleation mode could sometimes be more acidic. The inconsistency of the dependence of the particle acidity on the particle size should have been caused by the different emission sources of all the related species and the different meteorological conditions during the different campaigns. The results presented here at least partially explain the controversial phenomenon found in previous studies on this topic.

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“…To capture systematically the main synopticscale flows occurring at the measurement site, non hierarchical cluster analysis (DORLING et al, 1992) was applied to the HYSPLIT back-trajectory ensembles. To retrieve the largest amount of information, the clustering was applied to all single elements of the back-trajectory ensembles.…”

Section: Analysis Of Surface O 3 As a Function Of Back-trajectory Clumentioning

confidence: 99%

Analysis of Summer Ozone Observations at a High Mountain Site in Central Italy (Campo Imperatore, 2388 m a.s.l.)

Cristofanelli

Carlo

D‧Altorio

et al. 2013

Pure Appl. Geophys.

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Abstract-Tropospheric ozone (O 3 ) is an important atmospheric pollutant and climate forcer. The Mediterranean basin is a hot-spot region in terms of short-term O 3 distribution, with frequent episodes of high tropospheric O 3 , especially during summer. To improve the characterisation of summer O 3 variability in the Mediterranean area, during the period 6-27 August 2009 an experimental campaign was conducted at Campo Imperatore, Mt Portella (CMP), a high mountain site (2,388 m a.s.l.) located in the central Italian Apennines. As deduced from analysis of atmospheric circulation, the measurement site was significantly affected by air masses originating over the Mediterranean basin, which affected the measurement site for 32 % of the time. Analysis of average values and diurnal and day-to-day variability revealed that CMP O 3 observations (average value 60.0 ± 5.1 ppbv) were comparable with measurements at other European mountain stations, indicating a prevalent effect of meteorological conditions and atmospheric transport on the synoptic scale. In fact, only a small ''reverse'' diurnal variation typically characterises diurnal O 3 variability because of local thermal wind circulation, which sporadically favours transport of air masses rich in O 3 from the foothill regions. Statistical analysis of five-day back-trajectory ensembles indicates that synoptic-scale air-mass transport from the Mediterranean Sea usually results in decreasing O 3 concentrations at CMP, whereas the highest hourly O 3 values are mostly associated with air masses from central continental Europe, eastern Europe, and northern Italy. High O 3 concentrations are also related to downward air-mass transport from higher altitudes. Comparison of in-situ O 3 variability with tropospheric O 3 satellite-based measurements reveals similar features of the two data sets. Together with the results from back-trajectory analysis, this indicates that CMP measurements might usefully improve characterisation of broad-scale O 3 variability over the central Mediterranean basin.

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Cluster analysis: A technique for estimating the synoptic meteorological controls on air and precipitation chemistry—Method and applications

Cited by 289 publications

References 17 publications

Long-term dust climatology in the western United States reconstructed from routine aerosol ground monitoring

Long-term dust climatology in the western United States reconstructed from routine aerosol ground monitoring

Characterization of the size-segregated water-soluble inorganic ions at eight Canadian rural sites

Analysis of Summer Ozone Observations at a High Mountain Site in Central Italy (Campo Imperatore, 2388 m a.s.l.)

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