17- https://doi.org/10.1051/0004-6361/201732258
A NIKA view of two star-forming infrared dark clouds: Dust emissivity variations and mass concentration
Translate Article 
Context.The thermal emission of dust grains is a powerful tool for probing cold, dense regions of molecular gas in the interstellar medium, and so constraining dust properties is key to obtaining accurate measurements of dust mass and temperature.Aims.By placing constraints on the dust emissivity spectral index,β, towards two star-forming infrared dark clouds – SDC18.888–0.476 and SDC24.489–0.689 – we aim to evaluate the role of mass concentration in the associated star-formation activity.Methods.We exploited the simultaneous 1.2 and 2.0 mm imaging capability of the NIKA camera on the IRAM 30 m telescope to construct maps ofβfor both clouds, and by incorporatingHerschelobservations, we created H2column density maps with 13′′ angular resolution.Results.While we find no significant systematic radial variations around the most massive clumps in either cloud on ≳0.1 pc scales, their meanβvalues are significantly different, withβ̅ = 2.07 ± 0.09 (random) ± 0.25 (systematic) for SDC18.888–0.476 andβ̅ = 1.71 ± 0.09 (random) ± 0.25 (systematic) for SDC24.489–0.689. These differences could be a consequence of the very different environments in which both clouds lie, and we suggest that the proximity of SDC18.888–0.476 to the W39 HIIregion may raiseβon scales of ~1 pc. We also find that the mass in SDC24.489–0.689 is more centrally concentrated and circularly symmetric than in SDC18.888–0.476, and is consistent with a scenario in which spherical globally-collapsing clouds concentrate a higher fraction of their mass into a single core than elongated clouds that will more easily fragment, distributing their mass into many cores.Conclusions.We demonstrate thatβvariations towards interstellar clouds can be robustly constrained with high signal-to-noise ratio (S/N) NIKA observations, providing more accurate estimates of their masses. The methods presented here will be applied to the Galactic Star Formation with NIKA2 (GASTON) guaranteed time large programme, extending our analysis to a statistically significant sample of star-forming clouds.
- Research Article
- 10.5194/acp-26-1395-2026
- Jan 28, 2026
- Atmospheric Chemistry and Physics
Abstract. Dust activities across East Asia and North America have shown decadal variations, mediating radiation budget, air quality, and human health, especially during their peak months of April and May. Using satellite and ground measurements, as along with simulations from a dust emission model, we demonstrate an increase of 12.7 % and 23.4 % in April dust emissions across East Asia and North America, respectively, during the past four decades, in contrast to a 16.5 % and 2.5 % decrease during the last two decades. Meanwhile, both regions show a steady increase in May dust emissions by 5.7 % and 16.3 %, respectively, since the 1980s. Sensitivity experiments attribute both regions' decadal variations in dust emission primarily to surface wind speed changes; whereas vegetation exerts minimum influence on the regional dust emission variations. Furthermore, these decadal variations in dust initiating wind could largely be attributed to regime shifts in extratropical cyclone (EC), including their duration and intensity. Specifically, ECs are responsible for 60 %–70 % of the April–May total dust emissions in East Asia and 30 %–40 % of that in North America; meanwhile, ECs explain a larger portion of the decadal variations in April dust emission from East Asia (up to ∼80 %), compared with May and from North America. These results highlight the changing frequency and duration of strong winds, especially those associated with EC, and their role in shaping the decadal variations of mid-latitude dust emissions.
- Research Article
- 37
- 10.1051/0004-6361/201117956
- Jan 1, 2012
- Astronomy & Astrophysics
Past and recent observations have revealed unexpected variations in the FIR-mm dust emissivity. In the Herschel spectral range, those are often referred to as a 500{\mu}m emission excess. Several dust emission models have been developed to interpret astrophysical data in the FIR-mm domain. However, these are commonly unable to fully reconcile theoretical predictions with observations. In contrast, the recently revised two level system (TLS) model seems to provide a promising way of interpreting the existing data. The newly available Herschel Hi-GAL data which covers most of the inner Milky-Way offers a unique opportunity to investigate possible variations in the dust emission properties both with wavelength and environment. By combining the IRIS 100 {\mu}m with the Hi-GAL 160, 250, 350 and 500 {\mu}m data, we model the dust emission spectra in each pixel of the Hi-GAL maps, using both the TLS model and, for comparison, a single modified black-body fit. The effect of temperature mixing along the line of sight is investigated. We find a slight decrease in the dust temperature with distance from the Galactic center. We also report the detection of a significant 500 {\mu}m emissivity excess in the peripheral regions of the plane (35\circ<|l|<70\circ) of about 13-15% of the emissivity, that can reach up to 20% in some HII regions. We present the spatial distribution of the best-fit values for the two main parameters of the TLS model, i.e. the charge correlation length, lc, used to characterize the disordered charge distribution (DCD) part of the model, and the amplitude A of the TLS processes, with respect to the DCD effect. They highlight the plausible existence of an overall gradient with distance to the Galactic center. A comparison with previous findings in the solar neighborhood shows that the local value of the excess is less than expected from the Galactic gradient observed here.
- Preprint Article
- 10.5194/egusphere-egu21-4677
- Mar 3, 2021
&lt;p&gt;&lt;span&gt;In this study, the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) is employed to simulate a dust process in Northwest China during May 2018. The model's ability to simulate the dust process in Northwest China is firstly evaluated using various satellite-retrieved and observational data.&amp;#160;The four-dimensional assimilation method is also used to optimize meteorological data and effectively improve the simulation of the dust process.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.801d5c9c7dff58208440161/sdaolpUECMynit/12UGE&amp;app=m&amp;a=0&amp;c=b418b127ce3d884ac51c57c8e08b6c0b&amp;ct=x&amp;pn=gepj.elif&amp;d=1&quot; alt=&quot;&quot;&gt;&amp;#160;&lt;br&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt; Fig. 1. &lt;span&gt;Differences of wind field (unit: m/s) between the simulations (a-d: unassimilated; e-h: assimilated) and the observations at 03:00 UTC on 20&amp;#8211;23 May.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;The comparisons between the simulations based on five dust emission schemes within WRF-Chem and the observations show that, the Shao01 scheme overall has good performance in simulating the emission flux, the spatial pattern of source region, as well as the spatiotemporal variation of dust mass concentration, during this dust process. In comparison to Shao01, the GOCART AFWA and Shao04 schemes can also produce quite similar spatial pattern of dust source region, but tend to overestimate or underestimate dust emission and mass concentration. The Shao11 scheme fails to simulate the dust process since the importance of the fully disturbed particle size distribution is omitted. It is also noted that the GOCART scheme can well reproduce dust emission processes under weak wind erosion but underestimate dust emission flux under strong wind erosion. In addition, the GOCART scheme has produced some spurious emissions and thus blurred the distribution of dust source region.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.8bd9016d7dff55228440161/sdaolpUECMynit/12UGE&amp;app=m&amp;a=0&amp;c=a4dbf8c16429b73a7229d74df7d94cf2&amp;ct=x&amp;pn=gepj.elif&amp;d=1&quot; alt=&quot;&quot;&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt; Fig. 2. &lt;span&gt;The averaged dust emission flux (unit: &amp;#956;g/m&lt;/span&gt;&lt;sup&gt;&lt;span&gt;2&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;/s) from the GOCART (a), GOCART AFWA (b), Shao01 (c), Shao04 (d) and Shao11 (e) schemes during 17&amp;#8211;23 May.&lt;/span&gt; &lt;br&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.1a6c618d7dff57528440161/sdaolpUECMynit/12UGE&amp;app=m&amp;a=0&amp;c=c10811a41ff5090c9600732d85d1b98e&amp;ct=x&amp;pn=gepj.elif&amp;d=1&quot; alt=&quot;&quot;&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt; Fig. 3. &lt;span&gt;Variations of daily (a) and hourly (b) surface PM&lt;sub&gt;10&lt;/sub&gt; concentrations, friction velocity (c) and 10 m wind speed (d) at the Turpan station during 17&amp;#8211;23 May.&lt;/span&gt;&lt;br&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Northwest China is covered by mountains, basins, deserts and other landforms, thus the complex terrain is one of the key factors to influence the dust process over the region. Our study shows that after being emitted, the airborne dust transported toward the east and west. The dust to the east was diffused rapidly, but the portion toward the west was blocked and accumulated at the edges of the mountains and thus produced dust weather characterized by high dust concentration and long lifetime. The dust accumulated at the edges of the mountains could reach an altitude of more than 6 km due to wind and thermal effect, and finally arrive at Tibetan Plateau and eastern China.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.b97f3e9d7dff56828440161/sdaolpUECMynit/12UGE&amp;app=m&amp;a=0&amp;c=ebe09adfba0a7bc878587c33b5673a37&amp;ct=x&amp;pn=gepj.elif&amp;d=1&quot; alt=&quot;&quot;&gt;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt; Fig. 4. &lt;span&gt;The simulated (with Shao01 scheme) dust (unit: &amp;#956;g /m&lt;/span&gt;&lt;sup&gt;&lt;span&gt;3&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;) transport path (a-c) during 20&amp;#8211;23 May and vertical profiles of 38.5&amp;#176;N (d) and 85&amp;#176;E (g) at 05:00 UTC on 21 May, 36&amp;#176;N (e) and 95&amp;#176; E (h) at 06:00 UTC on 22 May and 36&amp;#176;N (f) and 98&amp;#176;E (i) at 05:00 UTC on 23 May.&lt;/span&gt; &lt;br&gt;&lt;/span&gt;&lt;/p&gt;
- Research Article
- 76
- 10.1016/j.atmosres.2020.104978
- Apr 3, 2020
- Atmospheric Research
Dust emission and transport in Northwest China: WRF-Chem simulation and comparisons with multi-sensor observations
- Research Article
- 17
- 10.13031/2013.18499
- Jan 1, 2005
- Transactions of the ASAE
Reducing odor emissions from swine farms to avoid complaints about odor nuisance is a major issue. Ozonationhas been used to reduce odor in swine buildings, but little research exists on its benefits. A swine-finishing building wasdivided into two identical rooms and two treatments, ozonation and the control, were applied in a cross-over design. Thetreatments were switched between rooms every three weeks. The overall experimental period was 12 weeks, during whichthere were four trials. Pig growth performance, dust mass and size concentration, odor intensity, total sulfur compounds,hydrogen sulfide concentration, ammonia concentration, and total heterotrophic bacterial counts were measured andanalyzed during the test period. Sulfur-containing compounds detected included dimethyldisulfide, dimethylsulfide(methanethiol), and dimethyltrisulfide. Ozone application to a swine building at the maximum safe concentration of 0.1 ppmdid not have any statistically significant effects on dust mass concentration, odor concentration and emission rate, sulfurcompound concentrations, and bacteria counts. However, it did increase ammonia concentration and decrease pig averagedaily gain. The ozonation effects on hydrogen sulfide concentration could not be evaluated by the gas tube method used duringthis study.
- Research Article
- 10
- 10.5194/acp-23-14271-2023
- Nov 16, 2023
- Atmospheric Chemistry and Physics
Abstract. Over the past decades, northern China has been suffering from persistent air pollution caused by both fine and coarse atmospheric particles. Although there are plenty of theoretical and observational studies on aerosols in northern China, most of them only consider total aerosol concentrations and focus on heavy pollution episodes; the long-term vertical distributions of dust (coarse) and anthropogenic aerosols (fine) and their relationships with the mixing layer height (MLH) have not been revealed. In this study, the dust and anthropogenic aerosols' mass concentration and the MLH were retrieved by polarization Raman lidar over Beijing from May 2019 to February 2022. We found that large amounts of anthropogenic aerosols accumulate at the top of the mixing layer, which is most noticeable in summer, with monthly mean mass concentration up to 57 µg m−3. It is mainly influenced by the southward transport in the upper air, where the atmosphere is relatively stable and moist, favoring hygroscopic growth of particles. Dust mass concentration is discontinuous in the vertical direction, not only on the ground but also in lofted layers that reach up to several kilometers. The heights of these lofted dust layers exhibited apparent seasonal dependence, with the height of the main dust layer gradually ascending from 1.1 km to about 2.5 km from April to June and below 3 km from October to December. In addition, there is a significant negative correlation between bottom anthropogenic aerosols' mass concentration and the MLH, and an inverse function fit is more suitable to characterize this relationship, while the relationship between bottom dust mass concentration and the MLH is insignificant. These results will enhance our understanding of the sophisticated interactions between dust and anthropogenic aerosols, the MLH, and regional transport in northern China. It will also help to refine atmospheric chemistry models and improve surface prediction capabilities.
- Research Article
- 78
- 10.1016/j.atmosenv.2016.10.051
- Oct 31, 2016
- Atmospheric Environment
Role of surface wind and vegetation cover in multi-decadal variations of dust emission in the Sahara and Sahel
- Research Article
- 52
- 10.5194/acp-20-4695-2020
- Apr 21, 2020
- Atmospheric Chemistry and Physics
Abstract. For the first time, continuous, vertically resolved long-term aerosol measurements were conducted with a state-of-the-art multiwavelength lidar over a Central Asian site. Such observations are urgently required in efforts to predict future climate and environmental conditions and to support spaceborne remote sensing (ground truth activities). The lidar observations were performed in the framework of the Central Asian Dust Experiment (CADEX) at Dushanbe, Tajikistan, from March 2015 to August 2016. An AERONET (AErosol RObotic NETwork) sun photometer was operated at the lidar field site. During the 18-month campaign, mixtures of continental aerosol pollution and mineral dust were frequently detected from ground to cirrus height level. Regional sources of dust and pollution as well as long-range transport of mineral dust mainly from Middle Eastern and the Saharan deserts determine the aerosol conditions over Tajikistan. In this study, we summarize our findings and present seasonally resolved statistics regarding aerosol layering (main aerosol layer depth, lofted layer occurrence); optical properties (aerosol and dust optical thicknesses at 500–532 nm, vertically resolved light-extinction coefficient at 532 nm); profiles of dust and non-dust mass concentrations and dust fraction; and profiles of particle parameters relevant for liquid water, mixed-phase cloud, and cirrus formation such as cloud condensation nuclei (CCN) and ice-nucleating particle (INP) concentrations. The main aerosol layer over Dushanbe typically reaches 4–5 km height in spring to autumn. Frequently lofted dust-containing aerosol layers were observed at heights from 5 to 10 km, indicating a sensitive potential of dust to influence cloud ice formation. Typical dust mass fractions were of the order of 60 %–80 %. A considerable fraction is thus anthropogenic pollution and biomass burning smoke. The highest aerosol pollution levels (in the relatively shallow winter boundary layer) occur during the winter months. The seasonal mean 500 nm AOT (aerosol optical thickness) ranges from 0.15 in winter to 0.36 in summer during the CADEX period (March 2015 to August 2016); DOTs (dust optical thicknesses) were usually below 0.2; seasonally mean particle extinction coefficients were of the order of 100–500 Mm−1 in the main aerosol layer during the summer half year and about 100–150 Mm−1 in winter but were mainly caused by anthropogenic haze. Accordingly, the highest dust mass concentrations occurred in the summer season (200–600 µg m−3) and the lowest during the winter months (20–50 µg m−3) in the main aerosol layer. In winter, the aerosol pollution mass concentrations were 20–50 µg m−3, while during the summer half year (spring to autumn), the mass concentration caused by urban haze and biomass burning smoke decreases to 10–20 µg m−3 in the lower troposphere. The CCN concentration levels are always controlled by aerosol pollution. The INP concentrations were found to be high enough in the middle and upper troposphere to significantly influence ice formation in mixed-phase and ice clouds during spring and summer seasons.
- Preprint Article
- 1
- 10.5194/egusphere-egu23-9569
- May 15, 2023
Mineral dust emissions play a fundamental role in the simulation of the dust cycle in numerical models. The emission of dust depends on a number of atmospheric and surface conditions that span a large range of time and spatial scales. Due to the inherent difficulties to physically represent this complexity in a simplified way, the emission of mineral dust is usually parameterized in the atmospheric numerical models. The heterogeneity of available dust emission parametrizations, along with the soil characteristics and meteorological information, the atmospheric models themselves, their tuning, and their boundary and initial conditions, contribute to the large spread of net dust flux estimated with different modeling frameworks.This work presents a novel approach to estimate dust emissions through the assimilation of dust optical depth filtered retrievals from satellite measurements, by means of an ensemble-based data assimilation scheme. Because of the lagged nature of the emission inversion problem, the assimilation is produced with a slightly modified version of the ensemble Kalman Filter algorithm. We show results of the inversion for 5-year global numerical experiments (2017 to 2021), by using dust-only simulations with three of the available state-of-the-art dust emission schemes implemented in the chemical MONARCH model.In these three experiments, we assimilate dust optical depth obtained from the SNPP-VIIRS Deep Blue retrievals. The control vector consists of model dust emissions at native spatial resolution (1.4 by 1 degrees) and a 3-days time resolution. We find regional and temporal corrections in the estimated emissions after assimilation that are consistent across the different dust emission scheme experiments, making our findings robust. We compare the dust optical depth of our simulations with the assimilated observations, as well as with independent dust-filtered optical depth from ground-based AERONET sun-photometers. The dust optical depth resulting from the simulations that use the corrected emissions show substantial improvements in the skill scores than the dust optical depth simulated with the uncorrected emissions. Our work paves the road toward quantifying and eventually reducing uncertainties in dust emission schemes and toward better constraining the contribution to climate of the dust sources at sub-regional scale.
- Research Article
- 28
- 10.5194/acp-20-10047-2020
- Aug 28, 2020
- Atmospheric Chemistry and Physics
Abstract. North African dust reaches the southeastern United States every summer. Size-resolved dust mass measurements taken in Miami, Florida, indicate that more than one-half of the surface dust mass concentrations reside in particles with geometric diameters less than 2.1 µm, while vertical profiles of micropulse lidar depolarization ratios show dust reaching above 4 km during pronounced events. These observations are compared to the representation of dust in the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) aerosol reanalysis and closely related Goddard Earth Observing System model version 5 (GEOS-5) Forward Processing (FP) aerosol product, both of which assimilate satellite-derived aerosol optical depths using a similar protocol and inputs. These capture the day-to-day variability in aerosol optical depth well, in a comparison to an independent sun-photometer-derived aerosol optical depth dataset. Most of the modeled dust mass resides in diameters between 2 and 6 µm, in contrast to the measurements. Model-specified mass extinction efficiencies equate light extinction with approximately 3 times as much aerosol mass, in this size range, compared to the measured dust sizes. GEOS-5 FP surface-layer sea salt mass concentrations greatly exceed observed values, despite realistic winds and relative humidities. In combination, these observations help explain why, despite realistic total aerosol optical depths, (1) free-tropospheric model volume extinction coefficients are lower than those retrieved from the micro-pulse lidar, suggesting too-low model dust loadings in the free troposphere, and (2) model dust mass concentrations near the surface can be higher than those measured. The modeled vertical distribution of dust, when captured, is reasonable. Large, aspherical particles exceeding the modeled dust sizes are also occasionally present, but dust particles with diameters exceeding 10 µm contribute little to the measured total dust mass concentrations after such long-range transport. Remaining uncertainties warrant a further integrated assessment to confirm this study's interpretations.
- Research Article
- 87
- 10.1086/508057
- Nov 20, 2006
- The Astrophysical Journal
We explore the nature of variations in dust emission within an individual galaxy using 3.6 - 160 micron Spitzer Space Telescope observations and 450 and 850 micron James Clerk Maxwell Telescope observations of the edge-on Sd spiral galaxy NGC 4631 with the goals of understanding the relation between polycyclic aromatic hydrocarbons (PAH) and dust emission, studying the variations in the colors of the dust emission, and searching for possible excess submillimeter emission compared to what is anticipated based on dust models applied to the mid- and far-infrared data. PAH emission at 8 micron is found to correlate best with hot dust emission at 24 micron on kiloparsec scales, although the relation breaks down on scales equal to hundreds of parsecs, possibly because of differences in the mean free paths between the photons that excite the PAHs and heat the dust and possibly because the PAHs are destroyed by the hard radiation fields in the centers of some star formation regions. The ratio of 8 micron PAH emission to 160 micron cool dust emission appears to be a function of radius. The 70/160 and 160/450 micron flux density ratios are remarkably constant even though the surface brightness varies by a factor of 25 in each wave band, which suggests that the emission is from dust heated by a nearly-uniform radiation field. Globally, we find an excess of 850 micron emission relative to what would be predicted by dust models. The 850 micron excess is highest in regions with low 160 micron surface brightness, although the strength and statistical significance of this result depends on the model fit to the data. We rule out variable emissivity functions or ~4 K dust as the possible origins of this 850 micron emission, but we do discuss the other possible mechanisms that could produce the emission.
- Research Article
- 11
- 10.1109/access.2021.3059068
- Jan 1, 2021
- IEEE Access
For a pulsed laser transmitted in the raised dust from battlefield vehicle movement, the premise of obtaining its transmission properties and anti-jamming method is to acquire the spatial distribution rules of dust mass concentration. In this study, the emission mechanism for vehicle-raised dust in the battlefield environment is analyzed, as well as various influencing factors of the dust emission velocity. A finite volume method (FVM)-based model for simulating the spatial dispersion of dust raised by a certain moving tank is built, and the effects of mass flow rate, traveling speed, wind speed and wind direction on the spatial distribution of dust mass concentration are explored in the battlefield environment. The results show that the raised dust is plume-shaped within the computational domain, and the spatial mass concentration of plume is positively correlated with the mass flow rate. Besides, it is necessary to determine the impact of tank travelling speed on the spatial mass concentration of dust based on the relationship between the travelling speed and the dust mass flow rate. Although front wind reduces the spatial mass concentration of dust plumes, the reduction rate decelerates when the wind speed exceeds 4 m/s. Crosswind leads to the deflection and decreased mass concentration of dust plumes. Under varying wind directions, the variation of crosswind component exerts a more pronounced influence on the spatial mass concentration of dust than that of the front wind component. This study provides a technical support for the further study of near-ground laser weapon system against vehicle dust interference in the battle field.
- Research Article
- 36
- 10.1016/s1672-2515(07)60058-x
- Oct 1, 2004
- China Particuology
Seasonal characterization of dust days, mass concentration and dry deposition of atmospheric aerosols over qingdao, china
- Research Article
- 23
- 10.1093/annhyg/mes050
- Aug 16, 2012
- The Annals of Occupational Hygiene
Dust mass concentrations, temperatures, and carbon dioxide concentrations were mapped in a modern, 1048-pen swine gestation barn in winter, spring, and summer. In each season, two technicians measured respirable mass concentrations with an aerosol photometer and temperatures and carbon dioxide concentrations with an indoor air quality monitor at 60 positions in the barn. Stationary photometers were also deployed to measure mass concentrations during mapping at five fixed locations. In winter when building ventilation rates were low (center-barn mean air velocity=0.34 m s(-1), 68 fpm) to conserve heat within the barn, mass and carbon dioxide concentrations were highest (mass geometric mean, GM=0.50 mg m(-3); CO2 GM=2060 ppm) and fairly uniform over space (mass geometric standard deviation, GSD=1.48; CO2 GSD=1.24). Concentrations were lowest in summer (mass GM=0.13 mg m(-3); CO2 GM=610 ppm) when ventilation rates were high (center-barn mean air velocity=0.99 m s(-1), 196 fpm) to provide cooling. Spatial gradients were greatest in spring (mass GSD=2.11; CO2 GSD=1.50) with low concentrations observed near the building intake, increasing to higher concentrations at the building exhaust. Mass concentrations obtained in mapping were generally consistent with those obtained from stationary monitors. A moderately strong linear relationship (R2=0.60) was observed between the log of photometer-measured mass concentration and the log of carbon dioxide concentration, suggesting that carbon dioxide may be an inexpensive alternative to assessing air quality in a swine barn. These results indicate that ventilation can effectively reduce contaminant levels in addition to controlling temperature.
- Research Article
- 79
- 10.1051/0004-6361:20010930
- Sep 1, 2001
- Astronomy & Astrophysics
\n \nWe present an extinction map of the Polaris molecular cirrus cloud derived\nfrom star counts and compare it with the Schlegel et al. ([CITE]) extinction map\nderived from the far-infrared dust opacity.\nWe find that, within the Polaris cloud, the Schlegel et al. ([CITE])\nAV values are a factor 2 to 3 higher than the star count values. \nWe propose that this discrepancy results from a difference in \n$\\tau_{\\rm FIR}/ A_V$ between the diffuse atomic medium and the Polaris \ncloud. We use the difference in spectral energy distribution, warm for \nthe diffuse atomic medium, cold for the Polaris cloud, to separate\ntheir respective contribution to the line of sight integrated infrared\nemission and find that the $\\tau_{\\rm FIR}/ A_V$ of cold dust in\nPolaris is on average 4 times higher than the Schlegel et al. ([CITE]) value for dust\nin atomic cirrus. This change in dust property could be interpreted by a\ngrowth of fluffy particles within low opacity molecular cirrus clouds such\nas Polaris. \nOur work suggests that variations in dust emissivity must be taken \ninto account to estimate AV from dust emission wherever cold\ninfrared emission is present (i.e. molecular clouds). \n \n\n
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