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Aerosol Optical Properties and Determination of Aerosol Size Distribution in Wuhan, China

Author(s):Wei Gong -- Shanshan Zhang -- Yingying Ma
Journal: Atmosphere
Publisher:
Abstract
| Pages: 81-91
Columnar aerosol volume size distributions from March 2012 to February 2013 in Wuhan, China, were investigated with a focus on monthly and seasonal variations in the aerosol optical depths (AODs) and Ångström exponents. AOD is wavelength dependent, and for AOD at, for example, 500 nm, the seasonal averaged AOD value decreased in the order of winter (~0.84), spring (~0.83), summer (~0.76) and autumn (~0.55). The Ångström exponent suggested that the aerosol sizes in summer (~1.22), winter (~1.14), autumn (~1.06) and spring (~0.99) varied from fine to coarse particles. The Ångström exponent and AOD could provide a qualitative evaluation of ASD. Moreover, aerosol size distribution (ASD) was larger in winter than the other three seasons, especially from 1.0 µm to 15 µm due to heavy anthropogenic aerosol and damp climate. The ASD spectral shape showed a bimodal distribution in autumn, winter, and spring, with one peak (<0.1) in the fine mode range and the other (>0.14) in the coarse mode range. However, there appeared to be a trimodal distribution during summer, with two peaks in the coarse mode, which might be due to the hygroscopic growth of the local particles and the generation of aerosol precursor resulting from the extreme-high temperature and relative humidity.

Variance of Fluctuating Radar Echoes from Thermal Noise and Randomly Distributed Scatterers

Author(s):Marco Gabella
Journal: Atmosphere
Publisher:
Abstract
| Pages: 92-100
In several cases (e.g., thermal noise, weather echoes, …), the incoming signal to a radar receiver can be assumed to be Rayleigh distributed. When estimating the mean power from the inherently fluctuating Rayleigh signals, it is necessary to average either the echo power intensities or the echo logarithmic levels. Until now, it has been accepted that averaging the echo intensities provides smaller variance values, for the same number of independent samples. This has been known for decades as the implicit consequence of two works that were presented in the open literature. The present note deals with the deriving of analytical expressions of the variance of the two typical estimators of mean values of echo power, based on echo intensities and echo logarithmic levels. The derived expressions explicitly show that the variance associated to an average of the echo intensities is lower than that associated to an average of logarithmic levels. Consequently, it is better to average echo intensities rather than logarithms. With the availability of digital IF receivers, which facilitate the averaging of echo power, the result has a practical value. As a practical example, the variance obtained from two sets of noise samples, is compared with that predicted with the analytical expression derived in this note (Section 3): the measurements and theory show good agreement.

Spatio-Temporal Variability of Winter Monsoon over the Indochina Peninsula

Author(s):Sirapong Sooktawee -- Usa Humphries -- Atsamon Limsakul -- Prungchan Wongwises
Journal: Atmosphere
Publisher:
Abstract
| Pages: 101-121
In this study, the spatial patterns and their interannual variability of wintertime low-level winds over the Indochina Peninsula (IDP) were studied by using the analysis of the empirical orthogonal function for complex numbers. The leading mode accounts for 46.6% of the total variance. The composite and regressed patterns of wind components show dominant northeasterly wind over the IDP, which are related to the East Asia winter monsoon (EAWM) circulation and connected to the cyclonic circulation near Borneo. The correlations between the EAWM indices and the leading principal component (PC) suggest the plausible connections between the low-level wind over the IDP and EAWM predominantly via the wind circulation. We also performed correlation analysis on the relationship between leading mode and sea surface temperature anomalies (SSTAs). The result indicates that there is a linkage between the northeasterly wind over the IDP and EAWM and with SSTAs in the Pacific Ocean. This study provides useful information and a mechanism related to the monsoon variability over the IDP.

Acknowledgement to Reviewers of Atmosphere in 2013

Author(s):Atmosphere Editorial Office
Journal: Atmosphere
Publisher:
Abstract
| Pages: 122-123
The editors of Atmosphere would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2013. [...]

Sources and Dynamic Processes Controlling Background and Peak Concentrations of TGM in Nanjing, China

Author(s):Casey B. Hall -- Huiting Mao -- Zhuyun Ye -- Robert Talbot -- Aijun Ding -- Yang Zhang -- Jialei Zhu -- Tijian Wang -- Che-Jen Lin -- Congbin Fu -- Xiuqun Yang
Journal: Atmosphere
Publisher:
Abstract
| Pages: 124-155
Total gaseous mercury (TGM) data from urban Nanjing, at the western edge of the Yangtze River Delta (YRD) region in China, over nine months, were analyzed for peak and background mercury concentrations. The background concentration of TGM was found to be 2.2 ng∙m−3. In examining episodic influences of free tropospheric air masses on the surface TGM concentrations in Nanjing, we hypothesize heterogeneity in the global distribution of TGM concentrations in the free troposphere. The nine-month averaged diurnal cycles of TGM indicate a strong co-emission with SO2 and an underestimation of greater than 80% TGM emissions in current inventories. Regular peak concentrations of mercury were investigated and the major causes were YRD emissions, transport from rural areas, and monsoonal transport. Transport of rural emissions is hypothesized to be from illegal artisanal small-scale gold mining that are currently missing in the emission inventories. Enhancement of TGM associated with summer monsoon contributed to a maximum TGM concentration in mid-May–early June, an inverse seasonality in comparison to most other observations in China, North America, and Europe.

Evaluation and Comparison of the Configuration Interaction Calculations for Complex Atoms

Author(s):Charlotte Froese Fischer
Journal: Atoms
Publisher:
Abstract
| Pages: 1-14
Configuration interaction (CI) methods are the method of choice for the determination of wave functions for complex atomic systems from which a variety of atomic properties may be computed. When applied to highly ionized atoms, where few, if any, energy levels from observed wavelengths are available, the question arises as to how a calculation may be evaluated. Many different codes are available for such calculations. Agreement between the results from different codes in itself is not a check on accuracy, but may be due to a similarity in the computational procedures. This paper reviews basic theory, which, when applied in a systematic manner, can be the basis for the evaluation of accuracy. Results will be illustrated in the study of 4s24p5 (odd) and 4s24p44d (even) levels in W39+ and the transitions between them.

Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities: An Experimenterís View

Author(s):Elmar Träbert
Journal: Atoms
Publisher:
Abstract
| Pages: 15-85
The interpretation of atomic observations by theory and the testing of computational predictions by experiment are interactive processes. It is necessary to gain experience with “the other side” before claims of achievement can be validated and judged. The discussion covers some general problems in the field as well as many specific examples, mostly organized by isoelectronic sequence, of what level of accuracy recently has been reached or which atomic structure or level lifetime problem needs more attention.

Swelling Properties of Hydrogels Containing Phenylboronic Acids

Author(s):Arum Kim -- Siddharthya K. Mujumdar -- Ronald A. Siegel
Journal: Chemosensors
Publisher:
Abstract
| Pages: 1-12
Phenylboronic acids are a class of compounds that bind glucose and other sugars. When polymerized into hydrogels, they provide a convenient nonenzymatic means for sensing glucose concentration, provided competing sugars are present at negligible concentrations. In this paper we provide a comprehensive study of swelling of hydrogels containing methacrylamidophenylboronic acid (MPBA), as a function of pH and concentration of either glucose or fructose. In one set of hydrogels, MPBA is substituted at 20 mol·% in a polyacrylamide hydrogel [p(MPBA-co-AAm)], while in a second set of hydrogels, 20 mol·% MPBA is supplemented with 20 mol·% of N-3-(dimethylaminopropyl methacrylamide) [p(MPBA-co-DMP-co-AAm)]. Swelling curves are markedly different for fructose and glucose, and for the two sets of hydrogels. While fructose alters swelling by binding and contributing to the ionization of MPBA, glucose does the same, but it also can form crosslinking bridges between separate chains, leading to hydrogel shrinkage. While the [p(MPBA-co-AAm)] hydrogels behaved as polyacids, swelling monotonically with increasing pH, the [p(MPBA-co-DMP-co-AAm)] hydrogels exhibited polyampholyte behavior, with swelling minima at intermediate pH values.

Reliability of Sensors Based on Nanowire Networks When the Electrical Current is Allowed to Move in All Directions

Author(s):Nader Ebrahimi -- Kristin McCullough
Journal: Chemosensors
Publisher:
Abstract
| Pages: 13-25
Nanowire networks have great potential in many industrial applications, including batteries, electrical circuits, solar cells, and sensors. In this paper we focus on a specific hydrogen gas nanosensor whose sensing element is a network of palladium nanowires. The nanosensor is modeled using a square, equilateral triangle, and hexagonal lattice. We provide the reliability behavior of this nanosensor when the electrical current is allowed to move in all directions. Our findings reveal an improvement in reliability compared to the scenario where the electrical current could not move from right to left. We show this improvement both analytically and through simulation.
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