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Responses of phytoplankton community to the input of different aerosols in the East China Sea (2016)

X. Meng, Y. Chen, B. Wang, Q.W. Ma, F. J. Wang

Wiley

In: Geophysical Research Letters

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Publikationsdatum: 2016-06-23

Beschreibung: Atmospheric deposition can affect marine phytoplankton by supplying macronutrients and trace elements. We conducted mesocosm experiments by adding aerosols with different composition (dominated by mineral dust, biomass burning and high Cu, and secondary aerosol, respectively) to the surface seawater of the East China Sea. Chlorophyll a concentrations were found to be the highest and lowest after adding aerosols containing the highest Fe and dissolved inorganic nitrogen (DIN), respectively. The relative abundance of Haptophyceae increased significantly after adding mineral dust, whereas diatom, Dinophyceae and Cryptophyceae reached the maximum accompanied with the highest DIN. Our results suggest that Fe may be more important than DIN in promoting primary productivity in the sampled seawater. The input of mineral dust and anthropogenic aerosols may result in distinct changes of phytoplankton community structure.

Print ISSN: 0094-8276

Digitale ISSN: 1944-8007

Thema: Geologie und Paläontologie , Physik

Publiziert von Wiley im Namen von American Geophysical Union (AGU).

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Sporadic and thermospheric enhanced sodium layers observed by a lidar chain over China (2013)

X. K. Dou, S. C. Qiu, X. H. Xue, T. D. Chen, B. Q. Ning

Wiley

In: Journal of Geophysical Research JGR - Space Physics

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Publikationsdatum: 2013-09-20

Beschreibung: [1] We report the statistical features of sporadic sodium layers (SSLs) and the thermospheric enhanced sodium layers (TeSLs) observed by a lidar chain located at Beijing (40.2°N, 116.2°E), Hefei (31.8°N, 117.3°E), Wuhan (30.5°N, 114.4°E), and Haikou (19.5°N, 109.1°E). The average SSL occurrence rate was approximately 46.0, 12.3, 13.8, and 15.0 hr per SSL at Beijing, Hefei, Wuhan, and Haikou, respectively. However, the TeSLs occurred relatively infrequently and were more likely to appear at low and high latitudinal sites. Both the SSLs and TeSLs at four lidar sites showed evident summer enhancements and correlated well with Es ( f o E s 〉 4 MHz ). The co-observations of SSLs at three lidar site pairs, i.e., Hefei – Beijing, Hefei – Wuhan and Hefei – Beijing, indicated that a large-scale SSL extended horizontally for at least a few hundred kilometers and exhibited a tidal-induced modulation. Moreover, the SSLs were better correlated for the Hefei – Wuhan and Hefei – Haikou pairs than the Hefei – Beijing pair, which suggested a difference in the dynamical/chemical process in mesosphere and lower thermosphere (MLT) between the Beijing site and the other sites.

Print ISSN: 0148-0227

Thema: Geologie und Paläontologie , Physik

Publiziert von Wiley im Namen von American Geophysical Union (AGU).

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An observationally based evaluation of cloud ice water in CMIP3 and CMIP5 GCMs and contemporary reanalyses using contemporary satellite data (2012)

J.-L. F. Li, D. E. Waliser, W.-T. Chen, B. Guan, T. Kubar, G. Stephens, H.-Y. Ma, M. Deng, L. Donner, C. Seman and L. Horowitz

Wiley

In: Journal of Geophysical Research JGR - Atmospheres

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Publikationsdatum: 2012-08-21

Beschreibung: We perform an observationally based evaluation of the cloud ice water content (CIWC) and path (CIWP) of present-day GCMs, notably 20th century CMIP5 simulations, and compare these results to CMIP3 and two recent reanalyses. We use three different CloudSat + CALIPSO ice water products and two methods to remove the contribution from the convective core ice mass and/or precipitating cloud hydrometeors with variable sizes and falling speeds so that a robust observational estimate can be obtained for model evaluations. The results show that for annual mean CIWP, there are factors of 2–10 in the differences between observations and models for a majority of the GCMs and for a number of regions. However, there are a number of CMIP5 models, including CNRM-CM5, MRI, CCSM4 and CanESM2, as well as the UCLA CGCM, that perform well compared to our past evaluations. Systematic biases in CIWC vertical structure occur below the mid-troposphere where the models overestimate CIWC, with this bias arising mostly from the extratropics. The tropics are marked by model differences in the level of maximum CIWC (∼250–550 hPa). Based on a number of metrics, the ensemble behavior of CMIP5 has improved considerably relative to CMIP3, although neither the CMIP5 ensemble mean nor any individual model performs particularly well, and there are still a number of models that exhibit very large biases despite the availability of relevant observations. The implications of these results on model representations of the Earth radiation balance are discussed, along with caveats and uncertainties associated with the observational estimates, model and observation representations of the precipitating and cloudy ice components, relevant physical processes and parameterizations.

Print ISSN: 0148-0227

Thema: Geologie und Paläontologie , Physik

Publiziert von Wiley im Namen von American Geophysical Union (AGU).

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Numerical Simulation of the Two-Phase Fluid Field in a Gas-Around-Liquid Spray Nozzle (2013)

D. Liu, B. Chen, B. Zhang

Wiley

In: Chemical Engineering and Technology

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Publikationsdatum: 2013-02-07

Beschreibung: A new gas-around-liquid spray nozzle (GLSN) was designed, and the two-phase flow fluid field in this nozzle was simulated numerically. Flow characteristics under different structural parameters were obtained by changing the L / D ratio of the premixing chamber, incident angle, and inlet pressures. Increasing the L / D ratio and incident angle improved flow characteristics such as atomization flow, outlet velocity, and turbulence intensity. The nozzle performed optimally at an L / D ratio of 0.5 and incident angle of 60°. The atomization flow decreased with higher gas pressure and increased with higher liquid pressure. The outlet velocity mainly depended on the inlet gas pressure, not on the inlet liquid pressure. These results provide an indication for optimum structures and parameters of the GLSN. Since the atomization effect of spray nozzles plays a key role in wet flue gas desulfurization processes, an innovative gas-around-liquid spray nozzle was designed. The two-phase flow fluid field in this nozzle was simulated numerically and the flow characteristics were determined with different structural parameters to find the optimum conditions.

Print ISSN: 0930-7516

Digitale ISSN: 1521-4125

Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Publiziert von Wiley

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Interannual variations and trends in surface air temperature in Finland in relation to atmospheric circulation patterns, 1961–2011 (2014)

M. Irannezhad, D. Chen, B. Kløve

Wiley

In: International Journal of Climatology

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Publikationsdatum: 2014-11-12

Beschreibung: ABSTRACT Annual and seasonal variations in surface air temperature (SAT) during the period 1961–2011 were analysed using daily mean temperature data sets from regular grid points (10 × 10 km 2 ) throughout Finland. The Mann–Kendall nonparametric test was used to detect significant historical trends in SAT and Spearman's correlation coefficient ( ρ ) to test the relationships between SAT patterns and various atmospheric circulation patterns over the northern hemisphere. The results showed that mean annual SAT in Finland increased ( p 〈 0.05) by 0.4 ± 0.2 °C per decade during the study period and that the SAT was significantly ( ρ = 0.58, p 〈 0.05) positively correlated with the Arctic Oscillation (AO) index. However, there were spatial differences within Finland for both the trends and relationships with the atmospheric circulation. Analysis of seasonal mean SAT identified significant ( p 〈 0.05) warming trends for both spring (by 0.4 ± 0.2 °C per decade) and summer (by 0.3 ± 0.2 °C per decade). Winter and spring mean SATs were most strongly ( p 〈 0.05) correlated with the AO index ( ρ = 0.72 and 0.42, respectively), while the most significant teleconnection pattern for mean SAT in summer was the East Atlantic (EA) pattern ( ρ = 0.43, p 〈 0.05); and in autumn the EA/West Russia (WR) pattern ( ρ = −0.59, p 〈 0.05). These results provide a detailed spatial picture of climate warming in Finland in recent decades and reveal that interannual variation of the SAT in Finland is closely linked with a number of atmospheric circulation patterns, not just the AO and North Atlantic Oscillation (NAO). Annual and cold-season SAT are mainly influenced by the AO and NAO, whereas the EA, EA/WR, Scandinavia (SCA) and West Pacific (WP) patterns play an important role for warm-season SAT.

Print ISSN: 0899-8418

Digitale ISSN: 1097-0088

Thema: Geologie und Paläontologie , Physik

Publiziert von Wiley

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6

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Magnetospheric Multiscale Observations of Large-Amplitude, Parallel, Electrostatic Waves Associated with Magnetic Reconnection at the Magnetopause (2016)

R. E. Ergun, J. C. Holmes, K. A. Goodrich, F. D. Wilder, J. E Stawarz, S. Eriksson, D. L. Newman, S. J Schwartz, M.V. Goldman, A. P. Sturner, D. M. Malaspina, M. E. Usanova, R. B. Torbert, M. Argall, P.-A. Lindqvist, Y. Khotyaintsev, J. L. Burch, R. J. Strangeway, C. T. Russell, C. J. Pollock, B. L. Giles, J. J. C. Dorelli, L. Avanov, M. Hesse, L. J. Chen, B. Lavraud, O. Le Contel, A. Retino, T. D. Phan, J. P. Eastwood, M. Oieroset, J. Drake, M. A. Shay, P. A. Cassak, R. Nakamura, M. Zhou, M. Ashour-Abdalla, M. André

Wiley

In: Geophysical Research Letters

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Publikationsdatum: 2016-05-14

Beschreibung: We report observations from the Magnetospheric Multiscale (MMS) satellites of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the Earth's magnetopause. The observed waves have parallel electric fields ( E || ) with amplitudes on the order of 100 mV/m and display non-linear characteristics that suggest a possible net E || . These waves are observed within the ion diffusion region and adjacent to (within several electron skin depths) the electron diffusion region. They are in or near the magnetosphere-side current layer. Simulation results support that the strong electrostatic linear and nonlinear wave activity appears to be driven by a two stream instability, which is a consequence of mixing cold (〈〈 10 eV) plasma in the magnetosphere with warm (~100 eV) plasma from the magnetosheath on a freshly reconnected magnetic field line. The frequent observation of these waves suggests that cold plasma is often present near the magnetopause.

Print ISSN: 0094-8276

Digitale ISSN: 1944-8007

Thema: Geologie und Paläontologie , Physik

Publiziert von Wiley im Namen von American Geophysical Union (AGU).

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A computational method for simulating subsurface flow and reactive transport in heterogeneous porous media embedded with flexible uncertainty quantification (2013)

X. Chen, B. M. Ng, Y. Sun, C. H. Tong

Wiley

In: Water Resources Research

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Publikationsdatum: 2013-08-10

Beschreibung: In [ Chen et al ., 2013], the fundamental concepts of the modular UQ methodology has been introduced for multi-physics applications in which each physics module can be independently embedded with its internal UQ method (intrusive or non-intrusive). Although the methodology offers the advantage of “plug-and-play” flexibility for general multi-physics systems without losing the global uncertainty propagation property, it is inadequate to quantify uncertainties of reactive transport in heterogeneous porous media. In the current paper, we extend the modular UQ methodology to subsurface flow and reactive transport applications, which are characterized by high dimensionality in the stochastic space due to spatially random velocity field in randomly heterogeneous porous media. Specifically, we develop a scheme to reduce the dimension of the stochastic space. This is achieved via a doubly-nested dimension reduction by applying Karhunen-Loeve expansion [ Karhunen , 1947; Kac and Siegert , 1947] to the logarithmic hydraulic conductivity field and Proper Orthogonal Decomposition [ Pearson , 1901; Hotelling , 1933] to the velocity field. This scheme enables the modular UQ framework to handle spatially random models efficiently while maintaining solution accuracy. When compared against sampling-based non-intrusive UQ methods, the modular UQ method demonstrates a similar accuracy at a fraction of computational cost on designed numerical experiments.

Print ISSN: 0043-1397

Digitale ISSN: 1944-7973

Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie

Publiziert von Wiley im Namen von American Geophysical Union (AGU).

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How Well the Early 2017 California Atmospheric River Precipitation Events Were Captured by Satellite Products and Ground-based Radars? (2018)

Y. Wen, A. Behrangi, H. Chen, B. Lambrigtsen

Wiley

In: Quarterly Journal of the Royal Meteorological Society

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Publikationsdatum: 2018-02-11

Beschreibung: ABSTRACT In January and February of 2017, California experienced multiple heavy storms that caused serious destruction of facilities and economic loss, although it also helped to reduce water storage deficit due to prolonged drought in previous years. These extreme precipitation events were mainly associated with Atmospheric Rivers (ARs) and brought about 174 km 3 of water to California according to ground observations. This paper evaluates the performance of six commonly used satellite-based precipitation products (IMERG, 3B42RT, PERSIANN, CCS, CMORPH, and GSMaP), as well as ground-based radar products (Radar-only and Radar-lgc) in capturing the ARs precipitation rate and distribution. It is found that precipitation maps from all products present heavy precipitation in January and February, with more consistent observations over ocean than land. Though large uncertainties exist in quantitative precipitation estimation (QPE) over land, the ensemble mean of different remote sensing precipitation products over California is consistent with gauge measurements. Among the six satellite-based products, IMERG correlates the best with gauge observations both in the detection and quantification of precipitation, but it is not the best product in terms of root mean square error (RMSE) or bias. Compared to satellite products, ground weather radar shows better precipitation detectability and estimation skill. However, neither radar nor satellite QPE products have good performances in quantifying the peak precipitation intensity during the extreme events, suggesting that further advancement in quantification of extremely intense precipitation associated with AR in the Western United States is needed.

Print ISSN: 0035-9009

Digitale ISSN: 1477-870X

Thema: Geographie , Physik

Publiziert von Wiley

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