Meteorological Institute of Shaanxi Province

Fengcheng, China

Meteorological Institute of Shaanxi Province

Fengcheng, China
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Dong Z.,Beijing Normal University | Dong Z.,Meteorological Institute of Shaanxi Province | Li Z.,Beijing Normal University | Li Z.,University of Maryland University College | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2017

Interactions between absorbing aerosols and the planetary boundary layer (PBL) play an important role in affecting air pollution near the surface. In this study, a unique feature of the aerosol-PBL interaction is identified that has important implications in monitoring and combating air pollution. Opposite trends in aerosol loading between the lower and upper PBL are shown on a wide range of timescales and data acquired by various platforms: from a short-term field experiment to decadal satellite observations and multidecadal ground observations in China. A novel method is proposed to obtain the vertical profiles of aerosol loading from passive sensors by virtue of varying elevations. The analyses of visibility, aerosol optical depth, and extinction with different temporal scales exhibit the similar trend, i.e., increasing in the lower atmosphere but decreasing in the upper atmosphere. Integration of the reversal aerosol trend below and above the PBL resulted in a much less change in the column-integrated quantities. The surface cooling effect, together with the change in the heating rate induced by the absorbing aerosol, unevenly modifies the atmospheric temperature profile, causing a more stable atmosphere inside the PBL but a destabilized atmosphere above the PBL. Such a change in the atmospheric stability favors the accumulation of pollutants near the surface and the vertical diffusion of aerosol particles in the upper atmosphere, both of which are consistent with the observed reversal aerosol trends. These findings have multiple implications in understanding and combating air pollution, especially in many developing countries with high emissions of light-absorbing aerosols. © Author(s) 2017.


Zhu Y.,Meteorological Institute of Shaanxi Province | Rosenfeld D.,Hebrew University of Jerusalem | Yu X.,Meteorological Institute of Shaanxi Province | Li Z.,Beijing Normal University | Li Z.,The Interdisciplinary Center
Journal of Geophysical Research D: Atmospheres | Year: 2015

The high resolution (375 m) of the Visible Infrared Imaging Radiometer Suite on board the Suomi National Polar-Orbiting Partnership satellite allows retrieving relatively accurately the vertical evolution of convective cloud drop effective radius (re) with height or temperature. A tight relationship is found over SE Asia and the adjacent seas during summer between the cloud-free aerosol optical depth (AOD) and the cloud thickness required for the initiation of warm rain, as represented by the satellite-retrieved cloud droplet re of 14 μm, for a subset of conditions that minimize measurement artifacts. This cloud depth (ΔT14) is parameterized as the difference between the cloud base temperature and the temperature at the height where re exceeds 14 μm (T14). For a unit increase of AOD, the height of rain initiation is increased by about 5.5 km. The concern of data artifacts due to the increase in AOD near clouds was mitigated by selecting only scenes with cloud fraction (CF) < 0.1. For CF > 0.1 and ΔT14 > ∼20°C, the increase of ΔT14 gradually levels off with further increase of AOD, possibly because the AOD is enhanced by aerosol upward transport and detrainment through the clouds below the T14 isotherm. The bias in the retrieved re due to the different geometries of solar illumination was also quantified. It was shown that the retrievals are valid only for backscatter views or when avoiding scenes with significant amount of cloud self-shadowing. These artifacts might have contributed to past reported relationships between cloud properties and AOD. © 2015. American Geophysical Union. All Rights Reserved.


Li J.,Nanjing University of Information Science and Technology | Yin Y.,Nanjing University of Information Science and Technology | Li P.,Weather Modification Office of Shanxi Province | Li Z.,Beijing Normal University | And 10 more authors.
Atmospheric Research | Year: 2015

For the first time, comprehensive aircraft measurements of atmospheric aerosols and cloud condensation nuclei (CCN) were made over the Loess Plateau in Shanxi, China. Data from six flights in July and August 2013 were analyzed. Fine aerosols were predominant over the region. On the one hazy day, the fraction of fine particles in the total aerosol load was the greatest. Aerosol number concentration decreased exponentially with altitude. Inversion layers caused low-level aerosol accumulation zones. The mean aerosol particle size increased with altitude, and the larger particles were mainly found above 2km. Aerosol number size distributions at different height ranges showed two or three peaks. The aerosol number size distribution from 0.01μm to 20μm can be fitted with three log-normal distribution functions. The number concentration of CCN (NCCN) decreased with altitude. NCCN was linearly related to the CN concentration (NCN). The fraction of CCN to CN (fCCN/CN) at 0.3% SS was half of that at 0.4% SS. The fCCN/CN on the hazy day was lower than on the clear days. Vertical profiles of fCCN/CN and the effective diameter (ED) were similar, although the fCCN/CN increased with altitude. © 2014 Elsevier B.V.


Li J.,Weather Modification Office of Shanxi Province | Li J.,Nanjing University of Information Science and Technology | Liu X.,Beijing Normal University | Yuan L.,Nanjing University of Information Science and Technology | And 10 more authors.
Journal of Environmental Sciences (China) | Year: 2015

Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients (σsc), absorption coefficients (σab), Angström exponent (α), single scattering albedo (ω), backscattering ratio (βsc), aerosol mass scattering proficiency (Qsc) and aerosol surface scattering proficiency (Qsc') were obtained. The mean statistical values of σsc were 77.45Mm-1 (at 450nm), 50.72Mm-1 (at 550nm), and 32.02Mm-1 (at 700nm). The mean value of σab was 7.62Mm-1 (at 550nm). The mean values of α, βsc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters (ED) of aerosols were less than 0.8μm. The vertical profiles of σsc,, α, βsc, Qsc and Qsc' showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and βsc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σsc, α, βsc, Qsc, Qsc', σab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions. © 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.


Rosenfeld D.,Hebrew University of Jerusalem | Liu G.,Meteorological Institute of Shaanxi Province | Yu X.,Meteorological Institute of Shaanxi Province | Zhu Y.,Meteorological Institute of Shaanxi Province | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2014

VIIRS (Visible Infrared Imaging Radiometer Suite), onboard the Suomi NPP (National Polar-orbiting Partnership) satellite, has an improved resolution of 750 m with respect to the 1000 m of the Moderate Resolution Imaging Spectroradiometer for the channels that allow retrieving cloud microphysical parameters such as cloud drop effective radius (re). VIIRS also has an imager with five channels of double resolution of 375 m, which was not designed for retrieving cloud products. A methodology for a high-resolution retrieval of and microphysical presentation of the cloud field based on the VIIRS imager was developed and evaluated with respect to MODIS in this study. The tripled microphysical resolution with respect to MODIS allows obtaining new insights for cloud-aerosol interactions, especially at the smallest cloud scales, because the VIIRS imager can resolve the small convective elements that are sub-pixel for MODIS cloud products. Examples are given for new insights into ship tracks in marine stratocumulus, pollution tracks from point and diffused sources in stratocumulus and cumulus clouds over land, deep tropical convection in pristine air mass over ocean and land, tropical clouds that develop in smoke from forest fires and in heavy pollution haze over densely populated regions in southeastern Asia, and for pyro-cumulonimbus clouds.
It is found that the VIIRS imager provides more robust physical interpretation and refined information for cloud and aerosol microphysics as compared to MODIS, especially in the initial stage of cloud formation. VIIRS is found to identify significantly more fully cloudy pixels when small boundary layer convective elements are present. This, in turn, allows for a better quantification of cloud-aerosol interactions and impacts on precipitation-forming processes. © 2014 Author (s).


PubMed | Hebrew University of Jerusalem, Max Planck Institute for Biogeochemistry, Max Planck Institute for Chemistry, Beijing Normal University and 3 more.
Type: Journal Article | Journal: Proceedings of the National Academy of Sciences of the United States of America | Year: 2016

Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Validation against ground-based CCN instruments at Oklahoma, at Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of 25% to 30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25 restricts the satellite coverage to 25% of the world area in a single day.


Yang W.-F.,Shaanxi Meteorological Bureau | Li X.-M.,Meteorological Institute of Shaanxi Province | Chen C.,Meteorological Institute of Shaanxi Province | Liu R.-F.,Shaanxi Meteorological Observatory | Du C.-L.,Meteorological Institute of Shaanxi Province
Zhongguo Huanjing Kexue/China Environmental Science | Year: 2015

Based on the meteorological and aerosol observed data, the change of wind, temperature, humidity, aerosol mass concentration, particle size distribution and scatter coefficient had been analyzed in Xi'an on 17~25 December 2013 and 20~26 February 2014.These factors had an effect on the fog/Haze of formation, development and lasting. The results showed: By ASP observation, particle number concentration between 0.5μm and 0.835μm of aerodynamic diameter increased obviously during the formation and maintaining of fog/haze. After the process of fog/haze, the particle number concentration of aerodynamic diameter <2.0μm and >3.5μm decreased significantly. By SMPS observation, particle number concentration was mainly concentrated in 30 nm~300 nm of aerodynamic diameter and had obvious diurnal variation during the formation and maintaining of fog/haze, the time of large particle number concentration appeared from 8 a.m. to 2 p.m and from 6 p.m to 2 a.m. The increase of pollutant concentration was mainly related to the increase of number concentration of aerodynamic diameter>140 nm. The increase of scatter coefficient was related to the increase of number concentration of aerodynamic diameter<1.0μm. This was one of the important factors which caused the visibility deterioration. ©, 2015, Chinese Society for Environmental Sciences. All right reserved.


Du C.-L.,Meteorological Institute of Shaanxi Province | Yu X.,Meteorological Institute of Shaanxi Province | Li X.-M.,Meteorological Institute of Shaanxi Province | Chen C.,Meteorological Institute of Shaanxi Province | And 4 more authors.
Research of Environmental Sciences | Year: 2013

Black carbon (BC) is one of the most important research fields in aerosol climate effect studies due to its strong absorption effect. Compared to early international efforts, systematic BC observations were started late since 1990s' in several cities of China. The variation and particle size characteristics and their causing factors of BC concentration were analyzed based on data collected at Jinghe station, suburban of Xi'an, during autumn and winter (October 1st, 2008-February 28, 2009). The station is suitable for BC characteristics study since it is far from downtown area without main BC source nearby. The observational data included BC and particle concentration data collected by atmospheric elements station, meteorological variables collected by automatic meteorological station and sounding station. Results showed that: 1) suburban has lower BC concentration than urban area; Contrast to tri-peak diurnal cycle at urban area, suburban showed double-peak characteristic with maximum values of 5.5 μg/m3 (09:00 o'clock) and 6.1 μg/m3 (23:00 o'clock). The two corresponding trough values were 4.9 μg/m3 (06:00 o'clock) and 2.6 μg/m3 (16:00 o'clock), respectively; 2) Relationship between BC concentration and particle size varied with particle sizes. The BC concentration was directly proportional to ultrafine particles and inversely proportional to big particles (e.g. dust). Dust affects measurement of BC concentration; 3) BC concentration was significantly related with temperature inversion near the ground (correlation coefficient). Wind speed had different effects in the processes of transport and diffusion of BC. Continuous precipitation had remarkable removal effects to BC. The increasing BC concentration during autumn could be contributed by the burning of crop stalks during the harvest seasons. In December and January, residential heating through burning coal and firewood by simple equipment caused relative high BC concentration. The reasons for lowest BC concentration in February were particles removal by precipitation (rain and snow) and dispersal by strong wind. Diurnal cycle of BC concentration reflected local BC emission variation and was affected by planetary boundary layer height. These results are useful to further studies of atmospheric environmental pollution and aerosol climate effect for other inland cities in the northwest of China.


Rosenfeld D.,Hebrew University of Jerusalem | Yu X.,Meteorological Institute of Shaanxi Province | Liu G.,Meteorological Institute of Shaanxi Province | Xu X.,Meteorological Institute of Shaanxi Province | And 6 more authors.
Geophysical Research Letters | Year: 2011

Heavy aerosol loads have been observed to suppress warm rain by reducing cloud drop size and slowing drop coalescence. The ice forming nuclei (IFN) activity of the same aerosols glaciate the clouds and create ice precipitation instead of the suppressed warm rain. Satellite observations show that desert dust and heavy air pollution over East Asia have similar ability to glaciate the tops of growing convective clouds at glaciation temperature of Tg < ∼-20°C, whereas similarly heavy smoke from forest fires in Siberia without dust or industrial pollution glaciated clouds at Tg ≤-33°C. The observation that both smoke and air pollution have same effect on reducing cloud drop size implies that the difference in Tg is due to the IFN activity. This dependence of Tg on aerosol types appears only for clouds with re-5 < 12 μm (re-5 is the cloud drop effective radius at the-5°C isotherm, above which ice rarely forms in cloud tops). For the rest of the clouds the glaciation temperature increases strongly with re-5 with little relation to the aerosol types, reaching Tg> ∼-15°C for the largest re-5, which are typical to marine clouds in pristine atmosphere. Copyright 2011 by the American Geophysical Union.


Zhu Y.,Meteorological Institute of Shaanxi Province | Rosenfeld D.,Hebrew University of Jerusalem | Yu X.,Meteorological Institute of Shaanxi Province | Liu G.,Meteorological Institute of Shaanxi Province | And 2 more authors.
Geophysical Research Letters | Year: 2014

The advent of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-Orbiting Partnership (NPP) satellite provided a quantum jump in the satellite capabilities of retrieving cloud properties, because it nearly tripled the resolution in the thermal channels (375 m). This allowed us to develop a methodology for retrieving convective cloud base temperature (Tb) and validate it over the Atmospheric System Research Southern Great Plains site for the satellite early afternoon overpass time. The standard error of the Tb retrieval was only 1.1°C. The knowledge of Tb allows the calculation of cloud base height and the depth of the boundary layer, as well as the boundary layer water vapor mixing ratio with an accuracy of about 10%. The feasibility of retrieving cloud base temperature and height is an essential component that is required for retrieving cloud condensation nuclei (CCN) from satellites by using convective clouds as natural CCN chambers. Key Points Convective cloud base temperature was retrieved from satellite with 1°C accuracy Boundary layer vapor mixing ratio was retrieved with 10% accuracy This became possible by using the 375 m resolution of the NPP/VIIRS Imager ©2014. American Geophysical Union. All Rights Reserved.

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