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Ren G.-Y.,Nanjing University of Information Science and Technology | Ren G.-Y.,National Climate Center | Zhang L.,Nanjing University of Information Science and Technology | Zhang L.,National Climate Center | And 4 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2015

With rapid growth of economy and expansion of cities, urbanization has become a significant factor in affecting the long-term changes of mean and extreme temperature and other key climatic variablesat most urban stations of mainland China. So far, this problem has aroused more and more attentions in urbanization effect on mean temperature trends, but the few analysis of urbanization effect on temperature probability density distribution has been done. This article analyzes the urbanization effect on daily temperature probability density distribution (PDF), daily temperature cumulative probability density distribution (CDF) and the seasonal cycles of daily mean temperature for Shijiazhuang weather station without any relocation before 2011 as an example. This paper uses daily data of Tmean, Tmin and Tmax of an urban weather station, Shijiazhuang station, and a nearby rural weather station, Gaocheng station, from 1962 to 2011. Shijiazhuang station was never moved before 2011.Urbanization effect (ΔTur) is defined as the temperature trends or change in daily temperature PDF and CDF of urban station caused by the changing Urban Heat Island (UHI) intensity and/or the effect of other factors (such as aerosols). The urbanization makes the distribution of annual Tmean, Tmin and Tmax at Shijiazhuang station during 1962-2011 shift to high temperature side. Urbanization effect on the distribution of annual Tmin is very obvious, but the effect on the distribution of annual Tmax is small. Due to the urbanization effect, the increase in Tmin is larger on high value side than on low value side at Shijiazhuang station, resulting in a flatter shape of annual Tmin PDF than that of the rural station; The PDF of Tmean, Tmin and Tmax at Shijiazhuang station all shifts to the higher value side during 1987-2011 compared to 1962-1986, with the largest shift occurring in Tmin. The PDF of Tmin at Shijiazhuang station in the time period 1962-2011 is characterized by a non-normal distribution due to the urbanization effect. The difference of PDF between Shijiazhuang station and Gaocheng station during 1962-2011 is larger and more significant in winter and spring than in summer and autumn, and the largest difference is found for winter Tmin. The urbanization effect in the 1962-2011 series of cold nights and warm nights are respectively -1.13 d/10a and 1.48 d/10a, and the urbanization contribution are respectively 28.32% and 37.76%. The urbanization effects in the Tmin-based extreme temperature indicesare larger for those in the Tmax-based extreme temperature indices at Shijiazhuang station. In each of the seasons of a year, the daily mean Tmin difference between the urban and rural stations is generally more than 1.0℃, with the daily urban heat island intensity, sometimes reaching above 1.5℃, being the largest from the beginning of December to the end of May, and the daily mean Tmax difference between the urban and rural stations is usually less than 0.5℃. The significant urbanization effect on urban station surface air temperature records exists not merely in the linear trends of mean temperature series and extreme temperature indices series, but also in the probability density distribution of daily Tmin and Tmean. It is an important factor in forming the asymmetry changes of diurnal and seasonal temperature cycles for Shijiazhuang station. ©, 2015, Science Press. All right reserved. Source

Zhai Q.-F.,Nanjing University of Information Science and Technology | Jin L.-J.,Nanjing University of Information Science and Technology | Lin Z.-Y.,Nanjing University of Information Science and Technology | Wu Z.-H.,Weather Modification Office of Hebei Province | Kuang S.-S.,Shijiazhuang Meteorological Bureau
Zhongguo Huanjing Kexue/China Environmental Science | Year: 2011

During May, 2010, number concentration of atmospheric aerosols near the ground at Shijiazhuang Meteorological Bureau, China were measured using WPS made by MSP Corporation in United States, combined with corresponding meteorological data, to study the characteristics of aerosol number concentration and size distribution in this observation and possible causes that lead to. The spectra of aerosol were mainly occupied by ultrafine particles(DP<0.1 μm) in this observation. The average particle number concentration was high in all size scales. High emission of pollution gases and particles, weak wind condition and the transport effect when the dominant wind direction was southeast were the primary possible causes of this result. Obvious diurnal variation of aerosol concentration was observed in sunny days, which was mainly controlled by solar radiation, heat condition, the height of the boundary layer and construction, and that between different diameters had significant differences. Both total and ultrafine particles number concentration reached daily peak value at 7:00, 12:00 and 21:00, while coarse particles (DP>0.1 μm) number concentration reached the peak value at 7:00 and 23:00. Source

Zhang Y.,Nanjing University of Information Science and Technology | Yin Y.,Nanjing University of Information Science and Technology | Xiao H.,Nanjing University of Information Science and Technology | Kuang S.-S.,Shijiazhuang Meteorological Bureau | Wu Z.-H.,Hebei Weather Modification Office
Zhongguo Huanjing Kexue/China Environmental Science | Year: 2012

The data measured by a three-wavelength integrating nephelometer, a PCASP-X2 and a visibility meter over Shijiazhuang, Hebei Province, China, from May 7~23, 2010, were used to investigate the scattering properties of aerosol particles and the relationship with particle size spectra, visibility and meteorological conditions. The results show that the scattering coefficients were (257±293), (199±237), and (143±173) Mm -1, respectively, for the three wavelengths, 450, 550 and 700 nm, and that the values varied significantly from day to day, while the microphysical property of aerosol is stable. It was also found that the daily variation of the aerosol scattering coefficient was a tri-peak shape, with the coefficient reaching peak values at about 8, 13 and 0 o'clock, respectively, and higher values were measured during nighttime. There was also a significant difference in the mean scattering coefficient under different weather conditions, with the mean value (524.9Mm -1) of overcast days was 4.7 times higher than that of fine days (112.3Mm -1). The ratios of backscattering coefficient to the total scattering coefficient of three wavelengths were all larger than 0.15, indicating that a significant fraction of the particular matter in Shijiazhuang was attributed to fine mode particles. There existed a positive correlation between the scattering coefficient and the volume concentration of aerosol, but sometimes when the volume concentration was large, the scattering coefficient was small, maybe because of the local emission source or meteorological condition. There was a negative correlation between the scattering coefficient and visibility. Our results also find that the scattering coefficient would exhibit two different trends when the relative humidity increases, and the local wind direction and speed could also influence the scattering properties of aerosol. Source

Ren G.,National Climate Center | Li J.,National Climate Center | Ren Y.,National Climate Center | Chu Z.,Beijing Municipality Meteorological Bureau | And 7 more authors.
Journal of Applied Meteorology and Climatology | Year: 2015

Trends in surface air temperature (SAT) are a critical indicator for climate change at varied spatial scales. Because of urbanization effects, however, the current SAT records of many urban stations can hardly meet the demands of the studies. Evaluation and adjustment of the urbanization effects on the SAT trends are needed, which requires an objective selection of reference (rural) stations. Based on the station history information from all meteorological stations with long-term records in mainland China, an integrated procedure for determining the reference SAT stations has been developed and is applied in forming a network of reference SAT stations. Historical data from the network are used to assess the urbanization effects on the long-term SAT trends of the stations of the national Reference Climate Network and Basic Meteorological Network (RCN+BMN or national stations), which had been used most frequently in studies of regional climate change throughout the country. This paper describes in detail the integrated procedure and the assessment results of urbanization effects on the SAT trends of the national stations applying the data from the reference station network determined using the procedure. The results showed a highly significant urbanization effect of 0.074°C (10 yr)-1 and urbanization contribution of 24.9% for the national stations of mainland China during the time period 1961-2004, which compared well to results that were reported in previous studies by the authors using the predecessor of the present reference network and the reference stations selected but when applying other methods. The authors are thus confident that the SAT data from the updated China reference station network as reported in this paper best represented the baseline SAT trends nationwide and could be used for evaluating and adjusting the urban biases in the historical data series of the SAT from different observational networks. © 2015 American Meteorological Society. Source

Luo Y.,Chinese Academy of Meteorological Sciences | Qian W.,Shijiazhuang Meteorological Bureau | Zhang R.,Chinese Academy of Meteorological Sciences | Zhang D.-L.,Chinese Academy of Meteorological Sciences | Zhang D.-L.,University of Maryland College Park
Journal of Hydrometeorology | Year: 2013

Heavy rainfall hit the Yangtze-Huai Rivers basin (YHRB) of east China several times during the prolonged 2007 mei-yu season, causing the worst flood since 1954. There has been an urgent need for attaining and processing high-quality, kilometer-scale, hourly rainfall data in order to understand the mei-yu precipitation processes, especially at the mesob and smaller scales. In this paper, the authors describe the construction of the 0.078-resolution gridded hourly rainfall analysis over the YHRB region during the 2007 mei-yu season that is based on surface reports at 555 national and 6572 regional automated weather stations with an average resolution of about 7 km. The gridded hourly analysis is obtained using a modified Cressman-type objective analysis after applying strict quality control, including not only the commonly used internal temporal and spatial consistency and extreme value checks, but also verifications against mosaic radar reflectivity data. This analysis reveals many convectively generated finescale precipitation structures that could not be seen from the national station reports. A comprehensive quantitative assessment ensures the quality of the gridded hourly precipitation data. A comparison of this dataset with the U.S. Climate Prediction Center morphing technique (CMORPH) dataset on the same resolution suggests the dependence of the latter's performance on different rainfall intensity categories, with substantial underestimation of the magnitude and width of the mei-yu rainband as well as the nocturnal and morning peak rainfall amounts, due mainly to its underestimating the occurrences of heavy rainfall (i.e., .10mmh-1). © 2013 American Meteorological Society. Source

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