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Zheng D.,Chinese Academy of Meteorological Sciences | Zhang Y.,Chinese Academy of Meteorological Sciences | Lu W.,Chinese Academy of Meteorological Sciences | Dong W.,Chinese Academy of Meteorological Sciences | And 2 more authors.
2011 7th Asia-Pacific International Conference on Lightning, APL2011 | Year: 2011

The current measurements of 17 return strokes (RSs) produced by 6 classical triggered lightning flashes (TLFs) conducted in Guangdong, China from 2008 to 2010 were analyzed for the first time in this study. The geometric mean (GM) value of the peak value current (I Peak) is 16.59 kA, the half-peak width (t HPW) is 21.91 μs, the 10-90% risetime (t 10-90%) is 0.45 μs, the 10-90% average gradient (G 10-90%) is 29.61 kA μs -1, the maximum gradient (G Max) is 55.89 kA μs -1, the charge transfer in 1ms after the beginning of the return strokes (Q 1ms) is 1.61 C, and the action integral in 1ms after the beginning of the return strokes (AI 1ms) is 6.60×10 3 A 2 s. The RSs in GCOELD are, on average, stronger than those reported by other authors referenced in this study. The peak value current has a general good linear relation with G 10-90% (determination coefficient (R 2) = 0.64), a good linear relation with G Max (R 2=0.74), a strong power function relation with Q 1ms (R 2=0.89), and an excellent logarithmic function relation with AI 1ms (R 2=0.92). Additionally, the current of the initial-stage return stroke (ISRS) of an altitude TLF was analyzed and found to have small t HPW (2.12 μs), charge transfer (36.37 mC) and action integral (181.56 A 2 s), but was similar to other RSs for all other parameters. After the ISRS, a number of chopped-shape pulses, attributed to the back-and-forth reflections of the ISRS current, were recorded and analyzed for their characteristics. © 2011 IEEE. Source

Hu S.,Hunan University | Song L.,Guangdong Meteorological Bureau | Li Q.,Hunan University | Li Q.,City University of Hong Kong
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2011

Mean wind speed and wind turbulence characteristics of typhoon winds in surface boundary layer were studied based on three-dimensional wind data, which were recorded from ultrasonic anemometers at 10m height at sites near seashore during land falling of Typhoons Damrey, Chunchu and Paipiroon. The relations among turbulence parameters such as power law index, friction velocity, turbulence intensities and gust factor were analyzed under different types of upwind terrains based on the field measurements results. The results of the analysis reveal that friction velocity strongly depends on mean wind speed, which increases with increasing wind speed. Power law index and turbulence intensities decrease with the increasing of wind speed. Gust factor increases with the increasing of turbulence intensities. By fitting the results of turbulence parameters, the relations among the parameters were proposed which will be useful for the wind resistant design of low rise buildings in typhoon-prone regions. Source

Ju Y.,Nanjing University | Ju Y.,South China Institute of Environmental Sciences | Fang J.,South China Institute of Environmental Sciences | Liu X.,South China Institute of Environmental Sciences | And 9 more authors.
Journal of Hazardous Materials | Year: 2011

Aqueous crystal violet (CV) solutions containing P25-TiO2 photocatalyst were irradiated with ultraviolet-visible (UV-vis) light from two microwave-powered electrodeless discharge lamps (EDL-2). The results demonstrated that approximately 94.4% of CV was effectively removed after 3min of irradiation, with a pseudo-first order kinetic constant of 0.838min-1. According to 32 kinds of products, a five-step degradation pathway of CV was proposed. Further investigations showed that (1) three kinds of N-demethylated products and 4-dimethylaminobenzophenone (DLBP) were the main intermediates; (2) malachite green (MG) and leuco-crystal violet could not be generated by N-demethylation and phototransformation reactions, respectively; (3) bis(4-(dimethylamino)phenyl)methanone preferentially generated via decomposition of the conjugated structure of CV could be further N-demethylated into DLBP. Moreover, the unique degradation pathways of CV and MG were ascribed to the different substituents on the conjugated structures. Additionally, the cost and kinetic constant of different processes was also evaluated, and the results indicated the feasibility of this method for treatment of CV in field situations. © 2010 Elsevier B.V. Source

Fong S.-K.,Macau Geophysical and Meteorological Bureau | Wu C.-S.,Sun Yat Sen University | Wang T.,Guangdong Meteorological Bureau | He X.-J.,Guangdong Meteorological Bureau | And 4 more authors.
Journal of Tropical Meteorology | Year: 2012

The multiple time scale climate changes are studied and calculated with statistical analysis and wavelet transformation on the basis of daily series of observed data over the period 1901-2007 in Macau. The result shows that statistically significant oscillations with 2 to 5 years of period generally exist in the series of climate variables (e.g. annual mean surface air temperature and precipitation as well as evaporation etc.), but with obvious locality in time domain. The variation of annual mean surface air temperature has a quasi 60-year period. The phases of the 60-year variation approximately and consistently match that of Atlantic Multidecadal Oscillation (AMO). The oscillations of seasonal mean surface air temperature in summer and winter have the periods of quasi 30-year and quasi 60-year, respectively. These two periods of oscillations have statistically significant correlation with Pacific decadal oscillation (PDO) and AMO, individually. The multidecadal variations of the precipitation of the annually first flood period and annual evaporation are dominated by periods of quasi 30-year and quasi 50-year, respectively. Source

Fong S.,Macao Geophysical and Meteorological Bureau | Wu C.,Sun Yat Sen University | Wang A.,Sun Yat Sen University | He X.,Guangdong Meteorological Bureau | And 4 more authors.
Advances in Climate Change Research | Year: 2010

Change related to climate in Macao was studied on the basis of daily temperature observations over the period 1901-2007. The result shows that annual mean surface air temperature in Macao as a whole rose with a warming rate of about 0.066 °C per 10 years in the recent 107 years. The most evident warming occurred in spring and winter. The inter-decadal variations of the seasonal mean temperature in summer and winter appeared as a series of waves with a time scale of about 30 years and 60 years, respectively. The annual mean minimum temperature increased about twice as fast as the annual mean maximum temperature, resulting in a broad decline in the annual mean diurnal range. The interde-cadal variations of annual mean maximum temperature are obviously different from those of annual mean minimum temperature. It appears that the increase in the annual mean maximum temperature in the recent 20 years may be part of slow climate fluctuations with a periodicity of about 60 years, whereas that in the annual mean minimum temperature appears to be the continuation of a long-term warming trend. Source

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