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Bian L.,Chinese Academy of Meteorological Sciences | Gao Z.,CAS Institute of Atmospheric Physics | Gao Z.,Nanjing University of Information Science and Technology | Ma Y.,Chinese Academy of Meteorological Sciences | And 7 more authors.
Journal of the Meteorological Society of Japan

The Tibetan field observatories, which are constructed in a project of the Japan International Co-operation Agency in 2007, provide an opportunity to establish four observation sites equipped with same sensors on and around Tibetan plateau for better understanding the monsoon climate features over the Tibetan plateau. By using same analyzing technique, the present paper examines the seasonal and diurnal variations in (1) radiation components, (2) turbulent momentum, heat, water vapor, and CO2 fluxes, and (3) soil temperature, moisture, and heat flux of the four homogenous sites (BJ at Bu-Jong (Naqu), DL at Da-Li, LZ at Lin-Zhi, and WJ at Wen-Jiang) on and around the Tibetan Plateau, in 2008. Seasonal variation in the sensible heat flux at the BJ site indicate that the sensible heat flux was stronger thereat compared with other sites in spring (March to May). After the monsoon had set, sensible heat flux decreased in all four sites. On the other hand, the seasonal variations in latent heat flux suggest that the latent heat flux increases rapidly with the water content in the soil that rises from March to June at the LZ, DL, and WJ sites. An annual cyclic pattern of CO2 flux at sites DL and WJ was obvious. Finally, At the sparsely vegetated BJ site the seasonal variation in CO2 flux was small due to the limited CO2 absorption in summer and its subsequent limited release in other seasons; and at the very grassy LZ site, the CO2 absorption responds to seasonal march of monsoon. Energy partitioning dramatically responds to the onset of monsoon at the BJ site. © 2012, Meteorological Society of Japan. Source

Li Y.-P.,China West Normal University | Zhou H.,China West Normal University | Zhang Z.-S.,South China Institute of Environmental Sciences | Wang Q.-Y.,Xian Jiaotong University | Luo L.,Chengdu Institute of Plateau Meteorology
Huanjing Kexue/Environmental Science

A total of 131 samples of PM2.5 were collected at urban area of Chengdu from April, 2009 to January, 2010. The secondary water-soluble inorganic ions (NH4 +, NO3 - and SO4 2-) in PM2.5were determined to study the pollution characteristics by Ion Chromatography method. The results showed the NH4 +, NO3 - and SO4 2- concentrations were (10.4 ± 8.6), (19.7 ± 14.6) and (32.8 ± 21.8) μg·m-3, accounting for (5.5 ± 2.8)%, (11.1 ± 3.5)% and (19.3 ± 6.4)% of PM2.5, respectively, and the sum of these three ions accounted for (35.9 ± 12.7)%. Meanwhile, the seasonal characteristics of secondary inorganic ions were obvious. The seasonal concentrations order of secondary inorganic components was SO4 2- > NO3 - > NH4 + in summer and winter, and the proportion of secondary inorganic ions of PM2.5 was 39.4% in summer and 44.3% in winter. The results of Correlation Analysis showed that most of NH4 +, NO3 - and SO4 2- existed as NH4HSO4, (NH4)2SO4 and NH4NO3 in Chengdu. And the average ratio of NO3 -/SO4 2- indicated that the main source of sulfur and nitrogen in the atmosphere was given priority to a fixed source. In addition, the sulfate oxidizing rate (SOR) and nitrate oxidizing rate (NOR) were 0.33 ± 0.12 and 0.19 ± 0.09, respectively. It showed that SO4 2- and NO3 - in PM2.5were due to the secondary transformation. Source

Yang X.-B.,Chengdu Institute of Plateau Meteorology | Ma Z.-F.,Chengdu Institute of Plateau Meteorology | Wang D.-Y.,University of New Brunswick | Wang D.-Y.,Qujing Normal University | Yan H.-S.,Yunnan University
Journal of Atmospheric and Solar-Terrestrial Physics

The spatio-temporal variations of major meridional modes are studied by using the ECMWF and NCEP/NCAR reanalyzed geopotential data between 70 and 10. hPa during 1979 and 2001. The variance contribution rates from the first and second modes are 56-69% and 14-22%, respectively, for ECMWF, but 76-85% and 9-10% for NCEP/NCAR. The climatic trend coefficients are positive and negative in the troposphere and stratosphere, respectively. The reversal is remarkably correlated with the AO/NAM, AAO/SAM and polar vortex, suggesting their important role in connecting the mid-low and upper circulation and the interaction between SH and NH. © 2010 Elsevier Ltd. Source

Wang W.,University of Sichuan | Wang W.,Chengdu Institute of Plateau Meteorology | Hu S.,University of Sichuan | Hu S.,East Stroudsburg University | Li Y.,Chengdu Institute of Plateau Meteorology
Water Resources Management

Synthetic generation of daily streamflow sequences is one of the most critical issues in stochastic hydrology. In this study, a new wavelet transform method is developed for synthetic generation of daily streamflow sequences. Firstly, daily streamflow sequences with different frequency components are decomposed into the series of wavelet coefficients W1(t), W2(t),...,WP(t) and scale coefficients (the residual) CP(t) at a resolution level P using wavelet decomposition algorithm. Secondly, the series of W1(t), W2(t),...,WP(t) and CP(t) are divided into a number of sub-series based on a yearly period. Thirdly, random sampling is performed from sub-series of W1(t), W2(t),...,WP(t) and CP(t), respectively. Based on these sampled sub-series, a large number of synthetic daily streamflow sequences are obtained using wavelet reconstruction algorithm. The advantages of this newly developed method include: (1) it is a nonparametric approach; (2) it is able to avoid assumptions of probability distribution types (Normal or Pearson Type III) and of dependence structure (linear or nonlinear); (3) it is not sensitive to the original data length and suitable for any hydrological sequences; and (4) the generated sequences from this method could capture the dependence structure and statistical properties presented in the data. Finally, a case study in Jinsha River, China, indicates that the new method is valid and efficient in generating daily streamflow sequences based on historical data. © 2010 Springer Science+Business Media B.V. Source

Jin J.-L.,Chengdu Institute of Plateau Meteorology | Jin J.-L.,Hefei University of Technology | Wei Y.-M.,Beijing Institute of Technology | Zou L.-L.,CAS Institute of Policy and Management | And 3 more authors.
Natural Hazards

Early warning for sustainable utilization of regional water resources is an important control measure for regional water security management. To establish operable and quantitative forewarning model, in this paper, a new forewarning model for sustainable utilization of water resources based on BP neural network and set pair analysis (named BPSPA-FM for short) was established. In the proposed approach, the accelerating genetic algorithm-based fuzzy analytic hierarchy process was suggested to determine the weights of evaluation indexes, back-propagation neural network updating model was used to predict the values of the evaluation indexes, and the set pair analysis was used to determine the function values of relative membership in variable fuzzy set of the samples. BPSPA-FM was applied to early warning for sustainable utilization of regional water resources of Yuanyang Hani terrace in Yunnan Province of China. The results show that the states of sustainable utilization in this system were near the critical value between nonalarm and slight alarm from 1990 to 2000, the states of the system fell into slight alarm and were rapidly close to intermediate alarm from 2001 to 2004, and the states of the system were predicted to be near the critical value between slight alarm and intermediate alarm from 2005 to 2010. The main alarm indexes of the system were utilization ratio of water in agriculture, control ratio of surface water, per capita water supply, per unit area irrigation water and per capita water consumption. BPSPA-FM can take full advantage of the changing information of the evaluation indexes in adjacent periods and the relationship between the samples and the criterion grades. The results of BPSPA-FM are reasonable with high accuracy. BPSPA-FM is general and can be applied to early warning problems of different natural hazards systems such as drought disaster. © Springer Science+Business Media B.V. 2011. Source

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