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Tropical cyclone rainfall in the Mekong River Basin for 1983–2016
Chen, Aifang,Ho, Chang-Hoi,Chen, Deliang,Azorin-Molina, Cesar Elsevier 2019 Atmospheric research Vol.226 No.-
<P><B>Abstract</B></P> <P>As home to about 70 million people, the Mekong River Basin (MRB), located in Mainland Southeast Asia, is often influenced by tropical cyclones (TCs) landfalling. The TCs not only cause flood and storm hazards, but also play important roles in providing freshwater resource and welcomed sediment transports. Our study focuses on the climatology of TCs and associated rainfall (TCR) in the MRB for 1983–2016. Results show that: (i) the mean landfall occurrence of TCs is 6.2 yr<SUP>−1</SUP>, leading to 36.7 mm yr<SUP>−1</SUP> of annual mean TCR (2.5% of the annual total precipitation), which mainly occur in monsoon-TC season (i.e., June–November); (ii) TCs highly concentrate on the lower eastern MRB, generating the largest TCR contribution of 12.4% to the annual total precipitation; (iii) the annual mean contribution of TCs induced extreme precipitation - R20mm and R50mm (days of heavy precipitation rate ≥20 mm day<SUP>−1</SUP> and ≥50 mm day<SUP>−1</SUP>, respectively) - to that from annual total precipitation is large in the lower eastern MRB; (iv) over 60% of the basin area is influenced by TCR on average; and (v) a significant weakening trend of the TC frequency has been observed. The present findings lay a foundation for further in-depth research of the potential influence of the dynamic TCs and the associated rainfall in the MRB.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Annual mean tropical cyclone landfall is 6.2 yr<SUP>−1</SUP> in the Mekong River Basin. </LI> <LI> Annual mean tropical cyclone rainfall contributes to 2.5% of annual total precipitation. </LI> <LI> Tropical cyclone highly concentrates on the lower eastern basin. </LI> <LI> Tropical cyclone contributes largely to extreme precipitation. </LI> <LI> A significant weakening trend of tropical cyclone occurrences is observed. </LI> </UL> </P>
Single-crystalline tungsten oxide nanoplates
Deliang Chen,Hailong Wang,Rui Zhang,Lian Gao,Yoshiyuki Sugahara,Atsuo Yasumori 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6
Tungsten oxide nanocrystals are important semiconductor materials with a suitable energy band gap (ca. 2.5 eV) for visible-light utilization. Though there are a great amount of reports on the synthesis of WO3 nanocrystals, no effective routes to two-dimensional (2D) WO3 nanocrystals have been reported. We here developed a novel and efficient route to synthesize free-standing single-crystalline WO3 nanoplates on a large scale and in a repeatable way. The proposed route involved a rational transformation of tungstatebased inorganic-organic hybrid nanobelts to single-crystalline WO3·H2O nanoplates, and then to single-crystalline monoclinic WO3 nanoplates with an inhibited crystal growth direction of [004]. The sizes of the as-obtained WO3 nanoplates are (200-500) nm × (200-500) nm × (10-30) nm. The WO3 nanoplates as-synthesized have high specific surface areas (up to 180m2 g−1) and showed remarkably enhanced visible-light photocatalytic properties in water splitting for O2 generation. Tungsten oxide nanocrystals are important semiconductor materials with a suitable energy band gap (ca. 2.5 eV) for visible-light utilization. Though there are a great amount of reports on the synthesis of WO3 nanocrystals, no effective routes to two-dimensional (2D) WO3 nanocrystals have been reported. We here developed a novel and efficient route to synthesize free-standing single-crystalline WO3 nanoplates on a large scale and in a repeatable way. The proposed route involved a rational transformation of tungstatebased inorganic-organic hybrid nanobelts to single-crystalline WO3·H2O nanoplates, and then to single-crystalline monoclinic WO3 nanoplates with an inhibited crystal growth direction of [004]. The sizes of the as-obtained WO3 nanoplates are (200-500) nm × (200-500) nm × (10-30) nm. The WO3 nanoplates as-synthesized have high specific surface areas (up to 180m2 g−1) and showed remarkably enhanced visible-light photocatalytic properties in water splitting for O2 generation.
Fu Yang,Gang Chen,Yu Kang,Dongmin Ma,Qilin Chen,Tian Tao,Fu Deliang 한국지질과학협의회 2020 Geosciences Journal Vol.24 No.2
The U-Pb ages of single zircon grains contained in the sandstone samples were analyzed by the LA-ICP-MS method, the sediment provenances and geological significance were discussed. The LA-ICP-MS zircon U-Pb dating from the sandstones, tuffaceous sandstones and volcanic tuffs of the Pingliang and Zhaolaoyu Formations along the southwestern Ordos Block are used to limit the maximum depositional age and material sources. The results show that: (1) The youngest ages of zircon dating in the three samples are 445 Ma, 444 Ma and 443 Ma, respectively, suggesting that the studied Formations were deposited in the Late Ordovician. (2) The detrital zircon U-Pb age analysis of the sandstones sample from the Pinliang Formation clustered in the 445–477 Ma, 588–1548 Ma and 1612–2496 Ma with the corresponding youngest peak age of 454.5 ± 3.3 Ma. (3) The distribution of zircon U-Pb age in sandstone samples showing that the sedimentary rocks detritus was mainly sourced from the North Qinling-Qilian terranes and the NCC, and has double provenance supply in the north and south. The material source of the tuffaceous sandstones and volcanic tuffs mainly comes from the volcanic and magmatic activity related to the North Qilian-North Qinling Island Arcs.
Impact of Synoptic Weather Types on Ground-Level Ozone Concentrations in Guangzhou, China
Wenhui Liao,Luolin Wu,Shengzhen Zhou,Xuemei Wang,Deliang Chen 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.2
Although precursor concentrations were reduced by emission control in Guangzhou, southern China from 2006 to 2016, ground-level O3 concentrations increased, forming potential risks to human health. This study explored the impacts of large-scale synoptic weather circulations on O3 concentration in Guangzhou, in a particular focus on high O3 pollution episodes. Twelve local weather types were clustered based on Lamb-Jenkinson weather types (LWTs). Analyses showed that LWTs strongly impacted daily O3 concentrations: A, AS, CN, and N+ weather types were likely associated with high ozone concentrations, while the ozone levels were relatively low under C, CE, CS, and S+ types. LWTs could explain 30–40% of the inter-annual variability of O3 concentration during the dry season. Numerical model simulations further demonstrated that continuous type A weather was the leading LWT correlated with high O3 concentrations, while type C weather was the predominant type correlated with low O3 concentrations. CMIP5 model results showed that occurrences of weather type A would increase by about 25% in the high emission scenario over the 2020–2069 period, which might worsen the O3 pollution in Guangzhou in the future. The increase in frequency weather type A would not be significant under the low emission scenario during the same period. Therefore, we should strictly implement the global emission reduction plan to prevent the change of weather circulation caused by climate change from aggravating ozone pollution in the future. The strong link between O3 concentrations and LWT frequencies makes the daily occurrence of LWTs a useful predictor for episodes of high O3 pollution and makes annual frequencies of LWTs good indicators of the inter-annual variability of the O3 concentration. These results are useful in efforts to predict O3 concentrations, providing a reliable weather forecast is available.