Eurasian Snow Cover Variability and Its Association with Summer Rainfall in China   总被引：13，自引：0，他引：13  

WU Bingyi  YANG Kun  ZHANG Renhe 《大气科学进展》2009,26(1):31-44

This study investigates the statistical linkage between summer rainfall in China and the preceding spring Eurasian snow water equivalent (SWE), using the datasets of summer rainfall observations from 513 stations, satellite-observed snow water equivalent, and atmospheric circulation variables in the NCEP/NCAR re-analysis during the period from 1979 to 2004. The first two coupled modes are identified by using the singular value decomposition (SVD) method. The leading SVD mode of the spring SWE variability shows a coherent negative anomaly in most of Eurasia with the opposite anomaly in some small areas of the Tibetan Plateau and East Asia. The mode displays strong interannual variability, superposed on an interdecadal variation that occurred in the late 1980s, with persistent negative phases in 1979--1987 and frequent positive phases afterwards. When the leading mode is in its positive phase, it corresponds to less SWE in spring throughout most of Eurasia. Meanwhile, excessive SWE in some small areas of the Tibetan Plateau and East Asia, summer rainfall in South and Southeast China tends to be increased, whereas it would be decreased in the up-reaches of the Yellow River. In recent two decades, the decreased spring SWE in Eurasia may be one of reasons for severe droughts in North and Northeast China and much more significant rainfall events in South and Southeast China. The second SVD mode of the spring SWE variability shows opposite spatial variations in western and eastern Eurasia, while most of the Tibetan Plateau and East Asia are in phase. This mode significantly correlates with the succeeding summer rainfall in North and Northeast China, that is, less spring SWE in western Eurasia and excessive SWE in eastern Eurasia and the Tibetan Plateau tend to be associated with decreased summer rainfall in North and Northeast China.  相似文献   

The time and frequency standard system for FAST receivers     

朱凯  范瑾  Kun Liang  Wei Tang  Zhi-Sheng Gao  Yan Zhu  Yi Feng  Wei-Wei Zhu  Lei Qian  You-Ling Yue  Jin-You Song  Xiang-Wei Shi  Xing-Yi Wang  Ming-Lei Guo  Hang Zhang  Heng-Qian Gan  Hong-Fei Liu  Cheng-Jin Jin  Peng Jiang 《天文和天体物理学研究(英文版)》2020,(5):148-154

This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The stability and drift rate of the frequency standard are calculated using 1-year monitoring data.The UTC-NIM Disciplined Oscillator(NIMDO)system improves the system time accuracy and stability to the level of 5 ns.Pulsar timing observations were carried out for several months.The weighted RMS of timing residuals reaches the level of less than 3.0μs.  相似文献   

Microphysical Characteristics of Extreme-Rainfall Convection over the Pearl River Delta Region,South China from Polarimetric Radar Data during the Pre-summer Rainy Season     

Hao HUANG  Kun ZHAO  Johnny C.L.CHAN  Dongming HU 《大气科学进展》2023,40(5):874-886

During the pre-summer rainy season, heavy rainfall occurs frequently in South China. Based on polarimetric radar observations, the microphysical characteristics and processes of convective features associated with extreme rainfall rates(ERCFs) are examined. In the regions with high ERCF occurrence frequency, sub-regional differences are found in the lightning flash rate(LFR) distributions. In the region with higher LFRs, the ERCFs have larger volumes of high reflectivity factor above the freezin...  相似文献   

Preface to the Special Issue on the 14th International Conference on Mesoscale Convective Systems and High-Impact Weather     

Zhemin TAN  Qinghong ZHANG  Xudong LIANG  Kun ZHAO  Xin XU  Lili LEI 《大气科学进展》2023,40(5):745-746

<正>A mesoscale convective system (MCS) is an organized cluster of thunderstorms known to be the most important convective mode in causing disastrous high-impact weather, such as heavy rainfall, hail, damaging winds, and tornadoes. The small spatial scale and fast temporal evolution of MCSs make their observation and prediction very challenging. East Asia is home to the world’s most prominent monsoon, setting the stage for various severe convective weather events. MCSs and their associated ...  相似文献   

Heterosis and heritability estimates for the survival of the Pacific white shrimp (Litopenaeus vannamei) under the commercial scale ponds     

LU Xi  LUAN Sheng  CAO Baoxiang  SUI Juan  DAI Ping  MENG Xianhong  LUO Kun  KONG Jie 《海洋学报(英文版)》2017,36(2):62-68

The aim of the present study is to detect the potential of the base population from diallel crosses of eight introduced strains of the Pacific white shrimp(Litopenaeus vannamei) for improving the yield. Heterosis and heritability were estimated for pond survival at commercial farm conditions for the base population that included 207 full-sib families from a nested mating design by artificial insemination. Among all the hybrids,the heterosis ranged from –11.37%(UA1×UA2) to 20.53%(UA3×SIN) with an average of 0.953%. The results showed that more than half of the hybrids(51.85%) have negative heterosis for survival rate, but most of the hybrids with positive heterosis have high estimates. The high proportion of negative heterosis for survival rate reminders us that the survival trait also should be considered in the crossbreeding program to avoid yield decrease. However, high positive heterosis manifested in most of the hybrids for survival indicates the usefulness of these hybrids for improving the survival to obtain higher yield by crossbreeding in this breeding program. The heritability estimate for pond survival was 0.092±0.043 when genetic groups were included in the pedigree, and it was significantly different from zero(P0.05). The results from this study also indicated that significant improvement for survival is possible through selection in L. vannamei.  相似文献   

Crude-oil hydrocarbon composition characteristics and oil viscosity prediction in the northern Songliao Basin     

ZHANG JuHe  FENG ZiHui  FANG Wei  HUO QiuLi  ZHANG Kun  LI JingKun  ZENG HuaSen  ZHANG BoWei 《中国科学:地球科学(英文版)》2014,57(2):297-312

Crude oil hydrocarbon composition characteristics and oil viscosity prediction are important bases in petroleum exploration.A total of 54 oil/heavy-oil samples and 17 oil sands were analyzed and quantified using both comprehensive 2D gas chromatography(GC×GC)and comprehensive 2D gas chromatography/time-of-flight mass spectrometry(GC×GC/TOFMS).The results show that crude oil in the West slope is mainly heavy oil and its hydrocarbon composition is characterized overall by paraffinsmono-aromaticsnaphthenesnon-hydrocarbonsdi-aromaticstri-aromaticstetra-aromatics.Aromatics are most abundant and non-hydrocarbons are least abundant,whilst content differences among paraffins,naphthenes,aromatics,and non-hydrocarbons are less than 15%.There are two types of heavy oil,secondary type and mixing type.Biodegradation is the main formation mechanism of heavy oil.Biodegradation levels cover light biodegradation,moderate biodegradation,and severe biodegradation.With increasing biodegradation,paraffin content decreases while contents of aromatics and nonhydrocarbons increase.In contrast,naphthene content increases first and then decreases with increasing biodegradation.In severe biodegradation stage,naphthenes decrease more quickly than aromatics and non-hydrocarbons.This provides a new method for studying oil/heavy-oil biodegradation mechanism and biodegradation resistance of different hydrocarbons at different biodegradation stages.In the Longhupao-Daan terrace and Qijia-Gulong depression,most crude oil is conventional oil.Its composition is dominated by paraffins with the lowest content of aromatics.In some casual oil wells from the Longhupao-Daan terrace,crude oil from Saertu oil reservoirs is moderately biodegraded whereas crude oil from Putaohua oil reservoir is lightly biodegraded.Chemical parameters using saturate hydrocarbons and aromatics are usually not suitable for determining organic type and thermal maturity of biodegraded oil,especially of moderately or severely biodegraded oil,whilst Ts/(Ts+Tm)ratio can be used to determine thermal maturity of both conventional crude oil and heavy oil.  相似文献   

Phylogenetic diversity of planktonic bacteria in the Chukchi Borderland region in summer   总被引：1，自引：1，他引：0  

ZENG Yinxin  YU Yong  LI Huirong  HE Jianfeng  LEE Sang H  SUN Kun 《海洋学报(英文版)》2013,32(6):66-74

Planktonic bacteria are abundant in the Chukchi Borderland region. However, little is known about their diversity and the roles of various bacteria in the ocean. Seawater samples were collected from two stations K2S and K4S where sea ice was melting obviously. The analysis of water samples with fluorescence in situ hybridization (FISH) showed that DMSP-degrading bacteria accounted for 13% of the total bacteria at the station K2S. No aerobic anoxygenic phototrophic (AAP) bacteria were detected in both samples. The bacterial communities were characterized by two 16S rRNA gene clone libraries. Sequences fell into four major lineages of the domain Bacteria, including Proteobacteria (Alpha, Beta and Gamma subclasses), Bacteroidetes, Actinobacteria and Firmicutes. No significant difference was found between the two clone libraries. SAR11 and Rhodobacteraceae clades of Alphaproteobacteria and Pseudoalteromonas of Gammapro-teobacteria constituted three dominant fractions in the clone libraries. A total of 191 heterotrophic bacterial strains were isolated and 76% showed extracellular proteolytic activity. Phylogenetic analysis reveals that the isolates fell into Gammaproteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. The most common genus in both the bacterial isolates and protease-producing bacteria was Pseudoalteromonas. UniFrac data showed suggestive differences in bacterial communities between the Chukchi Borderland and the northern Bering Sea.  相似文献   

Design principle for parameters and interferences of tungsten carbide insert interface on roller bits     

YIN Kun  JONG Yonchol  BO Kun  CHOE Jongman 《世界地质(英文版)》2013,16(1):43-47

The lifetime of roll-bits with inserted tooth will be obviously decreased while drilling in strata and the tungsten carbide can be integrally separated from the roll-cone,which will need more trip out time to replace the roller bit.This study provides an entire analysis on stress as well as strength for teeth and tooth holes in loaded conditions.Qualities of tooth drop from matrix within roller bit.The optimized interferences of teeth inserted into the bit can be reasonably obtained by the critical interference derived from some relevant influence factors on the tooth-fixing quality of roller bits.  相似文献   

Development of a 50-year daily surface solar radiation dataset over China   总被引：1，自引：0，他引：1  

TANG WenJun  YANG Kun  QIN Jun  MIN Min 《中国科学:地球科学(英文版)》2013,(9):1555-1565

Although solar radiation is a crucial parameter in designing solar power devices and studying land surface processes,long-term and densely distributed observations of surface solar radiation are usually not available.This paper describes the development of a 50-year dataset of daily surface solar radiation at 716 China Meteorological Administration(CMA) stations.First,a physical model,without any local calibration,is applied to estimate the daily radiation at all 716 CMA routine stations.Then,an ANN-based(Artificial Neural Network) model is applied to extend radiation estimates to earlier periods at each of all 96 CMA radiation stations.The ANN-based model is trained with recent reliable radiation data and thus its estimate is more reliable than the physical model.Therefore,the ANN-based model is used to correct the physical model dynamically at a monthly scale.The correction generally improves the accuracy of the radiation dataset estimated by the physical model:the mean bias error(MBE) averaged over all the 96 radiation stations during 1994-2002 is reduced from 0.68 to 0.11 MJ m-2 and the root mean square error(RMSE) from 2.01 to 1.80 MJ m-2.The new radiation dataset shows superior performance over previous estimates by locally calibrated ngstr m-Prescott models.Based on the new radiation dataset,the annual mean daily solar radiation over China is 14.3 MJ m-2.The maximal seasonal mean daily solar radiation occurs in the Tibetan Plateau during summer with a value of 27.1 MJ m-2,whereas the minimal seasonal mean daily solar radiation occurs in the Sichuan Basin during winter with a value of 4.7 MJ m-2.  相似文献   

Hydrodynamic Evolution and Hydrocarbon Accumulation in the Dabashan Foreland Thrust Belt,China   总被引：1，自引：0，他引：1  

ZENG Jianhui  GUO Kai  TIAN Kun  and XU Tianwu 《《地质学报》英文版》2012,86(4):912-923

There are two plays in the Dabashan foreland tectonic belt: the upper and the lower plays. The lower play experienced one sedimentary hydrodynamic stage, two burial hydrodynamic stages, two tectonic hydrodynamic stages and two infiltration hydrodynamic stages from the Sinian to the Cenozoic, while the upper play had one sedimentary hydrodynamic stage, one burial hydrodynamic stage, two tectonic hydrodynamic stages and one infiltration hydrodynamic stage from the Permian to the Cenozoic. Extensive flows of both sedimentary water, including hydrocarbons, and deep mantle fluid occurred in the Chengkou faults during collision orogeny in the Middle-Late Triassic Indosinian orogeny, and fluid flow was complicated during intracontinental orogeny in the Middle-Late Jurassic. In addition to these movements, infiltration and movement of meteoric water took place in the Chengkou faults, whereas in the covering-strata decollement tectonic belt, extensive sedimentary water flow (including hydrocarbons) occurred mainly in the Zhenba and Pingba faults. During the stage of rapid uplift and exhumation from the Cretaceous to the Cenozoic, the fluid flow was characterized mainly by infiltration of meteoric water and gravity-induced flow caused by altitude difference, whereas sedimentary water flow caused by tectonic processes was relatively less significant. Sedimentary water flow was more significant to the lower play in hydrocarbon migration and accumulation during collision orogeny in the Middle-Late Triassic Indosinian orogeny, but its influence is relatively slight on the upper play. On one hand, hydrodynamics during intracontinental orogeny in the Middle-Late Jurassic adjusted, reformed or oven destroyed oil reservoirs in the lower play; on the other hand, it drove large amounts of hydrocarbons to migrate laterally and vertically and is favorable for hydrocarbon accumulation. Infiltration hydrodynamics mainly adjusted and destroyed oil reservoirs from the Cretaceous to the Cenozoic.  相似文献