Interdecadal variation in Korean spring drought in the early 1990s     

《Dynamics of Atmospheres and Oceans》2017

Statistical change-point analysis was applied to a spring time series of the Palmer Drought Severity Index (PDSI) in Korea, and this showed that the total analysis period can be divided into two periods: a wet period (1975–1990) and a dry period (1991–2014). To investigate the deepening of the spring drought in Korea, a difference in the spring means between the 1991–2014 and 1975–1990 periods was analyzed with respect to large-scale environments. In the recent spring, a typical pressure system pattern in winter, which was an anomalous west-high east-low pressure system pattern, was strengthened throughout the troposphere around Korea. Due to the anomalous pressure system pattern, Korea was affected by relatively cold and dry anomalous northerlies. Furthermore, the western North Pacific subtropical high (WNPSH) was not intensified, and thus the supply of warm and moist airs into Korea was further reduced due to the upper-level jet moving further to the south. In order to determine the reason for the development of the anomalous west-high east-low pressure system pattern in East Asia, the difference in spring snow depth between the two periods was analyzed, and the analysis results showed that positive anomalies were predominant throughout most regions in East Eurasia. As a result, in the analysis of the ground heat net flux, negative anomalies were strengthened in most regions in East Eurasia. The cooling effect in the surrounding regions due to the high snow depth in East Eurasia strengthened the anomalous pressure system pattern as a west-high east-low type.  相似文献   

Interdecadal variation of precipitation days in August in the Korean Peninsula     

《Dynamics of Atmospheres and Oceans》2017

The present study examines a climate regime shift in the time series of the number of rainy days during August in the Korean Peninsula. The statistical change-point analysis indicates that a significant shift occurred in the time series around 1998, providing a rationale to divide it into two parts: 1975–1997 for the shorter rainy-day period and 1998–2012 for the longer rainy-day period. To examine the cause of recent rapid increases in the number of days with precipitation in August in the Korean Peninsula, differences in the averages of large-scale environments between the 1998–2012 period and the 1975–1997 period were analyzed.The differences in stream flows showed that anomalous cyclones were reinforced in the East Asian continent while anomalous anticyclones were reinforced in the western North Pacific at all layers of the troposphere. The anomalous anticyclones reinforced in the western North Pacific were associated with the western North Pacific subtropical high (WNPSH) developed a little more toward the Korean Peninsula recently. Consequently, the Korean Peninsula has been affected by anomalous south westerlies that supplied warm and humid airs from low tropical regions to the Korean Peninsula. The vertical thermal instability (warm anomaly at lower-level and cold anomaly at middle and upper-level) developed near the Korean Peninsula. In addition, upper tropospheric jets were reinforced further recently near the Korean Peninsula to provide good environments for development of upward flows. The frequency of TCs that affect the Korean Peninsula in August also increased rapidly since 1998.  相似文献   

基于稳定性同位素的普里兹湾南极大磷虾不同发育阶段食性转变分析     

张晔  李超伦  杨光  王延清  陶振铖  张永山  王爱军 《海洋学报(英文版)》2017,36(12):67-78

As one of the most common and dominant species in the Southern Ocean, Antarctic krill(Euphausia superba)play a significant role in food web structure and the process of energy flow. The diet of Antarctic krill in the Prydz Bay during austral summer of 2012/2013 was investigated and the ontogenetic shift in krill diet was evaluated using the stable isotope method. The nitrogen stable isotope values(δ~(15) N) of adults((2.78±0.58)‰) were much higher than those of juveniles((1.69±0.70)‰), whereas the carbon stable isotope values(δ~(13) C) of adults(–(28.26±1.08)‰) were slightly lower than those of juveniles(–(27.48±1.35)‰). Particulate organic matter(POM)from 0, 25, and 50 m depth combined(0/25/50 m) represented phytoplankton food items. The results showed that phytoplankton food items in surface water and mesozooplankton were two essential food items for Antarctic krill in the Prydz Bay during summer. POM(0/25/50 m) contributes 56%–69% and 26%–34% to the diet of juvenile and adult krill, respectively, whereas mesozooplankton composes 13%–34% and 58%–71% of the diet of juvenile and adult krill, respectively. Thus, an ontogenetic diet shift from POM(0/25/50 m), which consists mainly of phytoplankton, to a higher trophic level diet containing mesozooplankton, was detected. The capacity for adults to consume more zooplankton food items may minimize their food competition with juveniles, which rely mostly on phytoplankton food items. This suggests "diet shift with ontogeny" which may somehow help krill keep their dietary energy budget balanced and well adapted to the Antarctic marine ecosystem as a dominant species.  相似文献   

雨生红球藻细胞形态转换和藻落形成差异研究     

程天佑  徐晓莹  张文蕾  张维  陈林  袁冠华  刘天中 《海洋科学》2017,41(8):1-8

基于雨生红球藻(Haematococcus pluvialis)培养过程中游动细胞和不动细胞的形态差异与转换,对比研究了两种细胞类型在离心收集与藻落形成效率上的差异。结果表明,雨生红球藻SCCAP K-0084在BYA培养基中培养4~6 d和9~12 d分别以绿色游动细胞与绿色不动细胞为主;早期游动细胞离心收集需要更高的离心力,但500~1 000 g离心5 min可以在不影响细胞存活率的情况下有效收获所有类型细胞;相比于传统直接涂布法,双层琼脂平板法可有效提高平板藻落形成效率,且游动细胞藻落形成效率比不动细胞藻落形成效率更高。TAP培养基由于藻落形成效率较低并不适合于雨生红球藻平板培养与筛选,自养型培养基虽然具有较好的藻落形成效率但是藻落形成速度较慢,相比而言,BYA培养基藻落形成效率较高且生长速度快,更适合用于雨生红球藻细胞的后期平板培养与筛选过程。  相似文献   

基于HadCM3模式的我国主要气候区划界线时空预测研究     

杨强  郑西楠  何立恒 《干旱区地理》2017,40(1):17-25

气候区域分异规律及其时空演变研究是气候变化研究的核心内容之一。以1951-2014年中国气象数据和基于HadCM3模式的1950-2059年气象模拟数据为数据源来分析中国主要气候区划界线的时空变化趋势。结果表明：我国寒温带界线北移,且速度呈加快趋势;中温带和暖温带的北部界线向北移动,且东段界线的移动趋势较明显;亚热带北部界线已越过秦岭-淮河一线,且其东段北移趋势较明显;热带范围逐渐向北扩张。东北地区由湿润转干燥,达到干湿并存的状态;河西走廊、青藏高原和新疆地区总体上呈转湿趋势,虽北方半干旱区有部分区域转换为干旱区,但未出现明显的移动;华北平原等地区的湿润-半湿润界线和干湿区分界线均向西北方向移动;南方湿润区的干湿状况未发生显著变化。  相似文献   

The response of vegetation growth to shifts in trend of temperature in China   总被引：5，自引：1，他引：4  

Bin He  Aifang Chen  Weiguo Jiang  Ziyue Chen 《地理学报(英文版)》2017,27(7):801-816

Though many studies have focused on the causes of shifts in trend of temperature, whether the response of vegetation growth to temperature has changed is still not very clear. In this study, we analyzed the spatial features of the trend changes of temperature during the growing season and the response of vegetation growth in China based on observed climatic data and the normalized difference vegetation index (NDVI) from 1984 to 2011. An obvious warming to cooling shift during growing season from the period 1984–1997 to the period 1998–2011 was identified in the northern and northeastern regions of China, whereas a totally converse shift was observed in the southern and western regions, suggesting large spatial heterogeneity of changes of the trend of growing season temperature throughout China. China as a whole, a significant positive relationship between vegetation growth and temperature during 1984 to 1997 has been greatly weakened during 1998–2011. This change of response of vegetation growth to temperature has also been confirmed by Granger causality test. On regional scales, obvious shifts in relationship between vegetation growth and temperature were identified in temperate desert region and rainforest region. Furthermore, by comprehensively analyzing of the relationship between NDVI and climate variables, an overall reduction of impacts of climate factors on vegetation growth was identified over China during recent years, indicating enhanced influences from human associated activities.  相似文献   

短时单频脉冲震源的海洋浅地层剖面资料频移处理     

刘玉萍  李丽青  薛花  邓桂林  张宝金 《CT理论与应用研究》2014,(2):227-235

采用短时单频脉冲震源的浅地层剖面,记录的波形数据空间假频较严重。因其信号具有频率高、频带窄的特征,通常利用Hiibert变换提取瞬时振幅属性（信号包络）供解释使用。但瞬时振幅均为正值,在进行构造解释时不方便使用。本文提出在对浅层剖面资料提取瞬时振幅的基础上,计算瞬时振幅的微分并配合滤波的方法,实现高频窄带浅地层剖面资料的一种频移处理。该方法把高频窄带的多周期信号变为低频带宽的单周期信号,有效扩展了倍频程并消除假频。应用在南海浅地层剖面资料处理中,资料处理后更利于构造解释。  相似文献   

Variations of bank shift rates along the Yinchuan Plain reach of the Yellow River and their influencing factors     

Suiji Wang  Ling Li  Weiming Cheng 《地理学报(英文版)》2014,24(4):703-716

It is important to examine the lateral shift rate variation of river banks in different periods. One of the challenges in this regard is how to obtain the shift rate of river banks, as gauging stations are deficient for the study of river reaches. The present study selected the Yinchuan Plain reach of the Yellow River with a length of 196 km as a case study, and searched each point of intersection of 153 cross-sections (interval between two adjacent cross-sections was 1.3 km) and river banks in 1975, 1990, 2010 and 2011, which were plotted according to remote sensing images in those years. Then the shift rates for the points of intersection during 1975–1990, 1990–2010 and 2010–2011 were calculated, as well as the average shift rates for different sections and different periods. The results show that the left bank of the river reach shifts mostly to the right, with the average shift rates being 36.5 m/a, 27.8 m/a and 61.5 m/a in the three periods, respectively. Contemporarily, the right bank shifts mostly to the right in the first period, while it shifts to the left in the second and third periods, with the average shift rates being 31.7 m/a, 23.1 m/a and 50.8 m/a in the three periods, respectively. The average shift rates for the left and right banks during the period 1975–2011 are 22.3 m/a and 14.8 m/a, respectively. The bank shift rates for sections A, B and C are different. The shift rate ratio of the left bank in the three sections is 1:7.6:4.6 for shift to the left and 1:1.7:3.8 for shift to the right, while that of the right bank is 1:1.8:1.2 for shift to the left and 1:5.6:17.7 for shift to the right during the period 1975–2011. Obviously, the average shift rate is the least in section A, while it is maximum in section B for shift to the left and in section C for shift to the right. The temporal variation of the shift rate is influenced by human activities, while the spatial variation is controlled by the local difference in bank materials.  相似文献   

我国产业经济重心演变路径及其影响因素分析   总被引：14，自引：0，他引：14  

黄建山  冯宗宪 《地理与地理信息科学》2005,21(5):49-54

针对重心的研究现状及存在的问题,在对比分析我国产业重心与经济重心、投资重心、人口重心演化路径的基础上提出假设,构造模型并进行计量分析,得出如下结论：产业重心移动不仅受产业产值大小及方差的显著影响,而且受经济、投资以及人口变量的总量大小及方差的显著影响,而增长速度对产业重心移动的影响不显著。  相似文献   

Relating a recruitment shift of Patagonian grenadier (Macruronus magellanicus Lönnberg) to large-scale environmental changes off Southern Chile     

LA Cubillos  EJ Niklitschek  S Cahuin 《新西兰海洋与淡水研究杂志》2013,47(2):284-293

The SE Pacific stock of Patagonian grenadier (Macruronus magellanicus) showed evidence of an abrupt reduction in recruitment after 2000. This drop exceeded expectations from changes in the spawning stock biomass (SSB), indicating a change in the stock-recruitment relationship (S-R). We evaluated whether variability in recruitment could be explained by concurrent changes in three environmental indices: sea-surface temperature anomaly (SSTA); southern oscillation index (SOI); and latitudinal position of the west wind drift bifurcation (WWDL). Continuous and discrete effects of these indices were tested as covariates in linear log-log and non-linear Ricker's S-R models. Discrete effects represented regime shifts detected in SSTA (1998), SOI (1998) and WWDL (1995). While SSTA was the only continuous variable found to be significant, the discrete 1998 regime shift supported the most informative model. The best Ricker's model considered a discrete intercept change in the same year: 1998. Although a spurious correlation between SSTA and S-R changes is possible, SSTA may be reflecting major physical or biological changes relevant to M. magellanicus juveniles in the SE Pacific.  相似文献