Tree-ring-based drought variability in northern China over the past three centuries     

ZENG Xueli  LIU Yu  SONG Huiming  LI Qiang  CAI Qiufang  FANG Congxi  SUN Changfeng  REN Meng 《地理学报(英文版)》2022,32(2):214-224

Droughts are the most frequent natural disaster in regions at the margins of the East Asian summer monsoon (EASM),which pose threats to agriculture,the economy,and human lives.However,the limitations of only approximately 60 years of meteorological ob-servations hamper our understanding of the characteristics and mechanisms of local hydro-climate.Trees growing in the marginal region of the EASM are usually sensitive to moisture variations and have played important roles in past hydroclimatic reconstructions.Here,a 303-year tree-ring-width chronology of Pinus tabulaeformis from Mt.Lama,which is located in the junction of the Liaoning Province and Inner Mongolia,China,was used to reconstruct the May-August Palmer drought severity index (PDSI) in the marginal region of the EASM.The transfer function explains 48.0％ (or 47.2％ after adjusting for the loss of the degrees of freedom) of the variance over the calibration period from 1946 to 2012.A spatial correlation analysis demonstrates that our PDSI reconstruction can represent the drought variability on the northernmost margin of the EASM.The winter Asian polar vortex area index showed a delayed impact on the summer EASM precipitation in the following year.  相似文献   

辫状河致密砂岩储层构型单元定量表征方法     

瞿雪姣  李继强  张吉  赵忠军  戚志林  罗超 《吉林大学学报(地球科学版)》2018,48(5):1342-1352

针对现有辫状河储层构型单元定量表征方法关键参数获取困难且可靠性存疑的问题,以储层构型理论为指导,基于现代辫状河沉积、钻井岩心、录井和测井等资料,提出了基于单一辫状河道宽度的构型单元定量表征方法。首先,根据单井构型单元解释结果,确定同期辫状河道平面分布;其次,根据连井对比剖面,确定连井剖面内单一辫状河道间的界线位置;再次,根据现代辫状河单一辫状河道宽度与构型单元关系定量模型,限定辫状水道宽度、复合心滩长度及宽度等4级构型单元规模;最后,在单一辫状河道内确定4级构型单元平面分布,进而在密集井网区对复合心滩进行解剖,确定单个心滩位置和几何形态。采用该方法对苏××提高采收率试验区盒₈^下_1-3单层辫状河致密砂岩气藏进行了分析,结果表明：该单层砂岩气藏发育5条单一辫状河道,其宽度为1 050~1 890 m;辫状水道宽度为234~435 m;复合心滩长度和宽度分别为1 931~3 569 m、685~1 242 m;单个心滩长度和宽度分别为660~1 880 m、310~1 030 m。  相似文献   

秦岭东部牛背梁自然保护区巴山冷杉树轮宽度与气候因子的关系     

秦进  白红英  翟丹平  王俊  李书恒  黎斌 《冰川冻土》2017,39(3):540-548

基于树木年代学方法,通过响应分析与回归分析对秦岭东段主脊牛背梁自然保护区巴山冷杉（Abies fargesii）树轮宽度所蕴涵的气候意义进行探讨。结果表明：巴山冷杉年轮宽度标准化年表和差值年表的各项特征值较高,反映树轮资料包含较强的环境信息;归纳相关分析结果,发现春夏季气温是树木径向生长的主导因子,当年1-8月不同时段的平均气温普遍对巴山冷杉生长有促进作用,其中1-2月平均气温对树木生长的影响最为显著,而前一年10-11月平均气温的“滞后作用”不可忽略。降水不是该区巴山冷杉生长的主要限制因子,但当年1-2月的降水过多会导致组织生长减缓;回归模型能较好模拟年轮宽度与气候因子之间的关系,据此结合极宽、极窄轮出现年份的气候状况印证了巴山冷杉树轮宽度年际变化是生长季初期气温、降水相互制衡、共同作用的结果,并推测巴山冷杉林带位置有向高海拔迁移的可能。为秦岭植被生长在气候变化过程中的生态模式演变研究提供一定的依据。  相似文献   

Study on wave-induced setup over fringing reefs in the presence of a reef crest     

《Applied Ocean Research》2017

It has been well observed that a reef crest (ridge) may be present at the reef edge, but so far very few published studies focusing on the effects of such reef-crest on the wave dynamics over fringing reefs. To understand the role of a reef-crest configuration in determining breaking-wave induced setup over the reef flat, a series of experiments were carried out in a wave flume using an idealized fringing reef model with a reef crest. Experimental results were reported for a trapezoidal reef crest with five reef-crest widths under a series of monochromatic waves. Also examined was the reef without a reef crest. Data analysis shows that larger energy dissipation associated with smaller surfzone width around the reef edge occurred with a wider reef crest. The maximum wave-induced setup on the reef flat in the presence of the reef crest was significantly larger than that without, and it also increased with increasing reef-crest width. The reef-crest submergence was found to be a primary parameter controlling the magnitude of wave setup on the reef flat provided that the reef crest was sufficient wide. An alternative semi-analytical 1DH model based on the balance of cross-shore momentum was proposed. The model was validated by present laboratory data as well as three existing 1DH laboratory studies. Comparing with other two representative semi-analytical models in the literature showed that the proposed model was capable of better reproducing the maximum wave-induced setup on the reef flat for a variety of reef profiles with/without a reef crest, different reef-crest water levels, as well as both monochromatic and spectral waves. The model parameter was physically related to the two characteristic lengths in the surf zone and its value was dependent on the fore-reef slope as well as the presence of a reef crest. The 1DH model was also satisfactorily applied to a fringing reef in field conditions where the effects of fore-reef friction and back-reef lagoon were not important.  相似文献