Stable isotope analysis of consumer food webs indicates ecosystem recovery following prolonged drought in a subtropical estuarine lake     

MS Bird  R Perissinotto  NAF Miranda  N Peer  JL Raw 《African Journal of Marine Science》2016,38(3):411-422

Assessing changes in food-web structure provides a useful monitoring tool for gauging the resilience of ecosystems in the face of climatic impacts. We consider the ecological resilience of a large estuarine lake (St Lucia Estuary, South Africa) in the wake of an extreme climatic event (prolonged drought). Using carbon and nitrogen stable isotopes, food-web structure was assessed at five sites across the estuary during the winter and spring of 2013. Sampling occurred approximately three years after heavy rains flooded the system and returned it to a relatively diluted state following an almost decade-long drought that decimated food webs in the upper parts of the estuary due to hypersalinity effects. Comparisons of niche width and variance of consumer food webs among sites revealed a general homogenisation of food webs across the entire system, contrasting with the spatial differentiation of food webs documented during the drought phase. Our results indicate that the estuary is able to maintain ecological resilience at the whole-system level in the face of an extreme drought. This is likely facilitated by source pools of species residing in the relatively stable lower estuary, which are able to rapidly recolonise areas denuded by drought in the upper estuary.  相似文献   

中国富士苹果种植的气候适宜性研究   总被引：4，自引：0，他引：4  

屈振江  周广胜 《气象学报》2016,74(3):479-490

基于中国1981-2010年2084个气象台站资料和203个富士苹果种植区分布的地理数据,利用最大熵(MaxEnt)模型和ArcGIS平台,从物种分布机理与品质两方面研究了影响富士苹果在中国分布的主导气候因子及适宜范围,并对其气候适宜性进行区域划分和评价。结果表明,影响富士苹果在中国分布的主导气候因子有8个,富士苹果地理分布的气候适宜范围分别为年日照时数2000-2500 h、年平均气温7-14℃、≥10℃积温3000-4800℃·d、最冷月平均气温-7-0℃、夏季气温平均日较差8-12℃、年降水量400-800 mm、夏季平均气温20-26℃、夏季平均空气相对湿度60%-78%。中国富士苹果的气候适宜区主要分布在黄土高原、环渤海湾和黄河古道,其中,黄土高原区的陕西、山西和甘肃气候适宜度最高,而山东和河北两省富士苹果规模化种植还有较大发展空间。   相似文献   

Variation in summer surface air temperature over Northeast Asia and its associated circulation anomalies     

Wei Chen  Xiaowei Hong  Riyu Lu  Aifen Jin  Shizhu Jin  Jae-Cheol Nam  Jin-Ho Shin  Tae-Young Goo  Baek-Jo Kim 《大气科学进展》2016,33(1):1-9

This study investigates the interannual variation of summer surface air temperature over Northeast Asia(NEA) and its associated circulation anomalies.Two leading modes for the temperature variability over NEA are obtained by EOF analysis.The first EOF mode is characterized by a homogeneous temperature anomaly over NEA and therefore is called the NEA mode.This anomaly extends from southeast of Lake Baikal to Japan,with a central area in Northeast China.The second EOF mode is characterized by a seesaw pattern,showing a contrasting distribution between East Asia(specifically including the Changbai Mountains in Northeast China,Korea,and Japan) and north of this region.This mode is named the East Asia(EA) mode.Both modes contribute equivalently to the temperature variability in EA.The two leading modes are associated with different circulation anomalies.A warm NEA mode is associated with a positive geopotential height anomaly over NEA and thus a weakened upper-tropospheric westerly jet.On the other hand,a warm EA mode is related to a positive height anomaly over EA and a northward displaced jet.In addition,the NEA mode tends to be related to the Eurasian teleconnection pattern,while the EA mode is associated with the East Asia-Pacific/PacificJapan pattern.  相似文献   

Distributions of Downwelling Radiance at 10 and 20 μm in the High Arctic     

Zen Mariani  K. Strong  J. R. Drummond 《大气与海洋》2016,54(5):529-540

In the Arctic, most of the infrared (IR) energy emitted by the surface escapes to space in two atmospheric windows centred at 10 and 20?μm. As the Arctic warms and its water vapour burden increases, the 20?μm cooling-to-space window, in particular, is expected to become increasingly opaque (or “closed”), trapping more IR radiation, with implications for the Arctic’s radiative energy balance. Since 2006, the Canadian Network for the Detection of Atmospheric Change has measured downwelling IR radiation with Atmospheric Emitted Radiance Interferometers at the Polar Environment Atmospheric Research Laboratory at Eureka, Canada, providing measurements of the 10 and 20?μm windows in the High Arctic. In this work, measurements of the distribution of downwelling 10 and 20?µm brightness temperatures at Eureka are separated based on cloud cover, providing a comparison to an existing 10?µm climatology from the Southern Great Plains. The downwelling radiance at both 10 and 20?μm exhibits strong seasonal variability as a result of changes in cloud cover, temperature, and water vapour. Given the 20?µm window’s limited transparency, its ability to allow surface IR radiation to escape to space is found to be highly sensitive to changes in atmospheric water vapour and temperature. When separated by season, brightness temperatures in the 20?µm window are independent of cloud optical thickness in the summer, indicating that this window is opaque in the summer. This may have long-term consequences, particularly as warmer temperatures and increased water vapour “close” the 20?μm window for a prolonged period each year.  相似文献   

Subseasonal variability and predictability of the Arctic Oscillation/North Atlantic Oscillation in BCC_AGCM2.2     

《Dynamics of Atmospheres and Oceans》2016

The subseasonal variability and predictability of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) is evaluated using a full set of hindcasts generated from the Beijing Climate Center Atmospheric General Circulation Model version 2.2 (BCC_AGCM2.2). It is shown that the predictability of the monthly mean AO/NAO index varies seasonally, with the highest predictability during winter (December–March) and the lowest during autumn (August–November), with respect to both observations and BCC_AGCM2.2 results. As compared with the persistence prediction skill of observations, the model skillfully predicts the monthly mean AO/NAO index with a one-pentad lead time during all winter months, and with a lead time of up to two pentads in December and January. During winter, BCC_AGCM2.2 exhibits an acceptable skill in predicting the daily AO/NAO index of ∼9 days, which is higher than the persistence prediction skill of observations of ∼4 days. Further analysis suggests that improvements in the simulation of storm track activity, synoptic eddy feedback, and troposphere–stratosphere coupling in the Northern Hemisphere could help to improve the prediction skill of subseasonal AO/NAO variability by BCC_AGCM2.2 during winter. In particular, BCC_AGCM2.2 underestimates storm track activity intensity but overestimates troposphere–stratosphere coupling, as compared with observations, thus providing a clue to further improvements in model performance.  相似文献   

1—3月欧亚大陆热力变化及其与中国降水的关系   总被引：1，自引：1，他引：0       下载免费PDF全文

晏红明  王灵  李蕊 《应用气象学报》2016,27(2):209-219

利用1979—2011年NCEP/NCAR再分析资料、我国160个站降水和气温资料,分析欧亚大陆热力变化特征,其在冬季和春季的气候变率最明显,且南北区域呈反相差异。在此基础上, 探讨1—3月欧亚大陆热力差异与中国降水异常的关系,欧亚大陆正 (负) 热力差异年,1—3月华南、西南至河套西部地区降水偏多 (少) 明显,后期夏季多雨带位于长江中下游地区 (华南地区)。大气环流异常特征显示:1—3月欧亚大陆南北热力差异与同期北极涛动 (AO)、东亚大槽、东亚高空急流等大尺度大气环流,以及后期东亚高空急流、南亚高压、低层季风风系异常的密切相关是欧亚大陆热力变化与中国降水联系的可能途径。  相似文献   

SCHMIDT‐HAMMER EXPOSURE AGES FROM PERIGLACIAL PATTERNED GROUND (SORTED CIRCLES) IN JOTUNHEIMEN,NORWAY, AND THEIR INTERPRETATIVE PROBLEMS          下载免费PDF全文

STEFAN WINKLER  JOHN A. MATTHEWS  RICHARD W. MOURNE  PETER WILSON 《Geografiska Annaler: Series A, Physical Geography》2016,98(3):265-285

Periglacial patterned ground (sorted circles and polygons) along an altitudinal profile at Juvflya in central Jotunheimen, southern Norway, is investigated using Schmidt‐hammer exposure‐age dating (SHD). The patterned ground surfaces exhibit R‐value distributions with platycurtic modes, broad plateaus, narrow tails, and a negative skew. Sample sites located between 1500 and 1925 m a.s.l. indicate a distinct altitudinal gradient of increasing mean R‐values towards higher altitudes interpreted as a chronological function. An established regional SHD calibration curve for Jotunheimen yielded mean boulder exposure ages in the range 6910 ± 510 to 8240 ± 495 years ago. These SHD ages are indicative of the timing of patterned ground formation, representing minimum ages for active boulder upfreezing and maximum ages for the stabilization of boulders in the encircling gutters. Despite uncertainties associated with the calibration curve and the age distribution of the boulders, the early‐Holocene age of the patterned ground surfaces, the apparent cessation of major activity during the Holocene Thermal Maximum (HTM) and continuing lack of late‐Holocene activity clarify existing understanding of the process dynamics and palaeoclimatic significance of large‐scale sorted patterned ground as an indicator of a permafrost environment. The interpretation of SHD ages from patterned ground surfaces remains challenging, however, owing to their diachronous nature, the potential for a complex history of formation, and the influence of local, non‐climatic factors.  相似文献   

亚热带山地丘陵区气象要素空间化方法分析     

陈晓玲  曾永年  柳文杰 《测绘与空间地理信息》2017,(12):51-56

空间连续的气象要素是区域环境、生态系统模拟的重要参数,空间插值是实现气象观测站点数据空间化的主要方法。由于不同区域气候要素时空分布的复杂性,研究适用于特定区域的空间化方法具有重要意义。本文以湖南省为研究区,分析长江中游亚热带丘陵区气象要素的空间化方法。基于湖南省及其毗邻地区的46个气象站点14年(2000—2013年)的气象观测数据(月降水量、月均温)和DEM数据,对普通克里金法(OK)、反距离加权法(IDW)、样条法(SPLINE)和基于DEM的多元线性回归插值法(MLR)进行比较分析研究。研究结果表明:1)月降水量和月均温的MRE和RMISE值排序分别为:SPLINEIDWMLROK和SPLINOKIDWMLR;年平均降水量和年均温插值的MRE和RMISE值排序分别为:SPLINEIDWOKMLR和SPLINOKIDWMLR;2)MLR法不仅插值误差小,而且能从细节上反映出气象变化的空间变异性;3)对多变量进行数据探索分析表明,MLR插值法中,经度、坡度与年降水量空间分布存在空间的一致性;纬度、高程和坡度对年均温的空间分布具有很强的解释力。  相似文献   

北半球秋季欧亚遥相关与华西秋雨的关系   总被引：2，自引：0，他引：2  

徐金霞  闫彩霞  钟燕川  刘佳  马振峰 《气象科技》2017,45(3):492-498

利用EOF、相关分析、合成分析等常规统计方法研究华西秋雨与秋季欧亚遥相关(EUa)的关系。结果表明:北半球秋季欧亚遥相关(EUa)指数与华西秋雨呈显著的负相关,两者具有一致的阶段性特征。以1986年为界,20世纪80年代中期之前华西秋雨与EUa指数相关系数波动较大,均在-0.4以上,显著相关区主要集中于四川盆地西南部、贵州大部;20世纪80年代中期之后两者相关系数呈显著增加趋势,且显著相关区域向北偏移,主要集中于四川东北部、重庆大部以及陕西南部地区。EUa异常与华西秋雨的多寡关系显著。EUa正异常年,中高纬度环流形势与水汽特征有利于华西秋雨北部地区降水发生,华西秋雨南部地区缺乏水汽,动力条件不足,不利于秋雨偏多。EUa负异常年,华西秋雨东部地区,表现为有利于降水偏多,而西部地区则特征相反。  相似文献   

1951—2013年我国冬季气温年代际变化与PDO的关系     

徐忆菲  彭丽霞  李季  申双和 《气象科技》2017,45(4):669-677

利用我国160个测站1951—2013年冬季月平均气温资料和1951—2016年间冬季太平洋年代际振荡(PDO：Pacific Decadal Oscillation)指数资料,分析了两者在年际和年代际时间尺度上的相关关系,探讨了PDO对我国冬季气温影响的可能物理过程。结果发现：PDO与我国冬季气温年际变化不显著;在冬季期间,PDO对我国气温的影响是滞后的;PDO与我国冬季气温年代际变化存在密切关系,当PDO处于年代际正(负)位相时,我国气温普遍偏高(低);PDO年代际分量对我国的影响机制为：当PDO指数位于年代际正(负)位相时段,海平面气压场上西伯利亚高压减弱(增强),500 hPa高度场东亚大槽强度减弱(增强),200 hPa纬向风场东亚北支急流减弱(增强),这些都有利于我国冬季气温偏高(低)。  相似文献