Relationships between long-term ocean warming,marine heat waves and primary production in the New Zealand region     

Stephen M. Chiswell  Philip J. H. Sutton 《新西兰海洋与淡水研究杂志》2020,54(4):614-635

ABSTRACT

We test the paradigm that in a future warmer ocean, shallower winter mixing will lead to less net primary production (NPP), by investigating whether warming between 2002 and 2018 led to changes in NPP in the Tasman Sea/New Zealand region. The 2002–18 trend in sea surface temperature (SST) was positive over most of the region, and was driven by increasingly warmer summers and marine heat waves (MHWs) rather than year-round warming. In contrast, the trends in sea surface chlorophyll (SSC) and NPP were generally positive over the Subtropical Front (STF) and in a subtropical band north-east of New Zealand, but negative elsewhere. Regressions between SSC and SST, and between spring SSC and the coldest SST during the preceding winter, show similar spatial patterns to the SSC trend. We suggest these findings reflect different ecosystem functioning in the subtropical and subantarctic biomes that are separated by the STF. We conclude that any future warming is likely to lead to less production in the Tasman Sea, but more production over the STF. Three recent MHWs had different impacts on production, but generally led to less surface biomass north of the STF and more biomass south of the front.  相似文献   

湄州湾现代沉积过程     

郭允谋  陈华胄  杨顺良 《热带海洋学报》1993,(3)

湄州湾强劲的潮流导致外海泥沙输入,但受一定程度的限制,海湾周围的陆源碎屑成为沉积物质的主要来源。水动力,特别是潮流作用控制现代沉积的格局,潮流冲刷槽为粗粒沉积属海底冲刷产物,两侧的斜坡及潮坪,从湾中央向岸,从粗细混合沉积物过渡为细粒沉积,属淤积产物。  相似文献   

Variations of mixed layer properties in the Norwegian Sea for the period 1948-1999     

J. Even Ø. Nilsen  Eva Falck 《Progress in Oceanography》2006,70(1):58-90

The mixed layer of the ocean and the processes therein affect the ocean’s biological production, the exchanges with the atmosphere, and the water modification processes important in a climate change perspective. To provide a better understanding of the variability in this system, this paper presents time series of the mixed layer properties depth, temperature, salinity, and oxygen from Ocean Weather Station M (OWSM; 66° N,2° E) as well as spatial climatologies for the Norwegian Sea. The importance of underlying mechanisms such as atmospheric fluxes, advective signals, and dynamic control of isopycnal surfaces are addressed. In the region around OWSM in the Norwegian Atlantic Current (NwAC) the mixed layer depth varies between ∼20 m in summer and ∼300 m in winter. The depth of the wintertime mixing here is ultimately restrained by the interface between the Atlantic Water (AW) and the underlying water mass, and in general, the whole column of AW is found to be mixed during winter. In the Lofoten Basin the mean wintertime mixed layer reaches a depth of ∼600 m, while the AW fills the basin to a mean depth of ∼800 m. The temperature of the mixed layer at OWSM in general varies between 12 °C in summer and 6 °C in winter. Atmospheric heating controls the summer temperatures while the winter temperatures are governed by the advection of heat in the NwAC. Episodic lateral Ekman transports of coastal water facilitated by the shallow summer mixed layer is found important for the seasonal salinity cycle and freshening of the northward flowing AW. Atmospheric freshwater fluxes have no significant influence on the salinity of the AW in the area. Oxygen shows a clear annual cycle with highest values in May-June and lowest in August-September. Interannual variability of mixed layer oxygen does not appear to be linked to variations in any of the physical properties of the mixed layer.  相似文献   

面向线性光谱混合分解的邻域像元集螺线型构建方法     

刘博宇  陈军  邢华桥  武昊  张俊 《测绘学报》2017,46(11):1841-1849

高时间分辨率遥感影像在地表景观破碎区域易形成混合像元,难以发挥其高时间维度优势。现有方式多是基于线性光谱混合模型,借助邻域像元所构成的像元集合组成线性方程组,求出组分光谱值的最小二乘解,提高其空间分辨率。然而,现有方法依赖窗口形式来构建邻域像元集合,在某些区域易造成方程组无解的欠定问题。本文在分析其问题原因的基础上,引入阿基米德螺线代替传统的矩形窗口,对邻域各像元依次遍历,构建空间邻近、组分相近的邻域像元集合来解决该问题。在GlobeLand 30数据上的试验表明,螺线型构建方法对5种混合尺度上多种类型地物均具有稳定的精度,与传统窗口构建方法相比,可从构建邻域像元集合方面将总体理论精度提高2%,分解结果精度提高近1个数量级。  相似文献   

华北秋季一次低槽冷锋积层混合云宏微物理特征与催化响应分析   总被引：2，自引：0，他引：2  

秦彦硕  蔡淼  刘世玺  蔡兆鑫  胡向峰  吕峰 《气象学报》2017,75(5):835-849

利用2013年10月13日机载粒子测量系统（PMS）在张家口涞源地区对积层混合云中上部进行的增雨探测数据,分析了云的垂直微物理结构、云区的可播性和作业前后液态云粒子、冰晶及降水粒子的微物理变化。结果表明,此次降水性积层混合云的垂直结构由冷、暖两层云配置,云层发展厚实,冷云区云粒子浓度平均为62 cm-3,液态水含量最大0.05 g/m3;2DC和2DP探测的冰晶及降水粒子平均浓度分别为1.9和2.2 L-1;暖云内云粒子数浓度集中在300 cm-3左右,液态水含量约0.1 g/m3。探测区域云粒子数浓度的水平分布不均匀。利用云内过冷水含量和冰晶浓度等参数判断,该降水性积层混合云的播撒作业层具有强可播性。对比作业前后云中粒子浓度及平均直径发现,云粒子在作业前时段内的平均浓度为31 cm-3,远高于作业后平均浓度（17.6 cm-3）;但平均直径变化不大。作业后冰晶粒子通过贝吉龙过程消耗过冷水长大,浓度由之前的0.86 L-1增至4.27 L-1,平均直径也增至550 μm。冰晶粒子逐渐长大形成降水,降水粒子浓度也相应有所升高,谱明显变宽。   相似文献   

基于偏振雷达的积层混合云降水增雨潜力识别方法研究     

陈羿辰  何晖 《大气科学》2017,41(3):578-592.

本文统计分析了北京地区近三年的有效降水,重点研究了积层混合云降水特点并对其分类,发现积层混合云降水出现频次约占总降水次数的61%,其中积层混合云降水以积层连结型和水平混合型为主,二者之和占近80%。重点分析了积层混合云中对流和层云两种不同特点降水类型的宏微观结构,确立了反射率因子Z、温度T、粒子含水量M、催化剂AgⅠ（碘化银）活化率NE和粒子相态HTC（hydrometeor type classification）为人工增雨潜力识别指标及这些识别指标的取值范围,同时也根据研究现状和人工影响天气需求总结制定出人工增雨潜力等级。利用偏振雷达构建模糊逻辑识别算法对积层混合云三种降水类型进行增雨潜力区域识别研究,结果表明:（1）对于播撒碘化银增雨来说,积层混合云的增雨潜力区在垂直方向上可分为上、中、下三层,上层（增雨等级为“不适合”）和下层（零度层及以下）分别受含水量和温度等影响不适合增雨,中间层（增雨等级大于等于“等级一”）是可增雨区域;（2）积层混合云中层云区增雨潜力较小,对流云区可增雨潜力要远大于层云区,开式流场型与积层连结型可增雨潜力要大于水平混合型;（3）当降水云中识别出霰粒子时,其附近的大部分区域会有较好的增雨潜力。通过偏振雷达实例检验和数值模式模拟在积层混合云不同部位播撒碘化银催化试验发现,在增雨潜力较好的区域催化有很明显增雨效果,模拟试验结论与偏振雷达识别增雨潜力区结果也基本一致,说明基于偏振雷达的增雨潜力区识别方法和结果是具有参考意义的。  相似文献   

Social and Geographic Contexts of Water Concerns in Utah     

Courtney G. Flint  Xin Dai  Douglas Jackson-Smith  Joanna Endter-Wada  Sara K. Yeo  Rebecca Hale 《社会与自然资源》2017,30(8):885-902

Public concerns about water issues are key considerations in responding to changing hydrologic conditions. Literature is mixed on the social profiles associated with resource-related risks. Using data from a household survey, we compare concerns about water shortage, climate change impacts on water supply, poor water quality, and flooding. We assess the combined influence of social and locational factors on each concern and variations across three valleys in northern Utah. Generalized linear mixed modeling is used, given the ordinal nature of most variables. Water shortage was the greatest concern, and female, older, nonwhite, and recreationally active respondents were generally more concerned about water issues than their counterparts. Education, income, and religious identity presented more complicated relationships with water concerns, with significant interaction effects with valley geography. This study has implications for improving public involvement in risk management and engendering support for future water policy and planning strategies to address these risks.  相似文献   

On the Response of Subduction in the South Pacific to an Intensification of Westerlies and Heat Flux in an Eddy Permitting Ocean Model     

Chengyan LIU  Zhaomin WANG  Bingrui LI  Chen CHENG  Ruibin XIA 《大气科学进展》2017,34(4):521-531

Based on an eddy permitting ocean general circulation model, the response of water masses to two distinct climate scenarios in the South Pacific is assessed in this paper. Under annually repeating atmospheric forcing that is characterized by different westerlies and associated heat flux, the response of Subantarctic Mode Water(SAMW) and Antarctic Intermediate Water(AAIW) is quantitatively estimated. Both SAMW and AAIW are found to be warmer, saltier and denser under intensified westerlies and increased heat loss. The increase in the subduction volume of SAMW and AAIW is about 19.8 Sv(1 Sv =10~6m~3s~(-1)). The lateral induction term plays a dominant role in the changes in the subduction volume due to the deepening of the mixed layer depth(MLD). Furthermore, analysis of the buoyancy budget is used to quantitatively diagnose the reason for the changes in the MLD. The deepening of the MLD is found to be primarily caused by the strengthening of heat loss from the ocean to the atmosphere in the formation region of SAMW and AAIW.  相似文献   

Measurements of POI-based mixed use and their relationships with neighbourhood vibrancy   总被引：3，自引：0，他引：3  

Yang Yue  Yan Zhuang  Anthony G. O. Yeh  Jin-Yun Xie  Cheng-Lin Ma  Qing-Quan Li 《International journal of geographical information science》2017,31(4):658-675

Although mixed use is an emerging strategy that has been widely accepted in urban planning for promoting neighbourhood vibrancy, there is no consensus on how to quantitatively measure the mix and the effects of mixed use on neighbourhood vibrancy. Shannon entropy, the most commonly used diversity measurement in assessing mixed use, has been found to be inadequate in measuring the multifaceted, multidimensional characteristics of mixed use. And lack of data also makes it difficult to find the relationship between mixed use and neighbourhood vibrancy. However, the recent availability of new sources including mobile phone data and Point of Interest (POI) data have made it possible to develop new indices of mixed use and neighbourhood vibrancy to analyse their relationships. Taking advantage of these emerging new data sources, this study used the numbers of mobile phone users in a 24-hour period as a proxy of neighbourhood vibrancy and used POIs from a navigation database to develop a series of mixed-use indicators that can better reflect the multifaceted, multidimensional characteristics of mixed-use neighbourhoods. The Hill numbers, a unified form of diversity measurement used in ecological literature that includes richness, entropy, and the Simpson index, are used to measure the degrees of mixed use. Using such fine-grained data sets and the Hill numbers allowed us to obtain better insights into the relationship between mixed use and neighbourhood vibrancy. Four models varying in POI measurements that reflect different dimensions of mixed use were presented. The results showed that either POI density or entropy can explain approximately 1% of neighbourhood vibrancy, while POI richness contributes significantly in improving neighbourhood vibrancy. The results also revealed that the entropy has limitations as a measure for representing mixed use and demonstrated the necessity of adopting a set of more appropriate measurements for mixed use. Increasing the number of POIs has limited power to improve neighbourhood vibrancy compared with encouraging the mixing of complementary POIs. These exploratory findings may be useful for adjusting mixed-use assessments and to help guide urban planning and neighbourhood design.  相似文献   

正在萌芽段的震积地层学   总被引：9，自引：0，他引：9  

梁定益  聂泽同 《高校地质学报》1997,3(4):458-461

地震是经常发生的,是地球节律的一种反映。震积岩一词是Seilacher A(1969)首先提出的,随后欧美学者掀起了研究高潮。Mutti等(1984)认为浊积岩即震浊积岩,可以作为一个事件地层单元进行填图与追索。我国学者宋天锐(1988)最早提出地震－海啸序列,可以作为燕山地区雾连山组地层划分对比的标志。乔秀夫等(1994．1995) 在华北上震旦统一下寒武坑中建立了“碳酸盐岩液化地震序列”与“萨布哈震积序列”并对华北东部同期地层进行了对比与成因地层学研究。笔者(1991．1994)指出扬子西缘的二叠系震积岩由原地相的地震干扰层与异地相的滑来震积层两部分组成．两者之问被震积不整台面分开 在伸展构造环境下,震积不整合即伸展不整合,它是瞬时间于水下形成的。滑来震积层表现为多旋回的震积序列,其中的化石混积层具有正向有序混积现象,这也与盆地边界正断层多次活动有关。由此,提出“扬子西缘的东吴伸展运动”新认识。将震积岩的研究与构造灾变事件,事件地层学接轨。我国地史上也是一个多震的地区,在我国土地上,完全有可能哺育出现代地层学的一门新分支—— 震积地层学。  相似文献