基于EEMD的太阳活动对印度夏季风的多尺度胁迫分析

选取10.55~2.7 kaBP Qunf洞的Q5石笋δ¹⁸O记录作为印度夏季风的代用指标,集合经验模态分解（EEMD）多尺度分析结果揭示了印度夏季风的强弱变化和与亚洲季风减弱事件的一致性,进一步讨论了11 kaBP以来印度夏季风的逐渐增强而后减弱的发展态势。选用同时期的古树年轮¹⁴C记录作为太阳活动代用指标,调频、调幅分析结果发现印度夏季风的31 a、70 a和7 860 a尺度分量受太阳活动相应分量的调频胁迫较为显著;同时又揭示出“太阳活动71 a周期-印度夏季风31 a周期”“太阳活动1 379 a周期-印度夏季风142 a周期”和“太阳活动2 376 a周期-印度夏季风733 a周期”三对调幅胁迫。     

伊犁河谷2001-2014年地表温度时空分异特征

地表温度是地表能量平衡、区域和全球尺度地表物理过程的一个重要因子。为了辨析中国西北干旱区“天山湿岛”——伊犁河谷的地表温度时空分异,采用趋势分析法和空间数据统计法,探讨了2001-2014年不同土地利用/覆盖类型下地表温度时空变化规律,分析地表温度的时空分异特征及原因。结果表明：（1） MODIS LST产品的精度（平均R²=0.90）能够满足伊犁河谷地表温度时空变化分析的要求;（2）空间上,地表温度呈现出中部高四周低的变化趋势,高温区面积约占总面积的41%,低温区面积约占总面积的23%;时间上,伊犁河谷平均地表温度的年际波动较大,以2013年、2006年、2007年和2008年尤为突出;地表温度的年内变化呈现出单峰型分布,地表温度高值集中在3-8月,最高值出现在7月;（3）不同土地利用/覆盖类型下年均地表温度分布的总体特征为建设用地最高,稀疏草地、旱地等次之,冰川/积雪最低;（4）伊犁河谷地表温度变化趋势呈严重减少、基本不变和轻微增加区域面积分别占5%、37%和26%,以基本不变和轻微增加为主。伊犁河谷地表温度时空变化不仅受大尺度气候变化影响,还受土地类型差异影响,两者共同构成了不同地理区域及景观的温场格局,绿色植被对地表温度时空分布具有重要的调节作用。     

中国留学人员创业园分布及产业特征

以《中国留学人员创业年鉴》为基础数据,采用GIS空间分析技术,运用核密度估计法、L函数和最近邻层次聚类分析等方法,分析2006~2015年中国留学人员创业园空间分布规律以及园区产业集聚特征,结果表明：中国留学人员创业园集聚特征显著,而且随着时间的推移,其多中心趋势明显,集聚规模迅速增大,集聚强度呈“先升后降,但总体增大”趋势;主要集聚于长三角、京津冀和珠三角等地区,尤以前两者最显著,且三大集聚区的集聚强度与集聚规模差异明显,其中长三角留创园的集聚规模最大,京津冀集聚强度最高,而珠三角则比较复杂,其在很小空间尺度范围内服从集聚分布,而在较大空间尺度范围内则服从随机分布;基于不同主导产业的中国留学人员创业园依然集中于长三角、京津冀和珠三角等地区,其主导产业分布格局则差异显著,规律性不强。     

江南丘陵地区乡村聚落地域分异特征研究——以湖南省为例

以江南丘陵湖南地区为研究对象,通过对18个抽样村进行实地走访与问卷调查,从乡村聚落的居住条件、居住设施和乡村居民的生产生活形态等方面,探讨江南丘陵湖南地区乡村聚落空间地域分异特征与规律。研究表明：乡村聚落研究是江南丘陵地区乡村聚落空间布局优化与调控的基础。由于地域范围广泛,区域内的资源禀赋与地域组合、经济发展基础、文化传统等条件差异悬殊,因此江南丘陵湖南地区乡村聚落发展的地域分异规律较为明显,在聚落空间格局（规模、密度、形态）、居住条件（住房面积、住房结构、建筑特色）、居住设施（道路、饮水安全、网络电视开通率等基础与公共服务设施）和生产生活形态等方面呈现出较为显著的盆地-丘陵-低山区、发达-欠发达-落后、近郊-远郊-偏远等地貌、经济、区位梯度差异。     

1998~2013年中国地级单元制造业规模与结构高级度协调发展的时空特征

基于制造业企业级数据,采用产业结构高级度（UPG）指数、GIS、协调度评价模型等方法考察1998~2013年中国地级单元制造业规模与结构高级度协调发展的时空特征。结果表明：① 制造业规模格局始终呈东部沿海导向下的核心-边缘模式,沿海三大城市群规模优势明显,西南、西北以及青藏地区规模最小。② 制造业结构高级度格局总体呈“马赛克”式的混合分布模式,东北、黄河中游等传统工业基地的UPG指数下降明显,长三角、珠三角、山东半岛等沿海地区则不断提升。③ 制造业规模与结构高级度间的协调度水平稳定上升,总体由中度失调进入濒临失调阶段,但协调度水平及其成长格局具有“东-中-西”阶梯式降低特征。     

唐朝末年以来广西柳州干湿变化及人类活动演变

中世纪暖期和小冰期是近2 000年气候变化中重要的气候事件,厘清其在低纬度地区干湿变化特征及其对古代农业发展及人口增长的影响,具有重要的意义。通过对广西柳州岩溶洞穴中一60 cm岩芯进行孢粉、炭屑分析发现,研究区的气候、稻作农业从唐末以来先后经历了6个阶段演化：1）875―940 a A.D.,C/P值及花粉记录指示：研究区气候整体偏干,水稻种植减少;2）940―1 050 a A.D.,C/P值及花粉记录指示：夏季风增强,水稻种植稍增长,人口增加;3）1 050―1 140 a A.D.,C/P值及花粉记录指示：夏季风减弱,稻作农业及人口较前期有所增长;4）1 140―1370 a A.D.,C/P值及莎草科花粉含量指示：研究区当时气候处于“中世纪暖期”温暖湿润期,稻作农业面积扩大,人口增加;5）1 370―1 900 a A.D.,C/P值及莎草科花粉含量指示：“小冰期”气候变干,水稻种植及人口逐渐减少;6）1 900―2 009 a A.D.气候变暖湿,水稻种植扩大,人口迅速增长。进一步对研究区气候事件与稻作农业及人口关系研究发现：历史时期气候事件与水稻种植、人口具有耦合关系,即中世纪暖期,气候暖湿,水稻种植扩大,人口增殖;小冰期,气候冷干,水稻种植萎缩,人口锐减。在非原地沉积时,莎草科和C/P 对水分反映敏感,可以用来指示气候干湿变化。     

基于北极黄河站观测的日侧极光研究新进展

回顾了基于中国黄河站全天空极光观测对日侧弥散极光与喉区极光研究的最新进展。首先,利用黄河站极光观测,对日侧弥散极光展开系统性分类与统计研究,对这一重要空间物理现象取得新认识,指出日侧弥散极光对研究日侧外磁层冷等离子体的分布、形成及磁鞘粒子进入磁层都具有重要启示作用;同时发现并定义了一种新型分立极光结构——喉区极光,并推断其可能对应磁层顶的局地变形。喉区极光是指发生在电离层对流喉区附近、从极光卵赤道侧向低纬方向延伸出来的分立极光结构。全天空极光观测表明喉区极光走向大致与电离层对流方向一致。之后,观测验证了喉区极光对应磁层顶局地内陷式变形的推测;统计发现喉区极光是一种非常高发的现象,对应的磁层顶变形尺度可达2—3 Re,并指出这种变形最可能由磁鞘高速流冲击磁层顶产生;发现在喉区极光产生过程中还可能触发磁重联;证实伴随喉区极光的产生,磁鞘粒子会进入磁层并诱发产生一种新型弥散极光。通过喉区极光研究,可以将已有的磁鞘瞬态过程研究和触发式磁重联研究有机地结合在一起,对太阳风-磁层耦合过程形成一种新的认识,即:在磁鞘中局地产生(而不是存在于太阳风中)的瞬态过程可以在日下点附近频繁地导致磁层顶局地变形、触发重联、引发系列地球空间效应,可能对太阳风-磁层耦合具有不可忽略的重要性。以此为基础,讨论了日侧极光研究引出的新课题。     

Impact of reservoir operation and climate change on the hydrological regime of the Sesan and Srepok Rivers in the Lower Mekong Basin

The transboundary Sesan and Srepok sub-basins (2S) are the “hot-spot” areas for reservoir development in the Lower Mekong region, with 12 reservoirs built in the Vietnam territory. This study examines the impacts of reservoir operations in Vietnam and projected climate change on the downstream hydrologic regime of the 2S Rivers by jointly applying the Soil Water Assessment Tool (SWAT) and Water Evaluation and Planning (WEAP) models. Different scenarios of reservoir operation are considered and simulated to assess their impact on annual, seasonal, and monthly flow regimes under maximum hydropower capacity generation with and without taking into account the minimum flow requirement downstream near the Vietnam border with Cambodia. The precipitation and temperature projections from the high-resolution regional climate model HadGEM3-RA under two Representative Concentration Pathways, 4.5 and 8.5, of HadGEM2-AO are used as future climate change scenarios for the impact assessment. The study results show that reservoir operation leads to an increase in the dry season stream flows and a decrease in the wet season stream flows. The monthly flow regime exhibits considerable changes for both the Sesan and Srepok Rivers but with different magnitudes and patterns of increase and decrease. Climate change is likely to induce considerable changes in stream flows, though these changes are comparatively lower than those caused by reservoir operation. Climate change is likely to have both counterbalancing and reinforcing effects over the impact of reservoir operation, reducing changes during dry season but increasing changes in most of the other months.     

Assimilation of Feng-Yun-3B Satellite Microwave Humidity Sounder Data over Land

The ECMWF has been assimilating Feng-Yun-3B(FY-3B) satellite microwave humidity sounder(MWHS) data over ocean in an operational forecasting system since 24 September 2014. It is more difficult, however, to assimilate microwave observations over land and sea ice than over the open ocean due to higher uncertainties in land surface temperature, surface emissivity and less effective cloud screening. We compare approaches in which the emissivity is retrieved dynamically from MWHS channel 1 [150 GHz(vertical polarization)] with the use of an evolving emissivity atlas from 89 GHz observations from the MWHS onboard NOAA and EUMETSAT satellites. The assimilation of the additional data over land improves the fit of short-range forecasts to other observations, notably ATMS(Advanced Technology Microwave Sounder) humidity channels, and the forecast impacts are mainly neutral to slightly positive over the first five days. The forecast impacts are better in boreal summer and the Southern Hemisphere. These results suggest that the techniques tested allow for effective assimilation of MWHS/FY-3B data over land.     

Spatiotemporal correlation in WebGIS group-user intensive access patterns

Group-user intensive access to WebGIS exhibits spatiotemporal behaviour patterns with aggregation features and regularity distributions when geospatial data are accessed repeatedly over time and aggregated in certain spatial areas. We argue that these observable group-user access patterns provide a foundation for improved optimization of WebGIS so that it can respond to volume intensive requests with a higher quality of service and improve performance. Subsequently, a measure of access popularity distribution must precisely reflect the access aggregation and regularity features found in group-user intensive access. In our research, we considered both the temporal distribution characteristics and spatial correlation in the access popularity of tiled geospatial data (tiles). Based on the observation that group-user access follows a Zipf-like law, we built a tile-access popularity distribution based on time-sequence, to express the access aggregation of group-users with heavy-tailed characteristics. Considering the spatial locality of user-browsed tiles, we built a quantitative expression for the correlation between tile-access popularities and the distances to hotspot tiles, reflecting the attenuation of tile-access popularity to distance. Moreover, given the geographical spatial dependency and scale attribute of tiles, and the time-sequence of tile-access popularity, we built a Poisson regression model to express the degree of correlation among the accesses to adjacent tiles at different scales, reflecting the spatiotemporal correlation in tile access patterns. Experiments verify the accuracy of our Poisson regression model, which we then applied to a cluster-based cache-prefetching scenario. The results show that our model successfully reflects the spatiotemporal aggregation features of group-user intensive access and group-user behaviour patterns in WebGIS. The refined mathematical method in our model represents a time-sequence distribution of intensive access to tiles and the spatial aggregation and correlation in access to tiles at different scales, quantitatively expressing group-user spatiotemporal behaviour patterns with aggregation features and a regular distribution. Our proposed model provides a precise and empirical basis for performance-optimization strategies in WebGIS services, such as planning computing resource allocation and utilization, distributed storage of geospatial data, and providing distributed services so as to respond rapidly to geospatial data requests, thus addressing the challenges of volume-intensive user access.