EFFECT OF CIRCULATION LOW LATITUDES ON THE WEATHER OF MIDDLE LATITUDES——THE IDEA OF MID-RANGE AND SHORT-RANGE FORECASTS OF RAINSTORMS

There is a close relation between the circulations of the low latitudes over the ocean as well as their. variations and precipitation in China.Rainstorms and droughts which often cause disasters are two extreme cases of precipitation. Therefore it is practically and theoretically significant to forecast both of them. A series of analyses on the predominant rainstorms processes in mid-summer in North China were made from 1975 to 1977[1,2],and the method was used.As a consequence, a preliminary conclusion has been reached.     

ERTK: extra-wide-lane RTK of triple-frequency GNSS signals

Triple-frequency signals have thus far been available for all satellites of BeiDou and Galileo systems and for some GPS satellites. The main benefit of triple-frequency signals is their formation of extra-wide-lane (EWL) combinations whose ambiguities can be instantaneously fixed for several 10–100 km baselines. Yet, this benefit has not been fully exploited and only used as a constraint for narrow-lane (NL) ambiguity resolution (AR) in most previous studies. In this study, we comprehensively investigate the real-time kinematic (RTK) capabilities of EWL observations, also referred to as EWL RTK (ERTK). We begin by mathematically expressing the ease of EWL AR and the difficulty of NL AR, respectively, using a numerical demonstration. We then present the mathematical models for ERTK including the ionosphere-ignored, ionosphere-float and ionosphere-smoothed types. The experiments are conducted using a four-station network of real triple-frequency BeiDou data with baseline lengths from 33 to 75 km. The results show that the ionosphere-ignored ERTK achieves real-time solutions with a horizontal accuracy of about 10 cm. Although the ionosphere-float ERTK solutions are very noisy, they can be quickly improved at the centimetre level by further applying the ionosphere-smoothed model. Note that such accurate results are very promising and already satisfy many applications without complicated NL AR. To the best of our knowledge, this is the first comprehensive study to make full use of EWL observations of triple-frequency signals on RTK.     

Rendering 2D Lines on 3D Terrain Model with Optimization in Visual Quality and Running Performance

With the gradual shift from 2D maps to a 3D virtual environment, various visual artifacts were generated by overlaying 2D map symbols on 3D terrain models. This work proposes a novel screen‐based method for rendering 2D vector lines with the accuracy of more than one pixel on the screen in real time. First, screen pixels are inversely projected onto a 3D terrain surface, and then onto the 2D vector plane. Next, these pixels are classified into three categories in terms of their intersection situation with the 2D lines. After that, a multiple sampling process is applied to the pixels that intersect with the 2D lines in order to eliminate visual artifacts, such as intermittence and aliasing (in pixel scale). Finally, a suitable point‐in‐polygon judgment is implemented to color each sample point quickly. The algorithm is realized in a heterogeneously parallel model so that the performance is improved and becomes acceptable.     

Detecting primary precursors of January surface air temperature anomalies in China

This study aims to detect the primary precursors and impact mechanisms for January surface temperature anomaly (JSTA) events in China against the background of global warming, by comparing the causes of two extreme JSTA events occurring in 2008 and 2011 with the common mechanisms inferred from all typical episodes during 1979–2008. The results show that these two extreme events exhibit atmospheric circulation patterns in the mid–high latitudes of Eurasia, with a positive anomaly center over the Ural Mountains and a negative one to the south of Lake Baikal (UMLB), which is a pattern quite similar to that for all the typical events. However, the Eurasian teleconnection patterns in the 2011 event, which are accompanied by a negative phase of the North Atlantic Oscillation, are different to those of the typical events and the 2008 event. We further find that a common anomalous signal appearing in early summer over the tropical Indian Ocean may be responsible for the following late-winter Eurasian teleconnections and the associated JSTA events in China. We show that sea surface temperature anomalies (SSTAs) in the preceding summer over the western Indian Ocean (WIO) are intimately related to the UMLB-like circulation pattern in the following January. Positive WIOSSTAs in early summer tend to induce strong UMLB-like circulation anomalies in January, which may result in anomalously or extremely cold events in China, which can also be successfully reproduced in model experiments. Our results suggest that the WIOSSTAs may be a useful precursor for predicting JSTA events in China.     

建筑物上侧击雷电的三维数值模拟

基于三维近地面闪电先导发展随机模式,通过改变先导初始电位和建筑物几何特性,分析各种情况下的侧击雷电发生概率,探讨侧击雷电产生原因及影响因素。结果发现:建筑物尖端电场畸变值是影响侧击雷电产生的重要参量,当下行先导靠近建筑物且传播位置低于建筑物的高度时,建筑侧面电场畸变值达到触发阈值,侧击雷电易产生;下行先导的初始电位以及建筑物几何特性（高度和宽度）是影响侧击雷电发生概率的重要因素,当下行先导初始电位在-9~-3 MV范围内,侧击雷电发生概率呈先增加后降低的趋势,当初始电位为-4.5 MV时,侧击雷电的发生概率达到峰值;当建筑物高度在50~150 m范围内,侧击雷电发生概率随着高度增加呈先增加后减少的趋势;当建筑物高度为100 m时,侧击雷电发生概率达到峰值;当建筑物宽度在30~70 m范围内,侧击雷电发生概率随建筑物宽度呈递减趋势;当建筑物宽度为30 m时,侧击雷电的发生概率达到峰值。     

Resettlement and Climate Impact: addressing migration intention of resettled people in west China

ABSTRACT

The relationship between climate change and human displacement is an important topic of global concern. China is a special case due to a high level of government control enforcing the ecological migration of millions of people since the mid-1980s. Little research has addressed how resettled people adapt to climate impacts in ecologically vulnerable resettlement areas and what factors influence their intentions to relocate again or adapt locally. Employing a social-ecological system approach, this study builds a conceptual econometric framework which differentiates two steps that drive migration intention at the household level. The study uses this approach to examine the role of both contextual and household factors in motivating the migration intentions of resettled people in the largest environmental resettlement area of Ningxia Hui Autonomous Region, China, where household survey data were collected in 2012. This framework enabled an analysis, first, of how local contextual factors and household factors shape the severity of climate impacts on households and, second, how these factors interact with the experience of climate impacts to further influence a household’s migration intention as a response to climate impacts. The results show that some contextual factors (such as limited use of water-saving techniques, little practice of cultivating aridity-resistant crops, and lack of government support), strong local social networks and being in receipt of low rates of financial remittances have significant associations with adverse climate impacts experienced by resettled households, and also with their anticipated further relocation to respond to these impacts.     

基于居住区比较的西宁城市居民日常活动空间研究

采用2013年西宁市城市居民周日和周一连续两天的活动日志调查数据,利用趋势面和路径缓冲区方法表征和测度西宁市城区单位、郊区单位、城区商品房、郊区商品房、城区混合5类居住区居民的活动空间,并进行比较研究,在行为层面上对西宁城市居民日常活动空间特征及成因进行解读,利用多元线性回归模型分析活动空间的影响因素。结果表明:(1)单位居住区居民形成了职住接近主导的近家工作活动空间,商品房和混合居住区居民形成了较为扩展的工作活动空间;(2)各类型居住区居民工作日非工作活动近家集聚;(3)休息日单位居住区居民活动空间较工作日扩展,郊区商品房居住区居民活动空间较工作日收缩,城区商品房与混合居住区与工作日几无差异;(4)郊区居民活动空间范围显著大于城区居民,居住区距离市中心的距离对西宁城市居民日常活动空间范围具有正向影响;(5)住房属性是影响居民日常活动空间的重要变量,工作日商品房居住区居民活动空间显著大于单位居住区居民,而休息日各类型居住区居民活动空间范围的差异缩小。     

一次寒潮强风天气过程分析

１９９５年１１月７日出现的寒潮强风天气过程是由于冷空气不断堆积产生强的气压梯度风,地面迅速加压产生强变压风,冷高压脊前高空动量下传产生强的动量下传风所谓三风合一的所造成。影响范围之广,持续时间之长均为历史上所罕见。     

高分辨图象声纳目标模拟器的设计

高分辨图象声纳在小目标的探测和识别中扮演重要角色，目标模拟器是图象声纳设备调试的主要仪器之一。文章讨论了模拟器信号发生的机理，分析了近场和远场声基阵输出的信号模型。给出了利用该仪器测得的某型图象声纳的波束图。     

南海北部的等辐骨虫

对南海北部的等辐骨虫以往没有进行过研究。1959年和1962年我们乘全国海洋综合调查的机会，先后对广东沿海和海南岛以南海域进行了调查，本文系该调查研究的结果。广东沿海位处亚热带，是南海边缘海域，受南海暖流影响，等辐骨虫的种类和数量都很丰富，仅初步调查所获已超过东海西部和西沙群岛所发现的种数。文中描述了中国沿海首次记录的等辐骨虫共8种，对各个种的分布及其与环境因子的关系等作了初步探讨。