How well do sediment indicators record past climate? An evaluation using annually laminated sediments

The reliability of paleoclimatic inferences from lake-sediment records rests on the understanding of how various sediment indicators respond to environmental changes. Despite the recent proliferation of paleoclimatic records, only a limited number of studies have rigorously evaluated potential indicators by comparing lake-sediment records with instrumental weather data. We analyzed annually laminated sediments of the past 100 years from a lake in north-central Minnesota for a suite of variables commonly used for climatic reconstructions. Results were compared with time series of climatic or climate-derived variables, as well as with indices of climate modes thought to influence the regional climate of the midwestern United States. The oxygen-isotopic composition of calcite (δ¹⁸O_c) shows trends similar to those of effective moisture (as measured by precipitation [P] minus actual evapotranspiration [AET], P-AET, and the Palmer Drought Severity Index [PDSI]), with high δ¹⁸O_c values generally corresponding to low P-AET and low PDSI. δ¹⁸O_c also exhibits striking correspondence with the index of Pacific Decadal Oscillation (PDO) but it lags behind PDO by 3 years. Elevated δ¹⁸O_c values during the warm PDO phase probably reflect warm and dry climatic conditions in the midwestern US, especially during winter months. The carbon-isotopic composition of calcite (δ¹³C_c) shows some similarity with δ¹⁸O_c but also displays stratigraphic patterns resembling those of lake-productivity indicators, including biogenic silica, inverse of inorganic carbon, ratio of organic carbon to nitrogen, and to a lesser extent, organic carbon. δ¹³C_c is correlated with mean annual air temperature (MAAT) and the index of Atlantic Multidecadal Oscillation (AMO), probably because elevated MAAT stimulates the rate of algal carbon uptake, lengthens growing season, and/or enhances CO₂ degassing. Varves are typically thicker during periods of lower δ¹⁸O_c and higher P-AET (or PDSI) values, because wet climatic conditions probably increase nutrient availability and lake productivity. Gray-scale intensity does not co-vary with any of the above climatic variables or climate-mode indices. These results demonstrate the utility of lake-sediment analyses for reconstructing temperature, drought, and large-scale climatic modes at Steel Lake. However, application to down-core reconstructions may be compromised by a number of factors, including the site specificity and non-stationarity of such relationships.     

玉溪太阳能辐射资源分布特征

玉溪市太阳能辐射量资源丰富,1960~2009年平均日照时数在2 286.3~2 085.3小时,每天平均日照6小时,冬春季由于晴天多,日照最丰富;盛夏雨日多,日照最小,秋季因经常出现连阴雨天气,日照也相对较小。最大值出现在春季的3月,平均日照8.5小时,最小值出现在盛夏的7月,平均日照仅2.6小时。玉溪太阳能辐射量为57.615×108~52.55×108kJ/m2,资源从东北向西南递增,最丰富的地方主要集中在元江、新平县,其次是江川、通海县,最小是澄江县。20世纪80年代末以后,由于观测场周围环境污染和建筑物的增多增高,对太阳能辐射观测值带来较大影响,使气象站实际观测到的日照小于20世纪80年代以前,并且较不稳定。     

An overview on observational instruments and measuring methods for dewfall

This paper systematically summarizes previous measuring methods and observational instruments for the magnitude of dewfall on land surface, analyzes the characteristics of common observational instruments for land surface dewfall, and describes several basic dewfall measurement methods. Moreover, the basic principles of these methods and instruments are interpreted, and their advantages, disadvantages, and applicability are analyzed. Recommendations for the further improvement of these observational instruments and the development of dewfall measuring methods are presented, and new technologies and scientific proposals for exploiting dewfall are elucidated.     

基于改进型逆推法和模糊评价法的暴雨服务效益评估

对2010—2022年江西省70次暴雨过程开展了气象服务效益评估,在充分考虑政府组织决策水平、部门联防联动、公众参与及气象服务水平等影响的情况下,加入赋权系数,结合隶属度函数构建重要因子矩阵,基于改进的逆推法和模糊综合评价法建立了江西省暴雨灾害气象服务效益评估模型,实现了江西省暴雨灾害气象服务效益定量化评估。结果表明,2010—2022年江西省暴雨灾害直接经济损失和气象服务效益均有逐渐增长的趋势,不可避免损失因子为0.17—0.50,气象服务效益占经济总损失的25%—45%。暴雨灾害直接经济损失和气象服务效益相关性较高,表明气象服务在防灾减灾工作中起重要作用。     

关于地理信息产业的发展及几点建议

进入信息时代 ,地理信息产业迅速发展 ,取得巨大的成果 ,现代化的地理信息产品和技术服务在经济与社会可持续发展中的重要作用越来越明显 ,因此发展地理信息产业自然成为更为重要的任务     

计算机缩放图功能的开发和应用

本文介绍了采用计算机数字化仪的点输入功能,将曲线数字化。通过程序处理,对原图进行缩放,绘制任意比例尺的图件。其特点是操作简便、工作效率高,能满足绘图精度要求。     

城市地球物理学发展展望

目前，全球50％以上的人口生活在地球表面不到1％的面积上，城市化是当今全球发展的重要趋势。人类活动是生物圈中最重要的活动之一。半个世纪以来，人类活动的重要特征就是人口的城市化。作为传统地球物理学的一个新的发展领域，城市地球物理学就应运而生了。城市面临的环境问题和灾害减轻问题，都要求发展城市地下三维地图的科学基础。地下三维地图既是城市地球物理学的核心科学问题，也是我国地球物理学家面临的挑战和机遇。城市地球物理是地球物理学新的发展领域。     

G298 – A New Candidate γ Doradus Star in the Direction of the Globular Cluster M4

G298 = L3216 (V = 12.68, B?V = 0.59) is a field star in the direction of the globular cluster M4. It was used as one of our comparison stars in the past, now it is shown that G298 is a new γ Dor variable star with a period of 1.03099 day and peak to peak amplitude of about 0.02 mag in V. Its spectral type is F2 (IV ?).     

木星“大红斑”的旋转浅水实验模拟研究

在具有自由表面的旋转轨物面浅水实验系统上进行了可重复的系列模拟实验，在旋转随动坐标系中拍摄的照片和功率谱分析表明，确有大尺度持续存在的涡旋、漂移与演化产生，在一定条件下，呈现出一个自持的、长寿命的、沿与整体旋转方向相反方向漂移的反气旋孤立波涡旋（Rossby孤立波涡旋），这就是木星“大红斑”的实验室模型，实验结果证实，流体动力学不稳定主要来自于剪切和Coriolis力效应，由于远离平衡态的耗散系统的自组织，涌现出大尺度长寿命相干涡旋结构，受多次实验的启发，从流体动力学基本方程出发，在一定的实验条件下提出一个半经验模型，近似求出了Rossby孤立波涡旋解。     

Bivariate frequency analysis: discussion of some useful concepts in hydrological application

Basic concepts such as conditional probability distributions, conditional return periods, and joint return periods are important to understand and to interpret multivariate hydrological events such as floods and storms. However, these concepts are not well documented in the open literature. This paper assembles and clarifies these concepts, and illustrates their practical utility. Relationships between joint return periods and univariate return periods are also derived. These concepts and relationships are demonstrated by applying a bivariate extreme value distribution to represent the joint distribution of flood peak and volume from an actual basin. Copyright © 2002 John Wiley & Sons, Ltd.