基于MODIS卫星数据对艾比湖水域面积变化的监测

艾比湖的松散沉积物裸露区沉淀物质颗粒细小，细盐漠粉尘受阿拉山口大风主通道作用，向东南快速扩展，是新疆北疆地区主要沙源之一。Terra／MODIS卫星数据具有时效性强，成本低的特点，适宜进行湖泊水域面积的监测。我们进行2004年4-12月湖面积的监测发现，5月份以后，艾比湖水位逐渐下降，7，10月为艾比湖的枯水期，10月艾比湖水域面积出现最小值；冬半年(11—4月)为艾比湖的丰水期。通过与1998年监测的艾比湖水域面积数据比较得出2004年艾比湖各月的面积均比1998年有所增加，艾比湖地区生态环境有明显好转。     

精河县气象因子对艾比湖湖水面积变化的影响分析

利用2005--2009年250mx250m的EOS／MODIS卫星资料,对艾比湖湖水进行水体判识与面积计算,得到了逐旬的遥感动态监测数据,与周边气象台站同期气象因子进行了统计分析。结果表明：精河县气象因子变化对艾比湖湖水面积产生的影响较其它气象站点明显;影响艾比湖湖水面积变化的气象因子较多,其中主要有降水、风速和相对湿度影响,而与降水和风速有较好的主成分线性回归关系。     

艾比湖地区的风沙

本文就艾比湖地区的风沙及与之相关的气候和生态,作了些粗浅的探讨. 一、艾比湖的地形与气候艾比湖又名布尔哈齐湖,位于东径82°31'-83°30',北纬44°30'-45°30',在阿拉山口东南方,精河县北面,面积约1070平方公里,湖面海拔194米(根据1968年国     

伊犁地区沙尘暴天气的卫星云图分析及其山区黄土层来源的探讨

利用NOAA气象卫星的遥感资料，发现了造成伊犁天山山区黄土沉积的沙尘暴天气的3条沙尘暴移动路径：第I类型及路径－阿拉伯海急流云北上与南下的冷锋云系相结合－由巴尔喀什湖向阿拉山口路径；第Ⅱ类型及路径－孟加拉湾急流云系翻越横断山脉横穿塔里木盆地腹部－阿拉山口、艾比湖沙尘翻山路径；第Ⅲ类型及路径－塔里木盆地沙尘翻越天山山区－塔里木盆地沙尘翻山路径。且分析了3个沙尘源地。     

艾比湖1961－2001年的演化特点及机制分析

利用40 a的实测数据分析艾比湖的演化特点及机制。研究表明:艾比湖气候恶化,干旱少雨,蒸发量大,特别是与特殊的地形地貌相匹配,风多风大,沙尘暴和浮尘活动频繁。入湖水量逐年减少,湖面蒸发量大,湖泊面积处于萎缩阶段。影响湖泊演化的因子主要是气候变化及人类活动。     

艾比湖流域气温变化特征分析

利用艾比湖流域近40a来气温资料,分析了气温的变化特征,结果表明:艾比湖流域气温有着明显上升的趋势,尤其以20世纪90年代最为明显.艾比湖流域的气温升高具有明显的季节性差异,表现为冬季变暖明显,而春季变暖的趋势较为缓慢,艾比湖流域年气温的演变特点与新疆的基本一致.艾比湖流域最高和最低气温的变化普遍存在不对称性.     

极地海冰异常对我国夏季大气环流和降水影响的数值研究

利用全球大气环流谱模式分别进行了南极和北极海冰面积异常偏大和偏小的数值试验，对６－８月的结果进行了对比分析，讨论了极地海冰异常对我国夏季大气环流和降水的可能影响。结果表明，南极或北极海冰面积异常偏大，则我国夏季风变弱，特别蝇使得南亚高压、西北太平洋副热带高压等减弱。南极海冰面积偏大使得我国黄河－长江－带地区降水减少，北极海冰面积偏大，造成我国东部地区的降水量有所减少，模拟结果与统计分析相一致。可同     

北半球冬季雪盖对南宁地区盛夏降水的影响

利用卫星观测的1973－2001年北半球雪盖资料，分析了北半球、欧亚、北美雪病面积变化与南宁地区盛厦6－8月降水的关系，结果表明南宁地区盛夏降水与冬季雪盖面积相关显著。     

基于数字遥感技术的艾比湖地区荒漠化监测

由于MODIS数据具有高时间分辨率、连续性好、获取成本低的特点,本文选择MODIS作为主要数据源,结合在美国地质勘探局网站下载的NOAA-NDVI数据,研究了艾比湖地区荒漠化现状及动态变化监测的方法。主要解决了MODIS数据和NOAA-NDVI荒漠化信息的提取的问题。分析了艾比湖地区近2a及近11a不同荒漠化等级的变化。艾比湖地区从2002年至2004年荒漠化趋于严重,但1993年较2004年荒漠化程度减轻,即在这11a中荒漠化程度呈现波动变化,但总体趋势呈好转迹象。     

北极海冰对青海省春季（3—5月）降水的可能影响

用北极海冰面积指数及北半球500hPa高度资料、青海省春季降水资料，分析了它们之间的相互关系。结果表明北极海冰面积Q指数和M指数与我省春季降水的相关性较为一致，即相关性较好的区域皆为Ⅱ区，相关性较好的月份毕为当年1、3、4月及春季3－5月和前一年的6－8月；海冰是通过影响大气环流系统从而影响我省春季降水的，当年春季和前一年夏季海冰面积的变化对青海省春季降水的影响最明显。     

Stochastic Modeling of the Van Lake Monthly Level Fluctuations in Turkey

Summary  Planning, design, construction and operation of lakeshore structures require information about the future likely extremes of the lake levels at a given risk percentage. Alternative future likely synthetic sequences can be numerically generated provided that the underlying generating mechanism of the lake level fluctuation phenomenon is identified. Simple linear and periodic nonlinear models are used for modeling the deterministic part in the lake level records. Linear trend is eliminated from the original lake level historic data by regression line technique. The nonlinear part needs two stages for its identification. First Fourier series is applied to model interannual periodicities in the lake level fluctuation series and then monthly standardization procedure is applied for seasonal periodic nonlinear component modeling. A second order Markov model is found suitable for the remaining stochastic parts. The application of the methodology is presented for the Lake Van monthly level data in eastern Turkey. Suitable models are identified and their parameters are estimated for trend, periodic and stochastic parts. Likely, synthetic lake levels are generated by the stochastic model and hence lake level extreme values are depicted for the next 2, 6, 12, 24, 60 and 120 months with risk calculations. Such risk calculations take into account the stochastic characteristics of the lake level fluctuations only. The deterministic parts as linear trends and periodicities are added to the stochastic extreme events for the actual simulation of the lake levels. The model presented in this paper is not for time prediction of future lake levels but rather for the simulation of possible equally likely extreme lake level value occurrences over any desired future period. Received April 22, 1998/Revised July 28, 1999     

Spatial distribution and long-term trends of water transparency in Lake Ladoga

Based on the analysis of the surface water transparency (the depth of the Secchi disk disappearance), a seasonal trend of transparency for the entire lake water area was derived for the largest European lake, Lake Ladoga, on an equidistant grid and for limnetic regions. A spatial distribution of monthly mean water transparency of Lake Ladoga is considered from May to October. Climatic trends of transparency are assessed for the period from 1905 to 2003. The climatic trends are analyzed with a linear model used for each month from May to September. The areas with significant negative trends are singled out. A mean trend value is 0.02 m/year. The character of a spatial trend distribution changes depending on the month. In summer, the area with significant trends increases and covers about half of the lake water area. In the spring and in the fall, this area is much smaller and coincides with the southern regions of the lake.     

Enhancing monthly lake levels forecasting using heuristic regression techniques with periodicity data component: application of Lake Michigan

Theoretical and Applied Climatology - This study investigates the accuracy of three different techniques with the periodicity component for estimating monthly lake levels. The three techniques are...     

鄱阳湖影响过湖对流强度的数值模拟及机理分析

湖陆下垫面的非均匀性对强对流天气的发展演变有很大的影响。鄱阳湖是我国最大的淡水湖,湖面积具有明显的月变化和季节变化,而模式中的下边界一般默认湖面积不变,这与实际情况的差异较大,必然带来模式预报误差。利用WRF模式对夏季夜间发生在鄱阳湖地区的一次强对流天气过程进行数值模拟,并通过湖面积变化的敏感性试验,深入研究鄱阳湖对强对流天气发展演变的影响及其机理,结果表明：夏季夜间湖面上空2 m温度明显高于陆面,向湖陆风在湖面上空辐合上升,岸边则存在下沉辐散气流。这导致降水在湖西岸减弱、湖上空增强。随后用去湖敏感性试验印证了鄱阳湖的暖湖效应,湖泊的存在能够通过激发陆风次级环流对湖西岸（湖面）上空降水起抑制（促进）作用。去湖试验的降水在湖西岸增强20%,在湖面上空减弱16%,体现出湖泊对降水强度的重要影响。此外,还发现湖面积扩大1.5、2.5、3.5、4.0倍的扩湖敏感性试验的降水在湖面上空分别增幅7%、16%、30%、43%,进一步证实了强对流强度对鄱阳湖面积变化较为敏感。这指示我们在预报夏季夜间穿湖而过的强对流天气时,应重点关注其可能存在的入湖前减弱、入湖后增强的变化趋势。同时,在利用数值模式模拟湖区强对流天气过程时,如果湖面积与模式中默认的湖面积相差较大,则应考虑将实际湖面积引入模式下边界,以期提升模式对于湖区对流的预报能力。     

西藏冰湖溃决灾害事件极端气候特征

以1960年以来西藏境内已有记载的27次冰湖溃决灾害事件作为研究对象,基于西藏国家气象站点长时间序列（有效记录至今）日气温和日降雨数据,计算得到16个极端气温指数和6个极端降雨指数。通过主成分变换,提取综合极端气温指数和综合极端降雨指数,并进行历史（10年内对比）极端气候特征对比,获得冰湖溃决灾害发生当年及当月极端气候状态,结果表明西藏冰湖溃决灾害发生期（当年及当月）极端气候特征显著,反映极端气候状态对于激发西藏冰湖溃决灾害发生的重要贡献,具体表现为：(1) 67%（18次）的冰湖溃决事件发生当年综合极端气温指数和综合极端降雨指数均大于前期50%年份的综合极端气候指数,其中,13次灾害发生当年极端气候异常水平超过前期70%年份;(2)已有灾害暴发月份记载的25次冰湖溃决事件中,19次冰湖溃决事件发生当月极端气候指数异常偏高,11次冰湖溃决事件发生当月极端气温和极端降水均大于75%往年同期综合极端气候指数;(3)部分灾害事件如扎日错（1981年6月)、龙纠错溃决（2000年8月）等,灾害发生当年极端气温状态低于往年,而暴发当月综合极端气温指数和综合极端降雨指数均大于历史同期水平,表现为加剧状态;(4)所有冰湖溃决灾害发生当月的综合极端气温指数均高于往年同期指数,表明短历时极端气温事件对高原冰湖溃决灾害形成具有重要影响。     

Application of the Canadian regional climate model to the Laurentian great lakes region: Implementation of a lake model

Abstract

This study reports on the implementation of an interactive mixed‐layer/thermodynamic‐ice lake model coupled with the Canadian Regional Climate Model (CRCM). For this application the CRCM, which uses a grid mesh of 45 km on a polar stereographic projection, 10 vertical levels, and a timestep of 15 min, is nested with the second generation Canadian General Circulation Model (GCM) simulated output. A numerical simulation of the climate of eastern North America, including the Laurentian Great Lakes, is then performed in order to evaluate the coupled model. The lakes are represented by a “mixed layer” model to simulate the evolution of the surface water temperature, and a thermodynamic ice model to simulate evolution of the ice cover. The mixed‐layer depth is allowed to vary spatially. Lake‐ice leads are parametrized as a function of ice thickness based on observations. Results from a 5‐year integration show that the coupled CRCM/lake model is capable of simulating the seasonal evolution of surface temperature and ice cover in the Great Lakes. When compared with lake climatology, the simulated mean surface water temperature agrees within 0.12°C on average. The seasonal evolution of the lake‐ice cover is realistic but the model tends to underestimate the monthly mean ice concentration on average. The simulated winter lake‐induced precipitation is also shown, and snow accumulation patterns on downwind shores of the lakes are found to be realistic when compared with observations.     

胡杨树轮δ13C记录的艾比湖地区夏季最高温度变化

摘要：艾比湖是新疆北部生态环境最为敏感和脆弱的地区,这里分布的大片长龄胡杨是过去气候变化良好的记录体。本文利用艾比湖东岸的胡杨树轮资料,分析其宽度和稳定碳同位素组成,建立了树轮宽度年表和δ^13C序列,并对δ^13C序列进行了校正处理。树轮参数的气候意义分析表明胡杨树轮宽度所含的气候信息较少,而树轮δ^13C校正序列与精河夏季高温显著负相关,为荒漠平原区树轮气候研究提供了新的资料。研究区夏季的高温超过了光合作用的适宜温度,降低光合作用速率（A）,而地下水埋深较浅,叶片气候导度（g）并没有因受到水分条件限制而减小,在以上两个因素的共同作用下,叶片内部二氧化碳浓度（Ci）升高,导致胡杨δ^13C与夏季高温负相关关系。建立了胡杨树轮δ^13C校正序列与精河夏季高温的转换方程,方差解释量为33．0％。重建的精河145a来夏季高温序列反映了这一地区气候变暖的趋势,其升温的幅度高于北半球夏季升温幅度,但二者冷暖阶段变化并不完全一致。     

Effects of salinity upon evaporation from pans and shallow lakes near the Dead Sea

Summary Evaporation was evaluated for three shallow lakes near the Dead Sea with specific gravities (s.g.) of 1.26, 1.31 and 1.34, and for a hypothetical fresh lake of similar depth. The annual march of lake temperature was adequately predicted with an equilibrium temperature model. Predicted temperatures were only slightly affected by neglecting heat exchange between the lake and the underlying sediments. Modeled lake temperatures were then used in a modified Penman-type model and an alpha ratio model to generate evaporation estimates. The evaporation models were verified by comparison against 1950'ies water balance estimates of evaporation from the Dead Sea (s.g. about 1.18). Annual totals of evaporation predicted by the models for the shallow lakes declined from 2125 mm for fresh water (s.g. = 1.0) down to 588 mm for the most saline conditions (s.g. = 1.34). Evaporation was also measured from sunken pans in which s.g. was maintained at 1.0, 1.26, 1.31 and 1.34. Mean monthly pan coefficients (from lake/pan evaporation for equal s.g. values) ranged from 0.63 up to 1.03 as s.g. increased from 1.00 up to 1.34. The variations in coefficients are attributed to effects of salinity on the mechanisms that control the gain and loss of heat to the ponds and evaporation pans. The temperatures of the saline lakes were always somewhat warmer than the temperatures measured in the sunken pans, ranging from + 0.7 °C for s.g. of 1.26 up to + 1.3 °C for s.g. of 1.34; the corresponding value for the fresh condition was — 0.4 °C. The pan coefficients defined here for saline conditions will be useful for estimating actual water loss from brine-filled ponds used in commercial extraction of potash and other chemicals.With 2 Figures     

Climate change in the Tahoe basin: regional trends, impacts and drivers

The purpose of this study was to quantify the decadal-scale time trends in air temperature, precipitation phase and intensity, spring snowmelt timing, and lake temperature in the Tahoe basin, and to relate the trends to large-scale regional climatic trends in the western USA. Temperature data for six long-term weather stations in the Tahoe region were analyzed for trends in annual and monthly means of maximum and minimum daily temperature. Precipitation data at Tahoe City were analyzed for trends in phase (rain versus snow), decadal standard deviation, and intensity of rainfall. Daily streamflow data for nine gaging stations in and around the Tahoe basin were examined for trends in snowmelt timing, by two methods, and an existing record for the temperature of Lake Tahoe was updated. The results for the Tahoe basin, which contrast somewhat with the surrounding region, indicate strong upward trends in air temperature, a shift from snow to rain, a shift in snowmelt timing to earlier dates, increased rainfall intensity, increased interannual variability, and continued increase in the temperature of Lake Tahoe. Two hypotheses are suggested that may explain why the basin could be warming faster than surrounding regions. Continued warming in the Tahoe basin has important implications for efforts to manage biodiversity and maintain clarity of the lake.     

基于TM数据的湿地变化分析—以磴口县为例

利用2001、2006、2010年的TM遥感图像,采用目视解译的方法对磴口县湿地面积进行提取,结合气象数据,并对其变化进行分析。结果表明,2000—2010年,磴口县年降水呈现不及30a(1981—2010年)平均值的年份明显偏多,7—8月平均气温逐年上升;除内陆滩涂面积有所减少外,河流水体、湖泊坑塘水体以及湿地植被面积都有不同程度的增加,变化速率分别为2.06%、0.85%和4.65%,以湿地植被面积增加最为迅速。