中国地表感热的气候计算及其分布

讨论了我国地表感热的气候计算问题,提出以鲍文比法为基础的感热气候计算式,并据此计算出全国215站月、年平均感热通量密度,进而分析了其在全国的时空分布特点。     

A novel ozone sensor for direct eddy flux measurements

A small, lightweight (1.5 kg) and fast-response ozone sensor for direct eddy flux measurements has been built. The basis for detection is the chemiluminescence of an organic dye adsorbed on dry silica gel in the reaction with ozone. The chemiluminescence is monitored with a cheap and small blue-sensitive photomultiplier. At a flow rate of 100 l min^-1 the ozone sensor has a 90% response time of significantly better than 0.1 s with a detection limit lower than 50 ppt at S/N=3. There are no interferences from other atmospheric trace gases like NO_x, H₂O₂ and PAN. Water vapour and SO₂ enhance the chemiluminescence efficiency of the ozone sensor. Since their response times are 22 seconds and 30 minutes, respectively, no correlation between rapid ozone fluctuations and those of these two trace gases is noticed by the ozone sensor when operating at a frequency of 10 Hz.The ozone sensor was tested for several weeks in continuous measurements of ozone fluxes and deposition velocities over different croplands using the eddy correlation technique. Good agreement was found between ozone dry deposition velocities derived from profile measurements and by eddy correlation.     

任意点震源τ-P域地震图的解及AVO分析

用严格的数学推导得出τ-P域地震图的解析解。分析表明,τ-P域中地震图的子波可表示为激发震源子波的积分形式,决定反射波振幅的因素是平面波反射系数、反射界面上覆介质的波速以及方向因子。这些结果说明:1.在τ-P域进行AVO分析是可行的,并具有更高的精度;2.从一种新的途径可以进行速度函数的反演计算。     

南海到西太平洋地区水汽输送和山东夏季降水量奇异值分解分析

利用奇异值分解(SVD)方法和山东省26个代表站1951～2000年6～8月降水量、NCEP／NCAR再分析1958～1998年1～12月925～300hPa5层月平均比湿和风场资料,分析了山东夏季降水与前期(冬季、春季)及同期(夏季)南海到西太平洋地区水汽输送之间相关场的分布型,从中找出了遥相关的“关键区”,并对找到的“关键区”的可靠性进行了验证。研究表明,山东夏季降水与前期(冬季、春季)和同期(夏季)南海到西太平洋地区水汽输送相关较好,春季的相关程度最高,冬季次之,夏季最小。     

A preliminary study on sediment flux in the Changjiang Delta during the postglacial period

During the last 7000 years since the Changjiang Delta was formed, how much sediment brought by the Changjiang River remained in the modern Changjiang Delta? And how much sediment was delivered into the sea and adjacent coasts? These are very important que…     

Observational estimation of heat budgets on drifting ice and open water over the Arctic Ocean

It is of major scientific interests to determine the parameters of momentum, heat and vapor exchange in the planetary boundary layer in order to study the effects of ocean-ice-atmosphere interactions and their feedback mechanisms on global climate[1]. Lin…     

Fluxes of CO<Subscript>2</Subscript>, CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O from alpine grassland in the Tibetan Plateau

Using static chamber technique,fluxes of CO2,CH4 and N2O were measured in the alpine grassland area from July 2000 to July 2001,determinations of mean fluxes showed that CO2 and N2O were generally released from the soil,while the alpine grassland accounted for a weak CH4 sink.Fluxes of CO2,CH4 and N2O ranged widely.The highest CO2 emission occurred in August,whereas almost 90?of the whole year emission occurred in the growing season.But the variations of CH4 and N2O fluxes did not show any clear patterns over the one-year-experiment.During a daily variation,the maximum CO2 emission occurred at 16:00,and then decreased to the minimum emission in the early morning.Daily pattern analyses indicated that the variation in CO2 fluxes was positively related to air temperatures(R^2=0.73)and soil temperatures at a depth of 5 cm(R^2=0.86),whereas daily variations in CH4 and N2O fluxes were poorly explained by soil temperatures and climatic variables.CO2 emissions in this area were much lower than other grasslands in plain areas.     

利用场地观测计算地表通量

高原地表的感热和潜热通量在亚洲季风系统中有很重要的作用。由于高原地域辽阔，且自然环境较严酷，不利于建立完善的地面观测系统。因此，卫星遥感观测就成为测算高原整体感热和潜热通量的有效工具。地面场地的观测结果作为地表通量的真实值，对于卫星遥感测算是非常重要的。它也为构建陆面—大气模型提供了科学依据，是卫星资料的资料同化系统中的重要组成部分。 计算场地热量通量有几种不同的处理方法。最简单的方法利用有效的观测和试验的参数，可以给出稳定连续的估计。愈精确的Bowen比或者廓线的观测能给出愈精确的信息。综合了湍流测量及辐射测量、土壤热通量的观测结果的估计对陆面—大气相互作用进行了详细的描述，以适应模式的发展。从1998年开始，这些方法联合应用到青藏高原；场地通量观测方面的成果以及目前对其理解将在本文中做一概述。     

Study on the processing method of nighttime CO_2 eddy covariance flux data in ChinaFLUX

At present, using Eddy Covariance (EC) method to estimate the "true value" of carbon sequestration in terrestrial ecosystem arrests more attention. However, one issue is how to solve the uncertainty of observations (especially the nighttime CO2 flux data) appearing in post-processing CO2 flux data. The ratio of effective and reliable nighttime EC CO2 flux data to all nighttime data is relatively low (commonly, less than 50%) for all the long-term and continuous observation stations in the world. Thus, the processing method of nighttime CO2 flux data and its effect analysis on estimating CO2 flux annual sums are very important. In this paper, the authors analyze and discuss the reasons for underestimating nighttime CO2 flux using EC method, and introduce the general theory and method for processing nighttime CO2 flux data. By analyzing the relationship between nighttime CO2 flux and air fraction velocity u., we present an alternate method, Average Values Test (AVT), to determine the thresholds of fraction velocity (u.c) for screening the effective nighttime CO2 flux data. Meanwhile, taking the data observed in Yucheng and Changbai Mountains stations for an example, we analyze and discuss the effects of different methods or parameters on nighttime CO2 flux estimations. Finally, based on the data of part ChinaFLUX stations and related literatures, empirical models of nighttime respiration at different sites in ChinaFLUX are summarized.     

不同生态系统CO2通量和浓度特征分析研究

本文利用1993～1994年日本国家农业环境研究所与中国科学院沙漠研究所合作在内蒙古奈曼地区实测的7种不同生态系统（沙丘、轻度放牧草原、中度放牧草原、重度放牧草原、无放牧草原、玉米田和大豆田）的净辐射、土壤热通量、两个高度的CO2浓度、温度、湿度和风速等资料，采用空气动力学方法，计算了CO2通量及其与环境和人为干扰因子的关系，并分析了不同下垫面的光合作用特征. 结果表明：各种下垫面CO2通量的共同特点是：在白天，CO2通量和梯度的输送方向是从大气向植被，在中午（11～13时）输送达到负的最大值； 在夜间，CO2通量和梯度输送方向与白天相反，是从植被向大气，在早晨（3～5时）达到正的最大值. 植被覆盖率及生物量不同的下垫面光合作用强度有明显差异，天气状况对光合作用也有一定影响.