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891.
892.
以清洁发展机制(CDM)广西珠江流域治理再造林项目为例,对项目及其5种造林模式临时核证减排量(temporary certified emission reduction,缩写为tCER)和长期核证减排量(long-term certified emission reduction,缩写为lCER)成本的动态变化进行了初步研究。结果表明:从项目期初到期末,整个项目及5种造林模式人工林的tCER成本均逐渐降低,其中项目成本由第一承诺期末的40.33 ¥/t CO2降至最后承诺期末的13.34 ¥/t CO2;lCER成本先降低后升高,在第一承诺期末均降至最小值,项目成本由第一承诺期末的40.33 ¥/t CO2增加至最后承诺期末的105.27 ¥/t CO2;各造林模式tCER和lCER成本均以枫香+杉木、枫香+马尾松较高,马尾松+荷木、马尾松+栎类较低,桉树最低;贴现率对项目tCER和lCER、桉树tCER、枫香+杉木lCER成本影响均较大,而对马尾松+栎类tCER和lCER成本影响均较小;对桉树一个轮伐期内的tCER成本进行了敏感性分析,单位面积碳贮量的变化对其影响较大;考虑木材收益时,项目期末tCER净现值为13.11 ¥/t CO2,从中反映了该CDM项目实施是可行的。 相似文献
893.
894.
回波强度定标和调校方法是保障CINRAD/SB回波强度测量精度的关键技术,方法不当会导致回波强度测量误差增大,直接影响雷达定量估测降水产品的可靠性。为了满足回波强度测量误差在±1 dBZ范围内的技术要求,根据雷达气象方程,通过对CINRAD/SB接收机测试通道、主通道、天馈系统相关影响回波强度测量误差的因素进行分析,提出了从接收机动态范围和雷达参数调整、线性通道增益定标目标常数定标,到测试通道参数调整的回波强度定标工作流程。总结出以线性通道增益定标目标常数定标为基准,采用测试通道参数测量法或基准法调校,以保证发射功率和接收机动态范围变化导致的回波强度测量误差得到在线实时校正,提高了CINRAD/SB回波强度测量精度。从接收机测试通道、主通道、天馈系统及发射功率4个方面,给出了回波异常的分析和诊断流程。并提出在接收机保护器前端增加机外信号注入口和定标信号功率检测功能,以利于机内外回波强度定标对比校准和消除测试通道参数变化导致回波强度测量误差的建议。 相似文献
895.
利用星载闪电探测仪OTD(optical transient detecter)和LIS(lightning imaging sensor)所获取的1995年6月—2006年4月的卫星闪电资料,结合NOAA Optimum Interpolation SST海温资料,分析我国近海海域的闪电分布时空特征以及闪电活动与该海域海温之间的相关性。结果表明:我国近海闪电密度平均值为3.39 fl·km~(-2)·a~(-1),其中,南海和渤海的闪电活动相对频繁,随着与海岸线间距离以及纬度的增加,该海域闪电密度逐渐下降;在春季和冬季,黑潮主干海域的海温值相对较高,该处闪电活动也明显强于同纬度的东海近海和太平洋海域,表明黑潮海域是强闪电活动区;在季节变化上,我国近海海域闪电活动与同海域海温呈明显正相关,相关系数达0.797,闪电活动与海温变化体现出了一致的变化趋势;而在年际变化上,我国近海海域闪电活动与该海域海温的线性相关不显著,说明我国近海海域海温的年际变化并不是引起该海域闪电活动年际变化的主要原因。 相似文献
896.
P. D. Safai S. Kewat G. Pandithurai P. S. Praveen K. Ali S. Tiwari P. S. P. Rao K. B. Budhawant S. K. Saha P. C. S. Devara 《Journal of Atmospheric Chemistry》2008,61(2):101-118
Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra
in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased
by about 1.4 times during intense foggy/hazy days. Concentrations of SO4
2−, NO3
−, NH4
+ and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic
during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH4 aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for
transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening
peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties
of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol
optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (<1 μm). AOD value at 0.5 μm
wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63).
OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution
of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby
did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing
during intense foggy/hazy days (+75.8 W/m2) than that during clear sky or less foggy/hazy days (+38 W/m2), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from −40 W/m2 during clear sky or less foggy/hazy days to −76 W/m2 during intense foggy/hazy days, mainly due to the scattering aerosols like SO4
2-. 相似文献
897.
Emilia K. Jin James L. Kinter III B. Wang C.-K. Park I.-S. Kang B. P. Kirtman J.-S. Kug A. Kumar J.-J. Luo J. Schemm J. Shukla T. Yamagata 《Climate Dynamics》2008,31(6):647-664
The overall skill of ENSO prediction in retrospective forecasts made with ten different coupled GCMs is investigated. The coupled GCM datasets of the APCC/CliPAS and DEMETER projects are used for four seasons in the common 22 years from 1980 to 2001. As a baseline, a dynamic-statistical SST forecast and persistence are compared. Our study focuses on the tropical Pacific SST, especially by analyzing the NINO34 index. In coupled models, the accuracy of the simulated variability is related to the accuracy of the simulated mean state. Almost all models have problems in simulating the mean and mean annual cycle of SST, in spite of the positive influence of realistic initial conditions. As a result, the simulation of the interannual SST variability is also far from perfect in most coupled models. With increasing lead time, this discrepancy gets worse. As one measure of forecast skill, the tier-1 multi-model ensemble (MME) forecasts of NINO3.4 SST have an anomaly correlation coefficient of 0.86 at the month 6. This is higher than that of any individual model as well as both forecasts based on persistence and those made with the dynamic-statistical model. The forecast skill of individual models and the MME depends strongly on season, ENSO phase, and ENSO intensity. A stronger El Niño is better predicted. The growth phases of both the warm and cold events are better predicted than the corresponding decaying phases. ENSO-neutral periods are far worse predicted than warm or cold events. The skill of forecasts that start in February or May drops faster than that of forecasts that start in August or November. This behavior, often termed the spring predictability barrier, is in part because predictions starting from February or May contain more events in the decaying phase of ENSO. 相似文献
898.
采用EOF分解和合成分析方法研究了1960-2003年山西夏季降水异常之北少(多)南多(少)型(第二类雨型)和山西省气温的变化异常.结果表明,两者具有较好的对应关系.分析了第二类异常雨型的时空分布,并给出相应的典型年份.EOF时间系数变化特征揭示了山西夏季降水第二类雨型有显著的年际振荡.利用合成分析,从500hPa位势高度场、纬向风、850hPa风场、700hPa水汽场和水汽输送场等物理量场研究了山西夏季第二类雨型的环流异常特征.结果表明,第二类雨型与弱的东亚夏季风相关联,北多南少和北少南多是弱夏季风的不同表现.山西省夏季降水北多南少年副高呈带状分布,位置偏北,强度较强;中高纬度地区异常波列呈大圆路径分布,在高纬度地区存在纬向排列的- -波列,同时在东亚大陆沿岸存在经向排列的- -波列.并且华北北部有西风异常,北支锋区偏北,由西南向东北水汽输送较强.北少南多年与之相反.海温场分析表明,第二类雨型与中北太平洋海温异常紧密相关. 相似文献
899.
Droughts and famines: The underlying factors and the causal links among agro-pastoral households in semi-arid Makueni district, Kenya 总被引:4,自引:0,他引:4
Chinwe Ifejika Speranza Boniface Kiteme Urs Wiesmann 《Global Environmental Change》2008,18(1):220-233
Famines are often linked to drought in semi-arid areas of Sub-Saharan Africa where not only pastoralists, but also increasingly agro-pastoralists are affected. This study addresses the interplay between drought and famine in the rural semi-arid areas of Makueni district, Kenya, by examining whether, and how crop production conditions and agro-pastoral strategies predispose smallholder households to drought-triggered food insecurity. If this hypothesis holds, then approaches to deal with drought and famine have to target factors causing household food insecurity during non-drought periods. Data from a longitudinal survey of 127 households, interviews, workshops, and daily rainfall records (1961–2003) were analysed using quantitative and qualitative methods. This integrated approach confirms the above hypothesis and reveals that factors other than rainfall, like asset and labour constraints, inadequate policy enforcement, as well as the poverty-driven inability to adopt risk-averse production systems play a key role. When linking these factors to the high rainfall variability, farmer-relevant definitions and forecasts of drought have to be applied. 相似文献
900.
近46年西藏高原昼夜降水变化趋势 总被引:4,自引:2,他引:2
选取西藏地区18个气象站1961~2006年逐时降水资料,分析近46年昼夜降水的变化趋势。结果显示:近46年,西藏大部分地区各时段夜雨率均呈减少趋势,昼雨率呈增多趋势;夜雨天数冬半年各区域都呈增多趋势,年和夏半年东北部和藏西北地区呈增多趋势,其他区域呈减少趋势,而昼雨天数大部分地区年、季都呈增多趋势。昼、夜雨率和雨次的年代际变率较大,各区域年代际变化不一致,无明显的增减趋势;夜雨率冬半年出现异常最多,各区域年、季多为异常偏少。昼雨率冬、夏半年出现异常较多,年和夏半年多异常偏少,冬半年基本上为异常偏多;夜雨天数夏半年出现异常的最多,东部地区以异常偏少居多,中西部地区以异常偏多为主。昼雨天数夏半年出现异常最多,南部边缘地区均为异常偏多,藏北地区也以偏多为主,其他区域多异常偏少。西藏大部分地区年、季昼夜雨率的大小更多依赖于降水强度,而非雨次的多少。 相似文献