利用MODIS资料定量判识沙尘暴方法研究

为了利用MOD IS资料对沙尘暴的范围和强度进行定量判识,应用多时次MOD IS多波段资料,在对沙尘暴、云、雪和沙漠光谱特征进行较为细致分析的基础上,寻找出能区分沙尘、云和地表的波段,构建了2个定量判别沙尘暴范围和强度的沙尘指数,并利用沙尘指数对2002~2005年多次MOD IS沙尘暴的范围和强度进行判识。研究结果表明:1)沙尘在反射光谱段的光谱特征为反射率随着波长的增加而增大,与土壤光谱特征相近;大粒径沙尘反射率增长速率大于小粒径沙尘。2)小粒径沙尘具有较典型的气溶胶特征,对0.46μm蓝光波段敏感,对1.6和2.1μm短红外波段不敏感。3)大粒径沙尘不具有气溶胶特性,对蓝光波段不敏感,对短波红外敏感。4)3.7μm和8.5μm是对沙尘敏感波段,2波段的差可以作为判别沙尘的指标,并在一定程度上反映沙尘强度。5)设计的2个沙尘指数对监测沙尘十分有效,且方法简单,适于业务应用。     

Study on Quantitative Identification Sand and Dust Storm Using MODIS Data

In order to detect the scope and the intensity quanti cationally, the spectrum characteristic of sand and dust storm was analyzed in detail by using several MODIS data; bands that can distinguish sand and dust from cloud and surface were detected; two indices for determining the scope and intensity of sand and dust storm were found out, and were tested in several storms. Our study result shows: 1) The spectral characteristic of sand and dust in solar wavelengths is that the reflectance increases with the increasing of the wavelength. This is similar to the characteristic of the spectrum of soil. Also, the reflectance of large size dusts increases faster than small size dusts. 2) Small size dusts show typical characteristic of aerosol, being sensitive to blue band of 0.46 μm and insensitive to short wave infrared bands of 1.6 and 2.1 μm. 3) Large size dusts do not have aerosol characteristic, not sensitive to blue band but sensitive to short wave infrared bands. 4) Bands of 3.7 and 8.5 μm are sensitive to dusts. The difference of two bands can be used to identify sands and dusts and reflect the intensity to a certain extent. And 5) the two indices are very effective to monitor sands and dusts by testing a lot of sand and dust storm cases during the period of 2002-2005. Also, the method is simple and easy for operational use.     

江西暴雨预报的客观天气学模型和物理诊断模型研究

文章介绍了江西区域暴雨的客观天气学模型、物理诊断模型、预报流程以及利用数值化云图进行暴雨落区短时跟踪预报的方法。并给出了1992～1995年汛期模型的试报结果。     

蒙古气旋爆发性发展导致的强沙尘暴个例研究

对2001年4月6～7日发生在中国北方的一次强沙尘暴过程,从沙尘源、干旱气候背景、天气系统及起沙和扬沙的动力机制进行了初步研究,揭示了强沙尘暴与蒙古气旋和高空急流活动的关系.得出:位于内蒙古西部的巴丹吉林沙漠和中部的浑善达克沙地,是沙尘暴的主要沙尘源区;持续两年的干旱是强沙尘暴形成的气候背景;蒙古气旋的爆发性发展和冷锋后大风是起沙的主要动力;湍流输送和高空急流出口区左侧气流辐散强迫形成的干对流上升气流是沙尘向高空输送的动力机制等结论.作者认为强沙尘暴是挟带大量沙尘的强干对流风暴.     

北京地区一次降雹过程和冰雹微物理特征

对2000年5月17日降雹现场进行了实地考查，同时收集了部分冰雹样品，进行了冰雹切片实验，分析研究了雹谱、雹击带和冰雹的微物理结构特征。应用天气图、雷达探测冰雹云回波和探空资料，分析了冰雹云形成的天气条件、大气层结和冰雹云回波结构。     

山东半岛风电爬坡事件的识别与天气分析研究

根据山东省24个风电场2013年全年每15 min的风电输出功率实测数据以及相应的WRF(Weather Research and Forecasting)气象预测数据和FNL(Final Operational Global Analysis)再分析资料,分析了区域大规模风电爬坡现象与大尺度天气系统演变的联系。结果显示,大尺度天气系统,特别是阻塞高压系统,是诱发山东地区大规模风电爬坡的重要因素;爬坡事件的预测应当考虑天气演变的因素。进一步结合旋转门(The Swinging Door,TSD)算法重新讨论了爬坡事件的定义与识别,并在此基础上分析了爬坡事件的特征及其可预报性;并指出风电功率上报、考核制度应当重点考虑爬坡时间段的预测水平,以提高电网运行的稳定性。     

华北和北京的酷暑天气 Ⅰ. 历史概况及个例分析

如果将日最高气温超过３５ ℃的天气定义为酷暑天气, 则近６０ 年的资料统计表明, 北京出现酷暑天气的年频率高达８１ ％ , 并不少见, 尤以４０ 年代和９０ 年代明显偏多。１９４２ 年６ 月和１９９９ 年７ 月都出现≥４２ ℃的酷暑天气。分析表明, 北京和华北酷暑天气的出现与大环流形势密切相关, 大陆副热带高压维持于华北上空是其主要因素, 空气下沉增温是酷暑的主要机制, 而大城市的热岛效应则可使城区百叶箱气温再增高２ ℃左右。     

一次辽宁秋季暴雨天气的诊断分析

使用1.0°×1.0°NCEP再分析资料,对2006年10月21—22日深秋暴雨在天气形势分析的基础上,进行物理量诊断。结果表明:在有利的环境背景形势下,高位涡从对流层高层向低层伸展并形成湿位涡柱,引起气旋性环流与低涡环流叠加。对流层低层的湿斜压性增强,引起低层的锋区加强及垂直涡度发展,高空入侵干冷空气锲入底层,低层暖湿空气强迫抬升,使地面发展为气旋;高低空急流耦合产生上升气流,同时较强的补偿下沉运动激发上升运动加强,使次级环流加强,触发不稳定能量的释放;低空急流和超低空急流向辽宁输送暖湿空气及能量,对流层中低层形成湿柱并积聚高不稳定能量;中尺度气旋、高低空急流、湿位涡柱、次级环流上升支、地面高水汽含量湿区、高假相当位温出现的时间、强度、位置和结构决定了暴雨的时间和落区。     

Erratum to：A Case Study of the November 2012 Mixed Rain-Snow Storm over North China

正Erratum to:Acta Meteor Sinica DOI 10.1007/sl3351-013-0510-3The original version of this article unfortunately contained a mistake.The presentation of DOI number was incorrect.The corrected DOI number is 10.1007/sl3351-013-0512-1     

Urban Heat Island and Boundary Layer Structures under Hot Weather Synoptic Conditions: A Case Study of Suzhou City, China

A strong urban heat island (UHI) appeared in a hot weather episode in Suzhou City during the period from 25 July to 1 August 2007. This paper analyzes the urban heat island characteristics of Suzhou City under this hot weather episode. Both meteorological station observations and MODIS satellite observations show a strong urban heat island in this area. The maximum UHI intensity in this hot weather episode is 2.2℃, which is much greater than the summer average of 1.0℃ in this year and the 37-year (from 1970 to 2006) average of 0.35℃. The Weather Research and Forecasting (WRF) model simulation results demonstrate that the rapid urbanization processes in this area will enhance the UHI in intensity, horizontal distribution, and vertical extension. The UHI spatial distribution expands as the urban size increases. The vertical extension of UHI in the afternoon increases about 50 m higher under the year 2006 urban land cover than that under the 1986 urban land cover. The conversion from rural land use to urban land type also strengthens the local lake-land breeze circulations in this area and modifies the vertical wind speed field.     

Smallholder Maize Production and Climatic Risk: A Case Study from Mexico

The article explores the strategies employed by smallholder farmers in Mexico to cope with the affects of climatic variability, and how seasonal climate forecasts may assist these farmers in mitigating climatic risk. Recognizing that the decisions of smallholder farmers are intricately tied to the political-economic circumstances in which they operate, the article discusses how agricultural policy in Mexico affects the vulnerability of small-scale producers and may inhibit their ability to use climatic forecasts to their advantage. The article first reviews the literature on smallholder adaptation in Mexico, and discusses briefly policy and institutional issues affecting adaptation at the farm-level. Using the case of small-scale maize producers in Tlaxcala, Mexico, as an illustration, the article then argues that political-economic uncertainty outweighs climatic variability as a determinant of the production strategies of small-scale producers. In these circumstances, the farmers are unlikely to use new seasonal climate forecasts.     

Aerosol Data Assimilation Using Data from Fengyun-3A and MODIS:Application to a Dust Storm over East Asia in 2011

Aerosol optical depth(AOD) is the most basic parameter that describes the optical properties of atmospheric aerosols,and it can be used to indicate aerosol content. In this study, we assimilated AOD data from the Fengyun-3 A(FY-3 A) and MODIS meteorological satellite using the Gridpoint Statistical Interpolation three-dimensional variational data assimilation system. Experiments were conducted for a dust storm over East Asia in April 2011. Each 0600 UTC analysis initialized a24-h Weather Research and Forecasting with Chemistry model forecast. The results generally showed that the assimilation of satellite AOD observational data can significantly improve model aerosol mass prediction skills. The AOD distribution of the analysis field was closer to the observations of the satellite after assimilation of satellite AOD data. In addition, the analysis resulting from the experiment assimilating both FY-3 A/MERSI(Medium-resolution Spectral Imager) AOD data and MODIS AOD data had closer agreement with the ground-based values than the individual assimilation of the two datasets for the dust storm over East Asia. These results suggest that the Chinese FY-3 A satellite aerosol products can be effectively applied to numerical models and dust weather analysis.     

基于雷达资料四维变分同化和三维云模式对一次超级单体风暴发展维持热动力机制的模拟分析

利用三维云尺度数值模式和雷达资料快速更新循环四维变分同化(4DVar)技术,对京津冀地区一次强降水超级单体风暴发展演变的热动力机制进行了数值模拟和结果分析,并结合雷达、加密探空和自动站资料,揭示了快速变化的近风暴大气环境及风暴自身的热动力三维特征对超级单体形成、发展和演变的影响.雷达回波观测分析表明,这是一次由多单体合...     

孟湾风暴影响高原暴雪的个例分析:基于倾斜涡度发展的研究

基于湿位涡(MPV)诊断分析和倾斜涡度发展(SVD)理论,研究了2007年11月一次孟加拉湾热带风暴北上造成青藏高原暴雪的天气事件。结果表明:热带风暴螺旋云系移动至高原东南部受陡峭地形抬升与高层北侧下滑的干冷空气(MPV1正值带)相交汇是导致这次天气过程的重要原因。由于等熵面密集且明显倾斜,在降雪区上空附近大气弱稳定区,负的MPV2对总湿位涡MPV的贡献超过了MPV1,SVD得到较大增长,同时使得MPV0,导致条件性对称不稳定的产生,有利于倾斜涡度的发展。条件性对称不稳定机制是这次暴雪发生、发展的一种可能的重要机制。     

基于高分数据的边境示范村建设和生态环境监测——以玉麦乡为例

选取高分1号和2号卫星数据,利用ENVI和ArcGIS软件对西藏山南市隆子县玉麦乡的建设规模和生态环境进行研究,结果表明：2015～2019年,玉麦乡建筑物面积和道路长度增加了0.25km²和1.18km;冬季积雪覆盖面积减少80.17km2和1.18km;冬季积雪覆盖面积减少80.17km²;2019年相较于2015年,东部地区植被相对较好,中、高覆盖度植被面积分别增加了79.00km2;2019年相较于2015年,东部地区植被相对较好,中、高覆盖度植被面积分别增加了79.00km²和147.52km2和147.52km²。     

Q Vector Analysis of Torrential Rainfall from Meiyu Front Cyclone： A Case Study

Following similar derivation of quasi-geostrophic Q vector （Q^C）, a new Q vector （Q^N） is constructed in this study. Their difference is that the geostrophic wind in quasi-geostrophic Q vector is replaced by the wind in Q^N vector. The diagnostic analysis of Q^N vector is compared with that of Q^G vector in the case study of a typical Meiyu front cyclone （MYFC） occurred over Changjiang-Huaihe regions during 5-6 July 1991. The results show that the Q^N vector has more diagnostic advantages than Q^G vector does. Convergence of Q^N vector at 700 hPa is found to be a good indicator to mimic the horizontal distribution of precipitation. Q^N vector is further partitioned into four components： Q^Nalst （along-stream stretching）,Q^Ncurv （curvature）,Q^Nshdv （shear advection）, and Q^Ncrst （cross-stream stretching） in a natural coordinate system with isohypse （PG partitioning）. The application of Q^N PG partitioning in the MYFC torrential rain indicates that PG partitioning of Q can identify dominant physical processes. The horizontal distribution of 2V·Q^Nalst is similar to that of 2V·Q^N and mainly accounts for 2V·Q^N during the entire period of Meiyu. The effects of Q^Ncurv on rainfall enhancement fade from the mature stage to decay stage. Qshdv enhances precipitation significantly as the MYFC develops, and the effect weakens rapidly when the MYFC decays during its eastward propagation. Q^Ncrst shows little impacts on rainfall during the onset and mature phases whereas it displays significant role during the decay phase.Q^N alst and Q^Nshdv and Q^Ncrst show cancellation only during the decay period.     

Monitoring Carbon Dioxide from Space:Retrieval Algorithm and Flux Inversion Based on GOSAT Data and Using CarbonTracker-China

Monitoring atmospheric carbon dioxide(CO_2) from space-borne state-of-the-art hyperspectral instruments can provide a high precision global dataset to improve carbon flux estimation and reduce the uncertainty of climate projection. Here, we introduce a carbon flux inversion system for estimating carbon flux with satellite measurements under the support of "The Strategic Priority Research Program of the Chinese Academy of Sciences—Climate Change: Carbon Budget and Relevant Issues". The carbon flux inversion system is composed of two separate parts: the Institute of Atmospheric Physics Carbon Dioxide Retrieval Algorithm for Satellite Remote Sensing(IAPCAS), and Carbon Tracker-China(CT-China), developed at the Chinese Academy of Sciences. The Greenhouse gases Observing SATellite(GOSAT) measurements are used in the carbon flux inversion experiment. To improve the quality of the IAPCAS-GOSAT retrieval, we have developed a post-screening and bias correction method, resulting in 25%–30% of the data remaining after quality control. Based on these data, the seasonal variation of XCO_2(column-averaged CO_2dry-air mole fraction) is studied, and a strong relation with vegetation cover and population is identified. Then, the IAPCAS-GOSAT XCO_2 product is used in carbon flux estimation by CT-China. The net ecosystem CO_2 exchange is-0.34 Pg C yr~(-1)(±0.08 Pg C yr~(-1)), with a large error reduction of 84%, which is a significant improvement on the error reduction when compared with in situ-only inversion.     

太湖地区冬小麦田与蔬菜地N2O排放对比观测研究

2003年11月8日至2004年6月5日对太湖地区相邻的蔬菜地和稻麦轮作生态系统的冬小麦田,在当季不施肥情况下的N2O排放进行了田间同步对比观测,分析了N2O排放时间变化以及土壤湿度、土壤温度、土壤速效氮含量和农业管理措施对N2O排放的影响。研究结果表明,小麦播种前的耕翻(表层大约7cm土壤旋耕)处理不会明显改变稻麦轮作农田整个旱地阶段的N2O排放总量,但却使小麦生长季初期的N2O排放明显减弱69%(p<0.01,p为相关概率),使小麦生长季后期的N2O排放明显偏高2.6倍(p<0.05),而对其余时间段的N2O排放作用不明显。与长期实行稻麦轮作的旱地阶段农田相比,由稻田改种蔬菜20多年的蔬菜地,其整个观测期的N2O排放总量比免耕处理小麦田同期的排放高85%(p<0.05),比耕翻处理小麦田同期的排放高99%(p<0.01)。蔬菜地N2O排放偏高的原因是土壤速效氮,特别是铵态氮含量明显偏高(p<0.01)。     

A New Typhoon Bogus Data Assimilation and its Sampling Method: A Case Study

In this study,the authors introduce a new bogus data assimilation method based on the dimension-reduced projection 4-DVar,which can resolve the cost function directly in low-dimensional space.The authors also try a new method to improve the quality of samples,which are the base of dimension-reduced space projection bogus data assimilation (DRP-BDA).By running a number of numerical weather models with different model parameterization combinations on the typhoon Sinlaku,the authors obtained two groups of samples with different spreads and similarities.After DRP-BDA,the results show that,compared with the control runs,the simulated typhoon center pressure can be deepened by more than 20 hPa to 30 hPa and that the intensity can last as long as 60 hours.The mean track error is improved after DRP-BDA,and the structure of the typhoon is also improved.The wind near the typhoon center is enhanced dramatically,while the warm core is moderate.