适用于遥感应用的辐射传输高精度快速计算方法

准确的散射辐射方向特征与辐射传输能量守恒的物理要求是一切算法的有效性准则。在有限计算资源的限制下,寻找最优的有限展开算法,获得能量守恒物理要求下的散射方向特征的准确性,是多年来辐射传输算法的追求目标。在以有限流数离散化辐射传输方程进行数值求解过程中,要保证数值计算中的积分守恒,流数有限要求粒子散射相函数必须截断,而不合适的截断容易导致解的误差,尤其是当大气中存在强前向散射的大粒子时（如云滴、沙尘暴事件过后的沙尘）,截断的相函数会出现振荡,从而导致解的虚假振荡特性。散射相函数无限扩展可以消除这种虚假振荡,但容易导致数值积分能量不守恒和解的不稳定。本文从原理上对这种虚假振荡和不稳定现象进行了分析,并给出两种用较少流数达到较高的计算精度的高效计算方法,这些算法对于遥感方法研究、GCM气候模式中辐射强迫的参数化研究以及地气系统的能量收支研究,尤其是目前研究较多的云和沙尘等大粒子气候效应有重要意义。     

光学有效载荷高精度绝对辐射定标技术研究

随着多波段、多平台、高光谱分辨率遥感仪器的迅速发展,要求光谱辐射定标技术具有前所未有的高精度和长期测量稳定性。目前,传统辐射定标方法的精度已逐渐难以满足定量遥感应用的需求。本文提出了一种新型基于辐亮度标准探测器的高精度光谱辐射定标先进方法和技术,由于该方法可直接溯源至低温绝对辐射计,其绝对精度和长期稳定性优于传统的基于标准光源法,是提高中国目前光学遥感器实验室、星上和场地替代定标精度的有效途径。该方法已两次成功应用于中国“FY-2”气象卫星04和05星发射前外场定标,实际应用效果表明,它能够有效提高中国卫星遥感器的外场定标精度,对改善中国当前卫星遥感器各阶段定标精度,具有潜在的应用价值。     

Assimilating AMSU-a radiance data with the WRF hybrid En3DVAR system for track predictions of Typhoon Megi (2010)

The impact of assimilating radiances from the Advanced Microwave Sounding Unit-A (AMSU-A) on the track prediction of Typhoon Megi (2010) was studied using the Weather Research and Forecasting (WRF) model and a hybrid ensemble three-dimensional variational (En3DVAR) data assimilation (DA) system. The influences of tuning the length scale and variance scale factors related to the static background error covariance (BEC) on the track forecast of the typhoon were studied. The results show that, in typhoon radiance data assimilation, a moderate length scale factor improves the prediction of the typhoon track. The assimilation of AMSU-A radiances using 3DVAR had a slight positive impact on track forecasts, even when the static BEC was carefully tuned to optimize its performance. When the hybrid DA was employed, the track forecast was significantly improved, especially for the sharp northward turn after crossing the Philippines, with the flow-dependent ensemble covariance. The flow-dependent BEC can be estimated by the hybrid DA and was capable of adjusting the position of the typhoon systematically. The impacts of the typhoon-specific BEC derived from ensemble forecasts were revealed by comparing the analysis increments and forecasts generated by the hybrid DA and 3DVAR. Additionally, for 24 h forecasts, the hybrid DA experiment with use of the full flow-dependent background error substantially outperformed 3DVAR in terms of the horizontal winds and temperature in the lower and mid-troposphere and for moisture at all levels.     

卫星辐射率资料EnSRF同化及暴雨模拟应用

基于自主构建的WRF—EnSRF（Weather Researchand Forecasting—Ensemble Square—Root Filter）同化系统,同化了ATOVS（Advanced TIROS Operational Vertical Sounder）辐射率资料,以检验该系统同化卫星资料的能力及其在暴雨过程模拟中的效能。对2008年6月6—7日广东地区一次大暴雨过程进行了同化及数值模拟试验,结果表明,同化ATOVS辐射率资料得到的分析场,丰富了对流层高层的大气温度和对流层中低层的大气湿度信息,对风场也有一定的改进。控制试验和同化试验都较好地模拟出了降水的主要落区和发生时段,但控制试验对暴雨、大暴雨的雨区和雨强的模拟效果欠佳;相比而言,同化试验对强降水中心的位置、范围的模拟均有更好的反映,模拟的暴雨强度也与实际降水量级基本一致,同化改进效果明显。     

A self-sufficient approach for GERB cloudy radiance detection

Geostationary Earth Radiation Budget (GERB) is the broadband radiometer onboard the Meteosat Second Generation (MSG) platform, launched at the end of August 2002 and still in commissioning phase. GERB data is planned to be used in many applications concerning Earth Radiation Budget (ERB) calculation. In order to evaluate the impact of clouds on ERB, a cloud detection is required and, at present, a cloud mask based on higher spatial and spectral resolution data acquired by Spinning Enhanced Visible and Infrared Imager (SEVIRI), the imager onboard the same MSG platform, is planned to be used in order to identify cloudy GERB soundings.As an alternative, a self-sufficient (only based on GERB data) method (OCA, the One-channel Cloudy-radiance-detection Approach) is proposed, as a time-saving and, probably, more suitable solution than the planned co-location approach.In this paper, preliminary results obtained by using several years of Meteosat data as well as GERB synthetic radiances (produced from Meteosat-7 observations) are presented. It is shown how results obtained by using GERB data alone can be comparable (and better in terms of number and spatial distribution of clear-sky GERB soundings identified) to the ones achieved if the co-location of a higher resolution cloud mask is used.     

全球变暖背景下高山林线交错带的动态综述（英文）

高山林线交错带是亚高山森林与苔原之间、亚高山森林与无树草原之间的过渡带状区域,是生物多样性热点区域,具有营养物质输入源和低海拔生态系统的碳固存等不可替代的生态功能,提供着各种生态系统服务。与高山林线交错带相关的三种树线是树种线、林线和木材线。由于高山林线交错带占据了树种耐受温度极限的极端区域,对气候变化非常敏感,经常被用作植被对全球变暖响应的指标。随着全球气候变暖的加剧和不同气候区海拔梯度的变化,高山林线交错带中的树高和生物量也会发生显著变化。同时分布在全球不同气候带上的林线变化也表现出不同的规律,其中的原因包括温度升高程度的不一致、优势种和植物群落的不同、人为干扰程度的不同等。另外,关于林线推进的驱动因素也无一致的研究结果,不同气候区之间的研究结果可能会相互矛盾。然而,目前在气候变化下的高山林线发展领域,缺乏全面的综述。因此,本文从以下四个方面对此前的研究进行了总结,并探讨了高山林线动态变化的理论基础和挑战：（1）高山林线动态变化的生态功能和生态问题;（2）监测高山林线动态变化的研究方法;（3）全球不同气候区的林线迁移;（4）林线向上迁移的驱动因素。     

2007年6—7月西太平洋副热带高压的异常特征及其成因分析

采用NCEP资料以及NOAA卫星观测的OLR场资料,分析了2007年6—7月淮河流域暴雨及江南、华南异常高温期间西太平洋副热带高压的异常特征,其表现为强度强且南北位置相对稳定,东西方向进退明显于南北方向的移动。通过分析经圈平面上的垂直环流及风矢量场的特征表明,副高南北两侧都存在一定强度的上升气流,北侧上升气流对西太平洋副高中心区700 hPa以上高度的下沉运动有激发作用,而南侧上升气流对西太平洋副高中心区的下沉运动作用不大。中高纬度阻塞高压双阻型的建立,有利于西太平洋副高的加强和发展。强劲而稳定少动的中纬度西风急流和热带地区异常活跃的对流均有利于西太平洋副高的相对稳定。     

Application of direct assimilation of ATOVS microwave radiances to typhoon track prediction

In order to solve the difficult problem of typhoon track prediction due to the sparsity of conventionaldata over the tropical ocean, in this paper, the No. 0205 typhoon Rammasun of 4-6 July 2002 is studiedand an experiment of the typhoon track prediction is made with the direct use of the Advanced TIROS-NOperational Vertical Sounder (ATOVS) microwave radiance data in three-dimensional variational dataassimilation. The prediction result shows that the experiment with the ATOVS microwave radiance datacan not only successfully predict the observed fact that typhoon Rammasun moves northward and turnsright, but can also simulate the action of the fast movement of the typhoon, which cannot be simulated withonly conventional radiosonde data. The skill of the typhoon track prediction with the ATOVS microwaveradiance data is much better than that without the ATOVS data. The typhoon track prediction of theformer scheme is consistent in time and in location with the observation. The direct assimilation of ATOVSmicrowave radiance data is an available way to solve the problem of the sparse observation data over thetropical ocean, and has great potential in being applied to typhoon track prediction.     

水下盾构隧道纵向上浮理论解及工程应用

考虑静动态上浮力、浆液时变性和上覆土体反向压缩性因素,基于弹性地基梁的弯曲微分方程、有限元理论和变形、转角、剪力以及弯矩协调方程和边界条件,获得了水下盾构隧道纵向上浮的理论解,并运用于“河北第一盾”曹妃甸工业区综合管廊工程。工程算例表明,理论解与数值解最大误差在2.5%以内,与正常掘进段监测值吻合度较高,可用于分析水下盾构隧道纵向上浮。另外,所得理论解摒弃了数值计算模型建立和细化单元的繁琐过程,易被设计、施工人员接受和应用,同时也为完善相关设计规范提供一定参考。