AN IMPACT STUDY OF A NEW TYPE OF DATA OF ADAPTIVE OR TARGETING OBSERVATION ON TYPHOON FORECAST

There was a new concept of ‘adaptive or targeting observation’ in recent years, which is an additional and targeting observation based on the existing and fixed observing network for the atmosphere on the impacted region. Dropsonde is one of the important observing instruments in the adaptive or targeting observation. In this paper, GRAPES, the next generation of numerical weather prediction system of China has been used. The impacts on the typhoon Dujuan (No.200315) forecast in experiments with dropsonde have been studied and experiments on sensitivity have also been done. It was found that the forecasts of the elements have been improved obviously with the use of dropsonde, such as the path, the center location, and the intensity of typhoon. It was also found in the sensitivity studies that the setting of deviation structure also has obvious impacts on the forecast for typhoons. It is not true that the simulation is better when the proportion of the data of dropsonde is larger in the course to modify the background.     

变网格一体化模式的研究进展

作者介绍了近年来在数值天气预报领域的一个新动向－变网格一体化模式的进展。这种模式可以替代目前业务数值天气预报的有限区模式和全球谱模式，降低业务数值天气预报的计算成本。网格距离的可变性，以及采用半隐式－半拉格朗日式时间差分方案是该模式的主要特点。法国的变网格一体化模式自１９９２年已投入业务使用，其可行性已得到了预报检验的初步证实。     

TYPHOON TRACK PREDICTION EXPERIMENTS USING T106L19

1 INTRODUCTION The tropical cyclone is one of destructive weather systems that affect China most seriously. The destruction includes strong winds, heavy rain and storm surges. The key to mitigate them is whether we could predict the track accurately and on a timely basis. A number of coastal countries have adopted numerical forecast operation models that have long valid duration. For instance, in the limited-area spectral models and global spectral models currently running in the Meteo…     

GRAPES_RAFS系统研发

基于GRAPES (Global and Regional Assimilation and Prediction System)模式的GRAPES_RAFS (Rapid Analysis and Forecast System)系统是一个向前的间歇性同化分析的分析系统,能将多种高时空分辨率的观测资料充分利用起来,同时也是一个不断更新数值预报产品的中尺度数值预报系统.本文从该系统的结构、流程所涉及的各技术环节进行阐述,通过与业务GRAPES_MESO的预报效果对比分析对该系统的短时临近预报能力以及影响该系统短临预报性能的关键技术进行研究.研究结果表明:利用我国新一代数值预报系统GRAPES模式及GRAPES_3Dvar建立的全国稠密资料快速更新同化分析预报系统(GRAPES_RAFS系统)具有一定短时临近预报能力.同化系统的背景误差协方差准确描述、模式系统动力框架及物理过程精确度的提高能有效提高该系统的预报能力,而局地稠密资料的合理使用是该系统提供高质量预报的另一个关键技术,在资料相对稀少的情况下,该系统的短临预报性能面临严重挑战.     

不同平缓-混合坐标对一次高原准静止锋降水过程模拟影响对比分析

GRAPES_Meso模式预报存在南风偏大、虚假降水偏多等问题,且在大地形下游地区异常明显。平缓-混合坐标可以有效减小气压梯度力计算误差以及平流输送误差,而这两种误差与风场和水汽场预报密切相关。基于GRAPES_Meso模式选择四种平缓-混合坐标对一次典型的高原东部准静止锋降水过程进行模拟分析。模拟结果表明,较弱的天气形势演变下,平缓-混合坐标的改进效果比较明显,可以有效缓解风场预报偏差、虚假降水、虚假天气系统等问题,个例模拟的结果与实况更接近。     

非均匀分层下的二阶精度垂直差分方案及其在GRAPES模式中的应用

在非均匀分层下,目前GRAPES（Global/Regional Assimilation and Prediction System）模式中使用的垂直差分方案只能达到一阶精度。本文设计了一种适用于非均匀分层的二阶精度垂直差分方案,并将它应用于改进GRAPES模式动力框架的垂直离散化过程。一维廓线理想试验结果表明:二阶精度方案可以减少差分计算误差,而这种改进的幅度相对于差分计算本身引起的误差来说仍然是比较小的。通过密度流试验对修改后的模式动力框架进行测试,结果表明二阶方案可以保持模式动力框架的准确性和稳定性。进一步利用实际资料开展批量测试,发现二阶方案可以降低模式高空要素场的预报误差,而且这种改进随着预报时间的延长变得更为明显。最后选择一次典型的华南暴雨过程进行模拟,同样发现二阶精度方案对于48小时之后的降水会有一定程度的改进。     

不同光照周期对铜绿微囊藻和绿色微囊藻生长的影响

研究了不同光照周期对铜绿微囊藻(Microcystisaeruginosa)和绿色微囊藻(Microcystisviridis)生长的影响.按光照周期不同将两种微囊藻各分为五组处理组I[2L/22D]、Ⅱ[5L/19D]、Ⅲ[7L/17D]、Ⅳ[9L/15D]、对照组[12L/12D],试验期为20d.试验表明铜绿微囊藻实验中处理组Ⅳ[9L/15D]的比增长率和最大细胞数均最大,超过了对照组[12L/12D].绿色微囊藻实验中对照组[12L/12D]的最大细胞数和比增长率最大.随光照周期的延长两种微囊藻的最大细胞数有增加的趋势.绿色微囊藻对光照周期较铜绿微囊藻敏感.两种微囊藻在每日2h的光照周期下生长均受到抑制.     

适应性观测研究现状和展望

适应性观测是指为了有针对性地提高高影响天气数值预报的质量,在已有观测系统基础上对特定敏感区域/特定时段进行补充性加强观测。十多年来,这种旨在提高数值预报质量的新策略在国际上引起高度重视,成功开展了多个系列外场观测试验,并在适应性观测敏感区识别方法的发展和适应性观测资料同化后对数值预报质量影响的定量评估等方面均取得了重要的研究成果。文中简述了适应性观测问题及其目的,着重分析和总结了目标敏感区识别方法及其特点和适应性观测对数值预报质量的影响等方面的研究进展,并讨论了适应性观测资料改进未来数值预报质量需要解决的关键科学问题。     

Effects of terrain-following vertical coordinates on high-resolution NWP simulations

With increasing resolution in numerical weather prediction(NWP)models,the model topography can be described with finer resolution and includes steeper slopes.Consequently,negative effects of the traditional terrain-following vertical coordinate on high-resolution numerical simulations become more distinct due to larger errors in the pressure gradient force(PGF)calculation and associated distortions of the gravity wave along the coordinate surface.A series of numerical experiments have been conducted in this study,including idealized test cases of gravity wave simulation over a complex mountain,error analysis of the PGP estimation over a real topography,and a suite of real-data test cases.The GRAPES-Meso model is utilized with four different coordinates,i.e.,the traditional terrain-following vertical coordinate proposed by Gal-Chen and Somerville(hereinafter referred to as the Gal.C.S coordinate),the one-scale smoothed level(SLEVE1),the two-scale smoothed level(SLEVE2),and the COSINE(COS)coordinates.The results of the gravity wave simulation indicate that the GRAPES-Meso model generally can reproduce the mountain-induced gravity waves,which are consistent with the analytic solution.However,the shapes,vertical structures,and intensities of the waves are better simulated with the SLEVE2 coordinate than with the other three coordinates.The model with the COS coordinate also performs well,except at lower levels where it is not as effective as the SLEVE2 coordinate in suppressing the PGF errors.In contrast,the gravity waves simulated in both the Gal.C.S and SLEVE1 coordinates are relatively distorted.The estimated PGF errors in a rest atmosphere over the real complex topography are much smaller(even disappear at the middle and upper levels)in the GRAPES-Meso model using the SLEVE2 and COS coordinates than those using the Gal.C.S and SLEVE1 coordinates.The results of the real-data test cases conducted over a one-month period suggest that the three modified vertical coordinates(SLEVE1,SLEVE2,and COS coordinates)give better results than the traditional Gal.C.S coordinate in terms of forecasting bias and root mean square error,and forecasting anomaly correlation coefficients.In conclusion,the SLEVE2 coordinate is proved to be the best option for the GRAPES-Meso model.