Numerical Simulation of Andhra Severe Cyclone (2003): Model Sensitivity to the Boundary Layer and Convection Parameterization

The Andhra severe cyclonic storm (2003) is simulated to study its evolution, structure, intensity and movement using the Penn State/NCAR non-hydrostatic mesoscale atmospheric model MM5. The model is used with three interactive nested domains at 81, 27 and 9 km resolutions covering the Bay of Bengal and adjoining Indian Peninsula. The performance of the Planetary Boundary Layer (PBL) and convective parameterization on the simulated features of the cyclone is studied by conducting sensitivity experiments. Results indicate that while the boundary layer processes play a significant role in determining both the intensity and movement, the convective processes especially control the movement of the model storm. The Mellor-Yamada scheme is found to yield the most intensive cyclone. While the combination of Mellor-Yamada (MY) PBL and Kain-Fritsch 2 (KF2) convection schemes gives the most intensive storm, the MRF PBL with KF2 convection scheme produces the best simulation in terms of intensity and track. Results of the simulation with the combination of MRF scheme for PBL and KF2 for convection show the evolution and major features of a mature tropical storm. The model has very nearly simulated the intensity of the storm though slightly overpredicted. Simulated core vertical temperature structure, winds at different heights, vertical winds in and around the core, vorticity and divergence fields at the lower and upper levels—all support the characteristics of a mature storm. The model storm has moved towards the west of the observed track during the development phase although the location of the storm in the initial and final phases agreed with the observations. The simulated rainfall distribution associated with the storm agreed reasonably with observations.     

山东省飞机增雨天气系统云水资源转化特征分析

利用水汽辐合法和水汽凝结法，对山东省1997－1999年春秋季18个降水过程的水汽辐合率、凝结率及降水效率等表征云水资源及其转化的特征量进行计算。分析了南方气旋、西北冷锋等主要降水天气系统以上特征量的地域分布和差别。可为人工增雨作业区域选择和航线设计提供气候背景。     

热带气旋灾害指数的估算与应用方法

根据1949－1999年共50年资料，对影响我国的热带气旋所造成的灾情特点作了评估研究。采用数理统计方法，进行定理的计算，按登陆和外围影响两类主要方式建立灾情指数序列，并在此基础上，客观地划分了灾情等级，用来表示受灾的程度。还采用独立于本资料源的Suffir-Simpson热带气旋灾害指数评估方法和资料进行对比验证，最后提出了一套台风灾害预评估的技术方法。     

广州中尺度模式局地要素预报性能分析

该文简要介绍了华南中尺度模式的地表要素的预报诊断方案, 站点要素时间序列预报情况.用适合站点要素时间序列预报的检验方法, 检验并分析了各要素时间序列预报的性能.表明该中尺度模式的地表要素时间序列预报方案是有效的, 预报具有较高的准确性和应用价值.     

The generation of phytoplankton patchiness by mesoscale current patterns

 Elken et al. (1994) suggested that phytoplankton patchiness can be generated by mesoscale eddies in light-limited, nutrient-replete environments. This hypothesis is explored using two ecological models of different physical complexity. The model results support the idea that the coupling of mesoscale eddy circulation and phytoplankton growth leads to differential growth rates and thus generates variability in phytoplankton distributions. The specific circulation of a cyclonic eddy isolates a phytoplankton population in its core. Due to the reduced vertical mixing, a higher growth rate is supported in the core, and phytoplankton concentrations increase compared to the surrounding environment. A one-dimensional model is used to explore the hypothesis in general and to perform sensitivity studies. A more realistic simulation uses a coupled three- dimensional model for the western Baltic Sea. Starting from vertically and horizontally homogeneous distributions for nutrients and plankton, the models generate patchiness due to the proposed mechanism. The described mechanism may apply for other mesoscale variable environments during light-limited growth periods as well, e.g., the frontal region of the Southern Ocean. Received: 31 March 2001 / Accepted: 31 August 2001     

热带气旋暴雨增幅造成北方特大暴雨的预报

利用人工神经元网络的非线性决策特性，采用前向多层的误差反向传输网络，研制了一个登陆北上热带气旋暴雨增幅造成北方特大暴雨的预报方法－－能自动判虽有无暴雨增幅及其出现地区的人工神经元分类预报网络。该方法简便客观，试用效果较好，即可投入业务使用。     

有限区域卫星云图资料变分分析的试验研究

资料分析在数值预报中的重要性受到越来越多的关注，星目前常规探测网的时空局限性，利用分辨率较高的非常规资料势在必行。该文利用一个有限区域中尺度模式ＭＭ４，采用变分分析技术对有限区域的常规探空资料和非常规云图资料进行变分分析和数值模拟。     

A STUDY ON THE VARIATIONS OF ANNUAL FREQUENCY FOR TROPICAL CYCLONE IN NORTHWEST PACIFIC DURING THE LAST HUNDRED YEARS

In this paper, a study on the variation of annual frequency of tropical cyclone (TC) and its relation with SST, Southern Oscillation index, sunspot relative number and number of days for specific circulation patterns was made by using 1884-1988 data of annual frequency for Northwest Pacific TC occurrence, which had been corrected to tendencies.Preliminary results indicated that in the variation of annual TC frequency there exist obvious p.6riods of 21, 31, 15 and 6 years and sustaining periods lasting 12 years in average.Well-defined processes of inflexion were observed in 1931, 1959 and 1977 over the past hundred years.The results also suggested insignificant statistic tendency of annual TC frequency increasing (decreasing) in winter/spring (summer/autumn )in the El Nino years.When the stratosphere was in the zonally westerly phase, the northern zonal circulation would abnormally develop and solar activity would enhance to favour the generation and development of TC.     

VENTILATION FLOW IN A BAROCLINIC VORTEX RELATED TO TROPICAL CYCLONE MOTION

The tropical cyclone motion is numerically simulated with a quasi-geostrophic baroclinic model.The flow field of a tropical cyclone is decomposed into its axisymmetric and asymmetric components.The relation between the ventilation flow vector and the motion vector of the tropical cyclone is inves-tigated.The results of numerical experiments indicate:(1) There are both large-scale beta gyres andsmall-scale gyres in the asyrnmetric flow field.(2) The interaction between small-scale gyres andlarge-scale beta gyres leads to the oscillation of translation speed and translation direction for the tropi-cal cyclone.(3) There are the large deviations between the ventilation flow vector calculated bymeans of Fiorino and Elsberry's method and the motion vector of tropical cyclone.(4) The ventila-tion flow vector computed using the improved method closely correlates with the motion vector of thetropical cyclone.     

东海近海热带气旋及天气数值预报系统

以ＭＭ４模式为框架,研制并建立了东海近海热带气旋及天气数值预报系统,将对热带气旋的预报和一般天气的预报统一在一个模式中,并实现了业务自动化控制,自１９９４年台风季节起投入了业务试验和准业务的运行。结果表明：该系统对东海近海热带气旋路径、风场、降水及江淮梅雨降水具有较好的预报能力