Forecasting extreme events in the tropical Indian Ocean sector climate

Prospects for forecasting climate variability over the tropical Indian Ocean sector, specifically extreme positive events of the Indian Dipole Mode (IDM), with lead times of a season or more are investigated using the NASA Seasonal-to-Interannual Prediction Project (NSIPP) coupled-model system. The coupled system presents biases in its climatology over the Indian Ocean sector, which include (i) warmest sea-surface temperatures (SSTs) occurring in the central equatorial basin rather than on the eastside with the eastern (western) tropical SSTs up to 1 °C too cool (warm), (ii) a too northwest lying InterTropical Convergence Zonal over the ocean in boreal fall, (iii) a thermocline shallower (deeper) than observed west of Sumatra-Java (north of Madagascar), (iv) a delay of about a month in the onset (cessation) of the southwest (southeast) monsoon in the west (east) in boreal spring (fall). These biases affect the effectiveness of the SST-clouds-shortwave radiation negative feedback, the sensitivity of SST to wind-stress perturbations, and the character of equatorial coupled ocean-atmosphere modes. Despite these biases, ensemble hindcasts of the SST anomalies averaged over the eastern and western poles of the IDM for the decade 1993–2002, which included extreme positive events in 1994 and 1997/1998, are encouragingly good at 3-months lead. The onset of the 1997/1998-event is delayed by about a month, though the peak and decay are correctly timed. At 6-months lead-time, the forecast at the eastern pole deteriorates with either positive or negative false alarms generated each boreal fall. The forecast at the western pole remains good.     

Limitations of real-time models for forecasting river flooding from monsoon rainfall

Very intense rainfall during the southwest and northeast monsoons causes severe river flooding in India. Some traditional techniques used for real-time forecasting of flooding involve the relationship between effective rainfall and direct surface runoff, which simplifies the complex interactions between rainfall and runoff processes. There are, however, serious problems in deducing these variables in real time, so it is highly desirable to have a real-time flood forecasting model that would directly relate the observed discharge hydrograph to the observed rainfall. The storage routing model described by Baba and Hoshi (1997), Tanaka et al. (1997), and Baba et al. (2000), and a simplified version of this model, have been used to compute observed river discharge directly from observed hourly rainfall. This method has been used to study rainfall–runoff data of the Ajay River Basin in eastern India. Five intense rainfall events of this basin were studied. Our results showed that the Nash–Sutcliffe efficiency of discharge prediction for these five events was 98.6%, 94.3%, 86.9%, 85.6%, and 67%. The hindcast for the first two events is regarded as completely satisfactory whereas for the next two events it is deemed reasonable and for the fifth it is unsatisfactory. It seems the models will yield accurate hindcast if the rainfall is uniform over the drainage basin. When the rainfall is not uniform the performance of the model is unsatisfactory. In future this problem can, in principle, be corrected by using a weighted amount if rainfall is based upon multiple rain-gauge observations over the drainage basin. This would provide some measure of the dispersion in the rainfall. The model also seems unable to simulate flooding events with multiple peaks.     

回溯时间积分格式的有效性研究

采月正压准地转模式作为动力核,用Rossby-Haurwitz波函数作为理想场,同时使用回溯时间积分格式和普通中央差格式进行数值试验.结果表明,在短时积分的情况下,回溯格式能减小数值解误差1～2个量级,而且它对时间步长的增大不敏感.因此使用回溯格式可以减少积分计算量,延长积分时效.     

铁路沿线灾害性天气监测、预测、预警系统

针对铁路三防（防风，防沙，防洪）的需要，结合大风监测系统建设的实际，对恶劣天气气候条件下，如何保障列车运行安全进行了探讨，并提出铁路沿线灾害性天气监测，预测，预警系统。     

Comparative study of electron density from incoherent scatter measurements at Arecibo with the IRI-95 model during solar maximum

Arecibo (18.4 N, 66.7 W) incoherent scatter (IS) observations of electron density N(h) are compared with the International Reference Ionosphere (IRI-95) during midday (10/14 h), for summer, winter and equinox, at solar maximum (1981). The N(h) profiles below the F2 peak, are normalized to the peak density NmF2 of the F region and are then compared with the IRI-95 model using both the standard B0 (old option) and the Gulyaeva-B0 thickness (new option). The thickness parameter B0 is obtained from the observed electron density profiles and compared with those obtained from the IRI-95 using both the options. Our studies indicate that during summer and equinox, in general, the values of electron densities at all the heights given by the IRI model (new option), are generally larger than those obtained from IS measurements. However, during winter, the agreement between the IRI and the observed values is reasonably good in the bottom part of the F2 layer but IRI underestimates electron density at F1 layer heights. The IRI profiles obtained with the old option gives much better results than those generated with the new option. Compared to the observations, the IRI profiles are found to be much thicker using Gulyaeva-B0 option than using standard B0.     

Seasonal Forecasting for Climate Hazards: Prospects and Responses

One of the most promising developments for early warning of climate hazards is seasonal climate forecasting. Already forecasts are operational in many parts of the tropics and sub-tropics, particularly for droughts and floods associated with ENSO events. Prospects for further development of seasonal forecasting for a range of climatichazards are reviewed, illustrated with case studies in Africa, Australia, the U.S.A. and Europe. A critical evaluation of the utility of seasonal forecasts centres on vulnerability, communicationchannels, and effective responses. In contrast to short-term prediction, seasonal forecasts raise new issues of preparedness and the use of information.     

铜陵市区的烟幕分析及其预测

作者应用气象资料分析烟幕的发生规律，并应用灰色理论对烟幕进行预测。     

海安暴雨洪涝灾害预报探讨

暴雨洪涝预报是目前气象和水利，水文学科正在致力攻克的预报难题。作者通过调查海安洪涝发生与暴雨的关系，利用水文，地形资料找出径流量和主河道水位升降的相关，结合暴雨预报，推导暴雨洪涝发生的可能以及大致区域和洪涝程度。     

中国及邻近地区冬到夏的季节变化

南亚地区在冬到夏的转变过程中有显著的热力学与环境变化特征，是北半球季节变化的敏感区，对我国长期变化有十分重要的意义。根据这一特点，设计计算了南支西风指数，并将副高面积指数分南北区统计，更地地反映了季节变化特征。统计结果表明，这个指数组对梅雨与华北雨季有天气气候学意义。同时还找到了这个指数组对我国一些地区旱涝的前期指标。     

一种夏季大范围降水趋势分布的预报方法

综合考虑了影响夏季降水异常的大气、海洋因子和降水变化规律，提出了一种大范围降水异常分布的统计预报方法。用１９９１－１９９４年的独立资料检验，取得了满意效果。