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一、方法和被发现的性质 在以前的两次“东京会议”之前,在数值天气预报模式中对空间离散化的唯一可行方法是有限差分法。由于转换技术的发明,现在情况大大地改观了,许多全球模式(尤其是中期)如今都使用谱方法。在许多情况下(如日本气象厅,欧洲中期天气予报中心)甚至有限区域模式(短期)已经或者正在发展谱方法(Tatsumi,1985;世界气象组织,1985)。 谱方法在减少相速误差和处理极地问题的优越性是众所周知的。在中期预报上给人印象最深的进步就是使用了谱模式,特别是欧洲中期天气预报模式(Bengtsson,1985)。然而经常出现的问题是——如果它是一个问题的话——是用虚假负地形来描写陡峭的山脉,而这种虚假负地形的局地影响已被认为“在某些情况下是不理想的”(Jarraud and Baeele,1985)。也许人们能在这里增加一些灵活性,以致使某些模式的结果更近似。目前这种灵活性在格点模式中已经引入或正在得到普及,但在谱模式中显然还是不能应用。
Methods and Discovered Properties Prior to the two previous Tokyo Conferences, the only possible way to discretize space in the numerical weather forecasting model was the finite difference method. Due to the invention of conversion technology, the situation has greatly improved, and many global models (especially in the medium term) now use spectral methods. In many cases (such as the Japan Meteorological Agency and the European Center for Medium-Range Weather Reporting) even the limited regional model (short term) has been or is being developed for spectral methods (Tatsumi 1985; World Meteorological Organization 1985). The benefits of spectral methods in reducing phase velocity errors and handling polar issues are well known. The most impressive advance in mid-term forecasting is the use of spectral models, especially in the medium-term European weather forecasting model (Bengtsson, 1985). However, the recurring problem is - if it is a problem - the use of false negative terrain to describe steep mountains, and the local influence of this false negative terrain has been considered "in some cases not desirable (Jarraud and Baeele, 1985). Maybe people can add some flexibility here, so that the results of some models are more similar. At present, this flexibility has been introduced or is gaining popularity in gridding mode, but apparently still can not be applied in spectrum mode.