Predictability Changes of Stratospheric Circulations in Northern Hemisphere Winter
Predictability Changes of Stratospheric Circulations in Northern Hemisphere Winter
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DOI：
10.2151/jmsj.2016-001
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发表时间：
2016
影响因子：
3.1
通讯作者：
T. Ichimaru;S. Noguchi;T. Hirooka;H. Mukougawa
中科院分区：
文献类型：
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作者：
T. Ichimaru;S. Noguchi;T. Hirooka;H. Mukougawa
利用日本气象厅提供的1个月综合预报资料，研究了2001-2006年北方冬季平流层环流的实际可预测性。为了研究10 hpa位势高度场的可预测性极限，采用了均方根误差（RMSE）和异常相关（AC）两种测量方法。在冬季平流层，行星波活动的间歇性特征导致平流层环流出现两个特定时期，即行星波不活跃的未扰动期和行星波活跃的扰动期。因此，需要考虑到这一特性来评估可预测性。经过仔细考虑，扰动期的平均可预测周期约为10天；它比对流层的可预测周期（约7天）要长。但是，由于波浪场和纬向平均场的贡献所引起的预报误差的增长率不同，它表现出较大的变率。在非扰动期，基于AC的可预测周期与扰动期几乎相同，尽管基于RMSE的可预测周期非常长，因为RMSE可预测性是根据受扰动期影响的气候标准偏差来测量的。因此，即使预报误差很小，平流层环流的水平格局也难以预测。
Practical predictability of the stratospheric circulation in the boreal winters during the period 2001–2006 has been examined using the archive of 1-month ensemble forecast datasets provided by the Japan Meteorological Agency. To investigate the predictability limit, two measures of the Root-Mean-Square Error (RMSE) and Anomaly Correlation (AC) have been used for the 10-hPa geopotential height field. In the winter stratosphere, an intermittent character of planetary wave activity causes two specific periods of the stratospheric circulation, i.e., an undisturbed phase with inactive planetary waves and a disturbed phase with active ones. Therefore, the predictability needs to be evaluated taking account of this feature. On the basis of careful consideration, the mean predictable period can be estimated to about 10 days during the disturbed phase; it is longer than the tropospheric predictable period of about 7 days. However, it exhibits large variability because of different growth rates of forecast errors caused by contributions of both wave and zonal-mean fields. During the undisturbed phase, the predictable period based on the AC is almost the same as that of the disturbed phase, although the predictable period based on the RMSE is extremely long, since the RMSE predictability is measured against the climatological standard deviation affected by disturbed phases. Therefore, the horizontal pattern of the stratospheric circulation is less predictable even though the forecast error is quite small.