Advances in simulating atmospheric variability with the ECMWF model:: From synoptic to decadal time-scales
Advances in simulating atmospheric variability with the ECMWF model:: From synoptic to decadal time-scales
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DOI：
10.1002/qj.289
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发表时间：
2008-07-01
影响因子：
8.9
通讯作者：
Balsamo, Gianpaolo
中科院分区：
文献类型：
--
作者：
Bechtold, Peter;Koehler, Martin;Balsamo, Gianpaolo
介绍了利用 ECMWF 模型模拟大气变化的进展，这些进展源于对对流和扩散参数化的修改。修订特别涉及引入可变对流调整时间尺度、与环境相对湿度成正比的对流夹带率，以及基于莫宁-奥布霍夫函数依赖性的热量和动量的自由对流层扩散系数。根据使用高分辨率中期确定性和集合预报、月度和季节积分的分析和观测来评估预报系统， 以及与大气-海洋耦合模型的十年整合。结果表明，在热带和温带中尺度、天气和行星扰动的幅度方面，模型活动的水平明显更高、更真实。重要的是，随着变异性的提高和偏差的减少，不仅概率分数得到提高，而且中纬度中短范围内的确定性分数也得到提高。此外，该模型首次能够代表对流耦合的赤道开尔文波和罗斯贝波的真实频谱，并在月度预测期间保持马登-朱利安振荡（MJO）的真实振幅。然而，MJO 的传播速度比观察到的要慢。较高的热带对流层波活动还通过动量沉积产生更好的平流层温度和风。对流降水和解析降水之间的划分不受模型变化的影响，全球降水总量的大约 62% 属于对流类型。最后，对流和扩散参数化的变化导致集合预报的扩展更大，这使得集合预报系统中初始扰动的幅度降低了30%。版权所有 (c) 2008 英国皇家气象学会。
Advances in simulating atmospheric variability with the ECMWF model are presented that stem from revisions of the convection and diffusion parametrizations. The revisions concern in particular the introduction of a variable convective adjustment time-scale, a convective entrainment rate proportional to the environmental relative humidity, as well as free tropospheric diffusion coefficients for heat and momentum based on Monin-Obukhov functional dependencies.The forecasting system is evaluated against analyses and observations using high-resolution medium-range deterministic and ensemble forecasts, monthly and seasonal integrations, and decadal integrations with coupled atmosphere-ocean models. The results show a significantly higher and more realistic level of model activity in terms of the amplitude of tropical and extratropical mesoscale, synoptic and planetary perturbations. Importantly, with the higher variability and reduced bias not only the probabilistic scores are improved, but also the midlatitude deterministic scores in the short and medium ranges. Furthermore, for the first time the model is able to represent a realistic spectrum of convectively coupled equatorial Kelvin and Rossby waves, and maintains a realistic amplitude of the Madden-Julian oscillation (MJO) during monthly forecasts. However, the propagation speed of the MJO is slower than observed. The higher tropical tropospheric wave activity also results in better stratospheric temperatures and winds through the deposition of momentum.The partitioning between convective and resolved precipitation is unaffected by the model changes with roughly 62% of the total global precipitation being of the convective type. Finally, the changes in convection and diffusion parametrizations resulted in a larger spread of the ensemble forecasts, which allowed the amplitude of the initial perturbations in the ensemble prediction system to decrease by 30%. Copyright (c) 2008 Royal Meteorological Society.