Tropical and Midlatitude Impact on Seasonal Polar Predictability in the Community Earth System Model
Tropical and Midlatitude Impact on Seasonal Polar Predictability in the Community Earth System Model
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DOI：
10.1175/jcli-d-19-0088.1
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发表时间：
2019-08
影响因子：
4.9
通讯作者：
E. Blanchard‐Wrigglesworth;Q. Ding
中科院分区：
文献类型：
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作者：
E. Blanchard‐Wrigglesworth;Q. Ding
利用完美模式试验和在GCM中应用助推方法，探讨了改进的热带和中纬度预报对季节性极地可预测性的影响。我们运行了三组长达7个月的预测：一组是标准的自由运行预测，另两组是推动的预测，其中大气风、温度和特定湿度（U、V、T、Q）被推动到自由集合的其中一组预测中。这两种推力预报将推力应用于不同的区域：热带地区（30°S-30°N）和热带和中纬度地区（55°S-55°N）。研究发现，热带地区对北极或南极地区的海冰和大气（主要局限于北太平洋和别灵斯高森-阿蒙森-罗斯海）的预报能力影响不大，而中纬度地区对北极冬季和南极全年的预报能力有较大的影响。相对于自由预报，从5月初始化开始的北极夏季预报技能在推力预报中并没有得到很大的提高，因此主要是一个“局部”问题。在大气中，中纬度推力对预报技术的改善在极地平流层中最大，而在向地表方向减弱。
The impact on seasonal polar predictability from improved tropical and midlatitude forecasts is explored using a perfect-model experiment and applying a nudging approach in a GCM. We run three sets of 7-month long forecasts: a standard free-running forecast and two nudged forecasts in which atmospheric winds, temperature, and specific humidity (U, V, T, Q) are nudged toward one of the forecast runs from the free ensemble. The two nudged forecasts apply the nudging over different domains: the tropics (30°S–30°N) and the tropics and midlatitudes (55°S–55°N). We find that the tropics have modest impact on forecast skill in the Arctic or Antarctica both for sea ice and the atmosphere that is mainly confined to the North Pacific and Bellingshausen–Amundsen–Ross Seas, whereas the midlatitudes greatly improve Arctic winter and Antarctic year-round forecast skill. Arctic summer forecast skill from May initialization is not strongly improved in the nudged forecasts relative to the free forecast and is thus mostly a “local” problem. In the atmosphere, forecast skill improvement from midlatitude nudging tends to be largest in the polar stratospheres and decreases toward the surface.