The predictive skill and the most predictable pattern in the tropical Atlantic: The effect of ENSO
The predictive skill and the most predictable pattern in the tropical Atlantic: The effect of ENSO
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DOI：
10.1175/mwr3393.1
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发表时间：
2007-05-01
影响因子：
3.2
通讯作者：
Huang, Bohua
中科院分区：
文献类型：
--
作者：
Hu, Zeng-Zhen;Huang, Bohua
本文研究了热带大西洋NCEP气候预报系统(CFS)的预报技巧和最可预报模式。通过预测与相应分析之间的海表面温度(SST)异常相关性来衡量这一技能，并通过具有最大信噪比的经验正交函数分析来分离出最可预测的模式。平均而言，对于所有月份的初始条件预报，SST的可预报性西部高于东部。最高技能出现在热带巴西海岸附近和加勒比海，最低技能出现在东部海岸。从季节上看，在夏季或秋季使用ICs进行预测的技能较高，而在春季使用ICs进行预测的技能较低。CFS对热带大西洋经向梯度的预测很差。CFS预报相对于持续性预报的优势取决于IC月、地区和提前期。当提前期大于3个月时，CFS预测总体上好于相应的持续性预测。3月份最可预测的海温模式在几乎整个热带大西洋都有相同的迹象。3月份热带北大西洋西北部和热带南美洲至热带北大西洋西南部地区之间的降水变化明显相反，而在该区域的大部分地区，200百帕高度的位势高度都是相同的符号。这些可预测的信号主要是受厄尔尼诺-南方涛动(ENSO)的影响。3月份从热带南美洲到热带北大西洋西南部地区最可预测的降水模式的显著值与中心内这些地区的低(高)层过度辐散(辐合)有关。对于CFS来说，热带大西洋的预测能力在很大程度上取决于它预测ENSO的能力。这是由于ENSO与模式中热带大西洋最可预测的模式之间的密切联系。热带北大西洋海温的较高预报能力与中心在季节间时间尺度上预报ENSO的能力是一致的，特别是对于3-10月暖月的ICS。在东南大洋，系统的暖偏倚是导致该地区技术含量低的一个重要因素。
This work investigates the predictive skill and most predictable pattern in the NCEP Climate Forecast System (CFS) in the tropical Atlantic Ocean. The skill is measured by the sea surface temperature (SST) anomaly correlation between the predictions and the corresponding analyses, and the most predictable patterns are isolated by an empirical orthogonal function analysis with a maximized signal-to-noise ratio. On average, for predictions with initial conditions (ICs) of all months, the predictability of SST is higher in the west than in the east. The highest skill is near the tropical Brazilian coast and in the Caribbean Sea, and the lowest skill occurs in the eastern coast. Seasonally, the skill is higher for predictions with ICs in summer or autumn and lower for those with ICs in spring. The CFS poorly predicts the meridional gradient in the tropical Atlantic Ocean. The superiority of the CFS predictions to the persistence forecasts depends on IC month, region, and lead time. The CFS prediction is generally better than the corresponding persistence forecast when the lead time is longer than 3 months. The most predictable pattern of SST in March has the same sign in almost the whole tropical Atlantic. The corresponding pattern in March is dominated by the same sign for geopotential height at 200 hPa in most of the domain and by significant opposite variation for precipitation between the northwestern tropical North Atlantic and the regions from tropical South America to the southwestern tropical North Atlantic. These predictable signals mainly result from the influence of the El Nino-Southern Oscillation (ENSO). The significant values in the most predictable pattern of precipitation in the regions from tropical South America to the southwestern tropical North Atlantic in March are associated with excessive divergence (convergence) at low (high) levels over these regions in the CFS. For the CFS, the predictive skill in the tropical Atlantic Ocean is largely determined by its ability to predict ENSO. This is due to the strong connection between ENSO and the most predictable patterns in the tropical Atlantic Ocean in the model. The higher predictive skill of tropical North Atlantic SST is consistent with the ability of the CFS to predict ENSO on interseasonal time scales, particularly for the ICs in warm months from March to October. In the southeastern ocean, the systematic warm bias is a crucial factor leading to the low skill in this region.