Forecast evaluation of the North Pacific jet stream using AR Recon dropwindsondes,Quarterly Journal of the Royal Meteorological Society

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Forecast evaluation of the North Pacific jet stream using AR Recon dropwindsondes
Quarterly Journal of the Royal Meteorological Society ( IF 3.0 ) Pub Date : 2023-07-26 , DOI: 10.1002/qj.4545
David A. Lavers _{1,

2} , Ryan D. Torn ₃ , Chris Davis ₄ , David S. Richardson ₁ , F. Martin Ralph ₅ , Florian Pappenberger ₁

Affiliation

The term jet stream generally refers to a narrow region of intense winds near the top of the midlatitude or subtropical troposphere. It is in the midlatitude jet stream where instabilities and waves may develop into synoptic-scale systems, which in turn makes accurately resolving the structure of the jet stream and associated features critical for atmospheric development, predictability, and impacts, such as extreme precipitation and winds. Using dropwindsonde observations collected during the Atmospheric River Reconnaissance (AR Recon) campaign from 2020 to 2022, this study assesses the North Pacific jet stream structure in the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS). Results show that the IFS has a slow-wind bias on the lead times assessed, with the strongest winds (≥50 m·s⁻¹) having a bias of up to −1.88 m·s⁻¹ on forecast day 4. Also, the IFS cannot resolve the sharp potential vorticity (PV) gradient across the jet stream and tropopause, and this PV gradient weakens with forecast lead time. Cases with larger wind biases are characterized by higher PV biases and PV biases tend to be larger for cases with a higher horizontal PV gradient. These results suggest that further model-based experiments are needed to identify and address these biases, which could ultimately yield increased forecast accuracy.

中文翻译：

使用 AR Recon 落风探空仪对北太平洋急流进行预测评估

急流一词通常指中纬度或副热带对流层顶部附近的狭窄强风区域。在中纬度急流中，不稳定性和波浪可能会发展成天气尺度的系统，这反过来又使得准确解析急流的结构和相关特征对于大气发展、可预测性和影响（例如极端降水和风）至关重要。本研究利用 2020 年至 2022 年大气河勘测 (AR Recon) 活动期间收集的落风探空仪观测数据，评估了欧洲中期天气预报中心 (ECMWF) 综合预报系统 (IFS) 中的北太平洋急流结构。结果显示，IFS 在评估的提前时间上存在慢风偏差，其中最强风 (≥50 m·s ^-1 )在预测第 4 天的偏差高达 -1.88 m·s ^-1 。此外， IFS 无法解析急流和对流层顶的急剧位涡 (PV) 梯度，并且该 PV 梯度会随着预测的提前时间而减弱。风力偏差较大的情况的特点是光伏偏差较高，而水平光伏梯度较高的情况下，光伏偏差往往较大。这些结果表明，需要进一步基于模型的实验来识别和解决这些偏差，这最终可能会提高预测的准确性。

更新日期：2023-07-26

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