Reduced error and uncertainty in analysis and forecasting in the Southern Hemisphere through assimilation of PANSY radar observations from Syowa Station: a mid-latitude extreme cyclone case
Reduced error and uncertainty in analysis and forecasting in the Southern Hemisphere through assimilation of PANSY radar observations from Syowa Station: a mid-latitude extreme cyclone case
复制标题
通过同化昭和站 PANSY 雷达观测结果，减少南半球分析和预报的误差和不确定性：中纬度极端气旋案例
DOI：
10.1002/qj.4347
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发表时间：
2022
影响因子：
8.9
通讯作者：
and K. Sato
中科院分区：
文献类型：
--
作者：
K. Sato;J. Inoue;A. Yamazaki;Y. Tomikawa;and K. Sato
南半球高纬度地区观测网络分布稀疏，降低了区域大气环流分析和天气预报的精度。利用可操作的中期集合预报，我们比较了各预报中心对2017年12月17日靠近西澳大利亚的中纬度气旋的预报能力。在预报第4.5天，来自南极洲沿海的高空低压槽在西澳大利亚上空传播了一个大的集合，这对中纬度气旋的预报位置造成了很大的不确定性和误差。利用集合资料同化系统、地球模拟器大气环流模式和局地集合变换卡尔曼滤波实验集合再分析2 (ALERA2)，对日本南极Syowa站PANSY雷达1小时水平风速观测资料同化对ALERA2及其预报结果的影响进行了业务预报试验研究。观测系统试验表明，将PANSY雷达数据纳入对流层和平流层低层大气参数作为预报的初始条件，提高了大气参数的可重复性。为了研究PANSY雷达数据对中纬度气旋预报技能的影响，以有和没有PANSY数据的分析数据为初始条件，进行了63个成员集合预报试验。集合预报实验结果的对比证实，作为初始条件，PANSY雷达数据的加入减少了南极地区对流层上层集合的扩展和误差，从而提高了预报第4.5天西澳大利亚上空高层槽和地面气旋位置的预报精度。这些试验表明，PANSY雷达是一种适合于不断提高南半球大气环流预报技术的观测系统。
The sparse distribution of the observing network over the high latitudes of the Southern Hemisphere reduces the accuracy of regional atmospheric circulation (re)analysis and weather forecasting. Using operational medium‐range ensemble forecasts, we compared the forecast skill among forecast centres regarding a midlatitude cyclone close to western Australia on 17 December 2017. At forecast day 4.5, a large ensemble spread in an upper‐level trough over western Australia, which had travelled from coastal Antarctica, caused large uncertainty and error in the predicted position of the midlatitude cyclone. Using an ensemble data assimilation system and the Atmospheric General Circulation Model for the Earth Simulator and the Local Ensemble Transform Kalman Filter Experimental Ensemble Reanalysis version 2 (ALERA2), we conducted an operational forecast experiment to investigate the impact on ALERA2 and its forecast result of assimilation of 1‐hourly horizontal wind speed observational data from the PANSY radar located at the Japanese Syowa Station in Antarctica. An observing system experiment revealed that incorporation of PANSY radar data improved the reproducibility of atmospheric parameters in the troposphere and lower stratosphere as initial conditions for forecasting. To investigate the impact of PANSY radar data on forecast skill regarding the midlatitude cyclone, 63‐member ensemble forecast experiments were conducted using analysis data both with and without PANSY data as initial conditions. Comparison of the forecast results from the ensemble forecast experiments confirmed that incorporation of PANSY radar data reduced the ensemble spread and error in the upper troposphere over the Antarctic region as initial conditions, which enhanced the accuracy of the prediction of the positions of the upper‐level trough and surface cyclone over western Australia at forecast day 4.5. These experiments suggest that the PANSY radar represents an observing system suitable for continuous improvement in forecast skill of the atmospheric circulation in the Southern Hemisphere.