Abstract

A variational bias correction (VarBC) technique is proposed within the three-dimensional variational (3D-Var) assimilation system of the Météo-France convective scale model AROME to remove biases present in horizontal wind components derived from aircraft Mode-S data. A set of two predictors derived from the geometry between ground and air speeds has been chosen in order to correct the aircraft speed and heading. Data collected from a set of 8 ADS-B antennas located over France for two periods in 2018 (April and October) have been used to assess the VarBC. Thanks to the availability of anchoring data (radiosoundings, AMDAR aircraft reports), the adaptive bias correction scheme is very efficient for improving the quality of Mode-S derived winds to a level that is similar to those from AMDAR and Mode-S bias corrected by the KNMI. The heading bias correction is the most important one in order to reach background departure values around 2.5 m/s. The behaviour of the VarBC is assessed more precisely for specific aircraft where its capacity to adapt to rapid changes due for example to aircraft maintenance is demonstrated. Moreover, when examining separately predictors for both wind components they appear to converge most of the time towards similar speed and heading corrections. Additional quality controls have allowed to reach background departure values of 2.2 m/s while increasing by a factor of ten the number of aircraft observations to be assimilated in the AROME-France domain.

摘要

在法国-法国对流尺度模型AROME的三维变分（3D-Var）同化系统中，提出了变分偏差校正（VarBC）技术，以消除从飞机S模式数据得出的水平风分量中存在的偏差。为了校正飞机的速度和航向，已经选择了一组从地面速度和空气速度之间的几何形状导出的两个预测变量。从2018年两个月（4月和10月）在法国境内的8个ADS-B天线中收集的数据已用于评估VarBC。由于有了锚定数据（无线电探测，AMDAR飞机报告），自适应偏差校正方案非常有效地将Mode-S派生风的质量提高到与AMDAR和Mode-S偏差得到校正的水平相近。 KNMI。为了达到2.5 m / s左右的背景偏离值，航向偏差校正是最重要的一种。对于特定的飞机，VarBC的行为得到了更精确的评估，其中展示了其适应由于飞机维修等原因而迅速变化的能力。此外，当分别检查两个风分量的预测变量时，它们似乎在大部分时间收敛于相似的速度和航向校正。附加的质量控制使背景偏离值达到2.2 m / s，同时将法国AROME域中被吸收的飞机观测数量增加了十倍。对于特定的飞机，VarBC的行为得到了更精确的评估，其中展示了其适应由于飞机维修等原因而迅速变化的能力。此外，当分别检查两个风分量的预测变量时，它们似乎在大部分时间收敛于相似的速度和航向校正。附加的质量控制使背景偏离值达到2.2 m / s，同时将法国AROME域中被吸收的飞机观测数量增加了十倍。对于特定的飞机，VarBC的行为得到了更精确的评估，其中展示了其适应由于飞机维修等原因而迅速变化的能力。此外，当分别检查两个风分量的预测变量时，它们似乎在大部分时间收敛于相似的速度和航向校正。附加的质量控制使背景偏离值达到2.2 m / s，同时将法国AROME域中被吸收的飞机观测数量增加了十倍。