Title: Medium-scale thermospheric gravity waves in the high-resolution Whole Atmosphere Model: Seasonal, local time, and longitudinal variations Show Chinese title

Title: 中尺度热层重力波在高分辨率全大气模型中的研究：季节、地方时和经度变化

Abstract: This paper presents a study of the global medium-scale (scales<620 km) gravity wave (GW) activity (in terms of zonal wind variance) and its seasonal, local time and longitudinal variations by employing the enhanced-resolution (~50 km) Whole Atmosphere Model (WAMT254) and space-based observations for geomagnetically quiet conditions. It is found that the GW hotspots produced by WAMT254 in the troposphere and stratosphere agree well with previously well-studied orographic and non-orographic sources. In the ionosphere-thermosphere (IT) region, GWs spread out forming latitudinal band-like hotspots. During solstices, a primary maximum in GW activity is observed in WAMT254 and GOCE over winter mid-high latitudes, likely associated with higher-order waves with primary sources in polar night jet, fronts and polar vortex. During all the seasons, the enhancement of GWs around the geomagnetic poles as observed by GOCE (at ~250 km) is well captured by simulations. WAMT254 GWs in the IT region also show dependence on local time due to their interaction with migrating tides leading to diurnal and semidiurnal variations. The GWs are more likely to propagate up from the MLT region during westward/weakly-eastward phase of thermospheric tides, signifying the dominance of eastward GW momentum flux in the MLT. Additionally, as a novel finding, a wavenumber-4 signature in GW activity is predicted by WAMT254 between 6-12 LT in the tropics at ~250 km, which propagates eastward with local time. This behavior is likely associated with the modulation of GWs by wave-4 signal of non-migrating tides in the lower thermospheric zonal winds. Show Chinese abstract

Abstract: 本文通过使用增强分辨率（约50公里）的全大气模型（WAMT254）和地磁安静条件下的空间观测数据，研究了全球中尺度（尺度<620公里）重力波（GW）活动（以纬向风方差为指标）及其季节、地方时和经度变化。发现WAMT254在对流层和平流层产生的GW热点与之前广泛研究的地形和非地形源高度一致。在电离层-热层（IT）区域，GWs扩散形成纬度带状热点。在至日期间，在冬季中高纬度地区WAMT254和GOCE观测到GW活动的主要峰值，可能与极夜急流、锋面和极涡中的高阶波有关。在所有季节中，GOCE（在约250公里高度）观测到的磁纬极附近GW增强现象被模拟结果很好地捕捉。WAMT254在IT区域的GW也由于与迁移潮汐的相互作用而表现出对地方时的依赖性，导致昼夜和半昼夜变化。在热层潮汐的西向/弱东向相位期间，GW更有可能从中间层顶（MLT）区域向上传播，表明MLT中东向GW动量通量占主导地位。此外，作为一项新发现，WAMT254在热带地区约250公里高度、地方时6-12小时范围内预测出GW活动的波数-4特征，该特征随地方时向东传播。这种行为可能与非迁移潮汐的波-4信号对低热层纬向风中GW的调制有关。