Equatorial Waves, Diurnal Tides and Small‐Scale Thermal Variability in the Tropical Lower Stratosphere From COSMIC‐2 Radio Occultation
Equatorial Waves, Diurnal Tides and Small‐Scale Thermal Variability in the Tropical Lower Stratosphere From COSMIC‐2 Radio Occultation
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DOI：
10.1029/2020jd033969
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
W. Randel;Fei Wu;A. Podglajen
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文献类型：
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作者：
W. Randel;Fei Wu;A. Podglajen
一个名为COSMIC-2（气象、电离层和气候星座观测系统-2）的新无线电掩星星座正在提供前所未有的热带大气密集测量，平均每天在40°N-S范围内进行4,000多次高质量观测。我们使用这些数据来评估2019年10月至2020年4月期间热带低平流层的大尺度和小尺度热变率。对6小时网格COSMIC-2数据的时空谱分析揭示了丰富的行星尺度行波谱，包括开尔文波、混合Rossby重力波和惯性重力波，以及传播的日潮汐。这些相干模态显示出从热带对流层顶到平流层低层（17-25公里）的增强振幅。小尺度温度变化的特征（计算为与网格场的偏差）揭示了系统的空间模式，包括非洲和南美洲的时间平均最大值，覆盖了频繁的深对流。小尺度变化也表现出在赤道平流层下部的瞬态极大值，与静稳定性的局部变化有关，与大尺度开尔文波有关。新的COSMIC-2观测为热带对流层顶附近和上方的大尺度和小尺度波的丰富光谱提供了新的细节。
A new constellation of radio occultation satellites called COSMIC‐2 (Constellation Observing System for Meteorology, Ionosphere, and Climate‐2) is providing unprecedented dense measurements of the tropical atmosphere, with on average more than 4,000 high quality observations per day over 40°N–S. We use these data to evaluate large‐ and small‐scale thermal variability in the tropical lower stratosphere during October 2019 – April 2020. Space‐time spectral analysis of 6‐hourly gridded COSMIC‐2 data reveals a rich spectrum of traveling planetary‐scale waves, including Kelvin waves, mixed Rossby‐gravity waves and inertia gravity waves, in addition to propagating diurnal tides. These coherent modes show enhanced amplitudes from the tropical tropopause through the lower stratosphere (∼17–25 km). Characteristics of small‐scale temperature variances, calculated as deviations from the gridded fields, reveal systematic spatial patterns including time average maxima over Africa and South America overlying frequent deep convection. Small‐scale variances also exhibit transient maxima in the equatorial lower stratosphere tied to local variations in static stability, associated with large‐scale Kelvin waves. The new COSMIC‐2 observations provide novel details on the rich spectrum of large‐ and small‐scale waves near and above the tropical tropopause.