New results on equatorial thermospheric winds and temperatures from Ethiopia, Africa
New results on equatorial thermospheric winds and temperatures from Ethiopia, Africa
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非洲埃塞俄比亚赤道热层风和温度的新结果
DOI：
10.5194/angeo-35-333-2017
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发表时间：
2017
影响因子：
1.9
通讯作者：
S. Sanders
中科院分区：
文献类型：
--
作者：
F. Tesema;R. Mesquita;J. Meriwether;B. Damtie;M. Nigussie;J. Makela;D. J. Fisher;B. Harding;E. Yizengaw;S. Sanders
抽象的。赤道热层风、温度和 630 nm 相对强度的测量是使用成像法布里-珀罗干涉仪 (FPI) 获得的，该干涉仪最近部署在埃塞俄比亚巴赫达尔大学（北纬 11.6°，东经 37.4°，北纬 3.7°）。本研究获得的结果涵盖 2015 年 11 月至 2016 年 4 月之间的 6 个月（53 个夜晚的可用数据）。月平均值（包括当地冬季和春分季节）显示，最大月平均纬向风的震级通常在 70 至 90ms−1 范围内，并且在 19:00 至 21:00LT 之间为东风。与之前对当地这一时期赤道热层风的研究相比，其震级比在秘鲁扇区观测到的最大纬向风速要弱得多，但与巴西 FPI 结果相当。傍晚时分，冬季的经向风速为极地方向 30 至 50ms−1，春分月份的赤道方向风速为 10 至 25ms−1。冬季极地风的方向被认为主要是由于从夏半球流向冬半球的半球间风流的存在造成的。赤道风潮在晚上晚些时候观测到，并在冬季转移到当地时间较晚的时间，在春分月份转移到当地时间较早的时间。纬向风和经向风的最大速度也观察到显着的夜间变化。温度观测结果显示，午夜最高气温 (MTM) 通常出现在 00:30 至 02:00LT 之间。 2016年1月MTM振幅为 ∼ 110K，其他月份均较小。当地MTM出现与午夜前赤道风出现的时间差一般为60至180分钟。 MTM 出现后（02:00LT 后）还观察到了经向风逆转。将气候模型 HWM14 和 MSIS-00 与观测结果进行比较，HWM14 模型通常能够很好地预测纬向风观测结果，但冬季模型值高出 25ms−1。 HWM14 模型经向风与观测结果总体吻合良好。最后，MSIS-00 模型将当地冬季傍晚时分的温度高估了 50 至 75K。除此之外，总体一致性良好，尽管与之前的研究一致，与 FPI 数据相比，该模型未能重现 6 个月中任何一个月的 MTM 峰值。
Abstract. Measurements of equatorial thermospheric winds, temperatures, and 630 nm relative intensities were obtained using an imaging Fabry–Perot interferometer (FPI), which was recently deployed at Bahir Dar University in Ethiopia (11.6° N, 37.4° E, 3.7° N magnetic). The results obtained in this study cover 6 months (53 nights of useable data) between November 2015 and April 2016. The monthly-averaged values, which include local winter and equinox seasons, show the magnitude of the maximum monthly-averaged zonal wind is typically within the range of 70 to 90 ms−1 and is eastward between 19:00 and 21:00 LT. Compared to prior studies of the equatorial thermospheric wind for this local time period, the magnitude is considerably weaker as compared to the maximum zonal wind speed observed in the Peruvian sector but comparable to Brazilian FPI results. During the early evening, the meridional wind speeds are 30 to 50 ms−1 poleward during the winter months and 10 to 25 ms−1 equatorward in the equinox months. The direction of the poleward wind during the winter months is believed to be mainly caused by the existence of the interhemispheric wind flow from the summer to winter hemispheres. An equatorial wind surge is observed later in the evening and is shifted to later local times during the winter months and to earlier local times during the equinox months. Significant night-to-night variations are also observed in the maximum speed of both zonal and meridional winds. The temperature observations show the midnight temperature maximum (MTM) to be generally present between 00:30 and 02:00 LT. The amplitude of the MTM was ∼ 110 K in January 2016 with values smaller than this in the other months. The local time difference between the appearance of the MTM and a pre-midnight equatorial wind was generally 60 to 180 min. A meridional wind reversal was also observed after the appearance of the MTM (after 02:00 LT). Climatological models, HWM14 and MSIS-00, were compared to the observations and the HWM14 model generally predicted the zonal wind observations well with the exception of higher model values by 25 ms−1 in the winter months. The HWM14 model meridional wind showed generally good agreement with the observations. Finally, the MSIS-00 model overestimated the temperature by 50 to 75 K during the early evening hours of local winter months. Otherwise, the agreement was generally good, although, in line with prior studies, the model failed to reproduce the MTM peak for any of the 6 months compared with the FPI data.