Abstract
Abstract. In order to explore coupling between the thermosphere and ionosphere and to address the lack of data relating to thermospheric neutral winds and temperatures over the African sector, a new system of instruments was installed at the Oukaïmeden Observatory located in the high Atlas Mountains, 75 km south of Marrakesh, Morocco (31.206° N, 7.866° W, 22.84° N magnetic). In this work we present the first multi-year results of the climatology of meridional and zonal winds obtained during the period from January 2014 to February 2016, including observations from 648 nights. The measurements are obtained using an imaging Fabry–Pérot interferometer, which measures the 630.0 nm emissions caused by dissociative recombination of O2+. The basic climatology of the winds is as expected, showing zonal winds that are strongly eastward in the early evening just after sunset with a speed of 50 to 100 m s−1 decreasing in magnitude, and reversing directions in the local summer months, towards sunrise. The meridional winds are slightly poleward in the early evening during the local winter, before reversing directions around 21:00 LT. In the local summer months, the meridional winds are equatorward for the entire night, reaching a maximum equatorward speed of 75 m s−1. We compare the observed climatologies of neutral winds to that provided by the recently updated Horizontal Wind Model (HWM14) in order to validate that model's predictions of the thermospheric wind patterns over the eastern portion of Africa. The model captures much of the features in the observational climatologies. The most notable exception is for the zonal winds during local summer, when the maximum eastward wind in the observations occurs approximately 4 h later than seen in the model results.
Highlights
Space weather is a relatively new field of study and encompasses understanding how the near-space environment responds to forcing from lower-atmosphere weather systems as well as conditions on the Sun
We present a 26-month climatology of the neutral winds as well as a comparison to the recently updated Horizontal Wind Model (HWM14; Drob et al, 2015) and to prior measurements made in different longitude sectors but at similar geographic and geomagnetic latitudes
We see that there are significant disagreements between the observations and models for these components. This could be a limitation of the analysis technique used, as the amplitudes of these components are on the order of the uncertainties in the measurements, Liu et al (2016) found that, regionally and seasonally, HWM14 underestimates the neutral winds when compared to GOCE satellite measurements
Summary
Within the past several years, significant ground-based infrastructure has been deployed as part of the ISWI and other initiatives to address the deficiency of measurements in the African sector (e.g., Yizengaw et al, 2013) Despite this progress, critical measurements of thermospheric winds and temperatures are almost completely lacking in this region. It was within the framework of the ISWI that in November 2013, a team of scientists from the University of Illinois at Urbana-Champaign in the United States deployed a suite of optical instruments at the Oukaïmeden Observatory in the Atlas Mountains near Marrakesh, Morocco (31.206◦ N, 7.866◦ W, 22.84◦ N magnetic) They installed an imaging Fabry–Pérot interferometer (FPI) similar to what is described in Makela et al (2009) in order to measure the nighttime thermospheric winds and temperatures. Prior measurements made in different longitude sectors but at similar geographic and geomagnetic latitudes
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