scholarly journals Climatology of thermospheric neutral winds over Oukaïmeden Observatory in Morocco

2017 ◽  
Vol 35 (1) ◽  
pp. 161-170 ◽  
Author(s):  
Mohamed Kaab ◽  
Zouhair Benkhaldoun ◽  
Daniel J. Fisher ◽  
Brian Harding ◽  
Aziza Bounhir ◽  
...  
Keyword(s):  
Dissociative Recombination ◽  
Horizontal Wind ◽  
Wind Model ◽  
Neutral Winds ◽  
Zonal Winds ◽  
Early Evening ◽  
Atlas Mountains ◽  
Fabry Perot ◽  
Meridional Winds ◽  
High Atlas Mountains

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.

scholarly journals Thermospheric winds and temperatures above Mawson, Antarctica, observed with an all-sky imaging, Fabry-Perot spectrometer

2009 ◽  
Vol 27 (5) ◽  
pp. 2225-2235 ◽  
Author(s):  
C. Anderson ◽  
M. Conde ◽  
P. Dyson ◽  
T. Davies ◽  
M. J. Kosch
Keyword(s):  
Large Scale ◽  
Atmospheric Model ◽  
Horizontal Wind ◽  
Data Set ◽  
Average Behavior ◽  
Wind Speeds ◽  
Zonal Winds ◽  
F Region ◽  
Fabry Perot ◽  
Thermospheric Winds

Abstract. A new all-sky imaging Fabry-Perot spectrometer has been installed at Mawson station (67°36' S, 62°52' E), Antarctica. This instrument is capable of recording independent spectra from many tens of locations across the sky simultaneously. Useful operation began in March 2007, with spectra recorded on a total of 186 nights. Initial analysis has focused on the large-scale daily and average behavior of winds and temperatures derived from observations of the 630.0 nm airglow line of atomic oxygen, originating from a broad layer centered around 240 km altitude, in the ionospheric F-region. The 1993 Horizontal Wind Model (HWM93), NRLMSISE-00 atmospheric model, and the Coupled Thermosphere/Ionosphere Plasmasphere (CTIP) model were used for comparison. During the geomagnetically quiet period studied, observed winds and temperatures were generally well modelled, although temperatures were consistently higher than NRLMSISE-00 predicted, by up to 100 K. CTIP temperatures better matched our data, particularly later in the night, but predicted zonal winds which were offset from those observed by 70–180 ms−1 westward. During periods of increased activity both winds and temperatures showed much greater variability over time-scales of less than an hour. For the active night presented here, a period of 45 min saw wind speeds decrease by around 180 ms−1, and temperatures increase by approximately 100 K. Active-period winds were poorly modelled by HWM93 and CTIP, although observed median temperatures were in better agreement with NRLMSISE-00 during such periods. Average behavior was found to be generally consistent with previous studies of thermospheric winds above Mawson. The collected data set was representative of quiet geomagnetic and solar conditions. Geographic eastward winds in the afternoon/evening generally continued until around local midnight, when winds turned equatorward. Geographic meridional and zonal winds in the afternoon were approximately 50 ms−1 weaker than expected from HWM93, as was the transition to equatorward flow around midnight. There was also a negligible geographic zonal component to the post-midnight wind where HWM93 predicted strong westward flow. Average temperatures between 19:00 and 04:00 local solar time were around 60 K higher than predicted by NRLMSISE-00.

scholarly journals Global empirical wind model for the upper mesosphere/lower thermosphere. I. Prevailing wind

2000 ◽  
Vol 18 (3) ◽  
pp. 300-315 ◽  
Author(s):  
Y. I. Portnyagin ◽  
T. V. Solovjova
Keyword(s):  
General Circulation ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Systematic Bias ◽  
Prevailing Wind ◽  
Wind Model ◽  
Zonal Winds ◽  
Meridional Winds ◽  
Contour Plots ◽  
Thermospheric Dynamics

Abstract. An updated empirical climatic zonally averaged prevailing wind model for the upper mesosphere/lower thermosphere (70-110 km), extending from 80°N to 80°S is presented. The model is constructed from the fitting of monthly mean winds from meteor radar and MF radar measurements at more than 40 stations, well distributed over the globe. The height-latitude contour plots of monthly mean zonal and meridional winds for all months of the year, and of annual mean wind, amplitudes and phases of annual and semiannual harmonics of wind variations are analyzed to reveal the main features of the seasonal variation of the global wind structures in the Northern and Southern Hemispheres. Some results of comparison between the ground-based wind models and the space-based models are presented. It is shown that, with the exception of annual mean systematic bias between the zonal winds provided by the ground-based and space-based models, a good agreement between the models is observed. The possible origin of this bias is discussed.Key words: Meteorology and Atmospheric dynamics (general circulation; middle atmosphere dynamics; thermospheric dynamics)

scholarly journals Seasonal variations in the horizontal wind structure from 0–100 km above Rothera station, Antarctica (67° S, 68° W)

2005 ◽  
Vol 5 (4) ◽  
pp. 4291-4310 ◽  
Author(s):  
R. E. Hibbins ◽  
J. D. Shanklin ◽  
P. J. Espy ◽  
M. J. Jarvis ◽  
D. M. Riggin ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Model Atmosphere ◽  
Horizontal Wind ◽  
Zero Crossing ◽  
Zonal Winds ◽  
Wind Structure ◽  
Falling Sphere ◽  
Wind Climatology ◽  
Meridional Winds ◽  
Summer Time

Abstract. A medium frequency spaced-antenna radar has been operating at Rothera station, Antarctica (67° S, 68° W) for two periods, between 1997–1998 and since 2002, measuring winds in the mesosphere and lower thermosphere. In this paper monthly mean winds are derived and presented along with three years of radiosonde balloon data for comparison with the HWM-93 model atmosphere and other high latitude southern hemisphere sites. The observed meridional winds are slightly more northwards than those predicted by the model above 80 km in the winter months and below 80 km in summer. In addition, the altitude of the summer time zero crossing of the zonal winds above the westward jet is overestimated by the model by up to 8 km. These data are then merged with the wind climatology obtained from falling sphere measurements made during the PORTA campaign at Rothera in early 1998 and the HWM-93 model atmosphere to generate a complete zonal wind climatology between 0 and 100 km as a benchmark for future studies at Rothera. A westwards (eastwards) maximum of 44 ms−1 at 67 km altitude occurs in mid December (62 ms−1 at 37 km in mid July). The 0 ms−1 wind contour reaches a maximum altitude of 90 km in mid November and a minimum altitude of 18 km in January extending into mid March at 75 km and early October at 76 km.

scholarly journals Seasonal variations in the horizontal wind structure from 0-100 km above Rothera station, Antarctica (67° S, 68° W)

2005 ◽  
Vol 5 (11) ◽  
pp. 2973-2980 ◽  
Author(s):  
R. E. Hibbins ◽  
J. D. Shanklin ◽  
P. J. Espy ◽  
M. J. Jarvis ◽  
D. M. Riggin ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Model Atmosphere ◽  
Horizontal Wind ◽  
Zero Crossing ◽  
Zonal Winds ◽  
Wind Structure ◽  
Falling Sphere ◽  
Wind Climatology ◽  
Meridional Winds ◽  
Summer Time

Abstract. A medium frequency spaced-antenna radar has been operating at Rothera station, Antarctica (67° S, 68° W) for two periods, between 1997-1998 and since 2002, measuring winds in the mesosphere and lower thermosphere. In this paper monthly mean winds are derived and presented along with three years of radiosonde balloon data for comparison with the HWM-93 model atmosphere and other high latitude southern hemisphere sites. The observed meridional winds are slightly more northwards than those predicted by the model above 80 km in the winter months and below 80 km in summer. In addition, the altitude of the summer time zero crossing of the zonal winds above the westward jet is overestimated by the model by up to 8 km. These data are then merged with the wind climatology obtained from falling sphere measurements made during the PORTA campaign at Rothera in early 1998 and the HWM-93 model atmosphere to generate a complete zonal wind climatology between 0 and 100 km as a benchmark for future studies at Rothera. A westwards (eastwards) maximum of 44 ms-1 at 67 km altitude occurs in mid December (62 ms-1 at 37 km in mid July). The 0 ms-1 wind contour reaches a maximum altitude of 90 km in mid November and a minimum altitude of 18 km in January extending into mid March at 75 km and early October at 76 km.

scholarly journals FPI observations of nighttime mesospheric and thermospheric winds in China and their comparisons with HWM07

2013 ◽  
Vol 31 (8) ◽  
pp. 1365-1378 ◽  
Author(s):  
W. Yuan ◽  
X. Liu ◽  
J. Xu ◽  
Q. Zhou ◽  
G. Jiang ◽  
...  
Keyword(s):  
Zonal Wind ◽  
Annual Variation ◽  
Middle Atmosphere ◽  
Geomagnetic Latitude ◽  
Meridional Wind ◽  
Central China ◽  
Horizontal Wind ◽  
Zonal Winds ◽  
Meridional Winds ◽  
First Time

Abstract. We analyzed the nighttime horizontal neutral winds in the middle atmosphere (~ 87 and ~ 98 km) and thermosphere (~ 250 km) derived from a Fabry–Perot interferometer (FPI), which was installed at Xinglong station (40.2° N, 117.4° E) in central China. The wind data covered the period from April 2010 to July 2012. We studied the annual, semiannual and terannual variations of the midnight winds at ~ 87 km, ~ 98 km and ~ 250 km for the first time and compared them with Horizontal Wind Model 2007 (HWM07). Our results show the following: (1) at ~ 87 km, both the observed and model zonal winds have similar phases in the annual and semiannual variations. However, the HWM07 amplitudes are much larger. (2) At ~ 98 km, the model shows strong eastward wind in the summer solstice, resulting in a large annual variation, while the observed strongest component is semiannual. The observation and model midnight meridional winds agree well. Both are equatorward throughout the year and have small amplitudes in the annual and semiannual variations. (3) There are large discrepancies between the observed and HWM07 winds at ~ 250 km. This discrepancy is largely due to the strong semiannual zonal wind in the model and the phase difference in the annual variation of the meridional wind. The FPI annual variation coincides with the results from Arecibo, which has similar geomagnetic latitude as Xinglong station. In General, the consistency of FPI winds with model winds is better at ~ 87 and ~ 98 km than that at ~ 250 km. We also studied the seasonally and monthly averaged nighttime winds. The most salient features include the following: (1) the seasonally averaged zonal winds at ~ 87 and ~ 98 km typically have small variations throughout the night. (2) The model zonal and meridional nighttime wind variations are typically much larger than those of observations at ~ 87 km and ~ 98 km. (3) At ~ 250 km, model zonal wind compares well with the observation in the winter. For spring and autumn, the model wind is more eastward before ~ 03:00 LT but more westward after. The observed nighttime zonal and meridional winds on average are close to zero in the summer and autumn, which indicates a lack of strong stable tides. The consistency of FPI zonal wind with model wind at ~ 250 km is better than the meridional wind.

scholarly journals A Comparison of Meteor Radar Observation over China Region with Horizontal Wind Model (HWM14)

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 98
Author(s):  
Qiong Tang ◽  
Yufeng Zhou ◽  
Zhitao Du ◽  
Chen Zhou ◽  
Jiandong Qiao ◽  
...  
Keyword(s):  
Model Prediction ◽  
Meridional Wind ◽  
Radar Observation ◽  
Horizontal Wind ◽  
Meteor Radar ◽  
Wind Fields ◽  
Wind Model ◽  
Zonal Winds ◽  
Radar Measurements ◽  
China Region

This paper compares the wind fields measured by the meteor radar at Mohe, Beijing, Wuhan, and Sanya stations and horizontal wind model (HWM14) predictions. HWM14 appears to successfully reproduce the height-time distribution of the monthly mean zonal winds, although large discrepancies occur in wind speed between the model and measurement, especially in the summer and winter months. For meridional wind, the consistency between model prediction and radar observation is worse than that of zonal wind. The consistency between radar measurements and model prediction at Sanya station is worse than other sites located at higher latitudes. Harmonic analysis reveals large discrepancies in diurnal, semidiurnal, and terdiurnal tides extracted from meteor radar observations and HWM14 predictions.

scholarly journals Mid-latitude Summer Nighttime Anomaly (MSNA) – observations and model simulations

2011 ◽  
Vol 29 (1) ◽  
pp. 157-165 ◽  
Author(s):  
S. V. Thampi ◽  
N. Balan ◽  
C. Lin ◽  
H. Liu ◽  
M. Yamamoto
Keyword(s):  
Diurnal Variation ◽  
Northern Hemisphere ◽  
Electric Fields ◽  
Horizontal Wind ◽  
Model Simulations ◽  
Neutral Winds ◽  
Ionosphere Model ◽  
Mu Radar ◽  
Meridional Winds ◽  
Wind Velocities

Abstract. In this paper, we present model simulations of the Mid-latitude Summer Nighttime Anomaly (MSNA) in the Northern Hemisphere, which is characterized by noon-time dip and evening maximum in the diurnal variation of the ionospheric density. The simulations are carried out using SUPIM (Sheffield University Plasmasphere Ionosphere Model) for solar minimum at 135° E longitude where MSNA is most pronounced in the Northern Hemisphere. The simulations are used to understand the relative importance of electric fields, and zonal and meridional winds in the formation of MSNA. The wind velocities measured by the Middle and Upper atmosphere radar (MU radar) and those obtained from the horizontal wind model (HWM93) are used. The results show that the formation of MSNA is closely related to the diurnal variation of the neutral winds with little contribution from the changes in the electric fields. The observed features of MSNA are better reproduced when MU radar winds are used as model input rather than HWM winds.

scholarly journals A Study of Atmospheric Temperature and Wind Profiles Obtained from Rocketsondes in the Chinese Midlatitude Region

2015 ◽  
Vol 32 (4) ◽  
pp. 722-735 ◽  
Author(s):  
Z. Sheng ◽  
Y. Jiang ◽  
L. Wan ◽  
Z. Q. Fan
Keyword(s):  
Climate Model ◽  
Atmospheric Temperature ◽  
Horizontal Wind ◽  
Naval Research ◽  
Zonal Winds ◽  
Broadband Emission ◽  
Meridional Winds ◽  
Mean Differences ◽  
Wind Profiles ◽  
First Time

AbstractIn November 2004, five TK-1 meteorological rockets were launched at Jiuquan Satellite Launch Center in China for the first time. The observations are compared with models, reanalysis, and satellite datasets. The mean differences of temperature between the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) and the rocketsondes are about 0.7–2.4 K in the stratosphere and −6 K in the mesosphere. The temperature biases between the Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar, Exosphere (NRLMSISE-00)/Whole Atmosphere Community Climate Model (WACCM), and the rocketsondes are small (~1–2 K) in the lower stratosphere and largest near the stratopause. Both models strongly overestimated the temperature by 11 K on average. The discrepancies of horizontal winds between the Horizontal Wind Model 07 (HWM07)/WACCM and the rocketsondes reached the maximum in the upper stratosphere and the lower mesosphere. The westerly observed zonal winds and equatorward meridional winds were two interesting phenomena that led to large biases in the upper stratosphere, which need further study.

scholarly journals Comparison of high-latitude thermospheric meridionalwinds I: optical and radar experimental comparisons

2004 ◽  
Vol 22 (3) ◽  
pp. 849-862 ◽  
Author(s):  
E. M. Griffin ◽  
I. C. F. Müller-Wodarg ◽  
A. Aruliah ◽  
A. Aylward
Keyword(s):  
Solar Cycle ◽  
High Latitude ◽  
Model Performance ◽  
Meridional Wind ◽  
Experimental Techniques ◽  
Horizontal Wind ◽  
Wind Model ◽  
Data Set ◽  
Neutral Winds ◽  
Eiscat Measurements

Abstract. Thermospheric neutral winds at Kiruna, Sweden (67.4°N, 20.4°E) are compared using both direct optical Fabry-Perot Interferometer (FPI) measurements and those derived from European incoherent scatter radar (EISCAT) measurements. This combination of experimental data sets, both covering well over a solar cycle of data, allows for a unique comparison of the thermospheric meridional component of the neutral wind as observed by different experimental techniques. Uniquely in this study the EISCAT measurements are used to provide winds for comparison using two separate techniques: the most popular method based on the work of Salah and Holt (1974) and the Meridional Wind Model (MWM) (Miller et al., 1997) application of servo theory. The balance of forces at this location that produces the observed diurnal pattern are investigated using output from the Coupled Thermosphere and Ionosphere (CTIM) numerical model. Along with detailed comparisons from short periods the climatological behaviour of the winds have been investigated for seasonal and solar cycle dependence using the experimental techniques. While there are features which are consistent between the 3 techniques, such as the evidence of the equinoctial asymmetry, there are also significant differences between the techniques both in terms of trends and absolute values. It is clear from this and previous studies that the high-latitude representation of the thermospheric neutral winds from the empirical Horizontal Wind Model (HWM), though improved from earlier versions, lacks accuracy in many conditions. The relative merits of each technique are discussed and while none of the techniques provides the perfect data set to address model performance at high-latitude, one or more needs to be included in future HWM reformulations. Key words. Meteorology and atmospheric dynamics (thermospheric dynamics), Ionosphere (ionosphere-atmosphere interactions, auroral ionosphere)

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