Seasonal variations of electron densities below 100 km at mid-latitudes—II Electron densities and atmospheric circulation

1969 ◽  
Vol 31 (5) ◽  
pp. 703-729 ◽  
Author(s):  
J.B Gregory ◽  
A.H Manson
Keyword(s):  
Atmospheric Circulation ◽  
Seasonal Variations ◽  
Electron Densities

scholarly journals Seasonal Aspects of an Objective Climatology of Anticyclones Affecting the Mediterranean

2014 ◽  
Vol 27 (24) ◽  
pp. 9272-9289 ◽  
Author(s):  
Maria Hatzaki ◽  
Helena A. Flocas ◽  
Ian Simmonds ◽  
John Kouroutzoglou ◽  
Kevin Keay ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Seasonal Variations ◽  
Mediterranean Region ◽  
Tracking Algorithm ◽  
Automatic Identification ◽  
Research Perspectives ◽  
The Mediterranean ◽  
Frequency Generation ◽  
New Research ◽  
Seasonal Aspects

Abstract An objective climatology of anticyclones over the greater Mediterranean region is presented based on the Interim ECMWF Re-Analysis (ERA-Interim) for a 34-yr period (1979–2012) and the Melbourne University automatic identification and tracking algorithm. The scheme’s robustness and reliability for the transient extratropical propagation of anticyclones, with the appropriate choices of parameter settings, has been established and the results obtained here present new research perspectives on anticyclonic activity affecting the Mediterranean. Properties of Mediterranean anticyclones, such as frequency, generation and dissipation, movement, scale, and depth are investigated. The highest frequency of anticyclones is found over continental areas, while the highest maritime frequency occurs over closed basins exhibiting also maxima of anticyclogenesis. There is a significant seasonality in system density and anticyclogenesis maxima, this being associated with the seasonal variations of the larger-scale atmospheric circulation that affect the greater Mediterranean region.

scholarly journals Annual and seasonal variations in the low-latitude topside ionosphere

1998 ◽  
Vol 16 (8) ◽  
pp. 974-985 ◽  
Author(s):  
Y. Z. Su ◽  
G. J. Bailey ◽  
K.-I. Oyama
Keyword(s):  
Seasonal Variations ◽  
Topside Ionosphere ◽  
Neutral Wind ◽  
Electron Densities ◽  
Low Latitude ◽  
Time Model ◽  
Model Calculations ◽  
Neutral Gas ◽  
Summer Hemisphere ◽  
Winter Hemisphere

Abstract. Annual and seasonal variations in the low-latitude topside ionosphere are investigated using observations made by the Hinotori satellite and the Sheffield University Plasmasphere Ionosphere Model (SUPIM). The observed electron densities at 600 km altitude show a strong annual anomaly at all longitudes. The average electron densities of conjugate latitudes within the latitude range ±25° are higher at the December solstice than at the June solstice by about 100 during daytime and 30 during night-time. Model calculations show that the annual variations in the neutral gas densities play important roles. The model values obtained from calculations with inputs for the neutral densities obtained from MSIS86 reproduce the general behaviour of the observed annual anomaly. However, the differences in the modelled electron densities at the two solstices are only about 30 of that seen in the observed values. The model calculations suggest that while the differences between the solstice values of neutral wind, resulting from the coupling of the neutral gas and plasma, may also make a significant contribution to the daytime annual anomaly, the E×B drift velocity may slightly weaken the annual anomaly during daytime and strengthen the anomaly during the post-sunset period. It is suggested that energy sources, other than those arising from the 6 difference in the solar EUV fluxes at the two solstices due to the change in the Sun-Earth distance, may contribute to the annual anomaly. Observations show strong seasonal variations at the solstices, with the electron density at 600 km altitude being higher in the summer hemisphere than in the winter hemisphere, contrary to the behaviour in NmF2. Model calculations confirm that the seasonal behaviour results from effects caused by transequatorial component of the neutral wind in the direction summer hemisphere to winter hemisphere.

Sign in / Sign up

Export Citation Format

Share Document