Diurnal, seasonal, annual, and semi-annual variations of ionospheric parameters at different latitudes in East Asian sector during ascending phase of solar activity

We analyzed ionospheric parameters including the critical frequency of the F2 layer (foF2), the peak height of the F2 layer (hmF2), and the scale height at hmF2 (HT) from 2006 to 2012 (ascending phase of solar activity) at Hainan (19.5° N, 109.1° E, MLat. 9.7° N), Irkutsk (52.4° N, 104.3° E, MLat. 42.5° N), and Norilsk (69.2° N, 88.0° E, MLat. 59.8° N) stations (low, middle and high latitudes). We have used manual scaled digisonde ionogram data. Studies of foF2 and hmF2 di-urnal-seasonal variations continue those made earlier for East Asia. Features peculiar for the ascending phase of solar activity are mostly consistent to those for de-scending phase, except for the features of sunset and nighttime hmF2 variations. Features of annual and semi-annual variations recorded by a digisonde agree with those obtained by a satellite occultation and TEC map. We also obtained seasonal, diurnal, annual, and semi-annual variations of the ionospheric parameter HT (scale height at hmF2) from digisonde data, which differ from foF2 variations and hmF2 features.

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A great space weather event in February 1730

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832735 ◽

2018 ◽

Vol 616 ◽

pp. A177 ◽

Cited By ~ 10

Author(s):

Hisashi Hayakawa ◽

Yusuke Ebihara ◽

José M. Vaquero ◽

Kentaro Hattori ◽

Víctor M. S. Carrasco ◽

...

Keyword(s):

Solar Activity ◽

East Asia ◽

Magnetic Storm ◽

East Asian ◽

Active Phase ◽

Magnetic Storms ◽

Historical Records ◽

Maximum Phase ◽

Weather Event ◽

Space Weather Event

Aims. Historical records provide evidence of extreme magnetic storms with equatorward auroral extensions before the epoch of systematic magnetic observations. One significant magnetic storm occurred on February 15, 1730. We scale this magnetic storm with auroral extension and contextualise it based on contemporary solar activity. Methods. We examined historical records in East Asia and computed the magnetic latitude (MLAT) of observational sites to scale magnetic storms. We also compared them with auroral records in Southern Europe. We examined contemporary sunspot observations to reconstruct detailed solar activity between 1729 and 1731. Results. We show 29 auroral records in East Asian historical documents and 37 sunspot observations. Conclusions. These records show that the auroral displays were visible at least down to 25.8° MLAT throughout East Asia. In comparison with contemporary European records, we show that the boundary of the auroral display closest to the equator surpassed 45.1° MLAT and possibly came down to 31.5° MLAT in its maximum phase, with considerable brightness. Contemporary sunspot records show an active phase in the first half of 1730 during the declining phase of the solar cycle. This magnetic storm was at least as intense as the magnetic storm in 1989, but less intense than the Carrington event.

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Seasonal Variations of the Synoptic-Scale Transient Eddy Activity and Polar Front Jet over East Asia

Journal of Climate ◽

10.1175/2009jcli3225.1 ◽

2010 ◽

Vol 23 (12) ◽

pp. 3222-3233 ◽

Cited By ~ 56

Author(s):

Xuejuan Ren ◽

Xiuqun Yang ◽

Cuijiao Chu

Keyword(s):

East Asia ◽

Seasonal Variations ◽

East Asian ◽

Polar Front ◽

Transient Eddy ◽

Synoptic Scale ◽

Wind Fields ◽

The North ◽

Upper Level ◽

Polar Front Jet

Abstract Seasonal variations of the synoptic-scale transient eddy activity (STEA) and the jet streams over East Asia are examined through analysis of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data. Extracted from the 6-hourly upper-level wind fields, the distribution of the jet core numbers exhibits a distinct geographical border for the East Asian subtropical jet (EASJ) and the East Asian polar front jet (EAPJ) at the latitudes of the northern Tibetan Plateau (TP). In the cool seasons, two branches of the STEA and low-level baroclinicity exist over the East Asian landmass, accompanied by the two-jet state of the EASJ and EAPJ. In the warm seasons, a single jet pattern of the EASJ along the north flank of the TP is accompanied by the weakened STEA over the mid- to high latitudes of East Asia. Further analysis shows two distinct features of the seasonal variations of the STEA over East Asia, compared with that over the North Pacific. First, during the transitional period of April–June, the main STEA band over East Asia migrates northward dramatically, in conjunction with the EAPJ shifting in the same direction. Second, both the upper-level STEA and the lower-level baroclinicity poleward of the TP are prosperous in spring. The relationship between the STEA, baroclinicity, vertical wind shear, and static stability in the EAPJ region in different seasons is further investigated. It is found that in addition to the time-mean wind fields, the rapid increase in the sensible heat flux poleward side of the TP region in spring and the associated boundary layer processes are partially responsible for the spring prosperity of the local baroclinicity and the STEA.

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Projections of East Asian summer monsoon change at global warming of 1.5 and 2 °C

Earth System Dynamics ◽

10.5194/esd-9-427-2018 ◽

2018 ◽

Vol 9 (2) ◽

pp. 427-439 ◽

Cited By ~ 8

Author(s):

Jiawei Liu ◽

Haiming Xu ◽

Jiechun Deng

Keyword(s):

East Asia ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Precipitation Change ◽

High Latitudes ◽

Multimodel Ensemble ◽

Epr Method ◽

Asian Summer

Abstract. Much research is needed regarding the two long-term warming targets of the 2015 Paris Agreement, i.e., 1.5 and 2 ∘C above pre-industrial levels, especially from a regional perspective. The East Asian summer monsoon (EASM) intensity change and associated precipitation change under both warming targets are explored in this study. The multimodel ensemble mean projections by 19 CMIP5 models show small increases in EASM intensity and general increases in summer precipitation at 1.5 and 2 ∘C warming, but with large multimodel standard deviations. Thus, a novel multimodel ensemble pattern regression (EPR) method is applied to give more reliable projections based on the concept of emergent constraints, which is effective at tightening the range of multimodel diversity and harmonize the changes of different variables over the EASM region. Future changes projected by using the EPR method suggest decreased precipitation over the Meiyu belt and increased precipitation over the high latitudes of East Asia and Central China, together with a considerable weakening of EASM intensity. Furthermore, reduced precipitation appears over 30–40∘ N of East Asia in June and over the Meiyu belt in July, with enhanced precipitation at their north and south sides. These changes in early summer are attributed to a southeastward retreat of the western North Pacific subtropical high (WNPSH) and a southward shift of the East Asian subtropical jet (EASJ), which weaken the moisture transport via southerly wind at low levels and alter vertical motions over the EASM region. In August, precipitation would increase over the high latitudes of East Asia with more moisture from the wetter area over the ocean in the east and decrease over Japan with westward extension of WNPSH. These monthly precipitation changes would finally contribute to a tripolar pattern of EASM precipitation change at 1.5 and 2 ∘C warming. Corrected EASM intensity exhibits a slight difference between 1.5 and 2 ∘C, but a pronounced moisture increase during extra 0.5 ∘C leads to enhanced EASM precipitation over large areas in East Asia at 2 ∘C warming.

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Seasonal Variations of the Optimum Reliable Frequencies During Maximum and Minimum Periods of Solar Cycle 24

Al-Mustansiriyah Journal of Science ◽

10.23851/mjs.v31i4.887 ◽

2020 ◽

Vol 31 (4) ◽

pp. 15

Author(s):

Samar Abdalkaream Thabit ◽

Loay E. George ◽

Khalid A. Hadi

Keyword(s):

Mathematical Model ◽

Solar Activity ◽

Solar Cycle ◽

Seasonal Variations ◽

Path Length ◽

Polynomial Equation ◽

Ionospheric Parameter ◽

Solar Cycle 24 ◽

Path Lengths ◽

Cycle 24

In this research, the seasonal Optimal Reliable Frequency (ORF) variations between different transmitter/receiver stations have been determined. Mosul, Baghdad, and Basra have been chosen as tested transmitting stations that located in the northern, center, and southern of Iraqi zone. In this research, the minimum and maximum years (2009 and 2014) of solar cycle 24 have been chosen to examine the effect of solar activity on the determined seasonal ORF parameter. Mathematical model has been proposed which leads to generate the Optimal Reliable Frequency that can maintain the seasonal connection links for different path lengths and bearings. The suggested ORF parameter represented by a different orders polynomial equation. The polynomial equation has been determined depending on different selected parameters (path length, bearing, time (day), months and BUF values). The suggested seasonal ORF parameter was examined for the three stations of the adopted years. The value of the seasonal ORF ionospheric parameter increased with the increase of path length and varies with the bearing between the transmitting and receiving stations also, the seasonal ORF values were higher at maximum solar cycle (2014) than the minimum solar cycle (2009).

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Variations of Scale Height at F-Region Peak Based on Ionosonde Measurements during Solar Maximum over the Crest of Equatorial Ionization Anomaly Region

The Scientific World JOURNAL ◽

10.1155/2014/397402 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 7

Author(s):

Yu-Jung Chuo

Keyword(s):

Critical Frequency ◽

Peak Height ◽

Scale Height ◽

High Solar Activity ◽

Upward Movement ◽

Physical Processes ◽

F Region ◽

Equatorial Ionization Anomaly ◽

Anomaly Region ◽

Layer Peak

Scale height is an important parameter in characterizing the shape of the ionosphere and its physical processes. In this study, we attempt to examine and discuss the variation of scale height,Hm, around the F-layer peak height during high solar activity at the northern crest of the equatorial ionization anomaly (EIA) region.Hmexhibits day-to-day variation and seasonal variation, with a greater average daily variation during daytime in summer. Furthermore, the diurnal variation ofHmexhibits an abnormal peak at presunrise during all the seasons, particularly in winter. This increase is also observed in the F2-layer peak height for the same duration with an upward movement associated with thermospheric wind toward the equator; this upward movement increases the N2/O ratio andHm, but it causes a decrease in the F2-layer maximum critical frequency during the presunrise period.

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Analysis of Ionospheric foF2 by Solar Activity over the Korean Peninsula

International Journal of Electrical and Computer Engineering (IJECE) ◽

10.11591/ijece.v6i1.pp71-81 ◽

2016 ◽

Vol 6 (1) ◽

pp. 71

Author(s):

Min-Ho Jeon ◽

Chang-Heon Oh

Keyword(s):

Solar Activity ◽

Standard Deviation ◽

Sea Level ◽

Critical Frequency ◽

High Electron ◽

High Electron Density ◽

Layer Height ◽

Annual Variations ◽

F Region ◽

The Mean

The F2 layer is the upper sector of the ionospheric F region, and it is ~250 km above sea level. It has a high electron density and thus plays an important role in shortwave communications. The variations of the critical frequency of the F2 layer (foF2) offer clues regarding the events happening within the entire F2 layer, and foF2 analysis is essential for stable shortwave communications. This study analyzes the seasonal and annual variations of the foF2 as well as the reactions of the F2 layer height at two locations in South Korea by employing the mean and standard deviation (SD) used in previous studies. To ensure a more elaborate analysis, the median and quartiles were used for analyzing the ionosphere. We thereby compensate for the limitations of the mean and SD in developing the SD, despite the convenience of the SD for probability analysis. The application of the median and quartiles for the analysis of ionospheric data led to analysis results with greater detail. This was achieved by determining the relative SD and concurrently displaying the outliers and range of variations

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Pathways of Influence of the Northern Hemisphere Mid–high Latitudes on East Asian Climate: A Review

10.5194/egusphere-egu21-4225 ◽

2021 ◽

Author(s):

Jianping Li ◽

Fei Zheng ◽

Cheng Sun ◽

Juan Feng ◽

Jing Wang

Keyword(s):

East Asia ◽

Northern Hemisphere ◽

Synergistic Effects ◽

East Asian ◽

Antagonistic Effect ◽

The Arctic ◽

Future Research ◽

High Latitudes ◽

The North ◽

East Asian Climate

<p>This paper reviews recent progress made by Chinese scientists on the pathways of influence of the Northern Hemisphere mid&#8211;high latitudes on East Asian climate within the framework of a &#8220;coupled oceanic&#8211;atmospheric (land&#8211;atmospheric or seaice&#8211;atmospheric) bridge&#8221; and &#8220;chain coupled bridge&#8221;. Four major categories of pathways are concentrated upon, as follows: Pathway A&#8212;from North Atlantic to East Asia; Pathway B&#8212;from the North Pacific to East Asia; Pathway C&#8212;from the Arctic to East Asia; and Pathway D&#8212;the synergistic effects of the mid&#8211;high latitudes and tropics. In addition, definitions of the terms &#8220;combined effect&#8221;, &#8220;synergistic effect&#8221; and &#8220;antagonistic effect&#8221; of two or more factors of influence or processes and their criteria are introduced, so as to objectively investigate those effects in future research.</p>

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Analysis of Ionospheric foF2 by Solar Activity over the Korean Peninsula

International Journal of Electrical and Computer Engineering (IJECE) ◽

10.11591/ijece.v6i1.9344 ◽

2016 ◽

Vol 6 (1) ◽

pp. 71

Author(s):

Min-Ho Jeon ◽

Chang-Heon Oh

Keyword(s):

Solar Activity ◽

Standard Deviation ◽

Sea Level ◽

Critical Frequency ◽

High Electron ◽

High Electron Density ◽

Layer Height ◽

Annual Variations ◽

F Region ◽

The Mean

The F2 layer is the upper sector of the ionospheric F region, and it is ~250 km above sea level. It has a high electron density and thus plays an important role in shortwave communications. The variations of the critical frequency of the F2 layer (foF2) offer clues regarding the events happening within the entire F2 layer, and foF2 analysis is essential for stable shortwave communications. This study analyzes the seasonal and annual variations of the foF2 as well as the reactions of the F2 layer height at two locations in South Korea by employing the mean and standard deviation (SD) used in previous studies. To ensure a more elaborate analysis, the median and quartiles were used for analyzing the ionosphere. We thereby compensate for the limitations of the mean and SD in developing the SD, despite the convenience of the SD for probability analysis. The application of the median and quartiles for the analysis of ionospheric data led to analysis results with greater detail. This was achieved by determining the relative SD and concurrently displaying the outliers and range of variations

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Quiet-condition variations in the scale height at F2-layer peak at Jicamarca during solar minimum and maximum

Annales Geophysicae ◽

10.5194/angeo-25-2541-2007 ◽

2007 ◽

Vol 25 (12) ◽

pp. 2541-2550 ◽

Cited By ~ 31

Author(s):

C.-C. Lee ◽

B. W. Reinisch

Keyword(s):

Solar Minimum ◽

Critical Frequency ◽

Solar Maximum ◽

Peak Height ◽

Scale Height ◽

Quiet Condition ◽

Critical Frequency Fof2 ◽

Two Parameters ◽

Thickness Parameter ◽

Layer Peak

Abstract. This study is the first attempt to examine the quiet-condition variations in scale height (Hm) near the F2-layer peak in the equatorial ionosphere. The data periods of Hm derived from the Jicamarca ionograms are January-December 1996 and April 1999–March 2000. The results show that the greatest and smallest Hm values are generally at 11:00–12:00 LT and 04:00–05:00 LT, respectively. Additionally, the sunrise peak occurs at 06:00 LT only during solar minimum. The post-sunset peaks in the equinoctial and summer months are more obvious during solar maximum. The Hm difference between solar minimum and maximum are significant from afternoon to midnight. On the other hand, the Hm values during 07:00–10:00 LT for solar minimum are close to those for solar maximum. Furthermore, the correlation of Hm with the critical frequency (foF2) of F2-layer is generally low. In contrast, the correlation between Hm and the peak height (hmF2) of F2-layer is high. For Hm and the thickness parameter (B0) of F2-layer, the correlation between these two parameters is almost perfect.

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