scholarly journals foF2 Seasonal Prediction With IRI-2016 Over Quiet Activity at Dakar Station

2021 ◽  
Vol 13 (3) ◽  
pp. 1
Author(s):  
Sibri Alphonse Sandwidi ◽  
Christian Zoundi ◽  
Doua Allain Gnabahou ◽  
Frederic Ouattara
Keyword(s):  
Winter Season ◽  
Seasonal Prediction ◽  
Solar Cycles ◽  
Iri Model ◽  
Four Seasons ◽  
Vertical Drift ◽  
Relative Standard ◽  
Model Predictions ◽  
Critical Frequency Fof2 ◽  
Autumn And Winter

This study deals with comparison between Dakar station ionospheric F2 layer critical frequency (foF2) data and both subroutines (CCIR and URSI) of IRI-2016 model predictions. Dakar station is located near the crest of the African Equatorial Ionization Anomaly (EIA) region. Comparisons are made for very quiet activity during the four seasons (spring, summer, autumn and winter) over both solar cycles 21 and 22. The quietest days per season are determined by taking the five days with the lowest aa. The relative standard deviation of modeled foF2 values is used to assess the quality of IRI model prediction. Model predictions are suitable with observed data by day than by night. The accuracy is better during spring season and poor during winter season. During all seasons, both model subroutines don’t express the signature of the observed vertical drift E×B. But they express an intense counter electrojet at the place of mean intensity or high electrojet.

scholarly journals Milk Price Comparison Between Six Years from Romania and European Union

2021 ◽  
Vol 78 (1) ◽  
pp. 57
Author(s):  
Anamaria VÂTCĂ ◽  
Anca ROTARU ◽  
Ștefania GÂDEA ◽  
Sorin VÂTCĂ ◽  
Valentina STOIAN
Keyword(s):  
European Union ◽  
National Economy ◽  
Milk Protein ◽  
Winter Season ◽  
Fat Content ◽  
The European Union ◽  
Price Comparison ◽  
Four Seasons ◽  
European Standards ◽  
Autumn And Winter

Milk price tendency is essential for the national economy and protection of milk producers. The constant need to align with European standards motivate this study to assess the interaction of milk prices in our country compared to the European Union. The objective of the study was to statistically compare the prices from Romania and UE. For a deep overview we took into consideration the quantity from Romania and most important qualitative milk parameters namely protein and fat content. The data was from 6 years from 2013 until 2018 and from all four seasons. Analysis of variance was performed together with mean comparisons between different years and seasons. Milk medium prices were higher with at least 20% in UE compared to Romania. Prices were higher in autumn and winter rather than in spring and summer proportionally with the quantity of milk. Protein and fat content was significantly higher in autumn and winter season.

scholarly journals A modeling study offoF2andhmF2parameters measured by the Arecibo incoherent scatter radar and comparison with IRI model predictions for solar cycles 21, 22, and 23

2011 ◽  
Vol 116 (A3) ◽  
Author(s):  
Christiano Garnett Marques Brum ◽  
Fabiano da Silveira Rodrigues ◽  
Pedrina Terra dos Santos ◽  
Aleshka Carrion Matta ◽  
Nestor Aponte ◽  
...  
Keyword(s):  
Solar Cycles ◽  
Incoherent Scatter Radar ◽  
Iri Model ◽  
Incoherent Scatter ◽  
Scatter Radar ◽  
Model Predictions ◽  
Modeling Study

Grass silage: A comparison of the changes involved in the ordinary, molasses and A.I.V. processes

1937 ◽  
Vol 27 (2) ◽  
pp. 151-161 ◽  
Author(s):  
W. Morley Davies ◽  
G. H. Botham ◽  
W. B. Thompson
Keyword(s):  
Winter Season ◽  
Grass Silage ◽  
Autumn And Winter

The object of this communication is to give an account of an experiment, carried through in the autumn and winter season of 1934–5, designed to determine the changes in composition involved in making silage by the ordinary, molasses and A.I.V. processes. The changes in composition included those of both crude as well as digestible nutrients.

scholarly journals Spatial and Temporal Characteristics of Precipitation in Yungui Plateau during 1961-2015

2018 ◽  
Vol 38 ◽  
pp. 01021
Author(s):  
Wu Jianfeng ◽  
Yu Luqin ◽  
Cao Guangjie ◽  
Li Wei
Keyword(s):  
Linear Trend ◽  
Point Of View ◽  
Downward Trend ◽  
Guizhou Province ◽  
Analysis Method ◽  
Four Seasons ◽  
Daily Precipitation Data ◽  
Distribution Point ◽  
Autumn And Winter ◽  
Spatial Analysis Method

In this paper, the daily precipitation data of 19 meteorological stations in Guizhou Province from 1961 to 2015 are used. Using GIS spatial analysis method and linear trend analysis method, the distribution characteristics of annual and seasonal precipitation in Guizhou province were analyzed from space and time. The results show that: (1) From the perspective of spatial distribution, annual precipitation is generally less in the south and north and less in the east and west. The precipitation in winter and spring is east-west distribution and decreases from east to west in the four seasons. The precipitation in summer is roughly north-south and south-north less. The precipitation in autumn is mainly concentrated in southwest Guizhou and Chishui valley. (2) From the time distribution point of view, the precipitation in Guizhou Province showed a general downward trend, of which the precipitation in spring, autumn and winter showed a decreasing trend, the downward trend in autumn was more obvious, and the precipitation in summer increased but not obviously.

scholarly journals IRI-2001 model predictions compared with ionospheric data observed at Brazilian low latitude stations

2006 ◽  
Vol 24 (8) ◽  
pp. 2191-2200 ◽  
Author(s):  
F. Bertoni ◽  
Y. Sahai ◽  
W. L. C. Lima ◽  
P. R. Fagundes ◽  
V. G. Pillat ◽  
...  
Keyword(s):  
Reasonable Agreement ◽  
Critical Frequency ◽  
Peak Height ◽  
Low Latitude ◽  
F Region ◽  
Model Predictions ◽  
Critical Frequency Fof2

Abstract. In this work, the F-region critical frequency (foF2) and peak height (hmF2) measured by digital ionosondes at two Brazilian low-latitude stations, namely Palmas (10.17° S, 48.20° W, dip –10.80°) and São José dos Campos (23.20° S, 45.86° W, dip –38.41°), are compared with the IRI-2001 model predictions. The comparison at the latter station shows quite a reasonable agreement for both parameters. The former station exhibits a better agreement for hmF2 than for foF2. In general, the model generates good results, although some improvements are still necessary to implement in order to obtain better simulations for equatorial ionospheric regions.

scholarly journals Performance of the IRI-2016 at the Brazilian low-latitude ionosphere over the South America Magnetic Anomaly during solar minimum

2019 ◽  
Author(s):  
Juliano Moro ◽  
Jiyao Xu ◽  
Clezio Marcos De Nardin ◽  
Laysa Cristina Araújo Resende ◽  
Régia Pereira Silva ◽  
...  
Keyword(s):  
South America ◽  
Magnetic Anomaly ◽  
Critical Frequency ◽  
Peak Height ◽  
The South ◽  
Iri Model ◽  
Radio Science ◽  
Critical Frequency Fof2 ◽  
Dip Angle ◽  
Navigation Signals

Abstract. In this work we analyse the ionograms obtained by the recent Digisonde installed in Santa Maria (29.7º S, 53.7º W, dip angle = − 37º), Brazil, to calculate the monthly averages of the F2 layer critical frequency (foF2), its peak height (hmF2), and the E-region critical frequency (foE) acquired during geomagnetically quiet days from September 2017 to August 2018. The monthly averages are compared to the 2016 version of the International Reference Ionosphere (IRI) model predictions in order to study its performance close to the center of the South America Magnetic Anomaly (SAMA), which is a region particularly important for High Frequency (HF) ground-to-satellite navigation signals. The foF2 estimated with the Consultative Committee International Radio (CCIR) and International Union of Radio Science (URSI) options predicts well throughout the year. Whereas, for hmF2, it is recommended to use the SHU-2015 option instead of the other available options (AMTB2013 and BSE-1979). The IRI-2016 model outputs for foE and the observations presented very good agreements.

scholarly journals Investigating the foF2 variations at the Ionospheric Observatory of Rome during different solar cycles minimums and levels of geomagnetic activity

2020 ◽  
Vol 10 ◽  
pp. 52
Author(s):  
Alessandro Ippolito ◽  
Loredana Perrone ◽  
Christina Plainaki ◽  
Claudio Cesaroni
Keyword(s):  
Geomagnetic Activity ◽  
Solar Minimum ◽  
Critical Frequency ◽  
Background Level ◽  
Solar Cycles ◽  
Physical Processes ◽  
Minimum Duration ◽  
Critical Frequency Fof2 ◽  
Definition Of ◽  
Low Activity

The variations of the hourly observations of the critical frequency foF2, recorded at the Ionospheric Observatory of Rome by the AIS-INGV ionosonde (geographic coordinates 41.82° N, 12.51° E; geomagnetic coordinates 41.69° N, 93.97° E) during the low activity periods at the turn of solar cycles 21–22, 22–23 and 23–24, are investigated. Deviations of foF2 greater than ± 15% with respect to a background level, and with a minimum duration of 3 h, are here considered anomalous. The dependence of these foF2 anomalies on geomagnetic activity has been accurately investigated. Particular attention has been paid to the last deep solar minimum 2007–2009, in comparison with the previous solar cycle minima. The lack of day-time anomalous negative variations in the critical frequency of the F2 layer, is one of the main findings of this work. Moreover, the analysis of the observed foF2 anomalies confirms the existence of two types of positive F2 layer disturbances, characterised by different morphologies and, different underlying physical processes. A detailed analysis of four specific cases allows the definition of possible scenarios for the explanation of the mechanisms behind the generation of the foF2 anomalies.

scholarly journals The 22-year cycle in the geomagnetic 27-day recurrences reflecting on the F2-layer ionization

2004 ◽  
Vol 22 (4) ◽  
pp. 1171-1176 ◽  
Author(s):  
E. M. Apostolov ◽  
D. Altadill ◽  
M. Todorova
Keyword(s):  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Activity Index ◽  
Solar Rotation ◽  
Rotation Period ◽  
Sunspot Cycle ◽  
Solar Cycles ◽  
Solar Radio Flux ◽  
Critical Frequency Fof2 ◽  
Northern And Southern Hemispheres

Abstract. Solar cycle variations of the amplitudes of the 27-day solar rotation period reflected in the geomagnetic activity index Ap, solar radio flux F10.7cm and critical frequency foF2 for mid-latitude ionosonde station Moscow from the maximum of sunspot cycle 18 to the maximum of cycle 23 are examined. The analysis shows that there are distinct enhancements of the 27-day amplitudes for foF2 and Ap in the late declining phase of each solar cycle while the amplitudes for F10.7cm decrease gradually, and the foF2 and Ap amplitude peaks are much larger for even-numbered solar cycles than for the odd ones. Additionally, we found the same even-high and odd-low pattern of foF2 for other mid-latitude ionosonde stations in Northern and Southern Hemispheres. This property suggests that there exists a 22-year cycle in the F2-layer variability coupled with the 22-year cycle in the 27-day recurrence of geomagnetic activity. Key words. Ionosphere (mid-latitude ionosphere; ionosphere- magnetosphere interactions) – Magnetospheric physics (solar wind-magnetosphere interactions)

scholarly journals A Sediment Diagenesis Model of Seasonal Nitrate and Ammonium Flux Spatial Variation Contributing to Eutrophication at Taihu, China

2020 ◽  
Vol 17 (11) ◽  
pp. 4158 ◽  
Author(s):  
Linda Sarpong ◽  
Yiping Li ◽  
Eyram Norgbey ◽  
Amechi S. Nwankwegu ◽  
Yue Cheng ◽  
...  
Keyword(s):  
Water Quality ◽  
Water Column ◽  
Algal Blooms ◽  
Latin Hypercube Sampling ◽  
Sediment Flux ◽  
Low Oxygen ◽  
Four Seasons ◽  
Sediment Diagenesis ◽  
Oxygen Conditions ◽  
Autumn And Winter

Algal blooms have thrived on the third-largest shallow lake in China, Taihu over the past decade. Due to the recycling of nutrients such as nitrate and ammonium, this problem has been difficult to eradicate. Sediment flux, a product of diagenesis, explains the recycling of nutrients. The objective was to simulate the seasonal spatial variations of nitrate and ammonium flux. In this paper, sediment diagenesis modeling was applied to Taihu with Environmental Fluid Dynamics Code (EFDC). Latin hypercube sampling was used to create an input file from twelve (12) nitrogen related parameters of sediment diagenesis and incorporated into the EFDC. The results were analyzed under four seasons: summer, autumn, winter, and spring. The concentration of NH4–N in the sediment–water column increased from 2.744903 to 22.38613 (g/m3). In summer, there was an accumulation of ammonium in the water column. In autumn and winter, the sediment was progressively oxidized. In spring, low-oxygen conditions intensify denitrification. This allows algal blooms to continue to thrive, creating a threat to water quality sustainability. The sediment diagenesis model, coupled with water quality measured data, showed an average relative error for Total Nitrogen (TN) of 38.137%, making the model suitable. Future studies should simulate phosphate flux and measure sediment fluxes on the lake.

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