Low ionospheric reactions on tropical depressions prior hurricanes

Significance 

The variance in complexity of both physical and chemical processes occurring in the atmosphere during a tropical depression/cyclone, directly and indirectly causes changes at different altitude domains and geographical locations. Some of these processes occur in the ionosphere and have been the epicenter of previous studies. Global positioning technology has been employed in computing the total electron content variance during high ionosphere analyses. Such atmospheric related works are of immense significance as it is known that tropical depressions have a tendency to develop into tropical cyclones or, after all, recede to the unperturbed state. This therefore instigates the question on whether there exist any indications from which we can predict the time evolutions of atmospheric parameters after depression. Unfortunately, it becomes quite difficult to answer this question since little analysis has been undertaken on the behavior of low ionosphere.

A group of Serbian researchers investigated the long term low ionosphereic perturbations that last more than the lighting induced ones during such periods. They conducted in-depth studies on the effects of time of tropical depression beginning and its geographical position with respect to considered low ionospheric part to detectability of the low ionospheric disturbances. Their work is now published in the research journal, Advances in Space Research.

The research team commenced their experiments by sending very low frequency radio signals emitted by a NAA transmitter located in the United States of America and receiving them using a similar receiver located in Serbia so as to detect around 41 tropical depressions before the registered hurricanes. For this purpose, they developed a procedure for exceeding any long-term signal amplitude deviations during the considered periods around the tropical depression beginning, over three days before the day of depression. The research team considered subsamples with regard to the recorded time of tropical depression beginning, and analyzed sudden ionospheric disturbances with respect to time period and location of tropical depression beginning.

The authors observed that for all the cases studied, 88% of them recorded low ionosphereic perturbations. They also noted that signal deviations were detected during all the three time periods of daytime, nighttime and periods when solar terminator affects medium within signal propagate and they were repeatable. The researchers also found out that deviations in signal amplitudes were detected at different times in relation to tropical depression beginning, thereby indicating a possibility of detecting sudden ionospheric disturbances as precursor of tropical depressions.

The study by Aleksandra Nina and colleagues has successfully presented the pioneering work that investigates sudden disturbances in the low ionosphere in the period around tropical depression beginning. Most important, they have revealed that responses of the low ionosphere that lasts at least several tens of minutes in the periods of several hours around tropical depression beginning for near 90% of the considered cases, tend to indicate a large possibility of connection between the troposphere and low ionosphere in the periods around tropical depression beginning. The work presented a significant step towards comprehending and predicting hurricane formations.

Low ionospheric reactions on tropical depressions prior hurricanes- Advances in Engineering

About the author

Aleksandra Nina is a research assistant professor at the Institute of Physics, University of Belgrade. She received her Ph.D (2014) in Physics from the Faculty of Physics of the University of Belgrade. She is author of many scientific papers in her main areas of interest: ionosphere, databases, electromagnetic wave propagations, natural disasters.

About the author

Milan Radovanović received PhD in Geographical sciences from Geographical Faculty (Belgrade) in 2001. Milan is representative of Serbia in international organisation Variability of the Sun and Its Terrestrial Impact (VarSITI). He is also director of the Geographical Institute Jovan Cvijic SASA. His research interests include influences of the Sun on the atmospheric processes and environment on earth, physical geography, natural hazards and tourism.

About the author

Boško Milovanović. Geographer. PhD in climatology – physical geography in 2012 at the Faculty of Geography, University of Belgrade, Serbia. Research associate at the Geographical Institute “Jovan Cvijić” Serbian Academy of Sciences and Arts. Field of investigation: climatology, regional climatology of Serbia, climate fluctuation (instrumental period), methodology of scientific research.

About the author

Andjelka B. Kovačević is associate professor and head of Department of astronomy, Faculty of mathematics University of Belgrade. The main research field is time domain astronomy and data analysis.

About the author

Jovan Bajčetić is an assistant professor at the Department of Telecommunication and Information Science in the Military Academy, University of Defence in Belgrade. He obtained his PhD degree in Electrical and Computer Engineering from the Faculty of Technical Sciences, University of Novi Sad in 2017 on the topic “Modelling of intense solar radiation change influence on radio propagation”. He has been teaching and working on different topics in the radio communication systems, radio propagation, integrated communication networks and computer networks for last ten years. His recent interest is related to the propagation of radio signals in the ionospheric D-layer during intensive ionospheric disturbances, automated system for detection, classification and near real time warning for natural and manmade ionospheric disturbances based on the radio sounding remote sensing technic.

About the author

Luka Č. Popović received his Ph.D in 1994 from Faculty of Mathematics of the University of Belgrade, Serbia. First he was working at Popular astronomical observatory and Planetarium of AS ‘Rudjer Boskovic’ (1989-1992). Since 1992 he is working at Astronomical Observatory in Belgrade. Since 2001 he is teaching PhD students of astrophysics at Faculty of Mathematics of the University of Belgrade and from 2006 BSc students of physics at Faculty of Science, University of Banja Luka. His recent interest is related to active galactic nuclei, gravitational lenses, Stark broadening, gamma ray burst and physics of ionosphere.

Reference

Aleksandra Nina, Milan Radovanovic´, Bosˇko Milovanovic´, Andjelka Kovacˇevic´, Jovan Bajcˇetic´, Luka Cˇ . Popovic. Low ionospheric reactions on tropical depressions prior hurricanes. Advances in Space Research 60 (2017) 1866–1877

 

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