2016 URSI Asia-Pacific Radio Science Conference August 21-25, 2016 / Seoul, Korea HemisphericMeasurement and and annual Analysis asymmtry of Weather of NmF2 Phenomena observed by FORMOSAT-3/COSMICwith K-Band Rain RadioRadar occultation observations Jun-Hyeong Park Ki-Bok Kong Seong-Ook Park Dept. of Electrical Engineering Development1* team 1 Dept. of Electrical Engineering KAIST V. Sai GowtamKukdong ,Telecom S. Tulasi Ram KAIST DaeJeon, Republic of Korea 1IndianNonsan, institute Republic of geomagnetism, of Korea DaeJeon, Republic of Korea [email protected] [email protected] Panvel, [email protected] Navi Mumbai, India. Abstract——To the overcome average NmF2 blind valuesspots inof Decemberan ordinary solstice weather are 0.9wall83 exists AU for between December the andtransmitter 1.017 AU (Tx) for June).and receiver But varying (Rx) significantlyradar which higherscans thanhorizontally those at atJune a highsolstice altitude, at all longitudes.a weather Sunantennas – Earth to improvedistance isolationcan explain between only them.25% ofWith the thesetotal Thisradar is which known operates as F2 - layervertically, annual so asymmetry.called an atmospheric This phenomenon profiler, observedmethods, leakageasymmetry. power betweenLei et Txal. and(2013) Rx could found be reduced.similar wasis needed. observed In thisand paper,reported a K-bandseveral decadesradar for ago observing but the possiblerainfall asymmetryFig. 1 shows inmanufactured thermospheric antennas neutral and thedensity separation and wall. they mechanismsvertically is introduced,are not clearly and understood. measurement In thisresults present of rainfall study, are by attributed this to the varying Sun – Earth distance. But, using the rich data set of Constellation Observing System for shown and discussed. For better performance of the atmospheric ionosphericB. Design of behavio Tranceiverurr is different from the thermosphere Meteprofiler,orology, the radarIonosphere which and has Climate high resolution(COSMIC) even GPS with – Radio low because of its complex electrodynamics and transport Fig. 2 shows a block diagram of the K-band rain radar. occultationtransmitted powerobservations, is designed. we With investigated this radar, thea melting hemispheric layer is processes involved. Zeng et al. [2008] found significant asymmetry of equatorial ionization anomaly and its local time Reference signals for all PLLs in the system and clock signals detected and some results that show characteristics of the meting longitudinal variations in the asymmetry values. Their case and seasonal variations from 5 years data during ascending for every digital chip in baseband are generated by four layer are measured well. controlled simulation indicate that the solstice difference of phase of the solar cycle 24. Important findings from our study frequency synthesizers. In the Tx baseband module, a field Sun-Earth distance, offset between geomagnetic and are,Keywords—K-band; (i) during solstices, theFMCW; EIA crest rain in theradar; winter low hemisphere transmitted is programmable gate array (FPGA) controls a direct digital geographic center and the tilt of geomagnetic pole will play strongerpower; high than resolution; that in the rainfall; summer melting hemisphere layer from morning to synthesizer (DDS) to generate an FMCW signal which important roles on the annual asymmetry, however, the noon hours. In contrast to this, the EIA crest in the summer decreases with time (down-chirp) and has a center frequency detailed physical mechanisms of how the geomagnetic hemisphere becomes stronger and this transition occurs around of 670 MHz. The sweep bandwidth is 50 MHz which gives the I. INTRODUCTION configurations effects the annual asymmetry were still noon time, (ii) the December solstice exhibits a much pronounced high range resolution of 3 m. Considering the cost, 2.4 GHz ionizationA weather in both hemispheresradar usually and enhancedmeasures EIA meteorological than the June unexplained. There were no detailed studiessignal used on aseffects a reference of thermospheric clock input ofneu thetral DDS winds is split on andthe solsticesconditions at ofall over the a longitudinalwide area at sectors, a high altitude.(3) this Becauselocal time it used for a local oscillator (LO). the FMCW signal is dependency of hemispheric asymmetry and annual asymmetry annual asymmetry. Hence, the main objective of this paper is observes weather phenomena in the area, it is mainly used for transmitted toward raindrops with the power of only 100 mW. has been consistently observed throughout the ascending phase of to study the local time, longitudinal and solar activity weather forecasting. However, blind spots exist because an Beat frequency which has data of the range and the radial theordinary solar cycleweather 24 and radar possible scans mechanism horizontally, are in whichvestigated. results Based in variations of annual asymmetry and its responsible neutral and on our detailed analysis, location of subsolar point, offset between electrodynamicvelocity of raindrops mechanisms. is carried by 60 MHz and applied to the difficulties in obtaining information on rainfall at higher and input of the Rx baseband module. In the Rx baseband module, geographiclower altitudes and geomagneticthan the specific equator altitude. and the Therefore, declination a weatherangle of magnetic field are playing important roles in the annual quadrature demodulationII. DATA is ANDperformed RESULTS by a digital down radar that covers the blind spots is required. converter (DDC). Thus, detectable range can be doubled than asymmetry. FORMOSAT–3/COSMIC is a constellation of 6 satellites, A weather radar that scans vertically could solve the usual. Two Dimensional-Fast Fourier Transform (2D-FFT) is primarily dedicated to GPS radio occultation experiment to Keywords:problem. This Annual kind Asymmetry; of weather radar,Thermospheric so called anWinds; atmospheric GPS – performed by two FPGAs. Because the 2D FFT is performed study the Earth’s atmosphere and ionosphere. To study the profiler, pointsRadio towardsOccultation the sky and observes meteorological with 1024 beat signals, the radar can have high resolution of annual asymmetry, we used NmF2 data from the vertical conditions according to the height [1]. Also, because the the radial velocity. Finally, data of raindrops are transferred to electron density profiles provided by UCAR atmospheric profiler I.usually INTRODUCTION operates continuously at a fixed a PC with local LAN via the an UDP protocol. TABLE I. (http://www.cosmic.cdar.edu). A 41-day period that cantered position,Globally, it could the catchhemispheric the sudden averaged change NmF2of weather values in thein shows main specification of the system. on June 21 and December 21 is used to represent the solstices Decemberspecific area. solstice are significantly higher than those of June and December, respectively, from 2008 to 2012. at June solstice at all longitudes. Four types of anomalies, Solstice differences of 41-day mean F10.7 values equatorialIn this paper,ionization K-band anomaly, rain radar winter which or hasseasonal low transmitted anomaly, from 2008 to 2012 are -0.9405, 3.6317, 6.6449, 39.4982 and semiannualpower and highanomaly resolutions and ofannual the range anomaly and the orvelocity annual is 22.897 respectively (+ve means December is more). asymmetry,introduced. areThe often frequency found in modulatedthe F2 layer. continuous Apart from wave the (FMCW) technique is used to achieve high sensitivity and above four anomalies, recently Liu et al. (2009) and Chen et Fig. 1 shows the local time and latitudinal variation of the reduce the cost of the system. In addition, meteorological al. (2010) reported two different anomalies. Those are zonally averaged NmF2 and asymmetry index. During the results are discussed. Reflectivity, a fall speed of raindrops Weddell Sea Anomaly (WSA) and Mid-latitude summer solstices, EIA crest in the winter hemisphere is stronger than and Doppler spectrum measured when it rained are described, night-time anomaly (MSNA). All the above anomalies are the summer hemisphere during the morning to noon. and characteristics of the melting layer are analyzed as well. well understood except annual anomaly. Few studies on However, around noon to early afternoon hours, the EIA crest annual asymmetry can be found in the literature [Yonezawa, in summer hemisphere become stronger than the winter EIA 1971;II. SuD EVELOPMENTet al., 1998; OFRishbeth K-BAND and RAIN Muller RADAR Wodarg, SYSTEM 2006; crests and higher electron density in summer hemisphere is Mendillo et al., 2005, Liu et al., 2007, Zhen Zeng et al., 2008]. maintained throughout the afternoon to midnight. This distinct AllA. Antennathe above studies show that the asymmetry has significant hemispheric behaviour is consistently observed throughout the localTo time,suppress longitudinal side-lobe levelsand solarand increase cycle anvariations. antenna gain,One ascendingFig. 1. Manufactured phase of antenna SC 24and seinpdicatingaration wall. that this feature is pooffsetssible dual mechanism reflector isantennas the varying are usedSun- E[2].arth Also, distance separation (about independent of solar flux changes. The transition of strong 961 Fig. 1: Local time and latitudinal variations of the zonally averages NmF2 during June and December solstices (left and middle panels) and the Asymmetry Index (AI) (right panel) from 2008 to 2012. Solid black lines in right panels indicate the contour line corresponding