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Sporadic E seasonal variability and descent derived from GPS- COSMIC Radio Occultation 1 Department of Physics, Chinese Culture University, Taipei, Taiwan,

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Presentation on theme: "Sporadic E seasonal variability and descent derived from GPS- COSMIC Radio Occultation 1 Department of Physics, Chinese Culture University, Taipei, Taiwan,"— Presentation transcript:

1 Sporadic E seasonal variability and descent derived from GPS- COSMIC Radio Occultation 1 Department of Physics, Chinese Culture University, Taipei, Taiwan, R.O.C. 2 Institute of Space Science, National Central University, Chung-Li, Taiwan, R.O.C. Chien-Ya Wang 1 and Yen-Hsyang Chu 2 23 June 2010 CEDAR

2 Contents: 1.Occurrence rates of sporadic E(Es) from COSMIC RO data in 3 years. 2.Vertical tidal wavelengths estimate at different latitudes from Es occurrence rate profiles. 3.Probably a case of diurnal tide in Es region detected by Chung-Li VHF radar. Motivation: Variance analyze COSMIC RO (radio occultation) in Es region data to explore the Es phenomena.

3 ► Recently, GPS radio occultations (RO) are used to study irregularities in the lower ionospheric E region [Wu et al.,2005; Arras et al.,2008]. This allows for global maps of sporadic E occurrence rates of high spatial resolution. ► If there are electron density irregularities existed in the ray path, the scintillation and multiple paths effects will disturb the received GPS signals. Thus from the analysis of these disturbed signals, Es layer can be defined. ► Statistics of COSMIC RO data from 2006 Jul.~2009 Aug. will be presented. In this report will focus on the comparing with the idealized tide wind function in different latitudes. Introduction

4 Examples of Identifying Es layer from GPS Phase/SNR Profiles R:3-point running mean B: Raw data Red points indicate the peak perturbed, for those values of L2 and two SNRs have the same height of L1 are selected. 80 km 130 km Es region SNR 0 127.8615°W 9.2593°S A high pass filter is applied to SNR1 and SNR2, then normalize with background SNR 01 and SNR 02. Two high pass filter processes are applied to L1 and L2. L1 L2 SNR1SNR2

5 Occurrence Rate of Four Seasons from 2006 Jun.-2009 Aug. Grid Resolution 5°×5° SpringSummer Fall Winter

6 Wind shear theory with diffusion and E-field are neglected Theory

7 Simulation with ideal zonal wind Fit to mid-night diurnal Fit to noontime semidiurnal Local Time (hr)

8 Summer (2006-2008) 5 N 10 N 15 N 20 N 25 N 30 N 35 N 40N 45 N 50 N 55 N 60 N

9 Winter (2006-2008) 5 S 10 S 15 S 20 S 25 S 30 S 35 S 40 S 45 S 50 S 55 S 60 S

10 Diurnal tide Vertical wavelengths estimated from ideal tidal function

11 Es exist in negative zonal wind shear convergence region 20°N spring50°N summer Wind shear contour from HWM07 model

12 May 20 May 21 May 22 May 23 May 24 RTI plots of Chung-Li 30MHz radar Es echoes at May 20-24 2008

13 Es exist in negative zonal wind shear convergence region

14 A diurnal tide ?

15 Summery: Seasons morphology of Es occurrence rates from COSMIC data show two explicit semidiurnal tides start (from midnight and noontime ) in latitude 20°~60°N. The vertical wavelengths of semidiurnal tides are varies in 20~45 km, while the diurnal tide wavelengths in law latitude(5°~15°N) are ~15 km. Sporadic E echoes exist in negative zonal wind shear region, exhibit a candidate of diurnal tide with vertical wavelength ~25km are detected by Chung-Li radar. Thank you!


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