Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 The Ionosphere as Signal and Noise in Radio Occultation Christian Rocken, Sergey Sokolovskiy, Bill Schreiner, Doug Hunt, Stig Syndergard, Karl Hudnut UCAR COSMIC Project

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Radio Occultation Ionosphere as signal Ionosphere is noise

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 TEC EDP SCINTILLATION km and Plasmasphere IMPERFECT IONOSPHERIC CORRECTION ( km ) LOW QUALITY L2 OBSERVATONS (< 20 km ) Ionospheric Observations and Noise

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008

COSMIC trans- ionospheric radio links for a 100-min period, June 29, 2007 Amount of COSMIC-observed Trans Ionospheric TEC Data Quality of abs. TEC ~2 TECU

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Current Latency of COSMIC TEC Data Location of Low-Latency TEC Arcs Most data are downloaded from Satellites < 100 m Processing at CDAAC takes ~ 20 minutes

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008

COSMIC - Ionosonde Comparison Jan. 2008, distance < 500 km, time difference < 15 min, colors indicate ionosondes HMF2 rms=57 km F0F2 rms=0.60 MHz

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008

Scintillation Sensing with COSMIC No scintillation S4=0.005 Scintillation S4=0.113 GPS/MET SNR data

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Global Scintillation Mapping with COSMIC S4 Index Maximum between km

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Amplitude scintillations (S4 index based on 50-Hz observations) E-Layer scintillation: Occurs at all local times except near sun-rise (3-7 LT), strongest near sun- set (14-19 LT). Most active between deg north and south latitude More pronounced in NH than SH Stronger S4 than F-layer scintillation

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 F-Layer scintillation: Occurs sunset to sunrise ( LT). Most active in equatorial region (+/- 30 degrees). Weaker S4 than E-layer scintillation Amplitude scintillations (S4 index based on 50-Hz observations)

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Ionospheric Calibration We estimate systematic ionospheric error by computing the “mean of the iono-free bending angle minus neutral bending angle (from climatology) in the km height bin”. We compare this quantity “smean” for daytime vs. nighttime soundings. COSMIC Days 0-120, < Lat. < 20 DAY (11<LT<15) smean= e-7 rad NIGHT (2<LT<6) smean=-0.37e-7 rad We can see the day vs. night iono bias change we expect that we can monitor the change of this bias with the 11-year solar cycle.

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 CHANGE OF 10.7 CM FLUX WITH SOLAR CYCLE

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Relationship of F10.7 / Bending Bias/ Temperature F10.7 BA Bias CHANGE IN DAYTIME BENDING ANGLE BIAS IN 6 YEARS IS ~ 0.3 microrad !

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 HEIGHT [KM]TEMPERATURE ERROR [DEG K] Apparent Stratospheric Temperature Change Due to Ionosphere - Induced Bending Angle Bias of 0.3 microradians But we can correct for this error and effectively eliminate it !

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Linear Regression of BA Bias F10.7 Flux

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Ionospheric Correction In the Lower Troposphere Meehan et al. 2008

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Effect of Using L2 data to Different Penetration Depths

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008 Effect of Using L2 data to Different Penetration Depths

Formosat3/COSMIC Workshop, Taipei, Oct. 1-3, 2008

Summary In the 2 years since launch COSMIC has generated and distributed over 1.3 million ionospheric profiles and TEC arcs COSMIC ionospheric observations are of high quality and most products are available within < 120 minutes of on-orbit collection, About 300 TEC Arcs / day are available within < 30 minutes COSMIC is now also generating a large amount of scintillation observations - available from CDAAC We can see a clear correlation between F10.7 parameter and RO bending angle bias - Ionospheric bias correction of RO climate products seems feasible We do not see any evidence that availability of L2C data in in lower troposphere introduces a bias - some improvement in RMS can be expected when we start using L2C and extend ionospheric correction lower