Use of GPS Radio Occultation Data for Climate Monitoring Y.-H. Kuo, C. Rocken, and R. A. Anthes University Corporation for Atmospheric Research

GPS Occultation Basic measurement principle: Deduce atmospheric properties based on precise measurement of phase delay and amplitude.

Radio occultation for Climate

Radiosonde Stations and Manufacturers Vaisala/Australia IM-MK3/India Shang/China MEISEI/Japan Mars/MRZ VIZ AIR Others From Junhong Wang

Quantifying Regional Differences n Calculate the mean absolute difference in refractivity between CHAMP and Radiosondes (N CR ) between 5 ~ 25 km. n Calculate the corresponding mean of the absolute value of the difference in refractivity between CHAMP and the ECMWF (N CE ) n Perform calculation using radiosonde data from different regions of the world from June 2001 to March From D.Rossiter (UCAR Summer Student)

Statistics of CHAMP - Radiosonde Comparison RegionSonde Type Average # of matches IndiaIM-MK / /1.0 RussiaMars / /0.9 JapanMEISEI / /1.1 ChinaShanghai / /1.0 AustraliaVaisala / /0.9 Fractional Refractivity Differences between 5 ~ 25 km

Climate change to doubling CO2 n Perhaps the most accurate and stable global thermometer for estimating climate change n Most accurate where model- predicted temperature changes are large in upper troposphere and lower stratosphere Meehl et al. 2000, J. Climate.

GPS - NCEP/NCAR reanalysis refractivity difference at 300 mb Northern Hemisphere

GPS - ECMWF analysis refractivity difference at 300 mb Northern Hemisphere

GPS - radiosonde refractivity difference at 300 mb Northern Hemisphere

GPS - NCEP/NCAR reanalysis refractivity difference at 300 mb Southern Hemisphere

GPS - ECMWF analysis refractivity difference at 300 mb Southern Hemisphere

GPS - radiosonde refractivity difference at 300 mb Southern Hemisphere

Temperature change as detected by GPS RO 300 mb

Temperature change as detected by GPS RO 50 mb

Temperature change as detected by GPS RO 10 mb

COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) 6 Satellites launched in late 2005 Three instruments: GPS receiver, TIP, Tri-band beacon Weather + Space Weather data Global observations of: Pressure, Temperature, Humidity Refractivity Ionospheric Electron Density Ionospheric Scintillation Demonstrate quasi-operational GPS limb sounding with global coverage in near-real time Climate Monitoring

COSMIC Status

GPS radio occultation missions MissionLaunch-Duration# Soundings/dayRemarks GPS-MET4/ ~125Proof of Concept CHAMP11/2000 ~5~250Improved receiver, tracking SAC-C11/2000 ~3~500Improved receiver, open loop tracking test GRACE5/2002 ~5~500RO data not yet available COSMIC9/2005 ~ Real time-ops TerraSAR-X7/2005 ~5~400COSMIC RX & Antennas EQUARS7/2006 ~3~400COSMIC RX & CHAMP antennas METOP5/2007 ~5~500Real time - ops COSMIC II3/2009 ~ Real time-ops. Ionosphere

o: EQUARS o: COSMIC Distribution of GPS Occultation events in 24 hrs with EQUARS (2006, inclination angle<20 o ) and COSMIC (2005, 6 LEO satellites at 72 o ) EQUARS Dense data rate in equatorial region COSMIC Global coverage, but less data at low latitudes +