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 Vaisala/Australia

IM-MK3/IndiaIM-MK3/India Shang/China Shang/China MEISEI/JapanMEISEI/Japan

Mars/MRZ Mars/MRZ VIZVIZ AIR AIR

OthersOthers

From Junhong Wang

Quantifying Regional Differences

Calculate the mean absolute difference in refractivity between CHAMP and Radiosondes (NCR) between 5 ~ 25 km.

Calculate the corresponding mean of the absolute value of the difference in refractivity between CHAMP and the ECMWF (NCE)

Perform calculation using radiosonde data from different regions of the world from June 2001 to March 2004.

From D.Rossiter (UCAR Summer Student)

Statistics of CHAMP - Radiosonde Comparison

RegionSonde Type

Average # of matches

India IM-MK3 87 0.82/3.2 0.15/1.0

Russia Mars 1003 0.30/1.3 0.09/0.9

Japan MEISEI 107 0.26/1.7 0.14/1.1

China Shanghai 402 0.19/1.4 0.15/1.0

Australia Vaisala 366 0.18/1.3 0.13/0.9

€

NCR /S.D.

(%)

€

NCE /S.D.

(%)

Fractional Refractivity Differences between 5 ~ 25 km

Climate change to doubling CO2 Perhaps the most accurate

and stable global thermometer for estimating climate change

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, HumidityRefractivityIonospheric Electron DensityIonospheric Scintillation

Demonstrate quasi-operational GPS limb sounding with global coverage in near-real time

Climate Monitoring

COSMIC Status

GPS radio occultation missionsMission Launch-Duration # Soundings/day Remarks

GPS-MET 4/1995 2+ ~125 Proof of Concept

CHAMP 11/2000 ~5 ~250 Improved receiver, tracking

SAC-C 11/2000 ~3 ~500 Improved receiver, open loop tracking test

GRACE 5/2002 ~5 ~500 RO data not yet available

COSMIC 9/2005 ~5 2500 - 3000 Real time-ops

TerraSAR-X 7/2005 ~5 ~400 COSMIC RX & Antennas

EQUARS 7/2006 ~3 ~400 COSMIC RX & CHAMP antennas

METOP 5/2007 ~5 ~500 Real time - ops

COSMIC II 3/2009 ~5 2500 - 3000 Real time-ops. Ionosphere

o: EQUARSo: COSMIC

Distribution of GPS Occultation events in 24 hrs with EQUARS (2006, inclination angle<20o) and COSMIC (2005, 6 LEO satellites at 72o)

EQUARS

Dense data rate in equatorial region

COSMIC

Global coverage, but less data at low latitudes

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