COSMIC: Constellation Observing System for Meteorology, Ionosphere and Climate: Overview, Status, an

1
COSMIC Constellation Observing System for
Meteorology, Ionosphere and Climate Overview,
Status, and Results

• Bill Schreiner
• Chris Rocken, Doug Hunt, Sergey Sokolovskiy, Stig
  Syndergaard
• COSMIC Project Office
• Presentation for HIRDLS Science Team Meeting
• 29 January 2008

2
COSMIC at a Glance
3
Presentation of first results from
COSMIC/ FORMOSAT-3 to appear in Bulletin of
American Meteorological Society, March 2008
4
Characteristics of GPS RO Data

• Limb sounding geometry complementary to ground
  and space nadir viewing instruments
• Global 3-D coverage 40 km to surface
• High accuracy
• Demonstrated high precision (0.2 K between 10
  and 20 km)
• High vertical resolution (0.1 km near surface 1
  km above tropopause)
• Low horizontal resolution (200-300km)
• Only system from space to resolve atmospheric
  boundary layer
• All weather-minimally affected by aerosols,
  clouds or precipitation
• Independent height and pressure
• Requires no first guess sounding
• Independent of radiosonde calibration
• Independent of processing center
• No instrument drift
• No satellite-to-satellite bias
• Compact sensor, low power, low cost

5
Observed Atmospheric Volume
L300 km Z1 km
6
CDAAC Processing Flow
Atmospheric processing
Abel Inversion
1-D Var Moisture Correction
LEO data
Level 0--level 1
Excess Phase
Orbits and clocks
Fiducial data
Real time Task Scheduling Software
Profiles
Ionospheric processing
Combination with other data
Excess Phase
Abel Inversion
7
RO Retrieval Processing Flow
Input (phase,amplitude, LEO/GPS position and
velocity)
(Kuo et al., 2004)
6) Calculation of the bending angle from L1 raw
complex signal, FSI
1a) Open-Loop Data Processing NDM Removal, Phase
connection
7) Combining (sewing) (5) and (6) L1 bending
angle profiles
1) Detection of L1 PLL tracking errors
and truncation of the signal
8) Ionospheric calibration of the bending angle
2) Filtering of raw L1 L2 Doppler
9) Optimal estimation of the bending angle
3) Estimation of the occultation point
4) Transfer of the reference frame to the local
center of Earths curvature
10) Abel inversion
11) Retrieval of P,T
5) Calculation of L1 and L2 bending angles from
the filtered Doppler
Output
8
Optimization of the observation bending angle
The magnitude of the residual noise can be very
different for different occultations, but it
almost does not depend on height for a given
occultation. Above a certain height, climatology
provides better estimate of the atmospheric state
than RO observation. The observed bending
angle is optimally weighted with climatology.
This does not improve the value of the
bending angle at large heights, but results in
reduction of error propagation downward after
the Abel inversion.
where
The weighting function is calculated individually
for each occultation.
9
Current Constellation Jan 1, 2008
10
Over 2 Million Profiles 4/21/06-12/31/07
Neutral Atmosphere
Ionosphere
11
Friday Dec 7, 2007Global coverage in all
weather1878 soundings
12
A typical RO sounding showing very sharp
tropopause. No other instrument from space
provides such high vertical resolution.
13
Penetration of setting/rising soundingsWithin 1
km of surface 70 tropics 90 extratropics
14
Global Distribution and Height of ABLon a single
day
Sokolovskiy et al., GRL 2007
15
COSMIC Collocated Occultations
Occultation map of atmPhs.C003.2006.157.04.30.G13.
0001.0001.nc
Occultation map of atmPhs.C002.2006.157.04.30.G13.
0001.0001.nc
16
Statistics of Collocated Soundings

• Setting Occultations with Firmware v4.2
• Tangent Point separations
• Same QC for all retrievals
• One outlier removed
• Near real-time products used

(2006.111-277)
FM3-FM4 (2006.111-300)
ALL Collocated pairs Pairs with similar
straight-line tracking depths

Schreiner, W.S., C. Rocken, S. Sokolovskiy, S.
Syndergaard, and D. Hunt, Estimates of the
precision of GPS radio occultations from the
COSMIC/FORMOSAT-3 mission, GRL, 2007
17
NCEP Impact study with COSMIC

• 500 hPa geopotential heights anomaly correlation
  (the higher the better) as a function of forecast
  day for two different experiments
• PRYnc (assimilation of operational obs ),
• PRYc (PRYnc COSMIC)
• Assimilated 1,000 COSMIC profiles per day
• Assimilated operationally at NCEP 1 May 2007
• Assimilating refractivities from rising and
  setting occultations at all levels (including low
  level), provided they pass QC
• Results with COSMIC very encouraging
• Lidia Cucurull, JCSDA

18
COSMIC data to calibrate AMSU on NOAA satellites
19
Main Results So Far from COSMIC

• General
• High accuracy, precision and vertical resolution
  demonstrated
• Inexpensive, all weather, globally distributed
  soundings
• 664 registered users from 42 countries as of
  1/1/08
• Free and open data policy
• Only space system to give information on
  ionosphere, stratosphere and troposphere
• Weather analysis and prediction
• 80 observations available within 3 hr
• Significant positive impact on skill scores of
  operational NWP
• Large impact in individual forecasts (e.g.
  Hurricane Ernesto 2006)
• Unbiased, good anchor for radiance assimilation
• Observations of tropical boundary layer from
  space for 1st time

20
COSMIC Data Access
664 users have registered (1 Jan 2008)

• http//www.cosmic.ucar.edu
• Select the 'Sign Up ' link under
• COSMIC
• Accept data use agreement
• E-mail will be sent within 2-3
• business days to indicate
• access has been granted
• N, P, T, wv profiles in NetCDF format
• On-line SQL database, analysis tools and data
  download
• Available on LDM

21
References
R. A. Anthes, P. A. Bernhardt, Y. Chen, L.
Cucurull, K. F. Dymond, D. Ector, S. B. Healy,
S.-P. Ho, D. C. Hunt, Y.-H. Kuo, H. Liu, K.
Manning, C. McCormick, T. K. Meehan, W. J.
Randel, C. Rocken, W. S. Schreiner, S. V.
Sokolovskiy, S. Syndergaard, D. C. Thompson, K.
E. Trenberth, T.-K. Wee, N. L. Yen, and Z. Zeng
(2007) The COSMIC/FORMOSAT-3 Mission Early
Results, submitted to BAMS, 2007. Kuo, Y.-H.,
T.-K. Wee, S. Sokolovskiy, C. Rocken, W.
Schreiner, D. Hunt, and R. A. Anthes, 2004
Inversion and error estimation of GPS radio
occultation data, J. Meteor. Soc. Japan, 82, 1B,
507-531. Schreiner, W., C. Rocken, S.
Sokolovskiy, S. Syndergaard and D. Hunt, 2007
Estimates of the precision of GPS radio
occultations from the COSMIC/FORMOSAT-3 mission.
Geophys. Res. Lett., 34, L04808,
doi10.1029/2006GL027557. Sokolovskiy, S., 2001
Tracking tropospheric radio occultation signals
from low Earth orbit. Radio Sci., 36(3),
483-498.