Colloquium On Atmospheric Remote Sensing Using The Global Positioning System

June 20 - July 2, 2004


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Sunday, 20 June 2004
5:00 - 6:30 Welcome Reception at CU
Haven Room in Darley Commons - Williams Village Dormitory, Colorado University
Monday, 21 June, 2004 (Introduction to GPS)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to FL2
8:30 - 8:45 Welcome Remarks
Tom Bogdan (ASP Director)
Tina Yang (Director, TECRO in Houston)
8:45 - 10:15 Introduction to GPS / GNSS in Atmospheric Sensing (#1)
Tom Yunck, JPL
(1) Brief description of GPS / GNSS Systems + Some History
(2) Science applications of GPS/GNSS overview
(3) Why suitable for atmospheric sensing - some history
10:15 - 10:45 Break / Informal Discussion - FL2 Cafeteria Atrium
10:45 - 12:15 The Physics of Atmospheric Microwave Propagation (#2)
Sergey Sokolovskiy, UCAR
(1) Atmospheric refractivity
(2) Geometric optics and its applicability
(3) Deriving ray equations from Fermat principle
(4) Spherically symmetric atmosphere, Snell's law
(5) Propagation effects: phase delay, ray bending, focusing/defocusing effect on amplitude, their typical magnitude and examples in the Earth's atmosphere
12:15 - 1:15 Lunch
1:15 - 2:45 Description of GPS Signal Structure & How receivers work (#3)
Larry Young, JPL
(1) L1, L2, P1, P2, C/A, Ycode modulations, wavelengths, codes
(2) Receiver description
(3) Rinex data file description and explanation / Examples
2:45 Bus Departs from FL2 to NCAR Mesa Laboratory
3:15 Welcome by Tim Killeen (NCAR Director) and group photo
3:35 - 4:30 Tour of Mesa Laboratory
4:45 Bus Departs from Mesa Laboratory to CU dormitory
Tuesday, 22 June, 2004 (Ground-based meteorology)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to FL2
8:30 - 10:00 The GPS / GNSS Observation equation and data processing (#4)
M. Rothacher, University of Munich, Germany
(1) The observation equations / Zero/single/double differences
(2) Ambiguities/Data inversion/Parameter Estimation (LSQ, Kalman filter)
(3) GPS analysis software - what does it do?
10:00 - 10:30 Break / Informal Discussion - FL2 Cafeteria Atrium
10:30 - 12:00 Ground based Meteorology / Parameter Estimation / results (#5)
Christian Rocken, UCAR
(1) Wet delay / Dry Delay / Mapping functions
(2) Estimation of tropospheric parameters - error sources
(3) Ground based networks / Validation / Example results
12:00 - 1:00 Lunch
1:00 - 2:30 New developments in Ground-based meteorology (#6)
John Braun, UCAR
(Slant Delays / assumptions and errors
Tomography and 3-D moisture retrieval
Validation / example results
2:30 - 3:00 Break / Informal Discussion - FL2 Cafeteria Atrium
3:00 - 5:00 Ground-based Seminar Presentations (#7)
Ted Iwabutchi, UCAR, MRI - Geonet (#7a)
Natalya Nicholson, Univ. Calgary, Alberta - Southern Alberta GPS Network (#7b)
Victoria Hoyle, Univ. Calgary, Alberta - Retrieval of Atmospheric Water Vapor in Southern Alberta (#7c)
Randolph Ware, UCAR - SuomiNet (#7d)
Discussion
5:00 - 5:05 Bus Departs from FL2 to Flagstaff Picnic Area
5:30 - 7:00 Picnic
7:15 Bus Departs Flagstaff to CU Williams Village Dormitory
Wednesday, 23 June, 2004 (Ground-based ionosphere)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to FL2
8:30 - 10:00 Ionosphere and Ionospheric delay (#8)
Tony Mannucci, JPL
(1) Intro to the Ionosphere, E, F2 layers basic physics
(2) Dispersive delay / ionospheric refractivity / higher order effects
(3) Measuring TEC absolute and relative / Errors
10:00 - 10:30 Break / Informal Discussion - FL2 Cafeteria Atrium
10:30 - 12:00 GPS Ionospheric Monitoring, GIMs (#9)
Manuel Hernandez-Pajares Technical University of Catalonia, Spain
(1) Thin-shell model, local model global model
(2) L4 linear combination, parameter estimation
(3) Result examples, Errors / Quality
12:00 - 1:00 Lunch
1:00 - 2:30 Ionospheric Scintillation and GPS (#10)
Keith M. Groves, Hanscom Air Force Base
(1) Scintialltion - what is it? What causes it? why does it matter?
(2) Measurement of Scintillation S4 / ROTI etc.
(3) Effect of scintillation on GPS - problems / solutions /examples
2:30 - 3:00 Break / Informal Discussion - FL2 Cafeteria Atrium
3:00 - 4:30 Mountaintop and airborne GPS observations, and effects of turbulence on RO signals (#11):
Aoyama: Mountaintop GPS observations (#11a)
Speaker (TBD): Airborne GPS observations (#11b)
Larry Cornman, NCAR : The Effect of Turbulence on GPS Signals: Theory and Measurements(#11c)
4:30 - 5:00 Discussions - Bus Departs FL2 to CU Williams Village Dormitory

Thursday, 24 June, 2004 (Radio Occultation I)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to FL2
8:30 - 10:00 Introduction to Radio Occultation sounding (#12)
E. Rob Kursinski, U. of Arizona
(1) Overview of the main steps in processing RO signals.
(2) Calculation of the bending angles from Doppler.
(3) Abel inversion.
(4) Characteristics of RO sounding: vertical and horizontal resolution.
(5) Outline of the main difficulties of RO soundings (residual ionospheric noise, multipath.)
10:00 - 10:30 Break / Informal Discussion - FL2 Cafeteria Atrium
10:30 - 11:00 Extraction of the Atmospheric Excess Phase for RO Processing (#13a)
Chris Rocken and Bill Schreiner, UCAR
(1) Solving for satellite orbits and clocks.
(2) The use of ground receivers and reference satellites.
(3) Single vs. double differencing.
(4) Noise reduction by applying modified ionospheric calibration for reference link.
11:15 - 12:00 Precise Orbit Determination for Low Earth Orbiters (#13b)
M. Rothacher, University of Munich, Germany
(1) Differences between a ground station and a LEO
(2) GPS Observation Equation for a LEO
(3) Dynamic and Kinematic Orbit Representation
(4) Zero-, Double- and Triple-Difference POD Approach
(5) Accuracy of CHAMP Orbits
(6) Accuracy of CHAMP Velocities
12:00 - 1:00 Lunch
1:00 - 2:30 Acquisition of the tropospheric RO signals (#14)
Sergey Sokolovskiy, UCAR
(1) Modeling of the tropospheric RO signals.
(2) Structure of the tropospheric RO signals and their visualization by sliding spectrograms.
(3) Principles of the open loop tracking of RO signals.
(4) Post-processing of the acquired RO signals: correction of the mean frequency, upsampling, extraction of the phase and amplitude.
2:30 - 3:00 Discussions
3:00 - 4:00 Radio-holographic inversions of the tropospheric RO signals (#15)
Sergey Sokolovskiy, UCAR
(1) Back propagation method.
(2) Radio-optics (the sliding spectral) methods.
(3) Methods utilizing transformation of the complex wave function to impact parameter representation (canonical transform, full spectrum inversion).
4:00 - 4:30 GEOS: a 3rd generation of RO science?
Peter Milne, NSF
4:30 - 5:00 Discussions
5:15 Bus Departs from FL2 to CU Williams Village Dormitory
Friday, 25 June, 2004 (Radio Occultation II)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to FL2
8:30 - 10:00 Ionospheric calibration of RO signals (#16)
Stig Syndergaard, UCAR
(1) Calibration of the phases and the bending angles.
(2) Ionospheric calibration in case of very noisy L2.
(3) Ionospheric calibration in the lower troposphere.
(4) Higher-order effects, model-dependent ionospheric calibration.
10:00 - 10:30 Break / Informal Discussion
10:30 - 12:00 The use of ancillary data (climatology) the upper stratosphere for noise reduction of RO inversions (#17)
Sean Healy, ECMWF
(1) A dominant source of noise in RO observables in the upper stratosphere. Downward error propagation after the Abel inversion.
(2) Initialization of the Abel inversion by replacing the observables for the 1st guess (climatology) above some altitude. An optimal choice of the altitude.
(3) Optimization of the obsertvational bending angles (mixing with the 1st guess according to estimated errors).
(4) Individual estimation of noise for each occultation.
(5) Account for the finite vertical error correlation of the observational bending angles and the 1st guess.
12:00 - 1:00 Lunch
1:00 - 2:30 Challenge of RO in the PBL (#18)
Sergey Sokolovskiy, UCAR
(1) The structure of the moist PBL.
(2) Superrefraction in geometric optics.
(3) Inapplicability of the Abel inversion in case of the superrefraction.
(4) Effect of the superrefraction on RO inversions.
(5) Probability of the superrefraction in different regions over tropic ocean.
(6) Superrefraction in radio-holographic inversions.
(7) Effect of small-scale refractivity irregularities on radio-holographic inversions.
(8) Parameters of RO signals that indicate high probability of the superrefraction.
2:30 - 3:00 Break & Discussions
3:00 - 5:00 COSMIC Data Analysis and Archive Center (CDAAC) demonstration and exercise (#20)
Doug Hunt and Bill Schreiner, UCAR


(Note: The original lecture planned for #19 is cancelled)
5:15 Bus Departs from FL2 to CU Williams Village Dormitory
Saturday, 26 June 2004
Tour the Rocky Mountain National Park (Bus arrives Williams Village at 7:45 a.m. and departs Williams Village Dorms at 8:00 a.m.
Monday, 28 June, 2004 (RO Results)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to FL2
8:30 - 10:00 Error characterization of RO (#21)
E. Rob Kursinski, U. of Arizona
(1) Classification of the observational errors: measurement errors; and representativeness errors.
(2) Main error sources: residual ionospheric noise at high altitudes; turbulence at mid and low altitudes; superrefraction in the lower troposphere.
(3) Different approaches for error charcterization: theoretical, based on some parameters of RO signal (allows individual characterization of each occultation); empirical, based on comparison to ancillary data; empirical, based on comparison of close occultations.
(4) Summary of the magnitude and altitude ranges for different types of errors.
10:00 - 10:30 Break / Informal Discussion
10:30 - 12:00 Ionospheric observations from RO (#22)
Paul Straus, The Aerospace Corporation
(1) Uncalibrated and calibrated TEC. Calibration of TEC by use of pseudo-range data. Calibration of TEC by use of the ascending and descending parts of orbit.
(2) Abel inversion of TEC below LEO orbit. Use of single- and dual-frequency data. Advantages and shortcomings of both approaches. Demonstration of results.
(3) Overview of constrained inversions (demonstration of results). Overview of 3-D tomography, assimilation of TEC by dynamic ionospheric models.
(4) Overview of correlative ionospheric data used for comparisons to GPS RO inversions (ionosondes, incoherent scatter radars, etc.)
(5) Ionospheric scintillation. Its characterization. Localization of the regions with ionospheric irregularities by multiple occultations with crossed lines of sight and by back propagation of the complex RO signals from single occultations.
12:00 - 1:00 Lunch
1:00 - 2:30 GPS RO Missions: Overview and Results from CHAMP, GPS/MET and SAC-C (#23)
Jens Wickert, GFZ, Postdam, Germany
(1) Overview: GPS RO mission
(2) In more detail: GPS/MET & SAC-C (selected results)
(3) CHAMP: The mission
(4) CHAMP: Overview of results
2:30 - 3:00 Discussions
3:00 - 4:30 Water vapor monitoring with RO (#24)
E. Rob Kursinski, U. of Arizona
(1) Ambiguity of interpretation of the retrieved refractivity in the presence of water vapor. The use of ancillary data for resolving the ambiguity. 1-D VAR.
(2) Overview of GPS RO water vapor retrievals. Comparison to ancillary data (NWP models, radiosondes, etc.)
(3) Independent retrievals of water vapor by use of additional frequencies near the absorption lines (X-link technology). Requirements for the accuracy of amplitude measurements.
(4) Problems of the standard GPS RO and the X-link techniques in the lower troposphere. Demonstration of results of numerical simulations of the X-link technique.
4:30 - 5:00 CDAAC Exercise (#20b)
Doug Hunt, UCAR
5:15 Bus Departs from FL2 to CU Williams Village Dormitory
Tuesday, 29 June, 2004 (Science Applications)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to FL2
8:30 - 10:00 Climate Monitoring and RO (#25)
Stephen Leroy, Harvard University
(1) Issues of assessing climate change based on observations or global analyses
(2) Projection of climate changes based on global climate models
(3) Climate changes signals as detected by the GPS RO data
(4) Issues and topics for future research
10:00 - 10:30 Break / Informal Discussion
10:30 - 12:00 Complementary Radiometric Observations (#26)
John Dykema, Harvard University
(1) Explain TOVS, AIRS etc.
(2) What is the true information from AIRS vs from GPS RO - importance of 1st guess
(3) Discuss strengths and weaknesses of Radiometer data
(4) Discuss how RO + nadir viewing data can be complementary
12:00 - 1:00 Lunch
1:00 - 2:30 Radio Occultation and the Tropopause (#27)
William Randel, NCAR
(1) Transport of moisture through tropopause
(2) Diagnosis of tropopause variations based on GPS RO data
(3) Analysis of QBO based on GPS RO data
(4) Potential future applications of GPS RO data
2:30 - 3:00 Discussions
3:00 - 4:30 GPS reflections for oceanography, ice and surface hydrology (#28)
Cinzia Zuffada, JPL
(1) The concept of GPS reflected signals, bistatic radar geometry
(2) GPS reflections from ocean
- incoherent scattering
- surface roughness characterization
- ocean altimetry
- GPS reflections mission concept
(3) GPS reflections from land
- relationship to soil moisture
(4) GPS reflections from ice
- relationship to ice thickness
- ice altimetry
4:30 - 5:00 Discussions
5:15 Bus Departs from FL2 to CU Williams Village Dormitory
Wednesday, 30 June, 2004 (Data Assimilation)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to FL2
8:30 - 10:00 Overview of Atmospheric Data Assimilation (#29)
Chris Snyder, NCAR
(1) Estimation theory
(2) Different approaches to data assimilation (3DVAR, 4DVAR, EnKF)
(3) Factors affecting the performance of atmospheric data assimilation (e.g., observation error statistics, background error statistics, observation operators, model errors, …etc)
10:00 - 10:30 Break / Informal Discussion
10:30 - 12:00 Assimilation and Impact of Ground Based Observations (#30)
Lidia Cucurull, UCAR/NCEP
(1) Issues related to the assimilation of ground based GPS data
(2) Different choices of observation operators (total zenith delay, slant delay, slant water vapor, precipitable water, …etc)
(3) Variational assimilation of ground-based GPS data and other auxiliary data
(4) Impact on precipitation forecasts
12:00 - 1:00 Lunch
1:00 - 2:30 Assimilation and Impact of RO Observations (#31)
Bill Kuo, UCAR
(1) Issues related to the assimilation of GPS RO data
(2) Different choices of observation operators
(3) Variational (3DVAR and 4DVAR) assimilation of GPS RO data
(4) Impact on prediction
2:30 - 3:00 Discussions
3:00 - 4:30 GAIM and Ionospheric RO data assimilation (#32)
George Hajj, JPL
(1) Ionospheric Forward Model
(2) GPS ionospheric occultation and other complementary data
(3) 4DVAR
(4) Validation
5:15 Bus Departs from FL2 to CU Williams Village Dormitory
Thursday, 1 July, 2004 - Mini-Workshop on Atmospheric Remote Sensing Using GPS
Special Session on the Assimilation of GPS Radio Occultation Data
Main Seminar Room, Mesa Laboratory, 1850 Table Mesa Drive
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to Mesa Lab
8:45 - 9:00 Opening Remarks
9:00 - 9:30 Forecast impact experiments with CHAMP RO measurements: Firsts results at ECMWF.
Sean Healy, ECMWF
9:30 - 10:00 Use of COSMIC observations in the NOAA/NWS/NCEP data assimilation systems.
Lidia Cucurull, UCAR and NOAA/NCEP
10:00 - 10:30 Assimilation of GPS RO data using the NCAR Data Assimilation Research Testbed.
Hui Liu, NCAR
10:30 - 10:45 Coffee Break (Mezzanine)
10:45 - 11:15 Assimilation of CHAMP and SAC-C Radio Occultation Data Using MM5 4DVAR.
Tae-Kwon Wee, UCAR COSMIC
11:15 - 11:45 Impact of Assimilated GPS Occultation Refractivity on Typhoon Predictions.
Ching-Yuan Huang, National Central University
11:45 - 1:00 Lunch
1:00 - 1:30 A refractivity mapping operator for the assimilation of GPS RO data: Consequences for error covariance estimation.
Stig Syndergaard, UCAR
1:30 - 2:00 Validation of a simple non-local observation operator for assimilating radio occultation data with high-resolution weather model.
Sergey Sokolovskiy, UCAR
2:00 - 2:30 Statistical optimization of radio occultation data with dynamical estimation of error covariances.
Martin Lohmann, UCAR and NESDIS
2:30 - 2:45 Coffee Break (Mezzanine)
2:45 - 3:15 Preparing to Use Operational GPS Radio Occultation Observations at NOAA.
James G. Yoe, NESDIS
3:15 - 3:45 Consistency of horizontal and vertical resolution of atmospheric parameters measured with GPS radio occultations
Marcello Petitta, University of Rome "La Sapienza"
3:45 - 4:15 Validation of GPS Radio Occultation Measurements and Retrieval methods
Grace S. Peng, The Aerospace Corporation
4:15 - 5:15 Open Discussion on issues facing the assimilation of GPS RO data:
(i) choice of observation operator
(ii) data quality control
(iii) observation error statistics
(iv) impact of assimilation model errors
(v) the value-added of GPS RO data
5:30 - 7:30 Pizza party at the Tree Plaza
7:30 Bus Departs for CU Williams Village Dormitory
Friday, 2 July 2004 (Mini-Workshop on GPS Atmospheric Remote Sensing - Main Seminar Room, Mesa Laboratory)
8:15 Bus Departs from CU Williams Village Dormitory (500 30th St. Boulder, CO. Phone: 303-492-6573) to Mesa Lab
8:45 - 9:15 ROSE - Comparisons of analysis results from JPL, UCAR and GFZ
Jens Wickert, GFZ, Potsdam, Germany
9:15 - 9:45 Three-dimensional ionospheric imaging using ground-based and CHAMP GPS observations: validation and results.
Claudia Stolle, University of Leipzig, Germany
9:45 - 10:15 Ionospheric tomography and numerical mapping of F2-layer critical frequency using GPS RO data.
Lung-Chih Tsai, National Central University
10:15 - 10:30 Coffee Break (Mezzanine)
10:30 - 11:00 Improving the convection forecast with assimilation of the real ground-based GPS data
Yong-Run Guo, NCAR
11:00 - 11:30 Diurnal Variations of Atmospheric Precipitable Water from GPS data -- from North America to the Globe
Junhong Wang, NCAR
11:30 - 12:00 Application of GPS Slant Water Vapor Tomography to an IHOP Storm Case with Simple Constraints
Yuanfu Xie, Forecast Systems Laboratory/NOAA
12:00 - 1:00 Lunch
1:00 - 1:30 Ground-based GPS PW Observations during the North American Monsoon Experiment (NAME)
Ronald S. Mastaler, U. of Arizona
1:30 - 2:00 An error analysis of ground-based GPS slant-path residuals in a simulation study
John Braun, UCAR
2:00 - 3:00 Open discussions on issues facing ground-based GPS atmospheric remote sensing
John Braun, UCAR - Facilitator

* Improving Raw GPS Observations
   - Reducing Multipath Effects
   - Low Elevation Data
* GPS Zenith Estimation Improvements
   - What is the "noise floor" of GPS PW
   - Are there improvements to be made in mapping functions (Niell, or DMF)
   - Are there improvements to be made in PI calculations
* Data Assimilation
   - What should be assimiliated (TZD, ZWD, PW)
   - Why is the current impact of GPS so inconclusive
   - Is there an optimal model resolution to utilize GPS observations
* Slant Methods
   - Can slant be parameterized within an estimation scheme
* Tomography
* Ocean Observations
   - Would a network of GPS buoys have useful Applications
* Merging GPS with Satellite Products
   - MODIS (currently 10-20% errors in MODIS PW). Is this a problem?
   - GOES
   - SSM/I and others (works over water, but less well over land)
* Direct Monitoring of the Water Cycle
   - Establishing a climate record
   - Water Vapor and Precipitation Interactions
   - Water Vapor Transport questions

3:00 - 3:30 Concluding Remarks
3:30 Bus departs Mesa Lab for Williams Village Dormitory