Transcript Ground-based GNSS receivers as a meteorological observing

Mesoscale ionospheric tomography over
Finland
Juha-Pekka Luntama
Finnish Meteorological Institute
Cathryn Mitchell, Paul Spencer
University of Bath
4th European Space Weather Week, 5 – 9 November, 2007
Outline
1) Introduction
2) MIDAS algorithm and Finnish GNSS network
3) Global and mesoscale retrievals
4) Validation of the results
5) Summary and next steps
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Introduction
• Currently many services are providing global TEC maps in NRT (IGS,
SWACI, JPL, …) based on observations from globally distributed
GNSS stations (e.g. IGS, EUREF, …)
• Number of IGS and EUREF GNSS stations is low at auroral region
=> resolution of the global maps is limited at the area where the
ionosphere is very dynamic
• Dense GNSS networks available in Scandinavia – already used for
NWP in the EUMETNET E-GVAP framework
• Our objective is to retrieve high resolution TEC and electron density
maps based on these observations
• Test data collected in December 2006
• This work is done in collaboration between University of Bath and FMI
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Multi-Instrument Data Analysis System (MIDAS)
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•
MIDAS is an advanced algorithm
developed by University of Bath for
imaging the Earth's ionosphere using
data from various ground and spacebased instrumentation.
•
Line integral observations of the total
electron content (TEC) obtained
from a network of ground-based and
space-based GPS receivers may be
assimilated into the algorithm along
with point estimates of the local
electron density.
•
The resulting reconstructions provide
a highly accurate three-dimensional
image of the Earth's ionosphere and
its evolution in time.
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GPS network in Finland operated by Geotrim Ltd
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GPS ray path intersections within the grid
Level height = 300 km
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It was a dark and stormy night…
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IMAGE Magnetogram on 14 - 15 Dec 2006
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IGS global TEC maps on 14 - 15 Dec 2006
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Resolution enhancement with regional
observations
IGS
Regional
15 December 2006, 02:00
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3D electron density distributions
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High resolution TEC maps 14 – 15 Dec, 2006
Question: Do these maps represent the real ionosphere?
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Validation opportunity:
Ionospheric Tomography Chain observations
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Intercomparison on 15 Dec 2006 at 02:45
Ionospheric Tomography
Chain projection plane
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Summary
• These are the first results from a new ionospheric tomography testing
in Finland
• The results indicate that mesoscale ionospheric tomography can
provide electron density distributions with very high horizontal and
temporal resolution
• Current results are based on using only ground based GPS
observations => vertical resolution and accuracy of the height
information is limited
• Real time data streaming from the GNSS network will be started
before the end of the year => development of NRT user service
feasible
• Some potential application areas:
– ionospheric monitoring, storm warning, and correction service for GNSS
applications
– GNSS ionospheric error and scintillation forecasting research
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Next steps
• Improve vertical resolution:
– Use also GLONASS observations (routinely available from the Geotrim
network)
– Ingest spaceborne RO soundings
– Combine with other types of observations
=> data assimilation
• Validation of the high resolution tomography maps is a challenge
=> processing of more test cases
=> a rigorous error analysis
=> analysis of the impacts on independent GNSS receivers (IGS,
EUREF)
=> careful validation with independent observations (ionospheric
tomography chain, ionosonde, EISCAT, …)
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