Adjusting CCIR Maps to Improve Local Behaviour of Ionospheric Models

Haralambous, Haris; Leontiou, Theodoros; Petrou, Vasilis; Singh, Arun Kumar; Charalambides, Marios; Lithoxopoulos, Nikos; Agisilaou, Agis

doi:10.3390/atmos12060691

Cited by 6 publications

(4 citation statements)

References 19 publications

(23 reference statements)

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“…Time series of VTEC values (equivalent to GPS ionospheric delay) were further processed using our own R-based software. Time series of VTEC values observed during the European volcanic ash 2010 crisis were compared with the normal VTEC values observed at the same station sites in quiet-space weather and ionospheric conditions, in order to assess the contribution of volcanic ash to the overall GPS ionospheric delay [7,33]. In addition, a due consideration was given to the global status of the geomagnetic and ionospheric conditions, using the reference data from [37], in order to distinguish volcanic ash affects from potential effects of global geomagnetic and ionospheric storms.…”

Section: Outline Of Methodologymentioning

confidence: 99%

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Eyjafjallajökull Volcanic Ash 2010 Effects on GPS Positioning Performance in the Adriatic Sea Region

2021

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The Eyjafjallajökull volcanic ash crisis in 2010 temporarily suspended European air traffic operations, as the 39-day eruption caused widely dispersed ashes to enter the lower atmosphere. In this paper, we assessed the effects of this event on the ionosphere layer and, consequently, on GPS positioning. We collected and analysed the data from four IGS stations, nearest to the volcano, for the month of April 2010. We recorded Vertical Total Electron Content (VTEC) time series, analysed their dynamics, and compared them with the GPS positioning errors of a commercial-grade, un-aided, single-frequency GPS receiver (simulating the response of a mass-market GPS receiver). The geomagnetic indices during the time period show little geomagnetic disturbance, especially during the volcanic event. Our results show an enhancement in ionosphere error by up to 15% during the volcanic ash event and an enhanced variance in GPS position components errors. This study reveals the potential impact of the charged volcanic ash on single-frequency, unaided GPS positioning accuracy in the Adriatic Sea region and establishes a foundation for studying similar events in future.

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Section: Outline Of Methodologymentioning

confidence: 99%

“…By definition, TEC is the total number of free electrons encountered by a GPS signal travelling from a GPS satellite to a GPS user aerial. It determines the value of the GPS ionosphere delay and causes significant errors in GPS positioning [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Eyjafjallajökull Volcanic Ash 2010 Effects on GPS Positioning Performance in the Adriatic Sea Region

2021

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“…The CCIR maps for the F2 parameter consist of 988 coefficients for each month. CCIR provides two sets of coefficients, one for low sunspot numbers and one for high (Haralambous et al., 2021). The coefficients for intermediate levels of solar activity are determined by linear interpolation (European Commission, 2016).…”

Section: Background Modelmentioning

confidence: 99%

One‐Dimensional Variational Ionospheric Retrieval Using Radio Occultation Bending Angles: 2. Validation

Elvidge,

Healy,

Culverwell

2024

Space Weather

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Culverwell et al. (2023, https://doi.org/10.22541/essoar.168614409.98641332) described a new one‐dimensional variational (1D‐Var) retrieval approach for ionospheric GNSS radio occultation (GNSS‐RO) measurements. The approach maps a one‐dimensional ionospheric electron density profile, modeled with multiple “Vary‐Chap” layers, to bending angle space. This paper improves the computational performance of the 1D‐Var retrieval using an improved background model and validates the approach by comparing with the COSMIC‐2 profile retrievals, based on an Abel Transform inversion, and co‐located (within 200 km) ionosonde observations using all suitable data from 2020. A three or four layer Vary‐Chap in the 1D‐Var retrieval shows improved performance compared to COSMIC‐2 retrievals in terms of percentage error for the F2 peak parameters (NmF2 and hmF2). Furthermore, skill in retrieval (compared to COSMIC‐2 profiles) throughout the bottomside (∼90–300 km) has been demonstrated. With a single Vary‐Chap layer the performance is similar, but this improves by approximately 40% when using four‐layers.

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“…The CCIR maps for the F2 parameter consist of 988 coefficients for each month. CCIR provides two sets of coefficients, one for low sunspot numbers and one for high (Haralambous et al, 2021). The coefficients for intermediate levels of solar activity are determined by linear interpolation (European Commission, 2016).…”

Section: Nmf2mentioning

confidence: 99%

One-Dimensional Variational Ionospheric Retrieval Using Radio Occultation Bending Angles: Part 2 - Validation

Elvidge

Healy

Culverwell

2023

Preprint

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Culverwell et al. (2023) described a new one-dimensional variational (1D-Var) retrieval approach for ionospheric GNSS radio occultation (GNSS-RO) measurements. The approach maps a one-dimensional ionospheric electron density profile, modeled with multiple ”Vary-Chap’ layers, to bending angle space. This paper improves the computational performance of the the 1D-Var retrieval using an improved background model and validates the approach by comparing with the COSMIC-2 profile retrievals, based on an Abel Transform inversion, and co-located (within 200 km) ionosonde observations using all suitable data from 2020. A three or four layer Vary-Chap in the 1D-Var retrieval shows improved performance compared to COSMIC-2 retrievals in terms of percentage error for the F2 peak parameters (NmF2 and hmF2). Furthermore, skill in retrieval (compared to COSMIC-2 profiles) throughout the bottomside (~90 km to 300 km) has been demonstrated. With a single Vary-Chap layer the performance is similar, but this improves by approximately 40% when using four-layers.

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Adjusting CCIR Maps to Improve Local Behaviour of Ionospheric Models

Cited by 6 publications

References 19 publications

Eyjafjallajökull Volcanic Ash 2010 Effects on GPS Positioning Performance in the Adriatic Sea Region

Eyjafjallajökull Volcanic Ash 2010 Effects on GPS Positioning Performance in the Adriatic Sea Region

One‐Dimensional Variational Ionospheric Retrieval Using Radio Occultation Bending Angles: 2. Validation

One-Dimensional Variational Ionospheric Retrieval Using Radio Occultation Bending Angles: Part 2 - Validation

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