Remote sensing of tropospheric turbulence using GPS radio occultation

Abstract. Radio occultation (RO) measurements are sensitive to the small-scale irregularities in the atmosphere. In this study, we present a new technique to estimate tropospheric turbulence strength (namely, scintillation index) by analyzing RO amplitude fluctuations in impact parameter domain. GPS RO observations from the COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) satellites enabled us to calculate global maps of scintillation measures, revealing the seasonal, latitudinal, and longitudinal characteristics of the turbulent troposphere. Such information are both difficult and expensive to obtain especially over the oceans. To verify our approach, simulation experiments using the multiple phase screen (MPS) method were conducted. The results show that scintillation indices inferred from the MPS simulations are in good agreement with scintillation measures estimated from COSMIC observations.

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Simulated GPS radio occultation signals from sporadic-E layers

10.5194/egusphere-egu2020-12026 ◽

2020 ◽

Author(s):

Daniel Emmons

Keyword(s):

Radio Occultation ◽

Plasma Frequency ◽

Signal Amplitude ◽

Scintillation Index ◽

Gps Radio Occultation ◽

Multiple Phase ◽

Maximum Variance ◽

Sporadic E Layers ◽

Sporadic E ◽

Screen Model

<p>A multiple phase screen model is used to simulate GPS radio occultation signals through varying sporadic-E layers.&#160; The length, vertical extent, and plasma frequency of the sporadic-E layers are varied to analyze the effect on the signal received by a low earth orbiting satellite.&#160; A nonlinear relationship between the maximum variance in the signal amplitude and the plasma frequency is observed.&#160; For certain frequency ranges, the predictions match previous studies that have used the S<sub>4 </sub>scintillation index to predict fbEs values. Additionally, the spectra of the signals are analyzed as a function of the different parameters providing an alternative approach for extracting sporadic-E parameters from GPS radio occultation measurements.&#160;</p>

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Modulation of sporadic E layers by small-scale atmospheric waves in Earth’s high-latitude ionosphere

Solnechno-Zemnaya Fizika ◽

10.12737/szf-53201912 ◽

2019 ◽

Vol 5 (3) ◽

pp. 116-129

Author(s):

Владимир Губенко ◽

Vladimir Gubenko ◽

Иван Кириллович ◽

Ivan Kirillovich

Keyword(s):

High Latitude ◽

Radio Occultation ◽

Small Scale ◽

Polar Cap ◽

Atmospheric Waves ◽

Sporadic E Layers ◽

High Latitude Ionosphere ◽

Sporadic E Layer ◽

Sporadic E ◽

Good Agreement

We have used radio occultation measurements of the satellite CHAMP (Challenging Minisatellite Payload) to examine sporadic E layers (altitudes 90–130 km) in Earth’s high-latitude ionosphere. We have developed a new method for determining characteristics of internal atmospheric waves based on the use of inclined sporadic E layers of Earth’s ionosphere as a detector. The method relies on the fact that an internal wave propagating through the initially horizontal sporadic E layer causes the plasma density gradient to rotate in the direction of the wave vector, which leads to the fact that the layer ionization plane is set parallel to the phase wave front. The developed method enables us to study the interrelations between small-scale internal waves and sporadic E layers in Earth’s ionosphere and significantly expands the capabilities of traditional radio occultation monitoring of the atmosphere. We have found that the internal atmospheric waves under study have periods from 35 to 46 min and vertical phase speeds from 1.2 to 2.0 m/s, which are in good agreement with the results of independent experiments and simulation data on sporadic E layers at a height of ~100 km in Earth’s polar cap.

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Using GNSS radio occultation data to derive critical frequencies of the ionospheric sporadic E layer in real time

GPS Solutions ◽

10.1007/s10291-020-01050-6 ◽

2020 ◽

Vol 25 (1) ◽

Author(s):

Bingkun Yu ◽

Christopher J. Scott ◽

Xianghui Xue ◽

Xinan Yue ◽

Xiankang Dou

Keyword(s):

Real Time ◽

Radio Occultation ◽

Middle Latitude ◽

Satellite System ◽

Relative Difference ◽

Scintillation Index ◽

Small Scale ◽

Sporadic E ◽

Occultation Data ◽

Global Navigation Satellite

Abstract The small-scale electron density irregularities in the ionosphere have a significant impact on the interruptions of Global Navigation Satellite System (GNSS) navigation and the accuracy of GNSS positioning techniques. The sporadic ionospheric E (Es) layer significantly contributes to the transient interruptions of signals (loss of lock) for GNSS tracking loops. These effects on the GNSS radio occultation (RO) signals can be used to derive the global location and intensity of Es layers as a complement to ground-based observations. Here we conduct statistical analyses of the intensity of Es layers, based on the scintillation index S4max from the FORMOSAT-3/COSMIC during the period 2006–2014. In comparison with simultaneous observations from an ionosonde network of five low-to-middle latitude ionosondes, the S4max indices from COSMIC, especially the small values, are linearly related to the critical frequency of Es layers (foEs). An accumulated period of less than 1 h is required to derive the short-term variations in real-time ionospheric Es layers. A total of 30.22%, 69.57% and 98.13% coincident hourly foEs values have a relative difference less than 10%, 30% and 100%. Overall, the GNSS RO measurements have the potential to provide accurate hourly observations of Es layers. Observations with S4max < 0.4 (foEs < 3.6 MHz), accounting for 66% of COSMIC S4 measurements, have not been used fully previously, as they are not easily visible in ground-based ionosonde data.

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Application of the locality principle to radio occultation studies of the Earth's atmosphere and ionosphere

Atmospheric Measurement Techniques ◽

10.5194/amt-8-2885-2015 ◽

2015 ◽

Vol 8 (7) ◽

pp. 2885-2899 ◽

Cited By ~ 9

Author(s):

A. G. Pavelyev ◽

Y. A. Liou ◽

S. S. Matyugov ◽

A. A. Pavelyev ◽

V. N. Gubenko ◽

...

Keyword(s):

Remote Sensing ◽

Spherical Symmetry ◽

Radio Occultation ◽

Single Frequency ◽

Scintillation Index ◽

Joint Analysis ◽

Total Absorption ◽

Radio Waves ◽

Locality Principle ◽

Phase Variations

Abstract. A new formulation of the previously introduced principle of locality is presented. The principle can be applied for modernization of the radio occultation (RO) remote sensing of the atmospheres and ionospheres of the Earth and other planets. The principle states that significant contributions to variations of the intensity and phase of the radio waves passing through a layered medium are connected with influence of the vicinities of tangential points where the refractivity gradient is perpendicular to the radio ray trajectory. The RO method assumes spherical symmetry of the investigated medium. In this case, if location of a tangent point relative to the spherical symmetry centre is known, the time derivatives of the RO signal phase and Doppler frequency variations can be recalculated into the refractive attenuation. Several important findings are consequences of the locality principle: (i) if position of the centre of symmetry is known, the total absorption along the ray path can be determined at a single frequency; (ii) in the case of low absorption the height, displacement from the radio ray perigee, and tilt of the inclined ionospheric (atmospheric) layers can be evaluated; (iii) the contributions of the layered and irregular structures in the RO signal can be separated and parameters of layers and turbulence can be measured at a single frequency using joint analysis of the intensity and phase variations. Specially for the Earth's troposphere, the altitude distributions of the weak total absorption (about of 1–4 db) of the radio waves at GPS frequencies corresponding to possible influence of the oxygen, water vapour, and hydrometeors can be measured with accuracy of about 0.1 db at a single frequency. In accordance with the locality principle, a new index of ionospheric activity is introduced. This index is measured from the phase variations of radio waves passing through the ionosphere. Its high correlation with the S4 scintillation index is established. This correlation indicates the significant influence of locally spherical symmetric ionospheric layers on variations of the phase and intensity of the RO signal passing through transionospheric communication links. Obtained results expand applicable domain of the RO method as a powerful remote sensing technique for geophysical and meteorological research.

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Application of locality principle to radio occultation studies of the Earth's atmosphere and ionosphere

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-721-2015 ◽

2015 ◽

Vol 8 (1) ◽

pp. 721-758

Author(s):

A. G. Pavelyev ◽

Y. A. Liou ◽

S. S. Matyugov ◽

A. A. Pavelyev ◽

V. N. Gubenko ◽

...

Keyword(s):

Remote Sensing ◽

Spherical Symmetry ◽

Radio Occultation ◽

Single Frequency ◽

Scintillation Index ◽

Joint Analysis ◽

Total Absorption ◽

Radio Waves ◽

Locality Principle ◽

Phase Variations

Abstract. A new formulation of previously introduced principle of locality is presented. The principle can be applied for modernization of the radio occultation (RO) remote sensing of the atmospheres and ionospheres of the Earth and planets. The principle states that significant contributions to variations of the amplitude and phase of the radio waves passing through a layered medium are connected with influence of the vicinities of tangential points where the refractivity gradient is perpendicular to the radio ray trajectory. The RO method assumes spherical symmetry of the investigated medium. In this case if location of a tangent point relative to the spherical symmetry center is known, the derivatives on time of the RO signal phase and Doppler frequency variations can be recalculated into the refractive attenuation. Several important findings are consequences of the locality principle: (i) if position of the center of symmetry is known, the total absorption along the ray path can be determined at a single frequency, (ii) in the case of low absorption the height, displacement from the radio ray perigee, and tilt of the inclined ionospheric (atmospheric) layers can be evaluated, (iii) the contributions of the layered and irregular structures in the RO signal can be separated and parameters of layers and turbulence can be measured at a single frequency using joint analysis of the amplitude and phase variations. Specially for the Earth's troposphere, the altitude distributions of the weak total absorption (about of 1–4 db) of the radio waves at GPS frequencies corresponding to possible influence of the oxygen and water vapor can be measured with accuracy of about 0.1 db at a single frequency. According with the locality principle, a new index of ionospheric activity is introduced. This index is measured from the phase variations of radio waves passing through the ionosphere. Its high correlation with S4 scintillation index is established. This correlation indicates the significant influence of locally spherical symmetric ionospheric layers on variations of the phase and amplitude of the RO signal passing through transionospheric communication links. Obtained results expand the applicable domain of the RO method as a powerful remote sensing technique for geophysical and meteorological research.

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A representative density profile for the North Greenland snowpack

10.5194/tc-2016-102 ◽

2016 ◽

Author(s):

Christoph Florian Schaller ◽

Johannes Freitag ◽

Sepp Kipfstuhl ◽

Thomas Laepple ◽

Hans Christian Steen-Larsen ◽

...

Keyword(s):

Remote Sensing ◽

High Resolution ◽

Density Profile ◽

Accumulation Rate ◽

Data Sets ◽

Accumulation Rates ◽

The North ◽

A New Technique ◽

North Greenland ◽

Good Agreement

Abstract. Along a traverse through North Greenland in May 2015 we sampled the top two meters of snow and analyzed its density and water isotopic composition. A new technique for probing the upper meters of the snow and an adapted algorithm for comparing data sets from different positions and aligning stratigraphic features is presented. We find good agreement of the density layering in the snowpack over hundreds of kilometers, which allows the construction of a representative density profile. The results are supported by an empirical based statistical density model, that is used to generate sets of random profiles and validate the applied methods. Furthermore we are able to calculate annual accumulation rates, align melt layers and observe isotopic temperatures in the area back to 2010. Distinct relations of δ18O with both accumulation rate and density are deduced. Inter alia the depths of the 2012 melt layers and high resolution densities are provided for applications in remote sensing.

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Modulation of sporadic E layers by small-scale atmospheric waves in Earth’s high-latitude ionosphere

Solar-Terrestrial Physics ◽

10.12737/stp-53201912 ◽

2019 ◽

Vol 5 (3) ◽

pp. 98-108

Author(s):

Владимир Губенко ◽

Vladimir Gubenko ◽

Иван Кириллович ◽

Ivan Kirillovich

Keyword(s):

High Latitude ◽

Radio Occultation ◽

Small Scale ◽

Polar Cap ◽

Atmospheric Waves ◽

Sporadic E Layers ◽

High Latitude Ionosphere ◽

Sporadic E Layer ◽

Sporadic E ◽

Good Agreement

We have used radio occultation measurements of the satellite CHAMP (Challenging Minisatellite Payload) to examine sporadic E layers (altitudes 90–130 km) in Earth’s high-latitude ionosphere. We have developed a new method for determining characteristics of internal atmospheric waves based on the use of inclined sporadic E layers of Earth’s ionosphere as a detector. The method relies on the fact that an internal wave propagating through the initially horizontal sporadic E layer causes the plasma density gradient to rotate in the direction of the wave vector, which leads to the fact that the layer ionization plane is set parallel to the phase wave front. The developed method enables us to study the interrelations between small-scale internal waves and sporadic E layers in Earth’s ionosphere and significantly expands the capabilities of traditional radio occultation monitoring of the atmosphere. We have found that the internal atmospheric waves under study have periods from 35 to 46 min and vertical phase speeds from 1.2 to 2.0 m/s, which are in good agreement with the results of independent experiments and simulation data on sporadic E layers at a height of ~100 km in Earth’s polar cap.

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Small-scale vegetation mapping of large territories: perspectives of using modern remote sensing and GIS technologies, the Indian experiences

Geobotanical mapping ◽

10.31111/geobotmap/1994-1995.51 ◽

1996 ◽

pp. 51-54 ◽

Cited By ~ 1

Author(s):

N. V. M. Unni

Keyword(s):

Remote Sensing ◽

Satellite Remote Sensing ◽

Forest Cover ◽

Human Life ◽

Remote Sensing Data ◽

Modern World ◽

Small Scale ◽

Vegetation Map ◽

Gis Technologies ◽

Forest Cover Mapping

The recognition of versatile importance of vegetation for the human life resulted in the emergence of vegetation science and many its applications in the modern world. Hence a vegetation map should be versatile enough to provide the basis for these applications. Thus, a vegetation map should contain not only information on vegetation types and their derivatives but also the geospheric and climatic background. While the geospheric information could be obtained, mapped and generalized directly using satellite remote sensing, a computerized Geographic Information System can integrate it with meaningful vegetation information classes for large areas. Such aft approach was developed with respect to mapping forest vegetation in India at. 1 : 100 000 (1983) and is in progress now (forest cover mapping at 1 : 250 000). Several review works reporting the experimental and operational use of satellite remote sensing data in India were published in the last years (Unni, 1991, 1992, 1994).

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Interferential seeing monitor, a seeing monitor for atmospheric turbulence studies: calibration with the differential image motion monitor

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2400 ◽

2020 ◽

Vol 500 (2) ◽

pp. 1884-1888

Author(s):

Mohammed Sabil ◽

A Habib ◽

Z Benkhaldoun

Keyword(s):

Structure Function ◽

Atmospheric Turbulence ◽

Wave Structure ◽

Image Motion ◽

Phase Fluctuations ◽

Amplitude Fluctuations ◽

Focus Plane ◽

Cross Calibration ◽

Double Slit ◽

Good Agreement

ABSTRACT In this work, we aim to calibrate an interferential seeing monitor (ISM), which is a testing instument used at astronomical sites. Its method is based on the study of the diffraction pattern produced by a Young’s double-slit at the focus plane of a telescope. This method allows us to obtain the wave structure function by taking into account both phase and amplitude fluctuations of the light wavefront. A phase seeing εϕ was assigned to phase fluctuations and an amplitude seeing εχ was assigned to amplitude fluctuations (scintillation phenomenon), which allows us to obtain both phase and amplitude fluctuations. The feasibility of the ISM method was demonstrated by numerical simulations presented in a previous work. In this work, we have conducted a cross-calibration campaign of the ISM with a differential image motion monitor (DIMM) over 16 nights at the Oukaimeden and Atlas Golf Marrakech Observatories. The goal of this campaign was to study the reliability of this new method. In this paper, we present the calibration measurements and a comparison between the seeing measured by the ISM (εϕ, εχ) and that obtained by the DIMM (εdimm). These results show good agreement between the phase- eeing εϕ and εdimm.

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