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Edward Hanna - One of the best experts on this subject based on the ideXlab platform.

  • the Solar Eclipse a natural meteorological experiment
    Philosophical Transactions of the Royal Society A, 2016
    Co-Authors: Giles R Harrison, Edward Hanna
    Abstract:

    A Solar Eclipse provides a well-characterized reduction in Solar radiation, of calculable amount and duration. This captivating natural astronomical phenomenon is ideally suited to science outreach activities, but the predictability of the change in Solar radiation also provides unusual conditions for assessing the atmospheric response to a known stimulus. Modern automatic observing networks used for weather forecasting and atmospheric research have dense spatial coverage, so the quantitative meteorological responses to an Eclipse can now be evaluated with excellent space and time resolution. Numerical models representing the atmosphere at high spatial resolution can also be used to predict Eclipse-related changes and interpret the observations. Combining the models with measurements yields the elements of a controlled atmospheric experiment on a regional scale (10-1000 km), which is almost impossible to achieve by other means. This modern approach to 'Eclipse meteorology' as identified here can ultimately improve weather prediction models and be used to plan for transient reductions in renewable electricity generation. During the 20 March 2015 Eclipse, UK electrical energy demand increased by about 3 GWh (11 TJ) or about 4%, alongside reductions in the wind and photovoltaic electrical energy generation of 1.5 GWh (5.5 TJ).This article is part of the themed issue 'Atmospheric effects of Solar Eclipses stimulated by the 2015 UK Eclipse'.

  • meteorological effects of the Solar Eclipse of 20 march 2015 analysis of uk met office automatic weather station data and comparison with automatic weather station data from the faroes and iceland
    Philosophical Transactions of the Royal Society A, 2016
    Co-Authors: Edward Hanna, John Penman, Trausti Jonsson, Grant R Bigg, Halldor Bjornsson, Solvi Sjurðarson, Mads A Hansen, John Cappelen, Robert G Bryant
    Abstract:

    Here, we analyse high-frequency (1min) surface air temperature, mean sea-level pressure (MSLP), wind speed and direction and cloud-cover data acquired during the Solar Eclipse of 20 March 2015 from...

Xinan Yue - One of the best experts on this subject based on the ideXlab platform.

  • gps tec response to the 22 july 2009 total Solar Eclipse in east asia
    Journal of Geophysical Research, 2010
    Co-Authors: Feng Ding, Baiqi Ning, Weixing Wan, Libo Liu, Min Wang, Yiding Chen, Zhipeng Ren, Bo Xiong, Xinan Yue
    Abstract:

    [1] The longest total Solar Eclipse of this century occurred in East and South Asia on 22 July 2009. The Eclipse was accompanied with a medium magnetic storm, whose main phase onset occurred ∼27 min after the passage of the Moon's umbral shadow. Using TEC data from 60 GPS stations, we construct differential TEC maps to investigate the ionosphere response to the Solar Eclipse in central China in the range of 26°N–36°N, 108°E–118°E (i.e., the magnetic latitude 15°N–25°N). During the Eclipse's totality, a “shadow” in the ionosphere shown as TEC depletion area was formed ∼100 km south of the Moon's umbral path with a maximum decrease of 5 TECU. The TEC depletion area moved eastward, following the movement of the totality area with a time lag of ∼10 min. Enhancements of TEC due to the storm are observed after the main phase onset. The relative drop of TEC due to the Solar Eclipse is evidently larger at lower latitudes than that at higher ones and around noontime than that in the morning. By modeling work, we find that the latitudinal dependence of the TEC response may result from latitudinal variation of magnetic inclination, which influences the diffusion of ionization among different layers. Besides, the local time dependence of TEC response is closely related to the local time variation of background atmosphere density, which affects the electron loss efficiency in the ionosphere.

  • the ionospheric behavior in conjugate hemispheres during the 3 october 2005 Solar Eclipse
    Annales Geophysicae, 2009
    Co-Authors: Libo Liu, Xinan Yue, Weixing Wan
    Abstract:

    Abstract. We investigate the ionospheric behavior in conjugate hemispheres during the 3 October 2005 Solar Eclipse, on the basis of observations of electron temperature (Te) from the Defense Meteorological Satellites Program (DMSP) spacecraft, F2 layer critical frequency (foF2) and F2 layer peak height (hmF2) at the Grahamstown ionosonde station, and total electron content (TEC) from the Global Positioning System (GPS) station SUTH. The observations show that when the Eclipse occurred in the Northern Hemisphere, there was a decrease in Te, an increase in foF2 and TEC, and an uprising in hmF2 in its conjugate region compared with their reference values. We also simulated the ionosphere behavior during this Eclipse using a mid- and low-latitude ionospheric model. The simulations agree well with the observations. Because of the Eclipse effect, there are far fewer photoelectrons travelling along the magnetic field lines from the Eclipse region to the conjugate region, resulting in reduced photoelectron heating in the conjugate hemisphere which causes a drop in electron temperature and subsequent disturbances in the region.

  • the ionospheric responses to the 11 august 1999 Solar Eclipse observations and modeling
    Annales Geophysicae, 2008
    Co-Authors: Libo Liu, Xinan Yue, Weixing Wan
    Abstract:

    A total Eclipse occurred on 11 August 1999 with its path of totality passing over central Europe in the lat- itude range 40 -50 N. The ionospheric responses to this Eclipse were measured by a wide ionosonde network. On the basis of the measurements of foE, foF1, and foF2 at six- teen ionosonde stations in Europe, we statistically analyze the variations of these parameters with a function of Eclipse magnitude. To model the Eclipse effects more accurately, a revised Eclipse factor, FR, is constructed to describe the vari- ations of Solar radiation during the Solar Eclipse. Then we simulate the effect of this Eclipse on the ionosphere with a mid- and low-latitude ionosphere theoretical model by using the revised Eclipse factor during this Eclipse. Simulations are highly consistent with the observations for the response in the E-region and F1-region. Both of them show that the max- imum response of the mid-latitude ionosphere to the Eclipse is found in the F1-region. Except the obvious ionospheric response at low altitudes below 500 km, calculations show that there is also a small response at high altitudes up to about 2000 km. In addition, calculations show that when the Eclipse takes place in the Northern Hemisphere, a small ionospheric disturbance also appeared in the conjugate hemi- sphere.

Manish Naja - One of the best experts on this subject based on the ideXlab platform.

  • influence of Solar Eclipse of 15 january 2010 on surface ozone
    Atmospheric Environment, 2011
    Co-Authors: T Nishanth, Narendra Ojha, M Satheesh K Kumar, Manish Naja
    Abstract:

    Abstract This study pertains to the variations observed in the mixing ratios of surface ozone, its prominent precursor NOx∗ and the meteorological parameters (Solar radiation, temperature, relative humidity and wind speed) during the annular Solar Eclipse that occurred on 15 January 2010 at Kannur (11.9°N, 75.4°E, 5 m amsl), a tropical coastal site in the southern region of India. The Solar Eclipse started at 11:05 IST (IST is 5.5 h ahead of UTC), reached to the maximum obscuration at 13:20 IST and ended at 15:05 IST. The observations made at Kannur show influences of the Solar Eclipse phenomenon on the surface ozone and NOx∗ mixing ratios. A sharp decline in the surface ozone was observed during the Eclipse, due to the decreased efficiency of the photochemical ozone formation. The NO2∗ levels were found to increase during the Eclipse period while the NO levels remained unchanged. The Eclipse induced reduction in surface ozone and enhancement in NOx∗are estimated to be 57.5% and 62.5% respectively. Reductions in the air temperature, relative humidity and wind speed were also observed during the event of Solar Eclipse. Simulation from a chemical box model indicates about 94% reduction in the NO2 photolysis rates during the Eclipse period, which is leading to about 59% reduction in the surface ozone. Observations as well as model simulations indicate that the reduced photochemical ozone production from NO2 photolysis is possibly the main driver of ozone reduction during the Eclipse at this site.

Robert G Bryant - One of the best experts on this subject based on the ideXlab platform.

Gang Chen - One of the best experts on this subject based on the ideXlab platform.

  • plasma flux and gravity waves in the midlatitude ionosphere during the Solar Eclipse of 20 may 2012
    Journal of Geophysical Research, 2015
    Co-Authors: Gang Chen, Zhengyu Zhao, Dingkun Zhong, X Huang, Liang Huang, Lei Qiao, Jin Wang
    Abstract:

    The Solar Eclipse effects on the ionosphere are very complex. Except for the ionization decay due to the decrease of the photochemical process, the couplings of matter and energy between the ionosphere and the regions above and below will introduce much more disturbances. Five ionosondes in the Northeast Asia were used to record the midlatitude ionospheric responses to the Solar Eclipse of 20 May 2012. The latitude dependence of the Eclipse lag was studied first. The foF2 response to the Eclipse became slower with increased latitude. The response of the ionosphere at the different latitudes with the same Eclipse obscuration differed from each other greatly. The plasma flux from the protonsphere was possibly produced by the rapid temperature drop in the lunar shadow to make up the ionization loss. The greater downward plasma flux was generated at higher latitude with larger dip angle and delayed the ionospheric response later. The waves in the foEs and the plasma frequency at the fixed height in the F layer are studied by the time period analytic method. The gravity waves of 43–51 min center period during and after the Solar Eclipse were found over Jeju and I-Cheon. The northward group velocity component of the gravity waves was estimated as ~108.7 m/s. The vertical group velocities between 100 and 150 km height over the two stations were calculated as ~5 and ~4.3 m/s upward respectively, indicating that the Eclipse-induced gravity waves propagated from below the ionosphere.

  • daytime e region field aligned irregularities observed during a Solar Eclipse
    Journal of Geophysical Research, 2014
    Co-Authors: Gang Chen, Zhengyu Zhao, Dingkun Zhong, Han Jin
    Abstract:

    The driving mechanism of the midlatitude field-aligned irregularities (FAIs) has been in dispute for many years. The experimental observations were carried out during the Solar Eclipse of 22 July 2009 in Wuhan, China, to study the possibility of the wave-driven irregularities. A high-frequency coherent scatter radar was used to detect the E region irregularities. An ionosonde was applied to record the trace of gravity waves in ionosphere. The E region FAIs occurred at the end of the Solar Eclipse with fluctuant Doppler. At the same time, the oscillations on the fEs (maximum reflecting frequency of Es) curve and in the Doppler velocity of the echoes from the Es layer were also recorded. The data analysis and comparison show that the gravity waves and the FAIs occurred at the same time with the in-phase variations in amplitude and phase. Thus, the Solar Eclipse and the gravity waves may play important roles in the occurrence of the irregularities. A schematic diagram of one-period gravity wave is used to explain the possible gravity wave-driven mechanism and the Doppler fluctuation in the irregularities. The daytime FAI in midlatitude is a rare phenomenon, even in the condition of Solar Eclipse. There are only four cases of the E region FAIs observed during a Solar Eclipse, including our observations. The unique feature of our observations is the synchronized oscillations in the irregularities and in the Es layer, which will help address the outstanding question of the source of the midlatitude E region FAIs.

  • nighttime ionospheric enhancements induced by the occurrence of an evening Solar Eclipse
    Journal of Geophysical Research, 2013
    Co-Authors: Gang Chen, Zhengyu Zhao, Baiqi Ning, Ming Yao, Zhongxing Deng, Shuo Huang, Wenchao Feng
    Abstract:

    [1] The Solar Eclipse on 15 January 2010 traversed Asia and completed its travel on the Shandong Peninsula in China at sunset. Two vertical incidence ionosondes at Wuhan and Beijing and the oblique incidence ionosonde network in North China were implemented to record the ionospheric response to the Solar Eclipse. Following the initial electron density decrease caused by the Eclipse, the ionosphere was characterized by a strong premidnight enhancement, and a subsequent ionospheric decay, and a ~10 h later postmidnight enhancement. Neither geomagnetic disturbance occurred during the Eclipse day nor did obvious nighttime peak appear for the 10 day mean of the F2-layer critical frequency (foF2). The electron density profilogram of the Beijing ionosonde indicates that the two enhancements were the result of the plasma flux downward from the top ionosphere, possibly due to the steep decrease of the ionospheric electron density and plasma temperature during the Solar Eclipse. The two-dimensional differential foF2 maps present the regional variations of the nighttime electron density peaks and decay. Both the pre- and postmidnight enhancements initially appeared in a belt almost in parallel with the Eclipse track and then drifted southward. The different magnitudes of greatest Eclipse in the umbra and outside tend to account for the different occurrence times of the plasma flux. The ionospheric decay following the premidnight enhancement is also considered as a consequence of the Eclipse shade.

  • latitudinal dependence of the ionospheric response to Solar Eclipse of 15 january 2010
    Journal of Geophysical Research, 2011
    Co-Authors: Gang Chen, Zhengyu Zhao, Baiqi Ning, Zhongxin Deng, Guobin Yang, Chen Zhou, Ming Yao
    Abstract:

    [1] The ionospheric responses to the Solar Eclipse of 15 January 2010 in the equatorial anomaly region have been investigated by three vertical-incidence and seven oblique-incidence ionosondes arranged along the meridian from geomagnetic latitudes 18°N to 30°N in eastern China. Though the Solar Eclipse occurred later in the evening, the Eclipse effect on electron density and reflection height of ionospheric F2 layer was clearly observed. The study of the Eclipse lag (the time lag between the occurrence of the Eclipse maximum obscuration and the occurrence of the maximum depletion of foF2) with latitude indicates it increased with F2 layer altitude. Results suggest also that this Eclipse enhanced the prereversal enhancement. An unusual peak occurred after the maximum reduction in foF2 and this was observed by all our ionosondes. The following F2 layer plasma density increase was considered to be caused by the increased westward electric field.