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Fabrice Chane-Ming - One of the best experts on this subject based on the ideXlab platform.

  • Diagnosis of tropical cyclone activity through gravity wave Energy Density in the southwest Indian Ocean
    Geophysical Research Letters, 2016
    Co-Authors: C. Ibrahim, Fabrice Chane-Ming, Christelle Barthe, Y. Kuleshov
    Abstract:

    Tropical cyclone (TC) activity is diagnosed through convective gravity waves (GWs) observed in the upper troposphere (UT)/lower stratosphere (LS) above Tromelin island (15.53°S, 54.31°E) in the tropical southwest Indian Ocean. Monthly and weekly GW Total Energy densities derived from daily GPS windsonde data are compared with Outgoing Longwave Radiation (OLR) and TC hours in the vicinity of Tromelin. A relationship between GW Energy Density and TC activity is observed in the LS, for the TC season 2001/2002. Moreover TCs (local convection) produce GWs with Total Energy Density mostly higher (lower) than 12 J kg−1. A 10-season climatology (1997/1998-2006/2007) confirms that large values of GW Total Energy Density in the LS are associated with weak values of OLR during the TC passage. Monthly Total, kinetic and potential GW Energy densities within 2000 km radius of Tromelin can be estimated using linear relationships with TC hours for a threshold of above 6 TC days per month. A linear relationship also exists between weekly GW Total Energy Density in the LS and the activity of intense TCs above a threshold of 2 TC days per week within 1000 km radius of Tromelin. GW Energy Density in the LS could be used as a possible index to investigate TC activity in the UT/LS.

  • Estimation of the West African Monsoon variability through the analyses of the induced wave parameters
    2015
    Co-Authors: P. Kafando, Fabrice Chane-Ming, Monique Petitdidier
    Abstract:

    Using local (rainfall data) and global satellite observations (atmospheric fields reanalysis, OLR data, satellite- observed brightness temperature data and cloud cluster data), the activity of convective equatorial waves revealed to be strongly coupled with the West african Monsoon (WaM) variability. a previous study of wave activity in the West african area (Kafando et al., 2008), revealed that the signature of the monsoon is clearly observed on Total Energy Density in the lower stratosphere (19-23km). the annual cycle and the climatology of wave Total Energy Density showed that peaks of activity match the period of intense convection. in the present study, wave activity in relation with monsoon proxies (convection and precipitations) has been used to analyze the WaM interannual variability using nine years radiosonde observations, tropical rainfall Measuring Mission (trMM) data and Outgoing longwave radiation (Olr) data over several West african meteorological stations located in the latitudinal belt 4°n–20°n.

  • Latitudinal and seasonal variability of gravity-wave Energy in the South-West Indian Ocean
    Annales Geophysicae, 2008
    Co-Authors: Fabrice Chane-Ming, Denis Faduilhe, Jean Leveau
    Abstract:

    Vertical temperature profiles obtained by radiosonde and Raman lidar measurements are used to investigate a climatology of Total Energy Density of gravity waves (GW) in the Upper Troposphere (UT) and the Lower Stratosphere (LS) from 1992 to 2004 above Mahé (4° S, 55° E), Tromelin (15° S, 54° E) and La Réunion (21° S, 55° E) located in the tropical South-West Indian Ocean. The commonly used spectral index value (p˜5/3) of the intrinsic frequency spectrum is used for calculating estimated Total Energy Density in the UT and LS. Estimated Total Energy Density provides good estimation of Total Energy Density in the LS but underestimates Total Energy Density by one half in the UT above Mahé and Tromelin probably due to the activity of near-inertial frequency waves. Estimated Total Energy Density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Réunion, a semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Raman lidar provide consistent GW surveys in the UT/LS at heights

  • Climatology of gravity wave activity during the West African Monsoon
    Annales Geophysicae, 2008
    Co-Authors: P. Kafando, Fabrice Chane-Ming, Monique Petitdidier
    Abstract:

    Gravity wave activity is analysed in the lower stratosphere using 6 year radiosonde data (2001–2006) above two meteorological stations in the West African tropical region such as Niamey (13.47° N; 2.16° E) and Ouagadougou (12.35° N; 1.51° W). Monthly Total Energy Density of gravity waves is computed with temperature and horizontal wind perturbations to highlight the West African Monsoon period from June to September. Comparison with monthly Total Energy Density calculated with temperature only supports that observed small-scale temperature and wind perturbations are mostly associated with gravity waves in the lower stratosphere especially for large values during the wet season. Above the two sites, monthly evolution of gravity wave Total Energy Density reveals a maximum intensity of gravity wave activity in July during the West African Monsoon period. Indicators of convective activity such as mean Outgoing Longwave Radiation (OLR) and Tropical Rainfall Measuring Mission (TRMM) rain rates reveal to be adequate monsoon proxies to be compared to gravity wave Energy intensity during the West African Monsoon.

  • Latitudinal and seasonal variability of gravity-wave Energy in the South-West Indian Ocean
    Annales Geophysicae, 2007
    Co-Authors: Fabrice Chane-Ming, Denis Faduilhe, Jean Leveau
    Abstract:

    Vertical temperature profiles obtained by ra- diosonde and Raman lidar measurements are used to inves- tigate a climatology of Total Energy Density of gravity waves (GW) in the Upper Troposphere (UT) and the Lower Strato- sphere (LS) from 1992 to 2004 above Mah´ e (4 S, 55 E), Tromelin (15 S, 54 E) and La R´ (21 S, 55 E) lo- cated in the tropical South-West Indian Ocean. The com- monly used spectral index value (p 5/3) of the intrinsic fre- quency spectrum is used for calculating estimated Total en- ergy Density in the UT and LS. Estimated Total Energy den- sity provides good estimation of Total Energy Density in the LS but underestimates Total Energy Density by one half in the UT above Mah´ e and Tromelin probably due to the activity of near-inertial frequency waves. Estimated Total Energy Density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Ra semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Ra- man lidar provide consistent GW surveys in the UT/LS at heights

Samuel D. Mcdermott - One of the best experts on this subject based on the ideXlab platform.

  • Dark radiation and superheavy dark matter from black hole domination
    Journal of High Energy Physics, 2019
    Co-Authors: Dan Hooper, Gordan Krnjaic, Samuel D. Mcdermott
    Abstract:

    If even a relatively small number of black holes were created in the early universe, they will constitute an increasingly large fraction of the Total Energy Density as space expands. It is thus well-motivated to consider scenarios in which the early universe included an era in which primordial black holes dominated the Total Energy Density. Within this context, we consider Hawking radiation as a mechanism to produce both dark radiation and dark matter. If the early universe included a black hole dominated era, we find that Hawking radiation will produce dark radiation at a level Δ N _eff ∼ 0 . 03 − 0 . 2 for each light and decoupled species of spin 0, 1/2, or 1. This range is well suited to relax the tension between late and early-time Hubble determinations, and is within the reach of upcoming CMB experiments. The dark matter could also originate as Hawking radiation in a black hole dominated early universe, although such dark matter candidates must be very heavy ( m _DM ≳ 10^11 GeV) if they are to avoid exceeding the measured abundance.

  • Dark Radiation and Superheavy Dark Matter from Black Hole Domination.
    Journal of High Energy Physics, 2019
    Co-Authors: Dan Hooper, Gordan Krnjaic, Samuel D. Mcdermott
    Abstract:

    If even a relatively small number of black holes were created in the early universe, they will constitute an increasingly large fraction of the Total Energy Density as space expands. It is thus well-motivated to consider scenarios in which the early universe included an era in which primordial black holes dominated the Total Energy Density. Within this context, we consider Hawking radiation as a mechanism to produce both dark radiation and dark matter. If the early universe included a black hole dominated era, we find that Hawking radiation will produce dark radiation at a level $\Delta N_{\rm eff} \sim 0.03-0.2$ for each light and decoupled species of spin 0, 1/2, or 1. This range is well suited to relax the tension between late and early-time Hubble determinations, and is within the reach of upcoming CMB experiments. The dark matter could also originate as Hawking radiation in a black hole dominated early universe, although such dark matter candidates must be very heavy ($m_{\rm DM} >10^{11}$ GeV) if they are to avoid exceeding the measured abundance.

E Engel - One of the best experts on this subject based on the ideXlab platform.

  • Total Energy Density as an interpretative tool
    The Journal of Chemical Physics, 2000
    Co-Authors: Morrel H Cohen, Derek Frydel, Kieron Burke, E Engel
    Abstract:

    We present a formulation for the Total-Energy Density within Density-functional theory which is physically transparent and computationally feasible. We propose that it be used as a tool for the interpretation of computed Energy and electronic structure changes during structural transformations and chemical reactions, augmenting the present use of changes in the electron Density, in the Kohn–Sham local Density of states, and in the Kohn–Sham Energy Density.

  • Total Energy Density as an interpretative tool
    arXiv: Materials Science, 1999
    Co-Authors: Morrel H Cohen, Derek Frydel, Kieron Burke, E Engel
    Abstract:

    We present an unambiguous formulation for the Total Energy Density within Density-functional theory. We propose that it be used as a tool for the interpretation of computed Energy and electronic structure changes during structural transformations and chemical reactions, augmenting the present use of electron Density changes and changes in the Kohn-Sham local Density of states and Kohn-Sham Energy Density.

Y. Kuleshov - One of the best experts on this subject based on the ideXlab platform.

  • Diagnosis of tropical cyclone activity through gravity wave Energy Density in the southwest Indian Ocean
    Geophysical Research Letters, 2016
    Co-Authors: C. Ibrahim, Fabrice Chane-Ming, Christelle Barthe, Y. Kuleshov
    Abstract:

    Tropical cyclone (TC) activity is diagnosed through convective gravity waves (GWs) observed in the upper troposphere (UT)/lower stratosphere (LS) above Tromelin island (15.53°S, 54.31°E) in the tropical southwest Indian Ocean. Monthly and weekly GW Total Energy densities derived from daily GPS windsonde data are compared with Outgoing Longwave Radiation (OLR) and TC hours in the vicinity of Tromelin. A relationship between GW Energy Density and TC activity is observed in the LS, for the TC season 2001/2002. Moreover TCs (local convection) produce GWs with Total Energy Density mostly higher (lower) than 12 J kg−1. A 10-season climatology (1997/1998-2006/2007) confirms that large values of GW Total Energy Density in the LS are associated with weak values of OLR during the TC passage. Monthly Total, kinetic and potential GW Energy densities within 2000 km radius of Tromelin can be estimated using linear relationships with TC hours for a threshold of above 6 TC days per month. A linear relationship also exists between weekly GW Total Energy Density in the LS and the activity of intense TCs above a threshold of 2 TC days per week within 1000 km radius of Tromelin. GW Energy Density in the LS could be used as a possible index to investigate TC activity in the UT/LS.

Jean Leveau - One of the best experts on this subject based on the ideXlab platform.

  • Latitudinal and seasonal variability of gravity-wave Energy in the South-West Indian Ocean
    Annales Geophysicae, 2008
    Co-Authors: Fabrice Chane-Ming, Denis Faduilhe, Jean Leveau
    Abstract:

    Vertical temperature profiles obtained by radiosonde and Raman lidar measurements are used to investigate a climatology of Total Energy Density of gravity waves (GW) in the Upper Troposphere (UT) and the Lower Stratosphere (LS) from 1992 to 2004 above Mahé (4° S, 55° E), Tromelin (15° S, 54° E) and La Réunion (21° S, 55° E) located in the tropical South-West Indian Ocean. The commonly used spectral index value (p˜5/3) of the intrinsic frequency spectrum is used for calculating estimated Total Energy Density in the UT and LS. Estimated Total Energy Density provides good estimation of Total Energy Density in the LS but underestimates Total Energy Density by one half in the UT above Mahé and Tromelin probably due to the activity of near-inertial frequency waves. Estimated Total Energy Density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Réunion, a semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Raman lidar provide consistent GW surveys in the UT/LS at heights

  • Latitudinal and seasonal variability of gravity-wave Energy in the South-West Indian Ocean
    Annales Geophysicae, 2007
    Co-Authors: Fabrice Chane-Ming, Denis Faduilhe, Jean Leveau
    Abstract:

    Vertical temperature profiles obtained by ra- diosonde and Raman lidar measurements are used to inves- tigate a climatology of Total Energy Density of gravity waves (GW) in the Upper Troposphere (UT) and the Lower Strato- sphere (LS) from 1992 to 2004 above Mah´ e (4 S, 55 E), Tromelin (15 S, 54 E) and La R´ (21 S, 55 E) lo- cated in the tropical South-West Indian Ocean. The com- monly used spectral index value (p 5/3) of the intrinsic fre- quency spectrum is used for calculating estimated Total en- ergy Density in the UT and LS. Estimated Total Energy den- sity provides good estimation of Total Energy Density in the LS but underestimates Total Energy Density by one half in the UT above Mah´ e and Tromelin probably due to the activity of near-inertial frequency waves. Estimated Total Energy Density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Ra semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Ra- man lidar provide consistent GW surveys in the UT/LS at heights