Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

Chane-Ming, Fabrice; Faduilhe, Denis; Leveau, Jean

doi:10.5194/angeo-25-2479-2007

Cited by 7 publications

(8 citation statements)

References 28 publications

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“…Vertical profiles of temperature and horizontal wind with 100 m resolution reached the mean altitude of 23 km. Radiosonde data quality and accuracy are described in Chane Ming et al ( , 2007 and Ibrahim (2010), which used similar vertical profiles to characterize GWs in the UT/LS. At Ivato airport (389 m altitude), 40 GPS radiosonde profiles were obtained twice a day at 00:00 and/or 09:00 and/or 12:00 UTC with a vertical resolution of 300 m and a mean maximum altitude of 23 km.…”

Section: Methodsmentioning

confidence: 99%

Observation and a numerical study of gravity waves during tropical cyclone Ivan (2008)

et al. 2014

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Abstract. Gravity waves (GWs) with horizontal wavelengths of 32-2000 km are investigated during tropical cyclone (TC) Ivan (2008) in the southwest Indian Ocean in the upper troposphere (UT) and the lower stratosphere (LS) using observational data sets, radiosonde and GPS radio occultation data, ECMWF analyses and simulations of the French numerical model Meso-NH with vertical resolution < 150 m near the surface and 500 m in the UT/LS. Observations reveal dominant low-frequency GWs with short vertical wavelengths of 0.7-3 km, horizontal wavelengths of 80-400 km and periods of 4.6-13 h in the UT/LS. Continuous wavelet transform and image-processing tools highlight a wide spectrum of GWs with horizontal wavelengths of 40-1800 km, short vertical wavelengths of 0.6-3.3 km and periods of 20 min-2 days from modelling analyses. Both ECMWF and Meso-NH analyses are consistent with radiosonde and GPS radio occultation data, showing evidence of a dominant TCrelated quasi-inertia GW propagating eastward east of TC Ivan with horizontal and vertical wavelengths of 400-800 km and 2-3 km respectively in the LS, more intense during TC intensification. In addition, the Meso-NH model produces a realistic, detailed description of TC dynamics, some highfrequency GWs near the TC eye, variability of the tropospheric and stratospheric background wind and TC rainband characteristics at different stages of TC Ivan. A wave number 1 vortex Rossby wave is suggested as a source of dominant inertia GW with horizontal wavelengths of 400-800 km, while shorter scale modes (100-200 km) located at northeast and southeast of the TC could be attributed to strong localized convection in spiral bands resulting from wave number 2 vortex Rossby waves. Meso-NH simulations also reveal GWrelated clouds east of TC Ivan.

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Section: Methodsmentioning

confidence: 99%

Observation and a numerical study of gravity waves during tropical cyclone Ivan (2008)

et al. 2014

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“…This observation could be related to the increase in convective activity in the southwestern Indian Ocean (SWIO) basin during this period. It is well known that low-pressure and tropical cyclone systems are a source of low-frequency convective gravity waves in the SWIO basin (Chane-Ming et al, 2007Ibrahim et al, 2010). Based on a 10-season climatology investigation (1997/1998-2006/2007) obtained from GPS windsonde, Ibrahim et al (2010) showed a linear relationship between weekly gravity waves total energy density in the lower stratosphere and the activity of intense tropical cyclones in the SWIO basin.…”

Section: Statistical Analysis Of Temperature Inversion Layermentioning

confidence: 99%

Statistical analysis of the mesospheric inversion layers over two symmetrical tropical sites: Réunion (20.8° S, 55.5° E) and Mauna Loa (19.5° N, 155.6° W)

et al. 2017

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Abstract. In this investigation a statistical analysis of the characteristics of mesospheric inversion layers (MILs) over tropical regions is presented. This study involves the analysis of 16 years of lidar observations recorded at Réunion (20.8° S, 55.5° E) and 21 years of lidar observations recorded at Mauna Loa (19.5° N, 155.6° W) together with SABER observations at these two locations. MILs appear in 10 and 9.3 % of the observed temperature profiles recorded by Rayleigh lidar at Réunion and Mauna Loa, respectively. The parameters defining MILs show a semi-annual cycle over the two selected sites with maxima occurring near the equinoxes and minima occurring during the solstices. Over both sites, the maximum mean amplitude is observed in April and October, and this corresponds to a value greater than 35 K. According to lidar observations, the maximum and minimum mean of the base height ranged from 79 to 80.5 km and from 76 to 77.5 km, respectively. The MILs at Réunion appear on average ∼ 1 km thinner and ∼ 1 km lower, with an amplitude of ∼ 2 K higher than Mauna Loa. Generally, the statistical results for these two tropical locations as presented in this investigation are in fairly good agreement with previous studies. When compared to lidar measurements, on average SABER observations show MILs with greater amplitude, thickness and base altitudes of 4 K, 0.75 and 1.1 km, respectively. Taking into account the temperature error by SABER in the mesosphere, it can therefore be concluded that the measurements obtained from lidar and SABER observations are in significant agreement. The frequency spectrum analysis based on the lidar profiles and the 60-day averaged profile from SABER confirms the presence of the semi-annual oscillation where the magnitude maximum is found to coincide with the height range of the temperature inversion zone. This connection between increases in the semi-annual component close to the inversion zone is in agreement with most previously reported studies over tropics based on satellite observations. Results presented in this study confirm through the use of the ground-based Rayleigh lidar at Réunion and Mauna Loa that the semi-annual oscillation contributes to the formation of MILs over the tropical region.

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“…Recently, Chane‐Ming et al [2010] revealed a clear correlation between the daily maximum surface wind speed and the total energy density of low frequency GWs produced by intense TCs Dina and Faxai in the upper troposphere (UT)/lower stratosphere (LS). Among others, a positive contribution in total energy density of about 30% in the LS was quantified above Tromelin during intense TC Dina as compared with climatology in austral summer [ Chane‐Ming et al , 2007].…”

Section: Introductionmentioning

confidence: 99%

Diagnosis of tropical cyclone activity through gravity wave energy density in the southwest Indian Ocean

Ibrahim

Chane-Ming

Barthe

et al. 2010

Geophysical Research Letters

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[1] 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. Citation: Ibrahim, C., F. Chane-Ming, C. Barthe, and Y. Kuleshov (2010), Diagnosis of tropical cyclone activity through gravity wave energy density in the southwest Indian Ocean, Geophys. Res. Lett., 37, L09807,

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Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

Cited by 7 publications

References 28 publications

Observation and a numerical study of gravity waves during tropical cyclone Ivan (2008)

Observation and a numerical study of gravity waves during tropical cyclone Ivan (2008)

Statistical analysis of the mesospheric inversion layers over two symmetrical tropical sites: Réunion (20.8° S, 55.5° E) and Mauna Loa (19.5° N, 155.6° W)

Diagnosis of tropical cyclone activity through gravity wave energy density in the southwest Indian Ocean

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Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

Cited by 7 publications

References 28 publications

Observation and a numerical study of gravity waves during tropical cyclone Ivan (2008)

Observation and a numerical study of gravity waves during tropical cyclone Ivan (2008)

Statistical analysis of the mesospheric inversion layers over two symmetrical tropical sites: Réunion (20.8° S, 55.5° E) and Mauna Loa (19.5° N, 155.6° W)

Diagnosis of tropical cyclone activity through gravity wave energy density in the southwest Indian Ocean

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Statistical analysis of the mesospheric inversion layers over two symmetrical tropical sites: Réunion (20.8° S, 55.5° E) and Mauna Loa (19.5° N, 155.6° W)