A lightning climatology of the South-West Indian Ocean

Bovalo, Christophe; Barthe, Christelle; Bègue, Nelson

doi:10.5194/nhess-12-2659-2012

Cited by 39 publications

(31 citation statements)

References 63 publications

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“…Although few studies have examined the interdependency of the Mascarene High and MJO, Pohl et al (2009) an intraseasonal modulation of the Mascarene High and MJO by applying a principal component analysis. The variations in the environmental conditions and convection during P1 and P2 are consistent with a previous study showing that the Mascarene High generally inhibits convection owing to the trade inversion (Bovalo et al 2012). During the mature period of P4, a strong extratropical cyclone appears to the south of 20°S, and its appearance is synchronized with the local minimum pressure of less than 1008 hPa in the equatorial region and the intensification of the MJO convection (Fig.…”

Section: Large-scale Environmental Conditions Aroundsupporting

confidence: 90%

Equatorially Antisymmetric Features in the Initiation Processes of the Madden-Julian Oscillation Observed in Late October during CINDY2011

Moteki

2015

Journal of the Meteorological Society of Japan

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In this study, we investigated the equatorially antisymmetric features in the initiation processes of the MaddenJulian oscillation (MJO) event in late October during the cooperative Indian Ocean experiment on intraseasonal variability in the year 2011. This MJO event developed when the thermal equator was drastically shifted from the Northern Hemisphere to the equator from September to October as the Mascarene High over the southern Indian Ocean decayed and shifted southward. The large-scale fields of sea level pressure, temperature, and moisture around the MJO exhibited equatorially antisymmetric features. According to their different features in terms of surface convergence, temperature, and moisture, MJO convection over the Indian Ocean after its onset consisted of four distinct convective components: the southern intertropical convergence zone between 10°S and 0° along the meridional sea surface temperature (SST) gradients (s-ITCZ), the northern-ITCZ at the southern edge of the high SST above 29°C over the Bay of Bengal, the vortex disturbance over the Arabian Sea (VDAS) in association with the zonal SST gradients, and the westward-propagating diurnal convection originating from Sumatra. In particular, the double-ITCZ and VDAS were characterized by a steady, low-level convergence zone along the surface potential temperature gradients forced by the SST. Before the onset of the MJO convection, the double-ITCZ was characterized by cross-equatorial vertical circulation that was baroclinically tilted northward, and s-ITCZ convection was inhibited owing to the strong Mascarene High. After the onset, single, larger-scale upward motion was barotropically formed over the equator because of the equatorward shift of the double-ITCZ. Such changes in the equatorially antisymmetric meridional circulation are relevant for the organization of the MJO convection.

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Section: Large-scale Environmental Conditions Aroundsupporting

confidence: 90%

Equatorially Antisymmetric Features in the Initiation Processes of the Madden-Julian Oscillation Observed in Late October during CINDY2011

Moteki

2015

Journal of the Meteorological Society of Japan

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“…For the Atlantic respectively East Pacific) basin, the DEs ranged from 2.6% (respectively 0.9%) in 2005 to 20% (respectively 17.5%) in 2010. [ Bovalo et al , ] used the same method but found a smaller increase of the DE in the SWIO basin: from 2.0% in 2005 to 10.9% in 2013.…”

Section: Methodsmentioning

confidence: 99%

Lightning activity within tropical cyclones in the South West Indian Ocean

Bovalo

Barthe

Yang

et al. 2014

J. Geophys. Res. Atmos.

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Lightning activity within 70 tropical cyclones in the South West Indian Ocean is studied using a large data set (2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013) provided by the World Wide Lightning Location Network (WWLLN). The radial and azimuthal distributions of lightning flashes are analyzed in three different regions of the basin: the open ocean, the Mozambique Channel, and the oceanic region up to 400 km off the eastern coast of Madagascar (ECM). Over the open ocean, lightning activity detected by the WWLLN is mainly found in the eyewall and decreases outward, regardless of storm intensity. Lightning activity in the eyewall of tropical cyclones is higher than in the eyewall of tropical storms. The front and the right quadrants (225 • to 45 • ) relative to the storm motion are the regions where lightning flashes are preferentially detected. Near the ECM, lightning density in the eyewall, the inner rainbands, and the outer rainbands is quite similar, presumably owing to the proximity of land. When the system reaches tropical cyclone strength, lightning activity is mainly found in the left and rear quadrants relative to storm motion. In the Mozambique Channel, the radial and azimuthal distributions of lightning flashes are complex due to the geographical configuration of this subdomain. The relationships between lightning activity and intensity change have also been investigated for systems over the open ocean. The proportion of periods with lightning activity is higher during rapid intensity changes of tropical cyclones. During tropical storm stage, lightning activity in the outer rainbands starts increasing 18 h before a rapid intensification period.

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“…() have shown that precipitating convective systems on the African coast are mainly associated with the ITCZ, but are also influenced by local factors (orography, presence of lakes, oceanic influence) and by the southeasterly trade winds associated with the variability of the Mascarene High (Figure ). These two regions of strong deep convective activity also correspond to the location of the maximum lightning activity in the southwest Indian Ocean (Bovalo et al ., ), at (8°S–16°S; 35°E–40°E) and at (12°S–20°S; 45°E–50°E).…”

Section: Seasonal Cloud Distribution Over the Southwest Indian Oceanmentioning

confidence: 97%

Spatial and seasonal variability of clouds over the southwest Indian Ocean based on the DARDAR mask product

Vérèmes

Listowski

Delanoë

et al. 2019

Quart J Royal Meteoro Soc

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We present a characterization of the variability of clouds over the southwest Indian Ocean between 2007 and 2010. Cloud occurrence is derived from the DARDAR (raDAR/liDAR) mask, a synergistic product based on Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat measurements. It provides a target classification for hydrometeors. We demonstrate that this product is suitable for studying the vertical, spatial and seasonal cloud distribution in the southwest Indian Ocean. The variability of cloud occurrence increases approaching the tropics: the average maximum amplitude of monthly occurrence is ∼7% between 30°S and 60°S and ∼14% between 10°S and 30°S. The 10–30°S latitudinal band exhibits the largest contrasts: summer (winter) total cloud occurrence is mainly driven by high‐ (low‐) level clouds. The vertical distribution of clouds differs on either side of 55°E and this is related to a land–ocean contrast and to large‐scale influence. In winter, east of 55°E, the maximum of cloud occurrence corresponds to warm and mixed‐phased precipitating clouds associated with the Mascarene High. In summer, west of 55°E, the vertical distribution of cloud occurrence is driven by deep convection associated with the InterTropical Convergence Zone and the Near Equatorial Trough. The vertical distribution of cloud occurrence shows an interannual variability that is related to El Niño events. The influence of other oscillation modes should be further investigated.

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A lightning climatology of the South-West Indian Ocean

Cited by 39 publications

References 63 publications

Equatorially Antisymmetric Features in the Initiation Processes of the Madden-Julian Oscillation Observed in Late October during CINDY2011

Equatorially Antisymmetric Features in the Initiation Processes of the Madden-Julian Oscillation Observed in Late October during CINDY2011

Lightning activity within tropical cyclones in the South West Indian Ocean

Spatial and seasonal variability of clouds over the southwest Indian Ocean based on the DARDAR mask product

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