scholarly journals Interannual variability of the carbon dioxide system in the southern Indian Ocean (20°S-60°S): The impact of a warm anomaly in austral summer 1998

2004 ◽  
Vol 18 (1) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. Jabaud-Jan ◽  
N. Metzl ◽  
C. Brunet ◽  
A. Poisson ◽  
B. Schauer
Keyword(s):  
Carbon Dioxide ◽  
Indian Ocean ◽  
Interannual Variability ◽  
Austral Summer ◽  
Southern Indian Ocean ◽  
Warm Anomaly ◽  
The Impact

scholarly journals Effect of deep convection on the tropical tropopause layer composition over the southwest Indian Ocean during austral summer

2020 ◽  
Vol 20 (17) ◽  
pp. 10565-10586
Author(s):  
Stephanie Evan ◽  
Jerome Brioude ◽  
Karen Rosenlof ◽  
Sean M. Davis ◽  
Holger Vömel ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Austral Summer ◽  
Lagrangian Model ◽  
Southwest Indian Ocean ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Tropopause Region ◽  
The Impact

Abstract. Balloon-borne measurements of cryogenic frost-point hygrometer (CFH) water vapor, ozone and temperature and water vapor lidar measurements from the Maïdo Observatory on Réunion Island in the southwest Indian Ocean (SWIO) were used to study tropical cyclones' influence on tropical tropopause layer (TTL) composition. The balloon launches were specifically planned using a Lagrangian model and Meteosat-7 infrared images to sample the convective outflow from tropical storm (TS) Corentin on 25 January 2016 and tropical cyclone (TC) Enawo on 3 March 2017. Comparing the CFH profile to Aura's Microwave Limb Sounder's (MLS) monthly climatologies, water vapor anomalies were identified. Positive anomalies of water vapor and temperature, and negative anomalies of ozone between 12 and 15 km in altitude (247 to 121 hPa), originated from convectively active regions of TS Corentin and TC Enawo 1 d before the planned balloon launches according to the Lagrangian trajectories. Near the tropopause region, air masses on 25 January 2016 were anomalously dry around 100 hPa and were traced back to TS Corentin's active convective region where cirrus clouds and deep convective clouds may have dried the layer. An anomalously wet layer around 68 hPa was traced back to the southeast Indian Ocean where a monthly water vapor anomaly of 0.5 ppmv was observed. In contrast, no water vapor anomaly was found near or above the tropopause region on 3 March 2017 over Maïdo as the tropopause region was not downwind of TC Enawo. This study compares and contrasts the impact of two tropical cyclones on the humidification of the TTL over the SWIO. It also demonstrates the need for accurate balloon-borne measurements of water vapor, ozone and aerosols in regions where TTL in situ observations are sparse.

scholarly journals The South Atlantic–South Indian Ocean Pattern: a Zonally Oriented Teleconnection along the Southern Hemisphere Westerly Jet in Austral Summer

Atmosphere ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 259 ◽  
Author(s):  
Zhongda Lin
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Southern Hemisphere ◽  
Austral Summer ◽  
South Atlantic ◽  
The South ◽  
South Indian Ocean ◽  
Westerly Jet ◽  
South Indian ◽  
Zonal Wavenumber

Extratropical teleconnections significantly affect the climate in subtropical and mid-latitude regions. Understanding the variability of atmospheric teleconnection in the Southern Hemisphere, however, is still limited in contrast with the well-documented counterpart in the Northern Hemisphere. This study investigates the interannual variability of mid-latitude circulation in the Southern Hemisphere in austral summer based on the ERA-Interim reanalysis dataset during 1980–2016. A stationary mid-latitude teleconnection is revealed along the strong Southern Hemisphere westerly jet over the South Atlantic and South Indian Ocean (SAIO). The zonally oriented SAIO pattern represents the first EOF mode of interannual variability of meridional winds at 200 hPa over the region, with a vertical barotropic structure and a zonal wavenumber of 4. It significantly modulates interannual climate variations in the subtropical Southern Hemisphere in austral summer, especially the opposite change in rainfall and surface air temperature between Northwest and Southeast Australia. The SAIO pattern can be efficiently triggered by divergences over mid-latitude South America and the southwest South Atlantic, near the entrance of the westerly jet, which is probably related to the zonal shift of the South Atlantic Convergence Zone. The triggered wave train is then trapped within the Southern Hemisphere westerly jet waveguide and propagates eastward until it diverts northeastward towards Australia at the jet exit, in addition to portion of which curving equatorward at approximately 50° E towards the southwest Indian Ocean.

scholarly journals Effect of deep convection on the TTL composition over the Southwest Indian Ocean during austral summer

2020 ◽  
Author(s):  
Stephanie Evan ◽  
Jerome Brioude ◽  
Karen Rosenlof ◽  
Sean M. Davis ◽  
Hölger Vömel ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Deep Convection ◽  
Austral Summer ◽  
Active Regions ◽  
Lagrangian Model ◽  
Southwest Indian Ocean ◽  
Tropopause Region ◽  
The Impact

Abstract. Balloon-borne measurements of CFH water vapor, ozone and temperature and water vapor lidar measurements from the Maïdo Observatory at Réunion Island in the Southwest Indian Ocean (SWIO) were used to study tropical cyclones' influence on TTL composition. The balloon launches were specifically planned using a Lagrangian model and METEOSAT 7 infrared images to sample the convective outflow from Tropical Storm (TS) Corentin on 25 January 2016 and Tropical Cyclone (TC) Enawo on 3 March 2017. Comparing CFH profile to MLS monthly climatologies, water vapor anomalies were identified. Positive anomalies of water vapor and temperature, and negative anomalies of ozone between 12 and 15 km in altitude (247 to 121 hPa) originated from convectively active regions of TS Corentin and TC Enawo, one day before the planned balloon launches, according to the Lagrangian trajectories. Near the tropopause region, air masses on 25 January 2016 were anomalously dry around 100 hPa and were traced back to TS Corentin active convective region where cirrus clouds and deep convective clouds may have dried the layer. An anomalously wet layer around 68 hPa was traced back to the South East IO where a monthly water vapor anomaly of 0.5 ppbv was observed. In contrast, no water vapor anomaly was found near or above the tropopause region on 3 March 2017 over Maïdo as the tropopause region was not downwind of TC Enawo. This study compares and contrasts the impact of two tropical cyclones on the humidification of the TTL over the Southwest Indian Ocean.

The impact of SST front on the surface wind in the southern Indian Ocean

2020 ◽  
Author(s):  
Xuhua Cheng
Keyword(s):  
Indian Ocean ◽  
Deep Convection ◽  
Surface Wind ◽  
Polar Front ◽  
Open Ocean ◽  
Heat Fluxes ◽  
Southern Indian Ocean ◽  
Sst Front ◽  
Microwave Imager ◽  
The Impact

<p><span> </span>Using 28-year satellite-borne Special Sensor Microwave Imager observations, features of high-wind frequency (HWF) over</p><p>the southern Indian Ocean are investigated. Climatology maps show that high winds occur frequently during austral winter,</p><p>located in the open ocean south of Polar Front in subpolar region, warm flank of the Subantarctic Front between 55<sup>o</sup>E-78<sup>o</sup>E, </p><p>and south of Cape Agulhas, where westerly wind prevails. The strong instability of marine atmospheric boundary layer</p><p>accompanied by increased sensible and latent heat fluxes on the warmer flank acts to enhance the vertical momentum mixing,</p><p>thus accelerate the surface winds. Effects of sea surface temperature (SST) front can even reach the entire troposphere</p><p>by deep convection. HWF also shows distinct interannual variability, which is associated with the Southern Annual Mode</p><p>(SAM). During positive phase of the SAM, HWF has positive anomalies over the open ocean south of Polar Front, while</p><p>has negative anomalies north of the SST front. A phase shift of HWF happened around 2001, which is likely related to the</p><p>reduction of storm tracks and poleward shift of westerly winds in the Southern Hemisphere.</p>

scholarly journals A Tropospheric ozone maximum over the equatorial southern Indian Ocean

2012 ◽  
Vol 12 (1) ◽  
pp. 1979-2024
Author(s):  
L. Zhang ◽  
Q. B. Li ◽  
L. T. Murray ◽  
M. Luo ◽  
H. Liu ◽  
...  
Keyword(s):  
Indian Ocean ◽  
South America ◽  
Interannual Variability ◽  
Tropospheric Ozone ◽  
Three Dimensional ◽  
Central Africa ◽  
Tropospheric Chemistry ◽  
Southern Indian Ocean ◽  
Three Dimensional Model ◽  
Dynamic Factors

Abstract. We examine the distribution of tropical tropospheric ozone (O3) from the Microwave Limb Sounder (MLS) and the Tropospheric Emission Spectrometer (TES) by using a global three-dimensional model of tropospheric chemistry (GEOS-Chem). MLS and TES observations of tropospheric O3 during 2005 to 2009 reveal a distinct, persistent O3 maximum, both in mixing ratio and tropospheric column, in May over the Equatorial Southern Indian Ocean (ESIO). The maximum is most pronounced in 2006 and 2008 and less evident in the other three years. This feature is also consistent with the total column O3 observations from the Ozone Mapping Instrument (OMI) and the Atmospheric Infrared Sounder (AIRS). Model results reproduce the observed May O3 maximum and the associated interannual variability. The origin of the maximum reflects a complex interplay of chemical and dynamic factors. The O3 maximum is dominated by the O3 production driven by lightning nitrogen oxides (NOx) emissions, which accounts for 62% of the tropospheric column O3 in May 2006. We find the contribution from biomass burning, soil, anthropogenic and biogenic sources to the O3 maximum are rather small. The O3 productions in the lightning outflow from Central Africa and South America both peak in May and are directly responsible for the O3 maximum over the western ESIO. The lightning outflow from Equatorial Asia dominates over the eastern ESIO. The interannual variability of the O3 maximum is driven largely by the anomalous anti-cyclones over the southern Indian Ocean in May of 2006 and 2008. The lightning outflow from Central Africa and South America is effectively entrained by the anti-cyclones followed by northward transport to the ESIO.

Interannual changes of austral summer coccolithophore assemblages and southward expanse in the Southern Indian Ocean

2020 ◽  
Vol 178 ◽  
pp. 104765 ◽  
Author(s):  
Shramik M. Patil ◽  
Rahul Mohan ◽  
Suhas S. Shetye ◽  
Sahina Gazi ◽  
Pallavi Choudhari ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Austral Summer ◽  
Southern Indian Ocean
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