scholarly journals Thermodynamic structure of the Atmospheric Boundary Layer over the Arabian Sea and the Indian Ocean during pre-INDOEX and INDOEX-FFP campaigns

2004 ◽  
Vol 22 (8) ◽  
pp. 2679-2691 ◽  
Author(s):  
M. V. Ramana ◽  
P. Krishnan ◽  
S. Muraleedharan Nair ◽  
P. K. Kunhikrishnan
Keyword(s):  
Boundary Layer ◽  
Indian Ocean ◽  
Atmospheric Boundary Layer ◽  
Mixed Layer ◽  
Arabian Sea ◽  
Trade Wind ◽  
Back Trajectory ◽  
Spatial And Temporal Variability ◽  
Air Mass ◽  
The Indian Ocean

Abstract. Spatial and temporal variability of the Marine Atmospheric Boundary Layer (MABL) height for the Indian Ocean Experiment (INDOEX) study period are examined using the data collected through Cross-chained LORAN (Long-Range Aid to Navigation) Atmospheric Sounding System (CLASS) launchings during the Northern Hemispheric winter monsoon period. This paper reports the results of the analyses of the data collected during the pre-INDOEX (1997) and the INDOEX-First Field Phase (FFP; 1998) in the latitude range 14°N to 20°S over the Arabian Sea and the Indian Ocean. Mixed layer heights are derived from thermodynamic profiles and they indicated the variability of heights ranging from 400m to 1100m during daytime depending upon the location. Mixed layer heights over the Indian Ocean are slightly higher during the INDOEX-FFP than the pre-INDOEX due to anomalous conditions prevailing during the INDOEX-FFP. The trade wind inversion height varied from 2.3km to 4.5km during the pre-INDOEX and from 0.4km to 2.5km during the INDOEX-FFP. Elevated plumes of polluted air (lofted aerosol plumes) above the marine boundary layer are observed from thermodynamic profiles of the lower troposphere during the INDOEX-FFP. These elevated plumes are examined using 5-day back trajectory analysis and show that one group of air mass travelled a long way from Saudi Arabia and Iran/Iraq through India before reaching the location of measurement, while the other air mass originates from India and the Bay of Bengal.

Spatio-temporal variability of the thermodynamic characteristics of the marine atmospheric boundary layer (MABL) over the Indian and Southern Ocean (15oN to 70oS)

2021 ◽  
Author(s):  
Neha Salim ◽  
Harilal B Menon ◽  
Nadimpally V P Kiran Kumar
Keyword(s):  
Boundary Layer ◽  
Indian Ocean ◽  
Southern Ocean ◽  
Atmospheric Boundary Layer ◽  
Mixed Layer ◽  
Hadley Cell ◽  
Trade Wind ◽  
Marine Atmospheric Boundary Layer ◽  
Deep Mixed Layer ◽  
The Tropics

<p>The study deals with the thermodynamic characterization of marine atmospheric boundary layer (MABL) prevailing over regions of Indian Ocean and Indian Ocean sector of Southern Ocean from 29 high-resolution radiosondes launched during the International Indian Ocean Expedition (IIOE-2) and Southern Ocean Expedition (SOE-9). IIOE-2 was conducted during December 2015 onboard ORV Sagar Nidhi during which 11 radiosondes were launched, whereas SOE-9 was conducted during January-March 2017 onboard MV SA Agulhas which had 18 radiosonde ascents. These observations spanned latitudes from ~15<sup>o</sup>N to 70<sup>o</sup>S having crossed three major atmospheric circulation cells: Hadley cell, Ferrell cell and Polar cell. In addition, crucial atmospheric mesoscale phenomena such as inter-tropical convergence zone (ITCZ), sub-tropical jet (STJ) and polar jet (PJ) were encountered along with several oceanic fronts. Analysis of thermodynamic structure of MABL showed large variability in the formation of atmospheric sub-layers such as surface layer, mixed layer, cloud layer and trade wind inversion layer within MABL. MABL height varied spatially from tropics and mid-latitudes (12<sup>o</sup>N to 50<sup>o</sup>S) to polar latitudes (60<sup>o</sup>S to 68<sup>o</sup>S). Deep mixed layer were found over the tropics and mid-latitudes (~700 m) while shallow mixed layer was observed over the polar latitudes (~200 m). Deep mixed layer over the tropics were attributed to intense convective mixing while shallow mixed layer over polar regions was attributed to limited convective overturning associated with negative radiation balance at the surface. Convection was negligible over mid-latitudes (43<sup>o</sup>S to 55<sup>o</sup>S) where most of the atmospheric mixing were forced by frontal systems where lifting of air mass was mechanically driven by high speed winds rather than by convection. The enhanced convection over the tropics was confirmed from higher values of convective available potential energy (CAPE > 1000 J/kg) and large negative values of convective inhibition energy (CINE < -50 J/kg). Over the mid-latitude region (43<sup>o</sup>S to 50<sup>o</sup>S), enhanced advection and detrainment of convection was evident with maximum values of BRN shear (~65 knots) and lowest CAPE (~4 J/kg). Over polar latitudes (~60<sup>o</sup>S to 68<sup>o</sup>S), minimum CAPE (~17 J/kg) and low BRN shear (~5 knots) was noticed, which indicated presence of stable boundary layer conditions. A mesoscale phenomenon (i.e., ITCZ) was witnessed at ~5.92<sup>o</sup>S with highest CAPE ~2535.17 J/kg which signifies large convective instability resulting in strong convective updraft aiding thunderstorm activity and moderate precipitation over ITCZ. Analysis of conserved variables (CVA) revealed formation of second mixed layer (SML) structure between 12<sup>o</sup>N and 40<sup>o</sup>S. However, south of 40<sup>o</sup>S this structure ceases. The characteristics of SML structure and the plausible causes for its existence are also investigated.  </p>

Variability of Mixed-Layer Heights over the Indian Ocean and Central Arabian Sea during INDOEX, IFP-99

2003 ◽  
Vol 107 (3) ◽  
pp. 683-695 ◽  
Author(s):  
D. Bala Subrahamanyam ◽  
Radhika Ramachandran ◽  
K. Sen Gupta ◽  
Tuhin K. Mandal
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
Arabian Sea ◽  
The Indian Ocean

scholarly journals The structure of the haze plume over the Indian Ocean during INDOEX: tracer simulations and LIDAR observations

2006 ◽  
Vol 6 (4) ◽  
pp. 907-923 ◽  
Author(s):  
G. Forêt ◽  
C. Flamant ◽  
S. Cautenet ◽  
J. Pelon ◽  
F. Minvielle ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Indian Ocean ◽  
Arabian Sea ◽  
Vertical Structure ◽  
Atmospheric Modeling ◽  
Airborne Lidar ◽  
Layer Depth ◽  
The Indian Ocean ◽  
Ground Based Lidar ◽  
Lidar Observations

Abstract. Three-dimensional, nested tracer simulations of a pollution plume originating from the Indian sub-continent over the Indian Ocean, in the framework of the Indian Ocean Experiment (INDOEX), between 5 and 9 March 1999, were performed with the Regional Atmospheric Modeling System (RAMS), to provide insight into the transport patterns of the pollutants, as well as to investigate the dynamical mechanisms controlling the vertical structure of the plume and its evolution in the vicinity of the Maldives Islands. Airborne and ground-based LIDAR observations of the structure of the haze plume made on 7 March 1999 were used to assess the quality of the simulations, as well as the impact of grid resolution on the vertical structure of the simulated plume. It is shown that, over the Arabian Sea, in the vicinity of the Maldives Islands, the pollutants composing the plume observed by the airborne LIDAR essentially originated from the city of Madras and that the vertical structure of the plume was controlled by the diurnal cycle of the continental boundary layer depth. A combination of tracer simulations and remote sensing observations (airborne LIDAR, ship-borne photometer, ground-based LIDAR in Goa) was used to analyse the diurnal evolution of the haze plume over the sea. We find evidence that the sea breeze circulation and orographic lifting taking place in the southern part of the Indian sub-continent during the daytime play a crucial role in the modulation of the continental boundary layer depth, and in turn, the haze plume depth. The eastward shift of the subtropical high from central India to the Bay of Bengal after 6 March lead to an increase in the tracer concentrations simulated over the Arabian Sea, in the region of intensive observations north of the Maldives, as transport pathways form Hyderabad and Madras were modified significantly. The nesting of a high horizontal resolution domain (5 km, with 39 vertical levels below 4000 m above mean seal level) allows for a better representation of local dynamics, the circulation of sea and mountains breezes, and therefore a noticeable improvement in the representation of the pollutants' plume in the simulation.

scholarly journals Evolution of the Distribution of Upper-Tropospheric Humidity over the Indian Ocean: Connection with Large-Scale Advection and Local Cloudiness

2017 ◽  
Vol 56 (7) ◽  
pp. 2035-2052 ◽  
Author(s):  
Thomas Garot ◽  
Hélène Brogniez ◽  
Renaud Fallourd ◽  
Nicolas Viltard
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Transport Model ◽  
Intraseasonal Variability ◽  
Back Trajectory ◽  
Time Step ◽  
Air Masses ◽  
Upper Troposphere ◽  
Upper Tropospheric Humidity ◽  
The Indian Ocean

AbstractThe spatial and temporal distribution of upper-tropospheric humidity (UTH) observed by the Sounder for Atmospheric Profiling of Humidity in the Intertropics by Radiometry (SAPHIR)/Megha-Tropiques radiometer is analyzed over two subregions of the Indian Ocean during October–December over 2011–14. The properties of the distribution of UTH were studied with regard to the phase of the Madden–Julian oscillation (active or suppressed) and large-scale advection versus local production of moisture. To address these topics, first, a Lagrangian back-trajectory transport model was used to assess the role of the large-scale transport of air masses in the intraseasonal variability of UTH. Second, the temporal evolution of the distribution of UTH is analyzed using the computation of the higher moments of its probability distribution function (PDF) defined for each time step over the domain. The results highlight significant differences in the PDF of UTH depending on the phase of the MJO. The modeled trajectories ending in the considered domain originate from an area that strongly varies depending on the phases of the MJO: during the active phases, the air masses are spatially constrained within the tropical Indian Ocean domain, whereas a distinct upper-tropospheric (200–150 hPa) westerly flow guides the intraseasonal variability of UTH during the suppressed phases. Statistical relationships between the cloud fractions and the UTH PDF moments of are found to be very similar regardless of the convective activity. However, the occurrence of thin cirrus clouds is associated with a drying of the upper troposphere (enhanced during suppressed phases), whereas the occurrence of thick cirrus anvil clouds appears to be significantly related to a moistening of the upper troposphere.

scholarly journals Vallicula multiformis Rankin, 1956 (Ctenophora, Platyctenida): first record from the Indian Ocean

Check List ◽  
2015 ◽  
Vol 11 (1) ◽  
pp. 1544 ◽  
Author(s):  
Amruta Prasade ◽  
Deepak Apte ◽  
Purushottam Kale ◽  
Otto M.P. Oliveira
Keyword(s):  
Indian Ocean ◽  
Geographic Distribution ◽  
West Coast ◽  
Arabian Sea ◽  
First Record ◽  
West Coast Of India ◽  
The Pacific ◽  
The Indian Ocean ◽  
First Time

The benthic ctenophore Vallicula multiformis Rankin, 1956 is recorded for the first time in the Arabian Sea, from the Gulf of Kutch, west coast of India in March 2013. This occurrence represents a remarkable extension of its geographic distribution that until now included only known the Pacific and Atlantic oceans.

scholarly journals Satellite-observed relationships between aerosol and trade-wind cumulus cloud properties over the Indian Ocean

2011 ◽  
Vol 38 (1) ◽  
pp. n/a-n/a ◽  
Author(s):  
Sagnik Dey ◽  
Larry Di Girolamo ◽  
Guangyu Zhao ◽  
Alexandra L. Jones ◽  
Greg M. McFarquhar
Keyword(s):  
Indian Ocean ◽  
Trade Wind ◽  
Cumulus Cloud ◽  
Cloud Properties ◽  
The Indian Ocean
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