scholarly journals Thermodynamical characteristics of monsoon troposphere over the Bay of Bengal

MAUSAM ◽  
2021 ◽  
Vol 50 (3) ◽  
pp. 251-256
Author(s):  
O. P. SINGH
Keyword(s):  
Bay Of Bengal ◽  
Lower Troposphere ◽  
Radiosonde Data ◽  
Research Vessel ◽  
Low Level ◽  
Northern Bay Of Bengal ◽  
Level Inversion ◽  
Insight Into

Thermodynamical characteristics of monsoon troposphere, especially the lower troposphere, over different regions of Bay of Bengal has been studied utilising the radiosonde data collected by Ocean Research Vessel (ORV) Sagar Kanya during the period 8 July-5 August, 1991. The results reveal the existence of low level inversions over the central and adjoining parts of southern Bay of Bengal between 13.4°-17.2°N and 84.5°- 90.0°E during July-August The lower troposphere upto 850 hPa appears to be absolutely stable over this region of Bay of Bengal. In total contrast, none of the ascents taken over the region north of 17.7°N showed any low level inversion. The lower troposphere over the northern Bay of Bengal where convection develops under favourable synoptic situations in monsoon, was found to be unstable.   In July the low level inversion appears to extend far south (upto about 10.3°N) but gets disintegrated over the southern parts of Bay of Bengal with the advance of season. Many ascents over the northern and central Bay of Bengal have shown the occurrence of stable layers near 0° level. In the equatorial Bay of Bengal between 5°-10°N stable layers appear to exist near 400 hPa level and near 850-800 hPa level. The results seem to provide an insight into the pattern of convection over the Bay of Bengal during monsoon.

The Convolution of Dynamics and Moisture with the Presence of Shortwave Absorbing Aerosols over the Southeast Atlantic

2015 ◽  
Vol 28 (5) ◽  
pp. 1997-2024 ◽  
Author(s):  
Adeyemi A. Adebiyi ◽  
Paquita Zuidema ◽  
Steven J. Abel
Keyword(s):  
Lower Troposphere ◽  
Radiosonde Data ◽  
Aerosol Layer ◽  
Low Level ◽  
Moisture Effects ◽  
Fine Mode ◽  
Absorbing Aerosols ◽  
St Helena ◽  
Offshore Transport ◽  
Continental Outflow

Abstract Biomass burning aerosols seasonally overlie the subtropical southeast Atlantic stratocumulus deck. Previous modeling and observational studies have postulated a semidirect effect whereby shortwave absorption by the aerosol warms and stabilizes the lower troposphere, thickening the low-level clouds. The focus herein is on the dynamical and moisture effects that may be convoluted with the semidirect effect. Almost-daily radiosonde data from remote St. Helena Island (15.9°S, 5.6°W), covering September–October 2000–11, are combined with daily spatial averages (encompassing the island) of the MODIS clear-sky fine-mode aerosol optical depth (). Increases in are associated with increases in 750–500-hPa moisture content. The net maximum longwave cooling by moisture of almost 0.45 K day−1 reduces the aerosol layer warming from shortwave absorption. ERA-Interim spatial composites show that polluted conditions are associated with a strengthening of a deep land-based anticyclone over southern Africa, facilitating the westward offshore transport of both smoke and moisture at 600 hPa. The shallower surface-based South Atlantic anticyclone exhibits a less pronounced shift to the northeast, strengthening the low-level coastal jet exiting into the stratocumulus deck and cooling 1000-hPa potential temperatures. Warm continental outflow further increases the 800-hPa potential temperatures (), reinforcing the lower tropospheric stability () over the stratocumulus deck. Enhanced southerly dry air advection also strengthens the cloud-top humidity inversion. The increased stability helps explain an observed decrease in cloud-top heights despite an anomalous reduction in subsidence. The changes to the horizontal dynamics enhance low-level cloudiness. These are separate but not necessarily distinct from an aerosol semidirect effect, encouraging care in attribution studies.

scholarly journals Vertical Moist Thermodynamic Structure and Spatial–Temporal Evolution of the MJO in AIRS Observations

2006 ◽  
Vol 63 (10) ◽  
pp. 2462-2485 ◽  
Author(s):  
Baijun Tian ◽  
Duane E. Waliser ◽  
Eric J. Fetzer ◽  
Bjorn H. Lambrigtsen ◽  
Yuk L. Yung ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Temporal Evolution ◽  
Lower Troposphere ◽  
Western Pacific ◽  
Radiosonde Data ◽  
Temperature Structure ◽  
Free Troposphere ◽  
Thermodynamic Structure ◽  
Low Level ◽  
The Indian Ocean

Abstract The atmospheric moisture and temperature profiles from the Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit on the NASA Aqua mission, in combination with the precipitation from the Tropical Rainfall Measuring Mission (TRMM), are employed to study the vertical moist thermodynamic structure and spatial–temporal evolution of the Madden–Julian oscillation (MJO). The AIRS data indicate that, in the Indian Ocean and western Pacific, the temperature anomaly exhibits a trimodal vertical structure: a warm (cold) anomaly in the free troposphere (800–250 hPa) and a cold (warm) anomaly near the tropopause (above 250 hPa) and in the lower troposphere (below 800 hPa) associated with enhanced (suppressed) convection. The AIRS moisture anomaly also shows markedly different vertical structures as a function of longitude and the strength of convection anomaly. Most significantly, the AIRS data demonstrate that, over the Indian Ocean and western Pacific, the enhanced (suppressed) convection is generally preceded in both time and space by a low-level warm and moist (cold and dry) anomaly and followed by a low-level cold and dry (warm and moist) anomaly. The MJO vertical moist thermodynamic structure from the AIRS data is in general agreement, particularly in the free troposphere, with previous studies based on global reanalysis and limited radiosonde data. However, major differences in the lower-troposphere moisture and temperature structure between the AIRS observations and the NCEP reanalysis are found over the Indian and Pacific Oceans, where there are very few conventional data to constrain the reanalysis. Specifically, the anomalous lower-troposphere temperature structure is much less well defined in NCEP than in AIRS for the western Pacific, and even has the opposite sign anomalies compared to AIRS relative to the wet/dry phase of the MJO in the Indian Ocean. Moreover, there are well-defined eastward-tilting variations of moisture with height in AIRS over the central and eastern Pacific that are less well defined, and in some cases absent, in NCEP. In addition, the correlation between MJO-related midtropospheric water vapor anomalies and TRMM precipitation anomalies is considerably more robust in AIRS than in NCEP, especially over the Indian Ocean. Overall, the AIRS results are quite consistent with those predicted by the frictional Kelvin–Rossby wave/conditional instability of the second kind (CISK) theory for the MJO.

scholarly journals Low CO2 evasion rate from the mangrove-surrounding waters of the Sundarbans

2021 ◽  
Author(s):  
Anirban Akhand ◽  
Abhra Chanda ◽  
Kenta Watanabe ◽  
Sourav Das ◽  
Tatsuki Tokoro ◽  
...  
Keyword(s):  
Bay Of Bengal ◽  
Dissolved Inorganic Carbon ◽  
Monsoon Season ◽  
Buffering Capacity ◽  
Marine Water ◽  
High Temporal Resolution ◽  
Post Monsoon Season ◽  
Biogeochemical Parameters ◽  
Northern Bay Of Bengal ◽  
The Sundarbans

AbstractGlobally, water bodies adjacent to mangroves are considered significant sources of atmospheric CO2. We directly measured the partial pressure of CO2 in water [pCO2(water)] and related biogeochemical parameters with high temporal resolution, covering both diel and tidal cycles, in the mangrove-surrounding waters around the northern Bay of Bengal during the post-monsoon season. Mean pCO2(water) was marginally oversaturated in two creeks (470 ± 162 µatm, mean ± SD) and undersaturated in the adjoining estuarine stations (387 ± 58 µatm) compared to atmospheric pCO2, and was considerably lower than the global average. We further estimated the pCO2(water) and buffering capacity of all possible sources of the mangrove-surrounding waters and concluded that their character as a CO2 sink or weak source is due to the predominance of marine water from the Bay of Bengal with low pCO2 and high buffering capacity. Marine water with high buffering capacity suppresses the effect of pCO2 increase within the mangrove system and lowers the CO2 evasion even in creek stations. The δ13C of dissolved inorganic carbon (DIC) in the mangrove-surrounding waters indicated that the DIC sources were a mixture of mangrove plants, pore-water, and groundwater, in addition to marine water. Finally, we showed that the CO2 evasion rate from the estuaries of the Sundarbans is much lower than the recently estimated world average. Our results demonstrate that mangrove areas having such low emissions should be considered when up-scaling the global mangrove carbon budget from regional observations.

Disengaged and Uninformed: 2000 Presidential Election Coverage in Consumer Magazines Popular with Young Adults

2003 ◽  
Vol 80 (3) ◽  
pp. 513-527 ◽  
Author(s):  
Tom Reichert ◽  
James E. Mueller ◽  
Michael Nitz
Keyword(s):  
Young Adults ◽  
Presidential Election ◽  
Political System ◽  
Political Information ◽  
The Political ◽  
General Interest ◽  
Low Level ◽  
Men's Magazines ◽  
Election Coverage ◽  
Insight Into

This study examines content and tone of political information in five leading general interest and lifestyle magazines from December 1999 through November 2000. The analysis revealed a low level of political information in the selected magazines. With the exception of Rolling Stone and Glamour, the nature of coverage was strategy oriented and superficial, while the tone was mostly cynical in men's magazines, yet favorable toward Gore. The results provide a glimpse of the political information available for typical young adults and insight into the apathetic attitudes of young adults toward the American political system.

An observational analysis of the evolution of a mesoscale anti-cyclonic eddy over the Northern Bay of Bengal during May–July 2014

2018 ◽  
Vol 68 (11) ◽  
pp. 1431-1441 ◽  
Author(s):  
Nanda Kishore Reddy Busireddy ◽  
Krishna K. Osuri ◽  
Sanikommu Sivareddy ◽  
Ramasamy Venkatesan
Keyword(s):  
Bay Of Bengal ◽  
Cyclonic Eddy ◽  
Observational Analysis ◽  
Northern Bay Of Bengal

scholarly journals Medium-range mid-tropospheric transport of ozone and precursors over Africa: two numerical case studies in dry and wet seasons

2007 ◽  
Vol 7 (20) ◽  
pp. 5357-5370 ◽  
Author(s):  
B. Sauvage ◽  
F. Gheusi ◽  
V. Thouret ◽  
J.-P. Cammas ◽  
J. Duron ◽  
...  
Keyword(s):  
Mirror Symmetry ◽  
Monsoon Season ◽  
Trade Flow ◽  
Lower Troposphere ◽  
Hadley Cell ◽  
Scale Model ◽  
Wet Season ◽  
Airborne Measurements ◽  
Ozone Precursors ◽  
Low Level

Abstract. A meso-scale model was used to understand and describe the dynamical processes driving high ozone concentrations observed during both dry and monsoon season in monthly climatologies profiles over Lagos (Nigeria, 6.6° N, 3.3° E), obtained with the MOZAIC airborne measurements (ozone and carbon monoxide). This study focuses on ozone enhancements observed in the upper-part of the lower troposphere, around 3000 m. Two individual cases have been selected in the MOZAIC dataset as being representative of the climatological ozone enhancements, to be simulated and analyzed with on-line Lagrangian backtracking of air masses. This study points out the role of baroclinic low-level circulations present in the Inter Tropical Front (ITF) area. Two low-level thermal cells around a zonal axis and below 2000 m, in mirror symmetry to each other with respect to equator, form near 20° E and around 5° N and 5° S during the (northern hemisphere) dry and wet seasons respectively. They are caused by surface gradients – the warm dry surface being located poleward of the ITF and the cooler wet surface equatorward of the ITF. A convergence line exists between the poleward low-level branch of each thermal cell and the equatorward low-level branch of the Hadley cell. Our main conclusion is to point out this line as a preferred location for fire products – among them ozone precursors – to be uplifted and injected into the lower free troposphere. The free tropospheric transport that occurs then depends on the hemisphere and season. In the NH dry season, the AEJ allows transport of ozone and precursors westward to Lagos. In the NH monsoon (wet) season, fire products are transported from the southern hemisphere to Lagos by the southeasterly trade that surmounts the monsoon layer. Additionally ozone precursors uplifted by wet convection in the ITCZ can also mix to the ones uplifted by the baroclinic cell and be advected up to Lagos by the trade flow.

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