scholarly journals Subseasonal Dispersal of Freshwater in the Northern Bay of Bengal in the 2013 Summer Monsoon Season

2018 ◽  
Vol 123 (9) ◽  
pp. 6330-6348 ◽  
Author(s):  
J. Sree Lekha ◽  
J. M. Buckley ◽  
A. Tandon ◽  
D. Sengupta
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Summer Monsoon Season ◽  
Northern Bay Of Bengal

scholarly journals Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: Ship-borne measurements and model simulations

2016 ◽  
Author(s):  
Imran A. Girach ◽  
Narendra Ojha ◽  
Prabha R. Nair ◽  
Andrea Pozzer ◽  
Yogesh K. Tiwari ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Surface Ozone ◽  
Ozone Production ◽  
Spatial And Temporal Variability ◽  
Summer Monsoon Season ◽  
Rainfall Events ◽  
Model Simulations ◽  
Mixing Ratios

Abstract. We present ship-borne measurements of surface ozone, carbon monoxide and methane over the Bay of Bengal (BoB), the first time such measurements have been taken during the summer monsoon season, as a part of the Continental Tropical Convergence Zone (CTCZ) experiment during 2009. O3, CO, and CH4 mixing ratios exhibited significant spatial and temporal variability in the ranges of 8–54 nmol mol−1, 50–200 nmol mol−1, and 1.57–2.15 µmol mol−1, with means of 29.7 ± 6.8 nmol mol−1, 96 ± 25 nmol mol−1, and 1.83 ± 0.14 µmol mol−1, respectively. The average mixing ratios of trace gases over northern BoB (O3: 30 ± 7 nmol mol−1, CO: 95 ± 25 nmol mol−1, CH4: 1.86 ± 0.12 µmol mol−1), in airmasses from northern or central India, did not differ much from those over central BoB (O3: 27 ± 5 nmol mol−1, CO: 101 ± 27 nmol mol−1, CH4: 1.72 ± 0.14 µmol mol−1), in airmasses from southern India. Spatial variability is observed to be most significant for CH4. The ship-based observations, in conjunction with backward air trajectories and ground-based measurements over the Indian region, are analyzed to estimate a net ozone production of 1.5–4 nmol mol−1 day−1 in the outflow. Ozone mixing ratios over the BoB showed large reductions (by ~ 20 nmol mol−1) during four rainfall events. Temporal changes in the meteorological parameters, in conjunction with ozone vertical profiles, indicate that these low ozone events are associated with downdrafts of free-tropospheric ozone-poor airmasses. While the observed variations in O3 and CO are successfully reproduced using the Weather Research and Forecasting model with Chemistry (WRF-Chem), this model overestimates mean concentrations by about 20 %, generally overestimating O3 mixing ratios during the rainfall events. Analysis of the chemical tendencies from model simulations for a low-O3 event on August 10, 2009, captured successfully by the model, shows the key role of horizontal advection in rapidly transporting ozone-rich airmasses across the BoB. Our study fills a gap in the availability of trace gas measurements over the BoB, and when combined with data from previous campaigns, reveals large seasonal amplitude (~ 39 and ~ 207 nmol mol−1 for O3 and CO, respectively) over the northern BoB.

scholarly journals Discrepancies in Different Precipitation Data Products in the Bay of Bengal during Summer Monsoon Season

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Li Qi ◽  
Yuqing Wang
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Coastal Region ◽  
Vertical Wind Shear ◽  
Eastern Coast ◽  
Windward Side ◽  
Summer Monsoon Season ◽  
Rainfall Distribution ◽  
Convective Systems

In the east Bay of Bengal (BoB), the precipitation maximum always lies near the eastern coast on the windward side of Mountain Araka Yoma in the summer monsoon season. In this study, different precipitation products are compared in terms of their representation of the offshore rainfall maximum feature in this region. Climatologically, all products examined present similar rainfall distribution except for the CMAP. Significant discrepancies among different products are found in the interannual variation, as illustrated by the contrast features between 2002 and 2005. Based on the TRMM products (except for 3B42RT) and GPCP V1.2, the precipitation maximum occurred near the coast in 2002, while it was about 100–200 km offshore in 2005. However, this difference is not obvious in the GPCP V2.2 and TRMM 3B42RT products. Larger easterly vertical wind shear and warmer SST were present in 2005. Both favor stronger orographically-forced convective systems to propagate offshore, leading to the offshore rainfall maximum in 2005. Therefore, it is suggested that the TRMM 3B40RT, which is mainly based on passive microwave estimates, may be more reliable among different precipitation products in reflecting the precipitation feature in the coastal region of the east BoB.

scholarly journals Observed mini-cold pool off the southern tip of India and its intrusion into the south central Bay of Bengal during summer monsoon season

2006 ◽  
Vol 33 (6) ◽  
Author(s):  
R. R. Rao ◽  
M. S. Girish Kumar ◽  
M. Ravichandran ◽  
B. K. Samala ◽  
Nandakumar Sreedevi
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Cold Pool ◽  
Summer Monsoon Season ◽  
The South ◽  
South Central

scholarly journals Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: shipborne measurements and model simulations

2017 ◽  
Vol 17 (1) ◽  
pp. 257-275 ◽  
Author(s):  
Imran A. Girach ◽  
Narendra Ojha ◽  
Prabha R. Nair ◽  
Andrea Pozzer ◽  
Yogesh K. Tiwari ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Spatial And Temporal Variability ◽  
Summer Monsoon Season ◽  
Rainfall Events ◽  
Air Masses ◽  
Model Simulations ◽  
Mixing Ratios ◽  
Northern India

Abstract. We present shipborne measurements of surface ozone (O3), carbon monoxide (CO), and methane (CH4) over the Bay of Bengal (BoB), the first time such measurements have been performed during the summer monsoon season, as a part of the Continental Tropical Convergence Zone (CTCZ) experiment during 2009. O3, CO, and CH4 mixing ratios exhibited significant spatial and temporal variability in the ranges of 8–54 nmol mol−1, 50–200 nmol mol−1, and 1.57–2.15 µmol mol−1, with means of 29.7 ± 6.8 nmol mol−1, 96 ± 25 nmol mol−1, and 1.83 ± 0.14 µmol mol−1, respectively. The average mixing ratios of trace gases over BoB in air masses from central/northern India (O3: 30 ± 7 nmol mol−1; CO: 95 ± 25 nmol mol−1; CH4: 1.86 ± 0.12 µmol mol−1) were not statistically different from those in air masses from southern India (O3: 27 ± 5 nmol mol−1; CO: 101 ± 27 nmol mol−1; CH4: 1.72 ± 0.14 µmol mol−1). Spatial variability is observed to be most significant for CH4 with higher mixing ratios in the air masses from central/northern India, where higher CH4 levels are seen in the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY) data. O3 mixing ratios over the BoB showed large reductions (by  ∼  20 nmol mol−1) during four rainfall events. Temporal changes in the meteorological parameters, in conjunction with O3 vertical profile, indicate that these low-O3 events are associated with downdrafts of free-tropospheric O3-poor air masses. While the observed variations of O3 and CO are successfully reproduced using the Weather Research and Forecasting model with Chemistry (WRF-Chem), this model overestimates mean concentrations by about 6 and 16 % for O3 and CO, respectively, generally overestimating O3 mixing ratios during the rainfall events. An analysis of modelled O3 along air mass trajectories show mean en route O3 production rate of about 4.6 nmol mol−1 day−1 in the outflow towards the BoB. Analysis of the various tendencies from model simulations during an event on 10 August 2009, reproduced by the model, shows horizontal advection rapidly transporting O3-rich air masses from near the coast across the BoB. This study fills a gap in the availability of trace gas measurements over the BoB and, when combined with data from previous campaigns, reveals large seasonal amplitude ( ∼  39 and  ∼  207 nmol mol−1 for O3 and CO, respectively) over the northern BoB.

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