scholarly journals Variations in intensity and structure of a westward-propagating monsoon depression

MAUSAM ◽  
2022 ◽  
Vol 44 (3) ◽  
pp. 231-238
Author(s):  
KSHUDIRAM SAHA ◽  
SURANJANA SAHA

The study deals with a monsoon depression which developed over the Bay of Bengal, moved westward across central India and turned into a mid-tropospheric disturbance (MTD) over the northeastern : corner of the Arabian Sea. Its interactions with the thermal fields associated with the basic monsoon, subtropical westerly troughs and a new depression over the Bay of Bengal are examined. Evidence suggests the involvement of all the three factors in causing the observed variations in its intensity and structure. The low pressure system turned into a mid-tropospheric disturbance when it re-entered the warm sector of the basic monsoon field and received increased warm advection from the north to the west of its centre and cold advection from the south to the east in mid-troposphere. The importance of thermal advection is confirmed by computation of a heat budget. The role of condensation heating is also briefly discussed.  

2008 ◽  
Vol 117 (4) ◽  
pp. 429-447 ◽  
Author(s):  
M. K. Sharada ◽  
P. S. Swathi ◽  
K. S. Yajnik ◽  
C. Kalyani Devasena

2005 ◽  
Vol 35 (3) ◽  
pp. 395-400 ◽  
Author(s):  
S S C. Shenoi ◽  
D. Shankar ◽  
S. R. Shetye

Abstract The accuracy of data from the Simple Ocean Data Assimilation (SODA) model for estimating the heat budget of the upper ocean is tested in the Arabian Sea and the Bay of Bengal. SODA is able to reproduce the changes in heat content when they are forced more by the winds, as in wind-forced mixing, upwelling, and advection, but not when they are forced exclusively by surface heat fluxes, as in the warming before the summer monsoon.


Author(s):  
Jenson V. George ◽  
P.N. Vinayachandran ◽  
Anoop A. Nayak

AbstractThe inflow of high saline water from the Arabian Sea (AS) into the Bay of Bengal (BoB) and its subsequent mixing with the relatively fresh BoB water is vital for the North Indian Ocean salt budget. During June–September, Summer Monsoon Current carries high salinity water from the AS to the BoB. A time series of microstructure and hydrographic data collected from 4–14 July 2016 in the Southern BoB (8°N, 89°E) showed the presence of subsurface (60–150 m) high-salinity core. The high-salinity core was comprised of relatively warm and saline AS water overlying the relatively cold and fresh BoB water. Lower part of the high-salinity core showed double-diffusive salt fingering instability. Salt fingering staircases with varying thickness (up to 10 m) in the temperature and salinity profiles were also observed at the base of high-salinity core at approximately 75–150 m depth. The average downward diapycnal salt flux out of the high salinity core due to the effect of salt fingering was 2.8×10−7 kg m−2 s−1; approximately one order of magnitude higher than the flux if salt fingering were neglected.


2012 ◽  
Vol 140 (11) ◽  
pp. 3620-3633 ◽  
Author(s):  
J. V. Ratnam ◽  
S. K. Behera ◽  
Y. Masumoto ◽  
T. Yamagata

Abstract Remote effects due to the tropical disturbances in the north Indian Ocean are investigated by analyzing long-lasting (≥5 days) tropical disturbances, which reached at least the strength of tropical storms. The present analysis is carried out for both the pre- and postmonsoon periods. The spatial and temporal distribution of the outgoing longwave radiation (OLR) during the premonsoon disturbances over the Bay of Bengal reveals several interesting features. Temporal distribution of the OLR anomalies shows that the intraseasonal oscillations play an important role in the formation of those disturbances. The spatial distribution of the OLR anomalies shows a dipole with negative OLR anomalies over the bay and positive OLR anomalies over the Indonesian region. The atmospheric response to the negative OLR anomalies results in positive temperature anomalies over northwest India, Pakistan, Afghanistan, Iran, and Saudi Arabia, remote from the disturbance; and the response to the positive anomalies causes slight increase in the sea surface temperature of the Arabian Sea. Negative OLR anomalies are also seen over western Japan due to the Rossby waves generated by the heating over the Bay of Bengal besides the enhancement of the so-called “Pacific–Japan” teleconnection pattern. However, the analysis shows that the postmonsoon disturbances over the Bay of Bengal and the disturbances formed over the Arabian Sea in both pre- and postmonsoon seasons do not develop remote teleconnections associated with the above type of Rossby wave mechanism. These results are significant for the short- to medium-range weather forecast over a wide range covering Japan, Pakistan, Afghanistan, Iran, and Saudi Arabia.


2017 ◽  
Vol 18 (3) ◽  
pp. 683-692 ◽  
Author(s):  
W. Timothy Liu ◽  
Xiaosu Xie

Abstract Satellite observations between 2007 and 2015 are used to characterize the annual occurrence of the premonsoon drought (PMD), which causes human death and economic hardship in India, and to postulate its scientific causes. The PMD is identified as the driest and hottest weeks in central India just before the summer monsoon onset. The onset is marked by a sharp increase in precipitation and soil moisture and a decrease in air temperature. The difference between integrated moisture transported in from the Arabian Sea and out to the Bay of Bengal is largely deposited as rain over land during the summer monsoon. The PMD occurs during the short period when moisture is drawn out to the Bay of Bengal before it can be replenished from the Arabian Sea. The time gap is caused by the earlier start of summer monsoon (southwest) winds in the Bay of Bengal than in the Arabian Sea. Sea surface temperature rise precedes the start of summer monsoon wind in both the Arabian Sea and the Bay of Bengal, and it has the potential to give advance warning of the PMD and thus allow mitigation of the adverse effects.


MAUSAM ◽  
2021 ◽  
Vol 60 (1) ◽  
pp. 61-72
Author(s):  
A. MUTHUCHAMI

The two basins Arabian sea (ARS) and Bay of Bengal (BOB) of the North Indian Ocean (NIO) are having different dynamic and thermodynamic character and therefore ARS has subdued cyclone activity than BOB. In order to examine the difference between these basins in respect of various meteorological parameters, using NCEP/NCAR reanalysis data for the period 1971-2005 during the months of September to December the distribution of the dynamic and thermodynamic parameters are discussed. It is seen that sea surface temperature (SST) is not responsible for subdued activity over ARS as the SST over ARS and BOB is mostly above minimum threshold level. In respect of wind shear, during October in ARS north of 10°  N is favourable for storm formation unlike September where the whole of Arabian sea except the region north of 20° N is inert to cyclone formation. The humidity factor is more pronounced in ARS for prohibiting storm formation than shear factor. In all the months static instability at 90° E is least and so the atmosphere is neutral throughout the period and consequence of it any small trigger in the lower level will induce the system to grow further.  The BOB is more barotropic than ARS. There is a considerable difference exists in precipitation rate as a consequence of more stable atmosphere over Arabian sea than in Bay of Bengal even at the lower level.


1979 ◽  
Vol 50 (6) ◽  
pp. 773-778 ◽  
Author(s):  
Harold P. Smith ◽  
John M. Russell ◽  
William H. Boyce ◽  
Eben Alexander

✓ Among 481 children with myelomeningocele seen at the North Carolina Baptist Hospital since 1949, 46 have undergone a urinary diversion procedure, as follows: ileal loop in 43; sigmoid loop in two; and transverse colon conduit in one. The indications for diversion were incontinence in 28, urinary infection or pyelonephritis in 27, and hydronephrosis, pyelocaliectasis, and reflux in 12 patients. No deaths resulted from the diversionary procedures. One patient required early surgical revision and seven patients required late surgical revision. Two patients have since died, 44 have been followed for an average of 7.9 years, 15 for more than 10 years. Overall, of 26 patients with normal prediversionary intravenous pyelograms (IVP's), 88% now have normal or nearly normal IVP's; of 14 patients with abnormal prediversionary IVP's, 79% now have normal, improved, or unaltered IVP's. Renal function has remained normal in all 44 patients, and renal calculi have developed in 10 patients. Ileal loop diversion appears to convert a high-pressure system into a low-pressure system, thereby helping to prevent further renal damage. This procedure tends to stabilize, rather than improve, urinary-tract function. For these children already so incapacitated by their basic disease, this goal is acceptable, particularly since it also provides continence and independence from parental nursing.


2020 ◽  
Vol 54 (7-8) ◽  
pp. 3685-3704 ◽  
Author(s):  
Fabien Desbiolles ◽  
Emma Howard ◽  
Ross C. Blamey ◽  
Rondrotiana Barimalala ◽  
Neil C. G. Hart ◽  
...  

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