Progress of Indian summer monsoon onset and convective episodes over Indo-Pacific region observed during 2009-2014

Summer monsoon onset progress from the oceanic region of Southeast Bay of Bengal / Andaman Sea (Oceanr) up to extreme southwestern part of India (Kerala) for the years 2009 to 2014 is investigated. Synoptic weather information, INSAT/KALPANA-1 as well as cloud imageries archived from Dundee Satellite Receiving Station for May and early June for these years are used in the analysis. Upper-air reanalyzed winds from NCEP/NCAR and OLR data archived through NOAA satellites are also used. During the study period, the dates of monsoon onset as well as the time required for the advancement of onset from Oceanr to Kerala have shown a large variation. An attempt is made to investigate the causes for such variations. The results indicate that intense disturbances which formed over north Indian Ocean in 2009, 2010, 2013 and 2014 and over west-north Pacific Oceanic region in 2011 and 2012 have contributed for the same. Analysis is carried out, limiting its focus to bring out the role of these convective events in the observed variation of onset timing and its progress by taking case to case review of these events and bringing out their influence through synoptic analysis. Utility of this information in prediction of the progress of Indian summer monsoon onset is also brought out.

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The modulation of Indian summer monsoon onset processes during ENSO through equatorward migration of the subtropical jet stream

Climate Dynamics ◽

10.1007/s00382-021-05700-4 ◽

2021 ◽

Author(s):

Devanil Choudhury ◽

Debashis Nath ◽

Wen Chen

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Monsoon Onset ◽

Jet Stream ◽

Summer Monsoon Onset ◽

Subtropical Jet Stream ◽

Subtropical Jet

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Oceanic factors controlling the Indian summer monsoon onset in a coupled model

Climate Dynamics ◽

10.1007/s00382-014-2200-y ◽

2014 ◽

Vol 44 (3-4) ◽

pp. 977-1002 ◽

Cited By ~ 30

Author(s):

Chloé Prodhomme ◽

Pascal Terray ◽

Sébastien Masson ◽

Ghyslaine Boschat ◽

Takeshi Izumo

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Coupled Model ◽

Monsoon Onset ◽

Summer Monsoon Onset

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The role of surface air temperature over the east Asia on the early and late Indian Summer Monsoon Onset over Kerala

Scientific Reports ◽

10.1038/s41598-019-47945-4 ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Devanil Choudhury ◽

Debashis Nath ◽

Chen Wen

Keyword(s):

East Asia ◽

Air Temperature ◽

Summer Monsoon ◽

Indian Summer Monsoon ◽

Surface Air Temperature ◽

Monsoon Onset ◽

Summer Monsoon Onset

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The role of surface air temperature over the east Asia on the early and late Indian Summer Monsoon Onset over Kerala

10.5194/egusphere-egu2020-3820 ◽

2020 ◽

Author(s):

Devanil Choudhury ◽

Debashis Nath ◽

Wen Chen

Keyword(s):

East Asia ◽

Air Temperature ◽

Summer Monsoon ◽

Indian Summer Monsoon ◽

Late Onset ◽

Southern China ◽

Surface Air Temperature ◽

Monsoon Onset ◽

Low Level ◽

Summer Monsoon Onset

We investigated the physical mechanism for late Indian Summer Monsoon onset over Kerala (MOK). 14 early and 9 late onset years are selected based on the criteria when the onset is 5 days or more prior and after normal onset date (i.e 1 st June according to India Meteorological Department) respectively. Then, we perform composite analyses of mean May monthly and daily evolution during early and late onset years to examine the differences in monsoon circulation features prior to the MOK. We find that advection of Surface Air Temperature (SAT) from the northern to the southern China and the eastern Tibetan Plateau (TP) plays an important role to modulate the MOK processes. In the late onset years, more low-level jet (LLJ) from the Bay of Bengal (BOB) divert towards the east Asia before the onset, which is due to an extension of the low sea level pressure and high SAT over the east Asia (eastern TP, east-central China). This strengthens the low-level convergence and upper level divergence over the eastern TP and southern China. As a result, a significant amount of moisture from the BOB is transported towards the eastern TP and southern China. Thereby, a comparatively weaker LLJ and deficit low-level moisture supply over the eastern BOB maintain the key roles in modulating the MOK processes.

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