scholarly journals Daily summer monsoon rainfall over northeast India due to synoptic scale systems

MAUSAM ◽  
2021 ◽  
Vol 59 (1) ◽  
pp. 35-50
Author(s):  
M. MOHAPATRA ◽  
H. R. BISWAS ◽  
G. K. SAWAISARJE
Keyword(s):  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Rainfall Variability ◽  
Daily Rainfall ◽  
Northeast India ◽  
Monsoon Trough ◽  
Summer Monsoon Rainfall ◽  
Synoptic Scale ◽  
Data Set ◽  
The Mean

The summer monsoon rainfall over northeast India mostly depends on the synoptic systems over the region and neighbourhood and the convection due to the interaction of orography with the synoptic and sub-synoptic scale systems. Hence, an attempt is made to analyse the mean daily rainfall distribution over northeast India due to different synoptic systems like Low Pressure Systems (LPS) and cyclonic circulations (cycir) extending upto lower/middle tropospheric levels over different regions. The mean daily rainfall due to monsoon trough over various locations in northeast India is also analysed. For the above purpose, the rainfall data over 50 uniformly distributed stations in northeast India during summer monsoon season (June-September) for a period of 10 years (1991-2000) are considered. The principal objective of the study is to find out the contribution of the different synoptic systems to the spatial variability of monsoon rainfall over northeast India.   The developed synoptic analog maps may be useful to the forecasters for 24 hours rainfall forecast with the knowledge of location, intensity and movement of the synoptic systems. Based on larger data set, the results confirm the earlier findings (Srinivasan et al., 1972) with respect to rainfall due to monsoon trough and LPS. The Low Level Cycir (LLC) also plays significant role on the rainfall variability over northeast India, as the number of LLC days is significantly higher over the region, contrary to the days of occurrence of LPS. The study finds out the regions of excess/deficient rainfall and active/weak monsoon conditions due to different synoptic systems.

Some New Insights in to the Influence of Secular Changes in Sunspot Activity on Monsoon Rainfall Variability and Occurrences of Major Droughts in India during 650-2018 AD

2020 ◽  
Author(s):  
Ambily S ◽  
Girish T.E ◽  
Haritha V.G ◽  
Sunilkumar Morais.C ◽  
Baburaj M.S
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Monsoon Rainfall ◽  
Indian Summer Monsoon Rainfall ◽  
Rainfall Variability ◽  
Summer Monsoon Rainfall ◽  
Sunspot Activity ◽  
Multiple Sources ◽  
Secular Changes ◽  
12Th Century

We have defined M cycles as modified form of Gleissberg cycles to study the quasi-periodic secular changes in sunspot activity. Using direct and proxy observations for more than 1200 years we have provided evidence for the influence of the above M cyles on the monsoon rainfall variability and occurrences of major droughts in India. The solar cycle averages of All Indian summer monsoon rainfall (AISMR) and probability of observation of below or above normal AISMR is found to show correlated variations with changes in amplitude of sunspot cycles during the years 1901-2018 AD. Major droughts in India show a preference to occur during minima and declining phases of the M cycles during the years 650-2018 AD . We could generally find low probability of occurrence of droughts in India during the medieval solar maximum epoch ( 1100-1250 AD) and during most of the prolonged sunspot minima periods including the Maunder minima. The evolution of mean Indian summer monsoon rainfall during 650-1900 AD is studied using proxy data from multiple sources with maxima during the 12th century and minima during 14th and 19th centuries. The association of Indian droughts with El-Nino and the possibilities of long term prediction of Indian summer monsoon rainfall variability will be also discussed

scholarly journals Interannual Variation of the Summer Rainfall Center in the South China Sea

2017 ◽  
Vol 30 (19) ◽  
pp. 7909-7931 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
Jun Matsumoto
Keyword(s):  
Summer Monsoon ◽  
Interannual Variation ◽  
Monsoon Rainfall ◽  
Monsoon Season ◽  
Summer Rainfall ◽  
The Philippines ◽  
Monsoon Trough ◽  
Summer Monsoon Rainfall ◽  
Tropical Depression ◽  
Easterly Wave

Abstract A northwest–southeast-oriented summer monsoon trough exists between northern Indochina and northwestern Borneo. Ahead of this the South China Sea (SCS) trough is located at a convergent center west of the Philippines, which provides an environment favorable for rain-producing synoptic systems to produce rainfall over this center and form the SCS summer rainfall center. Revealed from the x–t diagram for rainfall, this rainfall center is developed by multiple-scale processes involved with the SCS trough (TR), tropical depression (TY), interaction of the SCS trough with the easterly wave/tropical depression (EI), and easterly wave (EW). It is found that 56% of this rainfall center is produced by the SCS trough, while 41% is generated by the other three synoptic systems combined. Apparently, the formation of the SCS summer monsoon rainfall center is contributed to by these four rain-producing synoptic systems from the SCS and the Philippines Sea. The Southeast Asian summer monsoon undergoes an interannual variation and exhibits an east–west-oriented cyclonic (anticyclonic) anomalous circulation centered at the western tropical Pacific east of the Luzon Strait. This circulation change is reflected by the deepening (filling) of the SCS summer monsoon trough, when the monsoon westerlies south of 15°N intensify (weaken). This interannual variation of the monsoon westerlies leads to the interannual variation of the SCS summer monsoon rainfall center to follow the Pacific–Japan oscillation of rainfall. The rainfall amount produced over this rainfall center during the weak monsoon season is about two-thirds of that produced during the strong monsoon season. The rain-production ratio between TR and TY + EI + EW is 60:38 during the strong monsoon season and 47:49 during the weak monsoon season.

Synoptic-scale variation of δ 18O in summer monsoon rainfall at Lijiang, China

2006 ◽  
Vol 51 (23) ◽  
pp. 2897-2904 ◽  
Author(s):  
Hongxi Pang ◽  
Yuanqing He ◽  
Aigang Lu ◽  
Jingdong Zhao ◽  
Baoying Ning ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Summer Monsoon Rainfall ◽  
Synoptic Scale ◽  
Scale Variation

Indian summer monsoon rainfall variability in response to differences in the decay phase of El Niño

2016 ◽  
Vol 48 (7-8) ◽  
pp. 2707-2727 ◽  
Author(s):  
Jasti S. Chowdary ◽  
H. S. Harsha ◽  
C. Gnanaseelan ◽  
G. Srinivas ◽  
Anant Parekh ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
El Niño ◽  
Monsoon Rainfall ◽  
Indian Summer Monsoon Rainfall ◽  
El Nino ◽  
Rainfall Variability ◽  
Summer Monsoon Rainfall ◽  
Decay Phase
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