On the recent strengthening of the relationship between ENSO and northeast monsoon rainfall over South Asia

The relation between the intensity of Siberian High, defined as the mean sea level pressure over the Siberian region bounded by 87.5 & 102.5° E longitudes and 47.5 & 52.5° N latitudes (PSH) and Indian northeast monsoon rainfall has been studied in antecedent and concurrent modes based on monthly/seasonal mean PSH and monthly/seasonal rainfall data of Tamil Nadu (NMR) for the 34 year period, 1971 to 2004. It has been found that a positive relationship exists between the PSH and NMR of October-November (ON) which is significant in the antecedent mode [PSH(AS/Sep)] and modest in concurrent mode. The relationship turns negative for NMR (Dec) with both PSH(Sep) (antecedent) and PSH(Dec) (concurrent). By and large, negative anomaly profile of PSH during September-November (SON) followed by a positive PSH (Dec) anomaly is associated with a deficient NMR, but, a normal to positive PSH anomaly profile in SON becoming negative in December is associated with an excess NMR. The manifestation of PSH on NMR has been shown to be by way of modulating the strength of low level easterlies over the Bay of Bengal off the southeast coast of peninsular India as well as the latitudinal positions of Sub Tropical Ridge at 200 hPa (STR) and Equatorial Trough at 850 hPa (ET) over India. An intense PSH (Sep) is associated with strengthening of easterlies over the Bay of Bengal as well as southward location of STR/ET thereby favouring a good NMR (ON). During December, a weaker than normal PSH (Dec) is associated with northward location of ET from its normal latitudinal position near the equator which becomes conducive for good NMR(Dec). That a weaker than normal PSH in December is associated with good NMR(Dec) is comprehended from an analysis of time series of PSH. It has been found that the PSH itself undergoes a phase change in December on most occasions, i.e., an intense PSH (Nov) is by and large, followed by a weaker than normal PSH (Dec) and vice versa.

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Relation between southern oscillation index and Indian northeast monsoon as revealed in antecedent and concurrent modes

MAUSAM ◽

10.54302/mausam.v59i1.1129 ◽

2021 ◽

Vol 59 (1) ◽

pp. 15-34

Author(s):

Y. E. A. RAJ ◽

B. GEETHA

Keyword(s):

Southern Oscillation Index ◽

Monsoon Rainfall ◽

Southern Oscillation ◽

Negative Relationship ◽

Positive Temperature ◽

Northeast Monsoon ◽

Temperature Anomalies ◽

Northeast Monsoon Rainfall ◽

Latitudinal Position ◽

The Relationship

The relation between Southern Oscillation Index (SOI) and Indian northeast monsoon has been studied in antecedent and concurrent modes based on monthly /seasonal mean SOI and monthly/seasonal rainfall data of Tamil Nadu for the 104 year period, 1901 to 2004. It has been found that a good negative relationship exists between the SOI and Indian northeast monsoon in antecedent and concurrent modes, the former being stronger than the later. In the concurrent mode, a strong negative relationship exists during the beginning of the season which changes as the season advances and turns positive during the fag end of the season. Such a changing nature of relationship is explained through the variation of latitudinal positions of 200 hPa Sub Tropical Ridge (STR) / Equatorial Trough (ET) and the location of these with reference to the latitudinal location of the area benefited by the northeast monsoon. It has been shown that a positive (negative) SOI shifts the STR north(south)wards throughout the year. The relationship between latitudinal position of STR and the Indian northeast monsoon rainfall (NMR) is negative during the beginning of the season and turns positive during the fag end of the season, which is similar to the relationship between SOI and NMR. The relation between upper tropospheric wind/temperature anomalies and NMR also shows a similar change in relationship. Westerly wind and negative temperature anomalies in October changing to easterly wind and positive temperature anomalies in January are by and large associated with good northeast monsoon activity. The reversal in the relationship between latitudinal position of STR and NMR as the season advances has also been partly explained based on theoretical considerations by invoking the tilting term of the vorticity equation. Thus the SOI appears to manifest itself on Indian northeast monsoon rainfall by way of modulating the latitudinal positions of STR. An analysis based on Australian “Rainman” software on winter monsoon rainfall of some Sri Lankan and southeast Asian stations has substantiated the changing nature of relationship. A study of dates of onset and withdrawal of Indian northeast monsoon in relation to SOI has revealed that negative (positive) SOI in September is associated with early (late) onset. But, continuation of negative SOI throughout the season favours early and abrupt withdrawal. Positive SOI during the fag end of the season is frequently associated with extension of the monsoon into January of the next year.

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Performance evaluation of CORDEX-South Asia simulations and future projections of northeast monsoon rainfall over south peninsular India

Meteorology and Atmospheric Physics ◽

10.1007/s00703-019-00716-2 ◽

2020 ◽

Vol 132 (5) ◽

pp. 743-770 ◽

Cited By ~ 1

Author(s):

M. C. Sannan ◽

M. M. Nageswararao ◽

U. C. Mohanty

Keyword(s):

Performance Evaluation ◽

South Asia ◽

Monsoon Rainfall ◽

Northeast Monsoon ◽

Peninsular India ◽

Future Projections ◽

Northeast Monsoon Rainfall

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On the Predictability of Northeast Monsoon Rainfall over South Peninsular India in General Circulation Models

Pure and Applied Geophysics ◽

10.1007/s00024-012-0633-y ◽

2013 ◽

Vol 170 (11) ◽

pp. 1945-1967 ◽

Cited By ~ 4

Author(s):

Archana Nair ◽

Nachiketa Acharya ◽

Ankita Singh ◽

U. C. Mohanty ◽

T. C. Panda

Keyword(s):

General Circulation ◽

Monsoon Rainfall ◽

General Circulation Models ◽

Northeast Monsoon ◽

Peninsular India ◽

Northeast Monsoon Rainfall

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Influence of moisture source and sink regions on northeast monsoon rainfall

Meteorological Applications ◽

10.1002/met.1705 ◽

2017 ◽

Vol 25 (3) ◽

pp. 376-383 ◽

Cited By ~ 1

Author(s):

P. Suneetha ◽

P. Latha ◽

S. Ramalingeswara Rao ◽

O. S. R. U. Bhanu Kumar

Keyword(s):

Monsoon Rainfall ◽

Northeast Monsoon ◽

Moisture Source ◽

Northeast Monsoon Rainfall ◽

Source And Sink

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Response of the South Indian runoff-harvesting civilization to northeast monsoon rainfall variability during the last 2000 years: instrumental records and indirect evidence

The Holocene ◽

10.1177/0959683607075835 ◽

2007 ◽

Vol 17 (2) ◽

pp. 207-215 ◽

Cited By ~ 21

Author(s):

Yanni Gunnell ◽

Krishnamurthy Anupama ◽

Benjamin Sultan

Keyword(s):

Monsoon Rainfall ◽

Rainfall Variability ◽

Indirect Evidence ◽

Northeast Monsoon ◽

The South ◽

South Indian ◽

Northeast Monsoon Rainfall ◽

Instrumental Records

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DAKSHIN BHARTIYA PADHAR PAR HONE WALI MONSOON WARSHA KA PRADHAN AVYAV VISHLESHAN

MAUSAM ◽

10.54302/mausam.v48i1.3939 ◽

2021 ◽

Vol 48 (1) ◽

pp. 77-82

Author(s):

O.P. SINGH

Keyword(s):

Principal Components ◽

Andhra Pradesh ◽

Monsoon Rainfall ◽

Principal Component ◽

Southwest Monsoon ◽

Northeast Monsoon ◽

Northeast Monsoon Rainfall ◽

Total Variability ◽

Southwest Monsoon Rainfall ◽

The Impact

The result of the Principal Component Analysis of southwest and northeast monsoon rainfall on the southern India plateau have been discussed. Monsoon rainfall data of five meteorological sub-divisions, i.e., Coastal Andhra Pradesh, Rayalseema, Tamilnadu, Interior parts of South Karnataka & Kerala, for a period of 33 years (1960-92), have been utilized. The results indicate that the rainfall of Coastal Andhra Pradesh and Rayalseema has maximum impact on first principal component of southwest monsoon rainfall of five meteorological sub-divisions. The study of only first principal component is sufficient in order to understand the 49% of total variability of southwest monsoon rainfall. Analysis of first three principal components is important to understand 85% of total variability of the rainfall of this season. On the first principal component of northeast monsoon rainfall of aforesaid five meteorological sub-divisions the impact of the rainfall of Kerala and south interior Karnataka has been found maximum. In order to understand the 56% of total variability the analysis of first principal component is sufficient. The special negative relation is found between northeast monsoon rainfall on the Coastal Andhra Pradesh and southwest monsoon rainfall of previous year on this very sub-division and Rayalseema. The principal components of southwest monsoon rainfall may prove useful for forecasting the northeast monsoon rainfall of southern Indian plateau.

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OUTLOOK ON NORTHEAST MONSOON RAINFALL OF TAMIL NADU

MAUSAM ◽

10.54302/mausam.v44i1.3739 ◽

2021 ◽

Vol 44 (1) ◽

pp. 19-22

Author(s):

Y.E.A. RAJ ◽

P. N. SEN ◽

S. M. JAMADAR

Keyword(s):

Multiple Regression ◽

Tamil Nadu ◽

Monsoon Rainfall ◽

Northeast Monsoon ◽

Northeast Monsoon Rainfall ◽

The Mean ◽

In The Beginning

The mean monthly wind vectors at 850, 500 and 150 hPa levels over Thiruvananthapuram (TRV) and Madras (MDS) for August. and September have been subjected to stepwise screening. The objective is to develop a scheme capable of providing an outlook of .northeast monsoon rainfall of Tamil Nu in the beginning of October. A multiple regression scheme of S1K predictors has been identified. The scheme developed from 23•year data performed well when te.ted in an independent five-year period.

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