Increasing trend of northeast monsoon rainfall over the equatorial Indian Ocean and peninsular India

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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District-level forecast of northeast monsoon rainfall over Tamilnadu using Indian Ocean dipole mode index

MAUSAM ◽

10.54302/mausam.v62i2.291 ◽

2021 ◽

Vol 62 (2) ◽

pp. 229-234

Author(s):

O.P. SINGH ◽

ONKARI PRASAD

Keyword(s):

Indian Ocean ◽

Indian Ocean Dipole ◽

Lead Time ◽

Monsoon Rainfall ◽

District Level ◽

Annual Rainfall ◽

Northeast Monsoon ◽

Dipole Mode ◽

Indian Ocean Dipole Mode ◽

Northeast Monsoon Rainfall

The northeast monsoon season (October-December) contributes a substantial percentage of annual rainfall over Tamilnadu. The present paper describes a method for prediction of northeast monsoon rainfall (NEMR) over Tamilnadu on smaller spatial scale, i.e., district-level with sufficient lead time. Tamilnadu has been divided into ten homogeneous clusters of districts and the predictions are made for each cluster with lead times of two and one months using Indian Ocean dipole mode (IODM) index. A stronger western pole of IODM during August-September is associated with enhanced northeast monsoon activity over most of the districts of Tamilnadu. The predictions on the basis of regressions developed from NEMR and IODM index data have been validated for six years from 1997-2002. For many districts the mean errors between actual (realized) and predicted rainfall are within ±10%. Hence, using IODM index, it is possible to predict the NEMR activity over most of the districts of Tamilnadu with a lead time of two months, with only exception of NEMR over Kanyakumari which is not significantly correlated to IODM phenomenon.

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Multi-model ensemble schemes for predicting northeast monsoon rainfall over peninsular India

Journal of Earth System Science ◽

10.1007/s12040-011-0111-4 ◽

2011 ◽

Vol 120 (5) ◽

pp. 795-805 ◽

Cited By ~ 22

Author(s):

NACHIKETA ACHARYA ◽

S C KAR ◽

MAKARAND A KULKARNI ◽

U C MOHANTY ◽

L N SAHOO

Keyword(s):

Monsoon Rainfall ◽

Northeast Monsoon ◽

Model Ensemble ◽

Peninsular India ◽

Northeast Monsoon Rainfall

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High‐resolution Climate Change Projection of Northeast Monsoon Rainfall over Peninsular India

Quarterly Journal of the Royal Meteorological Society ◽

10.1002/qj.4017 ◽

2021 ◽

Author(s):

C. B. Jayasankar ◽

K. Rajendran ◽

Sajani Surendran ◽

K. V. Ajay Anand

Keyword(s):

Climate Change ◽

High Resolution ◽

Monsoon Rainfall ◽

Northeast Monsoon ◽

Peninsular India ◽

Climate Change Projection ◽

Northeast Monsoon Rainfall

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The effect of ENSO / Anti ENSO on northeast monsoon rainfall

MAUSAM ◽

10.54302/mausam.v50i4.1947 ◽

2021 ◽

Vol 50 (4) ◽

pp. 343-354

Author(s):

U. S. DE ◽

R. K. MUKHOPADHYAY

Keyword(s):

Tamil Nadu ◽

Arabian Sea ◽

Monsoon Rainfall ◽

Southern Oscillation ◽

Northeast Monsoon ◽

Monsoon Precipitation ◽

Peninsular India ◽

Enso Events ◽

The North ◽

Northeast Monsoon Rainfall

Northeast monsoon precipitation data of 5 meteorological sub-divisions in India, spanning the period 1901-97, were analysed to identify the effect of ENSO/Anti ENSO events on the rainfall over southern peninsular India. ENSO/Anti ENSO years were selected on the basis of seasonal Southern Oscillation Index (SOI). The analysis revealed that ENSO years were generally associated with enhanced northeast monsoon precipitation while there was reduced precipitation during Anti ENSO years, the reduction in Anti ENSO years being significant for Tamil Nadu (at 0.1% level), for Kerala (at 1% level) and for South Peninsular India (at 1% level). Of 22 ENSO years, 18 years were found to be either flood or wet years, while 11 years out of 15 Anti ENSO years were found to be either drought or dry years. During ENSO years, the Sea Surface Temperature (SST) anomalies both over the Arabian Sea and the Bay of Bengal were positive during the months October to December, while the reverse was the case during Anti ENSO years. A concurrent significant positive correlation was noted between SST over east central Arabian Sea and the north central Bay regions and northeast monsoon rainfall. The cyclonic systems were observed to form relatively at lower latitudes during ENSO years as compared to those during Anti ENSO years. These systems were also found to move in a more westerly direction, hit Tamil Nadu and south Andhra coast, thus giving more rain over peninsula during ENSO years. The ridge line at 200 hPa level during ENSO years was located 3° south as compared to its location during Anti ENSO years.

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The Strengthening Relationship between ENSO and Northeast Monsoon Rainfall over Sri Lanka and Southern India

Journal of Climate ◽

10.1175/jcli3670.1 ◽

2006 ◽

Vol 19 (8) ◽

pp. 1567-1575 ◽

Cited By ~ 57

Author(s):

Lareef Zubair ◽

C. F. Ropelewski

Keyword(s):

Sri Lanka ◽

Indian Ocean ◽

El Niño ◽

Monsoon Rainfall ◽

El Nino ◽

Southern Oscillation ◽

Tropical Indian Ocean ◽

Northeast Monsoon ◽

Peninsular India ◽

The Relationship

Abstract Recently, it was reported that the relationship of the Indian southwest monsoon rainfall with El Niño–Southern Oscillation (ENSO) has weakened since around 1980. Here, it is reported that in contrast, the relationship between ENSO and the northeast monsoon (NEM) in south peninsular India and Sri Lanka from October to December has not weakened. The mean circulation associated with ENSO over this region during October to December does not show the weakening evident in the summer and indeed is modestly intensified so as to augment convection. The intensification of the ENSO–NEM rainfall relationship is modest and within the historical record but stands in contrast to the weakening relationship in summer. The intensification of the circulation is consistent with the warming of surface temperatures over the tropical Indian Ocean in recent decades. There is modestly intensified convection over the Indian Ocean, strengthening of the circulation associated with ENSO (Walker circulation), and enhanced rainfall during El Niño episodes in a manner consistent with an augmented ENSO–NEM relationship.

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