scholarly journals A 140 year data archive of dates of onset and withdrawal of northeast monsoon over coastal Tamil Nadu : 1871-2010 (Re-determination for 1901-2000)

MAUSAM ◽  
2021 ◽  
Vol 66 (1) ◽  
pp. 7-18
Author(s):  
B. GEETHA ◽  
Y.E.A RAJ
Keyword(s):  
Tamil Nadu ◽  
Northeast Monsoon ◽  
Data Archive

scholarly journals Rainfall Profile of Cauvery Delta Zone of Tamil Nadu

2016 ◽  
Vol 11 (2) ◽  
pp. 524-530
Author(s):  
N. K Sathyamoorthy ◽  
R Jagannathan ◽  
A. P Ramaraj
Keyword(s):  
Tamil Nadu ◽  
Southwest Monsoon ◽  
Cold Weather ◽  
Northeast Monsoon ◽  
Water Crisis ◽  
Canal Irrigation ◽  
Increasing Trend ◽  
Hot Weather ◽  
Cauvery Delta ◽  
Normal Rainfall

Thanjavur and Nagapattinam districts of Cauvery Delta Zone (CDZ) depend on canal irrigation for agriculture and are subjected to the vagaries of monsoon. This creates water crisis and affects agriculture of the region considered as rice bowl of Tamil Nadu. This necessitated the study of rainfall to plan and mitigate water scarcity. Rainfall data from Adhirampattinam, Aduthurai stations of Thanjavur district (Inland) and Nagapattinam station (Coastal area of Nagapattinam district) were utilized for the study. Normal rainfall of CDZ is 956 mm; Nagapattinam receives highest (1350 mm) and aduthurai (994 mm) recorded lowest. November is the wettest month for all locations while driest month differs among locations. Northeast monsoon (NEM) was considered as stable monsoon for CDZ as could be seen from the seasonal mean of 641 mm, 620 mm and 919 mm recorded by Adhirampattinam, Aduthurai and Nagapattinam, respectively. Trend analysis of seasons revealed that Adhirampattinam and Nagapattinam follow a decreasing trend for rainfall and rainydays during NEM and Southwest monsoon (SWM), with an increasing trend for Hot weather period (HWP) and Cold weather period (CWP). An interesting deviation is that Aduthurai recording an increasing trend for NEM while it followed same trend for HWP and SWM.

scholarly journals A statistical technique for determination of withdrawal of northeast monsoon over coastal Tamilnadu

MAUSAM ◽  
2021 ◽  
Vol 49 (3) ◽  
pp. 309-320
Author(s):  
Y. E. A. RAJ
Keyword(s):  
Standard Deviation ◽  
Tamil Nadu ◽  
Daily Rainfall ◽  
Statistical Technique ◽  
Northeast Monsoon ◽  
Dynamic Features ◽  
Superposed Epoch Analysis ◽  
Average Decrease ◽  
Sole Criterion ◽  
Normal Rainfall

The withdrawal dates of northeast monsoon over coastal Tamil Nadu for the 90-year period (1901-90) have been objectively derived. The methodology of determination was generally based on an index based on the spatial distribution of daily rainfall over stations of coastal Tamil Nadu, over a 5-day pentad for the six month period, September- February. The normal withdrawal date thus obtained was 27 December with a standard deviation of 13.6 days and range 23 November-28 January. The duration of northeast monsoon was distributed with mean 67.5 days, standard deviation 14.9 days and range 26-102 days. During 36.7 % of years the withdrawal spilled over to January of next year. The daily normal rainfall and its difference filter have been discussed with reference to the normal date of withdrawal. The average decrease of rainfall at the time of withdrawal has been derived by application of superposed epoch analysis. It has further been shown that during years when the withdrawal took place in January the intensity of northeast monsoon prior to withdrawal was as intense as in years when withdrawal occurred in December. A few cases of northeast monsoon withdrawal have been illustrated with diagrams. As no definite dynamic or thermodynamic features could be uniquely identified which are associated with the withdrawal, this technique is basically statistical, considering the behaviour of the daily normal rainfall as the sole criterion. Unique thermodynamic and dynamic features are not identifiable which are associated with the withdrawal of northeast monsoon over coastal Tamilnadu.

scholarly journals Spatial variation of clouding / rainfall over southeast Indian peninsula and adjoining Bay of Bengal associated with active and dry spells of northeast monsoon as derived from INSAT OLR data

MAUSAM ◽  
2021 ◽  
Vol 67 (3) ◽  
pp. 559-570
Author(s):  
B. AMUDHA ◽  
Y. E. A. RAJ ◽  
R. ASOKAN
Keyword(s):  
Spatial Variation ◽  
Tamil Nadu ◽  
Active Phase ◽  
Wave Radiation ◽  
Northeast Monsoon ◽  
Peninsular India ◽  
North East ◽  
The North ◽  
Northern Latitudes ◽  
Dry Spells

South Peninsular India (SPI) benefits largely from the rainfall (RF) realised during the North East Monsoon (NEM) season that prevails from October to December spilling over to January in some of the years.  Salient aspects of clouding / RF over SPI associated with 13 NEM seasons from 2000-01 to 2012-13 have been analysed using estimates of Outgoing Long wave Radiation (OLR) at 1° × 1° resolution derived from the radiance observations in the infra-red channel onboard the geostationary operational Indian satellite (INSAT) radiometers. OLR is considered as a proxy indicator for convective activity with the value of 230 Wm-2  as the threshold for RF occurrence. Year-to-year mean OLR patterns of the NEM season along with the latitudinal and longitudinal variabilities were analysed for dry, light and active phases of NEM. Based on rigorous analysis of INSAT OLR data for the above 13 years, it has been shown that during the active phase of NEM, Coastal Tamil Nadu (CTN) receives more RF while over BoB the RF is lower and decreases sharply over interior Tamil Nadu. This is a reiteration of a similar result from an earlier study based on 3 years (1996-98) OLR data from polar orbiting NOAA satellites. The spatial variation in OLR over the latitudes of 10.5, 12.5 and 14.5° N along  the longitudes of 75.5-85.5° E  has revealed the feature that  north of 10.5° N, values of OLR are higher with decrease in RF from south to north.  During dry phase of NEM in December and January, higher OLR is observed over northern latitudes of BoB than southern latitudes. It has been comprehended that in the southern latitudes of BoB, where higher sea surface temperatures (SST) are prevalent, more moisture is generated and pumped in to upper levels of the atmosphere leading to lower values of OLR compared to northern latitudes.  

scholarly journals OUTLOOK ON NORTHEAST MONSOON RAINFALL OF TAMIL NADU

MAUSAM ◽  
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.

Validation of PERSIANN Precipitation Product Using TAWN Rain Gauge Network Over Different Agro-climatic Zones in Tamil Nadu

2021 ◽  
Vol 108 (september) ◽  
pp. 1-6
Author(s):  
Venkadesh Samykannu ◽  
◽  
Pazhanivelan S ◽  
Keyword(s):  
High Altitude ◽  
Tamil Nadu ◽  
Rain Gauge ◽  
Northeast Monsoon ◽  
Data Set ◽  
Climatic Zones ◽  
Rain Gauges ◽  
Precipitation Estimation ◽  
Cauvery Delta ◽  
Rain Gauge Network

Currently, several satellite-precipitation products were developed using multiple algorithms to estimate rainfall. This study carried out using Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) product over seven agro-climatic zones of Tamil Nadu during the northeast monsoon (NEM) season of October to December for 2015-2017 (three years) against 118 rain-gauges data of Tamil Nadu Agricultural Weather Network (TAWN). The performance compares aggregated seasonal scale of rainfall using continuous (CC, RMSE, and NRMSE) statistical approaches. It was observed that PERSIANN is accurate in the high-altitude hilly zone and the Cauvery delta zone. For 2015, 2016, and 2017, the correlation values were 0.77, 0.52, and 0.71, respectively. The highest RMSE value was measured for northeast zone (NEZ) during 2015 (222.17 mm), and the lowest was determined for 22.63 in the High-altitude hilly zone (HAHZ) during 2016 and NRMSE had less errors during all three seasons. The study concluded that the PERSIANN data set could be useful substitute for rain-gauge precipitation data.

Prediction of Future Extremes During the Northeast Monsoon in the Coastal Districts of Tamil Nadu State in India Based on ENSO

2021 ◽  
Author(s):  
S. Lakshmi ◽  
E. A. K. Nivethaa ◽  
S. N. Ahamed Ibrahim ◽  
A. Ramachandran ◽  
K. Palanivelu
Keyword(s):  
Tamil Nadu ◽  
Northeast Monsoon ◽  
Tamil Nadu State

scholarly journals A scheme for advance prediction of northeast monsoon rainfall of Tamil Nadu

MAUSAM ◽  
2021 ◽  
Vol 49 (2) ◽  
pp. 247-254
Author(s):  
Y. E. A. RAJ
Keyword(s):  
Tamil Nadu ◽  
Monsoon Rainfall ◽  
Southern Oscillation ◽  
Weighted Average ◽  
Test Period ◽  
Northeast Monsoon ◽  
Subtropical Anticyclone ◽  
Northeast Monsoon Rainfall ◽  
The Individual ◽  
June July

Monthly means of winds. contour height and temperature of seven standard isobaric levels of ten well distributed Indian upper air stations for the months of April, June. July, August and September were subjected to correlation analysis to detect parameters that have predictive value to forecast in advance the northeast monsoon rainfall of Tamil Nadu. The period 1965-87 was taken as developmental period and 1988-94 as test period. Six predictors, out of which three were completely new, were identified. The final forecast of rainfall was obtained as the weighted average of the individual forecasts based on the six predictors by employing a screening technique different from the conventional ones. The system explained between 65-77% variation of the predict and with standard error of 13-18% and provided reasonably correct forecasts during the test period. The physical significance of the predictors has been explained based on the intensity of the subtropical anticyclone over India. The possibility of extending the study to include global parameters in the context of proven negative and significant relationship between Southern Oscillation Index (SOl) and the Indian northeast monsoon has been discussed. Scope for further studies on the topic has been spelt out.

scholarly journals Contrasting movement of wind based equatorial trough and equatorial cloud zone over Indian southern peninsula and adjoining Bay of Bengal during the onset phase of northeast monsoon

MAUSAM ◽  
2021 ◽  
Vol 58 (1) ◽  
pp. 33-48
Author(s):  
Y. E. A. RAJ ◽  
R. ASOKAN ◽  
P. V. REVIKUMAR
Keyword(s):  
Bay Of Bengal ◽  
Tamil Nadu ◽  
Southwest Monsoon ◽  
Monsoon Onset ◽  
Northeast Monsoon ◽  
Peninsular India ◽  
Zonal Winds ◽  
The North ◽  
Latitudinal Position ◽  
Onset Phase

ABSTRACT. The northeast monsoon sets in over southern parts of peninsular India after the retreat of southwest monsoon and in association with the southward movement of equatorial trough. The INSAT satellite imageries scrutinised during the past several years revealed that the cloud bands at the time of northeast monsoon onset moved from south Bay into the southern peninsula, a feature that contrasts with the north to south movement of the equatorial trough. The paper investigates this aspect based on a dataset of lower level upper winds of the peninsula, rainfall data and INSAT OLR data for the 20 year period 1981–2000. The super epoch profiles of zonal winds, latitudinal position of equatorial trough with reference to northeast monsoon onset dates have been derived and studied. The region with OLR values less than 230 W/m2 was defined as the equatorial cloud zone and the movement of northern limit of ECZ was studied based on the normal pentad OLR data and also the superposed epoch profiles. From these analysis it has been established that at the time of northeast monsoon onset, the wind based equatorial trough moves south of Comorin whereas the cloud zone in the Bay of Bengal moves from south to north. Reasons for the occurrence of such a contrasting feature have been ascribed to features such as decreasing strength of lower level easterlies from north to south over coastal Tamil Nadu, reversal of temperature gradient between Chennai and Thiruvananthapuram at the time of onset and the dynamics of 40-day oscillation. The northeast monsoon activity over coastal Tamil Nadu has been found to be negatively correlated with the low level zonal winds over the coast, the degree of relation decreasing from north to south and also from October to December. Based on the results derived in the study and also the other known features of northeast monsoon a thematic model of northeast monsoon onset listing the events that precede and succeed the onset has been postulated.

scholarly journals Identifying and Using Suitable Oceanic Domains for Prediction of the Indian Monsoon Rainfall over Tamil Nadu

2021 ◽  
pp. 60-71
Author(s):  
G. Senbagavalli ◽  
N. K. Sathyamoorthy ◽  
Ga. Dheebakaran ◽  
Patil Santosh Ganapati ◽  
S. Kokilavani ◽  
...  
Keyword(s):  
Land Surface ◽  
Tamil Nadu ◽  
Monsoon Rainfall ◽  
Southwest Monsoon ◽  
Vital Role ◽  
Lead Times ◽  
Northeast Monsoon ◽  
Rainfall Prediction ◽  
Model Training ◽  
June July

Rainfall prediction are vital for agriculture which is one of the primary sectors greatly affected by climate variability and extremes. Agriculture plays a vital role in shaping the economy of India which is often affected by monsoon. Sea surface temperature (SST) plays a vital role in rainfall predictability over the land surface. A total of twelve different domains of oceanic influences of SST on monsoon rainfall over Tamil Nadu were selected for analysis. The SST of different lead times (February, March, April, and May for southwest monsoon (SWM) and June, July, August, and September for northeast monsoon (NEM) from the ERSSTv5 and ECMWF-SEAS5 model with the Canonical Correlation Analysis (CCA) were used in the Climate Predictability Tool (CPT) to identify the best predictor domains for the prediction of SWM and NEM rainfall over Tamil Nadu. The model training utilized the first 40 years (1981-2020) SST and rainfall data and prediction was done for the 2021 seasons. The results of the study revealed from Kendall tau goodness index and CCA score, the predictor domains comprised of a combination of oceanic domains, this were the Indian, Arabian, Bay of Bengal, and Pacific Oceans recorded the best CCA score and the goodness index. Is therefore recommended that, these domains which have the highest overall predictability can be used by the National meteorological services to early warning and monsoon rainfall information over Tamil Nadu.

scholarly journals Rainfall Stability and Drought Valuation (Using Spi) Over Southern Zone of Tamil Nadu

2015 ◽  
Vol 10 (3) ◽  
pp. 923-933
Author(s):  
A.P Ramaraj ◽  
S Kokilavani ◽  
N Manikandan ◽  
B Arthirani ◽  
D Rajalakshmi
Keyword(s):  
Tamil Nadu ◽  
Standardized Precipitation Index ◽  
Extreme Drought ◽  
Northeast Monsoon ◽  
Weather Extremes ◽  
Monsoon Period ◽  
Spi Index ◽  
Southern Zone ◽  
Annual Range ◽  
Moderate Drought

Drought is the most extensive hydro-meteorological pattern of prolonged period of water scarcity affecting natural resources and environment. However, it has significantly different characteristics from one region to another. Tamil Nadu agonizes from various disasters including droughts. Generally rainfall deviation from the long-term mean continues to be a widely adopted indicator for drought intensity assessment. The application of this indicator is strongly limited by its inherent nature of its dependence on mean. Thus a standardized procedure that overcomes these limitations becomes a basic need. Moreover stability of rainfall in recent years has been erratic and hence to understand the stability of rainfall over years Precipitation Ratio (PR) was used. Further to understand the drought climatology of southern zone of Tamil Nadu, Standardized Precipitation Index (SPI) was used. PR was studied for three decades (1981-2010) covering seven locations. In most of the locations the rainfall was stable during 1981-90 and thereafter a gradual decline in stability was noticed confirming the weather extremes in the recent decade. SPI had an annual range from +2.69 to -4.94 while Monsoon period had +2.41 to -3.43 and +2.69 to -3.14 respectively for Southwest and Northeast monsoon seasons. As per SPI index, Southern zone is prone to moderate drought followed by severe and extreme drought category. Among the periods studied (Annual, SWM and NEM) number of moderate drought occurrences had no much variation while in severe and extreme drought category, variations could be observed. In particular, during NEM period there was almost no occurrence of extreme drought.

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