On some aspects of southwest monsoon rainfall  over Tamilnadu

The rainfall during southwest monsoon season over Tamilnadu is quite significant from the point of view of water storage in major reservoirs as northeast monsoon rainfall, which is about half of the annual rainfall, is not stable enough due to its large interannual variability. The southwest monsoon rainfall, on the other hand, is more stable. The north-south oriented trough over Tamilnadu and adjoining Bay togetherwith upper air cyclonic circulation/trough in lower tropospheric levels account for three fourths of significant rainfall occurrence during southwest monsoon season. Rainfall during southwest monsoon and northeast monsoon seasons was found to be independent with a small negative correlation of -0.18. This shows that the southwest monsoon rainfall may not be of much use to predict the pattern of northeast monoon rainfall over Tamilnadu.

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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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NGHIÊN CỨU XU THẾ BIẾN ĐỘNG TRƯỜNG NHIỆT ĐỘ BỀ MẶT BIỂN VÀ ẢNH HƯỞNG CỦA ENSO ĐẾN VÙNG BIỂN TÂY NAM VIỆT NAM SỬ DỤNG DỮ LIỆU VIỄN THÁM VÀ GIS

Tạp chí Khoa học và Công nghệ Biển ◽

10.15625/1859-3097/20/2/14173 ◽

2020 ◽

Vol 20 (2) ◽

pp. 129-141

Author(s):

Tran Anh Tuan ◽

Vu Hai Dang ◽

Pham Viet Hong ◽

Do Ngoc Thuc ◽

Nguyen Thuy Linh ◽

...

Keyword(s):

Surface Temperature ◽

Sea Surface Temperature ◽

Monsoon Season ◽

Linear Regression Analysis ◽

Southwest Monsoon ◽

Sea Surface ◽

Northeast Monsoon ◽

Temperature Trends ◽

Sea Surface Temperature Anomalies ◽

Southwest Monsoon Season

In this article, the sea surface temperature trends and the influence of ENSO on the southwest sea of Vietnam were analyzed using the continuous satellite-acquired data sequence of SST in the period of 2002–2018. GIS and average statistical methods were applied to calculate the average monthly and seasonal sea surface temperature, the seasonal sea surface temperature anomalies for each year and for the whole study period. Subsequently, the changing trends of sea surface temperature in the northeast and southwest monsoon seasons were estimated using linear regression analysis. Research results indicated that the sea surface temperature changed significantly throughout the calendar year, in which the maximum and minimum sea surface temperature are 31oC in May and 26oC in January respectively. Sea surface temperature trends range from 0oC/year to 0.05oC/year during the Northeast monsoon season and from 0.025oC/year to 0.055oC/year during the southwest monsoon season. Results based on the Oceanic Niño Index (ONI) analysis also show that the sea surface temperature in the study area and adjacent areas is strongly influenced and significantly fluctuates during El Niño and La Niña episodes.

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Blue whales off the Southern coast of Sri Lanka during the Southwest Monsoon Season

J. Cetacean Res. Manage. ◽

10.47536/jcrm.v21i1.189 ◽

2020 ◽

Vol 21 (1) ◽

pp. 1-7

Author(s):

Grace Russell ◽

Marcus Bridge ◽

Maja Nimak-Wood

Keyword(s):

Sri Lanka ◽

Monsoon Season ◽

Weather Conditions ◽

Southwest Monsoon ◽

Lower Latitude ◽

Northeast Monsoon ◽

Southern Coast ◽

Northern India ◽

Blue Whales ◽

Southwest Monsoon Season

Observations of 37 individual blue whales (Balaenoptera musculus) were recorded off the southern coast of Sri Lanka during the Southwest Monsoon Season (SWM). Sightings were made during a scientific geophysical survey campaign conducted in July and August 2017. Whilst blue whales are regularly recorded on the continental slope of southern Sri Lanka during the Northeast Monsoon Season (NEM) (December - March) and during the two inter-monsoonal periods (March - April and September - October), limited data is available for the SWM (May - September) mostly due to unfavourable weather conditions and very little survey effort. In the northern hemisphere blue whales undertake seasonal migrations from higher latitude feeding grounds to lower latitude breeding and wintering areas. However it has been suggested that a population of blue whales in the Northern India Ocean (NIO) remains in lower latitudes year round taking advantage of the rich upwelling areas off Somalia, southwest Arabia and western Sri Lanka. Data from this study nevertheless support a theory that a certain number of individuals remain off the southern coast off Sri Lanka during the SWM, suggesting that the productivity in this region is sufficient to support their year-round presence. This study therefore fills a knowledge gap regarding the presence and movement of blue whales in the NIO highlighting the importance of data obtained from platforms of opportunity.

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Annual and monthly rainfall trend in plantation and spice farming Western Ghats districts

Journal of Spices and Aromatic Crops ◽

10.25081/josac.2018.v27.i1.1014 ◽

1970 ◽

pp. 45

Author(s):

K Kandiannan, K S Krishnamurthy, C K Thankamani, S J Ankegowda

Keyword(s):

Coefficient Of Variation ◽

Western Ghats ◽

Monsoon Rainfall ◽

Southwest Monsoon ◽

Monthly Rainfall ◽

Negative Trend ◽

Annual Rainfall ◽

Post Monsoon ◽

The Nilgiris ◽

Southwest Monsoon Rainfall

Rainfall analysis of important plantation and spices producing districts such as The Nilgiris (Tamil Nadu), Kodagu (Karnataka) Idukki (Kerala) and Wayanad (Kerala) with 100 years data (1901 to 2000) obtained from the India Meteorological Department (IMD), Pune indicated that mean annual rainfall were 1839.7mm, 2715.7mm, 2979.4mm and 3381.0mm with a coefficient of variation (CV) of 16.0%, 17.0%, 25.8% and 19.6%, respectively. The contribution of southwest monsoon(June-September) to the annual rainfall in these districts were 80.3% (Wayanad), 78.9% (Kodagu), 65.2% (Idukki) and 56.3% (The Nilgiris) with corresponding CV of 24.1%, 20.6%, 32.5%, and 24.6%, respectively. The declining trend in mean annual rainfall was noticed for Idukki, Wayanad and The Nilgiris, whereas, for Kodagu, it was stable. The change was significant in Wayanad and The Nilgiris. Similar trend was also observed for the southwest monsoon rainfall. The maximum decline in annual and southwest monsoon rainfall was noticed in The Nilgiris followed by Wayanad. Pre and post monsoon rainfall receipts were comparatively less with high inter-annual variations. The pre-monsoon (March-May) receipt and its coefficient of variation (CV) was 252.4mm & 20.6% (Kodagu), 360.9mm & 36.5% (Idukki), 251.7mm & 36.6% (The Nilgiris) and 274.2mm & 54.2% (Wayanad). The post monsoon (October-December) rain was maximum in Idukki 548.1mm (CV 27.9%) followed by The Nilgiris 503.4mm(CV 31.3%), Wayanad, 333.1mm(CV 37.8%) and Kodagu 310.5mm (CV 32.7%). In all these districts there was a declining trend in the pre-monsoon rain with maximum decline in The Nilgiris. Similar declining trend was also observed in post-monsoon rain except for The Nilgiris, where the trend has been increasing. Overall, the study gives an indication that there was a spatial and temporal variation in rainfall amounts. The maximum decline in annual rainfall and the southwest monsoon was observed in The Nilgiris and Wayanad. July was the rainiest month in all the districts studied. Significant negative trend was asscoaited with The Nilgiris for January, May, June, July and August months. Whereas, in Kodagu, no significant trend was observed for mean monthly rainfall, except for August. In Idukki, significant negative changes were noticed for January, March, October and December rainfall. Monthly rainfall of January, March, April and July monthly rainfall were showed significant negative trend in Wayanad,. These negative trends across important plantation and spices producing districts of the Western Ghats would affect not only the agricultural economy of this sector but also water resources.

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Study of rainfall features over Goa state during southwest monsoon season

MAUSAM ◽

10.54302/mausam.v61i2.796 ◽

2021 ◽

Vol 61 (2) ◽

pp. 155-162

Author(s):

S. M. METRI ◽

KHUSHVIR SINGH

Keyword(s):

Heavy Rainfall ◽

Monsoon Season ◽

Southwest Monsoon ◽

Annual Rainfall ◽

Statistical Parameters ◽

Maximum Rainfall ◽

Rainfall Events ◽

Average Rainfall ◽

Southwest Monsoon Season ◽

Heavy Rainfall Events

In this paper the rainfall features at different raingauge stations of Goa state have been studied for the period of 30 years. The statistical parameters such as mean monthly rainfall, Standard Deviation and Coefficient of Variation have been computed for each raingauge station of Goa. Some heavy rainfall events during the period have also been studied. The study shows the significant rising trend of rainfall towards the eastern parts of Goa. Goa experiences an average rainfall of about 330 cm annually and around 90% of annual rainfall occurs during southwest monsoon season i.e. (June to September). Studies revealed that most of heavy rainfall events caused due to active off-shore trough and low pressure systems formed over southeast Arabian Sea. It has also come out from the study that the orography of Goa plays an important role in rainfall distribution. Valpoi receives maximum rainfall due to its orographic effect.

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Occurrence of dry and wet weeks over Maharashtra

MAUSAM ◽

10.54302/mausam.v51i1.1754 ◽

2021 ◽

Vol 51 (1) ◽

pp. 25-38

Author(s):

P. G. GORE ◽

V. THAPLIYAL

Keyword(s):

High Probability ◽

Markov Chain Model ◽

Monsoon Season ◽

Daily Rainfall ◽

Southwest Monsoon ◽

The State ◽

Chain Model ◽

Temporal And Spatial Distribution ◽

The North ◽

Southwest Monsoon Season

Based on the daily rainfall data of the past 90 years (1901-90), the initial and conditional probabilities of a wet week and the probabilities of 2 and 3 consecutive wet weeks have been computed for all the districts of Maharashtra during the southwest monsoon season by using Markov Chain model. A temporal and spatial distribution of probabilities of wet weeks have been studied in detail. Most of the districts show the highest probability of wet weeks during July. A few number of the districts show the second highest probability during August. The western and northeastern parts of the state show 10-16 wet weeks with high probability. The high rainfall districts along the west coast show high wet week probabilities during most of the period of the season. A few number of the districts from moderate rainfall zone, show high probability of a wet week during, July and August. A persistency in rainfall is noticed in only extreme western parts of the state. The east-west variation along 19° N shows 'L' shaped pattern for the high probability wet weeks. While, the north -south variation of the wet weeks with high probability shows a sinusoidal curve from north to south.

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Northeast monsoon rainfall and agricultural production in Tamilnadu and Andhra PradeshI - Rainfall variability and its significance in agricultural production

MAUSAM ◽

10.54302/mausam.v64i2.687 ◽

2021 ◽

Vol 64 (2) ◽

pp. 309-316

Author(s):

R.P. SAMUI ◽

M.V. KAMBLE ◽

J.P. SABALE

Keyword(s):

Agricultural Production ◽

Andhra Pradesh ◽

Monsoon Rainfall ◽

Positive Impact ◽

Monsoon Season ◽

Rainfall Variability ◽

Southwest Monsoon ◽

Positive Trend ◽

Northeast Monsoon ◽

Northeast Monsoon Rainfall

ekWulwu Hkkjrh; vFkZO;oLFkk dk egRoiw.kZ ?kVd gS tks —f"k dks izR;{k% :i ls izHkkfor djrk gS D;ksafd ;g ,d pkSFkkbZ th-Mh-ih- vkSj —f"k ij fuHkZj 60 izfr’kr turk dh vkthfodk dks izHkkfor djrk gSA Hkkjr esa eq[;r% nf{k.k&if’peh ekWulwu +_rq ds nkSjku o"kkZ gksrh gSA Hkkjr esa vDrwcj ls fnlEcj ds nkSjku fo’ks"kdj iwohZ vkSj nf{k.kh jkT;ksa esa ekulwuksRrj vof/k] ftls mRrj iwohZ ekWulwu dgrs gS] esa Hkh dkQh o"kkZ gksrh gSA ;g o"kkZ —f"k ds fy, vkSj bu {ks=ksa ds lac) lsDVjksa ds fy, dkQh egRoiw.kZ gksrh gSA rfeyukMq ds iwohZ rVh; ftyksa esa nf{k.k ls mRrj rd o"kkZ esa o`f) dh izo`fRr dk irk pyk gSA blds foijhr vka/kz izns’k ds rVh; nf{k.k iwohZ ftyksa esa vf/kd vkSj mRrj iwohZ Hkkxksa esa o"kkZ esa deh dh izo`fRr dk irk pyk gSA vka/kz izns’k dh vis{kk rfeyukMq esa o"kkZ dh vf/kdrk ds dkj.k mRrj iwohZ ekulwu dk nf{k.k if’pe ekulwu o"kkZ dh rqyuk esa —f"k mRiknu ij vf/kd izHkko dk irk pyrk gSA —f"k mRiknu ij o"kkZ ds izHkko ds v/;;uksa ls vka/kz izns’k esa pkoy vkSj eDdk ds mRiknu esa mRrj iwohZ ekWulwu ds ldkjkRed izHkko dk irk pyk gSA eDdk dh mit esa yxkrkj ldkjkRed izo`fRr dk irk pyk gSA mRrj iwohZ ekulwu _rq ds nkSjku vka/kz izns’k ds rVh; ftyksa dh rqyuk esa rfeyukMq ds rVh; ftyksa esa pØokr ;k vonkc dh otg ls Hkkjh ls vf/kd Hkkjh o"kkZ vkSj ck<+ ds dkj.k mRiknu dh deh vkbZ gSA ifjofrZrk ds ckjs esa mfpr tkudkjh rFkk mRrj iwohZ ekulwu o"kkZ ds ekSleh iwokZuqeku ds lkFk&lkFk —f"k izpkyuksa ds fy, fofo/k uhfr;ksa dk fodkl djus ls bu {ks=ksa ds —f"k vkSj tylalk/ku lsDVjksa ds fy, fu.kZ; ysus esa egRoiw.kZ vuqiz;ksx Hkwfedk gksxhA Monsoon which directly impacts agriculture is an important component of Indian economy because it influences about a quarter of the GDP and livelihood of 60% of the population who depend on agriculture for their livelihood. India receives rainfall mainly during southwest monsoon season. A considerable rainfall also occurs in India during the post monsoon period called as northeast monsoon during October to December, particularly over eastern and southern states and this is of great significance in agriculture and allied sectors in these regions. Increasing trend of rainfall is noticed from south to north in eastern coastal districts of Tamilnadu. On the contrary, it is higher in coastal southeast districts with decreasing trend in northeast parts of Andhra Pradesh. NE monsoon shows greater impact on agricultural production due to its higher quantum of rainfall compared to that of southwest monsoon rain in Tamilnadu than that in Andhra Pradesh. Studies on impact of rainfall on agricultural production revealed positive impact of NE monsoon on rice and maize production in AP. Maize yield is found to exhibit a consistent positive trend. Loss in production due to heavy to very heavy rain and flooding associated with cyclone or depression was more prominent along the coastal districts of Tamilnadu than that in the coastal districts of Andhra Pradesh during northeast monsoon season. Proper understanding of the variability and developing diversified strategies for agricultural operations alongwith the seasonal prediction of northeast monsoon rainfall would have considerable application value for decision making in agriculture and water resource sectors of these regions.

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Annual variations of carbonaceous PM<sub>2.5</sub> in Malaysia: influence by Indonesian peatland fires

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-22419-2015 ◽

2015 ◽

Vol 15 (16) ◽

pp. 22419-22449 ◽

Cited By ~ 2

Author(s):

Y. Fujii ◽

S. Tohno ◽

N. Amil ◽

M. T. Latif ◽

M. Oda ◽

...

Keyword(s):

Organic Compounds ◽

Biomass Burning ◽

Vanillic Acid ◽

Monsoon Season ◽

Chemical Species ◽

Principal Component ◽

Southwest Monsoon ◽

Northeast Monsoon ◽

Mass Ratio ◽

Southwest Monsoon Season

Abstract. In this study, we quantified carbonaceous PM2.5 in Malaysia through annual observations of PM2.5, focusing on organic compounds derived from biomass burning. We determined organic carbon (OC), elemental carbon (EC) and concentrations of solvent-extractable organic compounds (biomarkers derived from biomass burning sources and n-alkanes). We observed seasonal variations in the concentrations of pyrolyzed OC (OP), levoglucosan (LG), mannosan (MN), galactosan, syringaldehyde, vanillic acid (VA) and cholesterol. The average concentrations of OP, LG, MN, galactosan, VA and cholesterol were higher during the southwest monsoon season (June–September) than during the northeast monsoon season (December–March), and these differences were statistically significant. Conversely, the syringaldehyde concentration during the southwest monsoon season was lower. The PM2.5 OP/OC4 mass ratio allowed distinguishing the seven samples, which have been affected by the Indonesian peatland fires (IPFs). In addition, we observed significant differences in the concentrations between the IPF and other samples of many chemical species. Thus, the chemical characteristics of PM2.5 in Malaysia appeared to be significantly influenced by IPFs during the southwest monsoon season. Furthermore, we evaluated two indicators, the vanillic acid/syringic acid (VA/SA) and LG/MN mass ratios, which have been suggested as indicators of IPFs. The LG/MN mass ratio ranged from 14 to 22 in the IPF samples and from 11 to 31 in the other samples. Thus, the respective variation ranges partially overlapped. Consequently, this ratio did not satisfactorily reflect the effects of IPFs in Malaysia. In contrast, the VA/SA mass ratio may serve as a good indicator, since it significantly differed between the IPF and other samples. However, the OP/OC4 mass ratio provided more remarkable differences than the VA/SA mass ratio, offering an even better indicator. Finally, we extracted biomass burning emissions' sources such as IPF, softwood/hardwood burning and meat cooking through varimax-rotated principal component analysis.

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Verification of operational rainfall forecast over eastern India during southwest monsoon season

MAUSAM ◽

10.54302/mausam.v68i2.635 ◽

2021 ◽

Vol 68 (2) ◽

pp. 327-334

Author(s):

G. C. DEBNATH ◽

G. K. DAS

Keyword(s):

West Bengal ◽

Monsoon Rainfall ◽

Monsoon Season ◽

Skill Score ◽

Southwest Monsoon ◽

Summer Monsoon Rainfall ◽

Eastern India ◽

Rainfall Forecast ◽

Heidke Skill Score ◽

Southwest Monsoon Season

The Indian summer monsoon rainfall forecast and its verification has a direct impact on various sectors of public interest besides economy of the country. The present study highlights the verification of distribution forecast of synoptic method issued daily for six met subdivisions, comprising of five states of eastern India namely West Bengal, Sikkim, Bihar, Jharkhand and Odisha. Three years monsoon season rainfall data from 2011 through 2013 are used for the study area. The distribution-oriented verification is done for different rainfall classes like dry, isolated, scattered, fairly widespread and widespread to understand the usefulness of the synoptic method. Statistics are presented for both combined classes of Percentage Correct (PC) and Heidke Skill Score (HSS) of the met subdivision wise forecast and PC, POD and CSI for individual classes. It has been observed that among the met subdivision the efficiency of the method is highest in Sub Himalayan West Bengal (SHWB) & Sikkim followed by Gangetic West Bengal (GWB), Odisha, Jharkhand and Bihar.

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Long term trends in the frequency of monsoonal cyclonic disturbances over the north Indian Ocean

MAUSAM ◽

10.54302/mausam.v52i4.1737 ◽

2022 ◽

Vol 52 (4) ◽

pp. 655-658

Author(s):

O. P. SINGH

Keyword(s):

Arabian Sea ◽

Monsoon Season ◽

Southwest Monsoon ◽

North Indian Ocean ◽

The North ◽

Long Term Trends ◽

Cyclonic Disturbances ◽

Southwest Monsoon Season ◽

Cyclonic Storms

Long term trends in the frequencies of cyclonic disturbances (i.e. depressions and cyclonic storms) and the cyclonic storms forming over the Bay of Bengal and the Arabian Sea during the southwest monsoon season (June-September) have been studied utilizing 110 years data from 1890-1999. There have been significant decreasing trends in both the frequencies but the frequency of cyclonic disturbances has diminished at a faster rate. The trend analysis shows that the frequency of cyclonic disturbances has decreased at the rate of about six to seven disturbances per hundred years in the monsoon season. The frequency of cyclonic storms of monsoon season .has decreased at the rate of , one to two cyclones per hundred years.

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