scholarly journals Summer monsoon low pressure systems over the Indian region and their relationship with the sub-divisional rainfall

MAUSAM ◽  
2022 ◽  
Vol 53 (2) ◽  
pp. 177-186
Author(s):  
S. K. JADHAV
Keyword(s):  
Summer Monsoon ◽  
Monsoon Season ◽  
Correlation Coefficients ◽  
Central India ◽  
Low Pressure ◽  
Northeast India ◽  
Indian Region ◽  
Pressure System ◽  
Peninsular India ◽  
Latitude Belt

In the present paper performance of the monthly sub-divisional summer monsoon rainfall is studied in association with the position of the Low Pressure System (LPS) over the Indian region. Existence of the LPS over a particular location increases the rainfall activities in certain parts of the country while decreases in some other parts. For this study, the Indian region (5°-35° N and 60° -100° E) is divided into 5°  Lat. ´ 5° Long. grids. The duration of LPS is taken in terms of LPS days with respect to the location of LPS in a particular grid. Monthly total number of LPS days in each of the grids are computed during the summer monsoon season, June to September for the period 1891 – 1990. Maximum number of LPS days (more than half of the total) are observed in the latitude belt between 20°-25°N. The percentages of total LPS days in this area are higher in July and August which are peak monsoon months as compared to June and September. When there is a LPS are in the area 20°-25° N and 80°-90° E, there is significant increase in the rainfall activities in the sub-divisions along mean monsoon trough while northeast India and southeast peninsular India experience significant decrease in rainfall in the months of July and August. Owing to the movement of LPS from east to west through central India, most parts of the country, excluding northeast India and south peninsular India get good rainfall activity. Correlation coefficients between monthly LPS days over the different grids and monthly sub-divisional rainfall are computed to study the relationships. The performance of sub-divisional rainfall mostly related with the occurrence of LPS in certain grid- locations. The correlation field maps may give some useful information about rainfall performance due to LPS in a particular grid locations.

scholarly journals Present operational long range forecasting system for southwest monsoon rainfall over India and its performance during 2010

MAUSAM ◽  
2021 ◽  
Vol 62 (2) ◽  
pp. 179-196
Author(s):  
D.S. PAI ◽  
O.P. SREEJITH ◽  
S.G. NARGUND ◽  
MADHURI MUSALE ◽  
AJIT TYAGI
Keyword(s):  
Monsoon Season ◽  
Central India ◽  
Southwest Monsoon ◽  
Northeast India ◽  
Peninsular India ◽  
South West ◽  
Operational Forecasts ◽  
Geographical Regions ◽  
South West Monsoon ◽  
West Monsoon

At present, India Meteorological Department (IMD) issues various monthly and seasonal operational forecasts for the south-west monsoon season using models based on latest statistical techniques with useful skill. Operational models are reviewed regularly and improved through in house research activities. For the forecasting of the south-west monsoon season (June – September) rainfall over the country as a whole, a newly introduced statistical ensemble forecasting system is used. In addition, models have been developed for the forecast of the monsoon season rainfall over four geographical regions (NW India, NE India, Central India and South Peninsula) of the country and forecast for the rainfall over the second half of the monsoon season over the country as a whole. Models have also been developed for issuing operational forecast for the monthly rainfall for the months of July, August & September over the country as a whole. Operational forecasts issued by IMD for 2010 south-west monsoon rainfall have been discussed and verified. In addition, the experimental forecasts for the season rainfall over the country as a whole based on bothstatistical and dynamical models received from various climate research institutes within the country other than IMD arealso discussed. The operational monthly and seasonal long range forecasts issued for the 2010 southwest monsoon season for the country as a whole were accurate. However, forecasts for the season rainfall over the 4 geographical regions (Northwest India, Central India, Northeast India and south Peninsular India) were not accurate as the forecast for South Peninsular India overestimated the actual rainfall and that for northeast India underestimated the actual rainfall. The experimental forecasts for the season rainfall over the country as whole from various climate research institutes within the country showed large variance (91 % - 112% of LPA).

scholarly journals Sub-divisional summer monsoon rainfall over India in relation to low pressure systems over the Bay of Bengal and adjoining land regions during 1982-1999

MAUSAM ◽  
2021 ◽  
Vol 59 (3) ◽  
pp. 327-338
Author(s):  
M. MOHAPATRA
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
West Coast ◽  
Monsoon Rainfall ◽  
Monsoon Season ◽  
Central India ◽  
Low Pressure ◽  
Seasonal Rainfall ◽  
West Central ◽  
The Impact

A study is undertaken to find out characteristic features of relationship of the low pressure system (LPS) over the Bay of Bengal and adjoining land regions with the rainfall over different meteorological sub-divisions of India during summer monsoon season (June-September). For this purpose, rainfall over 35 meteorological sub-divisions in India and LPS days over west central (WC) Bay, northwest (NW) Bay, northeast (NE) Bay, Bangladesh (BDS), Gangetic West Bengal (GWB), Orissa, north coastal Andhra Pradesh (NCAP), east Madhya Pradesh and Chattisgarh (EMPC) and Jharkhand (JKD) during different monsoon months and the season as a whole over a period of 18 years (1982-1999) are analysed. There is large month to month variation in the impact of the LPS on the sub-divisional monsoon rainfall over India. However, the results presented in the study including developed correlation maps may be helpful to predict 24 hours rainfall based on the location of the LPS and associated monsoon trough.   The frequent development and persistence of LPS over NW Bay are favourable for higher seasonal monsoon rainfall over east central India. The development and persistence of LPS over WC Bay adversely affect the seasonal rainfall over this region. On the other hand, the frequent development and persistence of LPS over WC Bay and its subsequent westward movement across NCAP are favourable for higher seasonal rainfall over the peninsular region excluding west coast. The seasonal rainfall over northwest India decreases with increase in LPS days over EMPC. The seasonal rainfall over west central India, northeast India and west coast are not significantly related with the number of LPS days over the regions under consideration.

scholarly journals Another deficient monsoon 2004 - A comparison with drought year 2002 and possible causes

MAUSAM ◽  
2021 ◽  
Vol 58 (2) ◽  
pp. 161-176
Author(s):  
RAJENDRA KUMAR JENAMANI ◽  
S. R. KALSI ◽  
H. R. HATWAR ◽  
S. K. SUBRAMANIAN
Keyword(s):  
Summer Monsoon ◽  
Large Scale ◽  
Monsoon Season ◽  
Equatorial Indian Ocean ◽  
Central India ◽  
Walker Circulation ◽  
Indian Region ◽  
Western Pacific ◽  
Northwest Pacific ◽  
Atmospheric Conditions

The rainfall over India as a whole during the summer monsoon season of 2004 was deficient with –13% below normal. Earlier in 2002, India has faced another worst situation when large-scale drought occurred and all India rainfall was below –19%. In the present study, we have compared briefly salient observational features of both the monsoons to find out their distinct characteristics. Comparisons show appearance of many similar as well as contrasting features. Though, both seasons were deficient, their dates of onset of monsoon over Kerala were either before or near the normal date. Progress up to central India was also normal in both the seasons. While Indian Summer Monsoon Rainfall (ISMR) during June was good, a few longest stagnation periods during advancing stage in July of both the years made unexpected delay of monsoon in covering entire India. Rainfall of July also suffered the most in both the seasons with a record lowest ISMR in 2002. Not a single depression formed in 2002 while in 2004, their frequency was less than half of normal. Analysis of other large-scale monthly anomalous ocean and atmospheric conditions over Indo-Pacific region including El-Nino conditions confirms that ENSO and Equatorial Indian Ocean Oscillation or EQUINOO have caused drought in July 2002, but not in July 2004. This is because very high typhoon formation and their recurvature with significantly higher than normal convection over northwest Pacific associated with record lowest ISMR in July, 2002 in contrast to occurrence of deficient ISMR in July 2004 which was associated with few typhoon formation and less convection. Also in 2002, Indian region was happened to fall exactly under the subsidence branch of Walker circulation with ascending branch over the western Pacific in the season in contrast to 2004, when subsidence was observed to be both over large part of western Pacific and adjoining Indian region.

scholarly journals Secular variations and trends in the occurrence of monsoon synoptic systems and its impact on central India rainfall

MAUSAM ◽  
2021 ◽  
Vol 60 (3) ◽  
pp. 309-316
Author(s):  
D. M. RASE ◽  
M. P. SHEVALE ◽  
S. I. M. RIZVI
Keyword(s):  
Central India ◽  
Low Pressure ◽  
Indian Region ◽  
Regular Pattern ◽  
Annual Variability ◽  
Secular Variations ◽  
Monsoon Depressions ◽  
Using Data ◽  
Low Pressure Systems

Importance of monsoon depressions, Low Pressure Systems (LPS) and the number of LPS days on rainfall and hence indirectly on agriculture and hydrology, is well recognized.      In this paper the pattern of annual variability in these systems have been examined using data from 1901-2000. The above mentioned parameters have been subjected to decadal analysis to detect presence of any regular pattern. An attempt has been made to find its tendency with time.  Impact of these systems on central India rainfall has been determined and discussed.     The study endorses the earlier findings that there is a   decreasing trend in the frequency of depressions which has been compensated with increase in LPS days over Indian region in recent years.  The rainfall over central India is more significantly related with a number of LPS days over Indian region.

Increase in summer monsoon rains in northeast India during ENSO periods: a multiproxy analysis

2020 ◽  
Author(s):  
Arvind Singh ◽  
Kiran Kumar Pullabotla ◽  
Ramesh Rengaswamy
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Central India ◽  
Northeast India ◽  
Data Set ◽  
Rainfall Variation ◽  
Enso Events ◽  
Proxy Records ◽  
Rainfall Patterns

<p>El-Niño Southern Oscillation (ENSO) affects Indian summer monsoon. Most of the worst droughts - the most recent being in 2009 - in India have been triggered by ENSO. But given the heterogeneity in rainfall patterns over India, we revisited ENSO influence on Indian summer monsoon. Our analysis based on multiple isotopic (proxy-based) and satellite data set shows significant variation in the spatiotemporal patterns of rainfall over the Indian subcontinent and adjoining oceans. We observed a weaker summer monsoon over central India and relatively stronger summer monsoon over northeast India during strong El-Niño events. Rainfall derived from isotope-enabled general circulation models reproduces weak and strong rainfall patterns during the El-Niño events over central India and northeast India, respectively. These model derived δ<sup>18</sup>O<sub>rain</sub> (oxygen isotopic composition of rainfall) variation over central India during ENSO events mimic the weaker rainfall conditions. However, significant changes in the model derived rainfall and associated δ<sup>18</sup>O<sub>rain </sub>is not observed over northeast India during ENSO events. Based on multiple data analysis, we infer that the long term variations (trends) in the Indian summer monsoon strength were controlled by the long term variation in ENSO during the last 50 years (1965 – 2013).</p><p>Since these observations were unprecedented and counterintuitive, we further verified our observations from the proxy records. Two speleothems (cave deposits) records from the central India and northeast India were analyzed for the rainfall variation and ENSO influence signatures. These paleo-proxy records showed a similar inverse relation of rainfall patterns over central India and northeast India during ENSO periods, confirming observed ENSO’s role on rainfall. Also, these proxy records showed a long-term pause in ENSO events or stronger La-Niña like conditions, which were persisted during 1625 – 1715 and favored stronger (weaker) rainfall over central India (northeast India).</p>

scholarly journals Contribution of Monthly and Regional Rainfall to the Strength of Indian Summer Monsoon

2016 ◽  
Vol 144 (9) ◽  
pp. 3037-3055 ◽  
Author(s):  
Yangxing Zheng ◽  
M. M. Ali ◽  
Mark A. Bourassa
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Indian Subcontinent ◽  
India Meteorological Department ◽  
Central India ◽  
Northeast India ◽  
Summer Monsoon Rainfall ◽  
Rainfall Series ◽  
Seasonal Rainfall ◽  
Regional Rainfall

Indian summer monsoon rainfall (ISMR; June–September) has both temporal and spatial variability causing floods and droughts in different seasons and locations, leading to a strong or weak monsoon. Here, the authors present the contribution of all-India monthly, seasonal, and regional rainfall to the ISMR, with an emphasis on the strong and weak monsoons. Here, regional rainfall is restricted to the seasonal rainfall over four regions defined by the India Meteorological Department (IMD) primarily for the purpose of forecasting regional rainfall: northwest India (NWI), northeast India (NEI), central India (CI), and south peninsula India (SPIN). In this study, two rainfall datasets provided by IMD are used: 1) all-India monthly and seasonal (June–September) rainfall series for the entire Indian subcontinent as well as seasonal rainfall series for the four homogeneous regions for the period 1901–2013 and 2) the latest daily gridded rainfall data for the period 1951–2014, which is used for assessment at the extent to which the four regions are appropriate for the intended purpose. Rainfall during July–August contributes the most to the total seasonal rainfall, regardless of whether it is a strong or weak monsoon. Although NEI has the maximum area-weighted rainfall, its contribution is the least toward determining a strong or weak monsoon. It is the rainfall in the remaining three regions (NWI, CI, and SPIN) that controls whether an ISMR is strong or weak. Compared to monthly rainfall, regional rainfall dominates the strong or weak rainfall periods.

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