Impact of Pacific Decadal Oscillation in relation to QBO on Indian summer monsoon rainfall
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ORIGINAL PAPER
Impact of Pacific Decadal Oscillation in relation to QBO on Indian summer monsoon rainfall Rajeev Bhatla 1,2 & Sahil Sharma 1 & Shruti Verma 1 & Bimal Gyawali 1 Received: 13 May 2020 / Accepted: 1 November 2020 # Saudi Society for Geosciences 2020
Abstract The relationship between Indian Summer Monsoon (ISM) rainfall (June to September) and Pacific Decadal Oscillation (PDO) Index for the concurrent and succeeding seasons over all India and its three specific regions, i.e., northeast, northwest, and peninsular region has been examined from the years 1953 to 2016. The information is shared for the full series as well as by grouping the seasonal rainfall of India and PDO data according to the different phases (westerly/easterly) of quasi-biennial oscillation (QBO) at the 50 hPa level. The results suggest that for full series, the concurrent season July–August–September (JAS) shows higher degree of association as compared with June–July–August (JJA). When the seasonal rainfall and the PDO index data are stratified according to the phase of QBO, correlation coefficient (CC) values are showing a strong inverse association during the easterly phase of QBO over all India and the northwest region of India while the CC value is reduced during the westerly phase. For the northeast Indian region, concurrent CC values are showing high (low) during the westerly (easterly) phase of QBO. In addition, the warm PDO events are persistent during the summer monsoon period in association of easterly (westerly) phase of QBO causes drought (flood) events over India. However, the cold phase of PDO follows the easterly and westerly phase of QBO where the indication of drought and flood events is not persistent. Keywords Pacific Decadal Oscillation index . Quasi-biennial oscillation . Indian Summer Monsoon rainfall . Concurrent and succeeding seasons of monsoon
Introduction The south-west (SW) monsoon season is one of the fundamental parts of the climate over tropical region. The Indian landmass receives about 75% of the annual rainfall during SW monsoon (Saha and Mooley 1978) which leads the income of approximately two third of the total population depends on agriculture (Krishna Kumar et al. 2004). Over 61% of the agricultural area in India is not in any form of irrigation and is completely dependent on Indian Summer Monsoon (ISM) rainfall. Half of the India’s Responsible Editor: Zhihua Zhang * Rajeev Bhatla [email protected] 1
Department of Geophysics, Institute of Science, Banaras Hindu University, Varanasi 221005, India
2
DST-Mahamana Centre of Excellence in Climate Change Research, Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi, India
agricultural output comes from the summer crop which in turn depends on monsoon. Thus, the variability of summer monsoon rainfall has a profound impact on the Indian economy as well as on agriculture of India. Therefore, long range forecasting of ISM rainfall is highly important to balance the Indian economy and to feed the large population o
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