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Focus Story


        Indian                                                                                                                 El Niño, the warm phase of   variation of monsoon consists
                                                                                                                               ENSO, is associated with the
                                                                                                                                                          of wet spells (Active phase)
                                                                                                                                                          with continuous rains for a
                                                                                                                               warming of SSTs over central
                                                                                                                                                          few days are interspersed
                                                                                                                               and east-central Equatorial
        Monsoon                                                                                                                Pacific adversely impacts the   with relatively dry spells
                                                                                                                                                          (Break phase) of varying
                                                                                                                               Indian monsoons and hence,
                                                                                                                               agriculture in India. The La
                                                                                                                                                          duration. Long breaks in
                                                                                                                                                          critical growth periods of
                                                                                                                               Niña, cooler phase of ENSO
        Variability: It’s                                                                                                      generally favours stronger   agricultural crops lead to
                                                                                                                                                          substantially reduced yield.
                                                                                                                               than normal Indian monsoon.
                                                                                                                                                          Even in normal monsoon
                                                                                                                                                          years, an uneven spatial and
                                                                                                                                 A NEGATIVE IOD
                                                                                                                                                          temporal distribution of rains
        Impact on the                                                                                                            PHASE RESULTS IN         has an adverse effect on
                                                                                                                                                          agriculture. The intra-seasonal
                                                                                                                                 A WEAKER THAN
                                                                                                                                                          rainfall distribution over India
                                                                                                                                 NORMAL INDIAN
                                                                                                                                                          is influenced by different
                                                                                                                                 MONSOON
                                                                                                                                                          quasi-periodic oscillations, viz.
        Indian Economy                                                                                                         Another climatic oscillation,   3-7 days, 10-20 days and               Meteorological Department, New Delhi
                                                                                                                                                          30-60 days. While 3-7 days
                                                                                                                                                                                                            Dr D. S. Pai, Scientist -G, India
                                                                                                                                                          periodicity is associated with
                                                                                                                               referred to as the Indian
                                                                                                                                                          oscillations of the monsoon
                                                                                                                               Ocean Dipole (IOD), involves
                                                                                                                                                          periodicity or quasi-biweekly
                                                                                                                               fluctuations in Sea Surface   trough, the 10-20 days
                                                                                                                               Temperatures (SST) across   oscillations are associated
                                                                                                                               the Western Indian Ocean   with the westward moving
                                                                                                                               near the Arabian Sea and the   waves or synoptic scale
                                                                                                                               eastern counterpart near   convective systems generated
                                                                                                                               Indonesia in the Indian Ocean.   over the warm Bay of Bengal
        I ndia's distinctive       seasonal rainfall during JJAS,                                                              The IOD is essentially the   and propagating inland
         geographical features,
                                   particularly for an economy
        including its proximity to the   heavily reliant on agriculture,                                                       contrast in SSTs between   towards the main land of
                                                                                                                               these two regions. When the
                                                                                                                                                          India. The 30-60 days
        Himalayas and the expansive   such as India's.                                                                         western part of the Indian   oscillations, popularly known
        Asian landmass in the north,                                                                                           Ocean, near the Somalia    as Madden-Julian Oscillations
        along with its southern    The irregular behaviour of the   rainfall and can have a direct   (2002, 2004, 2009, 2014 and   coast, experiences higher   (MJOs) are the dominant
        border touching the Indian   Monsoon that disrupt the   impact on the nation's    2015) compared to the 2              SSTs compared to that over   component of the
        Ocean, create distinct climatic   usual rainfall patterns are   economy. Consequently,   excess years (2007 & 2019).   the eastern Indian Ocean, it   intra-seasonal variability (ISV)
        patterns marked by a       referred together as the   comprehending and           The deficient and excess             signifies a positive IOD, which   in the tropical atmosphere. It
        pronounced contrast        unpredictability of the    forecasting monsoon         years are identified based on        tends to be conducive for the   consists of large-scale
        between land and sea. The   monsoon. These variations in   fluctuations stands as one of   the departure of AISMR      stronger than normal Indian   coupled patterns in
        period spanning from June to   the monsoon stem from the   the most formidable    beyond ± 1 SD, which is ≈ 10         monsoon. Conversely, a     atmospheric circulation and
        September, known as the    intricate interactions among   challenges in the field of   per cent of its seasonal        negative IOD phase is results   deep convection, propagating
        Southwest Monsoon season   the land, atmosphere, and   atmospheric science today.  average AISMR of 87 cm              weaker than normal Indian   eastward slowly (~5 m/s)
        (JJAS), brings with it a mix of   ocean components of the                         (Average of 1971 to 2020).           monsoon.                   through the Indian and Pacific   Dr M. Mohapatra,  Director General of Meteorology,
        droughts and floods, an    climate system. They                  The interannual   The atmospheric-ocean                                          oceans where the sea surface            India Meteorological Department, New Delhi
        alternating pattern of active   result from factors                variability of   coupled phenomenon like El          THE VARIATION IN          is warm.
        and break phases in the    like the premature                       All India     Niño–Southern Oscillation             RAINFALL WITHIN THE
        monsoon, and heavy rainfall   onset or delayed                      Summer        (ENSO) is one of the major                                      Considering the importance
        across different regions of the   withdrawal of rain,               Monsoon       drivers of the interannual            SUMMER MONSOON            of prediction of monsoon on
        country. The monsoon, an   which can devastate                       Rainfall     variability of AISMR. ENSO            SEASON IS KNOWN AS        different time scales, IMD has    Contributed by:
        annual visitor, arrives    crops and                                 (AISMR)      refers to the large-scale             THE INTRA-SEASONAL        implemented various               Dr  D. R. Pattanaik, Scientist - F, India
        consistently but not always   subsequently slow                      during the   ocean-atmosphere climate              VARIATION OF              numerical models to forecast      Meteorological Department, New Delhi
        with the same intensity.   down economic                            last 22       interaction linked to periodic        MONSOON                   the monsoon rainfall in short
        Hence, each summer, not only   growth. Beyond                       years         variation in the winds and sea                                  range (up to 3 days), medium      Dr D. S. Pai, Scientist -G, India
        meteorologists and farmers   agriculture, a                       consists of 5   surface temperatures (SSTs)          In addition to the interannual   range (up to 10 days),      Meteorological Department, New Delhi
        but also economists are    multitude of sectors in                deficient years   across the central and             variability of AISMR, there is   extended range (up to 4
        preoccupied with the       India are closely linked                               east-central Equatorial Pacific.     also variation in rainfall within   weeks), and seasonal time   Dr M. Mohapatra, Director General of
        question of how the        to monsoon                                                                                  the summer monsoon season   scales to provide services to    Meteorology,  India Meteorological
        monsoon will behave that                                                                                               from Jun to Sep and it is   agriculture, water resource,     Department, New Delhi
        year. This concern is rooted in                                            Dr  D. R. Pattanaik,  Scientist - F         commonly known as the      disaster management and
        the profound significance of                                       India Meteorological Department, New Delhi          intra-seasonal variation of   many other sectors.
                                                                                                                               monsoon. The intra-seasonal
        06   ANALYSIS, RESEARCH, THOUGHT LEADERSHIP & ADVOCACY                                                                                                                                               ANALYSIS, RESEARCH, THOUGHT LEADERSHIP & ADVOCACY  07
                                                                                                                                                                                                                  QUARTERLY JOURNAL OF ECONOMICS
             QUARTERLY JOURNAL OF ECONOMICS
             SEPTEMBER 2023                                                                                                                                                                                                 SEPTEMBER 2023
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