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Modulation of the diurnal cycle of rainfall over India by intraseasonal variations of Indian summer monsoon

Deshpande, NR and Goswami, BN (2014) Modulation of the diurnal cycle of rainfall over India by intraseasonal variations of Indian summer monsoon. International Journal of Climatology, 34 (3). pp. 793-807.

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Changes in the amplitude and phase of the diurnal cycle of rainfall due to changes in the background circulation and thermodynamics associated with the intraseasonal variability of Indian summer monsoon have important implications for weather prediction over the region. Hourly rainfall data available at 91 Indian stations for 30years of observations are examined to determine the role of intraseasonal variations of Indian summer monsoon in modulating the diurnal cycle of rainfall over four homogenous regions. Harmonic analysis of the diurnal cycle of rainfall shows predominance of principal harmonic during the break phase of monsoon. During an active phase first two harmonics contribute substantially to the total variance in central parts of the country. It is observed that peak rainfall occurs in the morning hours during both the active and break phases along the West Coast with small diurnal variation in rainfall. Two peaks in the diurnal cycle are observed during active phases over central India. This region shows delay in the occurrence of afternoon peak and rise in rainfall intensity during the break phase of recent years, while, increase in rainfall intensity at all hours during break phases is observed along the West Coast of India in recent years. Further analysis of meteorological parameters indicates that lower-level convergence during late afternoon hours, reduction in geopotential height and increase in specific humidity (850hPa) in central parts of India during morning and evening hours are in phase with the two maxima observed in the diurnal cycle of rainfall in this region. Therefore, spatial variations in daily rainfall pattern during active/break phases can be attributed to orographic effect and heterogeneous convective development in different parts of the country.

Item Type: Article
Additional Information: Copyright of this article belongs to Royal Meteorological Society.
Uncontrolled Keywords: Active/break spells; Daily rainfall patterns; Diurnal cycle; Geo-potential heights; Indian summer monsoon rainfall; Intraseasonal variability; Intraseasonal variations; Meteorological parameters, Climate change; Harmonic analysis; Thermodynamics, Rain, diurnal variation; harmonic analysis; monsoon; precipitation intensity; rainfall; summer, India
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 05 Dec 2014 10:29
Last Modified: 05 Dec 2014 10:29

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