Indian summer monsoon rainfall: Dancing with the tunes of the sun |
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| Institution: | 1. Indian Institute of Astrophysics, Bengaluru 560034, India;2. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA;1. Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China;2. School of Astronomy & Space Science, Nanjing University, Nanjing 210093, China;3. Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Ministry of Education, Nanjing 210093, China;1. Department of Physics, Ben-Gurion University, Beer-Sheva 84105, Israel;2. Department of Physics, National Tsing-Hua University, Hsin-Chu 30013, Taiwan;3. Laboratoire d’Astrophysique de Marseille, Université de Provence, Marseille Cedex 13, France;1. Astronomy Department, National Research Institute of Astronomy and Geophysics, 11421 Helwan, Cairo, Egypt;2. Physics Department, College of Science, Northern Border University, 1321 Arar, Saudi Arabia;3. 1393 Garvin Street, Prince George, BC V2M 3Z1, Canada;1. Pacific Geographical Institute, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok, Russia;2. V.B. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia |
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| Abstract: | There is strong statistical evidence that solar activity influences the Indian summer monsoon rainfall. To search for a physical link between the two, we consider the coupled cloud hydrodynamic equations, and derive an equation for the rate of precipitation that is similar to the equation of a forced harmonic oscillator, with cloud and rain water mixing ratios as forcing variables. Those internal forcing variables are parameterized in terms of the combined effect of external forcing as measured by sunspot and coronal hole activities with several well known solar periods (9, 13 and 27 days; 1.3, 5, 11 and 22 years). The equation is then numerically solved and the results show that the variability of the simulated rate of precipitation captures very well the actual variability of the Indian monsoon rainfall, yielding vital clues for a physical understanding that has so far eluded analyses based on statistical correlations alone. We also solved the precipitation equation by allowing for the effects of long-term variation of aerosols. We tentatively conclude that the net effects of aerosols variation are small, when compared to the solar factors, in terms of explaining the observed rainfall variability covering the full Indian monsoonal geographical domains. |
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| Keywords: | Solar variability Indian summer monsoon variability Solar activity forcing on monsoon Simulations of monsoon rainfall |
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