Abstract
The intra-seasonal variability plays a major role in the inter-annual variability of weather parameters such as rainfall, temperature and pressure which lead to extreme weather events in certain years. The active (more rainy days) and break (less rainy days) periods of Indian summer monsoon heavily depend on the intra-seasonal variability of weather parameters such as wind, pressure and temperature oscillations during the monsoon season. In the present analysis daily total column ozone, surface temperature and surface pressure measured over Cochin using Microtop II Ozonometer (sun Photometer) were used to study the Intra-Seasonal Variations (ISV) of the above parameters during the monsoon season, 2015. The dominant and significant intra-seasonal oscillations (ISOs) were identified using an advanced statistical method called the Discrete Mayer’s Wavelet (DMW) analysis. Two major ISOs such as Madden Julian Oscillations (MJO, 30 - 60 days) and quasi-bi weekly (12 - 16 days) oscillations were found in TCO, surface temperature and pressure. In TCO an additional mode of ISO with quasi tri-weekly periodicity was also found (16 - 22 day). It is observed that MJO mode is the dominant among all other modes and its positive and negative phases correlate with positive and negative anomalies of the above parameters. The ISO mode in the surface pressure shows an out of phase relation with the Indian summer monsoon rainfall which indicates the active and break periods of Indian summer monsoon. The contribution of MJO mode is dominant in the tropical atmosphere, which modulates the intra-seasonal variability. It is found that for the year 2015 total column ozone, surface pressure and surface temperature show an annual range of 30 DU, 4 hPa and 1°C, respectively.
Highlights
The Madden-Julian Oscillation (MJO) is the dominant mode of tropical intra-seasonal variability in the Asiatic monsoon region
The Microtops II measurements of Total Column Ozone (TCO), surface temperature and pressure measured over the tropical station Cochin were used to understand the seasonal variability and intra-seasonal variability for the year 2015
The study focuses on the intra-seasonal variability of total column ozone, surface temperature and pressure during the monsoon season (June-September)
Summary
The Madden-Julian Oscillation (MJO) is the dominant mode of tropical intra-seasonal variability in the Asiatic monsoon region. The MJO is an eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average It connects weather and climate and influences high-impact events around the globe including monsoons, tropical cyclones, tornados, cold surges, flood and wildfires. The Madden Julian Oscillation (MJO) represents the connection between the weather and seasonal-tointerannual climate variations It significantly affects the tropical weather, climate and global atmospheric circulations. There can be multiple MJO events within a season, and so the MJO is best described as intraseasonal tropical climate variability Since it has been called the “30 60-day oscillation” and the “intraseasonal oscillation”, but the term “MJO” has emerged as a favorite in the global climate change scenario. An individual MJO event can last anywhere between 30 and 60 days
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