Mean diurnal cycle of monsoon precipitation: Unified model NCUM
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Mean diurnal cycle of monsoon precipitation: Unified model NCUM D. Rajan1 · Sandeep Pattnaik2 · Sagili Karunasagar1 Received: 19 November 2019 / Accepted: 17 October 2020 © Springer Nature Switzerland AG 2020
Abstract It is an essential component of the operational weather forecast agencies to capture the diurnal behavior of the rainfall on the spatiotemporal scale by numerical models for its accurate prediction. In this study, the mean diurnal cycle of precipitation is investigated with (i) atmospheric model-based predictions, (ii) space-based estimates, and (iii) ground-based rainfall observations during the active phase of Indian monsoon. Further, high-resolution precipitation data are used to identify the characteristics features of the model forecasts. The variability of mean diurnal variations in rain rate and frequency of rain is analyzed to determine the characteristics feature of precipitation. It is found that precipitation activity over Western Ghats, Bay of Bengal regions, is maximum during late afternoon. The time of peak rain rate is advanced during day time. The active phase of monsoon has the highest amplitude of diurnal variation in precipitation. The variability in the specific humidity is increased during this active period. The numbers of rainy hours are highly varying in nature for the space-based rainfall estimation than the model. Keywords Indian summer monsoon · Diurnal cycle of rainfall · Active period · Amplitude · Rainy hours
Introduction The diurnal variation of precipitation over any region is related to physical processes governed by various features such as dynamics and geographical futures over that region. The pattern of diurnal variation of rainfall is not unique. It will change from season to season as the circulation pattern will also change which leads to changes in the physical processes (Basu 2007). India receives more than 80% of its annual rainfall from the summer monsoon season (Rajeevan et al. 2010). Being an agricultural country, monsoon rainfall over India plays a major role in its economy. During the summer monsoon season, the presence of monsoon trough in the surface levels and anti-cyclone at upper levels over the Tibetan Plateau can play a major role to alter the physical * D. Rajan [email protected] Sandeep Pattnaik [email protected] Sagili Karunasagar [email protected] 1
NCMRWF, Ministry of Earth Sciences, Noida 201301, Uttar Pradesh, India
Indian Institute of Technology, Bhubaneswar, India
2
process over India. Also, the northward propagation of the Inter Tropical Convergence Zone (ITCZ) can form a convective band over the entire parts of Indian country from June to August. In September, ITCZ starts its southward propagation, and hence, the cease of rainfall starts over the Indian country. Due to the above circulations, the low-level jet will completely establish throughout the Indian country. A small perturbation is enough to make convective clouds over this reason as this region as LLJ is enriched with moisture. Basu (20
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