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![Anomaly composite of OLR overlaid with dot marks statistically significant at 99% confidence level [Colour figure can be viewed at wileyonlinelibrary.com]](profile/A-V-Sreenath/publication/349123415/figure/fig5/AS:11431281245952945@1716258689048/Anomaly-composite-of-OLR-overlaid-with-dot-marks-statistically-significant-at-99.png)
Anomaly composite of OLR overlaid with dot marks statistically significant at 99% confidence level [Colour figure can be viewed at wileyonlinelibrary.com]
Source publication
This study examined factors affecting wet and dry phases of monsoon rainfall over Kerala, using modern‐era retrospective analysis for research and applications (MERRA 2) data set. Based on circulation pattern, our study shows that the wet and dry phases of monsoon over Kerala are related to modulation of convective activity over the eastern equator...
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Citations
... For instance, west coast India has been experiencing decreased light/moderate rainfall days and increased heavy/very heavy rainfall days (Prathipati et al., 2019). The scientific evidence underscores the substantial role of offshore troughs (Viswanadhapalli et al., 2019), strong cross-equatorial flow over the Arabian Sea (Chaluvadi et al., 2021;Sreenath, 2021, Sreenath et al., 2022, and the low-pressure system over the Arabian Sea near Gujarat and Maharashtra coast for enhancing the precipitation amount along the west coast of India (Ray et al., 2019). ...
The inverse relationship between the warm phase of the El Niño Southern Oscillation (ENSO) and the Indian Summer Monsoon Rainfall (ISMR) is well established. Yet, some El Niño events that occur in the early months of the year (boreal spring) transform into a neutral phase before the start of summer, whereas others begin in the boreal summer and persist in a positive phase throughout the summer monsoon season. This study investigates distinct influences of exhausted spring El Niño (springtime) and emerging summer El Niño (summertime) on the regional variability of ISMR. The two ENSO categories were formulated based on the time of occurrence of positive SST anomalies over the Niño-3.4 region in the Pacific. The ISMR's dynamical and thermodynamical responses to such events were investigated using standard metrics such as the Walker and Hadley circulations, vertically integrated moisture flux convergence (VIMFC), wind shear and upper atmospheric circulation. The monsoon circulation features are remarkably different in response to the exhausted spring El Niño and emerging summer El Niño phases, which distinctly dictate regional rainfall variability. The dynamical and thermodynamical responses reveal that exhausted spring El Niño events favour excess monsoon rainfall over eastern peninsular India and deficit rainfall over the core monsoon regions of central India. In contrast, emerging summer El Niño events negatively impact the seasonal rainfall over the country, except for a few regions along the west coast and northeast India.
Large-scale transport of air mass modulates the weather by altering the cloud and precipitation microphysics of convective clouds. This study examines how oceanic and continental air mass advected into the convective cloud system determines hydrometeors' vertical distribution using in situ airborne observations from the Cloud-Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) during 2010. Maritime air mass from the Bay of Bengal favours a clean atmosphere (CA) that supports clouds with fewer droplets, and the effective radius crosses above 12 μm below the 10 °C temperature level. Thus CA is mainly characterised by moderate precipitation efficiency and broader hydrometeors size distribution spectra. The mixing of air mass from the Arabian sea, Bay of Bengal, and central Indian region results in a moderately polluted atmosphere (MPA), enhancing convective cloud depth and favours mixed-phase processes and equally strong updrafts and downdrafts. As the concentration of sea salt, dust particles, moisture content, and convective available potential energy (CAPE) increases, MPA profoundly supports the primary and secondary ice nucleation inside the convective system. Despite CA and MPA, wide hydrometeor size distribution is absent in a highly polluted atmosphere (HPA), primarily evolved from continental air mass. We noticed an absence of larger raindrops inside clouds developed in HPA, indicating reduced collisions, making them less efficient with the precipitation process. The raindrop size distribution under the three environmental conditions showed distinct characteristics, implying contrasting cloud microphysical processes and precipitation efficiency.
