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BIBLIOGRAPHY

Title: Classification and seasonal distribution of rain types based on surface and radar observations over a
tropical coastal station

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Author and Affiliation: Sreekanth T S, Hamza Varikoden, Resmi E A , Mohan Kumar G, National Centre for
Earth Science Studies, Akkulam, Thiruvananthapuram
Journal: Atmospheric Research Vol. 218 pp. 90-98.
Abstract: An attempt has been made to classify stratiformstratiform and convective rain using an impact type disdrometer
at a tropical coastal site based on (Testud et al., 2001) method . Using this classification scheme, all rain events
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were analysed and computed their duration (minutes) and accumulated water (mm) in convective, stratiform,
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transition and mixed rain types. For the first time, in this paper an atmospheric electric field mill was used for
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rain type classification.
The classification results were confirmed with disdrometer,disdrometer, Micro Rain Radar (MRR), and atmospheric electric
field mill (EFM) observations. In convective rain type, non-bright band and high electric field were
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correspondingly observed in MRR and EFM records. Whereas bright band and shallow electric fields were
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detected during stratiform rain in the above observations of instruments. Other supporting evidences were
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observed from disdrometer also in corresponding rain types.
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Seasonal variations in rain duration and associated accumulated water were investigated in the four seasons
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(winter, pre-monsoon, summer monsoon and post-monsoon) for different rain types. General and mixed rain
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events were identified depending on the presence of stratiform or convective type in them. Percentage of rain
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duration and events for the study period were analysed with respect to (a) mean monthly rain water availability
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and (b) the intensity pattern in the total rainfall encountered in each month.
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Among the four seasons, summer monsoon received maximum rainfall followed by post-monsoon. A bimodal
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variation in the rainfall with a primary peak in June and secondary peak in October was observed in the annual
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cycle. Rainfall was intense during the pre- and post-monsoon seasons and less intense during the summer
monsoon season. Also, shorter duration rain events were repeated in summer monsoon and fewer rain events of
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longer duration are resulted during pre- and post-monsoon seasons.
In this duration, mixed rain accounts second higher in all the seasons. It was more evident in summer monsoon
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and least in post-monsoon. Rainfall contribution from convective rain was dominant in all the seasons except in
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winter. In summer monsoon, mixed and transition rain types have contributed much water among the four
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seasons. In mixed and transition rain types, mixed rain contributed more in duration and transition contributed
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more to water. From day-night variation analysis, it was observed that there was day-high and night-low in pre-
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monsoon and its reversal in post-monsoon season, with almost same occurrence during the summer monsoon. In
the case of number of rain events, general (mixed) events were less (more) during the summer monsoon. From
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statistical analyses, an increase was observed in the duration of rain events from winter to post-monsoon. About
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20% of duration was aggregated by longer duration events in all the seasons except during the winter.
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