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Study of statistical estimated parameters using ERA5 reanalysis data over Khulna region during monsoon season

Koutavarapu Ravindranadh, Umakanth N., Satyanarayana T., Kumar M. Seshu, Rao M. C., Lee Dong‑Yeon, Shim Jaesool

Acta Geophysica

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2021

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Vol. 69, no. 5

1963--1978

EN

Thunderstorms are extreme localized weather phenomena that form primarily as a result of intense atmospheric convection. These are characterized by heavy rainfall, lightning and thunder. Thunderstorms occur in monsoon season over some parts of the world, and they can be found in the rain bands of many convective systems. Thunderstorms are a natural weather occurrence that results in significant damage to property and people all over the world. Lifted index, K index, total totals index, humidity index (HI), total precipitable water (TPW), convective available potential energy, deep convective index, S index, maximum temperature and rainfall parameters are investigated over Khulna region in Bangladesh during the monsoon season. We have measured all the above parameters using daily ERA5 reanalysis data for the monsoon season from 2011 to 2020. High TPW values (~>60 mm) and low HI values (~<20 K) are observed during July and August months over Khulna region. DCI values greater than 30 °C are observed which indicates highly favorable for severe convection-related thunderstorms. We have experimented ARMA model to estimate four parameters. The major motive behind this is to compare the accuracy of the ARMA model data to ERA5 data. For obtaining reliable statistical estimates of thunderstorm parameters, the ARMA model proved to be extremely useful.

2

Long term analysis of thunderstorm related parameters over Visakhapatnam and Machilipatnam, India

Umakanth N., Satyanarayana G. Ch., Simon B., Rao M. C., Babu N. Ranga

Acta Geophysica

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2020

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Vol. 68, no. 3

921--932

EN

In this present work, an attempt has been made to analyze various thunderstorm-related parameters and their infuence over the two stations Visakhapatnam (VSK) and Machilipatnam (MTM). The thunderstorm-related parameters used in the present study are convective available potential energy (CAPE), lifted index, K-index, total totals index (TTI), humidity index, convective inhibition, thunderstorm prediction index (TPI), deep convective index (DCI) and updraft vertical velocity. This analysis was carried out using NCEP NCAR reanalysis monthly data for the time period from 1948 to 2012. These parameters have given good guidance for studying the thunderstorm event. We also analyzed IMD thunderstorm occurrence days reported at two stations, i.e., VSK and MTM with NCEP NCAR (daily data) calculated CAPE, TTI, TPI and DCI parameter threshold days in pre-monsoon season for every year during the time period 2010 to 2019. Out of those four parameters, TTI has shown good correlation with the IMD recorded days. So we have attempted the prediction of thunderstorms using artifcial neural network (ANN) and auto-regressive moving average (ARMA) techniques for TTI parameter. While using these techniques, we have experimented in three training sets, i.e., 90%, 80% and 70%. Another attempt has been made to assess the skill of ARMA and ANN techniques in forecasting the occurrence of thunderstorm activity at VSK and MTM stations. The present study suggests that ANN has high skill than ARMA. From this study, we can understand that VSK has more chances for thunderstorms than MTM.

3

Analysis of various thermodynamic instability parameters and their association with the rainfall during thunderstorm events over Anakapalle (Visakhapatnam district), India

Umakanth N., Satyanarayana G. Ch., Simon B., Rao M. C., Kumar M. Tanooj, Babu N. Ranga

Acta Geophysica

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2020

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Vol. 68, no. 5

1549--1564

EN

Thunderstorm events usually take place in cumulonimbus clouds which are complemented with intense rainfall and highspeed winds. In general, rainfall parameter has massive signifcance when compared to other parameters. In this paper, a group of thunderstorm-related stability parameters were analyzed for pre-monsoon season only. Later, we also tried to study the association between thunderstorm-related stability parameters and rainfall parameter in pre-monsoon season over Anakapalle (Visakhapatnam district) during 2001–2010. We have utilized ERA-Interim ECMWF reanalysis daily datasets for this study. We also tried to compare IMD thunderstorm occurrence days with NOAA CPC-calculated rainfall days in pre-monsoon season over Anakapalle region for every year during 2001–2010. Out of those parameters, upward vertical velocity, convective available potential energy, K-index (KI), humidity index and total totals index parameters have shown good thresholds supporting the rainfall activity during pre-monsoon season. Later, we have also attempted the prediction of DCI and KI parameters over Anakapalle region using artifcial neural network (ANN) and auto-regressive moving average (ARMA) techniques. In comparison between the two techniques, ANN technique has shown good correlation with ERAInterim ECMWF reanalysis data.