An Anomalous Atmospheric Event during 2019 MISO-BOB Field Campaign

Edgar Gonzalez, University of Notre Dame, Notre Dame, IN, United States, Reneta Dimitrova, University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, Notre Dame, United States; Sofia University "St. Kliment Ohridski", Faculty of Physics, Department of Meteorology and Geophysics, Sofia, Bulgaria, Harindra J.S. Fernando, University of Notre Dame, Notre Dame, United States, Raghavendra Krishnamurthy, Pacific Northwest National Laboratory, Richland, United States, Sandeep Dnyandeo Wagh, University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, Notre Dame, IN, United States, S.U.P. Jinadasa, National Aquatic Resources Research and Development Agenc, Colombo, Sri Lanka, Shiromani Jayawardena, Meteorological Department, Colombo 7, Sri Lanka, Ahmed Muslim, Maldives Meteorological Service, Gan Island, Maldives, Zahid Hameed, Maldives Meteorological Service, Hulhule' 22000, Maldives, Vincent Amelie, Seychelles Meteorological Authority, Mahe, Seychelles and Hemantha W Wijesekera, Naval Research Laboratory, Ocean Sciences, Stennis Space Center, MS, United States
Abstract:
The focus of the 2019 MISO-BOB field campaign conducted from June 1 to July 31 during the southwest monsoons season of the Bay of Bengal (BOB) was the capture of Monsoon Intraseasonal Oscillations (MISO) events. To this end, a comprehensive array of ground measurement stations were deployed in Sri Lanka, Maldives and Seychelles, which included a Doppler lidar, flux tower and ceilometer at each station. During this period, the frequency of radiosonde launches at WMO sites in Maldives and Sri Lanka was significantly increased. Augmenting the land data were those taken from two MISO-BOB ocean cruises aboard R/V Sally Ride, which carried a flux tower (fully instrumented for sensible, latent and radiative fluxes), microwave radiometer, ceilometer, motion-stabilized Dopper lidar, ROSR SST radiometer, sea-snake thermistor chain, tethered lifting system, present weather detector, and vertical microstructure profiler. Radiosonde launches were made at 6 (sometimes 3) hour intervals. While MISO events were rare during the observation period, a few intense weather anomalies of significant interest were observed that might have implications in air-sea interaction studies. A noteworthy anomaly was recorded on July 18 in Sri Lanka, where unusual rainfall (>200 mm) was reported in the catchment areas accompanied by gale force winds (70-80 km/hr) that lasted for several hours. Analysis of wind anomalies in the land stations and from the ship as well as NCAR/NCEP reanalysis products indicate that this owes to a barotropic instability event generated between an eastward propagating planetary wave and a low-latitude westward zonal jet-like flow.
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