Detecting Source Regions of Wave Activities in the Tropical Atmosphere by Applying Beamforming to Interpolated Data Grids

Qi Hu School of Natural Resources, and Department of Geosciences, University of Nebraska at Lincoln, Lincoln, Nebraska

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Zhaoning Liang School of Natural Resources, and Department of Geosciences, University of Nebraska at Lincoln, Lincoln, Nebraska

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Michael W. Hoffman Department of Electrical Engineering, University of Nebraska at Lincoln, Lincoln, Nebraska

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Abstract

Wave activities are primary sources of weather disturbances and cyclones in the tropical atmosphere. One such activity is the intraseasonal variations in wind, convection, and precipitation in the tropical Indian and western tropical Pacific region. These variations affect the intensity, break and reset, and rainfall in the Indian and the East Asian monsoons. Detecting the source regions of these wave activities is essential for understanding and for prediction of wave development. In this study, a fixed beamforming method is proposed to deduce source regions of some wave activities in the tropical atmosphere. This method is tested with simulations of single and distributed complex sources of waves and, then, fixed beamformers are applied to the ECMWF interpolated data grids to detect and identify source regions of the intraseasonal oscillations–waves in the tropical Indian and tropical Pacific Ocean region. Results show that the fixed beamforming technique can uniquely identify the source regions of the intraseasonal oscillations. Applications of this method have revealed various source regions of all major intraseasonal oscillation (ISO) events in the tropical Indian and western equatorial Pacific region during the 29 yr from 1974 to 2002. Knowing these source regions will make it possible to extract the relevant information and, thus, to better understand the development of the intraseasonal oscillations as well as their effects on the tropical weather and climate.

Corresponding author address: Dr. Qi Hu, University of Nebraska at Lincoln, 707 Hardin Hall, Lincoln, NE 68583-0987. Email: qhu2@unl.edu

Abstract

Wave activities are primary sources of weather disturbances and cyclones in the tropical atmosphere. One such activity is the intraseasonal variations in wind, convection, and precipitation in the tropical Indian and western tropical Pacific region. These variations affect the intensity, break and reset, and rainfall in the Indian and the East Asian monsoons. Detecting the source regions of these wave activities is essential for understanding and for prediction of wave development. In this study, a fixed beamforming method is proposed to deduce source regions of some wave activities in the tropical atmosphere. This method is tested with simulations of single and distributed complex sources of waves and, then, fixed beamformers are applied to the ECMWF interpolated data grids to detect and identify source regions of the intraseasonal oscillations–waves in the tropical Indian and tropical Pacific Ocean region. Results show that the fixed beamforming technique can uniquely identify the source regions of the intraseasonal oscillations. Applications of this method have revealed various source regions of all major intraseasonal oscillation (ISO) events in the tropical Indian and western equatorial Pacific region during the 29 yr from 1974 to 2002. Knowing these source regions will make it possible to extract the relevant information and, thus, to better understand the development of the intraseasonal oscillations as well as their effects on the tropical weather and climate.

Corresponding author address: Dr. Qi Hu, University of Nebraska at Lincoln, 707 Hardin Hall, Lincoln, NE 68583-0987. Email: qhu2@unl.edu

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