Inter-annual Variation of Summer Southwest Monsoon Rainfall over the Monsoon Core Region of the Eastern Bay of Bengal and its Relationship with Oceans

Kyaw  Than Oo; Jonah Kazora

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Authors

Kyaw Than Oo , Jonah Kazora

Abstract

Using rainfall data from the Observation and, ERA5 reanalysis of sea surface temperature, this study examined the inter-annual variation of summer southwest monsoon rainfall on the eastern Bay of Bengal (BoB) mainland Indochina regions associated with ENSO. The composite study exhibits decreased rainfall in the eastern coastal region of BoB, and an increase in the northern Indo-Myanmar region during the developing phase of El Nino, but vice versa during the decay phase. Morlet wavelet power-spectrum analysis was performed on normalized rainfall anomalies to investigate the presence of significant signals that might be embedded in the study period. Further correlation analysis demonstrates that abnormal rainfall in the above two regions is controlled by different mechanisms. The Monsoon Core region rainfall anomaly is related to local convection and water vapor flux in the developing phase of El Niño. The anomalous anticyclone circulation in the upper troposphere helps strengthen rainfall. A strong/weak Myanmar southwest monsoon (MSwM) in the developing or decaying phase of El Niño can bring excess/less moisture to wet/dry the local southwest summer rainfall. In northern Indo-Myanmar, the anomalous rainfall is not only on the intensity of the MSwM but also on the frequency of western disturbances, and further findings need to be studied.

DOI

https://doi.org/10.31223/X5ZD54

Subjects

Oceanography and Atmospheric Sciences and Meteorology

Keywords

Mainland Indochina, Southwest Monsoon, rainfall, ENSO, MSwM

Dates

Published: 2023-09-22 22:57

Last Updated: 2023-09-23 02:57

License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
Source Data Reanalysis rainfall, SST netcdf4 data for this study were downloaded from the ECMWF data portal. This is a fifth-generation ECMWF reanalysis dataset with a geographical resolution of 0.25°x0.25° for global climate parameters over the previous decades are used to support the findings of this study and are included within the article. Data is now freely available from 1950 to the present by registration at ECMWF https://cds.climate.copernicus.eu/cdsapp#!/home. The actual monthly rainfall observation data from 79 observation stations used to support the findings of this study was provided under permission by Myanmar's Department of Meteorology and Hydrology (DMH) and hence cannot be freely distributed. Requests for access to these data should be made to the Director-General of DMH, Myanmar. https://www.moezala.gov.mm/ Software availability Open Grads (OpenGrADS - Home), Climate data operator (https://code.mpimet.mpg.de/ ), and IBM SPSS are mainly used for this study. Among these first two are open-source applications for everyone.

Conflict of interest statement:
I declared that there is no potential conflict of interest with any of the following statements. 1. For any component of the submitted work, the author received no cash or services from a third party (government, commercial, private foundation, etc.). (including but not limited to grants, data monitoring board, study design, manuscript preparation, statistical analysis, etc.). 2. The author is not affiliated with any entity that has a direct or indirect financial interest in the manuscript's subject matter. 3. The author was involved in the following aspects of the project: (a) idea and design, or data analysis and interpretation (b) authoring the article or critically reviewing it for essential intellectual content and (c) approval of the final version. 4. This work has not been submitted to and is not currently being reviewed by, any other journal or publishing venue. 5. The author has no patents that are broadly relevant to the work, whether proposed, pending, or issued. 6. The author received no payment or services from a third party for any aspect of the submitted work (government, commercial, private foundation, etc.). (including but not limited to grants, data monitoring board, study design, manuscript preparation, statistical analysis, etc.).