Influences of MJO on the Diurnal Variation and Associated Offshore Propagation of Rainfall near Western Coast of Sumatra
Madden-Julian Oscillation (MJO) plays an important role in modulating precipitation at Maritime Continent (MC) not only on a larger scale, but also in the diurnal cycle. Diurnal rainfall offshore propagation is one of the most evident features near coasts. This study investigates the impacts of MJO...
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| Format: | Article |
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MDPI AG
2022-02-01
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| Series: | Atmosphere |
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| Online Access: | https://www.mdpi.com/2073-4433/13/2/330 |
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| author | Bojun Zhu Yu Du Zhiqiu Gao |
| author_facet | Bojun Zhu Yu Du Zhiqiu Gao |
| author_sort | Bojun Zhu |
| collection | DOAJ |
| description | Madden-Julian Oscillation (MJO) plays an important role in modulating precipitation at Maritime Continent (MC) not only on a larger scale, but also in the diurnal cycle. Diurnal rainfall offshore propagation is one of the most evident features near coasts. This study investigates the impacts of MJO on diurnal rainfall and its offshore propagation at the western coast of Sumatra during boreal winters using ERA5 reanalysis. The real-time multivariate MJO (RMM) index was applied to locate the active MJO convection through eight different phases, in the western hemisphere and Africa in P8–P1, at the Indian Ocean in P2–P3, at MC in P4–P5, and the western Pacific Ocean in P6–P7. The rainfall characteristics, including the daily rate, the absolute and normalized diurnal variation amplitudes, and the strengths of diurnal offshore propagation, not only depend on active/inactive MJO stages but also vary under different MJO phases, through the combined modulations of large-scale backgrounds and local-scale land–sea circulations. The offshore rainfall propagation is associated with meso-large-scale gravity waves generated from land–sea thermal contrast and thus is affected by the radiation effect of cloud under different MJO phases. The stronger wave signals in P8–P1 and P6–P7 enhance the diurnal rainfall variation amplitudes away from the coast, while the strong coupling of moist convection with gravity waves contributes greatly to the diurnal rainfall cycle in P2–P3. |
| first_indexed | 2024-03-09T22:37:46Z |
| format | Article |
| id | doaj.art-6bd549c3ec9240cab608f4a50f7ec5ac |
| institution | Directory Open Access Journal |
| issn | 2073-4433 |
| language | English |
| last_indexed | 2024-03-09T22:37:46Z |
| publishDate | 2022-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Atmosphere |
| spelling | doaj.art-6bd549c3ec9240cab608f4a50f7ec5ac2023-11-23T18:45:56ZengMDPI AGAtmosphere2073-44332022-02-0113233010.3390/atmos13020330Influences of MJO on the Diurnal Variation and Associated Offshore Propagation of Rainfall near Western Coast of SumatraBojun Zhu0Yu Du1Zhiqiu Gao2Climate and Weather Disasters Collaborative Innovation Center, School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, ChinaSchool of Atmospheric Sciences, and Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Zhuhai 519082, ChinaClimate and Weather Disasters Collaborative Innovation Center, School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, ChinaMadden-Julian Oscillation (MJO) plays an important role in modulating precipitation at Maritime Continent (MC) not only on a larger scale, but also in the diurnal cycle. Diurnal rainfall offshore propagation is one of the most evident features near coasts. This study investigates the impacts of MJO on diurnal rainfall and its offshore propagation at the western coast of Sumatra during boreal winters using ERA5 reanalysis. The real-time multivariate MJO (RMM) index was applied to locate the active MJO convection through eight different phases, in the western hemisphere and Africa in P8–P1, at the Indian Ocean in P2–P3, at MC in P4–P5, and the western Pacific Ocean in P6–P7. The rainfall characteristics, including the daily rate, the absolute and normalized diurnal variation amplitudes, and the strengths of diurnal offshore propagation, not only depend on active/inactive MJO stages but also vary under different MJO phases, through the combined modulations of large-scale backgrounds and local-scale land–sea circulations. The offshore rainfall propagation is associated with meso-large-scale gravity waves generated from land–sea thermal contrast and thus is affected by the radiation effect of cloud under different MJO phases. The stronger wave signals in P8–P1 and P6–P7 enhance the diurnal rainfall variation amplitudes away from the coast, while the strong coupling of moist convection with gravity waves contributes greatly to the diurnal rainfall cycle in P2–P3.https://www.mdpi.com/2073-4433/13/2/330MJOrainfalldiurnal variationland–sea circulationgravity wave |
| spellingShingle | Bojun Zhu Yu Du Zhiqiu Gao Influences of MJO on the Diurnal Variation and Associated Offshore Propagation of Rainfall near Western Coast of Sumatra Atmosphere MJO rainfall diurnal variation land–sea circulation gravity wave |
| title | Influences of MJO on the Diurnal Variation and Associated Offshore Propagation of Rainfall near Western Coast of Sumatra |
| title_full | Influences of MJO on the Diurnal Variation and Associated Offshore Propagation of Rainfall near Western Coast of Sumatra |
| title_fullStr | Influences of MJO on the Diurnal Variation and Associated Offshore Propagation of Rainfall near Western Coast of Sumatra |
| title_full_unstemmed | Influences of MJO on the Diurnal Variation and Associated Offshore Propagation of Rainfall near Western Coast of Sumatra |
| title_short | Influences of MJO on the Diurnal Variation and Associated Offshore Propagation of Rainfall near Western Coast of Sumatra |
| title_sort | influences of mjo on the diurnal variation and associated offshore propagation of rainfall near western coast of sumatra |
| topic | MJO rainfall diurnal variation land–sea circulation gravity wave |
| url | https://www.mdpi.com/2073-4433/13/2/330 |
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