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Analysis of the Characteristics of 30-60 Day Low-Frequency Oscillation over Asia during 1998 SCSMEX


doi: 10.1007/s00376-001-0050-0

  • The wavelet analysis is performed of the mid- and low-latitude circulation index at 850 hPa over East Asia, the East Asian monsoon index and the precipitation over the middle and lower reaches of the Yangtze River during 1998 South China Sea Monsoon Experiment (SCSMEX) from May to August. Analysis shows that distinct 30-60 day low-frequency oscillation (LFO) exists in all of the above elements during the exper iment period. Analysis of low-frequency wind field at 850 hPa from May to August with 5 days interval is performed in this paper. Analysis results reveal that: (1)A low-frequency monsoon circulation system over East Asia, characterized by distinct 30-60 day low-frequency oscillation, exists over 100°-lS0°E of East Asian area from the middle and eastern parts of China continent and the South China Sea to the western Pacific in both the Northern and Southern Hemisphere. The activity of East Asian monsoon is mainly affected by the low-frequency systems in it; (2) All of the tropical monsoon onset over the South China Sea in the fifth pentad of May, the beginning of the Meiyu period and heavy rainfall over the middle and lower reaches of the Yangtze River in mid-June and the heavy rainfall after mid-July are related to the activity of low-frequency cyclone belt over the region, whereas the torrential rainfall over the upper reaches of the Yangtze River in August is associated with the westward propagation of low-frequency anticyclone into the mainland; (3) There are two sources of low-frequency oscillation system over East Asia during SCSMEX. i.e. the equatorial South China Sea (SCS) and mid-high latitudes of the middle Pacific in the Northern Hemisphere. The low-frequency system over SCS propagates northward while that in mid-high latitudes mainly propagates from northeast to southwest. Both of the heavy rainfall over the middle and lower reaches of the Yangtze River in June and July are associated with the northward propagation of the above-mentioned SCS low-frequency systems from the tropical region and the southwestward propagation from mid-high latitudes respectively and their convergence in the middle and lower reaches of the Yangtze River; (4) There are two activities of iow-frequency cyclone and anticyclone belt each in the East Asian monsoon system during May to August. However the activity of these low-frequency circulation systems is not clearly relevant to the low-frequency circulation system in the Indian monsoon system. This means that the low-frequency circulation systems in Indian monsoon and East Asian monsoon are independent of each other. The concept previously put forward by Chinese scholars that the East Asian monsoon circulation system (EAMCS) is relatively independent monsoon circulation system is testified once more in the summer 1998.
  • [1] Wang Shiyu, QianYongfu, 2000: Diagnostic Study of Apparent Heat Sources and Moisture Sinks in the South China Sea and Its Adjacent Areas during the Onset of 1998 SCS Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 17, 285-298.  doi: 10.1007/s00376-000-0010-0
    [2] Li Chongyin, Wu Jingbo, 2000: On the Onset of the South China Sea Summer Monsoon in 1998, ADVANCES IN ATMOSPHERIC SCIENCES, 17, 193-204.  doi: 10.1007/s00376-000-0003-z
    [3] Jiapeng MIAO, Tao WANG, Huijun WANG, Yongqi GAO, 2018: Influence of Low-frequency Solar Forcing on the East Asian Winter Monsoon Based on HadCM3 and Observations, ADVANCES IN ATMOSPHERIC SCIENCES, 35, 1205-1215.  doi: 10.1007/s00376-018-7229-0
    [4] LI Chongyin, PAN Jing, 2006: Atmospheric Circulation Characteristics Associated with the Onset of Asian Summer Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 23, 925-939.  doi: 10.1007/s00376-006-0925-1
    [5] Gill M. MARTIN, Amulya CHEVUTURI, Ruth E. COMER, Nick J. DUNSTONE, Adam A. SCAIFE, Daquan ZHANG, 2019: Predictability of South China Sea Summer Monsoon Onset, ADVANCES IN ATMOSPHERIC SCIENCES, 36, 253-260.  doi: 10.1007/s00376-018-8100-z
    [6] He Jinhai, Zhou Xueming, Ye Rongsheng, 1995: Numerical Study of Ural Blocking High’s Effect Upon Asian Summer Monsoon Circulation and East China Flood and Drought, ADVANCES IN ATMOSPHERIC SCIENCES, 12, 361-370.  doi: 10.1007/BF02656985
    [7] Shao Hui, Qian Yongfu, 2000: Main Features of Regional Circulation Variation during Onset of the South China Sea Monsoon in 1998, ADVANCES IN ATMOSPHERIC SCIENCES, 17, 322-338.  doi: 10.1007/s00376-000-0013-x
    [8] DING Yihui, HE Chun, 2006: The Summer Monsoon Onset over the Tropical Eastern Indian Ocean: The Earliest Onset Process of the Asian Summer Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 23, 940-950.  doi: 10.1007/s00376-006-0940-2
    [9] D.R. Chakraborty, N.K. Agarwal, 1996: Role of Triad Kinetic Energy Interactions for Maintenance of Upper Tropospheric Low Frequency Waves during Summer Monsoon 1988, ADVANCES IN ATMOSPHERIC SCIENCES, 13, 91-102.  doi: 10.1007/BF02657030
    [10] FENG Junqiao, HU Dunxin, YU Lejiang, 2013: Role of Western Pacific Oceanic Variability in the Onset of the Bay of Bengal Summer Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 30, 219-234.  doi: 10.1007/s00376-012-2040-9
    [11] Yanying CHEN, Ning JIANG, Yang AI, Kang XU, Longjiang MAO, 2023: Influences of MJO-induced Tropical Cyclones on the Circulation-Convection Inconsistency for the 2021 South China Sea Summer Monsoon Onset, ADVANCES IN ATMOSPHERIC SCIENCES, 40, 262-272.  doi: 10.1007/s00376-022-2103-5
    [12] Wei Helin, Wang Wei-Chyung, 1998: A Regional Climate Model Simulation of Summer Monsoon over East Asia: A Case Study of 1991 Flood in Yangtze-Huai River Valley, ADVANCES IN ATMOSPHERIC SCIENCES, 15, 489-509.  doi: 10.1007/s00376-998-0027-3
    [13] P. P. BABURAJ, S. ABHILASH, K. MOHANKUMAR, A. K. SAHAI, 2020: On the Epochal Variability in the Frequency of Cyclones during the Pre-Onset and Onset Phases of the Monsoon over the North Indian Ocean, ADVANCES IN ATMOSPHERIC SCIENCES, 37, 634-651.  doi: 10.1007/s00376-020-9070-5
    [14] LIU Peng, QIAN Yongfu, HUANG Anning, 2009: Impacts of Land Surface and Sea Surface Temperatures on the Onset Date of the South China Sea Summer Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 26, 493-502.  doi: 10.1007/s00376-009-0493-2
    [15] BAO Qing, LIU Yimin, SHI Jiancheng, WU Guoxiong, 2010: Comparisons of Soil Moisture Datasets over the Tibetan Plateau and Application to the Simulation of Asia Summer Monsoon Onset, ADVANCES IN ATMOSPHERIC SCIENCES, 27, 303-314.  doi: 10.1007/s00376-009-8132-5
    [16] ZHOU Wen, Johnny Chung-Leung CHAN, LI Chongyin, 2005: South China Sea Summer Monsoon Onset in Relation to the Off-Equatorial ITCZ, ADVANCES IN ATMOSPHERIC SCIENCES, 22, 665-676.  doi: 10.1007/BF02918710
    [17] HE Jinhai, WEN Min, WANG Lijuan, XU Haiming, 2006: Characteristics of the Onset of the Asian Summer Monsoon and the Importance of Asian-Australian “Land Bridge”, ADVANCES IN ATMOSPHERIC SCIENCES, 23, 951-963.  doi: 10.1007/s00376-006-0951-z
    [18] HUANG Ronghui, GU Lei, ZHOU Liantong, WU Shangsen, 2006: Impact of the Thermal State of the Tropical Western Pacific on Onset Date and Process of the South China Sea Summer Monsoon, ADVANCES IN ATMOSPHERIC SCIENCES, 23, 909-924.  doi: 10.1007/s00376-007-0100-3
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    [20] ZOU Liwei, ZHOU Tianjun, 2015: Asian Summer Monsoon Onset in Simulations and CMIP5 Projections Using Four Chinese Climate Models, ADVANCES IN ATMOSPHERIC SCIENCES, 32, 794-806.  doi: 10.1007/s00376-014-4053-z

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Manuscript received: 10 July 2001
Manuscript revised: 10 July 2001
通讯作者: 陈斌, bchen63@163.com
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Analysis of the Characteristics of 30-60 Day Low-Frequency Oscillation over Asia during 1998 SCSMEX

  • 1. Chinese Academy of Meteorological Sciences, Beijing 100081,Chinese Academy of Meteorological Sciences, Beijing 100081,Chinese Academy of Meteorological Sciences, Beijing 100081,National Climate Center, Beijing 100081

Abstract: The wavelet analysis is performed of the mid- and low-latitude circulation index at 850 hPa over East Asia, the East Asian monsoon index and the precipitation over the middle and lower reaches of the Yangtze River during 1998 South China Sea Monsoon Experiment (SCSMEX) from May to August. Analysis shows that distinct 30-60 day low-frequency oscillation (LFO) exists in all of the above elements during the exper iment period. Analysis of low-frequency wind field at 850 hPa from May to August with 5 days interval is performed in this paper. Analysis results reveal that: (1)A low-frequency monsoon circulation system over East Asia, characterized by distinct 30-60 day low-frequency oscillation, exists over 100°-lS0°E of East Asian area from the middle and eastern parts of China continent and the South China Sea to the western Pacific in both the Northern and Southern Hemisphere. The activity of East Asian monsoon is mainly affected by the low-frequency systems in it; (2) All of the tropical monsoon onset over the South China Sea in the fifth pentad of May, the beginning of the Meiyu period and heavy rainfall over the middle and lower reaches of the Yangtze River in mid-June and the heavy rainfall after mid-July are related to the activity of low-frequency cyclone belt over the region, whereas the torrential rainfall over the upper reaches of the Yangtze River in August is associated with the westward propagation of low-frequency anticyclone into the mainland; (3) There are two sources of low-frequency oscillation system over East Asia during SCSMEX. i.e. the equatorial South China Sea (SCS) and mid-high latitudes of the middle Pacific in the Northern Hemisphere. The low-frequency system over SCS propagates northward while that in mid-high latitudes mainly propagates from northeast to southwest. Both of the heavy rainfall over the middle and lower reaches of the Yangtze River in June and July are associated with the northward propagation of the above-mentioned SCS low-frequency systems from the tropical region and the southwestward propagation from mid-high latitudes respectively and their convergence in the middle and lower reaches of the Yangtze River; (4) There are two activities of iow-frequency cyclone and anticyclone belt each in the East Asian monsoon system during May to August. However the activity of these low-frequency circulation systems is not clearly relevant to the low-frequency circulation system in the Indian monsoon system. This means that the low-frequency circulation systems in Indian monsoon and East Asian monsoon are independent of each other. The concept previously put forward by Chinese scholars that the East Asian monsoon circulation system (EAMCS) is relatively independent monsoon circulation system is testified once more in the summer 1998.

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