Interaction between the Summer Monsoons in East Asia and the South China Sea: Intraseasonal Monsoon Modes

Chen, Tsing Chang; Yen, Ming Cheng; Weng, Shu Ping

doi:10.1175/1520-0469(2000)057<1373:ibtsmi>2.0.co;2

Cited by 108 publications

(85 citation statements)

References 21 publications

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“…Unlike the other bi-weekly (10 -24 day) wave that tends to propagate westward from the Philippine Sea to the Indo-China Peninsula and the Bay of Bengal (Chen and Chen 1995;Chen et al 2000), the TSM is a northwestward-propagating wavelike feature with TC embedded in the cyclonic circulation and the spectrum of this wave-like feature exhibits maxima around 7 -30 days. KHC12 investigated a kinetic energy budget study of the TSM.…”

Section: Introductionmentioning

confidence: 95%

Barotropic Interactions Between Summertime Tropical Cyclones/Sub-Monthly Wave Patterns and Intraseasonal Oscillations over the Western North Pacific

Ko¹,

Hsu²

2014

Terr. Atmos. Ocean. Sci.

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This study used the barotropic kinetic energy conversion to record the active eddy-mean flow interaction between the TC/sub-monthly wave pattern (TSM) and the intraseasonal oscillation (ISO) in the western North Pacific (WNP). Overall, the TSM extracted (lost) kinetic energy from (to) the cyclonic (anticyclonic) circulation of the ISO, which is located in the South China Sea and the Philippine Sea, during the ISO westerly (easterly) phase. The phase change in barotropic energy conversion was due to the opposite background flow set up by the ISO. When the climatological-mean southwesterly was retained as part of the background flow in both ISO westerly and easterly phases as in previous studies, the ISO along with the low-frequency background flow always provided kinetic energy to the TSM regardless of the phase. The stronger (weaker) southwesterly in the ISO westerly (easterly) phase, the stronger (weaker) energy conversion to the TSM. Climatological mean flow exclusion showed an upscale feedback in the TSM to the ISO during the easterly phase. However, this feedback was weaker than the downscale conversion from the ISO to the TSM during the westerly phase.

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Section: Introductionmentioning

confidence: 95%

Barotropic Interactions Between Summertime Tropical Cyclones/Sub-Monthly Wave Patterns and Intraseasonal Oscillations over the Western North Pacific

Ko¹,

Hsu²

2014

Terr. Atmos. Ocean. Sci.

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“…One of the major characteristics of the EASM is the northward-propagating intraseasonal signal that is often phase-locked with the seasonal cycle (Chen et al 2000). Marked intraseasonal signals were observed in the 1998 summer and found closely corresponding to the occurrence of a double Mei-Yu (Mu and Li 2000;Xu and Zhu 2002;Wang et al 2003;Ding et al 2004).…”

Section: Intraseasonal Signalsmentioning

confidence: 99%

Simulation of the 1998 East Asian Summer Monsoon using the Purdue Regional Model

Hsu

Kau

et al. 2004

Journal of the Meteorological Society of Japan

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This study used the Purdue Regional Model to simulate the 1998 EASM to assess the model performance. The results indicated that the model was capable of simulating the overall characteristics of the 1998 EASM on the seasonal, intraseasonal, onset, and daily time scales. On the seasonal time scale, the model tended to produce more precipitation over the land and less precipitation over the ocean. This land-sea contrast in the model performance was consistent with the stronger-than-observed Pacific anticyclone in the simulation. It appears that the over simulated anticyclone was also found in other models, and is not a unique problem to the PRM. Future studies are needed to tackle this seemingly fundamental problem in several regional models.The model simulated the seasonal march of the EASM well, characterized by northward-propagating rain bands. Intraseasonal oscillation events propagating northward were also well reproduced. These results confirm that the model is capable of producing realistic sub-seasonal variability in the inner domain, once the proper lateral boundary forcing is provided.The model correctly simulated the onset timing and dramatic changes before and after the onset. However, the model incorrectly simulated the circulation and precipitation during the onset, because it failed to simulate the rapid development of a weak trough in the northern South China Sea. After the onset period, the model performance became reliable again. This indicates that the model is capable of fixing the existing large biases, with the proper lateral boundary forcing.This model was able to simulate the gross fluctuation in the regional-averaged daily precipitation, although it missed some extreme events that resulted in flooding in China. The incorrect simulation of these extreme events was partially responsible for the biases in the simulated seasonal precipitation. It is suggested that a regional model should be able to simulate the multi-scale features from the daily to seasonal time scales and their mutual interaction to correctly simulate the monthly and seasonal mean fields.

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“…These dates were chosen based on the major shifts in the large-scale circulation and rainfall over the SCS as discussed previously. Because the onset of the SCS monsoon was progressive, the exact days marking the different phases may vary depending on the choice of parameters and/or geographical locations (e.g., Chen et al 2000 andDing et al 1999). Figure 7 shows the horizontal distributions of time-mean TMI surface rain rates, winds and divergences at 200 and 850 mb based on the SCSMEX wind analysis, for representative pentads within the four phases of the SCS summer monsoon respectively.…”

Section: Intraseasonal Variabilitymentioning

confidence: 99%

“…The sudden onset of the SCS monsoon is signaled by a large-scale wind shift in the lower troposphere from easterly to westerly, and outburst of deep convection over the SCS (Lau et al 1998;Ding et al 1999;Li and Qu 1999). Convective activities in the vicinity of northern SCS and the Philippines have been linked to interannual and intraseasonal rainfall variability over mainland China and Japan, as well as summertime teleconnection signals over the North Pacific (Nitta 1987;Huang and Sun 1992;Lau and Peng 1992;Chen et al 2000;Lau and Weng 2000a, b). Since precursory signals of anomalous monsoons over East Asia and South Asia can often be detected early in the season (Lau and Yang 1997), understanding the physical processes of onset and maintenance of SCS convection is critically important for predicting possible occurrence of droughts and floods in the Asian monsoon land regions.…”

Section: Introductionmentioning

confidence: 99%

Evolution of the Large Scale Circulation, Cloud Structure and Regional Water Cycle Associated with the South China Sea Monsoon during May-June, 1998.

Lau

2002

Journal of the Meteorological Society of Japan

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This paper studies the evolution of the South China Sea (SCS) monsoon during May-June 1998, to elucidate relationships among the large scale circulation, organization of convection, cloud structures, and fluctuations of the regional water cycle of the SCS. Primary data used include field observations from the South China Sea Monsoon Experiment (SCSMEX), and the satellite rain products from the Tropical Rainfall Measuring Mission (TRMM). Prior to the onset of the SCS monsoon, enhanced convective activities associated with the Madden and Julian Oscillation were detected over the equatorial Indian Ocean in early May while the SCS was under the influence of the West Pacific Anticyclone with prevailing low level easterlies and suppressed convection. Subsquently, a bifurcation of the MJO convection near 90 E led to the development of strong convection over the Bay of Bengal, which spawned low-level westerlies across Indo-China and contributed to the initial build-up of moisture and convective available potential energy over the northern SCS. The onset of the SCS monsoon occurred around May 18-20, and appeared to be triggered by the equatorward penetration of extratropical frontal disturbances, originating from the continental regions of East Asia.Analysis of TRMM microwave and precipitation radar data revealed that during the onset phase, convection over the northern SCS consisted of squall-type rain cells embedded in meso-scale complexes similar to extratropical systems. The radar Z-factor intensity indicated that SCS clouds possessed a bimodal distribution, with a pronounced signal (>30 dBz) at a height of 2-3 km, and another one (>25 dBz) at the 8-10 km level, separated by a well-defined melting level signaled by a bright band at around 5-km level. The most convectively active phase of the SCS monsoon, as measured by the abundance of convective and stratiform hydrometeor types, inferred from the radar vertical profile, was found to occur when the large scale vertical wind shear was weakest. The fluctuation of the water cycle over the northern SCS was found to be closely linked to the largescale dynamical and SST forcings. Before onset and during the break, the northern SCS was relatively warm and served as a moisture source (E À P > 0) to the overlying atmosphere. During the active phase, the northern SCS was cooled, providing a strong sink (E À P f 0) for atmospheric moisture, with the primary source of moisture coming from regions further west over Indo-China and the eastern Indian Ocean. Vigorous water recycling by convective systems in the northern SCS occurred during the mature phase of the SCS monsoon, with precipitation efficiency (defined as the ratio of the surface precipitation to the sum of large scale moisture convergence and surface evaporation from the ocean) approaching 96%. Westward transport of moisture from Indo-China into, and northward transport out of, the northern SCS provided the main source of moisture for the torrential rain over the YRV in mid-June 1998. The present results suggest...

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Interaction between the Summer Monsoons in East Asia and the South China Sea: Intraseasonal Monsoon Modes

Cited by 108 publications

References 21 publications

Barotropic Interactions Between Summertime Tropical Cyclones/Sub-Monthly Wave Patterns and Intraseasonal Oscillations over the Western North Pacific

Barotropic Interactions Between Summertime Tropical Cyclones/Sub-Monthly Wave Patterns and Intraseasonal Oscillations over the Western North Pacific

Simulation of the 1998 East Asian Summer Monsoon using the Purdue Regional Model

Evolution of the Large Scale Circulation, Cloud Structure and Regional Water Cycle Associated with the South China Sea Monsoon during May-June, 1998.

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