Quasi-Biweekly Mode and Its Modulation on the Diurnal Rainfall in Taiwan Forecasted by the CFS

Wang, Shih-Yu; Chia, Hsin-Hsing; Gillies, Robert R.; Jiang, Xianan

doi:10.1175/waf-d-12-00120.1

Cited by 11 publications

(20 citation statements)

References 42 publications

(31 reference statements)

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“…Among these weather systems, convective afternoon rainfall (hereafter, CAR) is the most frequently observed pattern (Wang and Chen 2008). Because of its importance to local residents, the characteristics and causes of CAR have been examined in many studies (Chen et al 1991;Johnson and Bresch 1991;Kerns et al 2010;Lin et al 2011;Huang and Chan 2012;Wang et al 2013). Studies have noted that CAR generally occurs on a day associated with a stronger sea breeze circulation during the daytime (e.g., Lin et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Summer Convective Afternoon Rainfall Simulation and Projection Using WRF Driven by Global Climate Model. Part I: Over Taiwan

Huang¹,

Chang

Cheng

et al. 2016

Terr. Atmos. Ocean. Sci.

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This paper is the first of a two-part study that investigates summer convective afternoon rainfall (CAR) activity over the East Asian continent through simulation and projection. We focus on the CAR activity over Taiwan in Part I. In Part II, the changes in CAR activity over South China and Luzon are examined. Using the WRF (Weather Research and Forecasting) model driven by two super-high resolution global climate models: HiRAM (High Resolution Atmospheric Model) and MRI (Meteorological Research Institute Atmospheric General Circulation Model), this study evaluates the performance of models (HiRAM, MRI, and WRF) used to simulate the summer CAR activity over Taiwan. The evaluations focus on the spatialtemporal variations in CAR activity during two time periods: the present-day (1979 -2003, historical run) and the future (2075 -2099, RCP8.5 scenario). For the present-day simulations, analyses indicate that both HiRAM and MRI cannot accurately simulate the temporal evolution of diurnal rainfall. This timing shift problem can be fixed after dynamical downscaling using WRF. The WRF dynamical downscaling approach also helps generate a more realistic CAR amount simulation over western Taiwan, where most residents live. In future projections all models predict that a significant decrease in CAR amount will occur over southwest Taiwan. This decrease in CAR amount is suggested due to the decrease in CAR frequency, not a change in the CAR rate. All models suggest that the cause of decrease in CAR frequency over southwest Taiwan is weaker local afternoon surface wind convergence and thermal instability to suppress CAR genesis.

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Section: Introductionmentioning

confidence: 99%

Summer Convective Afternoon Rainfall Simulation and Projection Using WRF Driven by Global Climate Model. Part I: Over Taiwan

Huang¹,

Chang

Cheng

et al. 2016

Terr. Atmos. Ocean. Sci.

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“…Using a local pressure index different from the BSISO2 index, Wang et al . () also demonstrated that DC appears more frequently in Taiwan when the subtropical high east of Taiwan has intensified under the modulation of a higher‐frequency (i.e. 8–25 day) intra‐seasonal oscillation.…”

Section: Resultsmentioning

confidence: 99%

“…However, because the index used by Wang et al . () is different to the two BSISO indices provided by Lee et al . (), it is not possible to clarify the following three scientific questions based on the result of Wang et al .…”

Section: Introductionmentioning

confidence: 97%

“…Using an index derived from local surface‐pressure changes, Wang et al . () have noted that the DC formation in Taiwan can be greatly modulated by atmospheric circulation related to the 10–20 day oscillation. However, because the index used by Wang et al .…”

Section: Introductionmentioning

confidence: 99%

“…(), it is not possible to clarify the following three scientific questions based on the result of Wang et al . (): (1) Which phase of BSISO1 and BSISO2 has the highest chance of DC formation in Taiwan? (2) Is the phase with the highest chance of DC formation also the phase with the strongest mean rainfall intensity of DC days?…”

Section: Introductionmentioning

confidence: 99%

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Impact of boreal summer intra‐seasonal oscillations on warm season diurnal convection activity in Taiwan

Huang

Chang

2017

Intl Journal of Climatology

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Diurnal convection (DC), which is characterized by rainy days with maximum rainfall during the afternoon without strong synoptic disturbances, is the most frequently observed weather system that affects local rainfall in Taiwan. In this study, we investigate the impact of boreal summer intra-seasonal oscillations (BSISOs) on the modulation of warm season (May-September) DC activities in Taiwan. Our analyses focus on (1) identifying the relationships between changes in DC characteristics (e.g. DC days and the mean rainfall intensities on DC days) and the phase evolutions of two types of BSISOs (including the 30-60-day ISO named BSISO1 and the 10-30-day ISO named BSISO2) and (2) the related maintenance mechanisms. Analyses of DC days demonstrate that the contribution of DC days to the total quantity of rainy days in Taiwan generally reaches a maximum value when Taiwan is being modulated by intensified southwesterly winds, intensified local sea breeze circulations, and intensified local thermal instabilities (i.e. phase 3 of BSISO1 and phase 7 of BSISO2). Analyses of the mean rainfall intensities on DC days show that maximum values are generally reached when the moisture convergence line propagates northwards over Taiwan (i.e. phase 1 of BSISO1 and phase 3 of BSISO2). Further examinations indicate that the abovementioned findings are not dependent upon the strengths of the BSISOs.

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Impact of atmospheric changes on the low‐frequency variations of convective afternoon rainfall activity over Taiwan

et al. 2015

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This study examines the characteristics of low-frequency variations (defined as decadal-scale changes) in summer (June-August) convective afternoon rainfall (CAR) activity over Taiwan during . Using 3-hourly rain gauge data, it was found that (1) the CAR frequency exhibits a secular trend and the 10-20 decadal oscillation, (2) the trend in CAR frequency is positive in northern Taiwan but negative in central and southern Taiwan, and (3) the CAR rate increased over most of the lower plains but decreased over the mountain range of Taiwan. Diagnoses using the Japanese ReAnalysis (JRA-55) data and surface observations indicate that the low-frequency variations in CAR frequency are closely associated with the variations in monsoon southwesterly winds over the South China Sea and island-wide sea breeze convergence. The regional low-level circulation changes are linked to sea surface temperature anomalies over the Niño-4 region and its 10-20 year (quasi-decadal) oscillation. Regarding the processes that change the CAR rate in the trending patterns, it was found that increases in the moisture flux convergence and the moist (conditional) instability over the lower plains together explain the stronger CAR events in the long run.

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Quasi-Biweekly Mode and Its Modulation on the Diurnal Rainfall in Taiwan Forecasted by the CFS

Cited by 11 publications

References 42 publications

Summer Convective Afternoon Rainfall Simulation and Projection Using WRF Driven by Global Climate Model. Part I: Over Taiwan

Summer Convective Afternoon Rainfall Simulation and Projection Using WRF Driven by Global Climate Model. Part I: Over Taiwan

Impact of boreal summer intra‐seasonal oscillations on warm season diurnal convection activity in Taiwan

Impact of atmospheric changes on the low‐frequency variations of convective afternoon rainfall activity over Taiwan

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