Diurnal Circulations and Rainfall in Taiwan during SoWMEX/TiMREX (2008)

Ruppert, James H.; Johnson, Richard H.; Rowe, Angela K.

doi:10.1175/mwr-d-12-00301.1

Cited by 45 publications

(59 citation statements)

References 61 publications

(114 reference statements)

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“…Similar analysis approaches to those described above have been successfully applied in many previous tropical and monsoon field campaigns [e.g., the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (COARE), the South China Sea Monsoon Experiment, the North American Monsoon Experiment, and the Terrain-influenced Monsoon Rainfall Experiment], which have confirmed the reliability of results via comparison with independent observations (Lin and Johnson 1996a,b;Johnson and Ciesielski 2002;Ciesielski et al 2003;Johnson et al 2010;Ruppert et al 2013). Detailed comparisons between the DYNAMO gridded sounding analysis and independent datasets are provided by Johnson et al (2015) and are not repeated here.…”

Section: A Gridded Sounding Analysissupporting

confidence: 63%

Diurnally Modulated Cumulus Moistening in the Preonset Stage of the Madden–Julian Oscillation during DYNAMO*

Ruppert

Johnson

2015

Journal of the Atmospheric Sciences

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120

151

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Atmospheric soundings, radar, and air-sea flux measurements collected during Dynamics of the Madden-Julian Oscillation (DYNAMO) are employed to study MJO convective onset (i.e., the transition from shallow to deep convection) in the tropical Indian Ocean. The findings indicate that moistening of the low-midtroposphere during the preonset stage of the MJO is achieved by simultaneous changes in the convective cloud population and large-scale circulation. Namely, cumuliform clouds deepen and grow in areal coverage as the drying by large-scale subsidence and horizontal (westerly) advection wane. The reduction of large-scale subsidence is tied to the reduction of column radiative cooling during the preonset stage, which ultimately links back to the evolving cloud population. While net column moistening in the preonset stage is tied to large-scale circulation changes, a new finding of this study is the high degree to which the locally driven diurnal cycle invigorates convective clouds and cumulus moistening each day. This diurnal cycle is manifest in a daytime growth of cumulus clouds (in both depth and areal coverage) in response to oceanic diurnal warm layers, which drive a daytime increase of the air-sea fluxes of heat and moisture. This diurnally modulated convective cloud field exhibits prominent mesoscale organization in the form of open cells and horizontal convective rolls. It is hypothesized that the diurnal cycle and mesoscale cloud organization characteristic of the preonset stage of the MJO represent two manners in which local processes promote more vigorous daily-mean column moistening than would otherwise occur.

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Section: A Gridded Sounding Analysissupporting

confidence: 63%

Diurnally Modulated Cumulus Moistening in the Preonset Stage of the Madden–Julian Oscillation during DYNAMO*

Ruppert

Johnson

2015

Journal of the Atmospheric Sciences

Self Cite

120

151

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“…15a), and this is also true over SEC although the differences are less obvious. 16a), in agreement with Li and Chen (1998), Yeh and Chen (2002), Wang et al (2005b), and Ruppert et al (2013). 15b), likely linked to a reduced blocking effect (e.g., Yeh and Chen 2002;Wang et al 2005b).…”

Section: The Diurnal Experiments With and Without Terrainsupporting

confidence: 62%

“…2). The local enhancement of convection offshore from southwestern Taiwan in CTL, most likely due to terrain blocking (e.g., Wang et al 2005b;Ruppert et al 2013), is reduced in SNP even though a substantial amount of rainfall is still received over southwestern Taiwan from episode 1. The daily rainfall distributions over Taiwan during 13-16 June in SNP (Figs.…”

Section: B the Synoptic Experimentsmentioning

confidence: 99%

A Study of Two Propagating Heavy-Rainfall Episodes near Taiwan during SoWMEX/TiMREX IOP-8 in June 2008. Part II: Sensitivity Tests on the Roles of Synoptic Conditions and Topographic Effects

Wang

Hsu

Chen

et al. 2014

Monthly Weather Review

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This study is the second of a two-part series to investigate two rainfall episodes in the Hovmöller space near Taiwan during the eighth intensive observing period (IOP-8, 12-17 June 2008) of the Southwest Monsoon Experiment/Terrain-influenced Monsoon Rainfall Experiment (SoWMEX/TiMREX). The first episode moved eastward and the second westward, and both caused heavy rainfall in Taiwan. The goal of Part I was to better understand the mechanism and controlling factors for the organization and propagation of the episodes. Here in Part II, the detailed roles played by synoptic conditions and terrain effects are further examined. Three sensitivity tests (at 2.5-km grid spacing) are designed to include only the effects of synoptic evolution (SNP), and those from land-sea distribution-diurnal variations on top of a mean background with/ without topography (DIU/DNT). As the benchmark, the control (CTL) experiment captures the 6-day event successfully and is validated in Part I.In SNP, the two episodes are reproduced with overall similarity to CTL and the observation, and this confirms that the general location/time of rainfall are mainly controlled by synoptic forcing in this case, in contrast to typical warm-season conditions in the central United States. Even so, diurnal effects can still exert discernible impacts and modulate local convective development in many instances, particularly an afternoon enhancement over terrain, and the averaged diurnal cycle in CTL over southeastern China resembles those in DIU/DNT rather than that in SNP (with no land). The steep topography of Taiwan is especially important for its rainfall distribution, including the heavy rainfall on 16 June through processes as postulated by Xu et al.

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“…3 shows that the distribution of CAR amount is characterized by a clear eastwest contrast, with larger (smaller) values in the west (east) side of the mountain range. The formation of this asymmetric distribution might be attributed to the fact that the southwesterly monsoon wind generally brings more moist and unstable air for CAR formation over western Taiwan (i.e., windward side) (e.g., Ruppert et al 2013;Huang and Wang 2014). Different from the observation, the HiRAM's simulated CAR amount distribution generally follows the terrain structure (i.e., larger values centered at the high mountains and smaller values at the low-plains).…”

Section: Present-day Simulationsmentioning

confidence: 76%

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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Diurnal Circulations and Rainfall in Taiwan during SoWMEX/TiMREX (2008)

Cited by 45 publications

References 61 publications

Diurnally Modulated Cumulus Moistening in the Preonset Stage of the Madden–Julian Oscillation during DYNAMO*

Diurnally Modulated Cumulus Moistening in the Preonset Stage of the Madden–Julian Oscillation during DYNAMO*

A Study of Two Propagating Heavy-Rainfall Episodes near Taiwan during SoWMEX/TiMREX IOP-8 in June 2008. Part II: Sensitivity Tests on the Roles of Synoptic Conditions and Topographic Effects

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

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