Ultra-High-Resolution Numerical Weather Prediction with a Large Domain Using the K Computer: A Case Study of the Izu Oshima Heavy Rainfall Event on October 15-16, 2013

Oizumi, Tsutao; Saitō, Kazuo; Ito, Junshi; Kuroda, Thoru; Duc, Le

doi:10.2151/jmsj.2018-006

Cited by 14 publications

(16 citation statements)

References 42 publications

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“…The total precipitation is larger in TOPO1km than in TOPO100m in all three cases, suggesting that the presence of submesoscale topography reduces precipitation. This contrasts with the results of Oizumi et al (2018) and Takemi (2018); when the mechanical effect of topography was dominant, precipitation was enhanced. The difference in total precipitation is mainly due to intense precipitation over 1 mm h 21 .…”

Section: A Statistical Characteristicscontrasting

confidence: 96%

“…A few studies have investigated the influence of submesoscale topography on precipitation with realistic topography. Numerical simulations using a terrain height dataset with subkilometer resolution enhanced the simulated precipitation of a coastal front associated with a typhoon (Oizumi et al 2018) and a stationary linear-shaped convective system under the baiu front 1 (Takemi 2018). Under these circumstances, submesoscale topography is thought to enhance the mechanical effects of largerscale topography on precipitation.…”

Section: Introductionmentioning

confidence: 98%

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Influence of sub-mesoscale topography on daytime precipitation associated with thermally driven local circulations over a mountainous region

Nishizawa

Yamaura

Kajikawa

2021

Journal of the Atmospheric Sciences

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In this study, the effect of sub-mesoscale topography (i.e., topographical features smaller than a few kilometers in size) on precipitation associated with thermally driven local circulations over a mountainous region is examined in the absence of synoptic-scale precipitation systems through a 100-m-mesh large-eddy simulation experiment. The observed effect of topography on precipitation is different to that identified in previous studies; sub-mesoscale topography is observed to induce a weakening effect on precipitation in this study, while previous studies have suggested that sub-mesoscale topography enhances precipitation. This discrepancy between studies is owing to differences in the scale of the topography and the precipitation-inducing system under consideration. Previous studies have focused on precipitation associated with synoptic-scale systems, where mechanical orographic forcing is dominant. The mechanism of the topographic effect where thermal orographic forcing is dominant was clarified in this study. Under thermally driven local circulation, the convergence of upslope flow near large-scale mountain ridges is one of the main causes of precipitation. Sub-mesoscale topographic features promote the detachment of upslope flow from the mountain surface and vertical mixing in the boundary layer. This detachment and mixing result in a weakening of convergence and updraft and reduction of equivalent potential temperature around the ridge that explains the observed weakening effect on precipitation. Cold pools formed by evaporation of rainfall associated with upslope flow enhance the weakening effect. These results confirm the importance of sub-mesoscale topography in orographic precipitation.

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Section: A Statistical Characteristicscontrasting

confidence: 96%

Section: Introductionmentioning

confidence: 98%

Influence of sub-mesoscale topography on daytime precipitation associated with thermally driven local circulations over a mountainous region

Nishizawa

Yamaura

Kajikawa

2021

Journal of the Atmospheric Sciences

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“…For wind representations, Oku et al (2010), Takemi et al (2010), and Takemi (2013) demonstrated that accurate representations of fine topographical features improve the representations of extreme winds in complex terrain. For rainfall, Takemi (2010) and Oizumi et al (2018) showed that the simulation with finer terrains reproduced stronger rains. However, there are few studies that examined how topographical representations affect quantitative simulations of heavy rainfalls.…”

Section: Introductionmentioning

confidence: 99%

Importance of Terrain Representation in Simulating a Stationary Convective System for the July 2017 Northern Kyushu Heavy Rainfall Case

Takemi

2018

SOLA

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An extreme, damaging rainfall occurred in northern Kyushu in July 2017. Whether such an extreme rainfall is quantitatively captured by numerical models is a challenging issue. We investigate the influences of terrain representation in simulating a stationary convective system and the resulting heavy rainfall for this case by conducting a series of 167-m-resolution numerical experiments. By employing a high-resolution elevation dataset as well as a double-moment cloud microphysics scheme, the control experiment successfully reproduced the stationary, linear-shaped convective system and the associated heavy rainfall. When the model terrain was created by a coarser-resolution elevation dataset, the 167-mresolution experiment underestimated the accumulated rainfall, because of discretely developing convection and weaker intensities of the rainfall. These impacts of the terrain representation were confirmed to be robust through conducting another experiments with a different microphysics scheme. The representation of model terrains is critically important in simulating stationary convective systems and quantitatively the resulting heavy rainfall.

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“…They also indicated that a senjo-kousuitai event observed in Fukui Prefecture in 2004 could not be reproduced due to uncertainty in the initial lowlevel wind conditions. Oizumi et al (2018) investigated the dependence of the reproducibility of a senjo-kousuitai event observed across Izu-Oshima Island in 2013 (see Fig. 1a) on the horizontal resolution (5 km, 2 km, 500 m, and 250 m) and planetary boundary schemes.…”

Section: Introductionmentioning

confidence: 99%

Quasi-stationary Band-Shaped Precipitation Systems, Named “Senjo-Kousuitai”, Causing Localized Heavy Rainfall in Japan

Kato

2020

Journal of the Meteorological Society of Japan

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In Japan, localized heavy rainfall events producing accumulated three-hour precipitation amounts larger than 200 mm are often observed to cause severe landslides and floods. Such events are mainly brought by quasi-stationary bandshaped precipitation systems, named "senjo-kousuitai" in Japanese. Senjo-kousuitai is defined as a band-shaped heavy rainfall area with a length of 50-300 km and a width of 20-50 km, produced by successively formed and developed convective cells, lining up to organize multi-cell clusters, and passing or stagnating at almost the same place for a few hours. The formation processes of senjo-kousuitai are categorized mainly into two types; the broken line type in which convective cells simultaneously form on a quasi-stationary local front by the inflow of warm and humid air, and the back building type in which new convective cells successively forming on the upstream side of low-level winds linearly organize with pre-existing cells. In this study, previous studies of band-shaped precipitation systems are reviewed, and the numerical reproducibility of senjo-kousuitai events and the favorable conditions for their occurrence are examined. In a case of Hiroshima heavy rainfall observed in western Japan on 20 August 2014, the reproduction of the senjo-kousuitai requires a horizontal resolution of at least 2 km, which is sufficient to roughly resolve the formation and development processes of convective cells, while a resolution of 250-500 m is necessary to accurately reproduce their inner core structures. The 2km model quantitatively reproduced the Hiroshima case when initial conditions 10 hours before the event were used, but the predicted amounts of maximum accumulated precipitation were considerably reduced as the initial time became closer to the occurrence time of the senjo-kousuitai. This reduction was brought from the 3 excessive inflow of low-level dry air that shifted occurrence areas of new multi-cell clusters. Six favorable occurrence conditions of senjo-kousuitai events for their diagnostic forecasts were statistically constructed from environmental atmospheric fields in previous localized heavy rainfall events. Two conditions of (1) large water vapor flux amounts (> 150 g m-2 s-1) and (2) short distances to the level of free convection (< 1000 m) were chosen representatively for the low-level water vapor field that is judged based on 500-m height data. Four other favorable conditions are selected; (3) high relative humidity at midlevels (> 60% at 500 hPa and 700 hPa), (4) large vertical shear estimated from the storm relative environmental helicity (>100 m 2 s −2), (5) synopticscale ascending areas (400 km mean field at 700 hPa), and (6) the exclusion of warm air advection frequently appearing at 700-850 hPa and inhibiting the development of convection (i.e., an equilibrium level > 3000 m).

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Ultra-High-Resolution Numerical Weather Prediction with a Large Domain Using the K Computer: A Case Study of the Izu Oshima Heavy Rainfall Event on October 15-16, 2013

Cited by 14 publications

References 42 publications

Influence of sub-mesoscale topography on daytime precipitation associated with thermally driven local circulations over a mountainous region

Influence of sub-mesoscale topography on daytime precipitation associated with thermally driven local circulations over a mountainous region

Importance of Terrain Representation in Simulating a Stationary Convective System for the July 2017 Northern Kyushu Heavy Rainfall Case

Quasi-stationary Band-Shaped Precipitation Systems, Named “Senjo-Kousuitai”, Causing Localized Heavy Rainfall in Japan

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