Numerical Experiments on the Layered Structures in the Mid-Troposphere over the Equatorial Pacific

Otsuka, Shigenori; Yoden, Shigeo

doi:10.2151/sola.2005-019

Cited by 2 publications

(6 citation statements)

References 6 publications

(7 reference statements)

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“…3c. Thin moist layers are often observed around the levels of the bimodal distribution of relative humidity when a synoptic flow field satisfies preferable conditions for forming thin layers, such as the vertical shear of horizontal winds (Otsuka and Yoden 2005). The multilayered structure of the meridional circulation is stronger in boreal summer, when the convective activity in the ITCZ is stronger.…”

Section: Discussionmentioning

confidence: 99%

“…The stable layers near the 08C level may also produce synoptic-scale vertical shear of horizontal winds through the enhancement of divergence at that level. A layer formation process shown in Otsuka and Yoden (2005) can be an example of such a dynamical process.…”

Section: Discussionmentioning

confidence: 99%

“…We use the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (NCAR) mesoscale model (MM5), version 3.6.2 (Grell et al 1995), and set up two computational domains with two-way nesting, which are the same as those used in Otsuka and Yoden (2005, their Fig. 1).…”

Section: A Model Descriptionmentioning

confidence: 99%

“…We use the data in the inner domain for analysis. The following configuration of the model is also the same as that used in Otsuka and Yoden (2005), and it is able to reproduce the observed thin moist layer reported by Shiotani et al (2002). The model has 62 levels from the surface to 10 hPa with nonuniform vertical grid intervals, which are about 300 m in the midtroposphere.…”

Section: A Model Descriptionmentioning

confidence: 99%

“…They found wet and ozone-poor layers with a typical vertical scale of 1 km in the midtroposphere. Otsuka and Yoden (2005) performed a numerical experiment on the thin moist layers reported by Shiotani et al (2002) and showed that such a layered structure was produced by the vertical shear of a horizontal wind component associated with two synopticscale vortices.…”

Section: Introductionmentioning

confidence: 99%

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Temporal–Spatial Distribution of Thin Moist Layers in the Midtroposphere over the Tropical Eastern Pacific

Otsuka

Yoden

2009

Journal of Climate

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The temporal-spatial distribution of thin moist layers in the midtroposphere over the tropical eastern Pacific is studied by data analyses of radiosonde soundings and downscaling numerical experiments with a regional model. Radiosonde soundings at San Cristó bal, Galá pagos, show frequent existence of thin moist layers between 2 and 10 km in altitude, with a local minimum at 7-8 km. The downscaling experiments with global objective analyses are completed for 2005-06, September and December of 1999-2004, and March of 2000-04. The vertical distribution of thin moist layers has three local maxima at 5, 10, and 16 km, where bimodality of the frequency distribution of water vapor is evident. Between 4 and 7 km, an annual variation is dominant in the occurrence ratio of thin moist layers, which tend to appear in nonconvective regions. In boreal winter, the layers appear to the north of the intertropical convergence zone (ITCZ), whereas in boreal summer the layers appear in the equator-side of the ITCZ. Interannual variations of the appearance of thin moist layers are also studied in 1999-2006, based on the experiments for particular months (March, September, and December). The occurrence ratio is generally high in December and March and low in September. In La Niñ a years, the annual variation is smaller than that in El Niñ o years; the occurrence ratio is higher in boreal summer to the south of the ITCZ.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: A Model Descriptionmentioning

confidence: 99%

Section: A Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temporal–Spatial Distribution of Thin Moist Layers in the Midtroposphere over the Tropical Eastern Pacific

Otsuka

Yoden

2009

Journal of Climate

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A Time-Lagged Ensemble Simulation on the Modulation of Precipitation over West Java in January–February 2007

2012

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A numerical experiment using a regional nonhydrostatic model is performed to investigate the synoptic condition related to the heavy precipitation event that occurred at Jakarta in West Java, Indonesia, in January-February 2007. A time-lagged ensemble forecast method is employed with nine ensemble members. The ensemble mean well reproduces the temporal modulation of the spatial distributions of precipitation obtained from the Tropical Rainfall Measuring Mission data.During the simulated two months, several monsoon surges are observed, but only the surge event during which the Jakarta flood event occurred is associated with a cold anomaly. The top of the cold northerly is about 1.5 km. The cold surge event is preceded by the so-called Borneo vortex event, which is dominated by a cyclonic vortex around Borneo, Indonesia, with a horizontal scale of 1000 km and a vertical scale of 3 km.An analysis of cumulative distribution functions in a pentad time scale shows the modulation of the probability of rainfall rate. In pentad 7 (31 January-4 February), which includes the heavy rainfall event, the fraction of the area with precipitation is the highest and the contribution of heavy rainfall to the total amount is one of the highest in the two-month period. The diurnal cycle of occurrence of heavy rainfall is also modulated; in pentad 7, semidiurnal variation becomes dominant, and the largest peak appears in the early morning.

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Numerical Experiments on the Layered Structures in the Mid-Troposphere over the Equatorial Pacific

Cited by 2 publications

References 6 publications

Temporal–Spatial Distribution of Thin Moist Layers in the Midtroposphere over the Tropical Eastern Pacific

Temporal–Spatial Distribution of Thin Moist Layers in the Midtroposphere over the Tropical Eastern Pacific

A Time-Lagged Ensemble Simulation on the Modulation of Precipitation over West Java in January–February 2007

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