• Journal of the Korean earth science society
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• v.35 no.3
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• pp.168-179
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• 2014

The purpose of this study focuses on the prediction time and location of turning-point of typhoon tracks using the water vapor images of Communication, Ocean and Meteorological Satellite (COMS) which has a very short observation interval. It targets a more accurate prediction of turning-point of typhoon tracks through the relationship between dry slot and northern/southern oscillations of jet stream. Jet stream moves by the position of jet streak and the ${\upsilon}$-component velocity of geostrophic wind. If the ${\upsilon}$-component of geostrophic wind gets stronger toward south, jet stream develops into a circular jet. In that condition, dry slot in satellite water vapor imagery extends toward south, and typhoon track turns as the distance of curved moisture band (CMB) gets narrowed down. If the interval of CMB is below $15^{\circ}$ of latitude, the typhoon track is turning toward north or northeast within 24 hours. As a result, typhoon track showed that when dry slot position was located less than $32^{\circ}N$, typhoon turned its track at $20-23^{\circ}N$ ($1^{th}$ Kong-Rey 2007 and $17^{th}$ Jelawt at 2012), and when in $35^{\circ}N$ above, it turned at $27^{\circ}N$ ($4^{th}$ Man-yi 2007).

• Atmosphere
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• v.19 no.1
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• pp.37-51
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• 2009

Kinematic characteristics of a heavy rainfall event occurred in Changma front are analyzed using synoptic weather charts, satellite imagery and NCEP(National Centers for Environmental Prediction) / NCAR(National Centers for Atmospheric Research) reanalysis data. The heavy rainfall is accompanied with mesoscale rain clouds developing over the Southwest region of Korea during the period from 0300 LST to 2100 LST 25 June 2006. The surface cyclone in the Changma front is generated and developed rapidly when it meets following vertical conditions: The maximum value of relative vorticity is appeared at 700 hPa and is extended gradually near the surface. It is thought that the vertical structure of relative vorticity is closely related with the descent of strong wind zone exceeding $10ms^{-1}$. The jet core at 200 hPa is shifted southward and extended downward and the low-level jet stream associated with upper-level jet stream appeared at 850 hPa. Kinematic features of heavy rainfall system at cyclone-generating point are as follows: In the generating stage of cyclone, the relative vorticity below 850 hPa increased and the convergence below 850 hPa and the divergence at 400 hPa are intensified by southward movement of jet core at 200 hPa. The heavy rainfall system seems to locate to the south of the exit region of upper-level jet streak; In the developing stage of cyclone, the relative vorticity below 850 hPa and the convergence near surface are further strengthened and upward vertical velocity between 850 hPa and 200 hPa is increased.

• Journal of Environmental Science International
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• v.21 no.12
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• pp.1511-1521
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• 2012

An attempt is made to analyse characteristic features of heavy rainfalls which occur at the metropolitan area of the Korean peninsular the on- and off- Changma season. For this, two representative heavy rainfall episodes are selected; one is the on-Changma season wherein a torrential rain episode happened at Goyang city on 12 July 2006, and the other is the off-Changma season, a heavy rainfall event in Seoul on 21 September 2006. Both recorded considerable amounts of precipitation, over 250mm in a half-day, which greatly exceeded the amount expected by numerical prediction models at those times, and caused great damage to property and life in the affected area. Similarities in the characteristics of both episodes were shown by; the location of upper-level jet streak and divergence fields of the upper wind over heavy rainfall areas, significantly high equivalent potential temperatures in the low atmospheric layer due to the entrainment of hot and humid air by the low-level jet, and the existence of very dry air and cold air pool in the middle layer of the atmosphere at the peak time of the rainfall events. Among them, differences in dynamic features of the low-level jet and the position of rainfall area along the low-level jet are remarkable.

• Journal of Environmental Science International
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• v.11 no.2
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• pp.111-120
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• 2002

Asian dust(or yellow sand) occurs mainly in spring and occasionally in winter in east Asia, when the weather conditions are under an upper trough/cut-off low and surface high/low pressure system during blocking episode days associated with the stationary patterns of the upper level jet stream. The transport mechanism for Asian dust during the blocking episode days in spring 2001 was analyzed using the TOMS aerosol index and meteorological mesoscale model 5(MM5). Based on the E vector, an extension of an Eliassen-Palm flux, the blocking episode days were found to be associated with the development of an upper cut-off low and surface cyclones. Concurrently, the occurrence of dust storms was also determined by strong cold advection at the rear of a jet streak, which exhibited a maximum wind speed within the upper jet stream. As such, the transport mechanism for Asian dust from China was due to advection of the isentropic potential vorticity(IPV) and isentropic surfaces associated with tropopause folding. The transport heights for Asian dust during the blocking episode days were found to be associated with the distribution of the isentropes below the IPV At the same time, lee waves propagated by topography affected the downward motion and blocking of Asian dust in China. The Asian dust transported from the dust source regions was deposited by fallout and rain-out with a reinforcing frontogenesis within a surface cyclone, as determined from satellite images using TOMS and GMS5. Accordingly, these results emphasize the importance of forecasting jet streaks, the IPV, and isentropes with geopotential heights in east Asia.

• Journal of the Korean earth science society
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• v.31 no.4
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• pp.354-369
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• 2010

The synoptic and kinematic characteristics of a heavy rainfall that occurred in Gangneung region on 22 to 24 October 2006 were investigated using weather maps, infrared images, AWS observation data and NCEP global final analyses data. The total amount of rainfall observed in the region for the period was 316.5 mm, and the instanteneous maximum wind speed was $63.7m\;s^{-1}$. According to the analysis of weather maps, before the starting of the heavy rainfall, an extratropical low pressure system was developed in the middle region of the Korean Peninsula, and an inverted trough was formed in the northern region of the peninsula. In addition, a jet stream on the upper charts of 300 hPa was located over the Yellow Sea and the southern boundary of the peninsula. A cutoff low in the cyclonic shear side of the upper jet streak, which was linked to an anomaly of isentropic potential vorticity, was developed over the northwestern part of the peninsula. And there are analyzed potential vorticity and wind, time-height cross section of potential vorticity, vertical air motion, maximums of the divergence and convergence and vertical distribution of potential temperature in Gangneung region. The analyzed results of the synoptic conditions and kinematic processes strongly suggest that the tropopause folding made a significant role of initializing the heavy rainfall.