• Journal of Environmental Science International
• /
• v.22 no.3
• /
• pp.319-329
• /
• 2013

In this study, the cause of rapid intensity change of typhoon Nakri(0208) in view of point of a trough-typhoon interaction using diagnostic methods was examined based on 6-hourly GDAPS data from 10 to 13 July, 2002. At 0000 UTC 13 July, high PV(Potential Vorticity) region moved southeastward, reaching to the western edge of the Korean peninsula and near typhoon center at surface and there shows an increasing value of EFC(Eddy Momentum Flux Convergence). Also, as the trough and typhoon approach one another at the same time, the vertical shear(850-200 hPa) increases to more than 15 m/s. Thus, it might be concluded that the trough-typhoon interaction made intensified significantly, providing the fact that typhoon Nakri(0208) underwent substantial weakening while moving northward to around Jeju island.

• Journal of Environmental Science International
• /
• v.16 no.9
• /
• pp.1051-1061
• /
• 2007

The impact of midlatitude synoptic system (upper-level trough) on typhoon intensity change was investigated by analyzing the spatial and temporal characteristics of vertical wind shear (VWS), relative eddy momentum flux convergence (REFC), and potential vorticity (PV). These variables were computed over the radial mean $300{\sim}1,000km$ from the typhoon center by using GDAPS (Global Data Assimilation and Prediction System) data provided by the Korea Meteorological Administration (KMA). The selected cases in this study are typhoons Rusa (0215) and Maemi (0314), causing much damage in life and property in Korea. Results show that the threshold value of VWS indicating typhoon intensity change (typhoon to severe tropical storm) is approximately 15 m/s and of REFC ranges 6 to 6.5 $ms^{-1}day^{-1}$ in both cases, respectively. During the period with the intensity of typhoon class, PVs with 3 to 3.5 PVU are present in 360K surface-PV field in the cases. In addition, there is a time-lag of 24 hours between central pressure of typhoon and minimum value of VWS, meaning that the midlatitude upper-level trough interacts with the edge of typhoon with a horizontal distance less than 2,000 km between trough and typhoon. That is, strong midlatitude upper-level divergence above the edge of the typhoon provides a good condition for strengthening the vertical circulation associated with the typhoons. In particular, when the distance between typhoon and midlatitude upper-level trough is less than 1,000 km, the typhoons tend to weaken to STS (Severe Tropical Storm). It might be mentioned that midlatitude synoptic system affects the intensity change of typhoons Rusa (0215) and Maemi (0314) while they moves northward. Thus, these variables are useful for diagnosing the intensity change of typhoon approaching to the Korean peninsula.

• Atmosphere
• /
• v.23 no.1
• /
• pp.23-32
• /
• 2013

Ensemble sensitivity has been recently proposed as a method to analyze the dynamics of severe weather events. We adopt it to investigate the physical mechanism which caused the heavy rainfall over the Korean Peninsula on 6th August 2003. Two rainfall peaks existed in this severe weather event. The selected response functions are 1 hour accumulated rainfall amount of each rainfall peak. Sensitivity fields were calculated using 36 ensemble members which were generated by WRFDA. The sensitive regions for the first rainfall peak are located over the Shandong Peninsula and the Yellow Sea at 12 hours before the first rainfall peak. However, the 12-h forecast sensitivity for the second rainfall peak is revealed near Typhoon ETAU (0310) and midlatitude trough. These results show that the first rainfall peak was induced by low pressure which located over the northern part of the Korean Peninsula while the second rainfall peak was caused by the interaction between typhoon ETAU and midlatitude trough.

• Journal of the Korean earth science society
• /
• v.34 no.4
• /
• pp.303-312
• /
• 2013

Typhoon Sanba was selected for describing the Korea Meteorological Administration (KMA) Global Data Assimilation Prediction System (GDAPS) model bias tendency in forecast for the interaction between mid-latitude trough and movement speed of typhoon. We used the KMA GDAPS analyses and forecasts initiated 00 UTC 15 September 2012 from the historical typhoon record using Typhoon Analysis and Prediction System (TAPS) and Combined Meteorological Information System-3 (COMIS-3). Sea level pressure fields illustrated a development of the low level mid-latitude cyclogenesis in relation to Jet Maximum at 500 hPa. The study found that after Sanba entered the mid-latitude domain, its movement speed was forecast to be accelerated. Typically, Snaba interacted with mid-latitude westerlies at the front of mid-latitude trough. This event occurred when the Sanba was nearing recurvature at 00 and 06 UTC 17 September. The KMA GDAPS sea level pressure forecasts provided the low level mid-latitude cyclone that was weaker than what it actually analyzed in field. As a result, the mid-latitude circulations affecting on Sanba's movement speed was slower than what the KMA GDAPS actually analyzed in field. It was found that these circulations occurred due to the weak mid-tropospheric jet maximum at the 500 hPa. In conclusion, the KMA GDAPS forecast tends to slow a bias of slow movement speed when Sanba interacted with the mid-latitude trough.