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최우갑,김영아 한국기상학회 2022 대기 Vol.32 No.4
We examined potential seasonal prediction of the Korean surface temperature usingthe relationships between the Arctic Sea Ice Area (SIA) in autumn and the temperature in thefollowing July and February at 850 hPa in East Asia (EA). The Surface Air Temperature (SAT)over Korea shows a similar relationship to that for EA. Since 2007, reduction of autumn SIAhas been followed by warming in Korea in July. The regional distribution shows strong correlationsin the southern and eastern coastal areas of Korea. The correlations in the sea surfacetemperature shows the maximum values in July around the Korean Peninsula, consistent withthe coastal regions in which the maximum correlations in the Korean SAT are seen. InFebruary, the response of the SAT to the SIA is the opposite of that for the July temperature. The autumn sea ice reduction is followed by cooling over Korea in February, although the magnitudeis small. Cooling in the Korean Peninsula in February may be related to planetarywave-like features. Examining the autumn Arctic sea ice variation would be helpful for seasonalprediction of the Korean surface temperature, mostly in July and somewhat in February. Particularly in July, the regression line would be useful as supplementary information for seasonaltemperature prediction.
Variations of the Polar Temperature in the Lower Stratosphere during 1955-2004
최우갑,김동준 한국기상학회 2008 大氣 Vol.18 No.4
The lower-stratospheric polar temperature in winter and spring for both hemispheres is investigated based on the NCEP/NCAR 50-year reanalysis data with respect to the strength of the stratospheric eddy heat flux. Both the polar temperature and the eddy heat flux show significant variation on the decadal and year-to-year time scales except during the Southern Hemisphere winter. The year-to-year variation in the polar temperature is mainly determined by the eddy heat flux convergence. The eddy heat flux convergence is compared with the diabatic heating rate obtained from a two-dimensional model. Radiative heating caused by absorption of solar radiation is comparable to the heating caused by the eddy heat flux convergence in the Southern Hemisphere. The effect of ozone depletion on diabatic heating has been found to be secondary in the Northern Hemisphere, even in March 1997 when the record depletion of ozone took place.
최우갑,육심찬 한국기상학회 2022 Asia-Pacific Journal of Atmospheric Sciences Vol.58 No.2
We investigated the relationship between the Arctic sea ice area and the following year’s atmospheric temperature using reanalysis data. The results demonstrate that the July air temperature at 850 hPa, observed over East Asia (EA) and Western North Pacific (WNP), shows a strong correspondence to the Arctic sea-ice area during the previous year’s September–November period. This relation has been observed since 2007. A strong relationship between the air temperature and the Arctic sea ice is observed only when the sea ice area in autumn is smaller than approximately 6.3million km2. This threshold value coincides with the record reduction in the Arctic sea ice in the autumn of 2007. Sea surface temperature over the Northern Pacific also shows a similar correlation with the Arctic sea ice. The study of these correlations may provide a potential technique for seasonal prediction of July air temperature over EA and the WNP regions.
ILAS와 ILAS-Ⅱ 자료에서 나타난 남극 와동 붕괴기간의 미량기체 분포변화
최우갑(Wookap Choi),임경수(Kyungsoo Lim) 한국기상학회 2010 대기 Vol.20 No.3
Variation of tracer distribution during the vortex-breakup period in the Antarctic region was observed by the data from the Improved Limb Atmospheric Spectrometer (ILAS) and ILAS-Ⅱ. All four trace species including methane, nitrous oxide, ozone, and water vapor show similar patterns of vertical gradient in spite of different structures of zonal mean mixing ratio. Timings of vortex breakup on each level are estimated by two different methods, and they are compared with zonal standard deviations following the latitude circle of each trace species. Although the tracers have different chemical life times and sink/source, the zonal standard deviation patterns show remarkable similarities. The zonal standard deviation shown here to measure the zonal asymmetry of tracer distribution is believed to diagnose the timing of the Antarctic polar-vortex breakup reasonably well.
최우갑(Woo kap Choi),김혜실(Hyesil Kim) 한국기상학회 2010 대기 Vol.20 No.3
The tropopause pressure in the Arctic region is calculated by the conventional thermal and dynamical methods using 30-year reanalysis data. The tropopause pressures determined thermally and dynamically both show semiannual cycles with one peak in April and May, and another in October, contrary to the tropopause temperatures. Although tropopause levels are higher both in January and July, the level of the tropopause in January seems to be associated with the stratospheric temperatures while that of July seems to be associated with the tropospheric temperatures. During the 30-year period the most significant trend appears in April, and it is shown that the altitude of the Arctic tropopause has been rising. Although a potential reason for this trend is stratospheric cooling due to ozone depletion, significant tropospheric warming in April is considered to be another reason.
최우갑(Wookap Choi),정지연(Jiyeon Jung),전종갑(Jong-Ghap Jhun) 한국기상학회 2013 대기 Vol.23 No.4
East Asia experienced extremely cold weather in January 2011, while the previous December and the following February had normal winter temperature. In this study National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data are used to investigate the characteristic features observed in the meteorological fields such as temperature, sea-level pressure, geopotential height, and wind during this winter period. In January the planetary-wave pattern is dominated by stationary-wave form in the mid-to-high latitude region, while transient waves are significant in the previous month. To understand the planetary-wave features quantitatively, harmonic analyses have been done for the 500-hPa geopotential height field. In the climatological-mean geopotential heights the wave numbers 1, 2, and 3 are dominant during the whole winter. In January 2011 the waves of number 1, 2, and 3 are dominant and stationary as in the climatological-mean field. In December 2010 and February 2011, however, the waves of number 4, 5, and 6 play a major role and show a transient pattern. In addition to the distinctive features in each month the planetarywave patterns dependent on the latitude are also discussed.