• 대기
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• 제11권2호
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• pp.6-12
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• 2001

The East Asian monsoon is generally accompanied with the quasi-stationary front along the northern and northwestern periphery of the subtropical anticyclone in the boundary zone of the polar cold air mass and the tropical warm air mass. The rainy season in Korea has been called as Changma since the middle of 1500s. In meteorology, the rainy season with the quasi-stationary front, the Changma front, during the early summer has been defined as the Changma since 1905. The difference of meaning on Changma between meteorologists and the general public sometime does give a confusion. For example, the heavy rainfall event after the retreat of Changma is recognized as Changma by the general public, but not by most of meteorologists. The decision of the onset and retreat dates of Changma among the meteorologists is also ambiguous because of different viewpoints on the definition of Changma. In this study we survey the etymology and definition of Changma.

• 대기
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• 제21권1호
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• pp.109-121
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• 2011

This study revisits the definition of Changma, which is the major rainy season in Korea and corresponds to a regional component of the East Asian summer monsoon system. In spite of several decades of researches on Changma, questions still remain on many aspects of Changma that include its proper definition, determination of its onset and retreat, and relevant large-scale dynamical and thermodynamical features. Therefore, this study clarifies the definition of Changma (which is a starting point for the study of interannual and interdecadal variability) using a basic concept of air mass and front by calculating equivalent potential temperature (${\theta}_e$) that considers air temperature and humidity simultaneously. A negative peak in the meridional gradient of this quantity signifies the approximate location of Changma front. This front has previously been recognized as the boundary between the tropical North Pacific air mass and cold Okhotsk sea air mass. However, this study identifies three more important air masses affecting Changma: the tropical monsoon air mass related to the intertropical convergence zone over Southeast Asia and South China Sea, the tropical continental air mass over North China, and intermittently polar continental air mass. The variations of these five air masses lead to complicated evolution of Changma and modulate intensity, onset and withdrawal dates, and duration of Changma on the interannual time scale. Importantly, use of ${\theta}_e$, 500-hPa geopotential height and 200 hPa zonal wind fields for determining Changma onset and withdrawal dates results in a significant increase (up to~57%) in the hindcast skill compared to a previous study.

• 한국제4기학회지
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• 제19권1호
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• pp.18-26
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• 2005

The East Asian summermonsoon is generally accompanied with the quasi-stationary front along the northern and northwestern periphery of the subtropical Northwest Pacific high. The rainy season in Korea has been called as Changma since the middle of 1500s. Understanding of Changma and heavy rainfall advancing along the Changma front is one of main interesting of Korean meteorologists. This study briefly summarized the descriptive characteristics of Changma and its relatedmechanism, definitions on the Changma period, and etymology of Changma through reviewing the previous studies on Changma.

• 한국지역지리학회지
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• 제9권2호
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• pp.192-202
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• 2003

본 연구는 한반도 전역에 걸쳐 장마전선의 위치에 따라 강수량의 분포특성을 살피고 이 강수량이 6, 7월 평균강 수량에 대한 기여율을 조사한 것이다. 그 결과 장마전선이 북위 30도 이북에 있는 경우 한반도 전체에서 전선과 가까운 지역에서 많은 강수량이 나타났으며 이들은 다우지역과 대체로 일치한다. 전선이 북위 30도 이남에 있는 경우와 비교하여 30${\sim}$33도로 북상할 때 전국적으로 강수량이 증가하여 이 시기에 장마가 시작됨을 알 수 있었다. 장마철에 개마고원 일대에서는 미우의 출현비율이 매우 높았다. 이중에는 장마전선과 무관한 강수도 상당수 있을 것으로 판단된다. 청천강 유역에서는 6, 7월 평균강수량에 대한 기여율이 큰 경우가 전선이 없을 때, 전선이 청천강 유역에서 먼 북위 30${\sim}$33도에 있는 때로서 한반도의 타 다우지역과는 다른 특성을 보인다.

• 통합자연과학논문집
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• 제4권1호
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• pp.44-57
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• 2011

In general, heavy rainfall in Korea is mostly associated with inflow of 850hPa low-level jet. It transports abundant heat and moisture flux to the Changma front. In this study, synoptic characteristics of heavy rainfall in Korea from a case study is examined by classifying heavy rainfall cases with synoptic patterns, in particular distribution of upper- and low-level jets, western North Pacific high, and moisture flux. The surface and upper-level weather charts including auxiliary analysis chart and radar and satellite images obtained from the Korea Meteorological Administration, and 500hPa geopotential heights from NCEP/NCAR are used and then KLAPS is applied to understand the local atmospheric structure associated with heavy rainfall. Results show that maximum frequency in 60 heavy rainfall cases with more than 150mm/day appears in the Changma type of 43 cases (a proportion in relation to a whole is 52%) including the combined Changma types with typhoon and cyclone. As indicated in previous studies, most heavy rainfall cases are related to inflow of low-level jet. In addition, synoptic characteristics based on the analyses of weather charts, radar and satellite images, and KLAPS in heavy rainfall case of 12 July, 2009 reveal that the atmospheric vertical structure in particular equivalent potential temperature favorable for effective inflow of warm and moist southwesterly into the Changma front is linked to large potential instability and the strong convergence accompanied with low-level jet around Suwon contributes to atmospheric upsliding along the Changma front, producing heavy rainfall.

• 대기
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• 제27권3호
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• pp.277-290
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• 2017

Characteristics of precipitation in South Korea during the 2016 Changma period (6/18~7/30) are analyzed in great details. El $Ni{\tilde{n}}o$-induced tropical Indian Ocean (IO) basin-wide warming lasts from spring to early summer and induces the western North Pacific subtropical high (WNPSH) circulation anomaly through an equatorial Kelvin wave during the 2016 Changma period. Along the northern edge of the WNPSH, strong precipitation occurred, in particular, over eastern China and southern Japan. During the Changma period, South Korea had the near-normal mean precipitation amount (~332 mm). However, about 226 mm of rain fell in South Korea during 1 July to 6 July, which amounts to 67% of total Changma precipitation in that year. Upper-level synoptic migratory lows and low-level moisture transport played an essential role, especially from 1 July to 3 July, in triggering an abrupt development of fronts over the Korean Peninsula and the eastern continent China. The front over the eastern China migrates progressively eastward, which results in heavy rainfall over the Korean peninsula from 1 to 3 July. In contrast, from 4 to 6 July, the typhoon (NEPARTAK) affected an abrupt northward advance of the North Pacific subtropical high (NPSH). The northward extension of the NPSH strengthens the Changma front and induces the southerly flows toward the Korean peninsula, giving rise to an increase in heavy rainfall. The NEPARTAK is generated due to interaction of the Madden-Julian Oscillation (MJO), equatorial Rossby wave and Kelvin waves.

• 대기
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• 제24권4호
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• pp.533-540
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• 2014

Statistical forecast models for the prediction of the summertime Changma precipitation have been developed in this study. As effective predictors for the Changma precipitation, the springtime sea surface temperature (SST) anomalies over the North Atlantic (NA1), the North Pacific (NPC) and the tropical Pacific Ocean (CNINO) has been suggested in Lee and Seo (2013). To further improve the performance of the statistical prediction scheme, we select other potential predictors and construct 2 additional statistical models. The selected predictors are the Northern Indian Ocean (NIO) and the Bering Sea (BS) SST anomalies, and the spring Eurasian snow cover anomaly (EUSC). Then, using the total three statistical prediction models, a simple ensemble-mean prediction is performed. The resulting correlation skill score reaches as high as ~0.90 for the last 21 years, which is ~16% increase in the skill compared to the prediction model by Lee and Seo (2013). The EUSC and BS predictors are related to a strengthening of the Okhotsk high, leading to an enhancement of the Changma front. The NIO predictor induces the cyclonic anomalies to the southwest of the Korean peninsula and southeasterly flows toward the peninsula, giving rise to an increase in the Changma precipitation.

• 한국지구과학회지
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• 제33권5호
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• pp.377-394
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• 2012

To elucidate the mechanism associated with the development of heavy precipitation system, a field experiment was carried out in Jejudo (or Jeju Island) and Marado, Korea from 22 June to 12 July 2006. The synoptic atmospheric conditions were analyzed using the National Centers for Environmental Prediction-National Center for Atmospheric Research's (NCEP/NCAR) reanalyzed data, weather maps, and sounding data. The kinematic characteristics of each precipitation system were investigated by dual Doppler radar analysis. During the field experiment, data of four precipitation events with more than 20 mm rainfall were collected. In F case (frontal precipitation), a typical Changma front was dominant and the observation field was fully saturated. However there was no convective instability near the surface. LF case (low pressure accompanied with Changma front) showed strong convective instability near the surface, while a strong convergence corresponded to the low pressure from China accompanied with Changma front. In FT case (Changma front indirectly influenced by typhoon), the presence of a convective instability indicated the transport of near surface, strong additional moisture from the typhoon 'EWINIAR'. The convergence wind field was ground to be located at a low level. The convective instability was not significant in T case (precipitation of the typhoon 'EWINIAR'), since the typhoon passed through Jejudo and the Changma front was disappeared toward the northeastern region of the Korean peninsula. The kinematic (convergence and divergence) characteristics of wind fields, convective instability, and additional moisture inflow played important roles in the formation and development of heavy precipitation.

• 대한지리학회지
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• 제45권6호
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• pp.748-765
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• 2010

본 연구에서는 장마철 우리나라의 지역 평균 강수량을 이용하여 강수의 지속성에 따른 종관 특성의 차이를 살펴보았다. 그 결과 일강수량 10mm 이상이 4일 이상 지속되는 강수(장기 강수)와 1~2일에 그치는 강수(단기 강수) 사이에는 종관 특성에 차이가 있음을 알았다. 장기 강수의 경우 우리나라 동쪽에 기압능이 발달, 저기압과 전선의 정체를 유도하였고, 또 강수 1일 전에 찬 공기가 화중지방으로 남하, 전선이 활발해져 강수의 지속성에 기여하였다. 단기 강수의 경우 저기압이 우리나라를 정체 없이 통과하였다. 또한 장기 강수와 단기 강수의 경우에 우리나라 부근의 전선이 대류권 전체에 미치는 경압성이 큰 구조를 보였다. 장기 강수의 전선 구조가 일본 남서부 지역 장기 강수의 경우와 다르며, 단기 강수의 경우는 양 지역에서 같다. 이는 장마가 반드시 일본 바이우(Baiu)의 연장선상에 있는 것은 아님을 의미한다.

• 대기
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• 제19권1호
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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.