• 대기
• /
• 제18권3호
• /
• pp.159-169
• /
• 2008

The characteristics of the typhoon's extratropical transition (ET) over the western North Pacific area were investigated using the cyclone phase space (CPS) diagram method suggested by Hart (2003). The data used in this study were the global data assimilation prediction system (GDAPS) and NCEP data set. The number of typhoons selected were 75 cases during 2002 to 2007, and the three parameters were analyzed : the motion relative thickness asymmetry of the storm (B), the upper thermal wind shear and the lower thermal wind shear. Comparing the best-track data provided by the Regional Specialized Meteorological Center /Tokyo, the time of the ET based on CPS was 2~6 hours earlier than the best-track data. And it was shown that the 400- km and 30 kt wind radius of storm for the CPS method were better agreement than the previous suggested radius 500- km.

• 한국지구과학회지
• /
• 제38권5호
• /
• pp.345-356
• /
• 2017

It is important to understand the variability of tropospheric ozone since it is both a major pollutant affecting human health and a greenhouse gas influencing global climate. We analyze the characteristics of East Asia tropospheric ozone simulated in a chemistry-climate model. We use a global chemical transport model, driven by the prescribed meteorological fields from an air-sea coupled climate model simulation. Compared with observed data, the ozone simulation shows differences in distribution and concentration levels; in the vicinity of the Korean Peninsula, a large error occurred in summer. Our analysis reveals that this bias is mainly due to the difference in atmospheric circulation, as the anomalous southerly winds lead to the decrease in tropospheric ozone in this region. In addition, observational data have shown that the western North Pacific subtropical high (WNPSH) reduces tropospheric ozone across the southern China/Korean Peninsula/Japan region. In the model, the ozone changes associated with WNPSH are shifted westward relative to the observations. Our findings suggest that the variations in WNPSH should be considered in predicting tropospheric ozone concentrations.

• Asian Pacific Journal of Cancer Prevention
• /
• 제14권9호
• /
• pp.5085-5088
• /
• 2013

Background: The north-western region of China has a high incidence of oesophageal cancer. This study aimed to investigate whether the intake of food and beverage at high temperature is associated with the risk of oesophageal cancer among adults residing in this remote part of China. Materials and Methods: A case-control study was undertaken in Urumqi and Shihezi, Xinjiang Uyghur Autonomous Region of China, between 2008 and 2009. Participants were 359 incident oesophageal cancer patients and 380 hospital-based controls. Information on temperature of food and beverage intake was obtained by face-to-face interview. Logistic regression analyses were performed to ascertain the association between intake temperature and the risk of oesophageal cancer. Results: The oesophageal cancer patients consumed foods and beverages at higher temperatures than controls, p<0.001. High temperature of tea, water and food intake appeared to increase the risk of oesophageal cancer by more than two-fold, with adjusted odds ratio (95% confidence intervals) of 2.86 (1.73-4.72), 2.82 (1.78-4.47) and 2.26 (1.49-3.45), respectively. Conclusions: Intake of food and beverage at high temperature was positively associated with the incidence of oesophageal cancer in north-western China.

• Ocean and Polar Research
• /
• 제43권1호
• /
• pp.1-14
• /
• 2021

In this study, extreme wind speeds in the Western North Pacific (WNP) were estimated using reanalysis wind fields synthesized with an empirical typhoon vortex model. Reanalysis wind data used is the Fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) data, which was deemed to be the most suitable for extreme value analysis in this study. The empirical typhoon vortex model used has the advantage of being able to realistically reproduce the asymmetric winds of a typhoon by using the gale/storm-forced wind radii information in the 4 quadrants of a typhoon. Using a total of 39 years of the synthesized reanalysis wind fields in the WNP, extreme value analysis is applied to the General Pareto Distribution (GPD) model based on the Peak-Over-Threshold (POT) method, which can be used effectively in case of insufficient data. The results showed that the extreme analysis using the synthesized wind data significantly improved the tendency to underestimate the extreme wind speeds compared to using only reanalysis wind data. Considering the difficulty of obtaining long-term observational wind data at sea, the result of the synthesized wind field and extreme value analysis developed in this study can be used as basic data for the design of offshore structures.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2023년도 학술발표회
• /
• pp.87-87
• /
• 2023

The impact of climate change on typhoons is a major concern in East Asia, especially due to the destructive effects of heavy rainfall on society and the economy, as many megacities are located along coastal regions. Although observations suggest significant changes in typhoon heavy rainfall, the extent to which anthropogenic forcing contributes to these changes has yet to be determined. In this study, we demonstrate that anthropogenic global warming has a substantial impact on the observed changes in typhoon heavy rainfall in the western North Pacific region. Observation data indicates that, in general, typhoon heavy rainfall has increased (decreased) in coastal East Asia (tropical western North Pacific) during the latter half of the 20th century and beyond. This spatial distribution is similar to the "anthropogenic fingerprint" observed from a set of large ensemble climate simulations, which represents the difference between Earth systems with and without human-induced greenhouse gas emissions. This provides evidence to support the claim that the significant increase in the frequency of typhoon heavy rainfall along coastal East Asia cannot be solely explained by natural variability. In addition, our results indicate that the signal of the "anthropogenic fingerprint" has been increasing rapidly since the mid-1970s and departed from natural variability in the early 2000s, indicating that the regional summer climate has already crossed the tipping point.

• 한국지구과학회지
• /
• 제44권3호
• /
• pp.185-195
• /
• 2023

The prolonged and heavy East Asian summer precipitation in 2020 may have been caused by an enhanced Madden-Julian Oscillation (MJO), which requires evaluation using forecast models. We examined the performance of GloSea6, an operational forecast model, in predicting the East Asian summer precipitation during July 2020, and investigated the role of MJO in the extreme rainfall event. Two experiments, CON and EXP, were conducted using different convection schemes, 6A and 5A, respectively to simulate various aspects of MJO. The EXP runs yielded stronger forecasts of East Asian precipitation for July 2020 than the CON runs, probably due to the prominent MJO realization in the former experiment. The stronger MJO created stronger moist southerly winds associated with the western North Pacific subtropical high, which led to increased precipitation. The strengthening of the MJO was found to improve the prediction accuracy of East Asian summer precipitation. However, it is important to note that this study does not discuss the impact of changes in the convection scheme on the modulation of MJO. Further research is needed to understand other factors that could strengthen the MJO and improve the forecast.

• 한국해양환경ㆍ에너지학회지
• /
• 제18권3호
• /
• pp.143-156
• /
• 2015

서태평양에 위치한 해저산 해역($150.2^{\circ}E$, $20^{\circ}N$ 부근)에서 수층 환경의 동적 특성을 파악하고자 수괴 및 용존산소, 무기영양염(질소, 인), 엽록소-a 등과 같은 수층 환경 인자의 거동을 살펴보았다. 2014년 10월에 해저산(OSM14-2)을 중심으로 동-서 및 남-북 방향으로 총 9개의 정점에서 CTD system을 이용하여 물리 화학적 자료를 획득하였다. 수온-염분 도표로부터 연구 해역에서 파악된 수괴는 표층에서 북태평양 열대수와 수온약층수, 중층에서 북태평양 중층수 그리고 저층에서 북태평양 심층수로 구분되었다. 용존산소 농도가 낮은 최소층(평균 $73.26{\mu}M$)은 산소 결핍 환경(dysoxic<$90{\mu}M$)으로 연구 해역 전반에 걸쳐 수심 700~1,200 m 사이에 분포하였다. 아질산염+질산염과 인산염으로 대표되는 무기영양염은 표면혼합층 내에서 빈영양 환경을 보인 후 수심 증가에 따라 점차적으로 증가해 용존산소 최소층에서 최대 농도를 나타냈으며, N:P ratio(13.7) 결과로부터 연구 해역은 식물플랑크톤이 성장하기에 질소 성분이 제한된 환경으로 파악되었다. 해저산을 중심으로 동-서 및 남-북 정점 라인에서 환경 인자의 수직 분포는 서쪽과 남쪽 해역에서 저층수 유입에 의한 영향으로 수심 500 m 부근에서 그리고 수심 2,500 m 이하의 저층 내에서도 서쪽 해역과 남쪽 해역에서 반대 해역과 비교해 환경 인자의 농도가 다르게 분포하였다. Redfield ratio(N:P=16:1)을 이용하여 구해진 Excess N 값은 연구 해역 전반에 걸쳐 음의 값을 보여 질소 제거 기작이 우세한 환경임을 나타냈으며, 서쪽 해역과 남쪽 해역 저층에서 상대적으로 높은 값이 관측되었다. 이러한 결과들은 해저산의 지형적인 특성이 저층 해류 순환에 영향을 미치고 이는 수층 환경 인자들의 거동을 결정하는데 중요하게 작용함을 지시한다.

• 한국제4기학회:학술대회논문집
• /
• 한국제4기학회 2004년도 추계학술대회
• /
• pp.37-43
• /
• 2004

The response of the CCCma coupled climate model to the imposition of LGM conditions is investigated. The global mean SAT and SST decrease by about $10^{\circ}C$ and $5.6^{\circ}C$ in the coupled model. Tropical SST decreases by $6.5^{\circ}C$, whereas CLIMAP reconstructions suggest that the tropics cool by only about $1.7^{\circ}C$, although the larger tropical cooling is consistent with the more recent proxy estimates. With the incorporation of a full ocean component, the coupled model gives a realistic spatial SST pattern, capturing features associated with ocean dynamics that are seen in the CLIMAP reconstructions. The larger decrease of the surface temperature in the model is associated with a reduction in global precipitation rate (about 15%). The tropical Pacific warm pool retreats to the west and a mean La $Ni\tilde{n}a$-like response is simulated with less precipitation over the central Pacific and more in the western tropical Pacific. The more arid ocean climate in the LGM results in an increase in SSS almost everywhere. This is particularly the case in the Arctic Ocean where large SSS increase is due to a decrease in river discharge to the Arctic Ocean associated with the accumulation of snow over the ice sheet, but in the North Atlantic by contrast SSS decreases markedly. This remarkable reduction of SSS in the North Atlantic is attributed to an increase in fresh water supply by an increase in discharges from the Mississippi and Amazon rivers and an increase in P-E over the North Atlantic ocean itself. The discharges increase in association with the wetter LGM climate south of the Laurentide ice sheet and in South America. The fresh water capping of the northern North Atlantic results in a marked reduction of deep convection and consequently a marked weakening of the North Atlantic overturning circulation. In the LGM, the maximum overturning stream function associated with the NADW formation decreases by about 60% relative to the control run, while in the Southern Ocean, oceanic convection is stronger in the LGM due to reduced stratification associated with an increase in SSS and a decrease in SST and the overturning stream function associated with the formation of AABW and the outflow increases substantially.

• 한국지구과학회지
• /
• 제23권4호
• /
• pp.369-379
• /
• 2002

저온 습윤한 1993년 여름철과 고온 건조한 1994년 여름철과 관련된 동아시아에서 대조적인 여름철 몬순순환의 특성을 상, 하층 대류권의 대기순환 특성과 함께 전구 해수온도 및 적도 대류성 강수장을 분석함으로써 조사하였다. 1993년의 경우, 동아시아, 중앙 북태평양 및 미국 서부지역에서 500hpa 면과 200hpa 면의 음의 지위고도 편차가 나타났지만, 1994년의 경우, 이들 지역들에서 양의 편차를 보였다. 1993년의 아열대 제트류는 평년보다 다소 남쪽에 치우쳐져 한반도 북쪽에 위치하였다. 서태평양 아열대 고기압이 남쪽으로 이동하여 동아시아지역에는 평년보다 많은 여름철 강수와 낮은 여름철 기온이 나타났다. 이는 오오츠크해로부터 동해로 저온 습윤한 기단의 확장에 때문으로 판단된다. 대조적으로 1994년의 아열대 제트류는 평년보다 다소 북쪽에 위치하였고, 서태평양 아열대 고기압의 갑작스런 북상은 동아시아 여름철 강수대의 북상을 동반하였다. 따라서, 아시아 여름철 강수 및 기온 편차는 1993년과 반대 양상을 보였다. 적도 태평양상의 해수온 편차에서는, 1993년은 엘니뇨가, 1994년은 라니냐가 각각 나타났다. 오스트레일리아 고기압과 마스카렝 고기압의 북서 연변을 따른 하층 적도 횡단류와 관련된 서태평양과 인도양에서 이상적인 대류성 강수는 이들 대조적인 동아시아 여름철의 대규모 대기순환에 영향을 준 것으로 판단된다. 또한, 동아시아 여름몬순지역에서 평균된 200 hPa 면의 동서바람편차는 한반도 여름 기온편차와 음의 상관을 보였다.

• 대기
• /
• 제27권1호
• /
• pp.1-16
• /
• 2017

In this study, trends of upper jet stream characteristics (intensity, altitude, latitude, and longitude) over the Asia-North Pacific region during the recent 30 (1979~2008) years were analyzed by using four reanalysis datasets (CFSR, ERA-Int., JRA-55, MERRA). We defined the characteristics of upper jet stream as the averages of mass weighted wind speed, mass-flux weighted altitude, latitude and longitude between 400 and 100 hPa. Due to the vertical averaging of jet stream characteristics, our results reveal a weaker spatial variabilities and trends than previous studies. In general, the four reanalysis datasets show similar jet stream properties (intensity, altitude, latitude and longitude) although the magnitude and trends are slightly different among the reanalysis datasets. The altitude of MERRA is slightly higher than that of others for all seasons. The domain averaged intensity shows a weakening trend except for winter and the altitude of jet stream shows an increasing trend for all seasons. Also, the meridional trend of jet core shows a poleward trend for all seasons but it shows a contrasting trend, poleward trend in the continental area but equatorward trend in the Western Pacific region during summer. The zonal trend of jet core is very weak but a relatively strong westward trend in jet core except for spring and winter. The trends of jet stream characteristics found in this study are thermodynamically consistent with the global warming trends observed in the Asia-Pacific region.