• Journal of the Korean earth science society
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• v.30 no.4
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• pp.464-477
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• 2009

In this study, we examined the patterns of local circulation over the Daechung lake area through the numerical experiment designed to investigate the impact of lake on the local circulation. The results of numerical experiment showed that the surface temperature predicted by WRF model was lower than the observation, while the wind speed was stronger than the observation. The local circulation over the lake area was characterized by a lake breeze induced by a horizontal thermal contrast between the lake surface and the Surrounding land. At Daecheong Lake, a lake breeze formed at 09 LST and dissipated at 18 LST, with maximum intensity at 15 LST. The vertical extent of the simulated circulation was about 1,200 m. The specific humidity increased as the humid air above the lake moved landward due to the daytime circulation of the lake breeze. The numerical experiments of sensitivity to existence of the lake showed that the simulated surface temperature decreased in the experiment with the lake. Wind speed was more intense around the lake area when the actual land use was substituted by grassland land use. The results of numerical experiments suggest that the lake-induced lake breeze circulation has an effect on the meteorology of planetary boundary layer around the lake.

• Korean Journal of Agricultural and Forest Meteorology
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• v.12 no.1
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• pp.11-22
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• 2010

According to IPCC 4th Assessment Report, concentration of carbon dioxide has been increasing by 30% since Industrial Revolution. Most of IPCC $CO_2$ emission scenarios estimate that the concentration will reach up to double of its present level within 100-year if the current tendency continues. The global warming has resulted in the agro-climate change over the Korean Peninsula as well. Accordingly, it is necessary to understand the future agro-climate induced by the increase of greenhouse gases in terms of the agro-climatic indices in the Korean peninsula. In this study, the future climate is simulated by an atmosphere/ocean/land surface/sea ice coupled general circulation climate model, Pusan National University Coupled General Circulation Model(hereafter, PNU CGCM), and by a regional weather prediction model, Weather Research and Forecasting Model(hereafter, WRF) for the purpose of a dynamical downscaling. The changes of the vegetable period and the crop growth period, defined as the total number of days of a year exceeding daily mean temperature of 5 and 10, respectively, have been analyzed. Our results estimate that the beginning date of vegetable and crop growth periods get earlier by 3.7 and 17 days, respectively, in spring under the $CO_2$-doubled climate. In most of the Korean peninsula, the predicted frost days in spring decrease by 10 days. Climatic production index (CPI), which closely represent the productivity of rice, tends to increase in the double $CO_2$ climate. Thus, it is suggested that the future $CO_2$ doubled climate might be favorable for crops due to the decrease of frost days in spring, and increased temperature and insolation during the heading date as we expect from the increased CPI.

• Atmosphere
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• v.25 no.4
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• pp.669-683
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• 2015

In this study, we investigated the prediction skills of four multiple linear regression methods for monthly air temperature over South Korea. We used simulation results from four regional climate models (RegCM4, SNURCM, WRF, and YSURSM) driven by two boundary conditions (NCEP/DOE Reanalysis 2 and ERA-Interim). We selected 15 years (1989~2003) as the training period and the last 5 years (2004~2008) as validation period. The four regression methods used in this study are as follows: 1) Homogeneous Multiple linear Regression (HMR), 2) Homogeneous Multiple linear Regression constraining the regression coefficients to be nonnegative (HMR+), 3) non-homogeneous multiple linear regression (EMOS; Ensemble Model Output Statistics), 4) EMOS with positive coefficients (EMOS+). It is same method as the third method except for constraining the coefficients to be nonnegative. The four regression methods showed similar prediction skills for the monthly air temperature over South Korea. However, the prediction skills of regression methods which don't constrain regression coefficients to be nonnegative are clearly impacted by the existence of outliers. Among the four multiple linear regression methods, HMR+ and EMOS+ methods showed the best skill during the validation period. HMR+ and EMOS+ methods showed a very similar performance in terms of the MAE and RMSE. Therefore, we recommend the HMR+ as the best method because of ease of development and applications.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.306-306
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• 2023

인공강우 실험은 일반적으로 호우 기간 중 수행한다. 과거 연구(국립기상과학원, 2020)에서 설정된 인공강우 실험 기준은 "일 강우량 20 mm를 초과하는 경우"로, 이는 경험적으로 결정된 기준이다. 이에 본 연구에서는 가용한 장기간 관측자료를 수집하고 자료를 분석하여 인공강우 실험을 위한 댐 유역의 기상학적 조건과 수문학적 조건을 평가하였다. 인공강우 실험 조건 평가를 위한 대상 유역으로 한반도 남부지방에 위치한 보령댐, 용담댐, 남강댐, 안동댐, 임하댐 유역을 고려하였다. 기상학적 조건은 인공강우 발생 조건과 밀접한 연관이 있다. 기상학적 조건을 평가하기 위한 자료로 장기간 자료가 가용하며 수집이 용이한 일 강우량, 상대습도, 운량 등의 자료를 수집하였다. 강우량과 운량의 경우 상위 10%, 20%, 30%에 대응하는 기준치를 산정하고, 이를 초과하는 연 횟수를 비교하여 유역의 조건을 평가하는데 반영하였다. 상대습도의 경우 연중 80%, 85%, 90%를초과하는 횟수를 비교하고 추가로 이 기준치를 초과함에도 강우는 발생하지 않은 횟수도 고려하였다. 수문학적 조건은 인공강우의 필요성, 즉 수자원 공급량 차원에서 고려한 조건으로 볼 수 있다. 수문학적 조건을 평가하기 위한 자료로는 댐의 일 및 월 단위 저수용량을 수집하고, 댐의 총 저수용량과 유효저수용량에 대한 비를 산정하여 평가에 고려하였다. 댐 유역의 인공강우 실험 조건을 평가한 결과는 다음과 같이 요약된다. 기상조건을 고려한다면 보령댐과 용담댐이 적절한 것으로 판단되었다. 특히 보령댐의 경우, 상대습도가 90% 이상으로 매우 높음에도 대기중의 수증기가 응결되지 못하여 강우량이 발상하지 않는 경우가 있어 Seeding의효과가 극대화될 여지가 높은 것으로 판단된다. 수문학적 조건을 고려하는 경우, 보령댐 유역, 안동댐 유역, 임하댐 유역이 유효 저수율이 낮은 것으로 나타나 인공강우를 활용한 수자원 확보의 필요성이 높은 유역으로 평가된다.