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순차적인 최적화 기법에 의한 생물계절모형 모수추정 방식 개선
윤경담 ( Kyung Dahm Yun ),김수형 ( Soo Hyung Kim ) 한국농림기상학회 2014 한국농림기상학회지 Vol.16 No.4
Accurate prediction of peak bloom dates (PBD) of flowering cherry trees is critical for organizing local cherry festivals and other associated cultural and economic activities. A two-step phenology model is commonly used for predicting flowering time depending on local temperatures as a result of two consecutive steps followed by chill and heat accumulations. However, an extensive computation requirement for parameter estimation has been a limitation for its practical use. We propose a sequential parameterization method by exploiting previously unused records of development stages. With an extra constraint formed by heat accumulation between two intervening stages, each parameter can then be solved sequentially in much shorter time than the brute-force method. The result was found to be almost identical to the previous solution known for cherry trees (Prunus × yedoensis) in the Tidal Basin, Washington D.C.
복잡지형 고해상도 격자망에서의 PRISM 기반 강수추정법
정유란 ( U Ran Chung ),윤경담 ( Kyung Dahm Yun ),조경숙 ( Kyung Sook Cho ),이재현 ( Jae Hyun Yi ),윤진일 ( Jin I. Yun ) 한국농림기상학회 2009 한국농림기상학회지 Vol.11 No.2
The demand for rainfall data in gridded digital formats has increased in recent years due to the close linkage between hydrological models and decision support systems using the geographic information system. One of the most widely used tools for digital rainfall mapping is the PRISM (parameter-elevation regressions on independent slopes model) which uses point data (rain gauge stations), a digital elevation model (DEM), and other spatial datasets to generate repeatable estimates of monthly and annual precipitation. In the PRISM, rain gauge stations are assigned with weights that account for other climatically important factors besides elevation, and aspects and the topographic exposure are simulated by dividing the terrain into topographic facets. The size of facet or grid cell resolution is determined by the density of rain gauge stations and a 5×5km grid cell is considered as the lowest limit under the situation in Korea. The PRISM algorithms using a 270m DEM for South Korea were implemented in a script language environment (Python) and relevant weights for each 270m grid cell were derived from the monthly data from 432 official rain gauge stations. Weighted monthly precipitation data from at least 5 nearby stations for each grid cell were regressed to the elevation and the selected linear regression equations with the 270m DEM were used to generate a digital precipitation map of South Korea at 270m resolution. Among 1.25 million grid cells, precipitation estimates at 166 cells, where the measurements were made by the Korea Water Corporation rain gauge network, were extracted and the monthly estimation errors were evaluated. An average of 10% reduction in the root mean square error (RMSE) was found for any months with more than 100mm monthly precipitation compared to the RMSE associated with the original 5km PRISM estimates. This modified PRISM may be used for rainfall mapping in rainy season (May to September) at much higher spatial resolution than the original PRISM without losing the data accuracy.
통신 : DTS (Days Transformed to Standard temperature) 생육 모델을 활용한 군위 지역의 "후지" 사과 성숙기 예측
최인태 ( In Tae Choi ),심교문 ( Kyo Moon Shim ),김용석 ( Yong Seok Kim ),정명표 ( Myung Pyo Jung ),윤경담 ( Kyung Dahm Yun ),김수형 ( Soo Hyung Kim ) 한국환경과학회 2015 한국환경과학회지 Vol.24 No.11
Fuji apple variety introduced in Japan has excellent storage quality and good taste so it is most commonly cultivated in the Korean Peninsula. Accurate prediction of harvest maturity allows farmers to more efficiently manage their farm, such as working time, fruit storage, market shipment and labor distribution so it is very important. This study was carried out to predict the harvest maturity of ‘Fuji’ apple using DTS (Days Transformed to Standard temperature) model based on the Arrhenius law in the Gunwi province of the South Korea. Input data are daily average temperature and apple harvest maturity. Predicted the harvest maturity of Fuji apple after estimating the optimal parameters by using the Nelder-Mead method. The differences of observed and predicted harvest maturity day are approximately 1 to 4 days and the RMSE is 2.9.