Abstract
A chill unit has been used to estimate chilling requirement for dormancy release and risk of freezing damage. A system that calculates chill units was developed to obtain site-specific estimates of dormancy release date for grapes and evaluated in Baekgu myun near Kimje City, Chunbuk, Korea from September 2002 to March 2003. The system utilized daily minimum and maximum temperature maps generated from spatial interpolation with temperature correction for topography. Hourly temperature was temporally interpolated from the daily data using a sine-exponential equation (Patron and Logan, 1981). Hourly chill units were determined from sigmoid, reverse sigmoid, and negatively increasing sigmoid functions based on temperature ranges and summed for 24 h. Cumulative daily chill units obtained from measurements did not increase until 20 October 2002, which was used as a start date for accumulation to estimate the dormancy release date. As a result, a map of dormancy release date in the study area was generated, assuming 800 chill units as a threshold for the chilling requirement. The chill unit accumulation system, implemented using Microsoft Visual Basic and C++ (Microsoft, Redmond, WA, USA), runs in the Windows environment with ArcView (ESRl Inc., Redlands, CA, USA).
기온의 공간변이가 심한 넓은 지역에서 Chill Unit 축적량과 휴면해제일의 공간분포를 얻기 위해서 Utah Chill Unit 모형을 지리정보시스템과 결합하여 Chill Unit 공간적산기(CUMAP)을 개발하였다. CUMAP은 Grid 형태의 일 최고, 최저기온을 입력받아 시간내삽법에 의해 매시기온을 추정하고, Utah 모형에 의해 매시 Chill Unit을 계산한다. 하루 단위로 Chill Unit이 누적되면 Grid파일로 저장되며, 사용자가 정하는 저온요구량(임계값)에 도달하는 날짜를 역시 Grid파일로 생성한다. 전라북도 김제시 백구면 일대 포도재배지역에 대해 CUMAP을 적용하여 10m 해상도의 Chill Unit 일별 적산값과 휴면해제일 추정분포도를 작성하였다.
