Analysis of Agricultural Climatology in Cheju Island I. Distribution of Daily Minimum Temperature in Winter Season Estimated from a Topoclimatological Method

제주도의 농업기후 분석 I. 지형기후 추정법과 동계 일최저기온 분포

Agricultural activities in Chejudo require more specialized weather services in this region. The meteorological information available from the Korea Meteorological Service (KMS) is limited in its areal coverage because the KMS stations are located along the narrow band of coastal area. topoclimatological technique which makes use of empirical relationships between the topography and the weather can be applied to produce reasonable estimates of the climatic variables such as air temperature and precipitation over remote land area where routine observations are rare. Presentation of these estimates in a from of fine-mesh grid map can also be helpful to upgrade the quality of weather services in this region. Altitude values of the 250 m grid points were read from a 1: 25000 topographic map and the mean altitude, the mean slope, and the aspect of the slope were determined for each 1 km$^2$ land area from these altitude data. Daily minimum air temperature data were collected from 18 points in Chejudo during the winter period from November 1987 to February 1988. The data were grouped into 3 sets based on synoptic pressure pattern. Departures from the KMS observations were regressed to the topographical variables to delineate empirical relationships between the local minimum temperature under specific pressure patterns and the site topography. The selected regression equations were used to calculate the daily minimum temperature for each 1 km$^2$ land area under the specific pressure patterns. The outputs were presented in a fine-mesh grid map with a 6-level contour capability.

종관기상자료만으로 충족시킬 수 없는 농업분야 국지기상정보 수요에 대처하기 위해 지형기후 관계식에 의거한 제주도 전역의 정밀기후 추정 및 표출방법을 개발하였다. 먼저 도전역을 250m 간격의 직교격자로 구획하고 교차점의 해발고도를 지형도상에서 판독하여 사방 1km 지역(단위격자)의 평균해발고도, 평균경사도, 그리고 평균 경사방향 등 지형내자를 계산, 정량화하였다. 18개의 기존 및 신설 기상관측소가 위치한 단위격자의 지형 인자값과 실제 관측된 일최저기온값을 중회귀분석하여 지형일기온 관계식을 도출하고 이로부터 미관측 격자에 대하여 주정치를 계산하였다. 구체적으로 겨울철 일최저기온에 대하여 3개의 전형적인 기압계 유형별로 최적 추정식을 만들어 해안지대에 위치한 제주 및 서귀포 관측자료와 기압계 유형판별만으로 도전역의 일최저온 분포 예측을 가능케 하였다.