Comparing Wind Data at Local Meteorological Stations and in Forested Areas Using Roughness Length and Topographic Exposure Indices

Abstract

This study evaluates whether wind data at local meteorological stations can be used for studying wind damage in forested areas. Data from four Automated Meteorological Data Acquisition System (AMeDAS) stations and one weather station, located in the northern and southern portions of Hokkaido Island, was compared with wind data collected at flux towers located in the Teshio and Tomakomai regional forests. Anemometers were affixed to the flux towers at a height of 32 m in Teshio and 40 m in Tomakomai; thus, the data was assumed to adequately represent wind conditions in a forested area without vegetation effects. Mean wind speed at the AMeDAS stations and weather station sites was converted to extreme wind speed using roughness length on eight directions. This comparison was based on the storm (October to May) and typhoon (August and September) seasons. Subsequently, a distance-limited topographic exposure index (TOPEX) was calculated for all anemometer positions using 1, 2, 5, and 10 km distances from the position. We found that wind at sites with low TOPEX scores and small roughness length could significantly represent wind conditions in nearby forested areas. Wind speeds with high TOPEX scores but small roughness length occasionally showed correlation with conditions at the flux tower. Although additional study is required, using TOPEX with roughness length could be beneficial for deriving suitable wind data sets that correlate with wind conditions in nearby forested areas.