福建沿海地区海陆风的时空分布特征

Spatial and temporal distribution characteristic of sea-land breeze over the Fujian coast

本文利用福建沿海8个70 m及2个100 m高度梯度测风塔1 a的多层风观测数据,分析福建沿海海陆风的时空及日变化特征.10个测风塔均匀分布于从南到北沿海,2009年6月1日～2010年5月31日开展了为期1 a的观测,采用50 m高度夜间02:00时前后的风向度数与午后14:00时前后的风向度数相减,其差值的绝对值在90°～270°之间,并且海风及陆风的维持时间均大于3 h,定义为海陆风日.分析表明,受台湾海峡的影响,福建沿海海陆风日数南、北多,中部少,中部沿海海陆风日在44～60 d之间,长乐以北沿海为66～94 d,漳浦以南为69～92 d.海陆风的季节变化表现为春季最多,夏季其次,秋季最少.海陆风的日变化特征表现为:春季陆风变海风的时间在09:00～10:00时左右,夏季在08:00～09:00时左右,秋冬季在09:00～10:00时左右;而海风变陆风的时间各季均在20:00时左右.海陆风的转换一般从低层开始,至100 m高度相差30 min左右;由于受地形的影响,福建沿海大多数海陆风日有其特点,即风向转换时角度变化较小,风向不与海岸线垂直,反而近于与海岸平行;海陆风转换时,当海风为偏北风时,上午陆风变海风时风向顺时针偏转,傍晚逆时针偏转,由海风变陆风;当海风为偏南风时,正好相反.

Based on one year muhilevel integrated data of eight 70 m and two 100 m gradient wind towers evenly distributed along the Fujian coast from south to north, the spatial and temporal distribution and daily variation of the sea-land breeze were analyzed. Observations over one year were carried out from June 1, 2009 to May 31, 2010. Days with 50 m-height-winds difference between 02：00 am to 02：00 pm fall in the absolute value of 90° -270° and with both sea breeze and land breeze maintained more than 3 hours were defined as sea-land breeze days. It showed that, due to the influence of Taiwan Strait, there were more sea-land breeze days over the south and north Fujian coast than over the middle Fujian coast. The sea-land breeze days were about 44 - 60 d in the middle coast, about 66 - 94 d in the northern coast of Changle, and 69 - 92 d in the southern coast of Zhangpu. The largest seasonal variation of sea-land breeze was in the spring, followed by the summer, and with least variation in the autumn. The sea-land breeze daily variation characteristics were that land breeze to sea breeze in spring, autumn and winter occurred from 09：00 to 10：00 am, and in summer occurred from 08：00 to 09：00 am, and the shift from sea breeze to land breeze occurred at about 08：00 pm for each season. The sea-land breeze direction shift starts from lower, with a 30-minute-difference from lower range to 100 m height. Because of the influence of the terrain, most sea-land breeze days had the following characteristics： a lesser angle change in direction shift, wind direction not perpendicular to but almost parallel to the coast; in the shifting of sea-land breeze, if sea breeze wind direction was north, the wind direction would change clockwise from land breeze to sea breeze in the morning, while changing counter clockwise from sea breeze to land breeze in the evening; and the reverse was true when sea breeze wind direction was south.