北极地区1979—2015年西北航道7-10月份气旋的特征分析

本文采用气旋自动识别与追踪算法，基于欧洲中期天气预报中心ERA-Interim平均海平面气压场，建立1979-2015年共37年7-10月北极西北航道东西两个区域的气旋数据。数据包括气旋中心经纬度以及中心最低气压值。基于这套数据，分析了北极7-10月西北航道气旋数量特征、空间密度分布、强度特征、加深以及爆发性气旋的活动情况。西北航道东西两段的气旋个数存在显著的差异，东段气旋个数是西段区域的2~2.5倍，并且两段个数变化趋势不一致，西段的气旋个数趋势呈不显著的减少，东段的个数呈不显著上升趋势。西北航道气旋强度偏弱，中心最低气压达980 hPa的气旋仅占不到总数的5%。最低中心气压集中分布在990~1 000 hPa之间。1979-2015年以来，东段的气旋强度趋势增强，西段气旋在2002年以前也是显著的增强，2002年以后强度减弱。气旋的生命史集中在7 d以内，东段1 d以内的气旋个数明显偏多。西段气旋高密度区域主要分布在74°N以北的波弗特海北部，东段主要分布在巴芬湾的东北侧和巴芬岛的东南侧，近几年来其主要密度分布区域东西两段存在南移以及略微变化。西北航道内爆发性气旋的增长位置集中在70°N的沿岸附近，尤其是加拿大北部以及格陵兰西海岸附近。大西洋震荡指数与东段气旋的个数有较好的正相关。

The statistic and variance of cyclones in Northwest Passage of Arctic from July to October in 1979-2015

Based on the data of the ERA-Interim mean sea level pressure field in the European Center for Medium-Range Weather Forecasts, this paper uses the cyclone automatic identification and tracking algorithm to establish the cyclone data from July to October in the east and west of the Northwest Passage of the Arctic from 1979 to 2015. The data include cyclone basic latitude and longitude position information and the cyclone center minimum pressure value. Based on this set of data, this paper analyzes the climatological characteristics, spatial density distribution, cyclone intensity characteristics, cyclone deepening and the activity of explosive cyclones over the Northwest Passage from July to October. The number of cyclones at the east and west region of the Northwest Passage is significantly different. The number of cyclones at the east is more than twice that of the west, and the trend of the number of cyclones at both regions is inconsistent. The trend of the number of cyclones at the west region shows an insignificant decrease but an insignificant increase in east region. The overall cyclone intensity of the northwest channel was weak. The cyclone with the lowest atmospheric pressure reaching 980 hPa accounted for only 5% of the total number of cyclones. The lowest center of cyclone pressure is concentrated between 990-1 000 hPa. Since 1979, the overall trend of cyclone intensity in the eastern region has increased, and the cyclone in the western region also significantly increased before 2002, but the overall cyclone intensity in the western region turned weak after 2002. Cyclone life history concentrated in less than 7 days, the eastern cyclone within a day significantly more than the number of cyclones. The western region of the density distribution of cyclones is mainly distributed in the north of Beaufort Sea north of 74°N. The eastern region is mainly distributed in the northeast of Baffin Bay and the southeast of Baffin Island. In recent years, there has been a slight shift in the eastward and westward shifts of the main density distribution area of the cyclone. The growth of explosive cyclones in the Northwest Passage is concentrated near 70°N coasts, especially in northern Canada and near the west coast of Greenland. The North Atlantic Oscillation Index is significantly positively correlated with the number of cyclones in the eastern region.