近14a宁波机场低云的统计特征分析

Statistical Characteristics Analysis of Low Clouds at Ningbo Airport over the Past 14 Years

摘要: 利用宁波机场2012年1月~2025年12月的低云观测资料，分析了机场低云量、云底高的日变化、年变化和年际变化特征。结果表明，宁波机场累年平均低云量为3.5/8，2012~2019年年平均低云量在其平均值上下波动，2019年开始呈下降趋势，2025年最明显；累年平均低云云底高为1034 m，近14年呈明显的上升趋势。夏季出现BKN量级低云最多，BKN低云量白天多于夜间，下午多于上午，夜间变化稳定，06时出现频率最高为17%，14时之后频率最低；冬季出现OVC量级的低云最多，OVC低云量出现频率与BKN低云量呈反位相，21~23时频率最高均为31%，05~08时频率最低为27%。机场对流云的累年平均频率为4%，最多出现在8月份，频率为15%；峰值为7~8月份的06~09时，频率 ≥ 30%；1月份从未出现过对流云。450 m低云(非对流云、云高低于450 m)的累年平均频率为9%，1~6月份是高发期，2月份为峰值，频率12%；7~10月份进入低发期，8月份为谷值；日变化表现为凌晨至上午出现频率高，午后至上半夜出现频率低。

Abstract: Using low cloud observation data from Ningbo Airport spanning January 2012 to December 2025, this study analyzed the diudrnal, annual and interannual variations in low cloud cover and cloud base height. Results show that the long-term average low cloud cover at Ningbo Airport is 3.5/8, from 2012 to 2019, the annual mean low cloud amount fluctuated up and down, and since 2019 it has shown a decreasing trend, with the most pronounced decrease occurring in 2025. The long-term average cloud base height of low clouds is 1034m, showing a clear upward trend over the past 14 years. BKN-level low clouds occur most frequently during summer, with higher daytime than nighttime occurrence, more in the afternoon than morning; nighttime variation is stable, peaking at 06:00 with a frequency of 17%, and lowest after 14:00. OVC-level low clouds are most common in winter, occurring in opposite phases to BKN clouds-peaking between 21:00 and 23:00 at 31% each, and lowest between 05:00 and 08:00 at 27%. The long-term average frequency of convective clouds at the airport is 4%, peaking in August at 15%; the highest frequency occurs between 06:00 and 09:00 in July and August, reaching ≥ 30%; convective clouds have never been observed in January. Other low clouds (non-convective, cloud base below 450 m) have a long-term average frequency of 9%, with peak occurrence from January to June, reaching a maximum in February at 12%; they enter a low-frequency period from July to October, with the lowest frequency in August. Diurnally, these clouds appear frequently from early morning to mid-morning but less so from afternoon to late night.