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应用生态学报 ›› 2022, Vol. 33 ›› Issue (10): 2785-2795.doi: 10.13287/j.1001-9332.202210.021

• 研究论文 • 上一篇    下一篇

涡度相关观测的太湖CH4通量数据插补方法评价

邱吉丽1, 张弥1*, 蒲旖旎1, 张圳2, 贾磊1, 赵佳玉1, 肖薇1, 刘寿东1   

  1. 1南京信息工程大学气候与环境变化国际合作联合实验室大气环境中心, 南京 210044;
    2南京市江宁区气象局, 南京 211100
  • 收稿日期:2021-11-17 修回日期:2022-07-18 出版日期:2022-10-15 发布日期:2023-04-15
  • 通讯作者: * E-mail: zhangm.80@nuist.edu.cn
  • 作者简介:邱吉丽, 女, 1998年生, 硕士研究生。主要从事地-气交换研究。E-mail: 1071632846@qq.com
  • 基金资助:
    国家重点研发计划项目(2020YFA0607500)和国家自然科学基金项目(41575147,41975143)

Evaluation of gap-filling methods for CH4 flux data based on eddy covariance method in the Lake Taihu, China

QIU Ji-li1, ZHANG Mi1*, PU Yi-ni1, ZHANG Zhen2, JIA Lei1, ZHAO Jia-yu1, XIAO Wei1, LIU Shou-dong1   

  1. 1Yale-NUIST Center on Atmospheric Environment, Nanjing University of Information Science & Technology, Nanjing 210044, China;
    2Jiangning District Meteorological Bureau, Nanjing 211100, China
  • Received:2021-11-17 Revised:2022-07-18 Online:2022-10-15 Published:2023-04-15

摘要: 涡度相关法是在湖泊开展CH4通量长期连续观测的重要方法。受到多种因素的影响,CH4通量观测数据存在大量缺失。为重构完整的CH4通量时间序列,就需要适宜的数据插补方法。本研究利用太湖涡度通量观测网络东部的避风港站点2014—2017年的常规气象数据及涡度相关观测的CH4通量数据,在分析半小时尺度以及日尺度CH4通量影响要素的基础上,测试了非线性回归法以及随机森林算法和误差反向传播算法在半小时尺度及日尺度上插补CH4通量缺失数据的可行性。结果表明: 在半小时尺度上,避风港站生长季CH4通量主要受到底泥温度、摩擦风速、气温、相对湿度、潜热通量和20 cm处水温的影响,非生长季主要受到相对湿度、潜热通量、风速、感热通量和底泥温度的影响,而在日尺度上CH4通量主要受潜热通量和相对湿度的影响。在对CH4通量缺失数据的插补中,随机森林模型在所有时间尺度上都表现为最佳的插补性能,其中,将日序、太阳高度角、底泥温度、摩擦风速、气温、20 cm处水温、相对湿度、气压和风速作为输入变量的随机森林模型更适用于半小时尺度缺失数据的插补;将日序、底泥温度、摩擦风速、气温、20 cm处水温、相对湿度、气压、风速和向下短波辐射作为输入变量的随机森林模型更适用于日尺度缺失数据的插补;整体上,插补模型对日尺度缺失数据的插补优于半小时尺度。

关键词: 涡度相关方法, CH4通量, 数据插补, 随机森林, BP神经网络

Abstract: Eddy covariance method has become a key technique to measure CH4 flux continuously in lakes. A large number of CH4 flux data was missing due to variable reasons. In order to reconstruct a complete time series of CH4 flux, it is necessary to find an appropriate gap-filling method to insert the CH4 flux data gap. Based on the routine meteorological data and CH4 flux data measured at Bifenggang site in the eastern part of the Taihu eddy flux network during 2014 to 2017, we analyzed the control factors of CH4 flux at the half-hour scale and daily scale. With those data, we tested that whether nonlinear regression method and two machine learning methods, random forest algorithm and error back propagation algorithm, could fill the CH4 flux gap at the half-hour scale and daily scale. The results showed that CH4 flux at the half-hour scale was mainly influenced by sediment temperature, friction velocity, air temperature, relative humidity, latent heat flux and water temperature at 20 cm in the growing season, and was mainly affected by relative humidity, latent heat flux, wind speed, sensible heat flux and sediment temperature in non-growing season. The CH4 flux at the daily scale was mainly affected by latent heat flux and relative humidity. Random forest model was the best in CH4 flux data gap filling at both time scales. The random forest model with the input variables of day of year, solar elevation angle, sediment temperature, friction velocity, air temperature, water temperature at 20 cm, relative humidity, air pressure, and wind speed was more suitable for filling the CH4 flux data gap at the half-hour scale. The random forest model with the input variables of day of year, sediment temperature, friction velocity, air temperature, water temperature at 20 cm, relative humidity, air pressure, wind speed, and downward shortwave radiation was more suitable for filling CH4 flux data gap at the day scale. The interpolation models could fill the data gap better at daily scale than that at the half-hour scale.

Key words: eddy covariance method, CH4 flux, gap filling, random forest, back propagation neural network