温室气体甲烷质量浓度变化规律

Volume concentration variation and law of greenhouse gas methane

利用Hilbert Huang变换方法对青海瓦里关观测站1991-05—2010-12期间的月平均甲烷质量浓度观测值进行研究。研究结果表明:瓦里关自1991年以来甲烷质量浓度呈递增趋势,其月平均值比全球甲烷质量浓度平均值高60-110μg/L;瓦里关甲烷质量浓度的瞬时增长率趋势与甲烷全球平均瞬时增长率趋势一致,但是,其波动范围更大,增长率在8-23μg/(L·a)内波动,而全球平均波动范围为-5-15μg/(L·a);质量浓度变化存在6个本征周期,分别是4月、7月、约1a、约2a、约5 a和约11a;其中约1a的周期与离瓦里关站最近的西宁市气温变化1a周期、西宁市降水11月周期紧密相关,约11 a的周期与太阳黑子活动的11a周期相关性大,说明它们是引起甲烷质量浓度变化的重要因素。

Hilbert-Huang transform （HHT） method was used to study the monthly average CH4 measurement data during May, 1991 and December, 2010 from Mt. Waliguan station. The results show that in Waliguan, CH4 volume concentration has increased gradually since 1991 and the monthly average is generally higher from 60 μg/L to 110 μg/L than the globalmonthly average. The trend of CH4 instantaneous growth rate is the same as the global average instantaneous growth rate in Waliguan, but it has a wide fluctuation range, and its value fluctuates between -8 μg/（L.a） and 23 μg/（L.a）, with contrast to global average between -5 μg/（L.a） and 15 μg/（L.a）. CH4 volume concentration variation of Waliguan exists six intrinsic cycles and they are as follows： 4 months, 7 months, about 1 a, about 2 a, about 5 a and about 11 a. The about 1 a cycle is closely related to the temperature 1 a cycle and rainfall 11 months cycle of Xining, where is the closest city from Waliguan station, and about 11 a cycle is related to sunspot variability 11 a cycle, and all these facts explain that they are important factors which would cause the CH4 volume concentration fluctuate.