龙凤山本底站大气CO2数据筛分及浓度特征研究

针对黑龙江龙凤山区域大气本底站2009年1月～2011年12月低层(离地10 m)和高层(离地80 m)大气CO2在线观测数据,选取低层数据重点开展研究,分析地面风向和风速等因素对观测CO2浓度的影响.结果表明,龙凤山低层大气CO2浓度明显受局地源汇影响,其与高层观测结果差异在白天08:00～17:00相对较小,小于(0.5±0.5)×10-6(物质的量比).春、夏和秋这3个季节E-ESE-SE-SSE扇区来向的地面风会明显抬升大气CO2浓度,而冬季N-NNW-NW-WNW扇区CO2浓度明显较高.该站4个季节近地面CO2浓度随着风速增大而逐渐减小,在冬季尤为明显.结合日变化及地面风的影响,对低层观测数据进行初步本底/非本底筛分,筛选出代表东北区域混合均匀CO2水平的本底数据占总数据的30.7%.本底CO2浓度季节变化显示该站大气CO2浓度呈现冬季高夏季低的趋势,季振幅约为(36.3±1.4)×10-6,明显大于同期WMO/GAW同纬度站点观测结果,2009～2011年龙凤山大气CO2平均增长率为2.4×10-6a-1.

Atmospheric CO2 Data Filtering Method and Characteristics of the Molar Fractions at the Longfengshan WMO/GAW Regional Station in China

Based on the in-situ observation results of atmospheric CO₂ molar fractions at two levels (10 m and 80 m above the ground) at Longfengshan (LFS) regional background station in Heilongjiang Province during January 2009 to December 2011, this study mainly focused on the results from 10 m above the ground level (a.g.l.). The results indicated that the observed data from 10 m were strongly affected by the local sources/sinks. The differences between the 10 m and 80 m results were relatively small during the daytime (08:00-17:00) with values smaller than (0.5±0.5)×10^-6. In spring, summer and winter, higher CO₂ molar fractions were observed when surface winds came from the E-ESE-SE-SSE sectors, while, in winter, surface winds from the N-NNW-NW-WNW sectors obviously enhanced the observed values. Generally, lower CO₂ values were accompanied with higher wind speed in the four seasons. This phenomenon was most obvious in winter. Based on the analysis of the observed diurnal cycles and the local meteorological conditions, the observed data from 10 m were filtered into background/non-background events. About 30.7% valid hourly data were filtered as regional background representative. The background CO₂ variation displayed a peak in winter and a valley in summer with a seasonal peak to peak amplitude of (36.3±1.4)×10^-6, which was higher than the values at similar latitude from Marine Boundary Layer (MBL) References and WMO/GAW stations. The yearly CO₂ increasing rate at LFS was roughly estimated to be 2.4×10^-6 a^-1.