塔克拉玛干沙漠腹地春、夏季CO_2通量特征

CO_2 flux characteristics of Taklimakan Desert in spring and summer

利用世界上唯一深入流动沙漠腹地200 km以上的塔克拉玛干沙漠塔中站所采集的2011年4月、7月的气象资料,分析了塔克拉玛干沙漠腹地春、夏季CO2通量的变化特征及影响因素。结果表明:塔克拉玛干沙漠腹地CO2通量表现为白昼地表吸收CO2,夜间地表排放CO2,且地表吸收强度明显大于地表排放;塔克拉玛干沙漠腹地春、夏季CO2平均净吸收速率分别为0.93μmol·m2·s-1和0.82μmol·m2·s-1;CO2通量受大气稳定性影响较大,稳定大气条件利于沙漠地表CO2的释放,不稳定大气条件有利于沙漠地表CO2的吸收;此外,地表温度、土壤湿度、风速均与CO2通量呈不同程度的负相关关系。

To make it clear that whether desert is somewhat a sink of carbon or a source of carbon,CO2 flux was measured in April and July of 2011 in Taklimakan Desert,the biggest desert in China and the world’s second-largest flow desert that just smaller than Sahara Desert in Africa. This paper analyzed the CO2 flux variation characteristics and impact factors of Taklimakan Desert in spring and summer in 2011. The pulse data are measured by OPEC open eddy detection system,the gradient data are measured by 10-meters observation tower,and the meteorological data are collected by Tazhong Station,which is the only meteorological station deep over 200 km in drifting desert in the world. It is worth pointing out that the instruments are installed in sand surface in order to exclude the influence of green plants. The conclusion shows that Taklimakan Desert is sink of carbon and CO2 absorption rate is affected by multiple factors. The results are as follows： CO2 is absorbed during the day and released at night in hinterland of Taklimakan Desert and CO2 absorption is significantly greater than release. Absorption peak appears at noon time. CO2 flux direction changes from absorption to release at sunset and release to absorption at sunrise. The average net absorption of spring and summer is about 0.93 μmol·m2·s-1and 0.82 μmol·m2·s-1respectively. CO2 flux shows different degrees of negative correlation with land surface temperature,soil moisture and wind speed. That is to say the absorption of CO2 increases with the increasing temperature,moisture and wind speed. It is reported that Ca O which can chemically react with CO2 in the sand of hinterland of Taklimakan desert is much more than that in the marginal area. Soil temperature and moisture may affect the reaction rate.When the wind speed increases,vertical turbulent transport of the surface layer increases too. This may be the reason why CO2 flux changes with wind speed. CO2 flux is influenced by atmospheric stability. Negative CO2 flux is concentrated in the range of Z/L〈0. Conversely,positive value is concentrated in Z/L〉0. But whether positive or negative,all CO2 flux date is concentrated in the range of ｜Z/L｜〈0.5. In other words,stable atmospheric conditions are conducive to the release of CO2 and unstable atmospheric conditions are conducive to the absorption.