戈壁地区夏季碳和水热循环及其湍流特征

本文利用2006年夏季大气边界层观测资料,采用涡动相关法分析了我国西北地区戈壁下垫面碳收支及水热循环的规律和特征,并分析了大气湍流特征.结果表明:夏季白天的CO₂湍流通量呈逆输送特征,即CO₂白天向下输送,夜间向上输送,平均数值为-0.199 mg·m^-2·s^-1,整体上表现为碳汇;戈壁地区湿度小,其数值受水平来流的影响较大,日变化特征不明显;温度的归一化标准差与稳定度参数的关系满足Monin-Obukhov Similarity (MOS)理论;温度和CO₂的能谱相似;互谱uc与uθ,wc与wθ相似;水汽和CO₂的输送主要受水平方向湍流的影响.

Characteristics of carbon dioxide, thermo-hydrological fluxes and atmospheric turbulence structure over Gobi Desert

Based on the turbulence data obtained from an atmospheric boundary layer station located in Gobi Desert in northwest China during the summer of 2006, the carbon dioxide fluxes, latent heat fluxes and sensible heat fluxes were investigated. The results showed that the carbon dioxide flux was transferred down to land surface in daytime but conversely at night, and the mean value of carbon dioxide flux was -0.199 mg·m^-2·s^-1, which indicated that the Gobi Desert was a carbon sink in summer. Since the value of the moisture content of the surface layer over the Gobi Desert was small, the specific humidity is almost passively controlled by horizontal moisture fluxes and its diurnal variation was unobvious. On the other hand, the statistical characteristic of the turbulent transport of temperature was in accordance with Monin-Obukhov Similarity theory. The normalized spectra of temperature were similar with that of the CO₂ concentration (c). The normalized cospectra of u-wind component (u) and carbon dioxide (c) were similar with that of u and the potential temperature (θ). The normalized cospectra of the vertical wind component (w) and carbon dioxide (c) were similar with that of w and θ. The transport of humidity and CO₂ depended on horizontal fluxes.