SST产品误差在海-气CO_2通量计算中的传递及贡献分析

ERROR IN SST PRODUCT: PROPAGATION IN THE ESTIMATION OF SEA-AIR CO_2 FLUX

海-气界面CO2通量的估算对于碳的生物地球化学循环和全球气候变化等研究具有重要的意义,利用遥感手段是进行全球尺度海表面碳通量估算的唯一手段,但是由于不确定性的存在限制了海-气界面CO2通量遥感估算产品在决策应用上的可靠性。本文通过建立海-气界面CO2通量直接控制参量(气体交换速率k、海表面CO2溶解度S和海表面CO2分压pCO2sw)误差结构图,以通量估算的主要影响因子——海表温度(SST)为例,建立了SST在通量计算中的误差传递流程图,并采用Monte Carlo方法模拟了SST误差在通量计算中的传递规律和对最终误差的贡献。结果表明在遥感SST误差为±0.5°C并为正态分布的假设下,误差在k、S计算中的传递为指数分布和近似指数分布,而在pCO2sw模型计算中为正态分布,最终在通量FC O中的传递为指数分布;在大气CO22分压为固定值370μatm的情况下,SST对最终的通量结果带来的误差为±1.2mmol/(m2·d)左右。本文以SST为例,提供了一种通量计算中遥感参数误差传递和贡献的计算方法,可以为其它遥感获取的参量提供分析依据和参考。

Estimation of sea-air CO2 flux is indispensable for a wide range of research especially for carbon biogeochemical cycles and globe climate change. The distribution and CO2 flux are highly variable in surface seawater and vary over a broad spectrum in time and space scales, and there is considerable interest in the use of satellite remotely sensed data to provide synoptic maps of sea-air CO2 flux. However, a great deal of uncertainties are associated with the current remote sensing products of sea-air CO2 flux due to many error sources, which limits largely its application on decision making. Taking SST, the major impact factor on the estimation of sea-air CO2 flux as an example, we presented in a flowchart how the error propagates during the flux calculation with parameters including gas transfer velocity(k), sea surface CO 2 solubility(S), and the partial pressure of CO2 at sea surface(pCO2sw). In addition, using Monte Carlo simulation, we analyzed the transfer law and the final contribution from the error to understand how SST error affects the flux interaction. The results indicate that under the assumption that remote sensing SST error is ±0.5°C and in normal distribution, the SST error transfer law was exponential distributed in k parameterization, and approximately exponential distributed in S parameterization, while normally distributed in pCO2sw parameterization and exponential distributed in CO2 flux; and when atmospheric CO2 partial pressure was fixed at the value of 370μatm, SST brought an error of ±1.2 mmol·m?2·day?1 to the final result of the flux. These results may provide a basis and reference for analyzing other parameters of remote sensing.