LI-COR產品測得渦度協方差數據助力科學家發重要文章

瀏覽次數：2981　發布日期：2015-9-2　來源：本站　本站原創，轉載請注明出處

近日，美國科學家M. A. Rawlins等人發表了一篇題為《Assessment of model estimates of land-atmosphere CO₂ exchange across Northern Eurasia》的文章，文中用到了橫跨歐亞大陸北部流域4個研究區域的6個通量塔獲取的渦度協方差數據，對凈生態系統生產力（NEP）及其組分總初級生產力（GPP）、生態系統呼吸（ER）和土壤碳的滯留時間進行了系統分析，從而使用渦度協方差的測量方法對多種陸地-大氣層CO₂交換的模型進行了有效的評估。該項研究在通量觀測領域一經問世便獲得了大量的關注，其中通量塔的數據均由LI-7500A CO₂/H₂O分析儀，LI-7200 CO₂/H₂O分析儀，和LI-7700開路式CH₄分析儀測量得到。

文章原文摘要：

Abstract. A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land-atmosphere carbon dioxide (CO₂) cycling through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary roductivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of Northern Eurasia. The retrospective simulations cover the period 1960–2009 at 0.5_ resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO₂ fluxes derived from sitebased eddy covariance measurements as well as regionalscale GPP estimates based on satellite remote-sensing data.

The site-based comparisons depict a tendency for overestimates in GPP and ER for several of the models, particularly at the two sites to the south. For several models the spatial pattern in GPP explains less than half the variance in the MODIS MOD17 GPP product. Across the models NEP increases by as little as 0.01 to as much as 0.79 g Cm^-2 yr^-2, equivalent to 3 to 340% of the respective model means, over the analysis period. For the multimodel average the increase is 135% of the mean from the first to last 10 years of record (1960–1969 vs. 2000–2009), with a weakening CO₂ sink over the latter decades. Vegetation net primary productivity increased by 8 to 30% from the first to last 10 years, contributing to soil carbon storage gains. The range in regional mean NEP among the group is twice the multimodel mean, indicative of the uncertainty in CO₂ sink strength. The models simulate that inputs to the soil carbon pool exceeded losses, resulting in a net soil carbon gain amid a decrease in residence time. Our analysis points to improvements in model elements controlling vegetation productivity and soil respiration as being needed for reducing uncertainty in landatmosphere CO₂ exchange. These advances will require collection of new field data on vegetation and soil dynamics, the development of benchmarking data sets from measurements and remote-sensing observations, and investments in future model development and intercomparison studies.

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http://www.biogeosciences.net/12/4385/2015/bg-12-4385-2015.pdf

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