The UCD advanced canopy-atmosphere-soil algorithm: Comparisons with observations from different climate and vegetation regimes
The UCD advanced canopy-atmosphere-soil algorithm: Comparisons with observations from different climate and vegetation regimes
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DOI：
10.1002/qj.49712656917
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发表时间：
2000-10-01
影响因子：
8.9
通讯作者：
U, KTP
中科院分区：
文献类型：
--
作者：
Pyles, RD;Weare, BC;U, KTP
提出了加州大学戴维斯分校（UCD）的高级冠层-大气-土壤算法（ACASA），并将其输出与六个不同地点的综合观测结果进行了比较。ACASA是一个多层冠层-表面层模型，它将稳态雷诺数平均流体流动方程求解到三阶。这些方程包括稳态、水平齐次、非绝热的矢量和标量通量和通量输运的显式表示。ACASA包括一种四阶、接近精确的技术，用于计算冠层内不同水平的叶、茎和土壤表面温度和表面能量通量。植物对微环境条件的生理反应也包括使用Ball-Berry/von caemmer - farquhar配方。将荷兰的草地、加拿大的落叶针叶林、巴西的热带牧场和森林以及美国的古温带雨林的观测能量通量和微环境条件与模拟值进行了比较。结果表明，所有6个站点的所有地表通量的月至年平均值的模拟估计值和观测估计值在95%置信阈值内一致。观测到的每小时净辐射估计值和模拟的每小时净辐射估计值也与所考虑的所有地点非常一致。在大多数情况下，每小时观测和模拟的感热通量和潜热通量估计值在统计上非常一致。ACASA与观测到的感热和潜热通量估计值之间存在的差异与观测不确定性的大小相同。在大多数情况下，观测和模拟的每小时冠层和地面储热值的估计值与观测值的一致性在95%的统计置信范围内。在热带和温带雨林的所有水平上，白天冠层内平均风速、温度和比湿度的模拟值和实测值具有95%的置信度。结果还表明，总的来说，与生物圈-大气转移方案相比，ACASA产生的通量估计值更接近观测值，且散射明显更小。敏感性试验表明，降低垂直分辨率、线性化地表温度计算和/或简化表层湍流处理，在许多情况下都会改变平均感热通量和潜热通量的估计，其量在统计上是显著的。结果表明，简化模型改变了通量预测的方式，而不仅仅是与植被特征相关，并且在所有植被状态下使用ACASA是有必要的。提高20层以上的垂直分辨率改善了热带地区的通量预测，但对其他地区影响不大。
The University of California, Davis (UCD), Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) is presented and its output is compared with a comprehensive set of observations at six diverse sites. ACASA is a multi-layer canopy-surface-layer model that solves the steady-state Reynolds-averaged fluid flow equations to the third-order. These equations include an explicit representation of the steady-state, horizontally homogeneous, diabatic set of vector and scalar fluxes and flux transports. ACASA includes a fourth-order, near-exact technique to calculate leaf, stem, and soil surface temperatures and surface energy fluxes at various levels within the canopy. Plant physiological response to micro-environmental conditions is also included using Ball-Berry/von Caemmerer-Farquhar formulations. Observed energy fluxes and microenvironmental conditions from a grass held in the Netherlands, deciduous and coniferous forests in Canada, tropical pasture and forest in Brazil, and an ancient temperate rainforest in the USA are compared with simulated values.Results indicate that simulated and observed estimates of monthly to annual means of all surface fluxes agree within 95% confidence thresholds for all six sites. Observed and simulated hourly estimates of net radiation are also in excellent agreement for all sites considered. Observed and simulated hourly sensible- and latent-heat flux estimates are in very good statistical agreement in most cases. Differences that exist between ACASA and observed sensible-and latent-heat flux estimates are of the same magnitudes as observational uncertainties. Estimates of observed and simulated hourly values of canopy and ground heat storage are within 95% statistical confidence limits of agreement with observations in most cases. Simulated and measured values of daytime intra-canopy mean wind speed, temperature, and specific humidity agree with 95% confidence within both a tropical and temperate rainforest at all levels. Results also indicate that, in general, ACASA produces flux estimates closer to observations with significantly less scatter than does the Biosphere-Atmosphere Transfer Scheme. Sensitivity tests show that reducing the vertical resolution, linearizing surface temperature calculations, and/or simplifying the treatment of surface-layer turbulence each altered mean sensible- and latent-heat flux estimates by amounts that are statistically significant in many cases. Results show that simplifying the model alters flux predictions in manners not simply related to vegetation character, and that using ACASA at its full complexity for all vegetation regimes is warranted. Increasing the vertical resolution beyond 20 layers improved flux predictions at tropical locations but had little impact elsewhere.