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841.
842.
Effects of the soil heat flux estimates on surface energy balance closure over a semi-arid grassland 下载免费PDF全文
Soil heat flux is important for surface energy balance (SEB), and inaccurate estimation of soil heat flux often leads to surface
energy imbalance. In this paper, by using observations of surface radiation fluxes and soil temperature gradients at a semi-arid
grassland in Xilingguole, Inner Mongolia, China from June to September 2008, the characters of the SEB for the semi-arid grassland
were analyzed. Firstly, monthly averaged diurnal variations of SEB components were revealed. A 30-min forward phase displacement
of soil heat flux (G) observed by a fluxplate at the depth of 5-cm below the soil surface was conducted and its effect on the SEB was studied.
Secondly, the surface soil heat flux (G
s) was computed by using harmonic analysis and the effect of the soil heat storage between the surface and the fluxplate on
the SEB was examined. The results show that with the 30-min forward phase displacement of observed G, the slope of the ordinary linear regression (OLR) of turbulent fluxes (H+LE) against available energy (R
n-G) increased from 0.835 to 0.842, i.e., the closure ratio of SEB increased by 0.7%, yet energy imclosure of 15.8% still existed
in the SEB. When G
s, instead of G was used in the SEB equation, the slope of corresponding OLR of (H+LE) against (R
n-G
s) reached 0.979, thereby the imclosure ratio of SEB was reduced to only 2.1%. 相似文献
843.
Estimating erroneous parameters in ensemble based snow data assimilation system has been given little attention in the literature. Little is known about the related methods’ effectiveness, performance, and sensitivity to other error sources such as model structural error. This research tackles these questions by running synthetic one-dimensional snow data assimilation with the ensemble Kalman filter (EnKF), in which both state and parameter are simultaneously updated. The first part of the paper investigates the effectiveness of this parameter estimation approach in a perfect-model-structure scenario, and the second part focuses on its dependence on model structure error. The results from first part research demonstrate the advantages of this parameter estimation approach in reducing the systematic error of snow water equivalent (SWE) estimates, and retrieving the correct parameter value. The second part results indicate that, at least in our experiment, there is an evident dependence of parameter search convergence on model structural error. In the imperfect-model-structure run, the parameter search diverges, although it can simulate the state variable well. This result suggest that, good data assimilation performance in estimating state variables is not a sufficient indicator of reliable parameter retrieval in the presence of model structural error. The generality of this conclusion needs to be tested by data assimilation experiments with more complex structural error configurations. 相似文献
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Evidence for Palaeozoic magmatism recorded in the Late Neoproterozoic Marlborough ophiolite,New England Fold Belt,central Queensland 总被引:1,自引:1,他引:0
The ultramafic‐mafic complex in the Marlborough terrane of the northern New England Fold Belt is dominated by members of a Neoproterozoic (ca 560 Ma) ophiolite (V1). The ophiolite has been intruded by the products of three Palaeozoic tectonomagmatic episodes (V2, V3 and V4). The V2 magmatic episode is represented by tholeiitic and calc‐alkaline basalts and gabbros of island‐arc affinities. Sm/Nd isotopes give a whole‐rock isochron age of 380 ± 19 Ma (2σ) to this episode, some 180 million years younger than the V1 ophiolitic rocks. The V3 magmatic episode includes tholeiitic and alkali basalts with enriched geochemical signatures characteristic of intraplate volcanism. A whole‐rock Sm/Nd isochron age of 293 ± 35 Ma is obtained for this event. A fourth magmatic event (V4) is represented by basaltic andesites and siliceous intrusives with geochemical features similar to modern adakites. This event has its type locality in the Percy Isles. These data provide tectonic and geochronological constraints for the previously enigmatic Marlborough terrane and as such contribute to the ever‐evolving understanding of New England Fold Belt development. 相似文献
850.
青藏公路沿线热喀斯特湖分布特征及其热效应研究 总被引:1,自引:1,他引:0
热喀斯特湖的出现和发育是多年冻土变暖的指示器,研究热喀斯特湖发育及其热效应是应对青藏高原气候变化和人类活动诱发冻土灾害的基础工作.基于SPOT-5卫星影像资料,在ArcGIS平台下解译遥感影像,获取了青藏公路沿线楚玛尔河至风火山段热喀斯特湖的数量和分布特征,这些热喀斯特湖以楚玛尔河高平原和北麓河盆地为主要分布区,且80%发育于高含冰量多年冻土区.热喀斯特湖通过竖向和侧向2种传热方式影响多年冻土,竖向传热会造成其下部多年冻土融穿,侧向传热会造成湖岸多年冻土增温,扩大热影响范围.通过北麓河地区一典型热喀斯特湖的数值计算,湖全年都在向湖岸放热.当热喀斯特湖离路基较近,将会对公路产生潜在或者直接的危害,其侧向热侵蚀往往会导致冻土路基温度升高,诱发路基病害. 相似文献