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141.
142.
Integrating lysimeter drainage and eddy covariance flux measurements in a groundwater recharge model
Vicente Vásquez Anton Thomsen Bo V. Iversen Rasmus Jensen Rasmus Ringgaard 《水文科学杂志》2013,58(9):1520-1537
AbstractField-scale water balance is difficult to characterize because controls exerted by soils and vegetation are mostly inferred from local-scale measurements with relatively small support volumes. Eddy covariance flux and lysimeters have been used to infer and evaluate field-scale water balances because they have larger footprint areas than local soil moisture measurements. This study quantifies heterogeneity of soil deep drainage (D) in four 12.5-m2 repacked lysimeters, compares evapotranspiration from eddy covariance (ETEC) and mass balance residuals of lysimeters (ETwbLys), and models D to estimate groundwater recharge. Variation in measured D was attributed to redirection of snowmelt infiltration and differences in lysimeter hydraulic properties caused by surface soil treatment. During the growing seasons of 2010, 2011 and 2012, ETwbLys (278, 289 and 269 mm, respectively) was in good agreement with ETEC (298, 301 and 335 mm). Annual recharge estimated from modelled D was 486, 624 and 613 mm for three calendar years 2010, 2011 and 2012, respectively. In summary, lysimeter D and ETEC can be integrated to estimate and model groundwater recharge.
Editor D. Koutsoyiannis 相似文献
143.
基于水下滑翔机观测资料,对南海北部一个反气旋涡旋的温度细结构进行了特征分析.温度细结构强度由温度的脉动值确定,并随着尺度的增加呈指数衰减.在垂直方向上,细结构强度随着深度的加深而减弱,细结构特征在海洋表层(0~100m)和表层以下(>100 m)存在显著区别.表层内,垂向混合和水平混合对细结构强度均有贡献,细结构强度大... 相似文献
144.
Cloud droplet dispersion is an important parameter in estimating aerosol indirect effect on climate in general circulation
models (GCMs). This study investigates droplet dispersion in shallow cumulus clouds under different aerosol conditions using
three-dimensional large eddy simulations (LES). It is found that cloud droplet mean radius, standard deviation, and relative
dispersion generally decrease as aerosol mixing ratio increases from 25 mg−1 (clean case) to 100 mg−1 (moderate case), and to 2000 mg−1 (polluted case). Under all the three simulated aerosol conditions, cloud droplet mean radius and standard deviation increase
with height. However, droplet relative dispersion increases with height only in the polluted case, and does not vary with
height in the clean and moderate cases. 相似文献
145.
A real case study for the transformation of Tropical Storm (TS) Haima (2004) into an extratropical cyclone (EC) is carried out numerically since,after landfall,Haima (2004) (as an EC) brought severe weather to a large area (from the south to the north) in China during 13-16 September 2004.With the linear diagnostic model (derived in a previous study) for the tangentially-averaged radial-vertical circulation within vortices moving on the spherical Earth,Haima’s (2004) life cycle is reconstructed noticeably well.Therefore,the major contributor could be identified confidently for Haima’s (2004) extratropical transition based on the diagnostic model outputs.The quantitative comparison shows that up to a 90% contribution to the innerregion updraft and a 55% contribution to the upper-layer outflow come from latent heating during Haima’s (2004) TS stage.Up to a 90% contribution to the inner-region updraft and nearly a 100% contribution to the upper-layer outflow come from the upper-layer eddy angular momentum advection (EAMA) during Haima’s (2004) EC stage.Representing the asymmetric structure of the storm,the predominantly positive contribution of the upper-layer EAMA to Haima’s (2004) transformation is closely associated with the Sshaped westerlies in the upper layer with two jets.One jet in the cyclonic-curvature area carries cyclonic angular momentum into the storm,and the other jet in the anticyclonic-curvature area carries anticyclonic angular momentum out of the storm.Consequently,the newly-increased cyclonic tangential wind is deflected by the Coriolis force to the right to form the upper-layer outflow accompanied by the central-area rising motion,leading to Haima’s (2004) extratropical transition after its landfall. 相似文献
146.
采用大涡模型对L形和U形三维钝体建筑物的绕流特性和风压分布特性进行数值研究。考虑平均和脉动速度入口边界,在雷诺数为1.5×10~5~7×10~5条件下,对2种钝体的9种分析工况进行瞬态动力分析,并将计算结果与已有研究进行对比。研究表明,钝体绕流对周围流场影响的强弱程度依次为尾流区、屋顶区、来流区,影响大小随着流场与钝体之间距离、钝体建筑高宽比、离地高度的增大而减小,且对来流区0.25H、屋顶上部0.4H、左右两侧0.5H、尾流区2.0H范围内流场的影响最大;钝体迎风面风压分布比较均匀,而侧面、背面和顶面受绕流涡旋的影响较大,平均风压分布较为复杂,并与脉动风压分布具有类似的变化趋势。研究结果对结构抗风设计与建筑风环境设计具有一定的参考价值。 相似文献
147.
148.
2013年12月华东地区发生历史罕见的超过20 d连续重度霾天气过程。本文利用NCEP/NCAR再分析资料、华东地区大气细颗粒浓度资料以及常规气象观测资料对此次天气过程的环流形势、持续机制和前期外强迫因子展开分析。结果表明,此次华东连续重度霾天气和东亚中高纬阻塞高压活动密切相关。2013年12月白令海到鄂霍茨克海阻塞活动加强导致东亚地区天气瞬变扰动异常偏弱,贝加尔湖东侧弱高空脊长时间维持,我国东部地区受弱偏北风影响,大气扩散条件较差,有利于华东本地大气细颗粒物积累和北方霾粒子向华东地区输送。进一步研究表明2013年12月鄂霍茨克海阻塞高压活动偏强可能和前期热带印度洋暖海温异常有关。 相似文献
149.
Robin S. Keir Oliver Schmale Maren Walter Jürgen Sültenfuß Richard Seifert Monika Rhein 《Earth and Planetary Science Letters》2008,270(3-4):338-348
Hydrothermal emission of mantle helium appears to be directly related to magma production rate, but other processes can generate methane and hydrogen on mid-ocean ridges. In an on-going effort to characterize these processes in the South Atlantic, the flux and distribution of these gases were investigated in the vicinity of a powerful black smoker recently discovered at 8°17.9' S, 13°30.4' W. The vent lies on the shoulder of an oblique offset in the Mid-Atlantic Ridge and discharges high concentrations of methane and hydrogen. Measurements during expeditions in 2004 and 2006 show that the ratio of CH4 to 3He in the neutrally buoyant plume is quite high, 4 × 108. The CTD stations were accompanied by velocity measurements with lowered acoustic Doppler current profilers (LADCP), and from these data we estimate the methane transport to have been 0.5 mol s− 1 in a WSW-trending plume that seems to develop during the ebb tidal phase. This transport is an order of magnitude greater than the source of CH4 calculated from its concentration in the vent fluid and the rise height of the plume. From this range of methane fluxes, the source of 3He is estimated to be between 0.14 and 1.2 nmol s− 1. In either case, the 3He source is significantly lower than expected from the spreading rate of the Mid-Atlantic Ridge. From the inventory of methane in the rift valley adjacent to the vent, it appears that the average specific rate of oxidation is 2.6 to 23 yr− 1, corresponding to a turnover time between 140 and 16 days. Vertical profiles of methane in the surrounding region often exhibited Gaussian-like distributions, and the variances appear to increase with distance from the vent. Using a Gaussian plume model, we obtained a range of vertical eddy diffusivities between 0.009 and 0.08 m2m2 s− 1. These high values may be due to tidally driven internal waves across the promontory on which the vent is located. 相似文献
150.
Delayed baroclinic response of the Antarctic circumpolar current to surface wind stress 总被引:2,自引:0,他引:2
The Antarctic Circumpolar Current (ACC) responds to the surface windstress via two processes, i.e., the instant barotropic process and the delayed baroclinic process. This study focuses on the baroclinic instability mechanism in ACC, which was less reported in the literatures. Results show that the strengthening of surface zonal windstress causes the enhanced tilting of the isopycnal surface, leading to more intense baroclinic instability. Simultaneously, the mesoscale eddies resulting from the baro- clinic instability facilitate the transformation of mean potential energy to eddy energy, which causes the remarkable decrease of the ACC volume transport with the 2-year lag time. This delayed negative cor- relation between the ACC transport and the zonal windstress may account for the steadiness of the ACC transport during last two decades. 相似文献