Evaluating a Model of Evaporation and Transpiration with Observations in a Partially Wet Douglas-Fir Forest   总被引：1，自引：0，他引：1  

Fred C. Bosveld  Willem Bouten 《Boundary-Layer Meteorology》2003,108(3):365-396

The Penman–Monteith equation is extended to describe evaporation of intercepted rain, transpiration and the interaction between these processes in a single explicit function. This single-layer model simulates the effects of heat exchange, stomatal blocking and changed humidity deficit close to the canopy as a function of canopywater storage. Evaporation depends on the distribution of water over the canopy and the energy exchange between wet and dry parts. Transpiration depends on the dry canopy surface resistance that is described with a Jarvis-type response. The explicit functions obtained for water vapour fluxes facilitate a straightforward identificationof the various processes. Canopy water storage amounts and xylem sapflow were measured simultaneously during drying episodes after rainfall in a dense, partially wet, Douglas-fir forest. Estimates of evaporation and transpiration rates are derived from these observations. The analysis shows that evaporation induced transpirationreduction is mainly caused by energy consumption. Changes in water vapour deficit have a minor effect due to a compensating stomatal reaction. The remaining difference between observed and modelled transpiration reduction can be attributed to partial blocking of stomata by the water layer.  相似文献   

Implementation of a Coupled Atmosphere-Wave-Ocean Model in the Mediterranean Sea: Sensitivity of the Short Time Scale Evolution to the Air-Sea Coupling Mechanisms     

P. Lionello  G. Martucci  M. Zampieri 《Journal of Atmospheric & Ocean Science》2003,9(1):65-95

In this study a coupled regional atmosphere-wave-ocean model has been implemented in the Mediterranean Sea and applied to the simulation of the atmospheric circulation and of the upper ocean structure on the short time scale range typical of regional meteorological predictions. The coupling accounts for the feedback of the upper ocean on the atmospheric circulation, that is for the variation of the SST (Sea Surface Temperature) during the development of the cyclones and for the dependence of the SSR (Sea Surface Roughness) on the wind-wave spectrum. The model can operate also in uncoupled mode, with prescribed SST and SSR computed using the Charnock formula (depending on wind speed only). Six case-studies, characterized by strong cyclones and intense air-sea interaction, have been analyzed. A sensitivity analysis is carried out by comparing uncoupled and coupled simulations, carried out including the SST and SSR-feedbacks both separately and simultaneously. The feedbacks have systematic effects on the atmospheric precipitation, on heat and momentum fluxes, and, consequently, on MLD (Mixed Layer Depth), SST, and SWH (Significant Wave Height). For all these quantities, except for SWH, the two feedbacks act in opposite directions. The effect of the SST feedback is larger on latent heat flux, precipitation, sea surface cooling, and, marginally, on mixed layer growth and it determines their reduction when the two feedbacks act simultaneously. The SSR and SST-feedbacks have comparable effect on the SWH field and they both contribute to the SWH reduction. Though the SLP (Sea Level Pressure) and Geopotential minima of single "fall" case-studies can be appreciably modified by the inclusion of the feedbacks, no systematic effect has been identified in these fields, presumably because of the intrinsic unpredictability of the atmospheric circulation.  相似文献   

Infrared galaxies in compact groups     

B. Kelm  P. Focardi  A. Zampieri 《Astrophysics and Space Science》2003,284(2):471-474

IR properties of Compact Group (CG) galaxies are presented and compared with IR properties of isolated galaxies. Despite CGs displaying more E-S0s and optically bright galaxies, no differences are retrieved concerning FIR emission. The observed lack of strong FIR enhancement in the CG sample is not surprising when interpreting FIR sources in CGs as accordant redshift projections, rather than as mergers in progress. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

西太平洋副热带高压和台风相互作用的数值试验研究   总被引：11，自引：0，他引：11  

任素玲刘屹岷  吴国雄 《气象学报》2007,65(3):329-340

利用1958—1998年台风资料,对台风路径进行分类,挑选出3类常见路径作为研究对象,通过合成分析,证实不同的台风路径所对应的副热带高压(副高)形势不同。台风西行时,西太平洋副热带高压势力强大,呈东西向带状,台风沿着副高南部西行,副高在整个过程中西伸;转向路径时,副高开始呈东西向带状,随着台风的移动副高主体东退,在160°E附近中间断裂;北上路径的台风对应的副高主体偏东。在此基础上,利用气候模式R42L9在不同的初始场中加入相同的温度扰动,成功模拟出西行和北上路径的台风,验证了不同副高形态对台风路径的不同影响。对模拟结果的分析还发现,台风可以引起正压Rossby波向中高纬度的传播。由于背景流场不同,不同移动路径的台风其波动能量的传播路径也不同,从而对中高纬度环流和西太平洋副高产生不同的影响:与北上台风不同,西行台风在其西北方向激发出正变高,使西太平洋副高加强西伸。  相似文献   

A three-dimensional code for muon propagation through the rock: MUSIC     

P. Antonioli  C. Ghetti  E.V. Korolkova  V.A. Kudryavtsev  G. Sartorelli 《Astroparticle Physics》1997,7(4):357-368

We present a new three-dimensional Monte-Carlo code MUSIC (MUon SImulation Code) for muon propagation through the rock. All processes of muon interaction with matter with high energy loss (including the knock-on electron production) are treated as stochastic processes. The angular deviation and lateral displacement of muons due to multiple scattering, as well as bremsstrahlung, pair production and inelastic scattering are taken into account. The code has been applied to obtain the energy distribution and angular and lateral deviations of single muons at different depths underground. The muon multiplicity distributions obtained with MUSIC and CORSIKA (Extensive Air Shower simulation code) are also presented. We discuss the systematic uncertainties of the results due to different muon bremsstrahlung cross-sections.  相似文献   

Localized multiscale energy and vorticity analysis: I. Fundamentals   总被引：1，自引：0，他引：1  

X. San Liang  Allan R. Robinson   《Dynamics of Atmospheres and Oceans》2005,38(3-4):195-230

A new methodology, multiscale energy and vorticity analysis (MS-EVA), is developed to investigate the inference of fundamental processes from oceanic or atmospheric data for complex dynamics which are nonlinear, time and space intermittent, and involve multiscale interactions. Based on a localized orthogonal complementary subspace decomposition through the multiscale window transform (MWT), MS-EVA is real problem-oriented and objective in nature. The development begins with an introduction of the concepts of scale and scale window and the decomposition of variables on scale windows. We then derive the evolution equations for multiscale kinetic and available potential energies and enstrophy. The phase oscillation reflected on the horizontal maps from Galilean transformation is removed with a 2D large-scale window synthesis. The resulting energetic terms are analyzed and interpreted. These terms, after being carefully classified, provide four types of processes: transport, transfer, conversion, and dissipation/diffusion. The key to this classification is the transfer–transport separation, which is made possible by looking for a special type of transfer, the so-called perfect transfer. The intricate energy source information involved in perfect transfers is differentiated through an interaction analysis.The transfer, transport, and conversion processes form the basis of dynamical interpretation for GFD problems. They redistribute energy in the phase space, physical space, and space of energy types. These processes are all referred to in a context local in space and time, and therefore can be easily applied to real ocean problems. When the dynamics of interest is on a global or duration scale, MS-EVA is reduced to a classical Reynolds-type energetics formalism.  相似文献   

寒区冻土环境与工程环境间的相互作用   总被引：24，自引：6，他引：18  

吴青柏  刘永智 《工程地质学报》2000,8(3):281-287

从冻土环境和工程环境相互作用着手 ,分析了青藏公路建设过程中的冻土环境破坏、环境保护状况及冻土环境保护对工程建设的重要性 ,同时对正在拟建的青藏铁路 ,阐述了人类经济活动对冻土环境和工程环境的影响 ,并初步提出寒区冻土、工程环境质量监测、管理和评价系统的设计框架.  相似文献   

Interactions of chlorpyrifos and methyl mercury: a mechanistic approach to assess chemical mixtures   总被引：1，自引：0，他引：1  

J. A. Steevens  W. H. Benson   《Marine environmental research》2000,50(1-5):113-117

The mechanism of interaction between chlorpyrifos, an organophosphate insecticide, and methyl mercury was assessed utilizing the amphipod, Hyalella azteca. Previous studies have demonstrated that chlorpyrifos and methyl mercury interact additively with survival as the endpoint. In addition, exposure to chlorpyrifos and methyl mercury increased the accumulation and decreased the elimination of methyl mercury. To further examine the mechanism responsible for these interactions, the in vivo and in vitro inhibition of acetylcholinesterase enzyme activity was assessed following exposure to methyl mercury and chlorpyrifos. In vivo, methyl mercury antagonized the effects of chlorpyrifos on acetylcholinesterase inhibition. Additional studies demonstrated that methyl mercury did not affect the in vitro bioactivation of chlorpyrifos or the subsequent inhibition of acetylcholinesterase enzyme activity. Chemical-chemical interactions were examined utilizing chromatographic techniques and suggested the formation of a chlorpyrifos-methyl mercury complex. The formation of this complex may result in increased accumulation of methyl mercury, apparent additive toxicity, and protection against chlorpyrifos-mediated acetylcholinesterase inhibition.  相似文献   

Hunter‐gatherer response to late Holocene climatic variability in northern and central Australia     

Alan N. Williams  Sean Ulm  Ian D. Goodwin  Mike Smith 《第四纪科学杂志》2010,25(6):831-838

Sum probability analysis of 1275 radiometric ages from 608 archaeological sites across northern and central Australia demonstrates a changing archaeological signature that can be closely correlated with climate variability over the last 2 ka. Results reveal a marked increase in archaeological records across northern and central Australia over the last 2 ka, with notable declines in western and northern Australia between ca. AD 700 and 1000 and post‐AD 1500 – two periods broadly coeval with the Medieval Climatic Anomaly and the Little Ice Age as they have been documented in the Asia–Pacific region. Latitudinal and longitudinal analysis of the dataset suggests the increase in archaeological footprint was continent wide, while the declines were greatest from 9 to 20° S, 110 to 135° E and 143 to 150° E. The change in the archaeological data suggests that, combined with an increase in population over the late Holocene, a disruption or reorganisation of pre‐European resource systems occurred across Australia between ca. AD 700 and 1000 and post‐AD 1500. These archaeological responses can be broadly correlated with transitions of the El Niño–Southern Oscillation (ENSO) mean state on a multi‐decadal to centennial timescale. The latter involve a shift towards the La Niña‐like mean state with wetter conditions in the Australian region between AD 700 and 1150. A transition period in ENSO mean state occurred across Australia during AD 1150–1300, with persistent El Niño‐like and drier conditions to ca. AD 1500, and increasing ENSO variability post‐AD 1500 to the present. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Influence of surface forcing on near-surface and mixing layer turbulence in the tropical Indian Ocean     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

An autonomous upwardly-moving microstructure profiler was used to collect measurements of the rate of dissipation of turbulent kinetic energy (ε) in the tropical Indian Ocean during a single diurnal cycle, from about 50 m depth to the sea surface. This dataset is one of only a few to resolve upper ocean ε over a diurnal cycle from below the active mixing layer up to the air–sea interface. Wind speed was weak with an average value of ~5 m s⁻¹ and the wave field was swell-dominated. Within the wind and wave affected surface layer (WWSL), ε values were on the order of 10⁻⁷–10⁻⁶ W kg⁻¹ at a depth of 0.75 m and when averaged, were almost a factor of two above classical law of the wall theory, possibly indicative of an additional source of energy from the wave field. Below this depth, ε values were closer to wall layer scaling, suggesting that the work of the Reynolds stress on the wind-induced vertical shear was the major source of turbulence within this layer. No evidence of persistent elevated near-surface ε characteristic of wave-breaking conditions was found. Profiles collected during night-time displayed relatively constant ε values at depths between the WWSL and the base of the mixing layer, characteristic of mixing by convective overturning. Within the remnant layer, depth-averaged values of ε started decaying exponentially with an e-folding time of 47 min, about 30 min after the reversal of the total surface net heat flux from oceanic loss to gain.  相似文献