Developing an empirical model of canopy water flux describing the common response of transpiration to solar radiation and VPD across five contrasting woodlands and forests

A modified Jarvis–Stewart model of canopy transpiration (E_c) was tested over five ecosystems differing in climate, soil type and species composition. The aims of this study were to investigate the model's applicability over multiple ecosystems; to determine whether the number of model parameters could be reduced by assuming that site‐specific responses of E_c to solar radiation, vapour pressure deficit and soil moisture content vary little between sites; and to examine convergence of behaviour of canopy water‐use across multiple sites. This was accomplished by the following: (i) calibrating the model for each site to determine a set of site‐specific (SS) parameters, and (ii) calibrating the model for all sites simultaneously to determine a set of combined sites (CS) parameters. The performance of both models was compared with measured E_c data and a statistical benchmark using an artificial neural network (ANN). Both the CS and SS models performed well, explaining hourly and daily variation in E_c. The SS model produced slightly better model statistics [R² = 0.75–0.91; model efficiency (ME) = 0.53–0.81; root mean square error (RMSE) = 0.0015–0.0280 mm h^‐1] than the CS model (R² = 0.68–0.87; ME = 0.45–0.72; RMSE = 0.0023–0.0164 mm h^‐1). Both were highly comparable with the ANN (R² = 0.77–0.90; ME = 0.58–0.80; RMSE = 0.0007–0.0122 mm h^‐1). These results indicate that the response of canopy water‐use to abiotic drivers displayed significant convergence across sites, but the absolute magnitude of E_c was site specific. Period totals estimated with the modified Jarvis–Stewart model provided close approximations of observed totals, demonstrating the effectiveness of this model as a tool aiding water resource management. Analysis of the measured diel patterns of water use revealed significant nocturnal transpiration (9–18% of total water use by the canopy), but no Jarvis–Stewart formulations are able to capture this because of the dependence of water‐use on solar radiation, which is zero at night. Copyright © 2012 John Wiley & Sons, Ltd.     

Predicting evaporation from mountain streams

Evaporation can be an important control on stream temperature, particularly in summer when it acts to limit daily maximum stream temperature. Evaporation from streams is usually modelled with the use of a wind function that includes empirically derived coefficients. A small number of studies derived wind functions for individual streams; the fitted parameters varied substantially among sites. In this study, stream evaporation and above-stream meteorological conditions (at 0.5 and 1.5 m above the water surface) were measured at nine mountain streams in southwestern British Columbia, Canada, covering a range of stream widths, temperatures, and riparian vegetation. Evaporation was measured on 20 site-days in total, at approximately hourly intervals, using nine floating evaporation pans distributed across the channels. The wind function was fit using mixed-effects models to account for among-stream variability in the parameters. The fixed-effects parameters were tested using leave-one-site-out cross-validation. The model based on 0.5 m measurements provided improved model performance compared to that based on 1.5 m values, with RMSE of 0.0162 and 0.0187 mm h⁻¹, respectively, relative to a mean evaporation rate of 0.06 mm h⁻¹. Inclusion of atmospheric stability and canopy openness as predictors improved model performance when using the 1.5 m meteorological measurements, with minimal improvement when based on 0.5 m measurements. Of the wind functions reported in the literature, two performed reasonably while five others exhibited substantial bias.     

Towards improved snow water equivalent retrieval algorithms for satellite passive microwave data over the mountainous basins of western USA

Space‐borne passive microwave snow water equivalent (SWE) retrieval algorithms are attractive for continuous SWE monitoring over large mountainous areas. The performance of three SWE retrieval algorithms, which were considered relevant for operational purposes, was examined for each month over the Colorado River Basin. In addition, statistical post‐processing was tested as a means of improving the SWE estimates from each algorithm. The evaluation started with the so‐called Chang equation, which was a pioneer algorithm and is still used in practice. Successive attempts were then made to improve the algorithm's performance through the calibration of the equation's coefficient and through the inclusion of brightness temperature data from various frequency channels. The Chang equation consistently underestimated SWE with average bias between 30 mm in November and more than 300 mm in April and root mean square error (RMSE) exceeding 500 mm at many locations in April. The statistical post‐processing effectively removed the bias and reduced the RMSE by half for all the months. When the Chang equation's coefficients were calibrated at each site, biases were reduced by approximately 85%, and RMSE was reduced by 40%–50%. Finally, the multiple channel equations produced unbiased SWE estimates with RMSEs 50%–60% of those from the Chang equation. However, the statistical post‐processing did not reduce RMSE for both calibrated algorithms. The last algorithm produced the most reliable estimates for at‐site analysis, but its skill deteriorated when analyses were performed over larger areal extents; therefore, it is only recommended for SWE monitoring over smaller areas. For larger areas, the calibrated Chang equation is desirable because it only requires interpolations of a calibrated coefficient, which was spatially coherent. Copyright © 2011 John Wiley & Sons, Ltd.     

Long-term variations in the muon flux angular distribution

The intensity of the atmospheric muon flux depends on many factors: the energy spectrum of primary cosmic rays and the state of the Earth’s heliosphere, magnetosphere, and atmosphere. The wide-aperture URAGAN muon hodoscope (Moscow, Russia, 55.7° N, 37.7° E, 173 m a.s.l.) makes it possible to investigate not only variations in the muon flux intensity but also temporal changes in the parameters of its angular distribution. These changes are analyzed using the vector of local anisotropy and its projections, which have different sensitivities to the parameters of modulation of both primary cosmic rays in the heliosphere and the Earth’s magnetosphere and secondary cosmic rays as they pass through the Earth’s atmosphere. The vector of local anisotropy is the sum of unit vectors (directions of the reconstructed muon tracks) normalized to the number of tracks. The results of an analysis of long-term variations in mean hourly projections of the vector of local anisotropy obtained from the 2007–2011 URAGAN hodoscope data are presented.     

Evapotranspiration models of different complexity for multiple land cover types

A comparison between half‐hourly and daily measured and computed evapotranspiration (ET) using three models of different complexity, namely, the Priestley–Taylor (P‐T), the reference Penman–Monteith (P‐M) and the Common Land Model (CLM), was conducted using three AmeriFlux sites under different land cover and climate conditions (i.e. arid grassland, temperate forest and subhumid cropland). Using the reference P‐M model with a semiempirical soil moisture function to adjust for water‐limiting conditions yielded ET estimates in reasonable agreement with the observations [root mean square error (RMSE) of 64–87 W m^?2 for half‐hourly and RMSE of 0.5–1.9 mm day^?1 for daily] and similar to the complex Common Land Model (RMSE of 60–94 W m^?2 for half‐hourly and RMSE of 0.4–2.1 mm day^?1 for daily) at the grassland and cropland sites. However, the semiempirical soil moisture function was not applicable particularly for the P‐T model at the forest site, suggesting that adjustments to key model variables may be required when applied to diverse land covers. On the other hand, under certain land cover/environmental conditions, the use of microwave‐derived soil moisture information was found to be a reliable metric of regional moisture conditions to adjust simple ET models for water‐limited cases. Further studies are needed to evaluate the utility of the simplified methods for different landscapes. Copyright © 2011 John Wiley & Sons, Ltd.     

Evaporation process modelling over northern Iran: application of an integrative data-intelligence model with the krill herd optimization algorithm

ABSTRACT

An integrated data-intelligence model based on multilayer perceptron (MLP) and krill herd optimization – the MLP-KH model – is presented for the estimation of daily pan evaporation. Daily climatological information collected from two meteorological stations in the northern region of Iran is used to compare the potential of the proposed model against classical MLP and support vector machine models. The integrated and the classical models were assessed based on different error and goodness-of-fit metrics. The quantitative results evidenced the capacity of the proposed MLP-KH model to estimate daily pan evaporation compared to the classical ones. For both weather stations, the lowest root mean square error (RMSE) of 0.725 and 0.855 mm/d, respectively, was obtained from the integrated model, while the RMSE for MLP was 1.088 and 1.197, and for SVM it was 1.096 and 1.290, respectively.     

15km3天然气球罐设计研究及优化

天然气的广泛应用,促进存储容器向大型化发展。以已投产使用的10km³天然气球罐为设计基础,设计建造完全国产化的15km³天然气球罐,利用计算参数建立有限元模型,验证模型的可靠性。建立双层拉杆模型,施加地震荷载及风载,进行动力响应分析及应力分析。为讨论双层拉杆最优位置及直径,建立了5种上下拉杆比例不同的模型,另外每种比例模型设计3种不同拉杆直径。结果表明:在8度设防二类场地地震波的情况下,上层和下层拉杆比例为0.618∶1,直径为50mm的模型对于球罐优化方面优于其他模型,球罐各项参数均显著减小且应力无放大效应。     

昆明烈度速报台网子台场地分类

依据昆明烈度速报台网子台场地钻孔资料、等效剪切波速以及地脉动测试结果,对不同强震动台站的场地划分标准作了对比.结合昆明盆地的地质构造特征,对昆明强震动烈度台站的场地类别作了判定.同时指出,对个别判定指标临近划分标准分界线的台站的分类工作还需进一步研究.     

Comparing single-phase,non-Newtonian approaches with experimental results: Validating flume-scale mud and debris flow in HEC-RAS

Post-fire debris flows and tailing impoundment failures destroy lives and property. These geologic hazards – and other similar processes – fall on a continuum between classic Newtonian flood analyses and geotechnical stability analyses. The US Army Corps of Engineers (USACE) is developing a non-Newtonian library (DebrisLib) that includes a suite of rheological and clastic approaches to hyper-concentrated, mudflow and debris flow dynamics. The Hydrologic Engineering Center (HEC) has implemented these non-Newtonian methods into the widely used, public-domain open-channel hydraulics and morphodynamic software, HEC-RAS (river analysis system). This work presents part of the verification and validation of these non-Newtonian approaches, applying several rheological equations to published laboratory results high-concentration flume experiments. This study tested the linear Bingham model as well as the turbulent and Bagnold quadratic terms of the O'Brien equation. HEC-RAS also includes the non-linear Herschel–Bulkley (HB) approach, which quantifies shear-thickening or shear-thinning processes. The study used these non-Newtonian models in HEC-RAS to simulate 10 of Parsons et al.’s (2001) flume experiments, which measured the snout and plug velocity of fluids with high solid concentrations (C_v = 68–74%) and a broad range of material gradations (d₅₀ = 0.05–1 mm, d₁₅ = 0.006–0.1 mm). The experiments also measured and back-calculated Bingham and HB parameters of the materials, finding HB powers between 0.45 and 1.25 (i.e. fluids that are dilatant, pseudo-plastic and visco-plastic). The rheological models incorporated into DebrisLib and implemented in HEC-RAS reproduce experimental data well for most experiments. The Bingham model generated a plug velocity root-mean-square error (RMSE) of 0.21 m/s using standard flow parameters and Parsons et al.’s calibrated parameters, a substantial improvement over the unmodified shallow water flow equations (RMSE 0.77 m/s). Experiments with strong snout effects tended to generate higher residuals, especially in the snout velocity. The RMSE associated with the O'Brien equation was larger with the Parsons et al. fit parameters, but similar (0.23 m/s) with measured parameters. The turbulent parameter was the largest (often the dominant) parameter in most O'Brien simulations, with the dispersive stress only proving significant for the coarsest material. DebrisLib had to use a modified version of the dispersive term to simulate these concentrations. Both the 2D depth-averaged shallow water equation (SWE) and diffusion wave equation were used to simulate the experiments. The best results were obtained with the SWE with horizontal mixing.     

Formalization of assessing radioactive waste burial site seismic regime parameters from seismological and geological data

A model is proposed that shows the relation of the block structure of the crust and earthquake sources (Sadovskii, 1979; Rodionov, 1979, 1984, 1994; Bugaev, 1999, 2011, 2014, 2015). The model can formalize how to assess the prediction of seismic regime parameters depending on the elastic limit and conditions and rate of deformation of the Earth’s crust. The spent nuclear fuel repository site in Olkiluoto (Finland) and a site in the area of the Krasnoyarsk Mining and Chemical Combine are considered as examples. It is demonstrated that the parameters of the prediction graphs limit the location of the points of magnitude repeatability graphs calculated for a site based on samples of earthquakes in the area according to different authors. This makes it possible to recommend predictive assessment of seismic regime parameters for stability monitoring of the seismic regime and safety analysis of a geological environment’s insulation properties for waste sites from the results of seismological monitoring and high-precision observations of modern movements of the Earth’s crust.     

太阳耀斑期间电离层效应的观测分析

一、一般情况 1989年7月31日到9月9目,在新乡、临潼和乌鲁木齐三点对VLF Omega信号相位变化进行了同时接收。与此同时,乌鲁木齐天文站的太阳色球观测和乌鲁木齐电离层垂测站的电离层探测也同时进行。在这期间,三个VLF信号观测点上同时有记录的太阳活动事件有36次。其中最大的发生在8月15日、16日和17日。特别是8月16日的太阳耀斑造成电离层垂测站的频高图近四个小时内没有回波。     

临汾水准巨幅形变的位错理论模拟与异常性质判定

在假设临汾水准两次巨幅形变异常为断裂错动的情况下,基于矩形断层位错模型模拟了罗云山断裂（土门-峪里段）错动所引起的垂直形变场分布,并通过D-InSAR技术对研究区域内的地面形变场进行实测,分析结果表明：（1）断裂错动理论上可导致长轴与断裂走向平行的椭圆状变形区域,位于断裂上盘的区域中心变形量最大,变形量向外围逐渐衰减为零,两次错动导致的变形波及范围分别约为长轴18Km和26Km,短轴12Km和17Km,显著变形幅度分别约为1-3mm和4-14mm。（2）D-InSAR实测形变场显示两次异常期间研究区域内未发现与断裂走向一致的连续变形区域,仅在盆地内部存在可能由于过量开采地下水所导致的地面沉降,变形范围约为10-12mm和10-15mm。（3）实测形变场与理论形变场在变形区域和变形幅度上均不一致,说明断裂活动引起临汾水准巨幅形变的可能性不大,可能为断裂上盘的土层局部变形所致。（4）通过断层位错模型的理论模拟和D-InSAR技术的实际监测相结合可以有效地确定跨断层水准巨幅形变异常的性质,为重大水准异常核实提供科学依据。     

Langmuir probe measurements aboard the International Space Station

In the current work we describe the Langmuir Probe (LP) and its operation on board the International Space Station. This instrument is a part of the scientific complex “Ostonovka”. The main goal of the complex is to establish, on one hand how such big body as the International Space Station affects the ambient plasma and on the other how Space Weather factors influence the Station. The LP was designed and developed at BAS–SRTI. With this instrument we measure the thermal plasma parameters–electron temperature Te, electron and ion concentration, respectively Ne and Ni, and also the potential at the Station’s surface. The instrument is positioned at around 1.5 meters from the surface of the Station, at the Russian module “Zvezda”, located at the farthermost point of the Space Station, considering the velocity vector. The Multi- Purpose Laboratory (MLM) module is providing additional shielding for our instrument, from the oncoming plasma flow (with respect to the velocity vector). Measurements show that in this area, the plasma concentration is two orders of magnitude lower, in comparison with the unperturbed areas. The surface potential fluctuates between–3 and–25 volts with respect to the ambient plasma. Fast upsurges in the surface potential are detected when passing over the twilight zone and the Equatorial anomaly.     

Comparison of Brewer spectrophotometer ultraviolet data from similar latitudes in the Northern and Southern Hemisphere

This paper presents UV data recorded over 12 months in 2000/2001 at a southern hemisphere (Toowoomba) and similar latitude northern hemisphere (BigBend and Everglades) sites using Brewer Spectrophotometers. The peak daily erythemally weighted UV (DUV) at the Toowoomba site was 8.8% and 25% higher compared to that at the BigBend and Everglades sites, respectively. The Everglades site exposures are lower than the BigBend site exposures in summer and spring. This may be due to the higher cloud cover for the Everglades site. The summer DUV values between Toowoomba and BigBend are similar. In spring, the average DUV value is the greatest at BigBend compared to the other two sites. Results indicate that variability between the measurement sites is due to varying cloud and ozone, and possibly due to aerosol and airmass differences of each region. Of these different site-specific local atmospheric conditions, cloud was the main contributor to the differences in UV between the sites.     

A meteorological-based crop coefficient model for estimation of daily evapotranspiration

Estimation of daily evapotranspiration (ET) over cloudy regions highly desires models which rely on meteorological data only. Notwithstanding, the conventional crop coefficient (K_c) method requires detailed knowledge of geo/biophysical properties of the coupled land-vegetation system, precipitation, and soil moisture. Six Eddy Covariance (EC) towers in Iowa, California and New Hampshire of the USA (covering corn, soybeans, prairie, and deciduous forest) were selected. Investigation on 6 years (2007–2012) 15-min micrometeorological records of these sites revealed that there is an indubitable strong interaction between relative humidity (RH), reference ET (ET_o), and actual ET at different timescales. This allowed to bypass the need for the non-meteorological inputs and express K_c as a second-order polynomial function of RH and ET_o, the ambient regression evapotranspiration model (AREM). The coefficients of the empirical function are crop-specific and may require calibration over different soil types. The mean absolute percentage error (MAPE) of the regression against daily EC observations was 17% during the growing season, and 32% throughout the year with root mean square error (RMSE) of 0.74 mm day⁻¹ and coefficient of determination of 0.71. The model was fully operational (MAPE of 34% and RMSE of 0.82 mm day⁻¹) over the four Iowan sites based on inputs from local weather stations and NLDAS-2 forcing data of NASA. AREM was capable of capturing the dynamics of ET at 15-min and daily timescales irrespective of varying complexities associated with biophysical, geophysical and climatological states.     

Directional damage due to near-fault and site effects in the M6.4 Changureh–Avaj earthquake of 22 June 2002

The Changureh–Avaj earthquake (M = 6.4) occurred 220 km northwest of Tehran on June 22, 2002. According to the official report, 226 people were killed, 1300 injured and 33,000 houses were seriously damaged or collapsed. Two villages located in the near-fault region with a population more than 200 people were completely destroyed. The damage survey was conducted within 30 km of the epicenter. During damage investigation, an observable pattern of damage in toppled masonry and concrete block fences was recognized. The data of damaged fences were documented and analyzed to study the effect of direction and distance from the epicenter. From the 109 fences, 85 fences were built within 15° of either north or east, providing an opportunity to study the effect of orientation. The results of analysis revealed that the east–west oriented fences toppled 2.6 times more than those oriented north–south. More than 70% of toppled fences were oriented in east–west direction, with more falling towards the north than to the south. This preferred direction of damage for toppled fences was observed in all four quadrants about the epicenter and at distance up to 15 km. In the northern quadrants almost all toppled fences were oriented east–west. Two possibilities, namely, near-fault effect and 2D or 3D site response, are examined to find an explanation for the observed damage pattern at the sites. Since the preferred direction of damage inferred from toppled fences within 15 km of epicenter was found to be parallel to the direction of rupture propagation, the near-fault forwarded rupture directivity was investigated as the most possible reason for the observed phenomenon at the sites. However, there were no records of strong motions available in near-fault zone. Thus, the near-fault ground motions were theoretically simulated by using developed local source parameters and heterogeneous slip model. Next, the principal axes were calculated by using eigenvector analysis of simulated horizontal motions. The preferred direction of damage in over 90% of the sites is well predicted by the directional dependence of near-fault ground motion. Nevertheless, the preferred direction of damage in Avaj station, where the main shock was recorded, demonstrates totally different result from the one predicted by the source. The shear-wave polarization is investigated as an alternative reason at the sites. The polarization of motion is found to be the greatest at frequencies with peaks in maximized and H/V spectra, suggesting that directional motion is associated with local site and geologic conditions. The dominant direction of motion due to source mechanism and local site conditions was identified and compared with the preferred direction of damage observed at the sites. It is found that the near-fault source effects can strongly control the motion directionality and even dictate its dominant direction to the one caused by local geologic or site conditions. Finally, the outcome provides field evidence of directional damage due to near-fault effects and local site conditions. This may aid in predicting the directions of damaging earthquake motions, and serve as an important factor in the design of critical facilities.     

Frequency band-dependence of S-wave splitting in China mainland and its implications

Butterworth band-pass filter has been applied to S-wave data recorded at 8 stations in China mainland, and S-wave splitting at different frequency bands is analyzed. The results show that the delay time and the fast polarization directions of S-wave splitting depend upon the frequency bands. There is an absence of S-wave splitting at the station of Urumqi (WMQ) for the band of 0.1–0.2 Hz. With the frequency band broadening, the delay time of S-wave splitting decreases at the stations of Beijing (BJI), Enshi (ENH), Kunming (KMI) and Mudanjiang (MDJ); the fast polarization direction changes from westward to eastward at Enshi (ENH), and from eastward to westward at Hailaer (HIA). The variations of delay time with bands at Lanzhou (LZH) and Qiongzhong (QIZ) are similar, and there is a coherent trend of fast polarization directions at BJI, KMI and MDJ, respectively. Initial interpretations to the results of frequency band-dependence of S-wave splitting are also presented.     

S wave inelastic attenuation and site effect in the northern Tianshan area

In this paper,according to the relationship of observation spectrum with source spectrum,travel-path attenuationfactor and site effect,we use the digital seismic data of moderate-small earthquakes to invert the soft rock site ef-fect and S wave inelastic attenuation under the constraint of site effect,and determine the parameters of path andsite.The parameters obtained by this method exclude the topographic effect of seismic stations,and truly reflectthe seismic effect of free soft rock sites and the S wave inelastic attenuation in the studied region.The average softrock site effect is about 1.5 times in the frequency domain of 2～4 Hz and the S wave quality factor is obtained asQS=278 f0.346,which can be directly applied to the stochastic modeling of ground motions in the studied region.     

北天山地区S波非弹性衰减和场地效应研究

采用中小地震的数字观测资料,依据地震观测谱和震源谱、传播路径衰减因子及场地效应的关系式,在对场地效应约束的条件下,反演S波非弹性衰减和软基岩场地效应,确定研究区路径、 场地参数. 该方法确定的参数, 避免了台站地形效应的影响,真实地反映了研究区自由软基岩场地的地震效应和传播路径非弹性衰减的影响. 研究区的平均软基岩场地效应, 在2~4 Hz频率范围为1.5倍左右; S波品质因子为QS=278 f 0.346.这些参数可以直接用于研究区的地面运动随机模拟.