The Spatial Sensitivity Analysis of Evapotranspiration using Penman-Monteith Method at Grid Scale

The need to allocate the existing water in a sustainable manner, even with the projected population growth, has made to assess the consumptive use or evapotranspiration (ET), which determines the irrigation demand. As underscored in the literature, Penman-Monteith method which is a combination of aerodynamic and energy balance method is widely used and accepted as the method of estimation of ET. However, the application of Penman-Monteith relies on many climate parameters such as relative humidity, solar radiation, temperature, and wind speed. Therefore, there exists a need to determine the parameters that are most sensitive and correlated with dependent variable (i.e., ET), to strengthen the knowledge base. However, the sensitivity of ET using Penman-Monteith is oftentimes estimated using meteorological data from climate stations. Such estimation of sensitivity may vary spatially and thus there exists a need to estimate sensitivity of ET spatially. Thus, in this paper, based on One-AT-A-Time (OAT) method, a spatial sensitivity tool that can geographically encompass all the best available climate datasets to produce ET and its sensitivity at different spatial scales is developed. The spatial tool is developed as a Python toolbox in ArcGIS using Python, an open source programming language, and the ArcPy site-package of ArcGIS. The developed spatial tool is demonstrated using the meteorological data from Automated Weather Data Network in Nebraska in 2010. To summarize the outcome of the sensitivity analysis using OAT method, sensitivity indices are developed for each raster cell. The demonstration of the tool shows that, among the considered parameters, the computed ET using Penman-Monteith is highly sensitive to solar radiation followed by temperature for the state of Nebraska, as depicted by the sensitivity index. The computed sensitivity index of wind speed and the relative humidity are not that significant compared to the sensitivity index of solar radiation and temperature.

A new non-linear vortex lattice method:Applications to wing aerodynamic optimizations

This paper presents a new non-linear formulation of the classical Vortex Lattice Method （VLM） approach for calculating the aerodynamic properties of lifting surfaces. The method accounts for the effects of viscosity, and due to its low computational cost, it represents a very good tool to perform rapid and accurate wing design and optimization procedures. The mathematical model is constructed by using two-dimensional viscous analyses of the wing span-wise sections, according to strip theory, and then coupling the strip viscous forces with the forces generated by the vortex rings distributed on the wing camber surface, calculated with a fully three-dimensional vortex lifting law. The numerical results obtained with the proposed method are validated with experimental data and show good agreement in predicting both the lift and pitching moment, as well as in predicting the wing drag. The method is applied to modifying the wing of an Unmanned Aerial System to increase its aerodynamic efficiency and to calculate the drag reductions obtained by an upper surface morphing technique for an adaptable regional aircraft wing.

Discrepancy and Applicability of Various Similarity Functions in Flux Calculations Under Stable Conditions

Based on data obtained during the Hualhe River Basin Experiment （HUBEX） in 1999, this study intends to detect the quantitative discrepancies in the momentum （τ0）, sensible heat （H0） and latent heat （E0） fluxes among six sets of similarity functions with the aerodynamic method. It also aims to clarify the applicability of the functions under stable conditions. The relative discrepancy was studied with the normalized transfer coefficients for τ0, H0 and E0, namely CD, CH and CQ, respectively. Except for one set of functions that adopted a rather small von Kármán＇s constant （0.365）, the relative discrepancy in τ0 among the other functions was less than 10%, while that in H0（E0） sometimes reached 25% when the bulk Richardson number （R/B） was less than 0.07. The absolute discrepancy in the fluxes was studied with statistical computations. Among the six sets of functions, the discrepancy in τ0, H0 and E0 sometimes reached 0.03 kg m^-1 s^-2, 4 W m^-2 and 10 W m^-2, respectively, and the discrepancy in the energy balance ratio sometimes exceeded 0.1. Furthermore, when RiB exceeded the critical value （Ric） for a specific set of functions, no fluxes could be derived with the functions. It is therefore suggested that RiB be compared with Ric before computing the fluxes if RiB is less than Ric. Finally, two sets of nonlinear similarity functions are recommended, due to their unlimited applicability in terms of RiB.

A Spatial Evapotranspiration Tool at Grid Scale

The drastic decline in groundwater table and many other detrimental effects in meeting irrigation demand, and the projected population growth have force to evaluate consumptive use or evapo-transpiration (ET), the rate of liquid water transformation to vapor from open water, bare soil, and vegetation, which determines the irrigation demand. As underscored in the literature, Pen-man-Monteith method which is based on aerodynamic and energy balance method is widely used and accepted as the method of estimation of ET. However, the estimation of ET is oftentimes carried out using meteorological data from climate stations. Therefore, such estimation of ET may vary spatially and thus there exists a need to estimate ET spatially at different spatial or grid scales/resolutions. Thus, in this paper, a spatial tool that can geographically encompass all the best available climate datasets to produce ET at different spatial scales is developed. The spatial tool is developed as a Python toolbox in ArcGIS using Python, an open source programming language, and the ArcPy site-package of ArcGIS. The developed spatial tool is demonstrated using the meteorological data from Automated Weather Data Network in Nebraska in 2010.

Measurement of HONO flux using the aerodynamic gradient method over an agricultural field in the Huaihe River Basin,China

To investigate nitrous acid(HONO)levels and potential HONO sources above crop rotation fields.The HONO fluxes were measured by the aerodynamic gradient(AG)method from 14 December 2019 to 2 January 2020 over an agricultural field in the Huaihe River Basin.The ambient HONO levels were measured at two different heights(0.15 and 1.5 m),showing a typical diurnal cycle with low daytime levels and high nighttime levels.The upward HONO fluxes were mostly observed during the day,whereas deposition dominated at night.The diurnal variation of HONO flux followed solar radiation,with a noontime maximum of 0.2 nmol/(m^(2)·sec).The average upward HONO flux of 0.06±0.17 nmol/(m^(2)·sec)indicated that the agricultural field was a net source for atmospheric HONO.The higher HONO/NO_(2)ratio and NO_(2)-to-HONO conversion rate close to the surface suggested that nocturnal HONO was formed and released near the ground.The unknown HONO source was derived from the daytime HONO budget analysis,with an average strength of 0.31 ppbV/hr at noontime.The surface HONO flux,which was highly correlated with the photolysis frequency J(NO_(2))(R^(2)=0.925)and the product of J(NO_(2))×NO_(2)(R^(2)=0.840),accounted for∼23%of unknown daytime HONO source.The significant correlation between HONO fluxes and J(NO_(2))suggests a light-driven HONO formation mechanism responsible for the surface HONO flux during daytime.

Fabrication and luminescence of highly transparent C12A7:Tb^(3+)glass-ceramics via in-situ crystallization from aerodynamic levitation processed glasses

Rare earth doped 12CaO·7Al_(2)O_(3)(C12A7)glass-ceramics are one of attractive photonic materials due to their high transparency,high luminescent efficiency and eco-friendly nature.A series of C12A7 glasses with different Tb^(3+)doping concentrations was prepared by aerodynamic levitation method.The C12A7:Tb glass-ceramics were obtained via in-situ growth from the glasses with the identical chemical composition at 800℃.The microstructure observation demonstrates that the elemental distributions of Ca and Al are homogeneous in the glass-ceramics and the grain size of C12A7 is 4-70 nm.The in-line transmittance of glass-ceramics reaches as high as 82%at 1500 nm.The emission spectra of the C12A7:Tb glass-ceramics present characteristic Tb^(3+)emission peaks at 486 nm(^(5)D_(4)→^(7)F_6),541 nm(^(5)D_(4)→^(7)F_(5)),585 nm(^(5)D_(4)→^(7)F_(4))and 621 nm(^(5)D_(4)→^(7)F_(3)).The photolumine scence lifetime of C12A7:0.3%Tb glass-ceramic is 1.9 ms.Compared with the emission intensity of the glasses,that of the glass-ceramics increases due to the reducing in concentration of oxygen vacancy associated with network forming(NWF)cations.The highly transparent C12A7:Tb glass-ceramics may be a promising candidate for green light source in solid state lighting.

Aerodynamic design of tractor propeller for high-performance distributed electric propulsion aircraft

Aiming to maximize the aerodynamic performance of the Distributed Electric Propulsion(DEP)aircraft,a hybrid design framework which focuses on the aerodynamic performance of the propeller/wing integration has been developed and validated numerically.Variable-fidelity modelling for propeller aerodynamics has been used to achieve computational efficiency with reasonable accuracy.By optimizing the aerodynamic loading distributions on the tractor propeller disk,the induced slipstream is redistributed into a form that is beneficial for the wing downstream,based on which the propeller blade geometry is generated through a rapid inversed design procedure.As compared with the Minimum Induced Loss(MIL)propeller at a specified thrust level,significant improvements of both the lift-to-drag ratio of the wing and the propeller/wing integrated aerodynamic efficiency is achieved,which shows great promise to deliver aerodynamic benefits for the wing within the propeller slipstream without any additional devices.

A second-order numerical method for elliptic equations with singular sources using local flter

The presence of Dirac delta function in differential equation can lead to a discontinuity,which may degrade the accuracy of related numerical methods.To improve the accuracy,a secondorder numerical method for elliptic equations with singular sources is introduced by employing a local kernel flter.In this method,the discontinuous equation is convoluted with the kernel function to obtain a more regular one.Then the original equation is replaced by this fltered equation around the singular points,to obtain discrete numerical form.The unchanged equations at the other points are discretized by using a central difference scheme.1D and 2D examples are carried out to validate the correctness and accuracy of the present method.The results show that a second-order of accuracy can be obtained in the fltering framework with an appropriate integration rule.Furthermore,the present method does not need any jump condition,and also has extremely simple form that can be easily extended to high dimensional cases and complex geometry.

RADIATION BALANCE AND TURBULENT FLUX CHARACTERISTICS OVER MIZUHO STATION IN ANTARCTICA

In this paper,by using measurements in micrometeorology and radiation balance in the surface layer(Yamanouchi et al.,1981;Wada et al.,1981;Ishikawa et al.,1982;Ohata et al.,1983),we have analyzed the diurnal and annual varia- tion characteristics of radiation balance in spring,summer,autumn and winter,and calculated the momentum flux and sensible heat flux with the aerodynamic method and profile gradient alternate method in different seasons.We have also obtained the diurnal variation characters of the latent heat flux from the equation for energy balance.The results from the calculation are compared.Finally,the relationship between the turbulent heat and momentum exchange coefficient and the diurnal variation of the Richardson number is discussed.

SURFACE IMBALANCE ENERGY CALCULATED AND ANALYZED WITH THE DATA OF EBEX-2000

Mainly.three methods have been developed to calculate turbulence heat flux.They are eddy covariance method,Bowen ratio/energy balance method and aerodynamic method.In this paper, all the three methods have been used to calculate sensible heat flux,latent heat flux and imbalance energy near the surface with the experiment data of EBEX-2000.Then comparisons of the three methods and some possible explanations of the surface imbalance energy are given.

Studies on aeroservoelasticity semi-physical simulation test for missiles

Missiles may be damaged when aeroservoelastic problem occurs,which is caused by the interaction of structure flexibility and flight control system.Because of the limit of wind tunnel test condition,numerical methods are mostly used in previous aeroservoelastic studies.However,series of assumptions and simplification on structures,aerodynamics and flight control systems are unavoidably introduced,and various nonlinear factors are also ignored,therefore,they result in considerable errors.A novel method called aeroservoelasticity semi-physical simulation test is proposed in this paper,which takes the flexible missile with control system as the test object.Vibration signals at several locations of the missile are measured by accelerometers,then corresponding unsteady aerodynamics is computed based on the fact that airflow at high Mach is nearly quasi-steady,and finally unsteady aerodynamics is exerted simultaneously by shakers at certain locations of the missile.The aeroservoelasticity semi-physical simulation test system can be constructed after the control system is closed.Open loop transfer function test and closed loop stability test are carried out in sequence.The test principle and method proposed in this paper are verified by the concordance between the results of numerical simulation and experiment.