Surface Energy Balance Equation Research Articles

Application of a two source energy balance model coupled with satellite based soil moisture and thermal infrared data

Satellite retrievals of thermal infrared data from the Earth’s surface when combined with the surface energy balance equation are widely used to monitor land surface evapotranspiration (ET). Unfortunately thermal infrared based models using this approach have a systematic positive bias with ET during soil water stress conditions. The Two-source Energy Balance model using information on Soil Moisture as another key constraint (TSEB-SM) improves model performance and utility. Here, high resolution satellite soil moisture data from SMAP (Soil Moisture Active Passive) were used to provide soil water boundary conditions for the TSEB-SM model. This SMAP driven TSEB-SM approach was applied in the Heihe river basin in China across a wide range of soil moisture conditions using MODIS thermal infrared land surface temperature (LST) data. The ET estimates from TSEB-SM were validated using flux tower measurements over the main land cover types in the study area and compared with the results from the original TSEB model. The comparison showed that the TSEB-SM approach reduced the RMSE error in latent heat flux estimates by 5 % to 20 % at satellite overpass time, and TSEB-SM outperformed the original TSEB model in daily ET estimates (RMSE values of 1.0 mm/d versus 1.5 mm/d, respectively) across all validation sites. The magnitude of the TSEB-SM improvements were larger early and late in the growing season and in arid areas, consistent with soil moisture improving estimates of ET particularly under times of higher water stress. The use of SMAP satellite soil moisture data with the TSEB-SM model increased the reliability of ET estimation and provides an improved capacity for continuos monitoring of drought effects on the global water cycle.

Reevaluating the Surface Energy Balance and Soil Thermal Diffusion Equations in the Noah Multi-Parameterization (Noah-MP) Scheme

The Noah multi-parameterization (Noah-MP) scheme is one of several land surface schemes implemented in the Weather Research and Forecasting (WRF) model. Our simulations by the WRF model with the Noah-MP scheme show that surface air temperatures in the morning and evening tend to be higher and lower, respectively, than observed, and that the temperatures at an urban station with snow cover increase little from 0 ℃ even in the daytime. The former depends on surface energy balance in the skin layer and the latter results from snow cover assumed to be uniform over a grid cell. These weaknesses are improved by considering the partial transmission of the solar radiation through the skin layer to the soil layer, the heat capacity of the vegetation canopy, and a mixture of soil layers with and without snow cover. The present scheme will contribute to an improvement of the Noah-MP scheme.

A coupled ground heat flux–surface energy balance model of evaporation using thermal remote sensing observations

Abstract. One of the major undetermined problems in evaporation (ET) retrieval using thermal infrared remote sensing is the lack of a physically based ground heat flux (G) model and its integration within the surface energy balance (SEB) equation. Here, we present a novel approach based on coupling a thermal inertia (TI)-based mechanistic G model with an analytical surface energy balance model, Surface Temperature Initiated Closure (STIC, version STIC1.2). The coupled model is named STIC-TI. The model is driven by noon–night (13:30 and 01:30 local time) land surface temperature, surface albedo, and a vegetation index from MODIS Aqua in conjunction with a clear-sky net radiation sub-model and ancillary meteorological information. SEB flux estimates from STIC-TI were evaluated with respect to the in situ fluxes from eddy covariance measurements in diverse ecosystems of contrasting aridity in both the Northern Hemisphere and Southern Hemisphere. Sensitivity analysis revealed substantial sensitivity of STIC-TI-derived fluxes due to the land surface temperature uncertainty. An evaluation of noontime G (Gi) estimates showed 12 %–21 % error across six flux tower sites, and a comparison between STIC-TI versus empirical G models also revealed the substantially better performance of the former. While the instantaneous noontime net radiation (RNi) and latent heat flux (LEi) were overestimated (15 % and 25 %), sensible heat flux (Hi) was underestimated (22 %). Overestimation (underestimation) of LEi (Hi) was associated with the overestimation of net available energy (RNi−Gi) and use of unclosed surface energy balance flux measurements in LEi (Hi) validation. The mean percent deviations in Gi and Hi estimates were found to be strongly correlated with satellite day–night view angle difference in parabolic and linear pattern, and a relatively weak correlation was found between day–night view angle difference versus LEi deviation. Findings from this parameter-sparse coupled G–ET model can make a valuable contribution to mapping and monitoring the spatiotemporal variability of ecosystem water stress and evaporation using noon–night thermal infrared observations from future Earth observation satellite missions such as TRISHNA, LSTM, and SBG.

A Possible Reconciliation between Eddy Covariance Fluxes and Surface Energy Balance Closure

At the surface of the earth, the available radiative energy Rn is distributed between the ground heat flux and the sensible and latent heat fluxes according to the surface energy balance (SEB) equation. In the past decades, most attempts to measure the individual terms of this equation have revealed a non-closure problem, regardless of the site of observation or period of the year. Today, no definitive answer has been provided to this question. In general, it is suspected that the sensible and latent heat fluxes (H and LvE, respectively) that are calculated with the eddy-covariance technique are underestimated. This paper suggests two additional terms that should be considered in the SEB equation, which are based on thermodynamic considerations. They are directly related to H and LvE and appear to be interesting candidates for explaining (at least in part) the non-closure of the SEB. The distribution of the correction between H and LvE varies as a function of the Bowen ratio B. The correction relative to H is dominant for values of B that are greater than 0.2 and represents more than 80% of the total correction for values greater than unity. The impact of these corrections on the SEB closure was tested on a large set of observations from 24 FLUXNET sites around the world with different vegetation types. The closure defect, which is about 17% in the original dataset, is reduced to about 3% with the proposed corrections.

The soil heat flux sensor functioning checks, imbalances' origins, and forgotten energies

Abstract. Soil heat flux is an important component of the surface energy balance (SEB) equation. Measuring it requires an indirect measurement. Every used technique may present some possible errors tied with the utilized specific technique, soil inhomogeneities, or physical phenomena such as latent heat conversion beneath the plates, especially in desiccation cracking soil or vertisol. The installation place may also induce imbalances. Finally, some errors resulting from the physical sensor presence, vegetation presence, or soil inhomogeneities may occur and are not avoidable. For all these reasons it is important to check the validity of the measurements. A quick and easy way is to integrate results over 1 year. By consideration of the inert core internal energy conservation law, it is shown that the corresponding integration should be close to zero after a necessary geothermal heat efflux subtraction. However, below-plate evaporation and vegetation-absorbed water or rainwater infiltration may also contribute to the observed short-scale and/or long-scale imbalance generating convective heat fluxes not sensed by the heat flux sensors. Another energy source is usually not included in the SEB equation: rainfall or irrigation. Yet its importance for short- and long-term integration is notable. As an example, the most used sensor, soil heat flux plates (SHFPs), is given.

Explicit modeling of pebble temperature in the porous-media model for pebble-bed reactors

In this study, a multiscale model has been developed to include an explicit pebble-temperature model nested in the porous-media model for pebble-bed reactor applications. The multiscale solid-phase energy balance model, including the pebble surface energy balance equation and an explicit modeling of pebble temperature, can predict the macroscopic (pebble bed) and microscopic (pebble) temperature distributions under both steady-state and transient conditions. The proposed multiscale model is solved in a fully coupled manner using the Newton-Krylov method, and therefore iterations between the macroscopic (pebble-bed-scale) and microscopic (pebble-scale) model are avoided. Extensive code verifications, validation, and demonstrations have been performed for this newly developed model. By explicitly modeling pebble temperatures, this new model addresses a major deficiency of the basic porous-media model, which assumes homogeneous solid-phase temperature and is not appropriate for pebble-bed reactor design and safety analyses.

Energy-Based Approaches in Estimating Actual Evapotranspiration Focusing on Land Surface Temperature: A Review of Methods, Concepts, and Challenges

The surface energy balance (SEB) model is a physically based approach in which aerodynamic principles and bulk transfer theory are used to estimate actual evapotranspiration. A wide range of different methods have been developed to parameterize the SEB equation; however, few studies addressed solutions to the SEB considering the land surface temperature (LST). Therefore, in the current review, a clear and comprehensive classification is provided for energy-based approaches considering the key role of LST in solving the energy budget. In this regard, three general approaches are presented using LSTs derived by climate and land surface models (LSMs), satellite-based data, and energy balance closure. In addition, this review surveys the concepts, required inputs, and assumptions of energy-based LSMs and SEB algorithms in detail. The limitations and challenges of aforementioned approaches including land surface temperature, surface energy imbalance, and calculation of surface and aerodynamic resistance network are also assessed. According to the results, since the accuracy of resulting LSTs are affected by weather conditions, surface energy closure, and use of vegetation/meteorological information, all approaches are faced with uncertainties in determining ET. In addition, for further study, an interactive evaluation of water and energy conservation laws is recommended to improve the ET estimation accuracy.

Temporal and Spatial Variation of Anthropogenic Heat in the Central Urban Area: A Case Study of Guangzhou, China

The urban heat island effect caused by the rapid increase in urban anthropogenic heat has gradually become an important factor affecting the living environment of urban residents. Studying the temporal and spatial variation characteristics of urban anthropogenic heat is of great significance for urban planning and urban ecological service systems. In this study, the urban anthropogenic heat flux (AHF) in 2004, 2009, 2014, and 2020 in the central urban area of Guangzhou was retrieved based on Landsat data and the surface energy balance equation, and the temporal and spatial characteristics of different types of anthropogenic heat were explored by combining the transfer matrix and the migration of the gravity center. The results showed that: (1) The overall change trend of anthropogenic heat in the central urban area of Guangzhou was enhanced, and the degree of enhancement was related to the type of urban functional land. (2) Different types of anthropogenic heat had different characteristics in terms of area expansion and spatial changes. Low-value anthropogenic heat (zero-AHF zone, low-AHF zone, medium-AHF zone) changed drastically in terms of area expansion. High-value anthropogenic heat (medium-AHF zone, high-AHF zone) changed more drastically in space. The increase in urban population, rapid economic development, and increased industrial production activities have stimulated the emission of anthropogenic heat, which has a positive impact on the intensity of anthropogenic heat.

Ablation behavior studies of charring materials with different thickness and heat flux intensity

Surface ablation and in-depth temperature distribution of the charring material are the key properties of the thermal protection system in re-entry vehicles subjected to aerodynamic heating. To investigate the factors affecting the ablation performance of charring materials, the influence of decomposition reaction and surface recession on ablation was added to the heat conduction and surface energy balance equation, to comprehend the phenomenon of surface material removal. The model developed in this study was verified by comparing with results from traditional finite difference method. Furthermore, the effects of external constant heat flux, initial material thickness, and heating time on ablation were determined and discussed on temperature, surface recession, and density distribution. The change trend of the external heat flux significantly affects the change trend of the surface temperature. The material thickness and heating time have great influence on the bottom temperature. This paper contributes to the understanding of the heat transfer and ablation of the charring materials, thereby providing a basis for the selection of the thermal protection material for re-entry vehicles.

Conditioning point and gridded weather data under aridity conditions for calculation of reference evapotranspiration

Meteorological data are often collected in dry, desert regions where the local environments exhibit effects of aridity caused by the lack of evapotranspiration (ET). In contrast, the standard reference ET (ETo) calculations of FAO56 and ASCE assume that the surfaces underlying collected weather data are well-watered so that near-surface meteorological measurements reflect the cooling and humidifying effects of an evaporating surface. In this study, we develop a weather data conditioning process and algorithms to adjust for biases in meteorological data that exhibit aridity effects. The conditioning process is intended to adjust the weather data to better exhibit characteristics of data collected over a well-watered vegetated surface prior to use of the data to estimate reference ET. The procedure involves the extrapolation of air temperature, vapor pressure, and wind speed profiles to and from a regional blending height using standard surface energy balance equations and flux-profile relationships and employing ET estimated for the ambient, dry conditions of an arid weather station and reference ET that should co-exist with weather measurements used to calculation reference ET. Example applications are given with 24-hour weather data and hourly weather data in Idaho and Nevada. Results indicate that reference ETo can be overstated by as much as 25% in southern Idaho and 8% in eastern Nevada. The methodology is intended to be transferrable to other regions and climates and is self-aware of the need for conditioning of weather data according to differences in ambient ET and the reference ET estimates.

Attribution of Land‐Use/Land‐Cover Change Induced Surface Temperature Anomaly: How Accurate Is the First‐Order Taylor Series Expansion?

AbstractLand surface temperature (LST) responds to land‐use/land‐cover change (LULCC), which modifies surface properties that control the surface energy balance (SEB). Quantifying changes in LST due to individual perturbations caused by LULCC is an attribution problem. Most attribution methods are based on the first‐order Taylor series expansion (FOTSE) of a linearized SEB equation. The accuracy of these methods is affected by the use of FOTSE at two places. The first is to linearize the SEB equation and to obtain an analytical solution for LST (the LST model), and the second is to obtain LST changes as the linear sum of concurrent changes in multiple factors (the attribution model). In this study, we systematically assess the importance of non‐linear effects lost in these linearization processes using the second‐order Taylor series expansion (SOTSE). Results show that while the SOTSE LST model outperforms the FOTSE LST model, the order of Taylor series expansion in the LST model does not significantly influence the attribution of LST changes. However, the SOTSE attribution model is considerably more accurate than the FOTSE attribution model, especially when the magnitude of perturbations is large. Results suggest that contributions from higher‐order and cross‐order terms in the attribution model can be as large as 50%. Sensitivity analysis further shows that non‐linear effects associated with changing surface resistance for LULCC scenarios with large perturbations (e.g., deforestation and urbanization) are particularly strong. In conclusion, we recommend using the FOTSE LST model and the SOTSE attribution model.

A Scheme to Estimate Diurnal Cycle of Evapotranspiration from Geostationary Meteorological Satellite Observations

The diurnal cycle of evapotranspiration (ET) is significant in studying the dynamics of land–atmosphere interactions. The diurnal ET cycle can be considered as an indicator of dry/wet surface conditions. However, the accuracy of current models in estimating the diurnal ET cycle is generally low. This study developed an improved scheme to estimate the diurnal cycle of ET by solving the surface energy balance equation combined with simplified parameterization, with daily ET as the constraint. Meteosat Second Generation (MSG) land surface temperature, and longwave and shortwave radiation products were the primary inputs. Daily ET was from the remote sensing-based ETMonitor model. The estimated instantaneous (30 min) ET from the improved scheme outperformed the official MSG instantaneous ET product when compared with in situ half-hourly measurements at 35 flux sites from the FLUXNET2015 dataset, and was also comparable with European Center for Medium-Range Weather Forecasts (ECMWF) ERA5 ET data, with an R2 of 0.617 and root mean square error (RMSE) of 65.8 W/m2 for the improved scheme. Results were largely improved compared with those without daily ET as the constraint. The improved method was stable for the estimation of ET’s diurnal cycle at the similar atmospheric conditions and the accuracy was comparative at different land cover surfaces. Errors in the input variables and the simplification of surface heat flux parameterization affected surface energy balance closure, which can lead to instability of the solution of constants in the simplified parameterization and further to the uncertainty of ET’s diurnal cycle estimation. Measurement errors, different source areas in measured variables, and inconsistent spatial representativeness between remote sensing and site measurements also impacted the evaluation.

The Microclimatic Effects of Ecological Restoration in Brownfield based on Remote Sensing Monitoring: The Case Studies of Landfills in China

In the acceleration of industrialization and urbanization, brownfield is an important resource for land regeneration and restoration targeting to recover its ecosystem function. Landfills, as a type of brownfield distributed in the highly populated areas, occupy massive land resources. The ecological restoration of landfills becomes an engineering approach to achieve multiple effects of society, environment, and economy. This paper aims to monitor and assess the restoration microclimatic effects of landfills restoration in China with remote sensing data and techniques. We selected representative landfill restoration projects, including Nanhaizi Park in Beijing, Nanhu Park in Tangshan, and Tianziling Park in Hangzhou, as the study cases. Using the Landsat imagery, the scenes of the pre-restoration, mid-restoration, and post-restoration were retrieved, and the surface energy balance equation was applied to calculate normalized difference vegetation index (NDVI), land surface temperature (Ts), and evapotranspiration (ET), representing vegetation conditions and hydro-heat microclimate conditions. The study areas are divided into four subzones and extracted the calculated values for statistics and comparison. We defined an indicator of restoration intensity (RI) using the different subzones to the outer contour distance radius and restoration phases to evaluate the spatial-temporal restoration degrees. The spatial pattern dynamics was displayed in the urbanization context in the cases of Beijing and Tangshan. We examined and quantified the relations between RI and the key indicators, NDVI, Ts, and ET. The overall results revealed that with higher restoration intensity, NDVI and ET became higher, and Ts became lower. It suggested that the ecological restoration on the landfills brought better vegetation, cooling, and humidification effects for the microclimatic environment. Our research has the implications for monitoring and assessing the climatic effects of ecological restoration in the brownfield regeneration in a macroscopic and ecosystem perspective.

Surface eddy fluxes and friction velocity estimates taking measurements at the canopy top

Agricultural engineers, crop physiologists and hydrologists are often forced to deploy instrumentation close to the canopy top to estimate surface eddy fluxes. This is a widely recognized problem either at farm-level or research-level. The eddy covariance (EC) method is grounded on hypothesis, simplifications and relationships valid in the inertial sublayer and alternative methods may require either calibration or inputs that are not commonly available. The present study enables a method that combines similarity, transilient and surface renewal theories in conjunction with the analysis of small eddies (Surface renewal of small eddies, SRSE, method) to estimate the friction velocity and surface fluxes of different scalars (sensible heat, latent heat and carbon dioxide) taking measurements at the canopy top. SRSE minimizes estimation of canopy parameters (only the zero-plane displacement is involved), allows implementing a primary flux quality control and to guide instrumentation deployment. For a mature maize crop, SRSE and EC surface energy balances indicated that EC was slightly more reliable than SRSE during daytime. For unstable cases, the normalized mean absolute error (MAE) to the available net surface energy (ANSE), MAE/ANSE, obtained by the EC and SRSE methods were 9% and 13 %, respectively. For stable cases during the day, 10 % and 11 %, respectively. For stable cases at night SRSE performed better than EC, MAE/ANSE were 23 % and 16 %, respectively. Regardless of the half-hourly eddy flux (including the friction velocity), the EC and SRSE were highly correlated (the minimum coefficient of determination was 0.91) and, in average (for all data) flux of scalars nearly matched including water-use-efficiency. To avoid acquisition of expensive and stringent instrumentation, the closure of the surface energy balance equation was forced to derive affordable approaches to estimate the latent heat flux for different stability cases.

Variational Assimilation of the Impervious Surfaces Temperature

Impervious surface temperature is a key parameter in impervious surface energy balance. Urban canopy models are now widely used to simulate impervious surface temperatures, but the physical assimilation method for the urban canopy model is still under development and the use of high temporal resolution observation data are limited. In this paper, a physical assimilation method was used to improve the simulation of the impervious surface temperature for the first time. A variational assimilation method was developed and coupled with the integrated urban land model, using the impervious surface energy balance equation as the adjoint physical constraint. The results showed that when the observed impervious surface temperature data of every timestep were assimilated into the integrated urban land model, the bias of the impervious surface temperature was reduced about 86 %. For the operational run, the observed data were assimilated twice per day, and the bias of the impervious surface temperature was reduced by about 78%.

Competition mechanism during oxidation of pyrolysis gases in nonequilibrium boundary layer on thermal protection performance of charring composites

AbstractThe influence of gas‐phase reactions in chemical nonequilibrium boundary layer on the thermal protection performance of charring materials has been analyzed in this work. These reactions are exothermic and compose of oxidation between the multicomponent pyrolysis gases and the oxidative gas components in the chemical nonequilibrium hypersonic boundary layer. During the reactions, the consumption amount of oxidizing components competes with the amount of exothermicity of gas‐phase oxidation reactions. We built the physical and mathematical models for the coupling of thermal and ablative responses of material, hypersonic flow response, and chemical response in chemical nonequilibrium boundary layer. Moreover, a new surface energy balance equation is built for bridging the multifield coupling mathematical models. In addition, the exothermic heat produced from the oxidation reactions of multicomponent pyrolysis gases is taken into consideration. The numerical example for the fluid‐chemical‐thermal‐ablative coupled behavior for a charring ablator and its environment for an Apollo‐like reentry vehicle in chemical nonequilibrium is simulated by using our two‐way coupling computer codes. Numerical results indicate that the oxidation of multicomponent pyrolysis gases in chemical nonequilibrium boundary layer weakens the mass ablation of surface char. Although the pyrolysis gas in the nonequilibrium boundary layer oxidizes and releases heat, the weakening effect of oxygen consumption on the surface is much more significant, especially when the cold heat flux is smaller.

The impact of building configurations and anthropogenic heat on daily urban air temperature cycles

Urban air temperature reflects the impact of urbanization on thermal and dynamics of urban climate. To understand the physical mechanism of building configurations and anthropogenic heat on daily urban air temperature cycles, an improved lumped urban air temperature model was provided. The surface energy balance equation for the improved and previous lumped urban air temperature model were compared. The effective depth of thermal mass and sub-surface temperature of urban surfaces in the previous model can be determined, which are usually chosen from model studies. These two parameters have a significant impact on the thermal storage. The models were evaluated and applied to the city of Hong Kong. Thermal storage is shown to have significant impact on the amplitude and phase term of daily air temperature cycle. Moreover, the building configurations can affect the solar radiation gain and redistribution in the sub-facets, which indirectly influenced the urban air temperature. The results show that the ventilation rate, building height and plan area ratio play important roles on daily cycle of urban air temperature, while the anthropogenic heat plays a less significant role. The main distinction of the improved model is its simplicity and less computation cost for practice use for engineers and urban planners. Two important parameters are emphasized, relative convective heat transfer number, λ, and time constant, τ. The two parameters provide some insights on how to control the urban thermal environment in an engineering way.

Comparison of a stand-alone surface renewal method to weighing lysimetry and eddy covariance for determining vineyard evapotranspiration and vine water stress

Surface renewal (SR) is a biometeorological technique that uses high-frequency air temperature measurements above a plant canopy to estimate sensible heat flux. The sensible heat flux is then used to estimate latent heat flux as the residual of a surface energy balance equation. SR previously relied on calibration against other methods (e.g., eddy covariance) to obtain accurate measurements of sensible heat flux, and this need for calibration limited the use of SR to research applications. Our group recently showed that compensating for the frequency response characteristics of SR thermocouples causes the calibration factor to converge near the theoretically predicted value of 0.5 (Shapland et al., Agric For Meteorol 189:36–47, 2014). This led to the development of an inexpensive, stand-alone SR system to measure sensible heat flux without the need for calibration, and here we evaluated the SR system in a mature vineyard containing a weighing lysimeter. Vineyard evapotranspiration (ET) measured with SR was strongly and positively correlated with that from the lysimeter, eddy covariance, and a soil water budget approach. ET measured with the various techniques responded similarly to changes in the microclimatic conditions (i.e., day to day variability) and when water was withheld from the entire vineyard for an extended period. A stress index, calculated using reference and actual ET from SR and lysimetry, was correlated to leaf water potential, stomatal conductance, and volumetric soil water content measurements, but some of these relationships were more variable than others. Our results suggest that the new SR method could potentially be used as a low-cost tool to provide growers with field-specific estimates of crop water use and stress for irrigation management in vineyards.

NEW METHODOLOGY FOR ESTIMATING EVAPOTRANSPIRATION AND UPDATING CROP COEFFICIENT FOR RICE IN EGYPT BY SURFACE RENEWAL METHOD

Improving irrigation management needs accurate information and tools to estimate accurate crop-water requirements. At the national level, one of the biggest deficiencies in water-use planning is a lack of continues and updated data sets of evapotranspiration and accurate crop coefficient values. The aim of this study is to evaluate locally, the “Surface Renewal (SR)” method, as an energy balance direct method to estimate crop evapotranspiration (ETc), and upgrade crop coefficients (Kc) of rice crop in Egypt. SR station was installed in the “agricultural production sector” farm in Moshtouhor, at Kaliobia governorate, in order to collect high resolution field observations of energy balance factors of paddy rice field. The data was used to calculate the actual crop evapotranspiration (ETc) and crop coefficient(Kc) of the crop by using the SR method, and comparing the result with the standard values recommended by FAO. The overall RMSE between the ETc-SR and the ETc-FAO was 0.92 mm/day. The error was at the highest level at the initial-season stage, and slightly decreased to reach to 0.48 mm/day by the end of the season. The average value of Kc-SR was 1.17, 1.13 and 1.14 at the initial-season, mid-season and late season stages, respectively. The RMSE between the Kc-SR and the Kc-FAO values were 0.17, 0.10 and 0.03 at the initial-season, the mid-season, and the late-season stages, respectively. The combination of the SR procedure and the simplified surface energy balance equation appears being an affordable alternative to be considered for estimating water use in agriculture. In the other hand, the SR method still need several evaluations, calibration work, in order to be used significantly to upgrade the Kc value for the local crop cultivars in Egypt.

Effectively modeling surface temperature and evaluating mean radiant temperature in tropical outdoor industrial environments

Radiant heat gain severely endangers thermal comfort and dramatically increases building energy consumptions in a tropical outdoor urban environment. To rapidly evaluate outdoor thermal features, this paper presents a three-dimensional integrated numerical model to assess building surface temperature and mean radiant temperature (MRT) in typical outdoor industrial environments of Singapore. For proper accounting of solar irradiance and radiant heat fluxes, Perez all-weather model and finite volume discrete ordinates method (fvDOM) are integrated into numerical code. Under the climate conditions of Singapore, i.e., light wind and intense solar irradiance, the model adopts a daily-average convection coefficient to simplify air dynamics to solve the surface energy balance equation so that the model efficiency can be significantly improved. Surface thermal load computed using the model has been validated by the on-site measurement for a contemporary and a matured industrial building on two sunny days. By comparing simulated and measured results, the corresponding coefficient of determination (R2) and the refined index of agreement (RIA) are respectively > 0.99 and > 0.8 to indicate that the model agrees well with the measurement. Also, the model is used to predict the MRT map around the industrial environment and to demonstrate that tree shading reduces mean MRT of 6.3 °C for daily-average and 13.29 °C at noon in a street canyon under a 25% greenery coverage ratio.