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Vehicle-oriented transportation has been dominating road design for decades and worsening the urban outdoor thermal environment. Introducing the concept of human-oriented design in road reconstruction, this study considered road orientation, number of planting strips, and leaf area index (LAI) of trees when developing alternative road structures that aims to provide pedestrians a more satisfying walking experience. The ENVI-met V4 model, was used to simulate the thermal environment of sidewalks within the scenarios. Results demonstrated that road orientation had significant but time-varied effects on mean radiant temperature (Tmrt) and physiological equivalent temperature (PET). Two Tmrt and PET peaks were noticed in East-West (EW) oriented roads; but only one peak was found in North-South (NS) roads due to that the aisle buildings on NS roads shaded sidewalks and reduced the solar radiation received in the morning. Changing tree’s LAI from low to high on EW and NS roads can reduce the mean Tmrt by 5.5 and 3.0 °C, and the mean PET by 3.2 and 1.7 °C, respectively. Simulation results also showed that adding one more planting strip in the middle of roads did not reduce the mean Tmrt (all cases less than 1.7 °C) and mean PET (all cases less than 1.2 °C) much. A significant synergistic cooling effect from road orientation, number of planting strips, and LAI of trees on the sidewalks’ Tmrt and PET was observed. Thus, the number of planting strips and LAI of trees could be more precisely applied while considering road orientation. These results provide quantitative and alternative information for designers to create a better walking experience for pedestrians.
Bau-Show Lin; Yin-Hua Cho; Cheng-I Hsieh. Study of the thermal environment of sidewalks within varied urban road structures. Urban Forestry & Urban Greening 2021, 62, 127137 .
AMA StyleBau-Show Lin, Yin-Hua Cho, Cheng-I Hsieh. Study of the thermal environment of sidewalks within varied urban road structures. Urban Forestry & Urban Greening. 2021; 62 ():127137.
Chicago/Turabian StyleBau-Show Lin; Yin-Hua Cho; Cheng-I Hsieh. 2021. "Study of the thermal environment of sidewalks within varied urban road structures." Urban Forestry & Urban Greening 62, no. : 127137.
Five machine learning (ML) algorithms were employed for gap-filling surface fluxes of CO2, water vapor, and sensible heat above three different ecosystems: grassland, rice paddy field, and forest. The performance and limitations of these ML models, which are support vector machine, random forest, multi-layer perception, deep neural network, and long short-term memory, were investigated. Firstly, the accuracy of gap-filling to time and hysteresis input factors of ML algorithms for different ecosystems is discussed. Secondly, the optimal ML model selected in the first stage is compared with the classic method—the Penman–Monteith (P–M) equation for water vapor flux gap-filling. Thirdly, with different gap lengths (from one hour to one week), we explored the data length required for an ML model to perform the optimal gap-filling. Our results demonstrate the following: (1) for ecosystems with a strong hysteresis between surface fluxes and net radiation, adding proceeding meteorological data into the model inputs could improve the model performance; (2) the five ML models gave similar gap-filling performance; (3) for gap-filling water vapor flux, the ML model is better than the P–M equation; and (4) for a gap with length of half day, one day, or one week, an ML model with training data length greater than 1300 h would provide a better gap-filling accuracy.
I-Hang Huang; Cheng-I Hsieh. Gap-Filling of Surface Fluxes Using Machine Learning Algorithms in Various Ecosystems. Water 2020, 12, 3415 .
AMA StyleI-Hang Huang, Cheng-I Hsieh. Gap-Filling of Surface Fluxes Using Machine Learning Algorithms in Various Ecosystems. Water. 2020; 12 (12):3415.
Chicago/Turabian StyleI-Hang Huang; Cheng-I Hsieh. 2020. "Gap-Filling of Surface Fluxes Using Machine Learning Algorithms in Various Ecosystems." Water 12, no. 12: 3415.
This study presented a two-year data set of sensible heat and water vapor fluxes above a humid subtropical montane Cypress forest, located at 1650 m a.s.l. in northeastern Taiwan. The focuses of this study were to investigate (1) the diurnal and seasonal variations of canopy resistance and fluxes of sensible heat and water vapor above this forest; and (2) the mechanism of why a fixed canopy resistance could work when implementing the Penman–Monteith equation for diurnal hourly evapotranspiration estimation. Our results showed distinct seasonal variations in canopy resistance and water vapor flux, but on the contrary, the sensible heat flux did not change as much as the water vapor flux did with seasons. The seasonal variation patterns of the canopy resistance and water vapor flux were highly coupled with the meteorological factors. Also, the results demonstrated that a constant (fixed) canopy resistance was good enough for estimating the diurnal variation of evapotranspiration using Penman–Monteith equation. We observed a canopy resistance around 190 (s/m) for both the two warm seasons; and canopy resistances were around 670 and 320 (s/m) for the two cool seasons, respectively. In addition, our analytical analyses demonstrated that when the average canopy resistance is higher than 200 (s/m), the Penman–Monteith equation is less sensitive to the change of canopy resistance; hence, a fixed canopy resistance is suitable for the diurnal hourly evapotranspiration estimation. However, this is not the case when the average canopy resistance is less than 100 (s/m), and variable canopy resistances are needed. These two constraints (200 and 100) were obtained based on purely analytical analyses under a moderate meteorological condition (Rn = 600 W·m−2, RH = 60%, Ta = 20°C, U = 2 m·s−1) and a measurement height around two times of the canopy height.
Bau-Show Lin; Huimin Lei; Ming-Che Hu; Supattra Visessri; Cheng-I Hsieh. Canopy Resistance and Estimation of Evapotranspiration above a Humid Cypress Forest. Advances in Meteorology 2020, 2020, 1 -16.
AMA StyleBau-Show Lin, Huimin Lei, Ming-Che Hu, Supattra Visessri, Cheng-I Hsieh. Canopy Resistance and Estimation of Evapotranspiration above a Humid Cypress Forest. Advances in Meteorology. 2020; 2020 ():1-16.
Chicago/Turabian StyleBau-Show Lin; Huimin Lei; Ming-Che Hu; Supattra Visessri; Cheng-I Hsieh. 2020. "Canopy Resistance and Estimation of Evapotranspiration above a Humid Cypress Forest." Advances in Meteorology 2020, no. : 1-16.
To reduce energy demand (both fossil fuel and renewable energy) for cooling the urban heat island environment, some solutions have been studied. Among these methods, the water spray system is considered more flexible due to its dynamic controls. This study investigated the cooling effect of water spray systems in the street canyon under different aspect ratios and high relative humidity environments using a computational fluid dynamics model. This model was validated with water channel and wind tunnel experiments. The results showed that the most effective cooling area was the area just under the spray nozzles. However, in a narrow street canyon, people in the middle of the street may feel the cooling effect because of the dispersion and accumulation of the cooled air. Our simulations demonstrated that air under the nozzles was saturated and this revealed that under drier conditions the water spray systems will have higher cooling performance. We also found that using large water droplets created a wider cooling area in the middle of the street canyon, and this phenomenon was not changed much if the nozzle height was increased from 2.5 m to 3.5 m.
Ying-Chen Lee; Tsang-Jung Chang; Cheng-I Hsieh. A Numerical Study of the Temperature Reduction by Water Spray Systems within Urban Street Canyons. Sustainability 2018, 10, 1190 .
AMA StyleYing-Chen Lee, Tsang-Jung Chang, Cheng-I Hsieh. A Numerical Study of the Temperature Reduction by Water Spray Systems within Urban Street Canyons. Sustainability. 2018; 10 (4):1190.
Chicago/Turabian StyleYing-Chen Lee; Tsang-Jung Chang; Cheng-I Hsieh. 2018. "A Numerical Study of the Temperature Reduction by Water Spray Systems within Urban Street Canyons." Sustainability 10, no. 4: 1190.
Cheng-Wei Huang; Chia-Ren Chu; Cheng-I Hsieh; Sari Palmroth; Gabriel Katul. Wind-induced leaf transpiration. Advances in Water Resources 2015, 86, 240 -255.
AMA StyleCheng-Wei Huang, Chia-Ren Chu, Cheng-I Hsieh, Sari Palmroth, Gabriel Katul. Wind-induced leaf transpiration. Advances in Water Resources. 2015; 86 ():240-255.
Chicago/Turabian StyleCheng-Wei Huang; Chia-Ren Chu; Cheng-I Hsieh; Sari Palmroth; Gabriel Katul. 2015. "Wind-induced leaf transpiration." Advances in Water Resources 86, no. : 240-255.
Dohyoung Kim; Ram Oren; Andrew Oishi; Cheng-I Hsieh; Nathan G Phillips; Kimberly A. Novick; Paul Stoy. Erratum to “Sensitivity of stand transpiration to wind velocity in a mixed broadleaved deciduous forest” [Agric. Forest Meteorol. 187 (2014) 62–71]. Agricultural and Forest Meteorology 2014, 192-193, 41 .
AMA StyleDohyoung Kim, Ram Oren, Andrew Oishi, Cheng-I Hsieh, Nathan G Phillips, Kimberly A. Novick, Paul Stoy. Erratum to “Sensitivity of stand transpiration to wind velocity in a mixed broadleaved deciduous forest” [Agric. Forest Meteorol. 187 (2014) 62–71]. Agricultural and Forest Meteorology. 2014; 192-193 ():41.
Chicago/Turabian StyleDohyoung Kim; Ram Oren; Andrew Oishi; Cheng-I Hsieh; Nathan G Phillips; Kimberly A. Novick; Paul Stoy. 2014. "Erratum to “Sensitivity of stand transpiration to wind velocity in a mixed broadleaved deciduous forest” [Agric. Forest Meteorol. 187 (2014) 62–71]." Agricultural and Forest Meteorology 192-193, no. : 41.
Wind velocity (U) within and above forest canopies can alter the coupling between the vapor-saturated sub-stomatal airspace and the drier atmosphere aloft, thereby influencing transpiration rates. In practice, however, the actual increase in transpiration with increasing U depends on the aerodynamic resistance (RA) to vapor transfer compared to canopy resistance to water vapor flux out of leaves (RC, dominated by stomatal resistance, Rstom), and the rate at which RA decreases with increasing U. We investigated the effect of U on transpiration at the canopy scale using filtered meteorological data and sap flux measurements gathered from six diverse species of a mature broadleaved deciduous forest. Only under high light conditions, stand transpiration (EC) increased slightly (6.5%) with increasing U ranging from ∼0.7 to ∼4.7 m s−1. Under other conditions, sap flux density (Js) and EC responded weakly or did not change with U. RA, estimated from Monin–Obukhov similarity theory, decreased with increasing U, but this decline was offset by increasing RC, estimated from a rearranged Penman–Monteith equation, due to a concurrent increase in vapor pressure deficit (D). The increase of RC with D over the observed range of U was consistent with increased Rstom by ∼40% based on hydraulic theory. Except for very rare half-hourly values, the proportion of RA to total resistance (RT) remained <15% over the observed range of conditions. These results suggest that in similar forests and conditions, the direct effect of U reducing RA and thus increasing transpiration is negligible. However, the observed U–D relationship and its effect on Rstom must be considered when modeling canopy photosynthesis.
Dohyoung Kim; Ram Oren; A. Christopher Oishi; Cheng-I Hsieh; Nathan Phillips; Kimberly A. Novick; Paul C. Stoy. Sensitivity of stand transpiration to wind velocity in a mixed broadleaved deciduous forest. Agricultural and Forest Meteorology 2013, 187, 62 -71.
AMA StyleDohyoung Kim, Ram Oren, A. Christopher Oishi, Cheng-I Hsieh, Nathan Phillips, Kimberly A. Novick, Paul C. Stoy. Sensitivity of stand transpiration to wind velocity in a mixed broadleaved deciduous forest. Agricultural and Forest Meteorology. 2013; 187 ():62-71.
Chicago/Turabian StyleDohyoung Kim; Ram Oren; A. Christopher Oishi; Cheng-I Hsieh; Nathan Phillips; Kimberly A. Novick; Paul C. Stoy. 2013. "Sensitivity of stand transpiration to wind velocity in a mixed broadleaved deciduous forest." Agricultural and Forest Meteorology 187, no. : 62-71.
Yi-Long Tu; Tsang-Jung Chang; Cheng-I Hsieh; Jen-Ying Shih. Artificial neural networks in the estimation of monthly capacity factors of WECS in Taiwan. Energy Conversion and Management 2010, 51, 2938 -2946.
AMA StyleYi-Long Tu, Tsang-Jung Chang, Cheng-I Hsieh, Jen-Ying Shih. Artificial neural networks in the estimation of monthly capacity factors of WECS in Taiwan. Energy Conversion and Management. 2010; 51 (12):2938-2946.
Chicago/Turabian StyleYi-Long Tu; Tsang-Jung Chang; Cheng-I Hsieh; Jen-Ying Shih. 2010. "Artificial neural networks in the estimation of monthly capacity factors of WECS in Taiwan." Energy Conversion and Management 51, no. 12: 2938-2946.
Measurements of meteorological variables and surface energy components over the South China Sea (SCS) are compared with the NCEP-DOE AMIP-II reanalysis (NCEP2). The observations were conducted on a research vessel in the summers of 2004 and 2006. In addition, a one-column ocean model is used to simulate surface energy components and upper-level water temperatures (at 4 and 10 m depths). The simulated upper-level water temperatures agree well with the observations during the two cruises (OR1-728, OR1-802) with a root-mean-square difference (RMSD) smaller than 0.4 K. The observations and the simulations show that the solar radiation (with a mean of similar to 200 W m(-2)) is stronger than the latent heat flux (similar to 160 W m(-2)), and the latent heat flux is stronger than the sensible heat flux (similar to 10 W m(-2)) during both periods. Nonetheless, the magnitude of variability in heat flux caused by the sporadic wind is not seen in the reanalysis, it appears in the turbulent heat flux simulated by the model. The major differences between the model estimate and the NCEP2 reanalysis are the value of emissivity and the inclusion of diurnal cycles in key variables, with the value of NCEP2 for emissivity as 1. The emissivity of this part of ocean is observed to be 0.96 with albedo at 0.07
Yung-Yao Lan; Ben-Jei Tsuang; Chia-Ying Tu; Ting-Yu Wu; Yuan-Long Chen; Cheng-I Hsieh. Observation and Simulation of Meteorology and Surface Energy Components over the South China Sea in Summers of 2004 and 2006. Terrestrial, Atmospheric and Oceanic Sciences 2010, 21, 325 .
AMA StyleYung-Yao Lan, Ben-Jei Tsuang, Chia-Ying Tu, Ting-Yu Wu, Yuan-Long Chen, Cheng-I Hsieh. Observation and Simulation of Meteorology and Surface Energy Components over the South China Sea in Summers of 2004 and 2006. Terrestrial, Atmospheric and Oceanic Sciences. 2010; 21 (2):325.
Chicago/Turabian StyleYung-Yao Lan; Ben-Jei Tsuang; Chia-Ying Tu; Ting-Yu Wu; Yuan-Long Chen; Cheng-I Hsieh. 2010. "Observation and Simulation of Meteorology and Surface Energy Components over the South China Sea in Summers of 2004 and 2006." Terrestrial, Atmospheric and Oceanic Sciences 21, no. 2: 325.
Hong-Ming Kao; Tsang-Jung Chang; Yi-Fang Hsieh; Chia-Ho Wang; Cheng-I Hsieh. Comparison of airflow and particulate matter transport in multi-room buildings for different natural ventilation patterns. Energy and Buildings 2009, 41, 966 -974.
AMA StyleHong-Ming Kao, Tsang-Jung Chang, Yi-Fang Hsieh, Chia-Ho Wang, Cheng-I Hsieh. Comparison of airflow and particulate matter transport in multi-room buildings for different natural ventilation patterns. Energy and Buildings. 2009; 41 (9):966-974.
Chicago/Turabian StyleHong-Ming Kao; Tsang-Jung Chang; Yi-Fang Hsieh; Chia-Ho Wang; Cheng-I Hsieh. 2009. "Comparison of airflow and particulate matter transport in multi-room buildings for different natural ventilation patterns." Energy and Buildings 41, no. 9: 966-974.
Soil heat flux is one of the important components of surface energy balance. In this study, long-term estimation of soil heat flux from single layer soil temperature was carried out by the traditional sinusoidal analytical method and the half-order time derivative method of Wang and Bras [Wang and Bras (1999) J Hydrol 216:214–226]. In order to understand the characteristics of soil heat flux and to examine the performances of the two methods, a field experiment was conducted at a temperate and humid grassland in Cork, Ireland. Our results show that the soil heat flux had the same magnitude as the sensible heat flux at this grassland site. It was also demonstrated that the analytical method did not predict the soil heat flux well because the sinusoidal assumption for the temporal variation in soil heat flux was invalid. In contrast, good agreement was found between the soil heat flux measurements and predictions made by the half-order time derivative method. This success suggests that this method could be used to estimate soil heat flux from long-term remotely sensed surface temperature.
Cheng-I Hsieh; Cheng-Wei Huang; Ger Kiely; Gerard Kiely. Long-term estimation of soil heat flux by single layer soil temperature. International Journal of Biometeorology 2008, 53, 113 -123.
AMA StyleCheng-I Hsieh, Cheng-Wei Huang, Ger Kiely, Gerard Kiely. Long-term estimation of soil heat flux by single layer soil temperature. International Journal of Biometeorology. 2008; 53 (1):113-123.
Chicago/Turabian StyleCheng-I Hsieh; Cheng-Wei Huang; Ger Kiely; Gerard Kiely. 2008. "Long-term estimation of soil heat flux by single layer soil temperature." International Journal of Biometeorology 53, no. 1: 113-123.
This study investigated a two-dimensional Lagrangian stochastic dispersion model for estimating water vapor fluxes and footprint over homogeneous and inhomogeneous surfaces. Over the homogeneous surface, particle trajectories were computed from a 2-D Lagrangian model forced by Eulerian velocity statistics determined by Monin-Obukhov similarity theory (MOST). For an inhomogeneous surface, the velocity and atmospheric stability profiles were computed using a second-order Eulerian closure model, and these local profiles were then used to drive the Lagrangian model. The model simulations were compared with water vapor flux measurements carried out above an irrigated bare soil site and an irrigated potato site. The inhomogeneity involved a step change in surface roughness, humidity, and temperature. Good agreement between eddy-correlation-measured and Lagrangian-model-predicted water vapor fluxes was found for both sites. Hence, this analysis demonstrates the practical utility of second-order closure models in conjunction with Lagrangian analysis to estimate the scalar footprint in planar inhomogeneous flows.
Cheng-I Hsieh; Gabriel Katul. The Lagrangian stochastic model for estimating footprint and water vapor fluxes over inhomogeneous surfaces. International Journal of Biometeorology 2008, 53, 87 -100.
AMA StyleCheng-I Hsieh, Gabriel Katul. The Lagrangian stochastic model for estimating footprint and water vapor fluxes over inhomogeneous surfaces. International Journal of Biometeorology. 2008; 53 (1):87-100.
Chicago/Turabian StyleCheng-I Hsieh; Gabriel Katul. 2008. "The Lagrangian stochastic model for estimating footprint and water vapor fluxes over inhomogeneous surfaces." International Journal of Biometeorology 53, no. 1: 87-100.
Transient responses of sap flow to step changes in wind speed were experimentally investigated in a wind tunnel. A Granier-type sap flow sensor was calibrated and tested in a cylindrical tube for analysis of its transient time response. Then the sensor was used to measure the transient response of a well-watered Pachira macrocarpa plant to wind speed variations. The transient response of sap flow was described using the resistance–capacitance model. The steady sap flow rate increased as the wind speed increased at low wind speeds. Once the wind speed exceeded 8.0 m s−1, the steady sap flow rate did not increase further. The transpiration rate, measured gravimetrically, showed a similar trend. The response of nocturnal sap flow to wind speed variation was also measured and compared with the results in the daytime. Under the same wind speed, the steady sap flow rate was smaller than that in the daytime, indicating differences between diurnal and nocturnal hydraulic function, and incomplete stomatal closure at night. In addition, it was found that the temporal response of the Granier sensor is fast enough to resolve the transient behaviour of water flux in plant tissue.
Chia R. Chu; Cheng-I Hsieh; Shen-Yuang Wu; Nathan G. Phillips. Transient response of sap flow to wind speed. Journal of Experimental Botany 2008, 60, 249 -255.
AMA StyleChia R. Chu, Cheng-I Hsieh, Shen-Yuang Wu, Nathan G. Phillips. Transient response of sap flow to wind speed. Journal of Experimental Botany. 2008; 60 (1):249-255.
Chicago/Turabian StyleChia R. Chu; Cheng-I Hsieh; Shen-Yuang Wu; Nathan G. Phillips. 2008. "Transient response of sap flow to wind speed." Journal of Experimental Botany 60, no. 1: 249-255.
This study investigated the flux-variance relationships of temperature, humidity, and CO(2), and examined the performance of using this method for predicting sensible heat (H), water vapor (LE), and CO(2) fluxes (F(CO2)) with eddy-covariance measured flux data at three different ecosystems: grassland, paddy rice field, and forest. The H and LE estimations were found to be in good agreement with the measurements over the three fields. The prediction accuracy of LE could be improved by around 15% if the predictions were obtained by the flux-variance method in conjunction with measured sensible heat fluxes. Moreover, the paddy rice field was found to be a special case where water vapor follows flux-variance relation better than heat does. However, the CO(2) flux predictions were found to vary from poor to fair among the three sites. This is attributed to the complicated CO(2) sources and sinks distribution. Our results also showed that heat and water vapor were transported with the same efficiency above the grassland and rice paddy. For the forest, heat was transported 20% more efficiently than evapotranspiration.
Cheng-I Hsieh; Mei-Chun Lai; Yue-Joe Hsia; Tsang-Jung Chang. Estimation of sensible heat, water vapor, and CO2 fluxes using the flux-variance method. International Journal of Biometeorology 2008, 52, 521 -533.
AMA StyleCheng-I Hsieh, Mei-Chun Lai, Yue-Joe Hsia, Tsang-Jung Chang. Estimation of sensible heat, water vapor, and CO2 fluxes using the flux-variance method. International Journal of Biometeorology. 2008; 52 (6):521-533.
Chicago/Turabian StyleCheng-I Hsieh; Mei-Chun Lai; Yue-Joe Hsia; Tsang-Jung Chang. 2008. "Estimation of sensible heat, water vapor, and CO2 fluxes using the flux-variance method." International Journal of Biometeorology 52, no. 6: 521-533.
Above forest canopies, eddy covariance (EC) measurements of mass (CO2, H2O vapor) and energy exchange, assumed to represent ecosystem fluxes, are commonly made at one point in the roughness sublayer (RSL). A spatial variability experiment, in which EC measurements were made from six towers within the RSL in a uniform pine plantation, quantified large and dynamic spatial variation in fluxes. The spatial coefficient of variation (CV) of the scalar fluxes decreased with increasing integration time, stabilizing at a minimum that was independent of further lengthening the averaging period (hereafter a ‘stable minimum’). For all three fluxes, the stable minimum (CV=9–11%) was reached at averaging times (τp) of 6–7 h during daytime, but higher stable minima (CV=46–158%) were reached at longer τp (>12 h) during nighttime. To the extent that decreasing CV of EC fluxes reflects reduction in micrometeorological sampling errors, half of the observed variability at τp=30 min is attributed to sampling errors. The remaining half (indicated by the stable minimum CV) is attributed to underlying variability in ecosystem structural properties, as determined by leaf area index, and perhaps associated ecosystem activity attributes. We further assessed the spatial variability estimates in the context of uncertainty in annual net ecosystem exchange (NEE). First, we adjusted annual NEE values obtained at our long‐term observation tower to account for the difference between this tower and the mean of all towers from this experiment; this increased NEE by up to 55 g C m−2 yr−1. Second, we combined uncertainty from gap filling and instrument error with uncertainty because of spatial variability, producing an estimate of variability in annual NEE ranging from 79 to 127 g C m−2 yr−1. This analysis demonstrated that even in such a uniform pine plantation, in some years spatial variability can contribute ∼50% of the uncertainty in annual NEE estimates.
Ram Oren; Cheng-I Hsieh; Paul Stoy; John Albertson; Heather R McCarthy; Peter Harrell; Gabriel Katul. Estimating the uncertainty in annual net ecosystem carbon exchange: spatial variation in turbulent fluxes and sampling errors in eddy-covariance measurements. Global Change Biology 2006, 12, 883 -896.
AMA StyleRam Oren, Cheng-I Hsieh, Paul Stoy, John Albertson, Heather R McCarthy, Peter Harrell, Gabriel Katul. Estimating the uncertainty in annual net ecosystem carbon exchange: spatial variation in turbulent fluxes and sampling errors in eddy-covariance measurements. Global Change Biology. 2006; 12 (5):883-896.
Chicago/Turabian StyleRam Oren; Cheng-I Hsieh; Paul Stoy; John Albertson; Heather R McCarthy; Peter Harrell; Gabriel Katul. 2006. "Estimating the uncertainty in annual net ecosystem carbon exchange: spatial variation in turbulent fluxes and sampling errors in eddy-covariance measurements." Global Change Biology 12, no. 5: 883-896.
Increases in atmospheric CO2 concentration not only affects climate variables such as precipitation and air temperature, but also affects intrinsic ecosystem physiological properties such as bulk stomatal conductance and intercellular CO2 concentration. De-convolving these two effects remains uncertain in biosphere–atmosphere water and carbon cycling. Using a simplified analytical net ecosystem CO2 exchange (NEE) model, tested with recently collected flux measurements in a humid grassland ecosystem in Ireland, we assess how much projected climate shifts affect net canopy photosynthesis (A) without physiological adjustments and contrast those findings with published field data on physiological adjustments for several grassland ecosystems. Our analysis suggests that the intrinsic grassland ecosystem physiological adjustment of A is about 45 times more important than the resulting climatic forcing shifts from the IS92a scenario (and a doubling of atmospheric CO2 concentration). Also, our analysis shows that increase in precipitation results in concomitant decrease in the two climate variables—net radiation and vapor pressure deficit, and these decreases have opposite (and almost canceling) effects on A. Implications to afforestation policy and future experimental efforts to quantify the carbon sink from humid grassland ecosystems are also discussed.
Cheng-I Hsieh; Ger Kiely; Adrian Birkby; Gabriel Katul. Photosynthetic responses of a humid grassland ecosystem to future climate perturbations. Advances in Water Resources 2005, 28, 910 -916.
AMA StyleCheng-I Hsieh, Ger Kiely, Adrian Birkby, Gabriel Katul. Photosynthetic responses of a humid grassland ecosystem to future climate perturbations. Advances in Water Resources. 2005; 28 (9):910-916.
Chicago/Turabian StyleCheng-I Hsieh; Ger Kiely; Adrian Birkby; Gabriel Katul. 2005. "Photosynthetic responses of a humid grassland ecosystem to future climate perturbations." Advances in Water Resources 28, no. 9: 910-916.
N2O emissions from a fertilized humid grassland near Cork, Ireland were continuously measured during 2003 using an eddy covariance system. For most of the year emissions were close to zero and 60% of the emissions occurred in eight major events of 2–20 days’ duration. Two hundred and seven kg ha−1 of synthetic N and 130 kg ha−1 organic N were applied over the year and the total measured annual N2O emission was 11.6 kg N ha−1. The flux data were used to test the prediction of N2O emissions by the DNDC (DeNitrification – DeComposition) model. The model predicted total emissions of 15.4 kg N ha−1, 32 % more than the observed emissions. On this basis the model was further used to simulate (a) background (non-anthropogenic) N2O emissions and (b) the effect on N2O emissions of future climate perturbations based on the Hadley Center model output of the IS92a scenario for Ireland. DNDC predicts 1.7 kg N ha−1 year−1 of background N2O emissions, accounting for 15% of the observed emissions. Climate shifts will increase total annual modeled N2O emissions from 15.4 kg N ha−1 to 22.4 kg N ha−1 if current levels of N applications are maintained, or to 21.2 kg N ha−1 if synthetic N applications are reduced to 170 kg N ha−1 to comply with recent EU water quality legislation. Thus the projected increase in N2O emissions due to climate change is far larger than the decrease expected from reduced fertilizer applications.
Cheng-I Hsieh; Paul Leahy; Ger Kiely; Changsheng Li; Gerard Kiely. The Effect of Future Climate Perturbations on N2O Emissions from a Fertilized Humid Grassland. Nutrient Cycling in Agroecosystems 2005, 73, 15 -23.
AMA StyleCheng-I Hsieh, Paul Leahy, Ger Kiely, Changsheng Li, Gerard Kiely. The Effect of Future Climate Perturbations on N2O Emissions from a Fertilized Humid Grassland. Nutrient Cycling in Agroecosystems. 2005; 73 (1):15-23.
Chicago/Turabian StyleCheng-I Hsieh; Paul Leahy; Ger Kiely; Changsheng Li; Gerard Kiely. 2005. "The Effect of Future Climate Perturbations on N2O Emissions from a Fertilized Humid Grassland." Nutrient Cycling in Agroecosystems 73, no. 1: 15-23.
In this study, a fluidized-bed reactor (FBR) was employed to treat copper-containing wastewater by mean of copper precipitation on the surface of sand grains. The conditions for optimum copper removal efficiency were also investigated. This technology was controlled so as to keep supersaturation low to induce the nucleated precipitation of copper coating on the sand surface in an FBR. The effects of relevant parameters, such as the pH value, the molar ratio of [C(T)] to [Cu(2+)], hydraulic loading and the types of chemical reagents used, were examined. The experimental results indicated that 96% copper removal efficiency could be achieved when the influent copper concentration was 10mg l(-1). The optimum chemical reagent was Na(2)CO(3); the molar ratio of [C(T)]/[Cu(2+)] was 2, and the optimal hydraulic loading was not be more than 25m h(-1). In addition, preventing homogeneous nucleation in the FBR was an important operation parameter. Homogeneous nucleation and molecular growth would lead to undesirable microparticle formation in the effluent. A good mixture of carbonate and copper in the presence of sand grains could reduce the level of homogeneous nucleation in the bottom of the reactor. Energy dispersive analysis (EDS) of X-rays provided insight into the copper coating on the sand surface, and element analysis indicated the weight percentages of CuCO(3) and Cu(OH)(2) in precipitate.
Chia-I Lee; Wan-Fa Yang; Cheng-I Hsieh. Removal of Cu(II) from aqueous solution in a fluidized-bed reactor. Chemosphere 2004, 57, 1173 -1180.
AMA StyleChia-I Lee, Wan-Fa Yang, Cheng-I Hsieh. Removal of Cu(II) from aqueous solution in a fluidized-bed reactor. Chemosphere. 2004; 57 (9):1173-1180.
Chicago/Turabian StyleChia-I Lee; Wan-Fa Yang; Cheng-I Hsieh. 2004. "Removal of Cu(II) from aqueous solution in a fluidized-bed reactor." Chemosphere 57, no. 9: 1173-1180.
This study was performed in a fluidized-bed reactor (FBR) filled with manganese-coated sand (MCS) to treat copper-contaminated wastewater. The adsorption characteristics of MCS, the adsorption equilibrium of MCS, and the copper removal capacity by MCS in FBR were investigated. In terms of the adsorption characteristics of MCS, the surface of MCS was evaluated using a scanning electron microscope (SEM). Energy dispersive analysis (EDS) of X-rays indicated the composition of MCS, and the quantity of manganese on MCS was determined by means of acid digestion analysis. The experimental results indicated that copper was removed by both sorption (ion exchange and adsorption) and coprecipitation on the surface of MCS in FBR. Copper removal efficiency was highly dependent on the pH and increased with increasing pH from pH 2 to 8. After the copper adsorption by MCS, the pH in solution was decreased. When the MCS concentration was greater than 10 g/l, the copper adsorptivities obtained by FBR were almost the same as that from the shaker and when the MCS concentration reached 40 g/l, the copper adsorptivity in FBR was greater than that from the shaker. The adsorption sites of MCS could be used efficiently by the FBR. A Langmuir adsorption isotherm equation fit the measured adsorption data from the batch equilibrium adsorption test better than the Freundlich adsorption isotherm equation did. In addition, the adsorption rate increased when the influent wastewater was aerated.
Chia-I Lee; Wan-Fa Yang; Cheng-I Hsieh. Removal of copper (II) by manganese-coated sand in a liquid fluidized-bed reactor. Journal of Hazardous Materials 2004, 114, 45 -51.
AMA StyleChia-I Lee, Wan-Fa Yang, Cheng-I Hsieh. Removal of copper (II) by manganese-coated sand in a liquid fluidized-bed reactor. Journal of Hazardous Materials. 2004; 114 (1-3):45-51.
Chicago/Turabian StyleChia-I Lee; Wan-Fa Yang; Cheng-I Hsieh. 2004. "Removal of copper (II) by manganese-coated sand in a liquid fluidized-bed reactor." Journal of Hazardous Materials 114, no. 1-3: 45-51.
This study proposes a two-dimensional Lagrangian stochastic dispersion model forestimating spatial and temporal variation of scalar sources, sinks, and fluxes withina forest canopy. Carbon dioxide and heat dispersion experiments were conducted forfield testing the model. These experiments also provided data for field testing a newlydeveloped one-dimensional Lagrangian analytical dispersion model. It was found that these two models produce similar scalar source-sinkand flux distribution patterns. Comparing with CO2 flux measurements, the one-dimensional model performed as well as the two-dimensional model even whenthe fetch is short (≈100 m). To drive these Lagrangian models, velocitystatistics through the canopy volume must be specified a priori. The sensitivity of thecomputed sources, sinks, and fluxes to the description of the flow statistics was furtherexamined. All in all, we found good agreement between model predicted andeddy-correlation measured CO2 and sensible heat fluxes.
Cheng-I Hsieh; Mário Siqueira; Gabriel Katul; Chia-Ren Chu. Predicting Scalar Source-Sink and Flux Distributions Within a Forest Canopy Using a 2-D Lagrangian Stochastic Dispersion Model. Boundary-Layer Meteorology 2003, 109, 113 -138.
AMA StyleCheng-I Hsieh, Mário Siqueira, Gabriel Katul, Chia-Ren Chu. Predicting Scalar Source-Sink and Flux Distributions Within a Forest Canopy Using a 2-D Lagrangian Stochastic Dispersion Model. Boundary-Layer Meteorology. 2003; 109 (2):113-138.
Chicago/Turabian StyleCheng-I Hsieh; Mário Siqueira; Gabriel Katul; Chia-Ren Chu. 2003. "Predicting Scalar Source-Sink and Flux Distributions Within a Forest Canopy Using a 2-D Lagrangian Stochastic Dispersion Model." Boundary-Layer Meteorology 109, no. 2: 113-138.