Energy Balance Experiment Research Articles

Enteric Methane Emissions, Rumen Fermentation Characteristics, and Energetic Efficiency of Holstein Crossbred Bulls Fed Total Mixed Ration Silage with Cassava instead of Rice Straw

This study investigated the effects of substituting rice straw with cassava in total mixed ration silage on feed intake, digestibility, rumen fermentation, ruminating activity, and energy balance. An energy balance experiment was conducted to determine nutrient and energy utilization in dairy bulls. Four Holstein Friesian (HF) crossbred young bulls (93.19% HF × 6.81% Native Thai; average age of 12.08 ± 0.22 months and body weight of 266 ± 9.80 kg) were used in a 4 × 4 Latin square design with four 28-d periods. The four dietary treatments included substituting cassava with rice straw on a 50, 150, 250, and 350 g/kg dry matter basis. Increasing the amount of cassava in the diet resulted in linearly decreased rumination behaviors and enteric methane emissions (p < 0.05) but a linear increase in feed intake and digestibility, total volatile fatty acid concentration, and propionic acid: acetic acid ratio in the rumen fluid (p < 0.05), thus leading to a greater energy balance status (p < 0.01). Our results indicated that replacing cassava with rice straw from 5% to 35% in the ration of Holstein bulls resulted in a substantial reduction in physically effective fiber and chewing time but improved nutrient and energy supply. The metabolizable energy requirement for the maintenance of crossbred dairy bulls was estimated to be 599.9 kJ/kg metabolic body weight and the efficiency of metabolizable energy used for growth was 0.88. We concluded that cassava is a good energy feed resource for Holstein crossbred bulls in the tropics.

The age-related metabolizable energy of cereal grains, oilseed meals, corn gluten meals, and feather meals for broilers.

A 2 × 3 factorial arrangement of treatments with two ages of broilers (11 to 14 or 25 to 28 d of age) and three samples of feed ingredients was utilized to compare metabolizable energy (ME) and ratio of ME to gross energy (GE) in each group of three cereal grains (CG, including one corn, two wheat flour), three oilseed meals (OM, including one soybean meal, one peanut meal, and one cottonseed meal), three corn gluten meals (CGM A, B, and C), and three feather meals (FM A, B, and C). Each treatment contained six replicates of four Arbor Acre male broilers in energy balance experiments. Trends toward interactions between age and source of CG were observed on the ME and ME/GE of CG (0.05 <P < 0.10). The ME and ME/GE in corn were greater for broilers from 25 to 28 than for 11 to 14 d of age (P < 0.05). However, the ME and ME/GE in wheat flour A and B were not affected by the age of the broilers. The ME and ME/GE of OM were not affected by the age of broilers but differed across sources (P < 0.01). Conversely, the ME and ME/GE of FM were not different across sources of FM, but the ME and ME/GE of FM were less for broilers from 11 to 14 compared to 25 to 28 d of age (P < 0.01). Significant interactions between age and sources of CGM affected the ME and ME/GE of CGM (P < 0.05). The ME and ME/GE of CGM A were greater than CGM B (P < 0.05) when fed to broilers from 25 to 28 d of age but there was no effect from 11 to 14 d of age. The ME and ME/GE of CGM were less in broilers from 11 to 14 compared to 25 to 28 d of age (P < 0.05). These results indicate that the energy value of wheat flour and OM are similar regardless of age, but the ME in starter diets with corn, CGM, and FM may be overestimated if the ME values are obtained from growing broilers.

Indirect Calorimetry to Assess Energy Balance in Mice: Measurement and Data Analysis.

Understanding the factors affecting body weight regulation requires careful measurement of food intake and metabolic rates. Modern indirect calorimetry systems are designed to record these features. Here, we describe our approach for reproducible analysis of energy balance experiments performed using indirect calorimetry. CalR, a free online web tool, calculates both instantaneous and cumulative totals for metabolic variables including food intake, energy expenditure, and energy balance making it an excellent start for analyzing energy balance experiments. Energy balance may be one of the most important metrics that CalR calculates as it provides a clear picture of metabolic trends resulting from experimental interventions. Because of the complexity of indirect calorimetry devices and the frequency of mechanical breakdowns, we place a heavy emphasis on the importance of data refinement and visualization. Plots representing energy intake or energy expenditure versus body mass or physical activity can help to identify a malfunctioning apparatus. We also introduce a critical visualization of experimental quality control: a plot of the change in energy balance versus the change in body mass, which simultaneously represents many of the essential components of indirect calorimetry. These analyses and data visualizations allow the investigator to make inferences about experimental quality control and the validity of experimental results.

Impact of vegetation water content information on soil moisture retrievals in agricultural regions: An analysis based on the SMAPVEX16-MicroWEX dataset

Soil moisture (SM) retrieval in agricultural regions during the growing seasons is particularly challenging due to high spatial variability and dynamic vegetation conditions. The retrievals have been problematic even when the passive signatures at different spatial scales match well since they depend upon the accuracy of vegetation information such as the vegetation water content (VWC). The VWC used in the Soil Moisture Active Passive (SMAP) single channel retrieval algorithm (SCA) is derived from remotely sensed, climatologically-based Normalized Difference Vegetation Index (NDVI), which does not respond to real-time vegetation dynamics and is prone to saturation. This study explored the differences and seasonal trend in passive signatures and SM at satellite- and field-scales and investigated uncertainties in retrievals arising from different approaches used to estimate VWC from optical and radar indices. It used high temporal resolution, ground-based data collected during the SMAP Validation-Microwave Water, Energy Balance Experiment in 2016 (SMAPVEX16-MicroWEX) during a growing season of corn and soybean. Overall, the brightness temperatures (TB) from SMAP matched well with the upscaled, ground-based TB, with a root mean square differences (RMSDs) of about 5 K. In contrast, the SMAP SM retrievals were worse during rapid vegetation growth in the mid-season, with higher RMSDs compared to the upscaled in situ SM, than those in the late-season. In addition, the ground-based TB from corn and soybean were similar in the early and the late seasons, while their emission differences were > 40 K in the mid season. This indicates the importance of accurate VWC information, particularly during the early and late growing seasons, to account for sub-pixel heterogeneities in agricultural regions. VWC obtained from five optical and radar indices were used in the SMAP SCA for soil moisture retrieval for the entire growing season of corn. The NDVI-based VWC provided SM retrievals that were consistently lower compared to those using in situ VWC, with a higher RMSD of 0.030 m3/m3 and a negative bias of 0.020 m3/m3 for VWC > 4 kg/m2. The Normalized Difference Water Index (NDWI)-derived VWC resulted in lower SM retrieval RMSD of 0.022 m3/m3 when compared with in situ SM. Among the three radar indices, vertically polarized cross-pol ratio (CRvv)-derived VWC provided similar RMSDs in retrieved SM as the NDWI-derived VWC during the growing season. The radar vegetation index (RVI)-derived VWC improved in the late season compared to the in situ VWC and resulted in SM retrievals with RMSDs similar to the CRvv-derived retrievals. Results presented here suggest that SMAP SCA SM retrievals could be improved through the use of near-real time NDWI and CRvv-derived vegetation information. Microwave data are available regardless of cloud cover, so the guaranteed availability of CRvv to capture seasonal and interannual variability is advantageous.

A big-data approach to understanding metabolic rate and response to obesity in laboratory mice.

Maintaining a healthy body weight requires an exquisite balance between energy intake and energy expenditure. To understand the genetic and environmental factors that contribute to the regulation of body weight, an important first step is to establish the normal range of metabolic values and primary sources contributing to variability. Energy metabolism is measured by powerful and sensitive indirect calorimetry devices. Analysis of nearly 10,000 wild-type mice from two large-scale experiments revealed that the largest variation in energy expenditure is due to body composition, ambient temperature, and institutional site of experimentation. We also analyze variation in 2329 knockout strains and establish a reference for the magnitude of metabolic changes. Based on these findings, we provide suggestions for how best to design and conduct energy balance experiments in rodents. These recommendations will move us closer to the goal of a centralized physiological repository to foster transparency, rigor and reproducibility in metabolic physiology experimentation.

Development of a dynamic energy-partitioning model for enteric methane emissions and milk production in goats using energy balance data from indirect calorimetry studies

The main objective of this study was to develop a dynamic energy balance model for dairy goats to describe and quantify energy partitioning between energy used for work (milk) and that lost to the environment. Increasing worldwide concerns regarding livestock contribution to global warming underscore the importance of improving energy efficiency utilization in dairy goats by reducing energy losses in feces, urine and methane (CH4). A dynamic model of CH4 emissions from experimental energy balance data in goats is proposed and parameterized (n = 48 individual animal observations). The model includes DM intake, NDF and lipid content of the diet as explanatory variables for CH4 emissions. An additional data set (n = 122 individual animals) from eight energy balance experiments was used to evaluate the model. The model adequately (root MS prediction error, RMSPE) represented energy in milk (E-milk; RMSPE = 5.6%), heat production (HP; RMSPE = 4.3%) and CH4 emissions (E-CH4; RMSPE = 11.9%). Residual analysis indicated that most of the prediction errors were due to unexplained variations with small mean and slope bias. Some mean bias was detected for HP (1.12%) and E-CH4 (1.27%) but was around zero for E-milk (0.14%). The slope bias was zero for HP (0.01%) and close to zero for E-milk (0.10%) and E-CH4 (0.22%). Random bias was >98% for E-CH4, HP and E-milk, indicating non-systematic errors and that mechanisms in the model are properly represented. As predicted energy increased, the model tended to underpredict E-CH4 and E-milk. The model is a first step toward a mechanistic description of nutrient use by goats and is useful as a research tool for investigating energy partitioning during lactation. The model described in this study could be used as a tool for making enteric CH4 emission inventories for goats.

Cyberlindnera jadinii yeast as a protein source for growing pigs: Effects on protein and energy metabolism

Inactivated Cyberlindnera jadinii yeast (previously classified as Candida utilis) produced from local lignocellulosic biomass-based sugars is an alternative protein source in diets for young pigs. The objective of this study was to evaluate the effects of diets containing C. jadinii on the nitrogen and energy metabolism and apparent total tract digestibility (ATTD) of major nutrients and energy in young pigs. Twenty-four intact boars with a mean initial body weight of 16.7 ± 4.5 kg were assigned to four diets: a conventional control diet for young pigs with soybean meal, fish meal, rapeseed meal and potato protein concentrate as major protein sources or one of three experimental diets containing 10, 20, and 40%% of crude protein (CP) from C. jadinii. The pigs were equally distributed to the dietary treatments according to initial body weight and litter, comprising a total of six replicates per diet. The experiment was carried out during three periods of 14 days. Each period comprised an energy and nitrogen balance experiment of four consecutive days including a 22 h respiration experiment by means of indirect calorimetry. Adding C. jadinii to diets did not affect the ATTD of nutrients and energy in the diets. The energy and nitrogen metabolism was not affected by partially replacing the main protein sources with C. jadinii. Collectively, the results indicate that CP from C. jadinii can replace up to 40% of dietary CP from conventional protein sources while maintaining the efficiency of nitrogen and energy metabolism in young pigs.

Measurements of Soil Surface Roughness During the Fourth Microwave Water and Energy Balance Experiment: April 18 through June 13, 2005

Passive microwave signatures have been used to retrieve geophysical parameters, such as soil temperature [Njoku and Li, 1999], moisture [Jackson et al., 1995], and surface roughness [Wegmüller and Mätzler, 1999]. One of the challenges in the parameter retrieval is the effect of soil surface roughness on the microwave emission. We conducted soil surface roughness measurements as part of our fourth Microwave Water and Energy Balance Experiment (MicroWEX-4) to understand the effects of surface roughness on microwave signatures at 6.7 GHz (λ = 4.48 cm). The dataset will also be used to develop and validate surface roughness models. In this report, we summarize briefly the theoretical background of surface roughness characteristics and discuss methodology and results of the roughness experiments. This document is Circular 1483, one of a series of the Department of Agricultural and Biological Engineering, UF/IFAS Extension. Original publication date November 2005. CIR1483/AE363: Measurements of Soil Surface Roughness During the Fourth Microwave Water and Energy Balance Experiment: April 18–June 13, 2005 (ufl.edu)

Field Observations During the Second Microwave Water and Energy Balance Experiment (MicroWEX-2): from March 17 through June 3, 2004

The goal of MicroWEX-2 was to understand the land-atmosphere interactions during the growing season of corn, and their effect on observed microwave brightness signatures at 6.7 GHz, matching that of the satellite-based microwave radiometer, AMSR. This document is Circular 1480, one of a series of the Department of Agricultural and Biological Engineering, UF/IFAS Extension. Original publication date November 2005. CIR1480/AE360: Field Observations During the Second Microwave Water and Energy Balance Experiment (MicroWEX-2): from March 17 through June 3, 2004 (ufl.edu)

Field Observations During the Fourth Microwave Water and Energy Balance Experiment (MicroWEX-4): from March 10 - June 14, 2005

The goal of MicroWEX-4 was to understand the land-atmosphere interactions during the growing season of corn, and their effect on observed microwave brightness signatures at 6.7 GHz, matching that of the satellite based microwave radiometer, AMSR. This document is Circular 1482, one of a series of the Department of Agricultural and Biological Engineering, UF/IFAS Extension. Original publication date November 2005. CIR1482/AE362: Field Observations During the Fourth Microwave Water and Energy Balance Experiment (MicroWEX-4): March 10–June 14, 2005 (ufl.edu)

Field Observations During the Third Microwave Water and Energy Balance Experiment (MicroWEX-3): June 16 - December 21, 2004

The goal of MicroWEX-3 was to understand the land-atmosphere interactions during the growing season of cotton, and their effect on observed microwave brightness signatures at 6.7 GHz, matching that of the two satellite-based microwave radiometers (AMSR-E and AMSR). This document is Circular 1481, one of a series of the Department of Agricultural and Biological Engineering, UF/IFAS Extension. Original publication date November 2005. CIR1481/AE361: Field Observations During the Third Microwave Water and Energy Balance Experiment (MicroWEX-3): June 16–December 21, 2004 (ufl.edu)

Field Data Report for the First Microwave Water and Energy Balance Experiment (MicroWEX-1), July 17 - December 16, 2003, Citra, Florida

Many studies have been conducted in agricultural areas such as bare soil, grass, soybean, wheat, pasture, and corn to understand the relationship between soil moisture and microwave remote sensing. Most of these experiments conducted in agricultural regions have been short-term experiments that captured only a part of growing seasons. It is important to know how microwave brightness signature varies with soil moisture, evapotranspiration (ET), and biomass in a dynamic agricultural canopy with a significant biomass (4-6 kg/m2 ) throughout the growing season. This document is Circular 1470, one of a series of the Agricultural and Biological Engineering Department, Agricultural Research Station, Institute of Food and Agricultural Sciences, University of Florida. First published April 2005. &#x0D; Cicular 14/AE288: Field Data Report for the First Microwave Water and Energy Balance Experiment (MicroWEX-1), July 17–December 16, 2003, Citra, Florida (ufl.edu)

Dynamic model development of enteric methane emission from goats based on energy balance measured in indirect open circuit respiration calorimeter

A dynamic model of methane (CH4) emission in goats was proposed and parameterized from energy balance experimental data. The model focused on dry matter intake and fat content of the diet as explanatory variables for CH4 emission. Experimental and literature data were used to develop the model. Then, data (n = 123) from five energy balance experiments were used to evaluate the model. The model was adequate to represent energy in milk, heat production and CH4 emissions. Residual analysis showed that most of the prediction errors were due to unexplained variations with small mean and slope bias (around zero with exception of CH4; <6%). The model tends to over-predict energy in CH4 at higher energy intake and, energy in milk and heat production at lower energy intake. Random bias was greater than 90%, signifying than more than 90% of the error was non-systematic indicating the mechanism in the model are properly represented. The model is a first step towards a mechanistic description of nutrient use by goats and, useful as a research tool for investigating energy partition in dairy goat systems. The model described in this study should be considered for preparation of enteric CH4 emissions inventories for goats.

Nitrogen-corrected apparent metabolizable energy value of macadamia nut cake for broiler chickens determined by difference and regression methods

Two energy balance experiments were conducted to determine the AMEn value of Macadamia nut cake (MNC) for broiler chickens at different ages. In experiment 1, two dietary treatments were fed from 4 to 10 d of age. Dietary treatments consisted of a basal diet (no MNC) and a diet containing 60g/kg of MNC (940g/kg of basal diet+60g/kg of MNC). In experiment 2, four dietary treatments were provided from 17 to 23 d of age. Diets in second experiment were 1) basal control diet (no MNC); 2) 30g/kg of MNC (970g/kg of basal diet+30g/kg of MNC); 3) 60g/kg of MNC (940g/kg of basal diet+60g/kg of MNC); and 4) 90g/kg of MNC (910g/kg of basal diet+90g/kg of MNC). In experiment 2, broilers were restricted feeding in such a way that all the birds received the same amounts of basal diet, so that differences in AMEn consumption were only due to MNC. A single source of MNC was used in both experiments. Feed intake, body weight, energy intake, energy excretion, N intake, N excretion, AMEn intake and AMEn were determined in both experiments. In experiment 1, the AMEn was estimated using the difference method by subtracting AMEn of the basal diet from AMEn of the test diet. In experiment 2, AMEn intake was regressed against feed intake with the slope estimating AMEn of MNC. Regression equation used was Y=2,908.2x−122.73 (P<0.001; SEM of the slope=11.7; r2=0.93). The AMEn of MNC was found to be 12.09 and 12.17MJ/kg in experiment 1 and 2, respectively with an average of 12.13MJ/kg on DM basis. The results indicate that AMEn of MNC is comparable to conventional feedstuffs with similar nutrient profile, thus can be incorporated in broiler diets.

Large eddies modulating flux convergence and divergence in a disturbed unstable atmospheric surface layer

AbstractThe effects of large eddies on turbulence structures and flux transport were studied using data collected over a flat cotton field during the Energy Balance Experiment 2000 in the San Joaquin Valley of California in August 2000. Flux convergence (FC; larger fluxes at 8.7 m than 2.7 m) and divergence (FD) in latent heat flux (LE) were observed in a disturbed, unstable atmospheric surface layer, and their magnitudes largely departed from the prediction of Monin‐Obukhov similarity theory. From our wavelet analysis, it was identified that large eddies affected turbulence structures, scalar distribution, and flux transport differently at 8.7 m and 2.7 m under the FC and FD conditions. Using the ensemble empirical mode decomposition, time series data were decomposed into large eddies and small‐scale background turbulence, the time‐domain characteristics of large eddies were examined, and the flux contribution by large eddies was also determined quantitatively. The results suggest that large eddies over the frequency range of 0.002 Hz &lt; f &lt; 0.02 Hz (predominantly 300–400 m) enhanced the vertical velocity spectra more significantly at 8.7 m than 2.7 m, leading to an increased magnitude of the cospectra and thus LE at 8.7 m. In the FD case, however, these large eddies were not present and even suppressed in the vertical velocity spectra at 8.7 m. Consequently, the cospectra divergence over the low‐frequency ranges primarily caused the LE divergence. This work implies that large eddies may either improve or degrade the surface energy balance closure by increasing or decreasing turbulent fluxes, respectively.

Impact of Bias Correction Methods on Estimation of Soil Moisture When Assimilating Active and Passive Microwave Observations

In this paper, bias correction approaches are investigated to understand their impact on assimilating active and/or passive microwave observations on near-surface soil moisture (SM) estimates. Synthetic and field observations were assimilated in a soil–vegetation–atmosphere transfer model linked with an integrated active–passive model at L-band for bare soil. The two bias correction methods included in this study are the online bias correction with feedback (BCWF) with extended implementation with nonlinear observation operators and the simultaneous state parameter (SSP) update. New equations for BCWF were derived for the case of nonlinear observation operators because current versions of this approach were not applicable for improving SM by assimilating microwave observations. In SSP, the bias is compensated by tunning the values of the parameters. The two approaches resulted in similar accuracy for improving SM estimates compared with the uncorrected estimates. SSP showed the highest certainty for both synthetic and field observations. Using the bias correction methods, the mean estimates of SM improved by up to 88%, 87%, and 94%, when passive, active, and active–passive synthetic observations were assimilated, respectively, compared with the open-loop estimates. In contrast, when assimilating field observations from the Eleventh Microwave Water Energy Balance Experiment, the mean estimates of SM improved by up to 44%, 18%, and 48%, when passive, active, and active–passive observations were assimilated, respectively, compared with open-loop estimates. The decrement in improving the SM estimates suggests sources of uncertainty other than those from model parameters and forcings.

Field Observations during the Eleventh Microwave Water and Energy Balance Experiment (MicroWEX-11): from April 25, 2012, through December 6, 2012

This new report from UF/IFAS researchers provides another set of observation data that can be used to develop better models for accurate prediction of weather and near-term climate. It describes the observations conducted during the MicroWEX-11, a season-long experiment incorporating active and passive microwave observations for bare soil, elephant grass, and sweet corn using a variety of sensors to understand land–atmosphere interactions and their effect on observed microwave signatures. These observations match that of satellite-based passive microwave radiometers and NASA’s recently launched Soil Moisture Active Passive (SMAP) mission. This 96-page report was written by Tara Bongiovanni, Pang-Wei Liu, Karthik Nagarajan, Daniel Preston, Patrick Rush, Tim H.M. van Emmerik, Robert Terwilleger, Alejandro Monsivais-Huertero, Jasmeet Judge, Susan Steele-Dunne, Roger De Roo, Ruzbeh Akbar, Ella Baar, Max Wallace, and Anthony England and published by the UF Department of Agricultural and Biological Engineering, July 2015.&#x0D; AE514/AE514: Field Observations during the Eleventh Microwave Water and Energy Balance Experiment (MicroWEX-11): from April 25, 2012, through December 6, 2012 (ufl.edu)

Field Observations During the Tenth Microwave Water and Energy Balance Experiment (MicroWEX-10): from March 1, 2011 through January 5, 2012

For accurate weather prediction, accurate modeling of surface hydrological processes is very important. Most current models capture the biophysics of moisture and energy transport and of crop growth and development pretty well. However, model estimates of soil moisture in the root zone diverge from reality due to accumulated errors in initialization, forcings, and computation. Remotely sensed microwave observations can be assimilated into these models to improve root zone soil moisture and crop yield estimates. This 100-page report describes the observations conducted during a season-long experiment in elephant grass and sweet corn using active and passive microwave observations. Published by the UF Department of Agricultural and Biological Engineering, April 2015. (Photo: J. Casanova, UF) AE512/AE512: Field Observations During the Tenth Microwave Water and Energy Balance Experiment (MicroWEX-10): from March 1, 2011 through January 5, 2012 (ufl.edu)

Experimental investigation on diesel engine’s waste heat capacity under mapping characteristics

Waste heat recovery for internal combustion engine (ICE) has been considered as an important strategy to improve efficiency and promote fuel economy, thus alleviating the problems of energy shortage and environmental pollution. This paper investigates the characteristics of various kinds of waste heat energy, namely, waste heat in exhaust, cooling water and charge air, over the engine’s whole operating region. Based on the energy balance experiments, the energy distribution of a conventional heavy-duty diesel engine is obtained under mapping characteristics. According to exergy analysis, the energy recovery potential for waste heat is studied as well. The experimental results indicate that exhaust energy increases with engine speed and load, while cooling water energy is more sensitive to load, especially at low and middle speed. Charge air energy, on the other hand, mainly counts on speed rather than load. Exhaust energy possesses the highest recovery potential in terms of both quantity and quality. Through waste heat recovery, a dramatic improvement in engine efficiency is achievable, actually, the maximum value can amount to 60% or even more.

Spectra and cospectra of turbulence in an internal boundary layer over a heterogeneously irrigated cotton field

During the Energy Balance Experiment, patch-to-patch irrigation generated gradients in soil moisture in a north-south oriented cotton field. An internal boundary layer (IBL) developed as a result of strong horizontal advection from relatively dry upstream patches to relatively wet downstream patches associated with the prevailing northerly winds. This generated large eddies of multiple sizes, which had significant influences on the structure of turbulence in the IBL. The power spectra and cospectra of wind speed, temperature, humidity, and energy fluxes measured at two heights within the IBL are presented and used to investigate the influence of the IBL on surface layer turbulence. The spectra and cospectra were greatly enhanced by external disturbances at low frequencies. The peak frequencies of these disturbances did not change with height. The spectra and cospectra typically converged and were parallel to the Kansas spectrum at high frequencies (in the inertial subrange). A clear gap in the spectra of horizontal wind velocity existed at intermediate frequencies when the surface layer was stable. The results indicate that large eddies that originated in the upstream convective boundary layer had considerable impacts on the spectra and cospectra of surface layer turbulence. The influence of these large eddies was greater (1) when the IBL was well-developed in the near surface layer than when the IBL did not exist, (2) at higher levels than at lower levels, and (3) when the atmospheric surface layer (ASL) was unstable than when the ASL was stable. The length scales of these large eddies were consistent with the dominant scales of surface heterogeneity at the experiment site.