scholarly journals Field Results from a Second-Generation Ocean/Lake Surface Contact Heat Flux, Solar Irradiance, and Temperature Measurement Instrument—The Multisensor Float

2007 ◽  
Vol 24 (5) ◽  
pp. 856-876 ◽  
Author(s):  
J. P. Boyle
Keyword(s):  
Heat Flux ◽  
Water Temperature ◽  
Temperature Measurement ◽  
Solar Irradiance ◽  
Second Generation ◽  
Flux Measurement ◽  
Eddy Correlation ◽  
Near Surface ◽  
Surface Contact ◽  
Good Agreement

Abstract This paper describes results from two field programs that support development of a wave-following surface contact multisensor float (MSF) designed to simultaneously measure net surface heat flux, net solar irradiance, and water temperature. The results reported herein compare measurements from a second-generation design (circa 1998) against directly measured radiative fluxes as well as turbulent fluxes derived using both eddy correlation and bulk aerodynamic methods. The reference flux data are collected using instrumented towers, buoys, and research vessels. Comparisons show that MSF net surface fluxes and net solar irradiance are in generally good agreement with values that are measured or derived using standard instruments and methods, having root-mean-square differences less than approximately 15%. MSF near-surface bulk water temperature measurement shows good agreement with similar measurements from a drifting buoy. MSF measurement of water surface temperature is not definitively determined, although results suggest it may be a good measure of skin temperature at night. MSF flux measurement occurs from within the aqueous conductive sublayer and so does not use turbulence models or parameterizations. At this time, results are most reliable in low wind conditions (2 m s−1 ≤ U10 ≤ 7 m s−1) and relatively calm seas. In higher winds and more active seas, the imperfect surface drifting and wave-following characteristics of the second-generation system limit its performance. More fundamentally, perturbation to the aqueous conductive sublayer and modification of near-surface turbulence structure by the MSF may also limit flux measurement accuracy under certain conditions.

scholarly journals Components of near-surface energy balance derived from satellite soundings – Part 2: Latent heat flux

2010 ◽  
Vol 10 (6) ◽  
pp. 14417-14443 ◽  
Author(s):  
K. Mallick ◽  
A. Jarvis ◽  
G. Wohlfahrt ◽  
C. Gough ◽  
T. Hirano ◽  
...  
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Bowen Ratio ◽  
Atmospheric Infrared Sounder ◽  
Near Surface ◽  
Available Energy ◽  
Surface Latent Heat Flux ◽  
Global Surface ◽  
Good Agreement

Abstract. This paper introduces a new method for recovering global fields of latent heat flux. The method focuses on specifying Bowen ratio fields through exploiting air temperature and vapour pressure measurements obtained from infra-red soundings of the AIRS (Atmospheric Infrared Sounder) sensor onboard the NASA-Aqua platform. Through combining these Bowen ratio retrievals with satellite surface net available energy data we have specified estimates of global surface latent heat flux at the 1° by 1° scale. These estimates were evaluated against data from 30 terrestrial tower flux sites covering a broad spectrum of biomes. Taking monthly average 13:30 local time (LT) data for 2003, this revealed a relatively good agreement between the satellite and tower measurements of latent heat flux, with a pooled root mean square deviation of 79 W m−2, and no significant bias. The results show particular promise for this approach under warm, moist conditions, but weaknesses under arid or semi-arid conditions subject to high radiative loads.

scholarly journals The Impact of Utility-Scale Photovoltaics Plant on Near Surface Turbulence Characteristics in Gobi Areas

Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 18
Author(s):  
Junxia Jiang ◽  
Xiaoqing Gao ◽  
Bolong Chen
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Reference Site ◽  
Eddy Correlation ◽  
Surface Boundary ◽  
Near Surface ◽  
Turbulence Characteristics ◽  
Surface Turbulence ◽  
Utility Scale ◽  
The Impact

With the rapid deployment of utility-scale photovoltaic (PV) plants, the impact of PV plants on the environment is a new concern of the scientific and social communities. The exchange of sensible and latent heat energy and mass between land and air in PV plants is crucial to understanding its impact. It is known that the near surface turbulence characteristics rule the exchange. Therefore, it is essential for understanding the impact to study the characteristics of near surface turbulence. However, it is not well recognized. Turbulent fluxes and strength characteristics for the PV plant and the adjacent reference site in the Xinjiang Gobi area were investigated in this study. Various surface layer parameters including friction velocity, stability parameter, momentum flux, and turbulent flux were calculated using eddy correlation system. Results indicate that compared to the reference site, near the surface boundary layer was more unstable during the daytime due to the stronger convection heating, while it was more stable at night in the PV plant. In the PV plant, Iu was weakened and Iv was strengthened during the daytime, and Iu and Iv were all weakened at night, while Iw was strengthened across the whole day. The significant difference between Iu and Iv in the PV plant indicated that the horizontally turbulence strengths were affected by the plant layout. The turbulent kinetic energy of the PV plant was lower than the reference site and the momentum in the PV plant was higher than the reference site, especially during the daytime. Compared to the reference site, the PV plant had a higher sensible heat flux and less latent heat flux. The turbulent components of wind followed the 1/3 power law in the unstable conditions and stable conditions in the PV plant and the reference site.

scholarly journals Time series analysis of water surface temperature and heat flux components in the Itumbiara Reservoir (GO), Brazil

2012 ◽  
Vol 23 (3) ◽  
pp. 245-259 ◽  
Author(s):  
Enner Herenio de Alcântara ◽  
José Luiz Stech ◽  
João Antônio Lorenzzetti ◽  
Evlyn Márcia Leão de Moraes Novo
Keyword(s):  
Heat Flux ◽  
Time Series ◽  
Surface Water ◽  
Surface Temperature ◽  
Water Temperature ◽  
Water Surface ◽  
Surface Water Temperature ◽  
Water Surface Temperature ◽  
Cyclical Pattern ◽  
Good Agreement

AIM: Water temperature plays an important role in ecological functioning and in controlling the biogeochemical processes of the aquatic system. Conventional water quality monitoring is expensive and time consuming. It is particularly challenging for large water bodies. Conversely, remote sensing can be considered a powerful tool to assess important properties of aquatic systems because it provides synoptic and frequent data acquisition over large areas. The objective of this study was to analyze time series of surface water temperature and heat flux to advance the understanding of temporal variations in a hydroelectric reservoir. METHOD: MODIS water-surface temperature (WST) level 2, 1 km nominal resolution data (MOD11L2, version 5) were used. All available clear-sky MODIS/Terra images from 2003 to 2008 were used, resulting in a total of 786 daytime and 473 nighttime images. Time series of surface water temperature was obtained computing the monthly mean in a 3×3 window of three reservoir selected sites: 1) near the dam, 2) at the centre of the reservoir and 3) in the confluence of the rivers. In-situ meteorological data from 2003 to 2008 were used to calculate surface energy budget time series. Cross-wavelet, coherence and phase analysis were carried out to compute the correlation between daytime and nighttime surface water temperatures and the computed heat fluxes. RESULTS: The monthly mean of the day-time WST shows lager variability than the night-time WST. All time series (daytime and nighttime) have a cyclical pattern, passing for a minimum (June - July) and a maximum (December and January). Fourier and the Wavelet Analysis were applied to analyze this cyclical pattern. The daytime time series, presents peaks in 4.5, 6 12 and 36 months and the nighttime WST shows the highest spectral density at 12, 6, 3 and 2 months. The multiple regression analysis shows that for daytime WST, the heat flux terms explain 89% of the annual variation (RMS = 0.89 °C, p < 0.0013). For nighttime, the heat flux terms explain 94% (RMS = 0.53 °C, p < 0.0002). CONCLUSION: The daytime WST and shortwave radiation presents a good agreement for periods of 6 (with shortwave retarded) and 12 months (with shortwave advanced); For nighttime WST and longwave the good agreement is present for 1, 3, 6 and 12 months, all with longwave advanced in relation to WST.

scholarly journals Eddy Covariance flux measurements with a weight-shift microlight aircraft

2012 ◽  
Vol 5 (2) ◽  
pp. 2591-2643 ◽  
Author(s):  
S. Metzger ◽  
W. Junkermann ◽  
M. Mauder ◽  
F. Beyrich ◽  
K. Butterbach-Bahl ◽  
...  
Keyword(s):  
Heat Flux ◽  
Eddy Covariance ◽  
Sensible Heat Flux ◽  
Flux Measurement ◽  
Wind Measurement ◽  
Airborne Measurements ◽  
Weight Shift ◽  
Flux Measurements ◽  
Good Agreement

Abstract. The objective of this study is to assess the feasibility and quality of Eddy-Covariance flux measurements from a weight-shift microlight aircraft (WSMA). Firstly we investigate the precision of the wind measurement (σu,v≤ 0.09 m s−1, σw = 0.04 m s−1), the lynchpin of flux calculations from aircraft. From here the smallest resolvable changes in friction velocity (0.02 m s−1), and sensible- (5 W m−2) and latent (3 W m−2) heat flux are estimated. Secondly a seven-day flight campaign was performed near Lindenberg (Germany). Here we compare measurements of wind, temperature, humidity and respective fluxes between a tall tower and the WSMA. The maximum likelihood functional relationship (MLFR) between tower and WSMA measurements considers the random error in the data, and shows very good agreement of the scalar averages. The MLFRs for standard deviations (SDs, 2–34%) and fluxes (17–21%) indicate higher estimates of the airborne measurements compared to the tower. Considering the 99.5% confidence intervals the observed differences are not significant, with exception of the temperature SD. The comparison with a large-aperture scintillometer reveals lower sensible heat flux estimates at both, tower (−40–−25%) and WSMA (−25–0%). We relate the observed differences to (i) inconsistencies in the temperature and wind measurement at the tower and (ii) the measurement platforms differing abilities to capture contributions from non-propagating eddies. These findings encourage the use of WSMA as a low price and highly versatile flux measurement platform.

A Study on Contribution of the Advective Heat Flux to the Energy Closure near the Land Surface in the Zoige Alpine Wetland

2020 ◽  
Author(s):  
Jun Wen ◽  
Xuancheng Lu ◽  
Yue Yang ◽  
Hui Tian ◽  
Wenhui Liu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Land Surface ◽  
Energy Balance Equation ◽  
Eddy Correlation ◽  
Underlying Surface ◽  
Closure Rate ◽  
Near Surface ◽  
Alpine Wetland ◽  
The Difference ◽  
Flux Energy

&lt;p&gt;The energy non-closure near the land surface has been a key topic in the land surface processes research. &amp;#160;The energy closure rate is still not high even after considering heat storage and photosynthesis energy consumption, while the contribution of advective energy to the closure rate needs to be considered further under the non-uniform underlying surface. In this paper, the advective energy caused by thermal heterogeneity of underlying surface is calculated by using the energy budget data collected from the Flower-Lake observation site in the Zoige Alpine Wetland in 2017, and the contribution of thermal advection to energy closure near the ground is estimated. The result shows: In summer of 2017, the maximum value of the advective heat flux was 23.8w/m2 at the Zoige alpine wetland. When the contribution of advective heat flux is introduced into the energy balance equation, the energy closure rate increases from 72.0% to 79.4%. With considering the contribution of horizontal heat transfer, it has a certain effect on improving energy closure rate for the flat terrain and thermal inhomogeneous underlying surface. The near surface thermal inhomogeneity leads to the accumulation of heat, which is the basic reason for the heat advection to affect the energy closure rate, and also an important reason for the difference between the wetland characteristics of water and heat exchange of the wetland with the other regions.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Key &lt;/strong&gt;&lt;strong&gt;words&lt;/strong&gt;&lt;strong&gt;&amp;#65306;&lt;/strong&gt;Alpine wetland; eddy correlation; advective&amp;#160;heat flux; energy closure&amp;#160;rate; inhomogeneous&amp;#160;land&amp;#160;surface&lt;/p&gt;

Estimating the Wall Heat Flux of Unsteady Conjugated Forced Convection Between Two Corotating Disks Using an Inverse Solution Scheme

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
David T. W. Lin ◽  
Hung Yi Li ◽  
Wei Mon Yan
Keyword(s):  
Heat Flux ◽  
Forced Convection ◽  
Boundary Surface ◽  
Temperature Sensors ◽  
Inverse Solution ◽  
Wall Heat Flux ◽  
Unknown Boundary ◽  
Measured Temperature ◽  
Solution Scheme ◽  
Good Agreement

An inverse solution scheme based on the conjugate gradient method with the minimization of the object function is presented for estimating the unknown wall heat flux of conjugated forced convection flows between two corotating disks from temperature measurements acquired within the flow field. The validity of the proposed approach is demonstrated via the estimation of three time- and space-dependent heat flux profiles. A good agreement is observed between the estimated results and the exact solution in every case. In general, the accuracy of the estimated results is found to improve as the temperature sensors are moved closer to the unknown boundary surface and the error in the measured temperature data is reduced.

scholarly journals Correction of Eddy Covariance Based Crop ET Considering the Heat Flux Source Area

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 281
Author(s):  
Stuart L. Joy ◽  
José L. Chávez
Keyword(s):  
Heat Flux ◽  
Eddy Covariance ◽  
Agricultural Land ◽  
Flux Measurement ◽  
Source Area ◽  
Mean Bias Error ◽  
Bias Error ◽  
Crop Water ◽  
The Past ◽  
Measurement Results

Eddy covariance (EC) systems are being used to measure sensible heat (H) and latent heat (LE) fluxes in order to determine crop water use or evapotranspiration (ET). The reliability of EC measurements depends on meeting certain meteorological assumptions; the most important of such are horizontal homogeneity, stationarity, and non-advective conditions. Over heterogeneous surfaces, the spatial context of the measurement must be known in order to properly interpret the magnitude of the heat flux measurement results. Over the past decades, there has been a proliferation of ‘heat flux source area’ (i.e., footprint) modeling studies, but only a few have explored the accuracy of the models over heterogeneous agricultural land. A composite ET estimate was created by using the estimated footprint weights for an EC system in the upwind corner of four fields and separate ET estimates from each of these fields. Three analytical footprint models were evaluated by comparing the composite ET to the measured ET. All three models performed consistently well, with an average mean bias error (MBE) of about −0.03 mm h−1 (−4.4%) and root mean square error (RMSE) of 0.09 mm h−1 (10.9%). The same three footprint models were then used to adjust the EC-measured ET to account for the fraction of the footprint that extended beyond the field of interest. The effectiveness of the footprint adjustment was determined by comparing the adjusted ET estimates with the lysimetric ET measurements from within the same field. This correction decreased the absolute hourly ET MBE by 8%, and the RMSE by 1%.

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