scholarly journals Surface Energy Components and Land Characteristics of a Rice Paddy

2007 ◽  
Vol 46 (11) ◽  
pp. 1879-1900 ◽  
Author(s):  
Jeng-Lin Tsai ◽  
Ben-Jei Tsuang ◽  
Po-Sheng Lu ◽  
Ming-Hwi Yao ◽  
Yuan Shen
Keyword(s):  
Air Quality ◽  
Surface Energy ◽  
Bowen Ratio ◽  
Rice Paddy ◽  
Carbon Dioxide Flux ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Canopy Resistance ◽  
Rice Paddies ◽  
Quality Models

Abstract Many meteorological and air-quality models require land characteristics as inputs. A field experiment was conducted to study the surface energy budget of a rice paddy in Taiwan. During the day, the energy balance ratio measured by an eddy covariance (EC) system was found to be 95% after considering the photosynthetic and local advected heat fluxes. The observations by the EC system suggest that the Bowen ratio was about 0.18 during the daytime. The EC system also measured the daytime absorbed carbon dioxide flux. The equivalent photosynthetic energy flux was about 1% of the net solar radiation. A reference table describing the land characteristics of rice paddies for use in meteorological and air-quality models is listed that shows that the albedo and the Bowen ratio measured over rice paddies were lower than those listed in many state-of-the-art models. This study proposes simulating latent heat flux by assigning proper values for canopy resistance rather than by assigning constant values for Bowen ratio or surface moisture availability. The diurnal pattern of the canopy resistance of the rice paddy was found to be “U” shaped. Daytime canopy resistance was observed to be 87 s m−1, and a high canopy resistance (∼900 s m−1) should be assigned during nighttime periods.

scholarly journals Estimating the Bowen Ratio for Application in Air Quality Models by Integrating a Simplified Analytical Expression with Measurement Data

2016 ◽  
Vol 55 (4) ◽  
pp. 1041-1048 ◽  
Author(s):  
K. M. Lin ◽  
J. Y. Juang ◽  
Y.-W. Shiu ◽  
L. F. W. Chang
Keyword(s):  
Heat Flux ◽  
Air Quality ◽  
Solar Radiation ◽  
Latent Heat ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Ratio Method ◽  
Quality Models ◽  
Ratio Equation ◽  
Taylor Method

AbstractIn air quality models, daytime sensible and latent heat fluxes are important factors that influence atmospheric stability. These heat fluxes originate from heat that is generated from solar radiation and is then released from the earth’s surface. Different climates and surface conditions may lead to varying heat flux distributions. Because latent heat flux is influenced by both solar radiation and plant evapotranspiration, it is often difficult to estimate. The objective of this study was to apply thermodynamic concepts to determine an equation that could be used to estimate the Bowen ratio in the absence of latent and sensible heat fluxes. This study showed that, using two meteorological parameters (i.e., absolute temperature and relative humidity), the Bowen ratio for the climate in Taiwan could be obtained and then used to estimate sensible and latent heat fluxes in a series of equations. Furthermore, the approach’s applicability was determined by testing the sensitivities of parameters used in the Bowen ratio equation. A comparison of results determined through the Priestly–Taylor and Penman–Monteith methods with meteorological data for Yilan and Chiayi counties, Taiwan, for the 2006 summer and winter is performed. The results of this study showed that, among the simulated latent heat fluxes in the two study areas, the values estimated using the Penman–Monteith method were the largest, followed by those estimated using the Priestly–Taylor method. Values estimated using the Bowen ratio method were the smallest. Predictions generated by the proposed Bowen ratio equation correlated with those generated by the other models; however, the values estimated with the Priestly–Taylor method were closest to the simulated values.

scholarly journals Analysing surface energy balance closure and partitioning over a semi-arid savanna FLUXNET site in Skukuza, Kruger National Park, South Africa

2016 ◽  
Author(s):  
Nobuhle P. Majozi ◽  
Chris M. Mannaerts ◽  
Abel Ramoelo ◽  
Renaud Mathieu ◽  
Alecia Nickless ◽  
...  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Latent Heat ◽  
Surface Energy Balance ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Radiation Budget ◽  
Energy Balance Closure ◽  
Flux Tower ◽  
The Impact

Abstract. Flux tower sites and data are in great demand to provide essential terrestrial climate, water and radiation budget information needed for environmental monitoring and evaluation of climate change impacts on ecosystems and society in general. They are also intended for calibration and validation of satellite-based earth observation and monitoring efforts, such as for example assessment of evapotranspiration from land and vegetation surfaces using surface energy balance approaches. Surface energy budget methods for ET estimation rely to a large extend on the basic assumption of a surface energy balance closure, assuming the full conversion of net solar radiation reaching the land surface into soil heat conduction and turbulent fluxes, i.e. the sensible (or convection) and latent heat components of the energy balance. Evapotranspiration is the conversion of the latent heat exchange fraction of the balance. In this paper, the Skukuza flux tower data were analysed in order to verify their use for validation of satellite–based evapotranspiration methods, under development in South Africa.Data series from 2000 until 2014 were used in the analysis. The energy balance ratio (EBR) concept, defined as the ratio between the sum of the turbulent convective and latent heat fluxes and radiation minus soil heat was used. At first typical diurnal patterns of EB partitioning were derived for four different seasons, well illustrating how this savannah-type biome responses to the weather conditions. Also the particular behaviour of the EB components during sunrise and sunset conditions, being important but usually neglected periods of energy transitions and inversions were noted and analysed. Annual estimates of the surface energy balance and its components were generated, including an evaluation of the balance closure. The seasonal variations were also investigated as well as the impact of nocturnal observations on the overall EB behaviour.

Observed Impact of Atmospheric Aerosols on the Surface Energy Budget

2013 ◽  
Vol 17 (14) ◽  
pp. 1-22 ◽  
Author(s):  
Allison L. Steiner ◽  
Dori Mermelstein ◽  
Susan J. Cheng ◽  
Tracy E. Twine ◽  
Andrew Oliphant
Keyword(s):  
Heat Flux ◽  
Surface Energy ◽  
Latent Heat ◽  
Atmospheric Aerosols ◽  
Sensible Heat Flux ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Environmental Drivers ◽  
Sensible Heat

Abstract Atmospheric aerosols scatter and potentially absorb incoming solar radiation, thereby reducing the total amount of radiation reaching the surface and increasing the fraction that is diffuse. The partitioning of incoming energy at the surface into sensible heat flux and latent heat flux is postulated to change with increasing aerosol concentrations, as an increase in diffuse light can reach greater portions of vegetated canopies. This can increase photosynthesis and transpiration rates in the lower canopy and potentially decrease the ratio of sensible to latent heat for the entire canopy. Here, half-hourly and hourly surface fluxes from six Flux Network (FLUXNET) sites in the coterminous United States are evaluated over the past decade (2000–08) in conjunction with satellite-derived aerosol optical depth (AOD) to determine if atmospheric aerosols systematically influence sensible and latent heat fluxes. Satellite-derived AOD is used to classify days as high or low AOD and establish the relationship between aerosol concentrations and the surface energy fluxes. High AOD reduces midday net radiation by 6%–65% coupled with a 9%–30% decrease in sensible and latent heat fluxes, although not all sites exhibit statistically significant changes. The partitioning between sensible and latent heat varies between ecosystems, with two sites showing a greater decrease in latent heat than sensible heat (Duke Forest and Walker Branch), two sites showing equivalent reductions (Harvard Forest and Bondville), and one site showing a greater decrease in sensible heat than latent heat (Morgan–Monroe). These results suggest that aerosols trigger an ecosystem-dependent response to surface flux partitioning, yet the environmental drivers for this response require further exploration.

scholarly journals Competing Effects of Vegetation on Summer Temperature in North Korea

2021 ◽  
Author(s):  
Jieun Oh ◽  
Eungul Lee
Keyword(s):  
Surface Energy ◽  
North Korea ◽  
Large Scale ◽  
Vegetation Index ◽  
Bowen Ratio ◽  
Summer Temperature ◽  
Heat Fluxes ◽  
Cooling Effect ◽  
Western Region ◽  
The Western Region

Abstract Vegetation reduction could affect regional climate by perturbing the surface energy and moisture balances via changes in albedo and evapotranspiration. However, it is unknown whether vegetation effects on climate occur in North Korea, where a severe reduction in forest cover has been observed. This study aimed to identify the biogeophysical processes in vegetation and climate interactions in North Korea, using Normalized Difference Vegetation Index (NDVI) and climate reanalysis data over the period 1982‒2015. As per the NDVI regression trend results, the highest rates of decreasing NDVI were detected in the western region of North Korea during summer. Based on the detrended correlation analysis of NDVI with surface energy variables at each grid point, including solar radiation, sensible and latent heat fluxes, Bowen ratio, and temperature, we identified a cooling effect of vegetation in the western region (with lower NDVI and lower elevation), but a warming effect of vegetation in the northern region (with higher NDVI and higher elevation). The different biogeophysical effects were induced by the increasing and decreasing Bowen ratio with increasing vegetation in the northern and western regions, respectively. In the western region of North Korea, where large-scale human-induced forest loss has been observed, the increasing summer temperature caused by the decreasing cooling effect of vegetation would be up to 1.5 ℃ by the end of this century, if the current rate of deforestation continues. Thus, we urgently suggest that sustainable management and restoration of forests are needed in North Korea, which is among the countries most vulnerable to climate change now and in the future.

scholarly journals Near-surface climate and surface energy budget of Larsen C ice shelf, Antarctic Peninsula

2012 ◽  
Vol 6 (2) ◽  
pp. 353-363 ◽  
Author(s):  
P. Kuipers Munneke ◽  
M. R. van den Broeke ◽  
J. C. King ◽  
T. Gray ◽  
C. H. Reijmer
Keyword(s):  
Surface Energy ◽  
Antarctic Peninsula ◽  
Energy Budget ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Shortwave Radiation ◽  
Sensible Heat ◽  
Ice Shelf ◽  
Near Surface ◽  
The Impact

Abstract. Data collected by two automatic weather stations (AWS) on the Larsen C ice shelf, Antarctica, between 22 January 2009 and 1 February 2011 are analyzed and used as input for a model that computes the surface energy budget (SEB), which includes melt energy. The two AWSs are separated by about 70 km in the north–south direction, and both the near-surface meteorology and the SEB show similarities, although small differences in all components (most notably the melt flux) can be seen. The impact of subsurface absorption of shortwave radiation on melt and snow temperature is significant, and discussed. In winter, longwave cooling of the surface is entirely compensated by a downward turbulent transport of sensible heat. In summer, the positive net radiative flux is compensated by melt, and quite frequently by upward turbulent diffusion of heat and moisture, leading to sublimation and weak convection over the ice shelf. The month of November 2010 is highlighted, when strong westerly flow over the Antarctic Peninsula led to a dry and warm föhn wind over the ice shelf, resulting in warm and sunny conditions. Under these conditions the increase in shortwave and sensible heat fluxes is larger than the decrease of net longwave and latent heat fluxes, providing energy for significant melt.

scholarly journals Observations of daytime surface energy balance in cloudy tropical conditions at Ile-Ife, Nigeria

MAUSAM ◽  
2022 ◽  
Vol 53 (3) ◽  
pp. 359-366
Author(s):  
O. O. JEGEDE
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Cloud Amount ◽  
Soil Surface ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Average Value ◽  
Tropical Conditions

Daytime energy balance at the surface in cloudy tropical conditions for Ile-Ife; Nigeria (7°33'N, 4°34'E) is investigated based on a series of micrometeorological measurements performed in October/November of 1998. For the humid environment that it is (mixing ratio, 17 -25 g / kg), magnitudes of the latent heat flux were much larger than the values for the sensible heat. Of the morning hours the average value for the Bowen ratio obtained was 0.36, while for the afternoons it was 0.74. As the soil surface became dried up in the afternoons, magnitudes of both sensible heat and ground heat fluxes were found to be comparable.   Fluctuations in the magnitudes of the terms of the surface energy balance correlated well to the cloud amount, degree of soil wetness, air temperature and humidity. But of all these factors, the variation in the amount of cloudiness appeared most dominant.

scholarly journals Atmospheric Drivers of Melt on Larsen C Ice Shelf: Surface Energy Budget Regimes and the Impact of Foehn

2021 ◽  
Author(s):  
Andy Elvidge ◽  
Peter Kuipers Munneke ◽  
John King ◽  
Ian Renfrew ◽  
Ella Gilbert
Keyword(s):  
Wind Speed ◽  
Surface Energy ◽  
Energy Budget ◽  
Model Simulation ◽  
Atmospheric Model ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Turbulent Heat ◽  
Ice Shelf ◽  
The Impact

<p>Recent ice shelf retreat on the east coast of the Antarctic Peninsula has been principally attributed to atmospherically driven melt. However, previous studies on the largest of these ice shelves—Larsen C—have struggled to reconcile atmospheric forcing with observed melt. This study provides the first comprehensive quantification and explanation of the atmospheric drivers of melt across Larsen C, using 31‐months' worth of observations from Cabinet Inlet, a 6‐month, high‐resolution atmospheric model simulation and a novel approach to ascertain the surface energy budget (SEB) regime. The dominant meteorological controls on melt are shown to be the occurrence, strength, and warmth of mountain winds called foehn. At Cabinet Inlet, foehn occurs 15% of the time and causes 45% of melt. The primary effect of foehn on the SEB is elevated turbulent heat fluxes. Under typical, warm foehn conditions, this means elevated surface heating and melting, the intensity of which increases as foehn wind speed increases. Less commonly—due to cooler‐than‐normal foehn winds and/or radiatively warmed ice—the relationship between wind speed and net surface heat flux reverses. This explains the seemingly contradictory results of previous studies. In the model, spatial variability in cumulative melt across Larsen C is largely explained by foehn, with melt maxima in inlets reflecting maxima in foehn wind strength. However, most accumulated melt (58%) occurs due to solar radiation in the absence of foehn. A broad north‐south gradient in melt is explained by the combined influence of foehn and non‐foehn conditions.</p>

scholarly journals Near-surface climate and surface energy budget of Larsen C ice shelf, Antarctic Peninsula

2011 ◽  
Vol 5 (5) ◽  
pp. 2665-2697
Author(s):  
P. Kuipers Munneke ◽  
M. R. van den Broeke ◽  
J. C. King ◽  
T. Gray ◽  
C. H. Reijmer
Keyword(s):  
Surface Energy ◽  
Antarctic Peninsula ◽  
Energy Budget ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Shortwave Radiation ◽  
Sensible Heat ◽  
Ice Shelf ◽  
Near Surface ◽  
The Impact

Abstract. Data collected by two automatic weather stations (AWS) on the Larsen C ice shelf, Antarctica, between 22 January 2009 and 1 February 2011 are analyzed and used as input for a model that computes the surface energy budget (SEB), including melt energy. The two AWSs are separated by about 70 km in the north-south direction, and both the near-surface meteorology and the SEB show similarities, although small differences in all components (most notably the melt flux) can be seen. The impact of subsurface absorption of shortwave radiation on melt and snow temperature is significant, and discussed. In winter, longwave cooling of the surface is entirely compensated by a downward turbulent transport of sensible heat. In summer, the positive net radiative flux is compensated by melt, and quite frequently by upward turbulent diffusion of heat and moisture, leading to sublimation and weak convection over the ice shelf. The month of November 2010 is highlighted, when strong westerly flow over the Antarctic Peninsula led to a dry and warm föhn wind over the ice shelf, resulting in warm and sunny conditions. Under these conditions the increase in shortwave and sensible heat fluxes is larger than the reduction of net longwave and latent heat fluxes, providing energy for significant melt.

scholarly journals Environmental Controls on the Surface Energy Budget over a Large Southern Inland Water in the United States: An Analysis of One-Year Eddy Covariance Flux Data

2012 ◽  
Vol 13 (6) ◽  
pp. 1893-1910 ◽  
Author(s):  
Heping Liu ◽  
Qianyu Zhang ◽  
Gordon Dowler
Keyword(s):  
Surface Energy ◽  
Eddy Covariance ◽  
Large Scale ◽  
The United States ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Vertical Temperature ◽  
Mechanical Mixing ◽  
Air Masses ◽  
Environmental Controls

Abstract The authors analyzed the surface energy fluxes that were measured by an eddy covariance system over the Ross Barnett Reservoir in Mississippi for a 1-yr period in 2008. On a monthly basis over the course of the year, positive vertical temperature and vapor pressure differences were observed, though negative vertical temperature differences occurred occasionally during some short periods when overwater air masses were warmer than the water surface. Consequently, the unstable atmospheric surface layer (ASL) and sufficient mechanical mixing led to positive sensible H and latent λE heat fluxes. The quantities H and λE were distinctively out of phase with the net radiation Rn. The H and λE from the water to the ASL was still substantial on nights with a negative Rn and in winter when Rn was very small. From February to August, approximately 60%–91% of the Rn was used for H and λE, with the remainder being stored in the water. Fueled by the previously stored heat in the water, H and λE exceeded Rn by almost 3 times from September to January. Nighttime evaporation represented a large loss of water (i.e., λE = 82.8 W m−2 at night versus 91.4 W m−2 during the daytime). Intraseasonal and seasonal variations in H and λE were strongly affected by frequent passages of large-scale air masses that were brought in by different synoptic weather systems (e.g., cyclones or anticyclones). The authors’ analysis suggested that this southern reservoir responded to atmospheric forcings on both diurnal and seasonal scales in the same ways as northern lakes of comparable sizes and depths.

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