scholarly journals Estimation of Water Stress on Rice Crop Using Ecological Parameters.

2019 ◽  
Vol 01 (01) ◽  
Author(s):  
Muhammad Saifullah ◽  
Bilal Islam ◽  
Saif-ul Rehman ◽  
Muhmmad Shoaib ◽  
Ehsan ul Haq ◽  
...  
Keyword(s):  
Heat Flux ◽  
Water Stress ◽  
Water Scarcity ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Rice Crop ◽  
Growth Stages ◽  
Sensible Heat ◽  
Area Index ◽  
Ecological Parameters

About half of world’s population intake rice as a staple food. As being water baby, rice need surplus of water to get targeted yield. Water scarcity has become a global issue therefore it has become a need to enhance the rice yield with reduced amount of water. In this research we used ecological parameters e.g., temperature, pressure, actual vapor pressure, sunshine hours and the extraterrestrial radiation to compute net radiations, ground and sensible heat fluxes on daily basis. Net shortwave radiations were observed as 23087 w/m2 in comparison to net longwave radiations which were 4387 w/m2 for the complete Rice Growth Period (RGP). The soil heat flux Go was observed as 3104 w/m2. Go was observed dependent upon the Leaf Area Index (LAI) with inverse relationship between them. Sensible heat flux (H) was measured as 1771 w/m2 throughout the RGP. H was observed dependent upon net radiations with a direct relationship between them. Rn, Go and H were used as input parameters to compute water stress which determines the excess of water in early growth stages of rice crop and water scarcity in the ripening stage. The flow of methodology is easily applicable at domestic level to determine water stress in rice fields.

scholarly journals Disentangling the response of forest and grassland energy exchange to heatwaves under idealized land–atmosphere coupling

2014 ◽  
Vol 11 (4) ◽  
pp. 5969-5995
Author(s):  
C. C. van Heerwaarden ◽  
A. J. Teuling
Keyword(s):  
Heat Wave ◽  
Heat Waves ◽  
Dynamic Properties ◽  
Sensible Heat Flux ◽  
Early Morning ◽  
Stomatal Resistance ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Area Index ◽  
Wave Conditions

Abstract. This study investigates the difference in land–atmosphere interactions between grassland and forest during typical heat wave conditions in order to understand the controversial results of Teuling et al. (2010) (T10, hereafter), who have found the systematic occurrence of higher sensible heat fluxes over forest than over grassland during heat wave conditions. With a simple, but accurate coupled land–atmosphere model, we are able to reproduce the findings of T10 for both normal summer and heat wave conditions, and to carefully explore the sensitivity of the coupled land–atmosphere system to changes in incoming radiation and early-morning temperature. Our results emphasize the importance of fast processes during the onset of heat waves, since we are able to explain the results of T10 without having to take into account changes in soil moisture. In order to disentangle the contribution of differences in several static and dynamic properties between forest and grassland, we have performed an experiment in which new land use types are created that are equal to grassland, but with one of its properties replaced by that of forest. From these, we conclude that the closure of stomata in the presence of dry air is by far the most important process in creating the different behavior of grassland and forest during the onset of a heat wave. However, we conclude that for a full explanation of the results of T10 also the other properties (albedo, roughness and the ratio of minimum stomatal resistance to leaf-area index) play an important, but indirect role; their influences mainly consist of strengthening the feedback that leads to the closure of the stomata by providing more energy that can be converted into sensible heat. The model experiment also confirms that, in line with the larger sensible heat flux, higher atmospheric temperatures occur over forest.

scholarly journals Modeling canopy-induced turbulence in the Earth system: a unified parameterization of turbulent exchange within plant canopies and the roughness sublayer (CLM-ml v0)

2017 ◽  
Author(s):  
Gordon B. Bonan ◽  
Edward G. Patton ◽  
Ian N. Harman ◽  
Keith W. Oleson ◽  
John J. Finnigan ◽  
...  
Keyword(s):  
Heat Flux ◽  
Friction Velocity ◽  
Sensible Heat Flux ◽  
Roughness Sublayer ◽  
Sensible Heat ◽  
Area Index ◽  
Community Land Model ◽  
Diurnal Range ◽  
Radiative Temperature ◽  
Canopy Model

Abstract. Land surface models used in climate models neglect the roughness sublayer and parameterize within-canopy turbulence in an ad hoc manner. We implemented a roughness sublayer turbulence parameterization in a multi-layer canopy model (CLM-ml v0) test if this theory provides a tractable parameterization extending from the ground through the canopy and the roughness sublayer. We compared the canopy model with the Community Land Model (CLM4.5) at 7 forest, 2 grassland, and 3 cropland AmeriFlux sites over a range of canopy height, leaf area index, and climate. The CLM4.5 has pronounced biases during summer months at forest sites in mid-day latent heat flux, sensible heat flux, and gross primary production, nighttime friction velocity, and the radiative temperature diurnal range. The new canopy model reduces these biases by introducing new physics. The signature of the roughness sublayer is most evident in sensible heat flux, friction velocity, and the diurnal cycle of radiative temperature. Within-canopy temperature profiles are markedly different compared with profiles obtained using Monin–Obukhov similarity theory, and the roughness sublayer produces cooler daytime and warmer nighttime temperatures. The herbaceous sites also show model improvements, but the improvements are related less systematically to the roughness sublayer parameterization in these short canopies. The multi-layer canopy with the roughness sublayer turbulence improves simulations compared with the CLM4.5 while also advancing the theoretical basis for surface flux parameterizations.

scholarly journals Comparison of turbulent structures and energy fluxes over exposed and debris-covered glacier ice

2020 ◽  
Vol 66 (258) ◽  
pp. 543-555 ◽  
Author(s):  
Lindsey Nicholson ◽  
Ivana Stiperski
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Similarity Theory ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Temperature Fields ◽  
Sensible Heat ◽  
Energy Fluxes ◽  
Glacier Surface ◽  
Debris Cover

AbstractWe present the first direct comparison of turbulence conditions measured simultaneously over exposed ice and a 0.08 m thick supraglacial debris cover on Suldenferner, a small glacier in the Italian Alps. Surface roughness, sensible heat fluxes (~20–50 W m−2), latent heat fluxes (~2–10 W m−2), topology and scale of turbulence are similar over both glacier surface types during katabatic and synoptically disturbed conditions. Exceptions are sunny days when buoyant convection becomes significant over debris-covered ice (sensible heat flux ~ −100 W m−2; latent heat flux ~ −30 W m−2) and prevailing katabatic conditions are rapidly broken down even over this thin debris cover. The similarity in turbulent properties implies that both surface types can be treated the same in terms of boundary layer similarity theory. The differences in turbulence between the two surface types on this glacier are dominated by the radiative and thermal contrasts, thus during sunny days debris cover alters both the local surface turbulent energy fluxes and the glacier component of valley circulation. These variations under different flow conditions should be accounted for when distributing temperature fields for modeling applications over partially debris-covered glaciers.

scholarly journals Urban signals in high-resolution weather and climate simulations: role of urban land-surface characterisation

2020 ◽  
Vol 142 (1-2) ◽  
pp. 701-728
Author(s):  
Denise Hertwig ◽  
Sue Grimmond ◽  
Margaret A. Hendry ◽  
Beth Saunders ◽  
Zhengda Wang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Land Cover ◽  
Sensible Heat Flux ◽  
Urban Land ◽  
Heat Fluxes ◽  
Anthropogenic Heat ◽  
Urban Surface ◽  
City Centre ◽  
Sensible Heat ◽  
Climate Simulations

Abstract Two urban schemes within the Joint UK Land Environment Simulator (JULES) are evaluated offline against multi-year flux observations in the densely built-up city centre of London and in suburban Swindon (UK): (i) the 1-tile slab model, used in climate simulations; (ii) the 2-tile canopy model MORUSES (Met Office–Reading Urban Surface Exchange Scheme), used for numerical weather prediction over the UK. Offline, both models perform better at the suburban site, where differences between the urban schemes are less pronounced due to larger vegetation fractions. At both sites, the outgoing short- and longwave radiation is more accurately represented than the turbulent heat fluxes. The seasonal variations of model skill are large in London, where the sensible heat flux in autumn and winter is strongly under-predicted if the large city centre magnitudes of anthropogenic heat emissions are not represented. The delayed timing of the sensible heat flux in the 1-tile model in London results in large negative bias in the morning. The partitioning of the urban surface into canyon and roof in MORUSES improves this as the roof tile is modelled with a very low thermal inertia, but phase and amplitude of the grid box-averaged flux critically depend on accurate knowledge of the plan-area fractions of streets and buildings. Not representing non-urban land cover (e.g. vegetation, inland water) in London results in severely under-predicted latent heat fluxes. Control runs demonstrate that the skill of both models can be greatly improved by providing accurate land cover and morphology information and using representative anthropogenic heat emissions, which is essential if the model output is intended to inform integrated urban services.

The progress on the observation and modeling of surface heat fluxes and evapotranspiration over heterogeneous landscapes of the Third Pole region

2020 ◽  
Author(s):  
Yaoming Ma
Keyword(s):  
Heat Flux ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Sensible Heat Flux ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Surface Heat Fluxes ◽  
The Third ◽  
Land Surface Heat Fluxes

<p>The exchange of heat and water vapor between land surface and atmosphere over the Third Pole region (Tibetan Plateau and nearby surrounding region) plays an important role in Asian monsoon, westerlies and the northern hemisphere weather and climate systems. Supported by various agencies in the People’s Republic of China, a Third Pole Environment (TPE) observation and research Platform (TPEORP) is now implementing over the Third Pole region. The background of the establishment of the TPEORP, the establishing and monitoring plan of long-term scale (5-10 years) of it will be shown firstly. Then the preliminary observational analysis results, such as the characteristics of land surface energy fluxes partitioning and the turbulent characteristics will also been shown in this study. Then, the parameterization methodology based on satellite data and the atmospheric boundary layer (ABL) observations has been proposed and tested for deriving regional distribution of net radiation flux, soil heat flux, sensible heat flux and latent heat flux (evapotranspiration (ET)) and their variation trends over the heterogeneous landscape of the Tibetan Plateau (TP) area. To validate the proposed methodology, the ground measured net radiation flux, soil heat flux, sensible heat flux and latent heat flux of the TPEORP are compared to the derived values. The results showed that the derived land surface heat fluxes over the study areas are in good accordance with the land surface status. These parameters show a wide range due to the strong contrast of surface feature. And the estimated land surface heat fluxes are in good agreement with ground measurements, and all the absolute percent difference in less than 10% in the validation sites. The sensible heat flux has increased slightly and the latent heat flux has decreased from 2001 to 2016 over the TP. It is therefore conclude that the proposed methodology is successful for the retrieval of land surface heat fluxes and ET over heterogeneous landscape of the TP area. Further improvement of the methodology and its applying field over the whole Third Pole region and Pan-Third Pole region were also discussed.</p>

scholarly journals A New Technique to Estimate Sensible Heat Fluxes around Micrometeorological Towers Using Small Unmanned Aircraft Systems

2017 ◽  
Vol 34 (9) ◽  
pp. 2103-2112 ◽  
Author(s):  
Temple R. Lee ◽  
Michael Buban ◽  
Edward Dumas ◽  
C. Bruce Baker
Keyword(s):  
Heat Flux ◽  
Land Surface ◽  
Spatial Scales ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Unmanned Aircraft ◽  
Unmanned Aircraft Systems ◽  
Sensible Heat ◽  
Aircraft Systems ◽  
Convection Initiation

AbstractUpscaling point measurements from micrometeorological towers is a challenging task that is important for a variety of applications, for example, in process studies of convection initiation, carbon and energy budget studies, and the improvement of model parameterizations. In the present study, a technique was developed to determine the horizontal variability in sensible heat flux H surrounding micrometeorological towers. The technique was evaluated using 15-min flux observations, as well as measurements of land surface temperature and air temperature obtained from small unmanned aircraft systems (sUAS) conducted during a one-day measurement campaign. The computed H was found to be comparable to the micrometeorological measurements to within 5–10 W m−2. Furthermore, when comparing H computed using this technique with H determined using large-eddy simulations (LES), differences of <10 W m−2 were typically found. Thus, implementing this technique using observations from sUAS will help determine sensible heat flux variability at horizontal spatial scales larger than can be provided from flux tower measurements alone.

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 Improving Computation of Sensible Heat Flux over a Water Surface Using the Variational Method

2006 ◽  
Vol 7 (4) ◽  
pp. 678-686 ◽  
Author(s):  
Zuohao Cao ◽  
Jianmin Ma ◽  
Wayne R. Rouse
Keyword(s):  
Heat Flux ◽  
Variational Method ◽  
Gradient Method ◽  
Similarity Theory ◽  
Sensible Heat Flux ◽  
Open Water ◽  
Heat Fluxes ◽  
Eddy Correlation ◽  
Sensible Heat ◽  
Flux Gradient

Abstract In this study, the authors have performed the variational computations for surface sensible heat fluxes over a large northern lake using observed wind, temperature gradient, and moisture gradient. In contrast with the conventional (Monin–Obukhov similarity theory) MOST-based flux-gradient method, the variational approach sufficiently utilizes observational meteorological conditions over the lake, where the conventional flux-gradient method performs poorly. Verifications using direct eddy-correlation measurements over Great Slave Lake, the fifth largest lake in North America in terms of surface area, during the open water period of 1999 demonstrate that the variational method yields good agreements between the computed and the measured sensible heat fluxes. It is also demonstrated that the variational method is more accurate than the flux-gradient method in computations of sensible heat flux across the air–water interface.

scholarly journals Footprint issues in scintillometry over heterogeneous landscapes

2009 ◽  
Vol 6 (2) ◽  
pp. 2099-2127 ◽  
Author(s):  
W. J. Timmermans ◽  
Z. Su ◽  
A. Olioso
Keyword(s):  
Heat Flux ◽  
Time Series ◽  
Sensible Heat Flux ◽  
Simulated Data ◽  
Heat Fluxes ◽  
Two Dimensional ◽  
Sensible Heat ◽  
Heterogeneous Landscapes ◽  
Heterogeneous Landscape ◽  
Potential Tool

Abstract. Scintillometry is widely recognized as a potential tool for obtaining spatially aggregated sensible heat fluxes. Although many investigations have been made over contrasting component surfaces, few aggregation schemes consider footprint contributions. In this paper an approach is presented to infer average sensible heat flux over a very heterogeneous landscape by using a large aperture scintillometer. The methodology is demonstrated on simulated data and tested on a time series of measurements obtained during the SPARC2004 experiment in Barrax, Spain. Results show that the two-dimensional footprint approach yields more accurate results of aggregated sensible heat flux than traditional methods.

scholarly journals Energy balance in a renewal sugarcane area with fallow period and soybean cultivation

2020 ◽  
Vol 42 ◽  
pp. e39
Author(s):  
Rubmara Ketzer Oliveira ◽  
Luciano Sobral Fraga Junior ◽  
Larissa Brêtas Moura ◽  
Debora Regina Roberti ◽  
Felipe Gustavo Pilau
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Rainfall Regime ◽  
Sensible Heat ◽  
Energy Fluxes ◽  
Fallow Period

Brazil is the main sugarcane producer in the world, which is intended for various purposes, from food to power generation. Soybean cultivation in areas of sugarcane under renewal has been growing progressively in Brazil. Quantifying energy fluxes at different stages of this process is essential for better management. The work was carried out in Piracicaba city, with the objective of analyzing the behavior of energy fluxes and the closing of the energy balance in a sugarcane renewal area with a fallow period followed by soybean cultivation. The latent and sensitive heat fluxes were obtained with the “Eddy covariance” method. The closing of the energy balance in the fallow period with straw-covered uncovered and soybean-cultivated soil presented a correlation coefficient of 0.88, 0.78 and 0.71, respectively. In the period without cultivation, the sensible heat flux was predominant in relation to the latent heat flux, varying according to the rainfall regime. The presence of straw under the soil in the fallow period affected the latent heat flux. With soybean cultivation, the latent heat flux surpassed the sensible heat flux.

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