scholarly journals Parameterization of Urban Sensible Heat Flux from Remotely Sensed Surface Temperature: Effects of Surface Structure

2019 ◽  
Vol 11 (11) ◽  
pp. 1347 ◽  
Author(s):  
Jinxin Yang ◽  
Massimo Menenti ◽  
E. Scott Krayenhoff ◽  
Zhifeng Wu ◽  
Qian Shi ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Sensible Heat Flux ◽  
Effective Resistance ◽  
Three Dimensions ◽  
Sensible Heat ◽  
Wall Surface ◽  
Surface Temperatures ◽  
Flux Parameterization ◽  
The Impact

Sensible heat exchange has important consequences for urban meteorology and related applications. Directional radiometric surface temperatures of urban canopies observed by remote sensing platforms have the potential to inform estimations of urban sensible heat flux. An imaging radiometer viewing the surface from nadir cannot capture the complete urban surface temperature, which is defined as the mean surface temperature over all urban facets in three dimensions, which includes building wall surface temperatures and requires an estimation of urban sensible heat flux. In this study, a numerical microclimate model, Temperatures of Urban Facets in 3-D (TUF-3D), was used to model sensible heat flux as well as radiometric and complete surface temperatures. Model data were applied to parameterize an effective resistance for the calculation of urban sensible heat flux from the radiometric (nadir view) surface temperature. The results showed that sensible heat flux was overestimated during daytime when the radiometric surface temperature was used without the effective resistance that accounts for the impact of wall surface temperature on heat flux. Parameterization of this additional resistance enabled reasonably accurate estimates of urban sensible heat flux from the radiometric surface temperature.

scholarly journals The impact of broadleaved woodland on water resources in lowland UK: II. Evaporation estimates from sensible heat flux measurements over beech woodland and grass on chalk sites in Hampshire

2005 ◽  
Vol 9 (6) ◽  
pp. 607-613 ◽  
Author(s):  
J. Roberts ◽  
P. Rosier ◽  
D. M. Smith
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Excellent Agreement ◽  
Sensible Heat Flux ◽  
Late Summer ◽  
Eddy Correlation ◽  
Sensible Heat ◽  
Flux Measurements ◽  
Shallow Soils ◽  
The Impact

Abstract. The impact on recharge to the Chalk aquifer of substitution of broadleaved woodland for pasture is a matter of concern in the UK. Hence, measurements of energy balance components were made above beech woodland and above pasture, both growing on shallow soils over chalk in Hampshire. Latent heat flux (evaporation) was calculated as the residual from these measurements of energy balances in which sensible heat flux was measured with an eddy correlation instrument that determined fast response vertical wind speeds and associated temperature changes. Assessment of wind turbulence statistics confirmed that the eddy correlation device performed satisfactorily in both wet and dry conditions. There was excellent agreement between forest transpiration measurements made by eddy correlation and stand level tree transpiration measured with sap flow devices. Over the period of the measurements, from March 1999 to late summer 2000, changes in soil water content were small and grassland evaporation and transpiration estimated from energy balance-eddy flux measurements were in excellent agreement with Penman estimates of potential evaporation. Over the 18-month measurement period, the cumulative difference between broadleaved woodland and grassland was small but evaporation from the grassland was 3% higher than that from the woodland. In the springs of 1999 and 2000, evaporation from the grassland was greater than that from the woodland. However, following leaf emergence in the woodland, the difference in cumulative evaporation diminished until the following spring.

scholarly journals Evaluation of functional properties of various types of vegetation cover using remotely sensed data analysis

2010 ◽  
Vol 4 (Special Issue 2) ◽  
pp. S49-S58 ◽  
Author(s):  
J. Brom ◽  
J. Procházka ◽  
A. Rejšková
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Hydrological Cycle ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Remotely Sensed Data ◽  
Mean Values

The dissipation of solar energy and consequently the formation of the hydrological cycle are largely dependent on the structural and optical characteristics of the land surface. In our study, we selected seven units with different types of vegetation in the Mlýnský and Horský catchments (South-Eastern part of the Šumava Mountains, Czech Republic) for the assessment of the differences in their functioning expressed through the surface temperature, humidity, and energy dissipation. For our analyses, we used Landsat 5 TM satellite data from June 25<SUP>th</SUP>, 2008. The results showed that the microclimatic characteristics and energy fluxes varied in different units according to their vegetation characteristics. A cluster analysis of the mean values was used to divide the vegetation units into groups according to their functional characteristics. The mown meadows were characterised by the highest surface temperature and sensible heat flux and the lowest humidity and latent heat flux. On the contrary, the lowest surface temperature and sensible heat flux and the highest humidity and latent heat flux were found in the forest. Our results showed that the climatic and energetic features of the land surface are related to the type of vegetation. We state that the spatial distribution of different vegetation units and the amount of biomass are crucial variables influencing the functioning of the landscape.

Sensible Heat Flux-Radiometric Surface Temperature Relationship for Eight Semiarid Areas

1994 ◽  
Vol 33 (9) ◽  
pp. 1110-1117 ◽  
Author(s):  
J. B. Stewart ◽  
W. P. Kustas ◽  
K. S. Humes ◽  
W. D. Nichols ◽  
M. S. Moran ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Sensible Heat Flux ◽  
Temperature Relationship ◽  
Sensible Heat ◽  
Semiarid Areas

scholarly journals Analyse De L’impact Du Changement De La Couverture Végétale Sur La Pluie Et La Température De Surface Au Sénégal

2017 ◽  
Vol 13 (29) ◽  
pp. 270
Author(s):  
Ibrahima Diba ◽  
Moctar Camara
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Vegetation Change ◽  
Heat Waves ◽  
Sensible Heat Flux ◽  
Strong Increase ◽  
The North ◽  
Model Control ◽  
Low Levels ◽  
The Impact

This work aims at examining the potential impacts of vegetation change (reforestation) of the Sahel-Sahara interface on the intra-seasonal and interannual variability of the rainfall and surface temperature over Senegal using the RegCM4 model. Two runs were performed from 1990 to 2009 with a spatial resolution of 50 km (0.44 °): the standard version of the RegCM4 model (control version) and the reforested one (named RegCM4_REFORESTATION). The impact of the reforestation is to decrease the surface temperature over Senegal in summer (JJAS). This decrease could be partly due to a decrease of the sensible heat flux over the southern and central Senegal and a strong increase of the latent heat flux. The reforestation also tends to increase the rainfall over the whole country and particularly in the Southwest. This rainfall increase which can also create an evaporative cooling, is consistent with the decrease of the surface temperature. The analysis of the annual cycle over three domains of Senegal shows that the reforestation tends to strengthen the low-levels humidity of the atmosphere from January to December especially during the summer period in the North and in the center of the country. The surface temperature presents two maxima in April-May and October-November and a minimum during the summer. The reforestation has a cooling impact during the whole year (particularly in the summer) and over the center and the northern part of Senegal. At the interannual timescale, the reforestation modifies significantly the rainfall by generally increasing it. However, there are years in which this trend is not respected and this translates into a weak correlation coefficient in the South of the country. This rainfall increase may translates into extreme hydroclimatic events such as floods. This work can be considered as a support for the Senegalese policymakers for the better planning of the management of adverse potential effects (such as floods, drought, heat waves, etc) of the Sahel-Sahara greening effort.

scholarly journals Uncertainty analysis of computational methods for deriving sensible heat flux values from scintillometer measurements

2009 ◽  
Vol 2 (3) ◽  
pp. 1383-1417 ◽  
Author(s):  
P. A. Solignac ◽  
A. Brut ◽  
J.-L. Selves ◽  
J.-P. Béteille ◽  
J.-P. Gastellu-Etchegorry ◽  
...  
Keyword(s):  
Heat Flux ◽  
Classical Method ◽  
Sensible Heat Flux ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Eddy Correlation ◽  
Time Averaging ◽  
Sensible Heat ◽  
Ratio Measurement ◽  
The Impact

Abstract. The use of scintillometers to determine sensible heat fluxes is now common in studies of land-atmosphere interactions. The main interest in these instruments is due to their ability to quantify energy distributions at the landscape scale, as they can calculate sensible heat flux values over long distances, in contrast to Eddy Correlation systems. However, scintillometer data do not provide a direct measure of sensible heat flux, but require additional data, such as the Bowen ratio (β), to provide flux values. The Bowen ratio can either be measured using Eddy Correlation systems or derived from the energy balance closure. In this work, specific requirements for estimating energy fluxes using a scintillometer were analyzed, as well as the accuracy of two flux calculation methods. We first focused on the classical method (used in standard software). We analysed the impact of the Bowen ratio according to both time averaging and ratio values; for instance, an averaged Bowen ratio (β) of less than 1 proved to be a significant source of measurement uncertainty. An alternative method, called the "β-closure method", for which the Bowen ratio measurement is not necessary, was also tested. In this case, it was observed that even for low β values, flux uncertainties were reduced and scintillometer data were well correlated with the Eddy Correlation results.

Sign in / Sign up

Export Citation Format

Share Document