PASTRI - Pilot for Aerial Surface Temperature Retrieval

2021 ◽  
Author(s):  
Daniel Spengler ◽  
Max Gulde ◽  
Bierdel Marius ◽  
Welling Cassi ◽  
Stottmeister Alex ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Land Surface ◽  
Sensor Performance ◽  
The Status ◽  
Reference Measurements ◽  
Temperature Retrieval ◽  
Farming Industry ◽  
Monitoring Service ◽  
Monitoring Area

<p>PASTRI will be a joint pilot study of ConstellR, GFZ Potsdam and FU Berlin for airborne based aerial surface temperature retrieval. The mission is planned as a preparation and demonstrator mission for the upcoming spaceborne thermal satellite microsatellites of ConstellR. ConstellR will provide a land surface temperature (LST) monitoring service with an initial focus on companies in the precision farming industry. The initial minimal viable constellation (MVC) of four microsatellites will offer global, daily LST monitoring at 50 m spatial resolution with 1.5 K radiometric accuracy for a monitoring area capacity comparable to the size of Germany’s agricultural area.</p><p>The authors intend to use a six-week airborne campaign in May/June 2021 as a data delivery pilot to develop and validate the provision of an LST product. In total 18 flights are planned (3 flights/week every second week, 2 flights/day) with the FU Berlin Cessna T207A. On the technical side, the project includes the payload development and adaptation to the mechanical interface of the airplane, the actual (airborne) recording or imagery, as well as setting up the data processing pipeline. The aircraft will be instrumented with an adapted ConstellR Sensor and a thermal hyperspectral Telops HyperCam. This enables a performance evaluation of the microsatellite sensor performance against a hyperspectral reference instrument. Based on that results, final adaptions could be made for the spaceborne sensors. The flights will be performed in Central Germany at agricultural sites and will be supplemented by in-situ reference measurements.</p><p>The concept and the status of preparation of the campaign will be presented.</p>

Plot-scale retrieval of land surface temperature and emissivity estimation

2021 ◽  
Author(s):  
Gitanjali Thakur ◽  
Stan Schymanski ◽  
Kaniska Mallick ◽  
Ivonne Trebs
Keyword(s):  
Land Cover ◽  
Surface Temperature ◽  
Land Surface Temperature ◽  
Satellite Data ◽  
Land Surface ◽  
Longwave Radiation ◽  
Landscape Scale ◽  
The Earth ◽  
Downwelling Longwave Radiation

<p>The surface energy balance (SEB) is defined as the balance between incoming energy from the sun and outgoing energy from the Earth’s surface. All components of the SEB depend on land surface temperature (LST). Therefore, LST is an important state variable that controls the energy and water exchange between the Earth’s surface and the atmosphere. LST can be estimated radiometrically, based on the infrared radiance emanating from the surface. At the landscape scale, LST is derived from thermal radiation measured using  satellites.  At the plot scale, eddy covariance flux towers commonly record downwelling and upwelling longwave radiation, which can be inverted to retrieve LST  using the grey body equation :<br>             R<sub>lup</sub> = εσ T<sub>s</sub><sup>4</sup> + (1 − ε) R<sub> ldw         </sub>(1)<br>where R<sub>lup</sub> is the upwelling longwave radiation, R<sub>ldw</sub> is the downwelling longwave radiation, ε is the surface emissivity, <em>T<sub>s</sub>  </em>is the surface temperature and σ  is the Stefan-Boltzmann constant. The first term is the temperature-dependent part, while the second represents reflected longwave radiation. Since in the past downwelling longwave radiation was not measured routinely using flux towers, it is an established practice to only use upwelling longwave radiation for the retrieval of plot-scale LST, essentially neglecting the reflected part and shortening Eq. 1 to:<br>               R<sub>lup</sub> = εσ T<sub>s</sub><sup>4 </sup>                       (2)<br>Despite  widespread availability of downwelling longwave radiation measurements, it is still common to use the short equation (Eq. 2) for in-situ LST retrieval. This prompts the question if ignoring the downwelling longwave radiation introduces a bias in LST estimations from tower measurements. Another associated question is how to obtain the correct ε needed for in-situ LST retrievals using tower-based measurements.<br>The current work addresses these two important science questions using observed fluxes at eddy covariance towers for different land cover types. Additionally, uncertainty in retrieved LST and emissivity due to uncertainty in input fluxes was quantified using SOBOL-based uncertainty analysis (SALib). Using landscape-scale emissivity obtained from satellite data (MODIS), we found that the LST  obtained using the complete equation (Eq. 1) is 0.5 to 1.5 K lower than the short equation (Eq. 2). Also, plot-scale emissivity was estimated using observed sensible heat flux and surface-air temperature differences. Plot-scale emissivity obtained using the complete equation was generally between 0.8 to 0.98 while the short equation gave values between 0.9 to 0.98, for all land cover types. Despite additional input data for the complete equation, the uncertainty in plot-scale LST was not greater than if the short equation was used. Landscape-scale daytime LST obtained from satellite data (MODIS TERRA) were strongly correlated with our plot-scale estimates, but on average higher by 0.5 to 9 K, regardless of the equation used. However, for most sites, the correspondence between MODIS TERRA LST and retrieved plot-scale LST estimates increased significantly if plot-scale emissivity was used instead of the landscape-scale emissivity obtained from satellite data.</p>

Evaluation of Land Surface Temperature Retrieved from MODIS Data

2013 ◽  
Vol 785-786 ◽  
pp. 1333-1336
Author(s):  
Xiao Feng Yang ◽  
Xing Ping Wen
Keyword(s):  
Surface Temperature ◽  
Brightness Temperature ◽  
Land Surface Temperature ◽  
Global Climate Change ◽  
Land Surface ◽  
Global Climate ◽  
Average Temperature ◽  
Profile Line ◽  
Weather Stations ◽  
Temperature Retrieval

Land surface temperature (LST) is important factor in global climate change studies, radiation budgets estimating, city heat and others. In this paper, land surface temperature of Guangzhou metropolis was retrieved from two MODIS imageries obtained at night and during the day respectively. Firstly, pixel values were calibrated to spectral radiances according to parameters from header files. Then, the brightness temperature was calculated using Planck function. Finally, The brightness temperature retrieval maps were projected and output. Comparing two brightness temperature retrieval maps, it is concluded that the brightness temperature retrieval are more accurate at night than during the day. Comparing the profile line of brightness temperature from north to south, the brightness temperature increases from north to south. Temperature different from north to south is larger at night than during the day. The average temperature nears 18°C at night and the average temperature nears 26°C during the day, which is consistent with the surface temperature observed by automatic weather stations.

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