Emissivity is a crucial parameter for calculating Land Surface Temperature (LST). One of the algorithms to calculate LST using single thermal band of Landsat 8 (Band 10) or Landsat 7 (Band 6) or Landsat 5 (Band 6) is based on the simplified Radiative Transfer Model (RTM) equation as documented in Barsi et al.(2003). The RTM equation in question is the following :
Ltoa = τεLt + Lu + (1-ε) Ld
where, τ is the atmospheric transmission, ε is the emissivity of the surface, Lt is the radiance of a blackbody target of kinetic temperature t, Lu is the upwelling or atmospheric path radiance, Ld is the downwelling or sky radiance, Ltoa is the Top Of Atmosphere (TOA) radiance measured by the sensor.
For this question, I'm only interested in estimating ε. Generally, I've been using the NDVI Threshold Method as described in Sobrino et al. (2001), which probably is the most commonly used method for estimating emissivity. This works more or less okay for Landsat scenes that have been acquired during the day. However, for night-time Landsat acquisitions, estimating emissivity using the NDVI method is illogical because the NIR and Red bands of Landsat mostly register only noise. This could be due to the absence of reflected energy from the sun at night and radiometric sensitivity of the sensor. With that said, I'm aware of alternate ways to estimate emissivity, e.g., (1) by Image Classification method which assumes emissivity for each class, or (2) by using emissivity values from spectral libraries such as the ASTER spectral library (http://asterweb.jpl.nasa.gov), or (3) by taking into account the seasonal ASTER Global Emissivity Database (GED) provided by JPL or (4) In-situ emissivity measurements. Except the last method, that is rarely available, the other methods may not be close enough in regard to the temporal resolution of the night-time Landsat image acquired for which the Land Surface Temperature is to be determined. In such a case, what would be the best way to accurately obtain a Land Surface Emissivity image for the corresponding night time Landsat thermal image?
Does anybody have any other ideas? You're encouraged to add relevant references in addition to your answers/comments.
PS: USGS is developing a Landsat Surface Temperature product that would be made available in the future, but I'm not sure whether it includes night time surface temperature.
References:
https://atmcorr.gsfc.nasa.gov/
https://remotesensing.usgs.gov/ecv/CDR_lst.php
https://landsat.usgs.gov/march-14-2018-upcoming-temporary-hold-us-landsat-ard-production
This might help:
Land Surface Temperature Mapping using Geoinformation Techniques
DOI: https://doi.org/10.14311/gi.17.1.2
Thanks Dr. Makinde for sharing your open access research article.
However, this paper uses the same NDVI based emissivity method (Sobrino et al., 2001) for estimation of day-time Land Surface Temperature from Landsat. My question is specifically about calculation of night-time Land Surface Temperature for Landsat. I don't think the NDVI based emissivity method will help for calculating night-time land surface temperature. Correct me if I'm wrong? Have you worked with night-time Landsat images for obtaining LST?
good greeting
I know Landsat does not take photos at night because it is synchronous with the orbit of the sun
Modher, thanks for your comments.
Allow me to clarify. Landsat 8 does acquire night-time images occasionally during its ascending (nighttime) node. In fact there is also a possibility for making special requests for acquiring night-time scenes. Look at the NASA Goddard video that I've attached here. You will be able to see the narrator says at 0:22-0:30 that, "The satellite travels from north to south over the sunlit portion of the Earth, and travels south to north over the dark side (night-time) of the Earth." Therefore when the satellite travels from south to north (ascending), it potentially has the ability to image the night side of the Earth.
If you are interested, you can browse through the archive of 18,839 Landsat 8 night-time images that have been acquired at the time of this writing.
https://earthexplorer.usgs.gov/
https://landsat.usgs.gov/acquisition
https://www.youtube.com/watch?v=P-lbujsVa2M
https://landsat.usgs.gov/how-do-i-search-and-download-ascending-nighttime-scenes
Hi James,
If I understand your question, USGS through earth explorer provides radiometrically corrected surface reflectance imagery for data with quality terrain level L1T and/or L1gT. it might be necessary to check your metadata file to confirm the data type...I suppose the method by Sobrino et al. should be applicable to any of these data type which has been corrected from atmospheric distortions. Otherwise, i will suggest you correct your reflectance image using techniques such as dark object subtraction before NDVI computations and then emissivity calculation using the procedure in the above literature. The following articles might be helpful.
https://earth.esa.int/web/guest/data-access/browse-data-products/-/article/landsat-oli-tirs-european-coverage
Article Investigating Surface Urban Heat Island Characteristics over...
Regards
Hello Kazeem, thanks for your comments and for sharing your research article on UHI.
Let me clarify. USGS already provides atmospherically corrected (Surface Reflectance - SR) Level 2 Landsat data. In fact, it also directly provides spectral indices such as NDVI, which is based on Level 2 SR Landsat data. However, in the question I'm talking about 'Night-Time' Landsat data. There is a clear difference between night-time and day-time Landsat data. As you are aware, 'Passive sensors such as Landsat are mostly used to detect energy when the naturally occurring energy source (Sun) is available. For all reflected energy, this can only take place during the time when the sun is illuminating the Earth. There is no reflected energy available from the sun at night. Energy that is naturally emitted (such as thermal infrared) can be detected day or night, as long as the amount of energy is large enough to be recorded.' That is why if you look at the VIS-NIR-SWIR bands of night time Landsat data, you would hardly be able to identify anything (except active fires, lava or other large and hot objects, if present during the time of image acquisition). However, with the thermal infrared (TIR) band, you can identify the naturally emitted energy from the Earth's surface. Therefore, I concluded that Sobrino et al. (2001) NDVI based emissivity method cannot be used for night-time land surface temperature estimation! I've added the Landsat 8 image details that I'm studying. Along with that I've added three night-time Landsat 8 Band 10, Band 5 and Band 4 images for your reference. Have a look and let me know if you agree or disagree.
Location: Reykjavík, Iceland
Landsat 8 Scene ID: LC80672292015017LGN01
Data Type: L1GT
Acquisition Date: 2015/01/17
Acquisition Time: 22:26
Hi all Please I need multispectral images in food , fruits , skin diseases (more than 25 images) thank you?
Dear in my opinion I think you can use the thermal bands in Landsat OLI 8 band 10 and band 10 to get what you want
regards
Hi all I think you can use thermal bands in LANDSAT-8 to
to obtain emissivity image
regards
Hi James this has been an old topic, have you solved it? I have the same issue. I have a diurnal and a nocturnal image from the same day, and I was considering using the diurnal ndvi to compute the emissivity. Did you solve it differently?
Ana Oliveira, as I understand, it seems, it would be fine to use the closest day-time emissivity image derived from NDVI in order to estimate land surface temperature of a night-time Landsat scene, provided, there are no changes related to soil moisture or land cover/use changes in between the day and night (e.g. Landsat) image acquisitions. In other situations a correction is required. For example, an emissivity correction would be required if a night-time Landsat image was acquired immediately after a rain event leading to significant soil moisture changes which in turn increases/decreases the emissivity of the land surface in the thermal infrared wavelength range.
You may want to look at the following paper. They have used a spectrally adjusted ASTER Global Emissivity Data Set version 3. Also have a look at the Joint Emissivity Database Initiative (JEDI).
- An Operational Land Surface Temperature Product for Landsat Thermal Data: Methodology and Validation by Malakar et al. (2018)
- https://emissivity.jpl.nasa.gov/aster-ged
Yes my understanding agrees with your input. My days are clear sky heatwave summer days, without rain. Great, many thanks! I will look into it.
It is not to late to know there are many websites provide what you asking for
wishes
I think there is no Landsat night time product available to download yet.
Abd El Raouf Elhmdi & Aysar Jameel Abdalkadhum
Landsat 8 does acquire night-time images occasionally during its ascending (nighttime) mode. For more info. read the 4th comment from the top that I posted on March 26, 2018 on this discussion page. Landsat 8 has acquired 27088 night-time images till date. You can select the 'Night' option in the 'Additional Criteria' on USGS EarthExplorer to download the night-time images.
Please see the third section of the paper below.
Sobrino, José A., Juan C. Jiménez-Muñoz, and Leonardo Paolini. 2004. “Land Surface Temperature Retrieval from LANDSAT TM 5.” Remote Sensing of Environment 90 (4): 434–40. https://doi.org/10.1016/j.rse.2004.02.003.
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