In the context of global warming and climate change, it has become essential to conduct thorough global and regional studies on temperature fluctuations.
Traditionally, in a typical ground-based weather station, the atmospheric temperature, also known as the air temperature, is recorded. With a global network of thousands of weather stations around the world, researchers can calculate the global mean temperature, analyze temperature anomalies, find causes of warming, and predict future climate scenarios.
However, conducting global or regional-level research can be challenging when attempting to consolidate data frequently from a dense network of ground-based sensors.
Temperature measurement using satellites
Satellite-based land surface temperature (LST) measurement is complementary to the air temperature because LST comes with a wide spatial coverage, which is expensive to achieve with ground stations. LST is widely accessible, can be integrated easily, and offers scalability. The use of LST can be advantageous in situations where there is limited ground data available. However, in the case of LST, there is a decrease in accuracy because of the presence of intricate land cover categories and the obstruction caused by cloud cover.
Is it possible for LST to serve as a substitute for air temperature measurements? Are they identical measurements?
No, they are not identical. There is a conceptual distinction. Land surface temperature refers to the overall temperature of the Earth’s surface, which includes the temperature of various components like soil, vegetation, and structures. In essence, LST is a combined measurement of the radiometric surface temperature. The sensor can detect the aggregate radiation that the components emit. The factors that influence LST include the level of moisture present, the nature of the surface, and the amount of solar energy received. While meteorological factors like wind and humidity also have an impact on air temperature measurement, land surface temperature is the primary factor.
Statistical approaches can be used to establish a relationship between air temperature and land surface temperature at certain locations and periods. The correlation demonstrates a stronger association during daylight hours compared to nighttime. This can be attributed to the prevalence of solar energy as the primary determinant during daylight hours. However, in certain studies, air temperature can serve as a more meaningful parameter.
When discussing differences between day and night, does land surface temperature vary in a similar manner to air temperature?
The land surface temperature exhibits greater fluctuations compared to the air temperature. The rate of change of LST is much higher than that of air temperature, which changes more gradually. The impact of solar radiation is more noticeably evident in LST compared to air temperature. The thermal inertia of the materials plays a major role in determining LST. During the night, the decline in LST over a water body is not as rapid as in other surrounding areas due to the high thermal inertia of the water; although the air temperature may not exhibit a significant effect.
When discussing seasonal variations, which option is superior?
Land surface temperature is advantageous for research on land-atmosphere interactions as it accounts for variations in vegetation cover and soil moisture. However, while assessing the influence on humans or the environment, it is necessary to take into account the air temperature. Also, in order to achieve a high level of precision, it is essential to incorporate the air temperature. In certain instances, both datasets can serve to enhance one another.
References:
Land Product Validation Subgroup (Working Group On Calibration And Validation Committee On Earth Observation Satellites). (2017). Land Surface Temperature Product Validation Best Practice Protocol. https://doi.org/10.5067/DOC/CEOSWGCV/LPV/LST.001
Li, Z.-L., Wu, H., Duan, S.-B., Zhao, W., Ren, H., Liu, X., Leng, P., Tang, R., Ye, X., Zhu, J., Sun, Y., Si, M., Liu, M., Li, J., Zhang, X., Shang, G., Tang, B.-H., Yan, G., & Zhou, C. (2023). Satellite Remote Sensing of Global Land Surface Temperature: Definition, Methods, Products, and Applications. Reviews of Geophysics, 61(1), e2022RG000777. https://doi.org/10.1029/2022RG000777
