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Electromagnetic Radiation and Remote Sensing
Published in Ni-Bin Chang, Kaixu Bai, Multisensor Data Fusion and Machine Learning for Environmental Remote Sensing, 2018
Earth's net radiation is the balance between outgoing and incoming energy at the TOA level. The solar energy arriving at the surface can vary from 550 W/m2 with cirrus clouds to 1025 W/m2 with a clear sky (Krivova et al., 2011). Earth and the atmosphere absorb 341 W/m2 of solar radiation on average annually (Johnson, 1954). In view of the energy budget delineation in Figure 2.4, outgoing longwave radiation is EMR emitted from Earth and its atmosphere out to space in the form of thermal radiation through both soil layers and atmospheric layers. Most of the outgoing longwave radiation has wavelengths (from 4 to 100 μm) in the thermal infrared part of the electromagnetic spectrum. In fact, our planet's climate is driven by absorption, reflection, shortwave or longwave emission, and scattering of radiation within the atmosphere due to the presence of thin clouds, aerosol, and some gases. Cases can be seen in some extreme weather events such as tropical storms and hurricane assessment.
Generation of global 1-km daily top-of-atmosphere outgoing longwave radiation product from 2000 to 2021 using machine learning
Published in International Journal of Digital Earth, 2023
The top-of-atmosphere (TOA) outgoing longwave radiation (OLR), defined as the outgoing radiation flux emitted from the Earth’s surface and atmosphere in the infrared wavelength regime, is an essential component of the Earth’s energy budget (Liang et al. 2019). TOA OLR is widely used in weather and climate research as it is strongly related to atmospheric conditions (e.g. water vapor, cloud cover) (Schmetz and Liu 1988). For instance, OLR has been used as an index of tropical convective activity to investigate decadal variations of atmospheric circulation in the global tropical belt (Nitta and Yamada 1989). Climate changes in the tropical western Pacific and Indian Ocean regions can also be detected by OLR records (Chu and Wang 1997). Therefore, accurate estimation of the global OLR is necessary.
Understanding climate change through Earth’s energy flows
Published in Journal of the Royal Society of New Zealand, 2020
All GHGs trap outgoing longwave radiation (OLR) which is mainly in the infrared part of the electromagnetic spectrum. The shorter wavelength incoming radiation from the sun, and hence the absorbed solar radiation (ASR), are initially largely unaffected. Infrared radiation from thermal emissions at Earth temperatures increases when the temperature of the emitting body increases. Hence with increasing GHGs, the planet warms until the OLR increases to match the ASR. This simple picture is complicated by many feedbacks and complexities, but the case can be made that the most fundamental measure that the climate is changing is the Earth's Energy Imbalance (EEI) (von Schuckmann et al. 2016). A major advantage of EEI is that it is the net result of all the complicated processes and feedbacks. This article focusses on these aspects, and details the difficulties of the traditional approach to dealing with climate change via models, and an alternative although complementary approach focused on EEI.
Remote sensing of earth’s energy budget: synthesis and review
Published in International Journal of Digital Earth, 2019
Shunlin Liang, Dongdong Wang, Tao He, Yunyue Yu
OLR (Fl) is not only an important component of EEB, but is also widely used as a tool in numerous applications, such as climate sensitivity and diagnosis, weather and climate predictions, studies on monsoon variability and equatorial waves. OLR is considered as a proxy for the deep convection and used as a heuristic indicator of cloudiness or for precipitation estimation. OLR anomalies may also be explored to link with earthquakes because these events can generate thermal anomalies in the atmosphere at low latitudes due to the overabundance of ions from the seismogenic zone (Chakraborty et al. 2018; Shah et al. 2018).