Antarctic spring ice-edge blooms observed from space by ICESat-2

Enabling Value Added Scientific Applications of ICESat‐2 Data With Effective Removal of Afterpulses

“…Compared with the land surface response in black, the signal decay after the other surfaces is much slower. This is because 532 nm laser light can penetrate into ocean, sea ice and snow surfaces and hence there are contributions from subsurface scattering, which are useful for investigating subsurface vertical structure using ICESat‐2 measurements (Lu, Hu, Yang, et al., 2020).…”

“…Therefore, the ICESat‐2 ATLAS after‐pulsing effects must first be removed in order to obtain a reliable ocean subsurface profile. A deconvolution method described in (Lu et al., 2014; Lu, Hu, Vaughan, et al., 2020; Lu, Hu, Yang, et al., 2020) can be used to remove the ICESat‐2 ATLAS afterpulses. As an illustration of the effectiveness of this deconvolution technique in removing ATLAS after‐pulsing effects, Figure 7 shows an example of the ICESat‐2 measured ocean subsurface signal (black) and its corresponding deconvolution (red).…”

“…However, under certain conditions PMT measurements can be affected by various artifacts that can confound the interpretation of the signals and potentially lead to errors in subsequent analyses. For example, the transient response of the CALIOP PMTs is nonideal (Hu et al., 2007; Lu et al., 2013, 2014; 2018; Lu, Hu, Vaughan, et al., 2020; McGill et al., 2007). That is, following a strong backscattering signal, such as from the Earth’s surface or a dense cloud, the signal initially falls off as expected but at some point begins decaying at a slower rate that is approximately exponential with respect to time (or distance).…”

“…That is, following a strong backscattering signal, such as from the Earth’s surface or a dense cloud, the signal initially falls off as expected but at some point begins decaying at a slower rate that is approximately exponential with respect to time (or distance). The CALIOP PMTs nonideal transient recovery can be seen over several hundreds of meters after a strong backscattering target (e.g., surface or water clouds), and thus make it wrongly appear as if the laser can penetrate the land surface to a depth of several hundreds of meters (Lu, Hu, Vaughan, et al., 2020; McGill et al., 2007). A second common PMT artifact is after pulsing, which is manifest as discrete, small amplitude signals that appear after onset of the main signal (Hamamatsu Photonics, 2006).…”

Geometric calibration of satellite laser altimeters based on waveform matching

“…Satellite laser altimetry technology can be used to obtain high‐precision three‐dimensional surface data. The rapid development of satellite laser altimetry has led to its application in resource surveys, environmental monitoring, polar research, disaster response and other fields (Ferreira et al, 2011; Fatoyinbo and Simard, 2013; Zhou et al, 2015; Lu et al, 2020). Full‐waveform laser altimetry systems can obtain more information about the spatial structure of the Earth’s surface features, including height, slope and aspect (Li et al, 2008; Duncanson et al, 2010; Fayad et al, 2014; Li et al, 2014; Wang et al, 2017).…”