Laser pulse bidirectional reflectance from CALIPSO mission

Abstract

Abstract. This paper presents an innovative retrieval method that translates the CALIOP land surface laser pulse returns into the surface bidirectional reflectance. To better analyze the surface returns, the CALIOP receiver impulse response and the downlinked samples' distribution at 30 m resolution are discussed. The saturated laser pulse magnitudes from snow and ice 10 surfaces are recovered based on surface tail information. The retrieved snow surface bidirectional reflectance is compared with reflectance from both CALIOP cloud cover regions and MODIS BRDF/Albedo model parameters. In addition to the surface bidirectional reflectance, the column top-of-atmosphere bidirectional reflectances are calculated from the CALIOP lidar background data and compared with the bidirectional reflectances derived from WFC radiance measurements. The retrieved CALIOP surface bidirectional reflectance and column top-of-atmosphere bidirectional reflectance results provide 15 unique information to complement existing MODIS standard data products and are expected to have valuable applications for modellers.

Multi‐Year Seasonal Trends in Sea Ice, Chlorophyll Concentration, and Marine Aerosol Optical Depth in the Bellingshausen Sea

“…When the CALIPSO orbit transects surfaces covered by ice, whether land or ocean, digitizer saturation often occurs in both perpendicular and parallel 532 nm channels at the Earth's surface and altitudes immediately below (Lu et al., 2018). When the signals from these channels are ratioed, termed surface integrated depolarization ratio ( δ ), the resulting values are in the range of 0.65–1.1.…”

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

“…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).…”

New Ocean Subsurface Optical Properties From Space Lidars: CALIOP/CALIPSO and ATLAS/ICESat‐2

“…Using the CALIOP depolarization ratio measurements at 532 nm together with colocated A‐Train measurements, such as Advanced Microwave Scanning Radiometer‐Earth observing system (AMSR‐E) wind speeds and MODIS diffuse attenuation coefficients ( k d , m −1 ), innovative retrieval methods have been developed to translate the CALIOP ocean backscattered signals into ocean optical properties, such as the particulate backscatter coefficient ( b bp , m −1 ) (Behrenfeld et al., 2013; Churnside et al., 2013; Lacour et al., 2020; Lu et al., 2016), phytoplankton biomass (Behrenfeld et al., 2017), and the total depolarization ratio of ocean waters (Dionisi et al., 2020; Lu et al., 2014). However, CALIOP's coarse vertical resolution (30 m in the atmosphere, 22.5 m in the water) (Behrenfeld et al., 2013; Lu et al., 2014) and the nonideal transient response of the 532 nm detectors (Y. Hu et al., 2007; Lu et al., 2018; Lu, Hu, Vaughan, et al., 2020) present substantial challenges in retrieving ocean subsurface profiles directly from CALIOP measurements.…”