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

The Advanced Topographic Laser Altimeter System (ATLAS) aboard the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) has been making very high resolution measurements of the Earth's surface elevation since October 2018. ATLAS uses photomultiplier tubes (PMTs) as detectors in photon counting mode, so that a single photon reflected back to the receiver triggers a detection within the ICESat-2 data acquisition system. However, one characteristic of ICESat-2 detected photons is the possible presence of afterpulses, defined as small amplitude pulses occurring after the primary signal pulse due to photon arrival. The disadvantage of these afterpulses is that they often confound the accurate measurements of low level signals following a large amplitude of signal and can degrade energy resolution and cause errors in pulse counting applications. This paper discusses and summarizes the after-pulsing effects exhibited by the ATLAS PMTs based on on-orbit measurements over different seasons and geographic regions. The potential impacts of these after-pulsing effects on altimetry and ocean subsurface retrievals are discussed.

Swelling of Transported Smoke from Savanna fires over the Southeast Atlantic Ocean

We use the recently released Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Version 4.1 (V4) lidar data to study the smoke plumes transported from Southern African biomass burning areas. Significant improvements in the CALIPSO V4 Level 1 calibration and V4 Level 2 algorithms lead to a better representation of their optical properties, with the aerosol subtype improvements being particularly relevant to smoke over this area. For the first time, we show evidence of smoke particles increasing in size, evidenced in their particulate color ratios, as they are transported over the South Atlantic Ocean from the source regions over Southern Africa. We hypothesize that this is due to hygroscopic swelling of the smoke particles and is reflected in the higher relative humidity in the middle troposphere for profiles with smoke. This finding may have implications for radiative forcing estimates over this area and is also relevant to the ORACLES field mission.

Laser pulse bidirectional reflectance from CALIPSO mission

This paper presents an innovative retrieval method that translate 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 returns from snow and ice 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. Besides the surface bidirectional reflectance, the column top-of-atmosphere bidirectional reflectance is calculated from the CALIOP lidar background data. It is compared with bidirectional reflectance from WFC radiance measurements. The retrieved CALIOP surface bidirectional reflectance and column top-of-atmosphere bidirectional reflectance results provide unique information to complement existing MODIS standard data products and would have valuable applications for modellers.

Retrieval of ocean subsurface particulate backscattering coefficient from space-borne CALIOP lidar measurements

A new approach has been proposed to determine ocean subsurface particulate backscattering coefficient b_bp from CALIOP 30° off-nadir lidar measurements. The new method also provides estimates of the particle volume scattering function at the 180° scattering angle. The CALIOP based layer-integrated lidar backscatter and particulate backscattering coefficients are compared with the results obtained from MODIS ocean color measurements. The comparison analysis shows that ocean subsurface lidar backscatter and particulate backscattering coefficient b_bp can be accurately obtained from CALIOP lidar measurements, thereby supporting the use of space-borne lidar measurements for ocean subsurface studies.

Tolerability, central effects and pharmacokinetics of intravenous ketorolac tromethamine in volunteers

The central effects, tolerability and pharmacokinetics of multiple intravenous doses of the analgesic ketorolac tromethamine (30 mg 4 times daily for 5 days) were studied in male volunteers. In this double-blind, randomized, parallel group study, 13 subjects received ketorolac tromethamine and 7 subjects received placebo (vehicle). To determine the effects of withdrawal all subjects were then given further dosing with placebo (4 times daily) for 2 days while maintaining the double-blind nature of the previous drug assignment. Physical examinations and laboratory tests were obtained prior to the drug administration and after completion of the study. Scales for assessment of anxiety, depression, sleep and opiate withdrawal were presented to the subjects on day 2, 5, 6, 7 and 8 of the study. After 5 days of multiple intravenous doses ketorolac showed overall good systemic tolerance and safety in comparison with placebo. Myalgia and taste perversion were more frequently reported in the ketorolac group. The frequency of injection site complaints, mostly transient pain, was about 80% for both ketorolac and placebo, indicating these were likely caused by the vehicle. There were no significant changes in the scales assessing anxiety, depression, sleep and opiate withdrawal during treatment with ketorolac and after its withdrawal, suggesting that the drug has neither any major central effects nor any clear addiction potential in this dose schedule. Pharmacokinetic parameters were derived from plasma samples collected after the first and last active doses.(ABSTRACT TRUNCATED AT 250 WORDS)