A relationship between depolarization ratio and surface concentration of particulate organic carbon (POC) is developed
from the NASA SeaWiFS Bio-optical Archive and Storage System (SeaBASS) in situ measurements and the Cloud-
Aerosol Lidar with Orthogonal Polarization (CALIOP) active lidar measurements. This relationship provides an
algorithm for estimating global POC from satellite or airborne polarization lidar measurements. Application of this
relationship to CALIOP data indicates that the estimates of POC ranges from about 3.3 mg/m<sup>3 </sup>within the South Pacific
Subtropical Gyre to 1.2×10<sup>3 </sup>mg/m<sup>3 </sup>in the area near land are in good agreement with Moderate Resolution Imaging
spectroradiometer (MODIS) POC products. Our results present depolarization ratio as a valuable tool for evaluating
global POC predictions in ocean ecosystem. The application of the algorithm to a 7-year of CALIOP depolarization ratio
mean values revealed patters of seasonal and interannual variability of POC. By comparing the results averaged over the
entire study region and entire season for each year separately, we found that the lowest POC occurred in 2013 and the
highest POC occurred in 2008.
We assess the accuracy of land surface elevation retrieved from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission through comparisons with the U.S. Geological Survey National Elevation Dataset (NED), Shuttle Radar Topography Mission (SRTM), and the altimetry product from the Geoscience Laser Altimeter System onboard the Ice, Cloud, and Land Elevation Satellite (ICESat). The vertical accuracy of the CALIPSO-derived land surface elevation was tested against these three datasets for about 16 million lidar shots over the continental United States. The results show that the CALIPSO-derived elevation was highly correlated with the elevation result from the NED, SRTM, and ICESat datasets. The overall absolute vertical accuracies of the CALIPSO-derived land surface elevation expressed as the root mean square error (RMSE) are 5.58 and 5.90 m when compared with the SRTM and NED results, respectively. Lower accuracy of the CALIPSO-derived land surface elevation was achieved by comparison with the ICESat results (8.35-m RMSE), primarily due to the several kilometers distance between the CALIPSO and ICESat ground footprints. The results show that the variability in terrain, vegetation, canopy, and footprint size can all influence comparisons between the CALIPSO-derived elevation and the results obtained from NED, SRTM, and ICESat datasets.
The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), an instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), was operated as an atmospheric lidar system to study the impact of clouds and aerosols on the Earth’s radiation budget and climate. This paper discusses the receiver transient response of the CALIOP instrument, which is useful for getting a reliable attenuated backscatter profile from CALIOP data products. The noise tail effect (slow decaying rate) of PMT and broadening effect of the
low-pass filter are both considered in modeling of the receiver transient response. An analytical expression of the CALIOP transient response function was obtained by the least square fitting of lidar measurements from land surfaces.
The primary objective of the atmospheric profiling lidar aboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite
Observations (CALIPSO) mission launched in April 2006 has been studying the climate impact of clouds and aerosols in
the atmosphere. However, CALIPSO lidar also collects information about other components of the Earth’s ecosystem,
such as polar ice sheets. The purpose of this study is to propose a new technique to provide high resolution of polar ice
sheet surface elevation from CALIPSO single shot lidar measurements (70 m spot size). The new technique relies on an
empirical relationship between the peak signal ratio and the distance between the surface and the peak signal range bin
center to achieve high altimetry resolution. The ice sheet surface elevation results in the region of Greenland and
Antarctic compare very well with the Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry measurements. The
comparisons suggest that the obtained CALIPSO ice sheet surface elevation by the new technique is accurate to within 1
m. Based on the new technique, the preliminary data product of along-track topography retrieved from the CALIPSO
lidar measurements is available to the altimetry community for evaluation.
CALIPSO satellite has been making global lidar measurements since June 2006 and its lidar, CALIOP, will likely be the
only lidar in space during the next several years. Laser altimetry data from space and aircraft-based atmospheric profiling
lidars, such as CALIOP, have not been widely used in the community due to their limited vertical sampling resolution
(30 meter) and broad laser pulse width (20 ns). This study intends to improve the CALIPSO laser altimetry data quality
and provide a highly accurate altimetry data product to the laser altimetry community.
In this study, a super-resolution laser altimetry technique has been proposed to provide improved lidar altimetry from a
profiling lidar with relatively broad pulse width and slow sampling rate. Application of the technique to CALIPSO data
leads to highly accurate CALIPSO land surface elevation measurements. The surface elevations will be derived from
near 5-year CALIPSO global observations. The CALIPSO surface elevation results in Northern America derived by the
new technique agree with the National Elevation Database (NED) high resolution elevation maps and a comparison
suggests that the accuracy of the new CALIPSO land surface elevation measurements is better than 1 meter.
Laser polarimetric imaging has great potential application to classify targets which could not be realized by intensity
imaging. A polarimetric imaging system is built to acquire two kinds of images, intensity and polarization degree coded
images, simultaneously. By fusing the intensity and polarization degree images with pseudo-color encoding technique,
we have achieved the classification of different kinds of targets with similar characteristics. Preliminary results show that
higher contrast and better resolution images classified with polarimetric technique could be obtained after speckle
reduction. Coherent speckle noise can be reduced with lowpass filter by treating it as high frequency noise. And lowpass
filter outperforms the normally used median filter in speckle reduction.
Laser polarimetric remote sensing has great potential in target detection, recognition and classification. Here, we propose
a modified laser polarimetric active imaging system. Principles and advantages of polarimetric detection are discussed.
Illuminating with a semiconductor laser, receiving by a Cassegrain telescope, splitting by a polarization beam splitter
(PBS), two images are created on two CCDs simultaneously. Two images of orthogonal polarization states can be
obtained once by using this system and then intensity and polarization degree can be calculated. Dual images coded with
intensity and polarization degree of testing target are obtained and analyzed. Preliminary experiments are conducted, and
the result shows the feasibility of the new method. Image coded with polarization degree can distinguish target, which
cannot be realized in intensity image when the targets have similar reflectivity. Intensity image and polarization degree
image can be fused together through HSI (Hue, Saturation and Intensity) pseudocolor coding. In the fusion image,
different depolarization targets display in different colors, hence the purpose of classifying targets with same material
can be achieved. Compared with traditional approaches which needing 16 images or 2 images, the new method has
extremely improved the measurement efficiency and provides a new way for real-time polarimetric imaging.