17 research outputs found
ESTIMATING INDUSTRIAL STRUCTURE CHANGES IN CHINA USING DMSP – OLS NIGHT-TIME LIGHT DATA DURING 1999–2012
The Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) night-time light imagery has been proved to be a powerful tool to monitor economic development with its relatively high spatial resolution at large scales. Night-time lights caused by human activities derived from DMSP-OLS satellite imagery are widely used in socioeconomic parameter estimations and urbanization monitoring. In this paper, DMSP-OLS night-time stable light data from 1999 to 2012 are utilized to analyze inter-annual variation in GDP of per unit light intensity (RGDP) in China. Furthermore, RGDP was compared with statistical data of the tertiary industry structure for 28 provincial regions. The results show that the provincial RGDP decreased abruptly in 2001–2002, 2008–2009 and 2011–2012, which is consistent with the proportional growth of the tertiary industry in GDP. These results indicate that the changes in RGDP can reflect tertiary industry structural changes in China's province-level regions
Investigation of ice particle habits to be used for ice cloud remote sensing for the GCOM-C satellite mission
In this study, various ice particle habits are investigated in conjunction
with inferring the optical properties of ice clouds for use in the Global
Change Observation Mission-Climate (GCOM-C) satellite programme. We develop a database of the single-scattering properties of five ice habit models:
plates, columns, droxtals, bullet rosettes, and Voronoi. The database is
based on the specification of the Second Generation Global Imager (SGLI)
sensor on board the GCOM-C satellite, which is scheduled to be launched in
2017 by the Japan Aerospace Exploration Agency. A combination of the
finite-difference time-domain method, the geometric optics integral equation
technique, and the geometric optics method is applied to compute the
single-scattering properties of the selected ice particle habits at 36
wavelengths, from the visible to the infrared spectral regions. This covers
the SGLI channels for the size parameter, which is defined as a single-particle radius of an equivalent volume sphere, ranging between 6 and
9000 µm. The database includes the extinction efficiency,
absorption efficiency, average geometrical cross section, single-scattering
albedo, asymmetry factor, size parameter of a volume-equivalent sphere,
maximum distance from the centre of mass, particle volume, and six nonzero
elements of the scattering phase matrix. The characteristics of calculated
extinction efficiency, single-scattering albedo, and asymmetry factor of the
five ice particle habits are compared. Furthermore, size-integrated bulk
scattering properties for the five ice particle habit models are calculated
from the single-scattering database and microphysical data. Using the five
ice particle habit models, the optical thickness and spherical albedo of ice
clouds are retrieved from the Polarization and Directionality of the Earth's
Reflectances-3 (POLDER-3) measurements, recorded on board the Polarization
and Anisotropy of Reflectances for Atmospheric Sciences coupled with
Observations from a Lidar (PARASOL) satellite. The optimal ice particle habit
for retrieving the SGLI ice cloud properties is investigated by adopting the
spherical albedo difference (SAD) method. It is found that the SAD is
distributed stably due to the scattering angle increases for bullet rosettes
with an effective diameter (<i>D</i><sub>eff</sub>) of 10 µm and Voronoi
particles with <i>D</i><sub>eff</sub> values of 10, 60, and 100 µm. It is
confirmed that the SAD of small bullet-rosette particles and all sizes of
Voronoi particles has a low angular dependence, indicating that a combination
of the bullet-rosette and Voronoi models is sufficient for retrieval of the
ice cloud's spherical albedo and optical thickness as effective habit models
for the SGLI sensor. Finally, SAD analysis based on the Voronoi habit model
with moderate particle size (<i>D</i><sub>eff</sub> = 60 µm) is compared
with the conventional general habit mixture model, inhomogeneous hexagonal
monocrystal model, five-plate aggregate model, and ensemble ice particle model.
The Voronoi habit model is found to have an effect similar to that found in
some conventional models for the retrieval of ice cloud properties from
space-borne radiometric observations
Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument
The principles of cloud droplet size retrieval via Polarization and
Directionality of the Earth's Reflectance (POLDER) requires that clouds be
horizontally homogeneous. The retrieval is performed by combining all
measurements from an area of 150 km × 150 km to compensate for
POLDER's insufficient directional sampling. Using POLDER-like data simulated
with the RT3 model, we investigate the impact of cloud horizontal
inhomogeneity and directional sampling on the retrieval and analyze which
spatial resolution is potentially accessible from the measurements. Case
studies show that the sub-grid-scale variability in droplet effective radius
(CDR) can significantly reduce valid retrievals and introduce small biases
to the CDR (~ 1.5 μm) and effective variance (EV)
estimates. Nevertheless, the sub-grid-scale variations in EV and cloud
optical thickness (COT) only influence the EV retrievals and not the CDR
estimate. In the directional sampling cases studied, the retrieval using
limited observations is accurate and is largely free of random noise.
Several improvements have been made to the original POLDER droplet size
retrieval. For example, measurements in the primary rainbow region
(137–145°) are used to ensure retrievals of large droplet
(> 15 μm) and to reduce the uncertainties caused by cloud
heterogeneity. We apply the improved method using the POLDER global L1B data
from June 2008, and the new CDR results are compared with the operational
CDRs. The comparison shows that the operational CDRs tend to be
underestimated for large droplets because the cloudbow oscillations in the
scattering angle region of 145–165° are weak for cloud fields with
CDR > 15 μm. Finally, a sub-grid-scale retrieval case
demonstrates that a higher resolution, e.g., 42 km × 42 km, can be
used when inverting cloud droplet size distribution parameters from POLDER
measurements
Trans-boundary aerosol transport during a winter haze episode in China revealed by ground-based Lidar and CALIPSO satellite
2016-2017 > Academic research: refereed > Publication in refereed journal201812_a bcmaVersion of RecordPublishe