scholarly journals Impact of Aerosol Property on the Accuracy of a CO2 Retrieval Algorithm from Satellite Remote Sensing

2016 ◽  
Vol 8 (4) ◽  
pp. 322 ◽  
Author(s):  
Yeonjin Jung ◽  
Jhoon Kim ◽  
Woogyung Kim ◽  
Hartmut Boesch ◽  
Hanlim Lee ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Satellite Remote Sensing ◽  
Retrieval Algorithm ◽  
Aerosol Property

scholarly journals Big grains go far: reconciling tephrochronology with atmospheric measurements of volcanic ash

2015 ◽  
Vol 8 (1) ◽  
pp. 65-120 ◽  
Author(s):  
J. A. Stevenson ◽  
S. C. Millington ◽  
F. M. Beckett ◽  
G. T. Swindles ◽  
T. Thordarson
Keyword(s):  
Remote Sensing ◽  
Satellite Remote Sensing ◽  
Volcanic Ash ◽  
Dispersion Model ◽  
Geometric Standard Deviation ◽  
Retrieval Algorithm ◽  
Systematic Bias ◽  
Atmospheric Measurements ◽  
Release Height ◽  
Nw Europe

Abstract. There is a large discrepancy between the size of volcanic ash particles measured from deposits on the ground (known as cryptotephra; 20–125 μm in length) and those reported by satellite remote sensing (effective radii of 0.5–9 μm; 95% of particles < 17 μm diameter). We use results from the fields of tephrochronology (a dating technique based on volcanic ash layers), dispersion modelling and satellite remote sensing in an attempt to understand from where it arises. We show that Icelandic cryptotephras deposited in NW Europe have lognormal particle size distributions (PSDs) with median lengths of 20–70 μm (geometric standard deviation: 1.40–1.66; 95th percentile length: 42–126 microns). This is consistent with semi-quantitative grainsize range estimates from the literature. Using measured fall velocities of ash particles, a release height typical of moderate Icelandic eruptions (10 km) and a wind speed typical for NW Europe (10 m s−1), we find that an ash cloud can transport particles < 80 μm diameter up to 850 km in 24 h, so that even moderately sized Icelandic eruptions can deposit cryptotephra on mainland Europe. The proportion of cryptotephra in airborne clouds is unknown. We used simulated satellite data of dispersion-model-derived ash clouds to investigate the effect of PSD on satellite retrievals and show that as the median radius of the input PSD increases, fewer ash-containing pixels are correctly identified. Where retrievals are made of simulated clouds with mass median radii larger than ~ 10 μm, the mean retrieved reff plateaus at around 9 μm. This is a systematic bias in the retrieval algorithm that would cause the grainsize of distal clouds containing significant cryptotephra to be underestimated. This cannot explain discrepancies in coarser proximal clouds, however, which may be because the complex physics of scattering by highly irregularly-shaped grains is inadequately represented by assuming that particles are dense spheres.

Monitoring land use change in the Lake Taupo catchment between 1975, 1990 and 2002 using satellite remote sensing data

2007 ◽  
pp. 17-22
Author(s):  
H. Lilienthal ◽  
A. Brauer ◽  
K. Betteridge ◽  
E. Schnug
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Land Use ◽  
Land Use Change ◽  
Satellite Remote Sensing ◽  
Remote Sensing Data ◽  
Native Vegetation ◽  
Lake Water Quality ◽  
Livestock Farming ◽  
Slow Decline

Conversion of native vegetation into farmed grassland in the Lake Taupo catchment commenced in the late 1950s. The lake's iconic value is being threatened by the slow decline in lake water quality that has become apparent since the 1970s. Keywords: satellite remote sensing, nitrate leaching, land use change, livestock farming, land management

Small-scale vegetation mapping of large territories: perspectives of using modern remote sensing and GIS technologies, the Indian experiences

1996 ◽  
pp. 51-54 ◽  
Author(s):  
N. V. M. Unni
Keyword(s):  
Remote Sensing ◽  
Satellite Remote Sensing ◽  
Forest Cover ◽  
Human Life ◽  
Remote Sensing Data ◽  
Modern World ◽  
Small Scale ◽  
Vegetation Map ◽  
Gis Technologies ◽  
Forest Cover Mapping

The recognition of versatile importance of vegetation for the human life resulted in the emergence of vegetation science and many its applications in the modern world. Hence a vegetation map should be versatile enough to provide the basis for these applications. Thus, a vegetation map should contain not only information on vegetation types and their derivatives but also the geospheric and climatic background. While the geospheric information could be obtained, mapped and generalized directly using satellite remote sensing, a computerized Geographic Information System can integrate it with meaningful vegetation information classes for large areas. Such aft approach was developed with respect to mapping forest vegetation in India at. 1 : 100 000 (1983) and is in progress now (forest cover mapping at 1 : 250 000). Several review works reporting the experimental and operational use of satellite remote sensing data in India were published in the last years (Unni, 1991, 1992, 1994).

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