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Geosciences, Volume 5, Issue 4 (December 2015) – 3 articles , Pages 286-360

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3237 KiB  
Article
Evaluation of VIIRS Land Surface Temperature Using CREST-SAFE Air, Snow Surface, and Soil Temperature Data
by Carlos L. Pérez Díaz, Tarendra Lakhankar, Peter Romanov, Reza Khanbilvardi and Yunyue Yu
Geosciences 2015, 5(4), 334-360; https://doi.org/10.3390/geosciences5040334 - 15 Dec 2015
Cited by 3 | Viewed by 5285
Abstract
In this study, the Visible Infrared Imager Radiometer Suite (VIIRS) Land Surface Temperature (LST) Environmental Data Record (EDR) was evaluated against snow surface (T-skin) and near-surface air temperature (T-air) ground observations recorded at the Cooperative Remote Sensing Science and Technology Center—Snow Analysis and [...] Read more.
In this study, the Visible Infrared Imager Radiometer Suite (VIIRS) Land Surface Temperature (LST) Environmental Data Record (EDR) was evaluated against snow surface (T-skin) and near-surface air temperature (T-air) ground observations recorded at the Cooperative Remote Sensing Science and Technology Center—Snow Analysis and Field Experiment (CREST-SAFE), located in Caribou, ME, USA during the winters of 2013 and 2014. The satellite LST corroboration of snow-covered areas is imperative because high-latitude regions are often physically inaccessible and there is a need to complement the data from the existing meteorological station networks. T-skin is not a standard meteorological parameter commonly observed at synoptic stations. Common practice is to measure surface infrared emission from the land surface at research stations across the world that allow for estimating ground-observed LST. Accurate T-skin observations are critical for estimating latent and sensible heat fluxes over snow-covered areas because the incoming and outgoing radiation fluxes from the snow mass and T-air make the snow surface temperature different from the average snowpack temperature. Precise characterization of the LST using satellite observations is an important issue because several climate and hydrological models use T-skin as input. Results indicate that T-air correlates better than T-skin with VIIRS LST data and that the accuracy of nighttime LST retrievals is considerably better than that of daytime. Based on these results, empirical relationships to estimate T-air and T-skin for clear-sky conditions from remotely-sensed (RS) LST were derived. Additionally, an empirical formula to correct cloud-contaminated RS LST was developed. Full article
(This article belongs to the Special Issue Advances in Remote Sensing and GIS for Geomorphological Mapping)
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3497 KiB  
Article
Evaluation of the Snow Thermal Model (SNTHERM) through Continuous in situ Observations of Snow’s Physical Properties at the CREST-SAFE Field Experiment
by Jose A. Infante Corona, Jonathan Muñoz, Tarendra Lakhankar, Peter Romanov and Reza Khanbilvardi
Geosciences 2015, 5(4), 310-333; https://doi.org/10.3390/geosciences5040310 - 02 Nov 2015
Cited by 3 | Viewed by 5615
Abstract
Snowpack properties like temperature or density are the result of a complex energy and mass balance process in the snowpack that varies temporally and spatially. The Snow Thermal Model (SNTHERM) is a 1-dimensional model, energy and mass balance-driven, that simulates these properties. This [...] Read more.
Snowpack properties like temperature or density are the result of a complex energy and mass balance process in the snowpack that varies temporally and spatially. The Snow Thermal Model (SNTHERM) is a 1-dimensional model, energy and mass balance-driven, that simulates these properties. This article analyzes the simulated snowpack properties using SNTHERM forced with two datasets, namely measured meteorological data at the Cooperative Remote Sensing Science and Technology-Snow Analysis and Field Experiment (CREST-SAFE) site and the National Land Data Assimilation System (NLDAS). The study area is located on the premises of Caribou Municipal Airport at Caribou (ME, USA). The model evaluation is based on properties such as snow depth, snow water equivalent, and snow density, in addition to a layer-by-layer comparison of snowpack properties. The simulations were assessed with precise in situ observations collected at the CREST-SAFE site. The outputs of the SNTHERM model showed very good agreement with observed data in properties like snow depth, snow water equivalent, and average temperature. Conversely, the model was not very efficient when simulating properties like temperature and grain size in different layers of the snowpack. Full article
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Article
Late Tertiary Petrified Wood from Nevada, USA: Evidence of Multiple Silicification Pathways
by George E. Mustoe
Geosciences 2015, 5(4), 286-309; https://doi.org/10.3390/geosciences5040286 - 14 Oct 2015
Cited by 31 | Viewed by 10426
Abstract
Late Tertiary fossil woods from the state of Nevada provide an opportunity for observing the mineralization sequences that cause buried wood to become permineralized. Oligocene and Miocene caldera basins contain abundant petrified wood that ranges in composition from incipient silicification to complete permineralization. [...] Read more.
Late Tertiary fossil woods from the state of Nevada provide an opportunity for observing the mineralization sequences that cause buried wood to become permineralized. Oligocene and Miocene caldera basins contain abundant petrified wood that ranges in composition from incipient silicification to complete permineralization. Examination of specimens from 21 localities reveals that the petrifaction sequence can follow multiple pathways. Fossil wood specimens from a single stratum may have different mineralization; silicification may vary even within a single specimen. Despite these variations, several trends are evident. Features in Nevada specimens suggest that two fundamental processes are involved: early mineralization of cell walls, and later silica deposition in lumina, vessels, and rot pockets from groundwater that permeated these open spaces. The process of open-space filling may be analogous to the genesis of geodes and veins, where multiple episodes of hydrothermal precipitation may produce opal, chalcedony, and quartz as deposits within a single cavity. Silica polymorphs may coexist as primary precipitates, or they may originate from solid-state transformation of a single parent material. Relic lepisphere textures observed in some chalcedony wood specimens are evidence of opal→chalcedony transition. In Nevada, specimens that contain crystalline quartz, this mineral appears to have been formed by direct precipitation in open spaces, not from recrystallization of chalcedony. Opal-A has seldom been reported in fossil wood, but this amorphous material is fairly common in Nevada specimens. Full article
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