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Title: Ascension Island: The Layered Atlantic Smoke Interactions with Clouds (LASIC) Campaign

Abstract

The ARM Climate Research Facility, a DOE scientific user facility, provides the climate research community with strategically located in situ and remote sensing observatories designed to improve the understanding and representation, in climate and earth system models, of clouds and aerosols as well as their interactions and coupling with the Earth’s surface.

Authors:
 [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC). Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1351251
Report Number(s):
LA-UR-17-22580
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Earth Sciences

Citation Formats

Nitschke, Kim. Ascension Island: The Layered Atlantic Smoke Interactions with Clouds (LASIC) Campaign. United States: N. p., 2017. Web. doi:10.2172/1351251.
Nitschke, Kim. Ascension Island: The Layered Atlantic Smoke Interactions with Clouds (LASIC) Campaign. United States. doi:10.2172/1351251.
Nitschke, Kim. Thu . "Ascension Island: The Layered Atlantic Smoke Interactions with Clouds (LASIC) Campaign". United States. doi:10.2172/1351251. https://www.osti.gov/servlets/purl/1351251.
@article{osti_1351251,
title = {Ascension Island: The Layered Atlantic Smoke Interactions with Clouds (LASIC) Campaign},
author = {Nitschke, Kim},
abstractNote = {The ARM Climate Research Facility, a DOE scientific user facility, provides the climate research community with strategically located in situ and remote sensing observatories designed to improve the understanding and representation, in climate and earth system models, of clouds and aerosols as well as their interactions and coupling with the Earth’s surface.},
doi = {10.2172/1351251},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Mar 30 00:00:00 EDT 2017},
month = {Thu Mar 30 00:00:00 EDT 2017}
}

Technical Report:

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  • Ascension Island is a geologic anomaly. It was formed by volcanism along the Mid-Atlantic Ridge about 7 million years ago, and that volcanism has continued as the oceanic plate moved westward away from the media valley of the ridge. Geologic mapping during this study has documented the distribution and age relationships of lithologies and structures. Chemical analysis of rocks samples and have allowed a quantitative classification of rock types. Potential for a geothermal discovery on Ascension Island is very high.
  • A preliminary evaluation of the potential for an economic geothermal resource at Ascension Island was completed. It is concluded that there is a high potential for the presence of a geothermal resource under the Island. A conceptual plant has been designed assuming the resource potential located near Gannet Hill is developed. A 7% discounted payback of 5.9 years was calculated for the baseline geothermal plant. Geothermal development can be easily integrated into the Ascension Island power system in that a selection of small, portable, skid mounted, turn key power geothermal generating systems are commercially available. Geologic findings and plant analysismore » are summarized.« less
  • The Phase I study of the geothermal potential of Ascension Island concluded that the possibility of a geothermal resource existing under the island was excellent. This conclusion was based on the presence of young volcanic rocks (a heat source close to the surface), an ample supply of water from the sea, and high permeability of many of the rocks which make up the island. The assumption was made that the resource would be similar to geothermal systems in the Azores or Japan, and a conceptual design of a power plant to utilize the resource was prepared upon which cost estimatesmore » and an economic analysis were subsequently performed. The results of the economic analysis were very favorable, and the Air Force decided to proceed into Phase II of the project. Under Phase II, an exploration program was designed and carried out. The purpose of the program was to ascertain whether or not a geothermal resource existed beneath Ascension island and, to the extent possible, to evaluate the quality of that resource. The exploration involved a detailed aeromagnetic survey of the island, reconnaissance and detailed electrical resistivity surveys, and drilling of holes for the measurement of temperatures. These methods have confirmed the existence of geothermal activity beneath Ascension. Measured temperature gradients and bottom hole temperatures as well as chemical geothermometers indicate temperatures sufficient for the generation of electricity within reasonable drilling depths. This report documents those conclusions and the supporting data. This report also documents the results of the power plant update with new data supplied from the Phase II exploration activities on the island. The power plant scenario has been changed to reflect the fact that the resource temperature may not be as high as that originally assumed in the Phase I study, the location of the production wells will in all likelihood be farther from the existing Air Force facilities--either north of Grazing Valley or south of Traveller's Hill--and the demand for power has increased which results in a more efficient utilization of the geothermal resource. The power plant concept chosen is similar to that used for Phase I in that small, modular, skid-mounted, factory assembled and tested, units are used to supply the power and potable water.« less
  • This technical report on the Phase II geothermal exploration of Ascension Island documents the data collected during thermal gradient drilling and the subsequent thermal and fluid chemical investigations. It also documents the completion of the Phase II exploration strategy which was proposed at the end of the Phase I--Preliminary Examination of Ascension Island. The thermal gradient drilling resulted in seven holes which range from 206 to 1750 ft (53-533 m) deep, with a cumulative footage of 6563 ft (2000 m). The drilling procedure and the problems encountered during the drilling have been explained in detail to provide information valuable formore » any subsequent drilling program on the island. In addition, the subsurface geology encountered in the holes has been documented and, where possible, correlated with other holes or the geology mapped on the surface of the island. Temperatures measured in the holes reach a maximum of 130 F (54.4 C) at 1285 ft (391.7 m) in hole GH-6. When the temperatures of all holes are plotted against elevation, the holes can be classed into three distinct groups, those which have no thermal manifestations, those with definite geothermal affinities, and one hole which is intermediate between the other two. From consideration of this information, it is clear that the highest geothermal potential on the island is in the Donkey Flat area extending beneath Middleton Ridge, and in the Cricket Valley area. Because of the greater drilling depths and the remote nature of the Cricket Valley area, it is recommended that future exploration concentrate in the area around Middleton Ridge.« less
  • Southern Africa is the world’s largest emitter of biomass-burning (BB) aerosols. Their westward transport over the remote southeast Atlantic Ocean colocates some of the largest atmospheric loadings of absorbing aerosol with the least examined of the Earth’s major subtropical stratocumulus decks. Global aerosol model results highlight that the largest positive top-of-atmosphere forcing in the world occurs in the southeast Atlantic, but this region exhibits large differences in magnitude and sign between reputable models, in part because of high variability in the underlying model cloud distributions. Many uncertainties contribute to the highly variable model radiation fields: the aging of shortwave-absorbing aerosolmore » during transport, how much of the aerosol mixes into the cloudy boundary layer, and how the low clouds adjust to smoke-radiation and smoke-cloud interactions. In addition, the ability of the BB aerosol to absorb shortwave radiation is known to vary seasonally as the fuel type on land changes.« less