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Title: Reducing uncertainty in climate prediction : enhancing the science case for TRUTHS
Author: Seales, Amy
ISNI:       0000 0004 7427 7432
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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The research in this thesis focuses on the ability of a proposed satellite mission, Traceable Radiometry Underpinning Terrestrial and Helio- Studies (TRUTHS), to detect signals of climate change as manifested in the Earth’s reflected shortwave spectrum. TRUTHS aims to measure the total incoming solar irradiance, spectral solar irradiance and Earth’s reflected shortwave radiation with sufficient radiometric accuracy to enable rapid detection of signals of climate change above natural variability. Early detection of such signals will potentially enable mitigation strategies to be employed faster. Initially, sensitivity studies were conducted to investigate the atmospheric and surface variables that affect reflected shortwave spectra. TOA shortwave reflectances calculated from Climate Observation System Simulation Experiment (COSSE) data were then used to investigate how quickly changes could be detected above natural variability, as manifested in the simulations, using a linear regression model. The shortest detection times ranged from 7-15 years and 10-25 years under clear and all sky conditions respectively. The impact of spatial resolution was investigated by comparing 10 degree and 1.41 degree zonal average data. The 10 degree data provided 9.2% more detections at <20 years for all sky conditions than the high resolution data. The data were also separated into land and ocean to investigate the effect of surface type, however this in general yielded no clear improvement in detection times. Finally, gaps were added to the data record to simulate realistic climate observation scenarios. These gaps varied from 10 to 25 years, with records lengths of 3 or 5 years based on the estimated lifetime of a TRUTHS mission. Detection times indicate that, of the scenarios investigated, a repeating 5 year mission followed by a 10 year gap is optimal, providing detection times of predominantly < 20 years globally at 1600nm, 1680nm and 2190nm, and in the tropics at visible wavelengths.
Supervisor: Brindley, Helen ; Green, Paul Sponsor: Engineering and Physical Sciences Research Council ; National Physical Laboratory
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral