B.S., Engineering Physics, University of Colorado (1960), M.S., Physics and Astrophysics, University of Colorado (1963), Ph.D. Atmospheric Physics, University of California at Los Angeles (1975) Developed state of the art Active Cavity Radiometer Irradiance Monitor (ACRIM) sensors for measurement of the total solar irradiance (TSI) of the earth. Designed and carried out a series of 3 NASA ACRIM satellite experiments that monitored TSI from 1980 to 2013. Studied the composite TSI record in the context of correlating TSI and climate change.
A continuous record of direct total solar irradiance (TSI) observations began with a series of sa... more A continuous record of direct total solar irradiance (TSI) observations began with a series of satellite experiments in 1978. This record requires comparisons of overlapping satellite observations with adequate relative precisions to provide useful long term TSI trend information. Herein we briefly review the active cavity radiometer irradiance monitor physikalisch-meteorologisches observatorium davos (ACRIM-PMOD) TSI composite controversy regarding how the total solar irradiance (TSI) has evolved since 1978 and about whether TSI significantly increased or slightly decreased from 1980 to 2000. The main question is whether TSI increased or decreased during the so-called ACRIM-gap period from 1989 to 1992. There is significant discrepancy between TSI proxy models and observations before and after the gap, which requires a careful revisit of the data analysis and modeling performed during the ACRIM-gap period. In this study, we use three recently proposed TSI proxy models that do not p...
We present a new analysis of the two-decade-old controversy over interpretation of satellite obse... more We present a new analysis of the two-decade-old controversy over interpretation of satellite observations of total solar irradiance (TSI) since 1978 and the implications of our findings for TSI as a driver of climate change. Our approach compares the methods of constructing the two most commonly referenced TSI composites (ACRIM and PMOD) that relate successive observational databases and two others recently constructed using a novel statistical approach. Our primary focus is on the disparate decadal trending results of the ACRIM and PMOD TSI composite time series, namely, whether they indicate an increasing trend from 1980 to 2000 and a decreasing trend thereafter (ACRIM) or a continuously decreasing trend since 1980 (PMOD). Construction of the four-decade observational TSI composites from 1978 to the present requires the use of results from two less precise Earth Radiation Budget experiments (Nimbus7/ERB and ERBS/ERBE) during the so-called ACRIM-Gap (1989.5–1991.8), between the end...
The technical challenge for TSI monitoring is to provide highly precise relative observations (tr... more The technical challenge for TSI monitoring is to provide highly precise relative observations (traceability) over climate timescales (decades to centuries) since sustained variations as small as 1000 ppm (0.1%) may cause significant climate change over these periods. The precision of satellite instrumentation using ambient temperature sensors can be smaller than their accuracy (~ 1000 ppm SI) by two orders of
A mean value for the 1 AU total solar irradiance of 1368.2 W/m² and a downward trend of 0.05% pe... more A mean value for the 1 AU total solar irradiance of 1368.2 W/m² and a downward trend of 0.05% per year were derived from measurements by the Active Cavity Radiometer Irradiance Monitor (ACRIM) experiment on the Solar Maximum Mission during 1980. Distinct temporary solar irradiance decreases associated with solar activity maxima were observed with a series of nine dips from April to October recurring at fairly regular intervals averaging 24 days. The decreases correlate inversely with sunspot area, 2800-MHz flux, and Zurich sunspot number. Dominant periods common to the irradiance and sunspot area power spectra link the irradiance decreases to sunspot flux deficit in solar active regions. Evidence of significant total irradiance modulation by facular flux excess is cited. A persistent radiative cycle of active regions consistent with the ACRIM irradiance results and the morphology of solar active regions was found. The pattern of regularly recurrent active region maxima between April and October suggests an asymmetry in solar activity generation during this period.
Composite TSI time series have been constructed from the set of contiguous, redundant, overlappin... more Composite TSI time series have been constructed from the set of contiguous, redundant, overlapping total solar irradiance (TSI) observations made by satellite experiments since late 1978. A precise knowledge of the relationship between ACRIM1 and ACRIM2 across the two year gap separating their results is required and can be derived using one of two overlapping data sets: the Nimbus7/ERB or
A continuous record of direct total solar irradiance (TSI) observations began with a series of sa... more A continuous record of direct total solar irradiance (TSI) observations began with a series of satellite experiments in 1978. This record requires comparisons of overlapping satellite observations with adequate relative precisions to provide useful long term TSI trend information. Herein we briefly review the active cavity radiometer irradiance monitor physikalisch-meteorologisches observatorium davos (ACRIM-PMOD) TSI composite controversy regarding how the total solar irradiance (TSI) has evolved since 1978 and about whether TSI significantly increased or slightly decreased from 1980 to 2000. The main question is whether TSI increased or decreased during the so-called ACRIM-gap period from 1989 to 1992. There is significant discrepancy between TSI proxy models and observations before and after the gap, which requires a careful revisit of the data analysis and modeling performed during the ACRIM-gap period. In this study, we use three recently proposed TSI proxy models that do not p...
We present a new analysis of the two-decade-old controversy over interpretation of satellite obse... more We present a new analysis of the two-decade-old controversy over interpretation of satellite observations of total solar irradiance (TSI) since 1978 and the implications of our findings for TSI as a driver of climate change. Our approach compares the methods of constructing the two most commonly referenced TSI composites (ACRIM and PMOD) that relate successive observational databases and two others recently constructed using a novel statistical approach. Our primary focus is on the disparate decadal trending results of the ACRIM and PMOD TSI composite time series, namely, whether they indicate an increasing trend from 1980 to 2000 and a decreasing trend thereafter (ACRIM) or a continuously decreasing trend since 1980 (PMOD). Construction of the four-decade observational TSI composites from 1978 to the present requires the use of results from two less precise Earth Radiation Budget experiments (Nimbus7/ERB and ERBS/ERBE) during the so-called ACRIM-Gap (1989.5–1991.8), between the end...
The technical challenge for TSI monitoring is to provide highly precise relative observations (tr... more The technical challenge for TSI monitoring is to provide highly precise relative observations (traceability) over climate timescales (decades to centuries) since sustained variations as small as 1000 ppm (0.1%) may cause significant climate change over these periods. The precision of satellite instrumentation using ambient temperature sensors can be smaller than their accuracy (~ 1000 ppm SI) by two orders of
A mean value for the 1 AU total solar irradiance of 1368.2 W/m² and a downward trend of 0.05% pe... more A mean value for the 1 AU total solar irradiance of 1368.2 W/m² and a downward trend of 0.05% per year were derived from measurements by the Active Cavity Radiometer Irradiance Monitor (ACRIM) experiment on the Solar Maximum Mission during 1980. Distinct temporary solar irradiance decreases associated with solar activity maxima were observed with a series of nine dips from April to October recurring at fairly regular intervals averaging 24 days. The decreases correlate inversely with sunspot area, 2800-MHz flux, and Zurich sunspot number. Dominant periods common to the irradiance and sunspot area power spectra link the irradiance decreases to sunspot flux deficit in solar active regions. Evidence of significant total irradiance modulation by facular flux excess is cited. A persistent radiative cycle of active regions consistent with the ACRIM irradiance results and the morphology of solar active regions was found. The pattern of regularly recurrent active region maxima between April and October suggests an asymmetry in solar activity generation during this period.
Composite TSI time series have been constructed from the set of contiguous, redundant, overlappin... more Composite TSI time series have been constructed from the set of contiguous, redundant, overlapping total solar irradiance (TSI) observations made by satellite experiments since late 1978. A precise knowledge of the relationship between ACRIM1 and ACRIM2 across the two year gap separating their results is required and can be derived using one of two overlapping data sets: the Nimbus7/ERB or
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