Roy Spencer - Academia.edu (original) (raw)
Papers by Roy Spencer
Journal of Atmospheric and Oceanic Technology, 2000
STATEMENT TO THE ENVIRONMENT AND PUBLIC WORKS COMMITTEE OF THE UNITED STATES SENATE Roy W. Spence... more STATEMENT TO THE ENVIRONMENT AND PUBLIC WORKS COMMITTEE OF THE UNITED STATES SENATE Roy W. Spencer, PhD Earth System Science Center The University of Alabama in Huntsville Huntsville, Alabama 35801 18 July 2013 (Updated July 19, 2013)
In a comparison between 37 GHz brightness temperatures from the Nimbus 7 Scanning Multichannel Mi... more In a comparison between 37 GHz brightness temperatures from the Nimbus 7 Scanning Multichannel Microwave Radiometer and rain rates derived from the WSR-57 radars at Galveston, Texas and Apalachicola, Florida, it was found that the brightness temperatures explained 72% of the variance of the rain rates. The functional form relating these two types of data was significantly different from that predicted by models of radiative transfer through plane-parallel clouds. Most of the difference can be explained in terms of the partial coverage of footprints by convective showers. Because residual polarization is always present, even for large obscuring storms over land and water, it is hypothesized that emission by nonspherical hydrometeors is at least partly responsible for the observed polarization.
The sensitivity of the climate system to an imposed radiative imbalance remains the largest sourc... more The sensitivity of the climate system to an imposed radiative imbalance remains the largest source of uncertainty in projections of future anthropogenic climate change. Here we present further evidence that this uncertainty from an observational perspective is largely due to the masking of the radiative feedback signal by internal radiative forcing, probably due to natural cloud variations. That these internal radiative forcings exist and likely corrupt feedback diagnosis is demonstrated with lag regression analysis of satellite and coupled climate model data, interpreted with a simple forcing-feedback model. While the satellite-based metrics for the period 2000–2010 depart substantially in the direction of lower climate sensitivity from those similarly computed from coupled climate models, we find that, with traditional methods, it is not possible to accurately quantify this discrepancy in terms of the feedbacks which determine climate sensitivity. It is concluded that atmospheric ...
The rain and ice signatures of tropical oceanic precipitation systems obtained with the Special S... more The rain and ice signatures of tropical oceanic precipitation systems obtained with the Special Sensor Microwave Imager (SSM/I) are examined. A method for polarization correction without the F8 SSM/I V85.5 channel is presented. As an example of the methodology, SSM/I imagery is used to study the ice and liquid features of Hurricane Gilbert.
Asia-Pacific Journal of Atmospheric Sciences
Asia-Pacific Journal of Atmospheric Sciences
Journal of Atmospheric and Oceanic Technology, May 1, 2003
... J. Climate, 11, 20162041. [Abstract]. Christy, JR, RW Spencer, and WD Braswell, 2000: MSU tr... more ... J. Climate, 11, 20162041. [Abstract]. Christy, JR, RW Spencer, and WD Braswell, 2000: MSU tropospheric temperatures: Dataset construction and radiosonde comparisons. J. Atmos. ... [Abstract].Folland, CK, ,and Coauthors. 2001: Observed climate variability and change. ...
Pipeline Gas Journal, 2005
Energy Law Journal, Jul 1, 2011
The structure and energetics of an African easterly wave are examined for several days during GAT... more The structure and energetics of an African easterly wave are examined for several days during GATE (GARP Atlantic Tropical Experiment) when the wave traversed the Atlantic Ocean. Data were utilized from land and ship-based soundings, aircraft dropwindsondes, and satellite-derived cloud motion winds. Analyses include the wave's horizontal and vertical structures of wind and temperature, kinetic energy budget calculations of the mean and eddy flows, and mapping of deep convective areas. The lower tropospheric circulation was coincident with deep convection, convergence, and positive vorticities. The middle tropospheric wave was associated with a 20 ms('-1) quasi-zonal jet which was positioned above the baroclinic zone along the leading edge of a Saharan air layer. Convergence was found in the exit region of the jet and helped to maintain deep convection. The upper troposphere had anticyclonic outflow from deep convection that was superimposed upon a daily changing basic current. It was determined that the wave relied upon deep convection for a major source of its kinetic energy in the middle and upper troposphere through generation of eddy available potential energy by cumulus heating in conjunction with upward motion due to low and middle troposphere convergence. Wave kinetic energy was utilized to help maintain the kinetic energy of the middle level mean flow, and times of maximum conversion from eddy to zonal kinetic energy corresponded to times of maximum jet strength. The wave low-level circulation received energy from barotropic conversions that were strongest during wave formation and weakest during wave dissipation.
The Advanced Microwave Sounding Unit (AMSU)-A instruments on the NOAA-15 and NOAA-16 satellites p... more The Advanced Microwave Sounding Unit (AMSU)-A instruments on the NOAA-15 and NOAA-16 satellites provide information on the warm cores of tropical cyclones from oxygen channel brightness temperature (Tb) measurements near 55 GHz. With appropriate assumptions, cyclone-scale Tb gradients can be directly related to middle-to-lower tropospheric height gradients. We have developed a method for diagnosis of maximum sustained winds (Vmax) from radially averaged Tb gradients in several of the AMSU channels. Calibration of the method with recon-based (or other in situ) winds results in better agreement than with Dvorak wind estimates. Gradient wind theory shows that the warm core Tb gradient signal increases non-linearly with wind speed, making microwave temperature sounders useful for diagnosing high wind speeds, but at the expense of a minimum useful detection limit of about 40 knots. It is found that accurate wind diagnoses depend upon (1) accounting for hydrometeor effects in the AMSU channels, and (2) maximizing signal-to-noise, since the 50 km resolution data cannot fully resolve the temperature gradients in the Vmax region, typically 10-20 km in scale. AMSU imagery and max diagnoses from specific hurricanes will be shown, including independent tests from the 2000 hurricane season.
The merging procedure utilized to generate homogeneous time series of three deep-layer atmospheri... more The merging procedure utilized to generate homogeneous time series of three deep-layer atmospheric temperature products from the nine microwave sounding units (MSUs) is described. A critically important aspect in the process is determining and removing the bias each instrument possesses relative to a common base (here being NOAA-6). Special attention is given to the lower-tropospheric layer and the calculation of the bias of the NOAA-9 MSU and its rather considerable impact on the trend of the overall time series. We show that the bias is best calculated by a direct comparison between NOAA-6 and NOAA-9, though there other possible methods available, and is determined to be +0.50°C. Spurious variations of individual MSUs due to orbital drift and/or cyclic variations tied to the annual cycle are also identified and eliminated. In general, intersatellite biases for the three instruments that form the backbone of the time series (MSUs on NOAA-6, -10 and -12) are known to within 0.01°C. After slight modifications in the treatment of the bias, drift-error, and cyclic fluctuations, the authors produced a time series in which the decadal trend is +0.03°C warmer than previously reported for the lower troposphere. Because they are of much higher precision, the midtropospheric and lower-stratospheric products are only slightly affected by alterations to procedures applied in this study. Recent suggestions that spurious jumps were present in the lower-tropospheric time series of earlier versions of the MSU data based on SST comparisons are addressed. Using independent comparisons of different satellites, radiosondes, and night marine air temperatures, no indication is found of the presence of these “spurious” jumps.
Journal of Atmospheric and Oceanic Technology, 2000
STATEMENT TO THE ENVIRONMENT AND PUBLIC WORKS COMMITTEE OF THE UNITED STATES SENATE Roy W. Spence... more STATEMENT TO THE ENVIRONMENT AND PUBLIC WORKS COMMITTEE OF THE UNITED STATES SENATE Roy W. Spencer, PhD Earth System Science Center The University of Alabama in Huntsville Huntsville, Alabama 35801 18 July 2013 (Updated July 19, 2013)
In a comparison between 37 GHz brightness temperatures from the Nimbus 7 Scanning Multichannel Mi... more In a comparison between 37 GHz brightness temperatures from the Nimbus 7 Scanning Multichannel Microwave Radiometer and rain rates derived from the WSR-57 radars at Galveston, Texas and Apalachicola, Florida, it was found that the brightness temperatures explained 72% of the variance of the rain rates. The functional form relating these two types of data was significantly different from that predicted by models of radiative transfer through plane-parallel clouds. Most of the difference can be explained in terms of the partial coverage of footprints by convective showers. Because residual polarization is always present, even for large obscuring storms over land and water, it is hypothesized that emission by nonspherical hydrometeors is at least partly responsible for the observed polarization.
The sensitivity of the climate system to an imposed radiative imbalance remains the largest sourc... more The sensitivity of the climate system to an imposed radiative imbalance remains the largest source of uncertainty in projections of future anthropogenic climate change. Here we present further evidence that this uncertainty from an observational perspective is largely due to the masking of the radiative feedback signal by internal radiative forcing, probably due to natural cloud variations. That these internal radiative forcings exist and likely corrupt feedback diagnosis is demonstrated with lag regression analysis of satellite and coupled climate model data, interpreted with a simple forcing-feedback model. While the satellite-based metrics for the period 2000–2010 depart substantially in the direction of lower climate sensitivity from those similarly computed from coupled climate models, we find that, with traditional methods, it is not possible to accurately quantify this discrepancy in terms of the feedbacks which determine climate sensitivity. It is concluded that atmospheric ...
The rain and ice signatures of tropical oceanic precipitation systems obtained with the Special S... more The rain and ice signatures of tropical oceanic precipitation systems obtained with the Special Sensor Microwave Imager (SSM/I) are examined. A method for polarization correction without the F8 SSM/I V85.5 channel is presented. As an example of the methodology, SSM/I imagery is used to study the ice and liquid features of Hurricane Gilbert.
Asia-Pacific Journal of Atmospheric Sciences
Asia-Pacific Journal of Atmospheric Sciences
Journal of Atmospheric and Oceanic Technology, May 1, 2003
... J. Climate, 11, 20162041. [Abstract]. Christy, JR, RW Spencer, and WD Braswell, 2000: MSU tr... more ... J. Climate, 11, 20162041. [Abstract]. Christy, JR, RW Spencer, and WD Braswell, 2000: MSU tropospheric temperatures: Dataset construction and radiosonde comparisons. J. Atmos. ... [Abstract].Folland, CK, ,and Coauthors. 2001: Observed climate variability and change. ...
Pipeline Gas Journal, 2005
Energy Law Journal, Jul 1, 2011
The structure and energetics of an African easterly wave are examined for several days during GAT... more The structure and energetics of an African easterly wave are examined for several days during GATE (GARP Atlantic Tropical Experiment) when the wave traversed the Atlantic Ocean. Data were utilized from land and ship-based soundings, aircraft dropwindsondes, and satellite-derived cloud motion winds. Analyses include the wave's horizontal and vertical structures of wind and temperature, kinetic energy budget calculations of the mean and eddy flows, and mapping of deep convective areas. The lower tropospheric circulation was coincident with deep convection, convergence, and positive vorticities. The middle tropospheric wave was associated with a 20 ms('-1) quasi-zonal jet which was positioned above the baroclinic zone along the leading edge of a Saharan air layer. Convergence was found in the exit region of the jet and helped to maintain deep convection. The upper troposphere had anticyclonic outflow from deep convection that was superimposed upon a daily changing basic current. It was determined that the wave relied upon deep convection for a major source of its kinetic energy in the middle and upper troposphere through generation of eddy available potential energy by cumulus heating in conjunction with upward motion due to low and middle troposphere convergence. Wave kinetic energy was utilized to help maintain the kinetic energy of the middle level mean flow, and times of maximum conversion from eddy to zonal kinetic energy corresponded to times of maximum jet strength. The wave low-level circulation received energy from barotropic conversions that were strongest during wave formation and weakest during wave dissipation.
The Advanced Microwave Sounding Unit (AMSU)-A instruments on the NOAA-15 and NOAA-16 satellites p... more The Advanced Microwave Sounding Unit (AMSU)-A instruments on the NOAA-15 and NOAA-16 satellites provide information on the warm cores of tropical cyclones from oxygen channel brightness temperature (Tb) measurements near 55 GHz. With appropriate assumptions, cyclone-scale Tb gradients can be directly related to middle-to-lower tropospheric height gradients. We have developed a method for diagnosis of maximum sustained winds (Vmax) from radially averaged Tb gradients in several of the AMSU channels. Calibration of the method with recon-based (or other in situ) winds results in better agreement than with Dvorak wind estimates. Gradient wind theory shows that the warm core Tb gradient signal increases non-linearly with wind speed, making microwave temperature sounders useful for diagnosing high wind speeds, but at the expense of a minimum useful detection limit of about 40 knots. It is found that accurate wind diagnoses depend upon (1) accounting for hydrometeor effects in the AMSU channels, and (2) maximizing signal-to-noise, since the 50 km resolution data cannot fully resolve the temperature gradients in the Vmax region, typically 10-20 km in scale. AMSU imagery and max diagnoses from specific hurricanes will be shown, including independent tests from the 2000 hurricane season.
The merging procedure utilized to generate homogeneous time series of three deep-layer atmospheri... more The merging procedure utilized to generate homogeneous time series of three deep-layer atmospheric temperature products from the nine microwave sounding units (MSUs) is described. A critically important aspect in the process is determining and removing the bias each instrument possesses relative to a common base (here being NOAA-6). Special attention is given to the lower-tropospheric layer and the calculation of the bias of the NOAA-9 MSU and its rather considerable impact on the trend of the overall time series. We show that the bias is best calculated by a direct comparison between NOAA-6 and NOAA-9, though there other possible methods available, and is determined to be +0.50°C. Spurious variations of individual MSUs due to orbital drift and/or cyclic variations tied to the annual cycle are also identified and eliminated. In general, intersatellite biases for the three instruments that form the backbone of the time series (MSUs on NOAA-6, -10 and -12) are known to within 0.01°C. After slight modifications in the treatment of the bias, drift-error, and cyclic fluctuations, the authors produced a time series in which the decadal trend is +0.03°C warmer than previously reported for the lower troposphere. Because they are of much higher precision, the midtropospheric and lower-stratospheric products are only slightly affected by alterations to procedures applied in this study. Recent suggestions that spurious jumps were present in the lower-tropospheric time series of earlier versions of the MSU data based on SST comparisons are addressed. Using independent comparisons of different satellites, radiosondes, and night marine air temperatures, no indication is found of the presence of these “spurious” jumps.