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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)
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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... 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.
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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... 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 ...
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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... 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.
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... 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:... 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. ...
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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,... 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.
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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... 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 atmospheric temperature products from the nine microwave sounding units (MSUs) is described. A critically important aspect in the process is... 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.
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The potential of microwave sounding units (MSU) for augmenting the surface-based thermometer record by providing a measurement representing a significant depth of the troposphere is considered. These radiometers measure the thermal... more
The potential of microwave sounding units (MSU) for augmenting the surface-based thermometer record by providing a measurement representing a significant depth of the troposphere is considered. These radiometers measure the thermal emission by molecular oxygen in the atmosphere at different spectral intervals in the oxygen absorption complex near 60 GHz. Brightness temperature variations measured by NOAA-6 and NOAA-7 MSUs during a near-two year period are analyzed and compared with monthly averaged surface air temperature data. It is demonstrated that MSUs, while of limited use for vertical profiling of the atmosphere, provide stable measurements of vertically average atmospheric temperatures, centered at a constant pressure level.
The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) was provided by the National Space Development Agency of Japan (NASDA) to fly on NASA's Aqua satellite. AMSR-E has a wide variety of hydrologic science applications.... more
The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) was provided by the National Space Development Agency of Japan (NASDA) to fly on NASA's Aqua satellite. AMSR-E has a wide variety of hydrologic science applications. Retrievals currently being made from the data include: all-weather sea surface temperatures; precipitation; oceanic surface wind speed, integrated cloud water, and water vapor; soil moisture; sea ice parameters; and, snow cover parameters. The AMSR-E performance has been, on the whole, excellent. AMSR-E carries 20 channels, with the highest spatial resolution yet achieved from space, at dual polarized frequencies ranging from 6.9 GHz to 89 GHz. A variety of field experiments supporting validation of most of the geophysical retrieval algorithms have now been completed.
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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... 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.
Results are presented of an intercomparison between MSU channel 2 Tb and radiosonde data taking both oxygen and water vapor absorption into account. A total of 45 stations covering most of the central and eastern U.S. were included.... more
Results are presented of an intercomparison between MSU channel 2 Tb and radiosonde data taking both oxygen and water vapor absorption into account. A total of 45 stations covering most of the central and eastern U.S. were included. Precise comparisons (to 0.1 C or better) between MSU Tb and radiosonde-calculated Tb were found to be possible with large numbers of stations and long averaging periods (many months), although they are not sufficient in number to address the previously documented monthly precision of 0.01 C from satellite-satellite intercomparisons. The MSU channel 2 does not have a 1:1 response to atmospheric temperature variations; the response averages about 92 percent. No evidence was found to suggest that procedural or hardware changes in the U.S. radiosonde system have caused any widespread biases between 1980 and 1986.
ABSTRACT The Advanced Microwave Precipitation Radiometer (AMPR) has just completed a number of successful field deployments and will be refitted with a number of improvements to allow for improved calibration measurements and enhanced... more
ABSTRACT The Advanced Microwave Precipitation Radiometer (AMPR) has just completed a number of successful field deployments and will be refitted with a number of improvements to allow for improved calibration measurements and enhanced data processing. The AMPR is sponsored by NASA at the Marshall Space Flight Center for the investigation of precipitation using passive microwave brightness temperatures from the NASA ER-2 high altitude aircraft. The primary goal of the AMPR is the exploitation of the scattering signal of precipitation at frequencies near 18, 37, and 85 GHz together to unambiguously retrieve storm precipitation structure and intensity information from high in the storm (85 GHz) to deep within the storm (18 GHz).
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The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) was built in Japan, and it has been flying on the Aqua satellite since May 2002. Aqua has completed its prime mission in September 2008. The observations... more
The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) was built in Japan, and it has been flying on the Aqua satellite since May 2002. Aqua has completed its prime mission in September 2008. The observations from AMSR-E are being used by scientists all over the world in conjunction with other ATrain satellite instruments to monitor and understand
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The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) has been in orbit, flying on NASA's Aqua satellite,... more
The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) has been in orbit, flying on NASA's Aqua satellite, for more than four years. Scientists from around the world have been working with data from AMSR-E. The US Science Team algorithm developers have been working on validating their algorithms. All data are now being reprocessed with these new improved
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The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) continues to operate nominally on NASA's Aqua satellite. This paper provides a sampling of products from AMSR-E that are of use for a variety of... more
The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) continues to operate nominally on NASA's Aqua satellite. This paper provides a sampling of products from AMSR-E that are of use for a variety of global hydrologic investigations.
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The Advanced Microwave Scanning Radiometers (AMSR) are dual-polarized microwave radiometers having channel frequencies ranging from 6.9 GHz to 89 GHz, and were designed to retrieve global information on precipitation, sea surface... more
The Advanced Microwave Scanning Radiometers (AMSR) are dual-polarized microwave radiometers having channel frequencies ranging from 6.9 GHz to 89 GHz, and were designed to retrieve global information on precipitation, sea surface temperature, oceanic surface winds and integrated cloud water and water vapor, vegetation, sea ice, and snow cover. Two AMSR's have been built by Mitsubishi Electric Corporation for the National
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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... 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
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A combination of theory and measurement is used to develop a scattering-based method for quantitatively measuring rainfall over the ocean from Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) 37-GHz observations. This technique... more
A combination of theory and measurement is used to develop a scattering-based method for quantitatively measuring rainfall over the ocean from Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) 37-GHz observations. This technique takes the observed scattering effects of precipitation on 37-GHz brightness temperatures and applies it to the oceanic environment. It requires an estimate of the effective radiating temperature of the
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Rain rate algorithms for spring, summer and fall that have been developed from comparisons between the brightness temperatures measured by the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) and rain rates derived from... more
Rain rate algorithms for spring, summer and fall that have been developed from comparisons between the brightness temperatures measured by the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) and rain rates derived from operational WSR-57 radars over land are described. Data were utilized from a total of 25 SMMR passes and 234 radars, resulting in 12 000 observations of 1600 km2
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The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) is a conically scanning, dual-polarization, total power microwave radiometer flying on... more
The Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) is a conically scanning, dual-polarization, total power microwave radiometer flying on NASA's Aqua satellite. It has been taking global observations for more than four years. The instrument was provided by the Japan Aerospace Exploration Agency, JAXA, and it was built by Mitsubishi Electric Company. AMSR-E data provide information on
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The scattering algorithms of Spencer (1983, 1986) are applied to the December-May period from 1981-1984, to obtain the 1982-1983 December-May convective precipitation anomaly patterns associated with the El Nino/Southern Oscillation. It... more
The scattering algorithms of Spencer (1983, 1986) are applied to the December-May period from 1981-1984, to obtain the 1982-1983 December-May convective precipitation anomaly patterns associated with the El Nino/Southern Oscillation. It is shown that semiannual convective precipitation patterns over global land and ocean regions can be mapped using the volume scattering effect of precipitation-size ice on Nimbus-7 SMMR 37 GHz brightness temperature. It is suggested that the Defense Meteorological Satellite Program Special Sensor Microwave/Imager 85 GHz data (in combination with 37 and 19 GHz data) can be valuable in global surveys of precipitation patterns.
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In the remote sensing community, stability and accuracy are two critical terms that need to be used in a consistent and clear way for their use to be of maximum benefit. Their definitions in combination with the vocabulary of the ISO... more
In the remote sensing community, stability and accuracy are two critical terms that need to be used in a consistent and clear way for their use to be of maximum benefit. Their definitions in combination with the vocabulary of the ISO Guide on uncertainty analysis have been applied to long time series meas- urements using satellite instruments for climate monitoring. Based on the definitions of these terms, re- quirements have been developed for satellite instrumentation at a calibration workshop on November 12 - 14, 2002 organized by NIST, NOAA, NPOESS IPO and NASA. The background analyses that lead to some of these requirements are discussed.
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... Maryland. Corresponding author address: Paul A. Hirschberg, National Weather Service, 1325 EastWest Highway, Building SSMC2, Room 13236, Silver Spring, MD 20910. Email: Paul.Hirschberg@noaa.gov. 1. Introduction. ...
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We agree with CA Mears and FJ Wentz (The effect of diurnal correction on satellite-derived lower tropospheric temperature, Reports, 2 Sept., p. 1548; published online 11 Aug.) that our University of Alabama in Huntsville (UAH) method of... more
We agree with CA Mears and FJ Wentz (The effect of diurnal correction on satellite-derived lower tropospheric temperature, Reports, 2 Sept., p. 1548; published online 11 Aug.) that our University of Alabama in Huntsville (UAH) method of calculating a diurnal correction to ...
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... Coupled models like PCM successfully simulate many of the statistical characteristics of El Niño-induced temperature variability, although the precise timing of El Niño and La Niña events cannot be ... MF Wehner. Lawrence Berkeley... more
... Coupled models like PCM successfully simulate many of the statistical characteristics of El Niño-induced temperature variability, although the precise timing of El Niño and La Niña events cannot be ... MF Wehner. Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. ...