Kathryn A. Bush

Reexamination of the Observed Decadal Variability of the Earth Radiation Budget Using Altitude-Corrected ERBE/ERBS Nonscanner WFOV Data

Abstract This paper gives an update on the observed decadal variability of the earth radiation budget (ERB) using the latest altitude-corrected Earth Radiation Budget Experiment (ERBE)/Earth Radiation Budget Satellite (ERBS) Nonscanner Wide Field of View (WFOV) instrument Edition3 dataset. The effects of the altitude correction are to modify the original reported decadal changes in tropical mean (20°N to 20°S) longwave (LW), shortwave (SW), and net radiation between the 1980s and the 1990s from 3.1, −2.4, and −0.7 to 1.6, −3.0, and 1.4 W m−2, respectively. In addition, a small SW instrument drift over the 15-yr period was discovered during the validation of the WFOV Edition3 dataset. A correction was developed and applied to the Edition3 dataset at the data user level to produce the WFOV Edition3_Rev1 dataset. With this final correction, the ERBS Nonscanner-observed decadal changes in tropical mean LW, SW, and net radiation between the 1980s and the 1990s now stand at 0.7, −2.1, and 1.4 W m−2, respectivel...

On-orbit radiometric calibrations of the Earth Radiation Budget Experiment (ERBE) active-cavity radiometers on the Earth Radiation Budget Satellite (ERBS)

Between November 1984 and July 2002, the Earth Radiation Budget Satellite (ERBS)/Earth Radiation Budget Experiment (ERBE) nonscanning, active cavity radiometers (ACR) were used to measure incoming total solar irradiance, earth-reflected solar irradiance, and earth-emitted outgoing longwave radiation (OLR) irradiance. The ERBE shortwave wide field-of view (SWFOV) and toal wide field-of-view (TWFOV) ACRs measured irradiances from the entire earth disc in the shortwave (0.2-5.0 μm) and total (0.2-100 μm) broadband spectral regions. On-orbit, the ACRs observations of the incoming total solar irradiance, and of reference irradiance from on-board tungsten lamp and blackbodies were used to determine drifts and shifts in the ACR responses/gains. In the cases of the SWFOV ACR, its response/gain changed as much as 8.8% while the TWFOV response was stable at levels better than 0.1%. The precise measurements of gain and offset variations have permitted the generations of ERBE level 1 data products [earth-reflected solar (≈240 Wm-2)and earth-emitted (≈100 Wm-2) irradiances] at the precision levels better than 0.3 Wm-2. In this paper, the ACR radiometric on-orbit calibration approaches and systems are outlined.

Time-Sampling Errors of Earth Radiation From Satellites: Theory for Outgoing Longwave Radiation

The measurements of radiation budget by satellites in low Earth orbit provide limited sampling of the diurnal cycle. Thus, maps of monthly mean radiation fluxes contain errors due to this limitation. The Earth Radiation Budget Experiment reduced these errors in the data products by using a half-sine fit to account for regional diurnal cycles. An algorithm is presented to compute errors that are created when one computes the average value of outgoing longwave radiative flux (OLR) for a month based on the half-sine fit. Details of the temporal sampling are described by a sampling matrix that gives the number of OLR measurements in each local hour and each day of the month. The error analysis must take into account the correlation in time between irregularly spaced data due to synoptic variations, the weighting of measurements to accommodate the half-sine fit and deviations of the regional diurnal cycle from the half-sine. Using these ingredients, a closed-form expression is presented for the standard deviation of the temporal-sampling errors of the monthly mean OLR as computed from satellite measurements. The method is demonstrated for a well-sampled case and a poorly sampled case. This approach can be used to evaluate data products for existing measurements and for future mission design, or evaluating measurements of other atmospheric parameters.

On-orbit calibrations of the ERBE active-cavity radiometers on the Earth Radiation Budget Satellite (ERBS): 1984-2002

From October 1984 until September 30, 1999, on-orbit, the Earth Radiation Budget Satellite (ERBS)/Earth Radiation Budget Experiment (ERBE) nonscanning, active cavity radiometers (ACR) were calibrated using observations of the incoming total solar irradiance, and of reference irradiances from an on-board tungsten lamp and blackbodies in order to determine drifts and shifts in the ACR responses. On October 7, 1999, the ERBE elevation drive system failed near the earth nadir viewing configuration. Thereafter, the elevation failure prevented observations of the on-board, built-in calibration systems. On July 23, August 8, and December 10, 2002, the ERBS was pitched 180 degrees to observe cold space, representative of a 3 Kelvin blackbody, in order to determine the ACRs zero-irradiance offsets. On December 4, 2002, the ERBS was pitched 180 degrees away from the earth in order to observe the sun, and to determine the ACRs gains. In this paper, the 2002, 180-degree pitch calibrations are compared with the earlier 1984-1999, calibrations which were obtained using the on-orbit, built-in calibration systems. In addition, the 2002 calibrations are compared with earlier scheduled November 21, 1984, and October 20, 1985, 180-degree pitch calibrations, as well as with deep space calibrations from unscheduled July 2, 1987, January 16, 1999, and November 16, 2000, ERBS spacecraft tumbles. The 2002 ACR offsets were found to be consistent with 1984-2000 offsets at the 1.0 Wm-2. 1984-1999, ERBE top-of-the-atmosphere (TOA), and satellite altitude (SA) earth irradiances are presented. Analyses of the TOA ERBE earth irradiances indicate that the TOA irradiance time series exhibited a 1.7 Wm-2 increase as a result of 1988-1992, and 1998-2002 satellite altitudinal decreases during periods of maximum solar magnetic activity.

A scientific digital library in context: an earth radiation budget experiment collection in the atmospheric sciences data center digital library

At the NASA Langley Research Center, the Earth Radiation Budget Experiment (ERBE) Data Management Team and the Atmospheric Sciences Data Center are developing a digital collection for the ERBE project. The main goal is long-term preservation of a comprehensive information environment. The secondary goal is to provide a context for these data products by centralizing the 25-year research projects scattered information elements. The development approach incorporates elements of rapid prototyping and user-centered design in a standards-based implementation. A working prototype is in testing with a small number of users.

Twelve-month running trends from Earth Radiation Budget Satellite (ERBS) active-cavity radiometric measurements and global surface temperatures

Four earth-viewing nonscanning active cavity radiometers of the ERBS (Earth Radiation Budget Satellite) have been measuring the radiation arising from the earth-atmosphere system since its’ launch day, October 5, 1984. The ERBS spacecraft was placed in a non-sun-synchronous trajectory inclined at 57°. Two radiometers out of four, namely the wide field-of-view total (WFOV-T) radiometer which measures the radiation in the total spectral band of 0.2 - 100 μm, and the wide-field-of-view shortwave (WFOV-SW) radiometer measures the Earth’s reflected radiation in the wavelength region of 0.2 - 5 μm were used in this study. These sensors were calibrated continuously by observing the in-flight internal black bodies as well as the Sun every two weeks. The WFOV-T channel was found very stable within 0.1%. The monthly flux values of the ERBS nonscanning active cavity radiometers at satellite altitude and the corresponding NCDC (National Climatic Data Center) global surface temperature data for the period of fifteen years (1985-1999) were used in this paper. The effect of Mt. Pinatubo eruption is very clearly noticeable in the running trends of both WFOV-T and WFOV-SW radiometric measurements. Further the resulting twelve month running trends derived from the outgoing longwave radiation was found to follow the twelve month running trend determined from the global surface temperature data set. Both trends are real and increasing. The “global-cooling-like” event caused by the Mt. Pinatubo eruption was also found under both day and nighttime conditions.

On-orbit characterizations of Earth Radiation Budget Experiment broadband shortwave active cavity radiometer sensor responses

The NASA Earth Radiation Budget Experiment (ERBE) missions were designed to monitor long-term changes in the earth radiation budget components which may cause climate changes. During the October 1984 through September 2004 period, the NASA Earth Radiation Budget Satellite (ERBS)/ERBE nonscanning active cavity radiometers (ACR) were used to monitor long-term changes in the earth radiation budget components of the incoming total solar irradiance (TSI), earth-reflected TSI, and earth-emitted outgoing longwave radiation (OLR). The earth-reflected total solar irradiances were measured using broadband shortwave fused, waterless quartz (Suprasil) filters and ACR’s that were covered with a black paint absorbing surface. Using on-board calibration systems, 1984 through 1999, long-term ERBS/ERBE ACR sensor response changes were determined from direct observations of the incoming TSI in the 0.2-5 micrometer shortwave broadband spectral region. During the October 1984 through September 1999 period, the ERBS shortwave sensor responses were found to decrease as much as 8.8% when the quartz filter transmittances decreased due to direct exposure to TSI. On October 6, 1999, the on-board ERBS calibration systems failed. To estimate the 1999-2004, ERBS sensor response changes, the 1984-1997 NOAA-9, and 1986-1995 NOAA-10 Spacecraft ERBE ACR responses were used to characterize response changes as a function of exposure time. The NOAA-9 and NOAA-10 ACR responses decreased as much as 10% due to higher integrated TSI exposure times. In this paper, for each of the ERBS, NOAA-9, and NOAA-10 Spacecraft platforms, the solar calibrations of the ERBE sensor responses are described as well as the derived ERBE sensor response changes as a function of TSI exposure time. For the 1984-2003 ERBS data sets, it is estimated that the calibrated ERBE earth-reflected TSI measurements have precisions approaching 0.2 Watts-per-squared-meter at satellite altitudes.

The earth radiation budget experiment (ERBE) 15-year data set

The availability of a 15-year data set of radiative fluxes from the Earth Radiation Budget Experiment (ERBE) allows us to investigate the interannual variability of top-of-the-atmosphere (TOA) outgoing longwave radiation (OLR) and reflected shortwave radiation (SWR). Variance maps and empirical orthogonal function (EOF) analysis are used to describe temporal and spatial patterns of variability.

Measurements of filtered lunar radiances using the NASA Terra spacecraft/CERES thermistor bolometer sensors during 2000 and 2001

Studies were conducted to define lunar radiances on an absolute radiometric scale tied to the International Temperature Scale of 1990 (ITS-90). The Clouds and the Earths Radiant Energy System (CERES) thermistor bolometer sensor instruments were used to measure lunar radiances from the NASA Tropical Rainfall Measuring Mission (TRMM), Terra, and Aqua spacecraft platforms. Each CERES instrument package consisted of three different sensors: (1) broadband shortwave [0.3 to 5 micrometers]; (2) broadband total [0.3 to >100 micrometers]; and (3) narrowband, water vapor window [8 to 12 micrometers]. Moon-reflected solar radiances were measured with the shortwave sensor while both moon-reflected solar and moon-emitted longwave radiances were measured using the total sensor. The differences between the total and shortwave sensor measurements were used to determine the broadband longwave, moon-emitted radiances. The narrowband, water vapor window sensor measured only the longwave, moon-emitted radiances. The radiances were obtained as a function of phase angle (formed at the moon between directions to the sun and the spacecraft). The resulting filtered radiances were normalized to the mean sun-moon distance, one astronomical unit (AU), and to the mean earth-moon distance of 0.0026 AU (384,400 kilometers). 1998, 2000, and 2001, CERES lunar filtered measurements are presented, compared, and analyzed. Additional measurements are presented from the January 9, 2001, and May 16, 2003, total lunar eclipse events. Analyses of the Clouds and the Earths Radiant Energy System (CERES) thermistor bolometer sensor observations of lunar radiances indicated that broadband shortwave and longwave lunar filtered radiances can be linked to a radiometric scale based upon an International Temperature Scale of 1990 (ITS-90) at absolute levels approaching ± 0.2 Wm-2sr-1. For a lunar image diameter of 31 minutes of arc, an emitting lunar disc temperature of approximately 400 Kelvin was estimated from the longwave radiances near 7-degree phase angle. The integration of the CERES unfiltered radiances over all reflection angles can be used to define the moon radiation budget (MRB).

Ground calibrations of the Clouds and the Earth's radiant energy System (CERES) instrument for the tropical rainfall measuring mission (TRMM)

Clouds and the Earths radiation energy system (CERES), a key experiment in the Earth observing system (EOS), is designed to measure the reflected shortwave and the emitted longwave radiances from Earth and its atmosphere. The CERES instrument consists of a scanning thermistor bolometer package with built in flight calibration systems. The first CERES instrument is scheduled for launch in 1997 aboard the joint National Aeronautics and Space Administration (NASA) and Japanese National Space Development Agency (NASDA) tropical rainfall measuring mission (TRMM) spacecraft. The laboratory calibrations of the instrument were conducted in the TRW vacuum facilities which are equipped with blackbodies, a cryogenically cooled transfer active-cavity radiometer, shortwave reference source, solar simulator and a constant radiance reference source. This paper describes the calibration facility and the calibration procedures for the CERES instrument.