The CLARREO mission addresses the need to provide accurate, broadly acknowledged climate records that can be used
to validate long-term climate projections that become the foundation for informed decisions on mitigation and adaptation
policies. The CLARREO mission accomplishes this critical objective through rigorous SI traceable decadal change
observations that will reduce the key uncertainties in current climate model projections. These same uncertainties also
lead to uncertainty in attribution of climate change to anthropogenic forcing. CLARREO will make highly accurate and
SI-traceable global, decadal change observations sensitive to the most critical, but least understood climate forcing,
responses, and feedbacks. The CLARREO breakthrough is to achieve the required levels of accuracy and traceability to
SI standards for a set of observations sensitive to a wide range of key decadal change variables. The required accuracy
levels are determined so that climate trend signals can be detected against a background of naturally occurring
variability. The accuracy for decadal change traceability to SI standards includes uncertainties associated with
instrument calibration, satellite orbit sampling, and analysis methods. Unlike most space missions, the CLARREO
requirements are driven not by the instantaneous accuracy of the measurements, but by accuracy in the large time/space
scale averages that are necessary to understand global, decadal climate changes.
The Clouds and the Earth's Radiant Energy System (CERES) Flight Model-5 (FM-5) instrument will fly on the
NPOESS Preparatory Project spacecraft, which has a launch-readiness date of no earlier than June, 2010. This
mission continues the critical Earth Radiation Budget Climate Data Record begun by the Earth Radiation Budget
Experiment instruments in the mid 1980's and continued by the CERES instruments currently flying on the Terra
and Aqua spacecraft. This paper outlines lessons learned on the existing CERES instruments from 30+ years of
flight experience and presents a radiometric protocol to ensure that the FM-5 instrument performance exceeds the
calibration and stability goals.
This paper documents the development of the first integrated data set of global vertical profiles of clouds, aerosols, and
radiation using the combined NASA A-Train data from the Aqua Clouds and Earth's Radiant Energy System (CERES)
and Moderate Resolution Imaging Spectroradiometer (MODIS), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite
Observations (CALIPSO), and CloudSat. As part of this effort, cloud data from the CALIPSO lidar and the CloudSat
radar are merged with the integrated column cloud properties from the CERES-MODIS analyses. The active and
passive datasets are compared to determine commonalities and differences in order to facilitate the development of a
3-dimensional cloud and aerosol dataset that will then be integrated into the CERES broadband radiance footprint.
Preliminary results from the comparisons for April 2007 reveal that the CERES-MODIS global cloud amounts are, on
average, 0.14 less and 0.15 greater than those from CALIPSO and CloudSat, respectively. These new data will provide
unprecedented ability to test and improve global cloud and aerosol models, to investigate aerosol direct and indirect
radiative forcing, and to validate the accuracy of global aerosol, cloud, and radiation data sets especially in polar regions
and for multi-layered cloud conditions.
It is estimated that in order to best detect real changes in the Earth's climate system, space based instrumentation
measuring the Earth Radiation Budget (ERB) needs to remain calibrated with a stability of 0.3% per decade.
This stability is beyond the specification of existing ERB programs such as the Clouds and the Earth's Radiant
Energy System (CERES, using three broadband radiometric scanning channels: the shortwave 0.3 - 5μm, total
0.3- > 100μm, and window 8 - 12μm). It is known that when in low earth orbit, optical response to blue/UV
radiance can be reduced significantly due to UV hardened contaminants deposited on the surface of the optics.
Typical onboard calibration lamps do not emit sufficient energy in the blue/UV region, hence this darkening
is not directly measurable using standard internal calibration techniques. This paper details a study using a
model of contaminant deposition and darkening, in conjunction with in-flight vicarious calibration techniques, to
derive the spectral shape of darkening to which a broadband instrument is subjected. The model ultimately uses
the reflectivity of Deep Convective Clouds as a stability metric. The results of the model when applied to the
CERES instruments on board the EOS Terra satellite are shown. Given comprehensive validation of the model,
these results will allow the CERES spectral responses to be updated accordingly prior to any forthcoming data
release in an attempt to reach the optimum stability target that the climate community requires.
It is estimated that in order to best detect real changes in the Earth's climate system, space based instrumentation measuring the Earth Radiation Budget (ERB) must remain calibrated with a stability of 0.3% per decade. Such stability is beyond the specified accuracy of existing ERB programs such as the Clouds and the Earth's Radiant Energy System (CERES, using three broadband radiometric scanning channels: the shortwave 0.3 - 5μm, total 0.3- > 100μm, and window 8 - 12μm). It has been shown that when in low earth orbit, optical response to blue/UV radiance can be reduced significantly due to UV hardened contaminants deposited on the surface of the optics. Since typical onboard calibration lamps do not emit sufficient energy in the blue/UV region, this darkening is not directly measurable using standard internal calibration techniques. This paper describes a study using a model of contaminant deposition and darkening, in conjunction with in-flight vicarious calibration techniques, to derive the spectral shape of darkening to which a broadband instrument is subjected. Ultimately the model uses the reflectivity of Deep Convective Clouds as a stability metric. The results of the model when applied to the CERES instruments on board the EOS Terra satellite are shown. Given comprehensive validation of the model, these results will allow the CERES spectral responses to be updated accordingly prior to any forthcoming data release in an attempt to reach the optimum stability target that the climate community requires.
MODIS aerosol retrievals over ocean from Terra and Aqua platforms are available from the Clouds and the Earth's Radiant Energy System (CERES) Single Scanner Footprint (SSF) datasets generated at NASA Langley Research Center (LaRC). Two aerosol products are reported side by side. The primary M product is generated by subsetting and remapping the multi-spectral (0.44 - 2.1 μm) MOD04 aerosols onto CERES footprints. MOD04 processing uses cloud screening and aerosol algorithms developed by the MODIS science team. The secondary (AVHRR-like) A product is generated in only two MODIS bands: 1 and 6 on Terra, and ` and 7 on Aqua. The A processing uses NASA/LaRC cloud-screening and NOAA/NESDIS single channel aerosol algorthm. The M and
A products have been documented elsewhere and preliminarily compared using two weeks of global Terra CERES SSF (Edition 1A) data in December 2000 and June 2001. In this study, the M and A aerosol optical depths (AOD) in MODIS band 1 and (0.64 μm), τ1M and τ1A, are further checked for cross-platform consistency using 9 days of global Terra CERES SSF (Edition 2A) and Aqua CERES SSF (Edition 1A) data from 13 - 21 October 2002.
KEYWORDS: Sensors, Space operations, Calibration, Solar radiation, Satellites, Shortwaves, Solar energy, Radiometry, Clouds, Bidirectional reflectance transmission function
The Geostationary Earth Radiation Budget (GERB) instrument aboard the Meteosat Second Generation Satellite has 256 channels which measure total radiance and 256 channels which measure solar radiation reflected from the Earth. In order to validate the calibration of these channels, the Clouds and Earth Radiant Energy System (CERES) instrument aboard the Terra spacecraft is operated in such a way as to view Earth scenes from the same direction as the GERB, so as to measure the same total and reflected solar radiances. The method uses the capability to program the azimuth of the CERES scan plane, such that the scan plane includes the GERB.
The NASA CERES Project has developed a combined radiation and cloud property dataset using the CERES scanners and matched spectral data from high-resolution imagers, the Visible Infrared Scanner (VIRS) on the Tropical Rainfall Measuring Mission (TRMM) satellite and the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua. The diurnal cycle can be well-characterized over most of the globe using the combinations of TRMM, Aqua, and Terra data. The cloud properties are derived from the imagers using state-of-the-art methods and include cloud fraction, height, optical depth, phase, effective particle size, emissivity, and ice or liquid water path. These cloud products are convolved into the matching CERES fields of view to provide simultaneous cloud and radiation data at an unprecedented accuracy. Results are available for at least 3 years of VIRS data and 1 year of Terra MODIS data. The various cloud products are compared with similar quantities from climatological sources and instantaneous active remote sensors. The cloud amounts are very similar to those from surface observer climatologies and are 6-7% less than those from a satellite-based climatology. Optical depths are 2-3 times smaller than those from the satellite climatology, but are within 5% of those from the surface remote sensing. Cloud droplet sizes and liquid water paths are within 10% of the surface results on average for stratus clouds. The VIRS and MODIS retrievals are very consistent with differences that usually can be explained by sampling, calibration, or resolution differences. The results should be extremely valuable for model validation and improvement and for improving our understanding of the relationship between clouds and the radiation budget.
12 There are 2 CERES scanning radiometer instruments aboard the TERRA spacecraft, one for mapping the solar radiation reflected from the Earth and the outgoing longwave radiation and the other for measuring the anisotropy of the radiation. Each CERES instrument has on-board calibration devices, which have demonstrated that from ground to orbit the broadband total and shortwave sensor responses maintained their ties to the International Temperature Scale of 1990 at precisions approaching radiances have been validated in orbit to +/- 0.3 percent (0.3 W m-2sr-1). Top of atmosphere fluxes are produced by use of the CERES data alone. By including data from other instruments, surface radiation fluxes and radiant fluxes within the atmosphere and at its top, shortwave and longwave, for both up and down components, are derived. Validation of these data products requires ground and aircraft measurements of fluxes and of cloud properties.
Current uncertainties in the effects of aerosols and clouds on the Earth radiation budget limit our understanding of the climate system and the potential for global climate change. PICASSO-CENA is a recently approved satellite mission within NASA's Earth System Science Pathfinder (ESSP) program designed to address these uncertainties. The PICASSO-CENA payload includes a lidar and three passive instruments which will provide unique information on the global distribution and properties of aerosols and clouds. PICASSO-CENA will be flown in formation with the EOS PM and CloudSat satellites to provide coincident measurements of atmospheric state, radiative fluxes, and thick clouds. This global suite of measurements will provide a basis for improving the representation of clouds and aerosols in climate models, leading to improved capabilities for predicting climate and climate change. PICASSO-CENA is planned for a three year mission beginning in early 2003 and is being developed within the framework of a collaboration between NASA and CNES.
NASA's Earth Observing System (EOS) is part of an international program for studying the Earth from space using a multiple-instrument, multiple-satellite approach. The Clouds and the Earth's Radiant Energy System (CERES) experiment is designed to monitor changes in the Earth's radiant energy system and cloud systems and to provide these data with sufficient simultaneity and accuracy to examine critical cloud/climate feedback mechanisms which may play a major role in determining future changes in the climate system. The first EOS satellite (Terra), scheduled for launch this year, and the EOS-PM satellite, to be launched in late 2000, will each carry two CERES instruments. The first CERES instrument was launched in 1997 on the Tropical Rainfall Measuring Mission (TRMM) satellite. The CERES TRMM data show excellent instrument stability and a factor of 2 to 3 less error than previous Earth radiation budget missions. The first CERES data products have been validated and archived. The data consist of instantaneous longwave and shortwave broadband radiances, top- of-atmosphere fluxes, scene types, and time and space averaged fluxes and albedo. A later data product will combine CERES radiances and high-resolution image data to produce cloud properties and fluxes throughout the atmosphere and at the surface.
The Clouds and Earth's Radiant Energy System (CERES) experiment, the first satellite project devoted to monitoring cloud macrophysical and microphysical properties simultaneously with the broadband radiation field, is designed to dramatically improve our understanding of the relationship between clouds and the Earth's radiation budget. The first CERES instruments flew on the Tropical Rainfall Measuring Mission (TRMM) satellite between 35 degrees N and 35 degrees S with the Visible Infrared Scanner (VIRS), a 2-km resolution imager with five channels: 0.65, 1.6, 3.75, 10.8, and 12 micrometer beginning in January 1998. Cloud amount, height, temperature, phase, effective particle size, and water path are derived from the VIRS radiances and validated using surface radar and lidar data. Droplet radii are largest over ocean and smallest over land. Mean droplet radius is larger than that from earlier studies. The mean ice diameter is 61 micrometer. Variations of cloud parameters with temperature and viewing and solar zenith angle are given. Surface observations of liquid water path and droplet size agree well with the VIRS retrievals. This is the first analysis of cloud microphysical properties covering all times of day using all available pixels and viewing angles for half of the globe. Seasonal and diurnal variations of the cloud properties are presented.
The National Aeronautics and Space Administration (NASA) is studying options for future space-based missions, building upon the measurements to be made by the first series of Earth Observing System (EOS) missions. One mission under consideration is the NPOESS Preparatory Project (NPP), a cooperative mission of NASA and the National Polar-orbiting Operational Environmental Satellite System (NPOESS). This mission would utilize new instrument technologies being developed by the NPOESS, with additional NASA requirements, to continue certain measurements from the first series of EOS missions. By flying in the 2005 time period, NPP would provide an early demonstration and validation of new instrument technologies and algorithms in support of future NPOESS missions and extend the critical time series measurements of EOS.
The first CERES instrument has been placed in orbit on the TRMM Spacecraft. This instrument is designed to measure the Earth's radiation budget and also the anisotropy of reflected solar radiation and outgoing longwave radiation. The TRMM orbit and the combination of CERES with other instruments aboard the spacecraft provide a unique opportunity for a number of scientific studies. Results from the on-board calibration system compared well with ground calibrations. Data products include radiant fluxes at the top of the atmosphere', surface reflected solar and longwave radiant fluxes and cloud-radiative interactions.
The Clouds and Earth Radiant Energy System (CERES) instrument is designed to measure the Earth's radiation budget and also to make measurements from which the anisotropy of reflected solar radiation can be computed. The instrument design, which is based on the Earth Radiation Budget Experiment (ERBE), and its operations are described. The instrument can scan in elevation and azimuth simultaneously. The azimuthal rotation is important for gathering data to describe the anisotropy of the reflected solar radiance field. The ground vacuum calibration facility ties the calibration of the instrument to the International Temperature Scale of 1990. In-flight calibration sources are included to maintain and demonstrate the required 1 percent accuracy of each mission. Flight operations to achieve the accuracy are also discussed. The CERES Proto-Flight Model is flying on the Tropical Rainfall Measurement Mission spacecraft and successive models are scheduled to fly aboard the EOS/AM-1 and EOS/PM-1 platforms. The objectives of each flight of the instrument are discussed.
We attempt to bound microphysical properties of cirrus clouds via complementary satellite, rawinsonde, and lidar data analysis and radiative transfer modeling. Data acquired during the 1991 FIRE (First ISSCP Regional Experiment) Cirrus IFO (intensive field operation) includes AVHRR (advanced very high resolution radiometer) LAC (local area coverage), satellite imagery, high temporal resolution rawinsonde data, and lidar backscatter and depolarization information. We use the complementary rawinsonde and lidar data to generate profiles of the atmosphere, to place clouds at the correct height, and to verify the complex mixed phase nature of high altitude cirrus. Using the DISORT radiative transfer model (Stamnes et al., 1988), we generate brightness temperatures for a range of optical depths for single- and/or multi-level cloud systems composed of water or ice spheres or ice hexagons.
The clouds and the earth's radiant energy system (CERES) experiment will provide consistent data bases of radiation and cloud fields. The CERES instrument consists of a scanning thermistor bolometer package with built-in flight calibration systems. Two bolometer packages will be launched on the earth observing system (EOS) platforms to measure the Earth/atmosphere-reflected solar shortwave and Earth/atmosphere-emitted long wave radiances with measurement accuracy goals approaching 1.0% and 0.5%, respectively. In each package, there are three different bolometers. All bolometers will be calibrated in a unique TRW vacuum facility equipped with blackbodies, a cryogenically cooled active-cavity radiometer, shortwave sources, and other specialized calibration devices. The blackbodies are tied to the International Temperature Scale of 1990 (ITS'90). Using math models, the calibration measurements will define the instrument filtered gains and offsets. This paper outlines the CERES instrument design and radiometric calibrations.
Satellite measurements from the Earth Radiation Budget Experiment (ERBE) are providing important quantitative data on the diurnal variability of broadband shortwave and longwave radiation. The results derived from the combination of the Earth Radiation Budget Satellite (ERBS) and NOAA-9 indicate that the largest diurnal variations in longwave radiation occur typically over deserts and over land areas which experience intense convective activity. Maximum values of the albedo diurnal amplitude factor are over oceans. Seasonal and cloud cover variations have important effects on the diurnal cycles of Earth's radiation budget. ERBE results derived for individual regions are in substantial agreement with the diurnal results derived from the Geostationary Operational Environmental Satellite (GOES) measurements.
Scanning radiometers aboard satellites have been employed for over a decade to measure the Earth radiation budget. The measured radiance is converted to flux at the top of the atmosphere by applying angular dependence models (ADM''s) that are a function of the viewing geometry and the scene type. This paper examines the significance of the number of ADM''s used a measure of the effectiveness of the ADM''s and the implications of requiring the ADM''s to satisfy reciprocity. The overall significance of the ADM''s is determined by analyzing the same satellite data with a single Lambertian model a single mean model and the 12 Earth Radiation Budget Experiment (ERBE)1 ADM''s. The ERBE ADM''s will undergo reexamination and possible improvement before they are applied to the future Clouds and the Earth''s Radiant Energy System (CERES) radiation measurements. To measure the improvement of the models we develop a test of " goodness" for the models which includes normality reciprocity and uniformity of flux estimates determined from different viewing geometries. Alongtrack scan data are used for this test of the ADM''s. We discuss the task of constraining the standard ERBE ADM''s to satisfy the reciprocity condition. Earth Radiation Budget Satellite (ERBS) data are used to demonstrate the effect of these modified models. 1. FORMULATION OF ADM''S The radiance L at a point in Wm2sr1 is given by L (1) where M is the flux in
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