|
FLASHFlux TISA Terra+Aqua Version2 |
| Investigation: | FLASHFlux |
| Data Product: | Time Interpolated and Spatially Averaged (TISA) |
| Data Sets: | Terra+Aqua (Instruments: CERES-FM1 or CERES-FM2, CERES-FM3 or CERES-FM4, MODIS) |
| Data Set Family: | Version2 |
| Data Set Versions: | Version2D |
The Fast Longwave and SHortwave Flux (FLASHFlux) project is based upon the algorithms developed for and data collected by the Clouds and the Earth's Radiant Energy System (CERES) project. CERES is currently producing world-class climate data products derived from measurements taken aboard NASA's Terra and Aqua spacecrafts. While of exceptional fidelity, CERES data products require a considerable amount of processing to assure quality and verify accuracy and precision. The result is that CERES data are typically released more than six months after acquisition of the initial measurements. For climate studies, such delays are of little consequence especially considering the improved quality of the released data products. There are, however, many uses for the CERES data products on a near real-time basis. These include CERES instrument calibration and subsystem quality checks, CloudSat operations, seasonal predictions, land and ocean assimilations, support of field campaigns, outreach programs such as S'COOL, and application projects for agriculture and energy industries.
The FLASHFlux project was envisioned as a conduit whereby CERES data could be provided to the community within a week of the initial measurements, with the trade-off that some degree of fidelity would be exacted to gain speed.
The purpose of this document is to inform potential users of the FLASHFlux data of the differences between the FLASHFlux and CERES data products. This document also provides potential users with information concerning the difference between versions within the Version2 family. This document provides the data users with cautions where they could possibly misinterpret the data; links to further information about the data product, algorithms, and accuracy; and information about planned changes. Even though the FLASHFlux endeavor intends to incorporate the latest input data sets and improvements into its algorithms, there are no plans to reprocess the FLASHFlux data products once these modifications are in place. Thus, in contrast to the CERES data products, the FLASHFlux data products are not to be considered of climate quality. Users seeking climate quality should instead use the CERES data products.
The FLASHFlux Version2 data sets refer to all files within the Version2 family. When changes are made that may noticeably affect one or more output parameters, the letter which follows the version number is changed (e.g., Version5D, Version5E, and Version5F would all belong to the Version5 family of TISA files). All files with the same number belong in the same version family, regardless of the letter that follows. Substantial changes will result in a version number change, which also changes the version family. By definition, adding or removing TISA parameters will always result in a version number/family change. Every TISA version family has its own Data Quality Summary. Note that a change in the input (SSF) version will result in a change to TISA version. Typically, an SSF letter change will result in a TISA letter change and an SSF version number (family) change will result in a TISA version number change. However, the TISA version letter or number may also change independently of the SSF.
Please note, this document is a high-level summary and represents the minimum information for scientific users of this data product. We strongly urge authors, researchers, and reviewers of research papers to periodically re-check this URL for the latest status of this Data Set Version and particularly before publication of any scientific papers using the data.
FLASHFlux will typically choose to process the Terra and Aqua instruments that are in the crosstrack scan mode. To determine operations on a given day from any previous month, refer to the CERES Operations in Orbit. FLASHFlux TISA is a daily product produced by combining Terra and Aqua data and interpolating inside a 3-day window.
A full list of parameters on the TISA is contained in the TISA Data Parameters page; however, only the daily averaged flux products have been fully validated. Current efforts are underway to validate the hourly averaged flux products, and when completed will be noted in this document.
This Data Quality Summary is written for all TISA files within the Version2 family.
When referring to a FLASHFlux data set, please include FLASHFlux, the specific data set version or the data set version family, and the data product. Multiple files that are identical in all aspects of the filename except for the 6 digit configuration code (number to the left of the data date) differ little scientifically. Thus, users may analyze FLASHFlux data from the same data set version and data product without regard to configuration code. If all the files come from one data set version, refer to the data set using that specific data set version. For example, users working only with Version2D files should refer to "FLASHFlux Version2D TISA." If the files are from numerous data set versions of the same family, then refer to the data set as "FLASHFlux Version2 TISA.";
Users should analyze FLASHFlux data sets from different version families separately.
Both FLASHFlux and CERES make use of the same SW Model B and LW Model B algorithms. These models are also named Langley Parameterized SW Algorithm (LPSA) and Langley Parameterized LW Algorithm (LPLA) respectively. Hence, both FLASHFlux and CERES rely on similar input data sets from the meteorological products and MODIS.
FLASHFlux will provide high quality data sets to the community within a week of the initial measurements. The FLASHFlux data sets will not be reprocessed into consistent time series records.
FLASHFlux input data sets and algorithms will change as improvements become available.
FLASHFlux SSF processes very shortly after the data date, and therefore, there may be gaps. Also, FLASHFlux TISA is a daily product derived by combining inputs from both Terra and Aqua while CERES TISA is a monthly product derived for each satellite separately.
CERES produces a non-GEO product and a GEO product by bringing in geostationary satellite data to improve temporal sampling characteristics. So far, FLASHFlux is a non-GEO product only.
CERES Rev1 corrections are included in the special set of correction coefficients used by FLASHFlux and should not be applied again by the user.
Data from only one Terra and one Aqua instrument are processed each day. The selected instrument is typically in the crosstrack mode of operation. When possible, the data from the same instrument are processed for the entire month. To determine the mode of operations for each instrument in previous months, users should refer to CERES Operations in Orbit. Available data from the Terra and Aqua instrument are combined in the TISA product.
FLASHFlux only produces data sets for one crosstrack CERES instrument from each satellite. The instrument in crosstrack mode for a satellite may change over time. Instrument operation modes typically change at a monthly boundary and are seldom made in the middle of a month. When a failure or anomaly is detected, the instrument FLASHFlux processes may abruptly switch in the middle of a month.
Users should not apply the Rev1 user applied revisions discussed in the CERES Data Quality Summaries to any FLASHFlux data set. As Rev1 scaling factors become available, they will be included in the FLASHFlux data sets via the set of correction coefficients used to unfilter the CERES radiances.
Users should note that only the daily averaged flux products have been fully validated. Current efforts are underway to validate the hourly averaged flux products, and when completed will be noted in this document.
Users who need to know whether the hour box data was extrapolated, interpolated, or associated with an actual observation should consult the Quality Assurance byte in the Quality Assurance Vgroup. The bit definitions are as follows:
if actual observation, bit0 == 0:It should be noted that in the above situation (bit0 == 1), if bit1=0, then bit3 will not have a meaningful value. Similarly, if bit2=0, then bit4 will not have a meaningful value.
The Model B surface flux parameters have been validated for the Version2 family of data sets. These surface fluxes are computed for all-sky conditions.
Validation of the FLASHFlux results is actively being pursued. The accuracy of FLASHFlux results will be documented as they become available.
The Langley Parameterized Shortwave Algorithm (LPSA) described in Gupta et al. (2001) was developed to provide a fast radiative transfer method to derive the Earth's shortwave (SW) surface radiation budget. Both CERES and FLASHFlux projects use this algorithm for deriving instantaneous Single Scanner Footprint (SSF) and Time Interpolation and Spatial Averaging (TISA) data products. This algorithm is also used by WCRP/GEWEX Surface Radiation Budget (SRB) project for deriving global surface insolation products. The LPSA consists of physical parameterizations that account for the attenuation of solar radiation in simple terms separately for clear and cloudy atmospheres.
The Langley Parameterized Longwave Algorithm (LPLA) is a fast parameterization derived from an accurate narrowband radiative transfer model (Gupta 1989; Gupta et al. 1992). The LPLA is also used by both CERES and FLASHFlux projects for deriving SSF and TISA products and by WCRP/GEWEX SRB project for deriving global LW fluxes. The LPLA computes downward LW flux (DLF) in terms of an effective emitting temperature of the atmosphere, the column water vapor, the fractional cloud amount, and the cloud-base height for each footprint. The effective emitting temperature and column water vapor are computed from temperature and humidity profiles available from the MOA database. Fractional cloud amount and cloud-base height are available from the CERES cloud subsystem.
FLASHFlux will not be able to hold the TISA processing constant. As inputs and algorithms change, the quality of the data product will also change. Minor changes that do not impact the science will be denoted by an increase in the 6 digit configuration code that appears just before the data date and hour. Changes that impact the science enough to be noted will result in a letter change within the data set version. Major changes will result in a change to the data set family.
The following are expected to have an impact on the FLASHFlux TISA:
The FLASHFlux and CERES Teams have gone to considerable trouble to remove major errors and to verify the quality and accuracy of this data. Please provide a reference to the following papers when you publish scientific results with the CERES data:
Wielicki, B. A., B. R. Barkstrom, E. F. Harrison, R. B. Lee III, G. L. Smith, and J. E. Cooper, 1996: Clouds and the Earth's Radiant Energy System (CERES): An Earth Observing System Experiment, Bull. Amer. Meteor. Soc., 77, 853-868.
Stackhouse, P. W., D. P. Kratz, G. R. McGarragh, S. K. Gupta, and E. B. Geier, 2006: Fast Longwave and Shortwave Radiative Flux (FLASHFlux) Products From CERES and MODIS Measurements. 12th Conference on Atmospheric Radiation, American Meteorological Society, Madison, Wisconsin, 10-14 July 2006.
When Langley Atmospheric Science Data Center (ASDC) data are used in a publication, we request the following acknowledgment be included:
"These data were obtained from the NASA Langley Atmospheric Science Data Center."
The Langley ASDC requests two reprints of any published papers or reports which cite the use of data that we have distributed. This will help us determine the use of data that we distribute, which is helpful in optimizing product development. This also helps us to keep the product related references current.
To assist the Langley Atmospheric Science Data Center in providing the best service to the scientific community, we request notification if you transmit these data to other researchers.
For questions or comments on the FLASHFlux Quality Summary, contact the User and Data Services staff at the Atmospheric Science Data Center.
A Portable Document Format (PDF) reader (such as Adobe Acrobat Reader) is required to open and view PDF documents.
