GLOBAL CLIMATE OBSERVING SYSTEM
ESSENTIAL CLIMATE VARIABLE - Albedo |
| Domain | Terrestrial | Description | The albedo of a land surface is the non-dimensional ratio of the radiation flux reflected by a (typically horizontal) surface in all directions and the incoming irradiance, which is the radiation flux from the upper hemisphere. This is technically known as the bi-hemispherical reflectance factor (BHR), and both fluxes must be relative to the same spectral range. For bare soils and other solid, convex objects, the material interface between the ground and the atmosphere constitutes the reference surface. In the case of vegetation, a reference surface is typically defined at or near the top of the canopy and must be specified explicitly. This “generic” albedo is highly variable in space and time as a result of changes in surface properties (snow deposition and melting, changes in soil moisture and vegetation cover, etc.), as a function of fluctuations in the illumination conditions (solar angular position, atmospheric effects, cloud properties, etc.), and with human activities (e.g. clearing and planting forests, sowing and harvesting crops, burning rangeland, etc.).
Albedo is thus not an intrinsic surface property, but a joint property of the surface and the overlying atmosphere, since the latter's composition (gases, clouds and aerosols) significantly affects the spectral and directional distribution of the irradiance.
Albedo is both a forcing variable affecting the climate and a sensitive indicator of environmental degradation. [GCOS-195 6.3.9] |
| Sub-domain | - |
| Full Name | Albedo |
| Satellite Signficant Contribution | Yes  |
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| GCOS Actions |
Action
Status* | Description | Who | Time Frame | Performance Indicator | Cost Implications |
T3
Cat-D | Development of a subset of current LTER and FLUXNET sites into a global terrestrial reference network for monitoring sites with sustained funding perspective, and collocated measurements of meteorological ECVs; seek linkage with Actions T4 and T29 as appropriate. | Parties’ national services and research agencies, FLUXNET organizations, NEON, and ICOS, in association with CEOS WGCV, CGMS-GSICS, and GTOS (TCO and TOPC). | Implementation started by 2011, completed by 2014. | Plan for the development and application of standardised protocols for the | 30-100M US$ (40% in non-Annex-I Parties). |
T24
Cat-B | Obtain, archive and make available in situ calibration/validation measurements and collocated albedo products from all space agencies generating such products; promote benchmarking activities to assess the quality and reliability of albedo products. | Space agencies in cooperation with CEOS WGCV. | Full benchmarking/intercomparison by 2012. | Publication of inter-comparison/validation reports. | 1-10M US$ (20% in non-Annex-I Parties). |
T25
Cat-B | Implement globally coordinated and linked data processing to retrieve land surface albedo from a range of sensors on a daily and global basis using both archived and current Earth Observation systems. Who: Space agencies, through the CGMS and WMO Space Programme. | Space agencies, through the CGMS and WMO Space Programme. | Reprocess archived data by 2012, then generate continuously. | Completeness of archive. | 1-10M US$ (Mainly by Annex-I Parties) |
*GCOS-195 Status Categories:
Category A: Action completed, perhaps exceeding reasonable expectations. Very good progress on ongoing tasks.
Category B: Action largely completed according to expectation. Good progress on ongoing tasks.
Category C: Moderate progress overall, although progress may be good for some part of the action.
Category D: Limited progress overall, although progress may be moderate or good for some part of the action.
Category E: Very little or no progress, or deterioration rather than progress.
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| GCOS Products | |
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| CEOS Response | [T24 (T.5)]
2015 Update: Sensor-specific validation efforts continued during 2011-2015. Due to a lack of dedicated funding, the planned activities for intercomparison and validation across albedo products and the publication of fiducial reference data set based on in-situ networks are delayed. The Land Product Validation Subgroup of CEOS WGCV has updated and published validation and intercomparison information at the end of 2014 available on the Land Product Validation web site http://lpvs.gsfc.nasa.gov/. The validation and intercomparison protocol is under development.
[T25 (T.5)]
2015 Update: Two SCOPE-CM projects are ongoing, SCM-02 (Surface albedo LEO) and SCM-03 (Surface albedo GEO) with the aim of evaluating and producing Climate Data Records (CDR) for surface albedo.
a) Surface albedo CDR from Geostationary satellites (SCM-03)
Land surface albedo is a key forcing parameter for the climate system controlling the radiative energy budget. It is the Global Climate Observing System (GCOS) terrestrial Essential Climate Variable (ECV) product T.5 that is described including product requirements in GCOS-154, thus, its monitoring is of primary importance for an understanding of the climate system. Its value changes in space and time, depending on both natural processes (vegetation growth, rain and snowfall and snow melting, wildfires, etc.) and human activities (forestation and deforestation, harvesting crops, anthropogenic fires, etc.). Observations acquired by geostationary satellites have the advantages of offering both a long-term dataset and an angular sampling of the surface as well as providing diurnal sampling of key parameters influencing the retrieval such as cloud cover and aerosol load. The project objective is the generation of a land surface albedo Climate Data Record (CDR) covering the Earth surface seen by geostationary satellites (Polar Regions are not included) for a time window of approximately 30 years. The project aims at a product that includes Level 2 (at the native instrument resolution) and Level 3 (at coarse resolution between 0.25 and 1.0 degree) surface albedo data records to be utilized in climate science and climate services.
Phase 1 (2008-2012)
The SCOPE-CM Phase 1 focused on the establishment of a coordinated network of space agencies and organizations. The main task during this phase is the creation of interagency partnerships and the establishment of the network, for which five pilot projects have been started. During this phase the involved agencies have demonstrated that the current approach is feasible. The involved scientists have all the necessary skills to continue the work including updates to the retrieval system. The team spirit during the unfunded activities of phase 1 was demonstrated by a joint publication in the Bulletin of the American Meteorological Society (Lattanzio et al. 2013). During this phase a first processing of the data archives in EUMETSAT, JMA and NOAA has been performed to check the feasibility of such a federated activity.
Phase 2 (2012-2018)
The SCOPE-CM Implementation Plan (SCOPE-CM 2014) was revisited in 2012 and the Land surface albedo from geostationary satellites (LAGS) project has been accepted in 2014. The first objectives are the quality improvement, in particular in terms of residual cloud contamination removal, and a homogenization of the ancillary input information (calibration and NWP data) among the 3 agencies. The need to tackle these issues was a clear outcome of the first phase. The next Level 2 reprocessing campaign is foreseen for 2016. Following the success of such an activity a near-global Level 3 product will be generated and distributed. The project team is confident that the resulting CDR will contribute to climate studies answering questions such as on monsoon decadal scale variability. It will further contribute to the evaluation of quality of climate model simulations by entering the Obs4MIPs initiative and to direct estimates of global surface energy budget. ... more ...
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