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CM SAF provides new global near-realtime data for climate monitoring
The new Interim Climate Data Record (ICDR) AVHRR has been released by CM SAF in March 2021. It starts in 2019/01 and is being continuously extended to five days behind present. The ICDR is based on observations from the AVHRR sensors onboard the polar orbiting NOAA and METOP satellites. It deploys the same algorithms as the Thematic Climate Data Record (TCDR) CLARA-A2.1 (CM SAF cLoud, Albedo and surface Radiation dataset from AVHRR data - Edition 2.1) and thus consistently extends its time series of cloud properties, surface albedo and surface radiation parameters. Since CLARA-A2.1 starts in 1982, the combined time series already covers more than 39 years and is growing continuously. It also includes the new reference period 1991-2020 for WMO-conformant climatological standard normal. The products are available with global coverage.
TCDRs as well as ICDRs undergo a thorough validation and review process before publication. While TCDRs are based on inter-calibrated satellite level-1 products, the ICDR uses satellite products available in near real-time. Beside the initial validation before publication, the ICDRs are validated retrospectively in so-called Annual Quality Assessment Reports to ensure the quality of the products during the continuous processing. The ICDR is generated with the same algorithms that are used in the production of the TCDR, hence, both data records are still highly consistent. Together, they can serve climatological applications with strong timeliness requirements like monitoring of anomalies. Furthermore, the combined records of TCDR and ICDR are well suited for other climatological applications, as long as an extended version of the underlying TCDR is not available.
global map of the cloud fraction climatology for 1982-2020 Source: CM SAF
global map of the surface albedo climatology for 1982-2020 Source: CM SAF
global map of the downwelling shortwave radiation climatology for 1982-2020 Source: CM SAF
Figure 1: Climatological mean fields of CLARA-A2.1 and ICDR AVHRR (based on CLARA-A2 methods) for cloud fractional coverage, surface albedo and surface incoming shortwave radiation for the time period 1982 – 2020 (from top to bottom).
The ICDR AVHRR features the range of products from the CLARA-A2.1 data record listed below. All parameters are available on a global 0.25°x0.25° latitude/longitude grid. For cloud fractional coverage, cloud top height and surface albedo, the products are additionally provided in two equal area grids with a resolution of 25 km x 25 km covering the Polar Regions. The cloud parameters and the surface incoming shortwave radiation are available as monthly and daily averages, while surface albedo is presented as monthly and pentad (5 day) averages.
These ICDR AVHRR products can be ordered via the CM SAF Web User Interface.
More information on the ICDR AVHRR including direct links to the data download as well as links to the documentation (Product User Manuals, Validation Reports, Algorithm Theoretical Basis Documents) are available from the ICDR AVHRR landing page.
List of products in ICDR AVHRR
| Product Name | Product Acronym |
|---|---|
| Fractional Cloud Cover | CFC |
| Cloud Top Height, Temperature, Pressure | CTO |
| Cloud Phase | CPH |
| Liquid Water Path | LPW |
| Ice Water Path | IWP |
| Surface Albedo | SAL |
| Surface Incoming Shortwave Radiation | SIS |
| Time period | 2019/01 – present |
|---|---|
| Temporal resolution | daily mean, pentad mean, monthly mean (depending on product) |
| Spatial coverage | global on a regular latitude/longitude grid (polar areas: equal area) |
| Spatial resolution | 0.25° x 0.25° globally and 25 km x 25 km for polar areas |
| Data Format | NetCDF 4, Climate and Forecast (CF) Metadata Convention v1.6 |
Documentation
Karlsson, K.-G., Anttila, K., Trentmann, J., Stengel, M., Meirink, J. F., Devasthale, A., Hanschmann, T., Kothe, S., Jääskeläinen, E., Sedlar, J., Benas, N., van Zadelhoff, G.-J., Schlundt, C., Stein, D., Finkensieper, S., Håkansson, N., and Hollmann, R.: CLARA-A2: The second edition of the CM SAF cloud and radiation data record from 34 years of global AVHRR data, 17, 5809–5828, https://doi.org/10.5194/acp-17-5809-2017, 2017.
Karlsson, Karl-Göran; Anttila, Kati; Trentmann, Jörg; Stengel, Martin; Solodovnik, Irina; Meirink, Jan Fokke; Devasthale, Abhay; Kothe, Steffen; Jääskeläinen, Emmihenna; Sedlar, Joseph; Benas, Nikos; van Zadelhoff, Gerd-Jan; Stein, Diana; Finkensieper, Stephan; Håkansson, Nina; Hollmann, Rainer; Kaiser, Johannes; Werscheck, Martin (2020): CLARA-A2.1: CM SAF cLoud, Albedo and surface RAdiation dataset from AVHRR data - Edition 2.1, Satellite Application Facility on Climate Monitoring, https://doi.org/10.5676/EUM_SAF_CM/CLARA_AVHRR/V002_01.
JK / April2021