The CM SAF FCDR of Microwave Imager Radiances comprises inter-calibrated brightness temperatures (BTRs) from the SMMR, SSM/I and SSMIS radiometers. The 4th edition covers the time period from October 1978 to December 2020 including all available data from the SMMR radiometer aboard Nimbus–7, the SSM/I radiometers aboard F08, F10, F11, F13, F14, and F15 and the SSMIS radiometers aboard F16, F17, and F18.

This data record has now been extended by two more years of SSMIS (F16, F17, F18) data. This prolongs the end of the covered time period to December 2022.

The data record can be ordered via the Web User Interface. More information on the data record and accompanying documentation is available from the DOI page: DOI:10.5676/EUM_SAF_CM/FCDR_MWI/V004.

The AVHRR sensor onboard the NOAA-15 satellite has been in service for more than 25 years and its data has been used in all CLARA CDR editions. It is also still used in the ICDR products for CLARA-A3. However, recently problems with the sensor's scan motor have become more serious and it has therefore been decided to discontinue using the data from 10 November 2023 onwards. Especially since end of August 2023 scan motor problems became more obvious in the sensor data. Products have been affected in various ways and most clearly by loss of data in segments and stripes, sometimes being directly visible in some products. More problematic is that also navigation information might be affected leading to erroneous projection of data. To prevent from further damages to products, it was decided to stop using NOAA-15 AVHRR data in all CLARA-A3 ICDR products.

Besides the scan motor issue of NOAA-15, increased amounts of data losses for NOAA-15 NOAA-18 and NOAA-19 have been observed since late July 2023 with largest data gaps from mid-September to end of October 2023. This is caused by the transition of these satellites to the POES Extended Life Ground System which operates on a best-effort basis (see also https://www.ospo.noaa.gov/data/messages/2023/11/MSG_20231101_0100.html). Unfortunately, the period is overlapping with the above mentioned problem of NOAA-15. We thus advice to keep these issues in mind when using ICDR data from CLARA-A3 of the described period.

The loss of observations from NOAA-15 is foreseen to be covered up by introducing observations from the Metop-C satellite which so far has not been used in ICDR production due to previous uncertainties in the applied calibration method. With an updated calibration, Metop-C can now be used and will to a large extend replace observations from NOAA-15, despite a slightly later observation time. The (re-)introduction of Metop-C observations will be communicated in a separate service message as soon as a date for the introduction is set.

Status

see service message No. 159

In the previous years, CM SAF has been releasing a number of climate data records (CDRs) and interim climate data records (ICDRs). For several parameters, more than one edition of the respective CDR and ICDR has been published with the most recent version having improved quality, better coverage and higher accuracy compared to the previous release(s) of the respective parameter. CM SAF strongly recommends using only the most recent release of the CDRs and ICDRs.

In order to help our users to identify the most recent CDR and ICDR data, we are in the process of changing the access to the different data records in our system. Only the most recent edition of the products will be available for ordering via our CM SAF Web User Interface. Earlier releases of the respective products will only be made available on request. In case users need access to these earlier product versions, please contact the CM SAF User Help Desk via contact.cmsaf@dwd.de.

Information on all released products will remain available on the CM SAF webpage (e.g., change log, documentation. For all CDR versions the respective DOI page includes information about the ordering of the respective products. A list of all CDRs and their DOIs is available on the CM SAF webpage including information on the access to the products.

The changes will be implemented in the upcoming weeks and we will update this service message once the changes are completed.

We are sorry to inform you that due to an inconsistent treatment of missing values, 106 grid boxes of the CLARA-A3 surface irradiance (SIS) daily mean data in the period 1979 – 2022 contain (incorrect) negative values. Our analysis has shown that only grid boxes in the area between 66°N and 71°N in the Northern winter months (November – January) have been affected.
As a consequence of the incorrect daily SIS data, the corresponding grid boxes of the monthly data of surface irradiance (SIS), surface net solar radiation (SNS), and the surface radiation budget (SRB) are also affected (These parameters use the daily SIS data as input.).
Users are advised to disregard the data of the affected grid boxes (in the daily and monthly means) and set their values to missing data. Note, that an impact of the inconsistent treatment of the missing values during the data generation on additional grid boxes of the CLARA-A3 solar surface radiation data record cannot be excluded.

The list of affected grid boxes is attached (dat, 5KB, Not barrier-free file.) to this service message and has the following format:
Date (given as YYYY-MM-DD), Date (in days since 1970-01-01), index of longitude, index of latitude, longitude (in degrees), latitude (in degrees), SIS value (in Wm-2).
The counting of the provided indices for latitude and longitude starts at 1.

Tables 1 and 2 show the number of affected grid boxes for each day and each month, respectively.

Table 1: Number of affected grid boxes per day

Table 2: Number of affected grid boxes per month

Note that the number of grid boxes per time step (i.e., day or month) is larger than 1 million (CLARA-A3 spatial grid: 1440 x 720). Thus, the overall impact of this feature on the data quality is negligible. Due to the insignificant overall impact no update of the data is planned for CLARA-A3.
The list of affected grid boxes will be regularly extended.

The CLARA-A3 cloud and surface albedo (SAL) polar products are defined on different grids. Cloud polar products are defined on 25km x 25km EASE-Grid, SAL polar products are defined on 25km x 25km EASE-Grid 2-0. Therefore, products are not comparable on a pixel-by-pixel basis. Individual auxiliary files are available for cloud and SAL products.

Auxiliary files for cloud polar products:
clara3_level3_aux_data_polar_nh.nc / clara3_level3_aux_data_polar_sh.nc

Auxiliary files for SAL polar products:
clara3_sal_level3_aux_data_polar_nh.nc / clara3_sal_level3_aux_data_polar_sh.nc

The third edition of the Surface Solar Radiation Data Set - Heliosat (SARAH-3) is a satellite-based climate data record of the solar surface irradiance, the surface direct irradiance (direct horizontal and direct normalized), the sunshine duration, the photosynthetically active radiation, daylight, and the effective cloud albedo derived from satellite-observations of the visible channels of the MVIRI and the SEVIRI instruments onboard the geostationary Meteosat satellites. SARAH-3 covers the time period 1983/01/01 until 2020/12/31 as climate data record (CDR) and is operationally extended as interim climate data record (ICDR) to the present with a latency of 5 days; the data cover the region ±65° longitude and ±65° latitude. The products are available as monthly and daily means, and as 30-min instantaneous data (sunshine duration is available as monthly and daily sum) on a regular latitude/longitude grid with a spatial resolution of 0.05° x 0.05° degrees. The data record is complemented with a comprehensive documentation of the algorithms used and the generation of the data record. Validation report and user guidance are available as well.

The data record can be ordered via the Web User Interface. More information on the data record and accompanying documentation is available from the DOI page: 10.5676/EUM_SAF_CM/SARAH/V003

The CLARA-A3 record provides cloud properties and radiation parameters derived from the AVHRR sensor onboard polar orbiting NOAA and METOP satellites. CLARA-A3 is the latest edition of CLARA with previous editions documented in Karlsson et al. (2013) and Karlsson et al. (2017). CLARA-A3 covers the time period 1979/01/01 until 2020/12/31 as climate data record (CDR), but is operationally extended as interim climate data record (ICDR) to the present with a latency of 10 days.
The AVHRR measurement input to the CLARA-A3 retrieval algorithms is the EUMETSAT PyGAC AVHRR Fundamental Data Record (FDR) Release 1 (DOI:10.15770/EUM_SEC_CLM_0060). CLARA-A3 features a range of cloud products: cloud mask, cloud top temperature/pressure/height, cloud thermodynamic phase, and (for liquid and ice clouds separately) cloud optical thickness, particle effective radius and cloud water path. Additionally, cloud droplet number concentration and cloud geometrical thickness are provided for liquid clouds. Furthermore, a range of radiation products are included in CLARA-A3: surface black-sky, white-sky and blue-sky albedo; surface downwelling short- and longwave radiation as well as surface net radiation; top-of-atmosphere (TOA) upwelling short- and longwave radiation. Cloud products are available as monthly and daily averages and histograms, as well as daily resampled global products (Level 2b) for individual satellites. Surface albedo is presented as monthly and pentad (5 day) averages. Surface and TOA radiation products are provided as daily and monthly averages. All averages are available on a 0.25° x 0.25° global grid. Surface albedo and selected cloud products are also provided on two equal area grids with a resolution of 25 km x 25 km covering the polar regions. Daily resampled cloud products (level 2b) are provided in a global grid with a resolution of 0.05°x0.05°. CLARA-A3 features a comprehensive set of documentation including User Manuals, Validation Reports and Algorithms Theoretical Baseline Documents.

The data record can be ordered via the Web User Interface. More information on the data record and accompanying documentation is available from the DOI page: 10.5676/EUM_SAF_CM/CLARA_AVHRR/V003

Status

see service message No. 159
see service message No. 154 and No. 155

As announced earlier (see Service Message 143), a new edition of the global cloud, surface radiation and top of atmosphere radiation climate data record (CDR) from AVHRR (CLARA A3) and its corresponding Interim Climate Data Record (ICDR) will soon become available. The release of the CLARA-A3 CDR and ICDR is currently planned for early Q2/2023. With the release of this new edition, we will phase out the processing of the currently provided ICDR AVHRR based on CLARA-A2 algorithms. All users are invited to check their applications using the available test data (see also Service Message 143 and the here (PDF, 272KB, Barrier-free file) for more information on the test files).

CLARA-A3 is based on intercalibrated AVHRR measurements provided as a Fundamental Data Record (FDR) by EUMETSAT for the CDR period, which is operationally extended by CM SAF as basis for the ICDR. New algorithm developments now allow using data from the first generation of the AVHRR-instrument, which significantly improves the temporal coverage and data density. The CLARA-A3 CDR covers the time period 1979-2020 and will be extended as an ICDR from January 2021 onwards with a latency of about 10 days.

Additional key features of CLARA-A3 include:

• General algorithm development improving the quality across all CLARA-A3 products.
• Extension of the product portfolio including for example (a) introduction of upwelling top of atmosphere shortwave and longwave radiation as new products, (b) adding white and blue-sky surface albedo and (c) adding liquid cloud droplet number concentration and liquid cloud geometrical thickness as additional data layers.
• More uncertainty information is added to both level2 and level3 cloud products.
• Better treatment of snow and ice surfaces for the surface radiation products.

Important to note, that while the CLARA-A2 ICDR was available under the term ‘ICDR AVHRR based on CLARA-A2 methods’, the new CDR and corresponding ICDR are both referred to as product family 'CLARA-A3'.

With the official release of CLARA-A3 more information will be issued by CM SAF.

Status

see service message No. 152

The global total column water vapour (TCWV) data record combines microwave and near-infrared imager based TCWV over the ice-free ocean as well as over land, coastal ocean and sea-ice, respectively. The data record relies on microwave observations from SSM/I, SSMIS, AMSR-E and TMI, partly based on a fundamental climate data record (Fennig et al., 2020; Fennig et al., 2017) and on near-infrared observations from MERIS (3rd reprocessing), MODIS-Terra (collection 6.1) and OLCI (1st reprocessing). Details of the retrieval are described in Andersson et al. (2010) and ATBD HOAPS for the microwave imagers as well as in Lindstrot et al. (2012), Diedrich et al. (2015) and ABTD NIR Level 2 for the near-infrared imagers. The water vapour of the atmosphere is vertically integrated over the full column and given in units of kg/m². The microwave and near-infrared data streams are processed independently and combined afterwards by not changing the individual TCWV values and their uncertainties. The combined data record has a spatial resolution of 0.5°x0.5° and 0.05°x0.05°, with the near-infrared based data being averaged and the microwave-based data being oversampled to match the lower and higher spatial resolution, respectively. The product is available as daily and monthly means and covers the period July 2002 – December 2017.

The data record can be ordered via the Web User Interface. More information on the data record and accompanying documentation is available from the DOI page: 10.5676/EUM_SAF_CM/COMBI/V001

As announced earlier (see Service Message 143), a new edition of the regional radiation data record based on MVIRI and SEVIRI and its corresponding interim climate data record (ICDR) will soon become available. The release of the SARAH-3 CDR and ICDR is currently planned for early Q2/2023. With the release of this new edition, we will phase out the processing of the currently provided ICDR, which is based on the SARAH-2 algorithms. Users should already now check their applications using the test data provided earlier (see Service Message 143 and the pdf file for more information on the test files).

The SARAH-3 climate data record includes important scientific improvements and small, but relevant, technical changes compared to the previous edition of the SARAH data record. All currently available parameters from the SARAH-2 ICDR data records (SIS, SDU, SID, DNI) will also be available for SARAH-3, in addition also ICDR data for CAL, PAR and DAL will be provided.

The most important technical change in SARAH-3 compared to SARAH-2 is a shift in the definition of the spatial grid by half a grid box to harmonize the spatial grids between all CM SAF data records based on geostationary data (e.g., the CLAAS data record). Of course, the correct grid information is provided in each data file from the SARAH-3 climate data record and we strongly recommend to use this information in any data processing of the SARAH-3 data.

Scientifically, the most important changes are the improved consideration of snow-covered surfaces in the satellite retrieval, which results in higher surface irradiance over snow-covered surfaces in particular under clear-sky conditions, and the use of new data for the surface albedo and the atmospheric water vapour used in the simulation of the clear-sky surface radiation. These changes imply that for climatological assessments, e.g., the calculation of anomalies, the SARAH-3 CDR data needs to be used as reference for the SARAH-3 ICDR data. Combining SARAH-2 CDR data with SARAH-3 ICDR (or vice versa) will result in the estimation of incorrect and unrealistic anomalies/changes.

Status

see service message No. 153

As announced earlier, the CLAAS-2 based ICDR products will be discontinued after some time of parallel dissemination with the next release of the data record. The processing of the CLAAS-2-based CFC and CTO products from SEVIRI will be stopped at the end of February 2023. Previously processed data will remain available via the Web User Interface.
Users should change their applications to the newest edition of the data, CLAAS-3, which is available since early December 2022 (see Service Message 146).
The parallel dissemination of the two ICDR products via EUMETCast will also be stopped at that time with the monthly mean cloud fraction of February 2023 being the last product of the CLAAS-2 based version to be disseminated via EUMETCast.