EarthCARE level-2 demonstration products from simulated scenes

Overview

The EarthCARE satellite combines four instruments, a Cloud Profiling Radar (CPR), an Atmospheric Lidar (ATLID), a Multispectral Imager (MSI) and a Broadband Radiometer (BBR), from which many products will be generated on the properties of clouds, aerosols, precipitation and radiation.  The dataset in this repository consists of test products generated from simulated 3D scenes produced by the Canadian Global Environmental Multiscale (GEM) model. This includes both Level 1 (L1) "input" products containing simulated satellite measurements, and Level 2 (L2) "output" products produced by running the various European retrieval algorithms on the inputs.  The dataset has been produced as part of the European Space Agency funded "CARDINAL" project involving numerous European and Canadian scientists, and there are several versions representing the evolution of the algorithms during preparation for the launch of EarthCARE.  The scenes and algorithms are discussed in detail in a Special Issue of the journal Atmospheric Modelling Techniques (AMT), so the overview here is limited to a summary of what is contained in this dataset.

Directory structure

The four main top-level directories inside the zip file are for the three simulated scenes (except for the C-APC directory, described in a separate section below), each of which represent a single 6000-km long EarthCARE granule:

• Halifax: A swath over the Atlantic Ocean from the Caribbean to the Labrador Sea, passing close to Halifax in Nova Scotia
• Baja: A swath passing over the Rocky Mountains and the Baja California peninsula in Mexico
• Hawaii: A swath over the Pacific Ocean passing close to Hawaii
• Halifax_aerosol (added in version 10.10): A modified version of the Halifax scene with clouds removed and modified aerosols, to provided additional testing of the ATLID and MSI retrieval algorithms (note that algorithms involving CPR and BBR have not been run on this scene)

Each of these directories contains three further directories:

• input: simulated level-1 instrument data (note that the data formats, e.g. attributes and variable names, do not exactly match those of real EarthCARE data, although they are close)
• output: level-2 meteorological products generated from the input data (note that updates to the algorithms in future may lead to minor changes to the data formats, so always use the most up-to-date Zenodo release)
• logs: text files logging the progress of the algorithms as they generated the level-2 data

The input and output directories contain subdirectories for each product, and these each contain two files:

• A NetCDF4/HDF5 file with the suffix "h5" containing the retrieved data
• An XML file with the suffix "HDR" containing a description of the variables in the file (reproducing metadata already in the NetCDF4/HDF5 file)

Input products (L1)

The level-1 products are named Y-ZZZ where Y indicates the source of the data (A=ATLID, C=CPR, M=MSI, B=BBR and X=auxiliary) and ZZZ is a shortened version of the product name:

• A-NOM: Nominal ATLID measurements
• C-NOM: Nominal CPR measurements
• M-RGR: Regridded MSI measurements
• B-NOM: Nominal BBR measurements averaged to various scales
• B-SNG: Single-pixel BBR measurements
• X-JSG: Definition of the Joint Standard Grid on to which several of the observations are interpolated
• X-MET: Meteorological data from ECMWF

Single-instrument output products (L2a)

The naming convention is the same as the L1 data products.

• A-AER: ATLID aerosol profiles
• A-ALD: ATLID aerosol layer descriptor
• A-CTH: ATLID cloud top height
• A-EBD: ATLID extinction, backscatter and depolarization
• A-FM: ATLID feature mask
• A-ICE: ATLID ice cloud properties
• A-TC: ATLID target classification
• C-CD: CPR corrected Doppler velocity
• C-CLD: CPR cloud properties
• C-FMR: CPR feature mask and reflectivity
• C-TC: CPR target classification
• M-AOT: MSI aerosol optical thickness
• M-CM: MSI cloud mask
• M-COP: MSI cloud optical and physical properties

Multi-instrument output products (L2b)

The level-2b output products are named YY-ZZZ where YY is 2-4 character code conveying which of the four instruments were used and ZZZ is the shortened version of the product name.

• AC-TC: ATLID-CPR target classification
• AM-ACD: ATLID-MSI aerosol column descriptor
• AM-CTH: ATLID-MSI cloud top height
• BM-RAD: BBR-MSI broadband radiances (unfiltered)
• ACM-3D: ATLID-CPR-MSI constructed 3D scene
• ACM-CAP: ATLID-CPR-MSI synergistic retrieval of cloud, aerosol and precipitation
• ACM-COM: ATLID-CPR-MSI composite of single-instrument cloud and aerosol retrievals
• ACM-RT: ATLID-CPR-MSI radiative fluxes and heating rates computed on the retrievals
• BMA-FLX: BBR-MSI-ATLID broadband fluxes
• ACMB-DF: ATLID-CPR-MSI-BBR difference between radiances and fluxes computed from retrievals (ACM-RT) and measurements (BM-RAD, BMA-FLX)

CPR Antenna Pointing Correction (C-APC) product

From version 10.01 of the dataset, an additional top-level "C-APC" directory contains test data for the CPR Antenna Pointing Correction product, which will be generated via statistical analysis of a larger sample of C-NOM data. The generated information about mis-pointing of the radar antenna will then be used to improve interpretation of subsequent radar Doppler observations. There are two subdirectories:

• GEM_scenes: contains a file used in subsequent radar processing of the three GEM scenes, although in these scenes it has been assumed that there is no mis-pointing to correct, indicated by the file containing missing data and zeros.
• Antenna_mispointing_example: contains input and output files (in further subdirectories) illustrating what the data would look like with mis-pointing present. It was generated by artificially modifying the Doppler veclocities in the original Baja, Halifax and Hawaii scenes, concatenating them to generate a full orbit, and then running the C-APC algorithm to characterize the mis-pointing.

Product definition documents

From version 10.10 of the dataset, an additional top-level directory "Product_definition_documents" is provided containing documents that describe the variables contained in each of the level-2 product files.

Filename format

The data filenames and directories have the following name format:

ECA_EXAA_YYY_ZZZ_LL_OBSERVATION-TIME_GENERATION-TIME_VVVVVV

where:

• "ECA" indicates EarthCARE.
• EXAA indicates the file class: ESA, Latency N/A, Simulator, Baseline N/A.
• YYY is a three-character code indicating the instrumental source of the data. The 1-4 character codes defined in the sections above are converted to 3 character codes as follows: A -> ATL, C -> CPR, M -> MSI, B -> BBR, X -> AUX, AM -> AM_, AC -> AC_, BM -> BM_, ACMB -> ALL.
• ZZZ is a three-character code abbreviating the full name of the product, as defined in the sections above.
• LL represents the level of the data from 1B, 1C, 1D, 2A and 2B.
• OBSERVATION-TIME is a code representing the date and time the observations were taken in the form yyyymmddThhmmssZ. Note that for the present datasets the dates are fictional future dates.
• GENERATION-TIME is a code of the same form representing the time that the processor was run to produce the data product.
• VVVVVV indicates the orbit number and frame letter.

Further information may be obtained from the papers in the special issue of AMT. The description here may be expanded in future.

Contacts: Gerd-Jan van Zadelhoff <gerd-jan.van.zadelhoff@knmi.nl> and Robin Hogan <r.j.hogan@ecmwf.int>