Glossary ======== .. glossary:: Auxiliary Data Any data that is input to the geophysical retrieval or gridding that is not radar altimeter sensor data (see :term:`Source Data`). Auxiliary data sets can be dynamic (e.g. daily) or static fields. The data may be stored in external files or computed form a parametrization. Examples are sea ice concentration or type products, land/ocean or regions masks, data on snow on sea ice or mean sea surface products. The overview of supported auxiliary data sets is available in the :ref:`Auxiliary_Datasets` section. Auxiliary Dataset ID A unique identifier for an auxiliary dataset in the form of ``:`` required for specifying and referencing auxiliary datasets in pysiral processors. (See :ref:`Auxiliary_Datasets`) C3S Copernicus Climate Change Service. A program that produces long-term climate and interim data records CCI ESA Climate Change Initiative. A program that produces long-term climate data records (term: `CDR`). CDR Climate Data Record. A data record that provides a long-term, consistent, and quality controlled representation of a specific climate variable. FYI First year sea ice. This term is used to describe sea ice that has formed during the current freeze-up season and has not yet survived a summer melt season. Hemisphere The hemisphere of the Earth, either northern or southern. In pysiral, the hemisphere refers to the Northern and Southern Polar Oceans. Level-1 Pre-Processor Dedicated processing step in pysiral that ingests source data and creates orbit segments over the polar oceans with additional pre-computed parameters in a unified file format for all supported radar altimeter missions. Level-2 Processor Dedicated processing step that performs the geophysical retrieval based on the output of the :term:`Level-1 Pre-Processor`. The coverage of the output is identical to the input data. Level-2 Pre-Processor Dedicated processing step that ingests output from the :term:`Level-2 Processor` and filters and aggregates data and writes daily summary files with the same resolution of the Level-2 data. Level-3 Processor Aggregates the output of the :term:`Level-2 Processor` on a spatio-temporal grid. Also allows to compute statistics and additional parameters. Mission A satellite mission that may consist of one or more satellite platforms. For example, Sentinel-3A and Sentinel-3B are part of the Sentinel-3 mission. iCDR Interim Climate Data Record. A data record that that is a temporal extensions of an :term:`CDR` and is used to provide data until the next CDR is available. Platform A specific (satellite) platform. In pysiral, each platform is referenced by a unique platform identifier, which is by default the lower case name ([a-z0-9]) e.g. ``cryosat2`` or ``envisat``. Processing Item A class that can be called during a processing run for a specific processing level (Level-2 processor). Examples are computing variables, statistics or filtering data. The class must be compliant with the conventions of a processing item for the specific processor. These requirements are generally: 1. The class must have a unique name (typically starts with target processing level) 2. The class receives configuration keywords during initialization. 3. The class must be a subclass of a processing item class (sub-classing registers the processing item class) 4. The class must have a required method that receives the data container, which is then modified in-place It is advisable to implement processing items with a dedicated configuration class and store it in the module ``pysiral..alg``, but any location is technically possible. Processing items are added in processing configuration files to the workflow. The specification includes the class name, optionally the stage in the workflow and any options if required. Processing Level Data processing levels describe the state of data processing from lower (close to the actual sensor data) to higher levels (geophysical retrievals). +---------+-----------------------------------------------+ | Level | Description | +=========+===============================================+ | ``L0`` | Sensor raw data (not supported by pysiral) | +---------+-----------------------------------------------+ | ``L1B`` | Calibrated sensor data. Typical processing | | | level for :term:`Source Data` | +---------+-----------------------------------------------+ | ``L1P`` | Pre-processed sensor data created by the | | | :term:`Level-1 Pre-Processor` | +---------+-----------------------------------------------+ | ``L2`` | Geophysical data at the same coverage and | | | resolutions of l1p data. | | | | | | Output of the :term:`Level-2 Processor` | +---------+-----------------------------------------------+ | ``L2i`` | Geophysical data at the same coverage and | | | resolutions of l1p data. | | | | | | Same as ``L2``, but also contains variables | | | from the ``L1P`` input data. | | | | | | Output of the :term:`Level-2 Processor` | +---------+-----------------------------------------------+ | ``L2p`` | Aggregated and filtered l2i data, for example | | | daily summary files only over sea ice | | | | | | Output of the :term:`Level-2 Pre-Processor` | +---------+-----------------------------------------------+ Product Line An identifier of products and part of the data id of processing levels 2 or higher. The string is usually a short name of the project or institute funding or implementing the data production (Examples: ``cci`` for sea ice thickness climate data records of the ESA Climate Change Initiative). Record type The record type defines the type of data record. In pysiral, the record type can be a :term:`Timeliness` code, but also ``cdr`` (climate data record) of ``icdr`` (interim climate data record). Stage of Development Sea ice classification usually in operational Ice Charts with distinct classes. Sea Ice Concentration The fraction of sea ice in a given area. It is usually expressed as a percentage (0-100%) or as a fraction (0-1). Sea Ice Type The classification of sea ice into different types based on the stage of development of sea ice. In pysiral, sea ice type is defined as the fraction of multi-year sea ice within in a defined area. Sensor The name of the radar altimeter sensor. In pysiral, each sensor is referenced by a unique platform identifier, which is by default the lower case name e.g. ``siral`` for ``cryosat2`` or ``ra-2`` for ``envisat`` . Source Data The term source data refers to calibrated radar altimeter data (waveforms) annotated with a land/ocean mask. geophysical range corrections for path delays in the atmosphere and ionosphere as well as information from tide models. Timeliness Defines the delay a data record is produced. Data from a specific platform/sensor is often delivered with more than one timeliness, and each of these products is its own :term:`Source Data` set. Datasets from satellites that are no longer operational are classified as reprocessed. The table below gives an overview of frequently used timeliness codes and their typical delay. The actual delay of indiviudal source data products may differ from the typical delay. +---------+---------------------+---------------+---------+ | Code | Meaning | Typical Delay | Alias | +=========+=====================+===============+=========+ | ``nrt`` | Near Real-Time | < 2 days | ``stc`` | +---------+---------------------+---------------+---------+ | ``stc`` | Short Time Critical | < 2 day | ``nrt`` | +---------+---------------------+---------------+---------+ | ``rep`` | Reprocessed | 1 month | ``ntc`` | +---------+---------------------+---------------+---------+ | ``ntc`` | Non Time Critical | 1 month | ``rep`` | +---------+---------------------+---------------+---------+