R: Class to Store AMSR-2 Satellite Data

amsr-class {oce}

R Documentation

Class to Store AMSR-2 Satellite Data

Description

This class stores data from the AMSR-2 satellite.

Details

The Advanced Microwave Scanning Radiometer (AMSR-2) is in current operation on the Japan Aerospace Exploration Agency (JAXA) GCOM-W1 space craft, launched in May 2012. Data are processed by Remote Sensing Systems. The satellite completes an ascending and descending pass during local daytime and nighttime hours respectively. Each daily file contains 7 daytime and 7 nighttime maps of variables named as follows within the data slot of amsr objects: timeDay, SSTDay, LFwindDay (wind at 10m sensed in the 10.7GHz band), MFwindDay (wind at 10m sensed at 18.7GHz), vaporDay, cloudDay, and rainDay, along with similarly-named items that end in Night. See reference 1 for additional information on the instrument, how to cite the data source in a paper, etc.

The bands are stored in raw() form, to save storage. The accessor function [[,amsr-method can provide these values in raw form or in physical units; plot,amsr-method(), and summary,amsr-method() work with physical units.

Slots

data: As with all oce objects, the data slot for amsr objects is a list containing the main data for the object.
metadata: As with all oce objects, the metadata slot for amsr objects is a list containing information about the data or about the object itself. Examples that are of common interest include longitude and latitude, which define the grid.
processingLog: As with all oce objects, the processingLog slot for amsr objects is a list with entries describing the creation and evolution of the object. The contents are updated by various oce functions to keep a record of processing steps. Object summaries and processingLogShow() both display the log.

Modifying slot contents

Although the [[<- operator may permit modification of the contents of amsr objects (see [[<-,amsr-method), it is better to use oceSetData() and oceSetMetadata(), because those functions save an entry in the processingLog that describes the change.

Retrieving slot contents

The full contents of the data and metadata slots of a amsr object may be retrieved in the standard R way using slot(). For example slot(o,"data") returns the data slot of an object named o, and similarly slot(o,"metadata") returns the metadata slot.

The slots may also be obtained with the [[,amsr-method operator, as e.g. o[["data"]] and o[["metadata"]], respectively.

The [[,amsr-method operator can also be used to retrieve items from within the data and metadata slots. For example, o[["temperature"]] can be used to retrieve temperature from an object containing that quantity. The rule is that a named quantity is sought first within the object's metadata slot, with the data slot being checked only if metadata does not contain the item. This [[ method can also be used to get certain derived quantities, if the object contains sufficient information to calculate them. For example, an object that holds (practical) salinity, temperature and pressure, along with longitude and latitude, has sufficient information to compute Absolute Salinity, and so o[["SA"]] will yield the calculated Absolute Salinity.

It is also possible to find items more directly, using oceGetData() and oceGetMetadata(), but neither of these functions can retrieve derived items.

Author(s)

Dan Kelley and Chantelle Layton

References

Information on the satellite, how to cite the data, etc. is provided at ⁠http://www.remss.com/missions/amsr/⁠.
A simple interface for viewing and downloading data is at ⁠http://images.remss.com/amsr/amsr2_data_daily.html⁠.