g1sst-class: Class to Store G1SST Satellite/Model Data

In oce: Analysis of Oceanographic Data

Class to Store G1SST Satellite/Model Data

Description

This class stores G1SST model-satellite products.

Details

G1SST is an acronym for global 1-km sea surface temperature, a product that combines satellite data with the model output. It is provided by the JPO ROMS (Regional Ocean Modelling System) modelling group. See the JPL website (reference 1) to learn more about the data, and see the read.g1sst() documentation for an example of downloading and plotting.

It is important not to regard G1SST data in the same category as, say, amsr data, because the two products differ greatly with respect to cloud cover. The satellite used by amsr has the ability to sense water temperature even if there is cloud cover, whereas g1sst fills in cloud gaps with model simulations. It can be helpful to consult reference 1 for a given time, clicking and then unclicking the radio button that turns off the model-based filling of cloud gaps.

Slots

data

As with all oce objects, the data slot for g1sst objects is a list containing the main data for the object.

metadata

As with all oce objects, the metadata slot for g1sst objects is a list containing information about the data or about the object itself.

processingLog

As with all oce objects, the processingLog slot for g1sst 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 g1sst objects (see [[<-,g1sst-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 g1sst 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 [[,g1sst-method operator, as e.g. o[["data"]] and o[["metadata"]], respectively.

The [[,g1sst-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

References

1. JPO OurOcean Portal ⁠https://ourocean.jpl.nasa.gov/SST/⁠ (link worked in 2016 but was seen to fail 2017 Feb 2).

See Also

Other classes holding satellite data: amsr-class, landsat-class, satellite-class

Other things related to g1sst data: [[,g1sst-method, [[<-,g1sst-method, read.g1sst()

oce documentation built on Sept. 11, 2024, 7:09 p.m.