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nowcoast/analysis_ocean_sfc_sst_time (MapServer)

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Service Description:
Last Revised: November 2020

Map Information

This nowCOAST™ time-enabled map service provides a map depicting the latest daily sea surface temperature analyses from both the NOAA/NWS/NCEP operational Near-Sea Surface Temperature (NSST) analysis and the NASA/SPoRT experimental North American Sea Surface Temperature Composite.

The NSST analysis has a 1/12 degree (~9 km) grid resolution and covers the globe including the Great Lakes. SSTs are indicated by different colors at 2 degrees F intervals. NCEP generates the analysis once per day and it is updated on the nowCOAST™ map service around 0400 UTC (11 PM EST). The NSST replaced NCEP's Real-Time Global Sea Surface Temperature (RTGSST) analysis on February 11, 2020.

The experimental SPoRT SST analysis has a 2 km grid resolution and covers the North Atlantic Ocean and the Eastern North Pacific Ocean, the Great Lakes, and occasionally other large lakes. SSTs are displayed by the same color scale used for the NCEP SST analysis. The NASA SPoRT group generates the analysis twice per day and it is updated on the nowCOAST™ map service around 0330 UTC (2230 EST) and 1530 UTC (1030 EST). For more detailed information about layer update frequency and timing, please reference the nowCOAST™ Dataset Update Schedule.

Background Information

The NWS/NCEP daily NSST (1/12 deg) analysis is generated by the interpolation of NCEP's Global Data Assimilation System (GDAS) NSST foundation water temperature analysis. NSST models oceanic vertical water temperature structure near the surface due to diurnal warming and sub-layer cooling physical processes. The NSST analysis replaced NCEP's NOAA/NWS/NCEP operational Real-Time Global SST Analysis System, commonly referred to as RTG_SST_HR, which was retired from the NCEP Production Suite.

The NASA Short-Term Prediction Research and Transition (SPoRT) group generates a semi-operational SST composite for the Northern Hemisphere (NA) at a 2 km spatial resolution. The SPoRT SST Composite is a blend of 1) NASA high-resolution Moderate Resolution Imaging Spectroradiometer (MODIS), 2) Visible Infrared Imaging Radiometer Suite (VIIRS), 3) the NOAA/NESDIS daily global Blended GOES/POES Sea Surface Temperature (SST) Analysis, and 4) United Kingdom Met Office (UKMO) daily global Operational Sea Surface Temperature and Ice Analysis (OSTIA). However, for inland lakes such as the Great Lakes, the NESDIS GOES/POES analysis is not available. MODAS and VIIRS data have spatial resolutions of 1 km and 750 m, respectively while the NESDIS and OSTIA analyses have resolutions of approximately 5 and 6 km, respectively. VIIRS is flown on the Suomi National Polar-orbiting Partnership (Suomi NPP) and NOAA-20 polar-orbiting satellites, while MODIS is flown on NASA's Terra and Aqua polar-orbiting satellites.

The SPoRT compositing algorithm uses the most recent seven-day collection of MODIS level-2B data and the most recent daily NESDIS GOES/POES SST Analysis and OSTIA products. While the MODIS and VIIRS data seven-day collections are processed in near real-time, the NESDIS and OSTIA product are from the previous day. Two types of weighting are used in the compositing processed. One weight is for the data latency and the other for the product type (i.e. resolution). The MODIS and VIIRS data are given the most weight due to their higher spatial resolution and goal for the composite to be an observation-driven product. All available confidence flags and bias information are incorporated in the compositing process. The SPoRT SST Composite is generated twice daily and valid for the periods 0000-1159 UTC and 1200-2359 UTC.

Time Information

This map service is time-enabled, meaning that each individual layer contains time-varying data and can be utilized by clients capable of making map requests that include a time component.

In addition to ArcGIS Server REST access, time-enabled OGC WMS 1.3.0 access is also provided by this service.

This particular service can be queried with or without the use of a time component. If the time parameter is specified in a request, the data or imagery most relevant to the provided time value, if any, will be returned. If the time parameter is not specified in a request, the latest data or imagery valid for the present system time will be returned to the client. If the time parameter is not specified and no data or imagery is available for the present time, no data will be returned.

This service is configured with time coverage support, meaning that the service will always return the most relevant available data, if any, to the specified time value. For example, if the service contains data valid today at 12:00 and 12:10 UTC, but a map request specifies a time value of today at 12:07 UTC, the data valid at 12:10 UTC will be returned to the user. This behavior allows more flexibility for users, especially when displaying multiple time-enabled layers together despite slight differences in temporal resolution or update frequency.

When interacting with this time-enabled service, only a single instantaneous time value should be specified in each request. If instead a time range is specified in a request (i.e. separate start time and end time values are given), the data returned may be different than what was intended.

Care must be taken to ensure the time value specified in each request falls within the current time coverage of the service. Because this service is frequently updated as new data becomes available, the user must periodically determine the service's time extent. However, due to software limitations, the time extent of the service and map layers as advertised by ArcGIS Server does not always provide the most up-to-date start and end times of available data. Instead, users have three options for determining the latest time extent of the service:

  1. Issue a returnUpdates=true request (ArcGIS REST protocol only) for an individual layer or for the service itself, which will return the current start and end times of available data, in epoch time format (milliseconds since 00:00 January 1, 1970). To see an example, click on the "Return Updates" link at the bottom of the REST Service page under "Supported Operations". Refer to the ArcGIS REST API Map Service Documentation for more information.
  2. Issue an Identify (ArcGIS REST) or GetFeatureInfo (WMS) request against the proper layer corresponding with the target dataset. For raster data, this would be the "Image Footprints with Time Attributes" layer in the same group as the target "Image" layer being displayed. For vector (point, line, or polygon) data, the target layer can be queried directly. In either case, the attributes returned for the matching raster(s) or vector feature(s) will include the following:
    • validtime: Valid timestamp.
    • starttime: Display start time.
    • endtime: Display end time.
    • reftime: Reference time (sometimes referred to as issuance time, cycle time, or initialization time).
    • projmins: Number of minutes from reference time to valid time.
    • desigreftime: Designated reference time; used as a common reference time for all items when individual reference times do not match.
    • desigprojmins: Number of minutes from designated reference time to valid time.
  3. Query the nowCOAST™ LayerInfo web service, which has been created to provide additional information about each data layer in a service, including a list of all available "time stops" (i.e. "valid times"), individual timestamps, or the valid time of a layer's latest available data (i.e. "Product Time"). For more information about the LayerInfo web service, including examples of various types of requests, refer to the nowCOAST™ LayerInfo Help Documentation


Map Name: NOAA NWS NCEP NSST and NASA SPoRT Sea Surface Temperature Analyses (Time Enabled)


All Layers and Tables

Dynamic Legend

Dynamic All Layers

Layers: Description:


Spatial Reference: 102100  (3857)

Single Fused Map Cache: false

Initial Extent: Full Extent: Time Info: Units: esriMeters


Document Info: Supports Dynamic Layers: true

MaxRecordCount: 1000

MaxImageHeight: 4096

MaxImageWidth: 4096

Supported Query Formats: JSON, AMF, geoJSON

Min Scale: 0

Max Scale: 0

Supports Datum Transformation: true

Child Resources:   Info   Dynamic Layer

Supported Operations:   Export Map   Identify   Find   Return Updates