Managing Sea Surface Temperature (SST) Time-Series from Long-Term or Classic Climatologies:
US National Oceanographic Data Center (NODC) Live Access Server (LAS)
In this exercise you'll learn how to find and inspect the massive data
resources available through a relatively new LAS published by the US
NODC. The NODC
is the final depository for a number of satellite imagery products from
other programs, and they have boldly taken on the job of organizing huge
amounts of data into an easily usable LAS. In addition
to raster products described at
Importing Satellite SST and Sea Ice Climatologies into Marine GIS: NODC
LAS, the time-series functions of the LAS can be invoked with
any appropriate dataset. Time-series plots from the latest version
of LAS may include these options, depending on the types of
"Long-term" global analysis
rasters covering specific time periods (e.g. weeks, months) over periods
of years, for example daily SST for the 3rd week in July, 2001, or all
daily SSTs from 1983-2012; can be made from most LAS raster datasets;
"Classic" climatologies (in
the NODCs own terminology) which are daily, weekly or monthly averages
of all data, for example the average of all July SSTs in the entire
database; can only be visualized from LAS datasets that are already
Using this LAS or any of
the many LAS installations available on the net, you can revisit
global conditions for specific times in the past (various intervals; sometimes very
distant), or (for sites
with "classic" climatologies) you can see the usual conditions
(averaged over many years) for particular days, weeks, months or seasons . [ A limited list of LAS
sites is linked just below.]
Preliminary Reading (in
OceanTeacher, unless otherwise indicated):
|1. Open the NODC LAS and take
some time to explore the interface.
2. The author has explored
the main menu items, and offers the following summary. Items that will
or have been covered in MDL exercises are indicated in yellow.
Pathfinder SST Climatology at 9 km
- Global rasters of sea temperature- and ice-related parameters;
1 grid for each of the 366 year-days (1962-2008 data)
CoRTAD - Tiled rasters from the Coral Reef
Temperature Anomaly Database (1981-2010); various parameters for
Experimental Datasets, Under Testing - Not
explored yet; some data apparently not yet loaded
GCOS - Global Climate Observing System datasets;
numerous global SST rasters at 5-deg and 1-deg resolution, for 1981 to
2007 (roughly); "pilot study" of reconstructed global SST rasters for
many other periods
GHRSST Aggregation - Group for High
Resolution SST; L2 through L4 SST global analysis grids for 1981-2011 or
later in some cases; includes nearly all of the Group's archived
Jason-2 Granule Statistics-Per Pass - Not
Gridded Cycle Mean-Per Pass
- Global rasters of altimeter
data (winds, waves, sea height) for 2008-2013; an "operational" product
is current to -3 weeks!
NODE - Regional raster products related to NOAA's
studies of impacts on coral reefs from acidification; includes a few
related global products also available elsewhere; a single tide dataset
for Port Aransas, TX is included (!).
5.2 RI Statistics -
Multi-year (1981-2012) daily global grids of temperature-, ice-, and
wind-related parameters; daily regionally-averaged time-series of
temperature-, ice-, and wind-related parameters
Regional Climatologies - S and T climatology
grids for the Arctic Ocean and Greenland-Iceland-Norwegian Sea
Version 5.0/5.1 AVHRR Pathfinder Sea Surface
Temperature - Global rasters of sea temperature- and ice-related
parameters for 1962-2008; various time periods, quality flags, and
Version 5.2 AVHRR Pathfinder Sea Surface Temperature
- Global rasters of sea temperature- and ice-related parameters for
1962-2008; various time periods, quality flags, and conditions
World Ocean Atlas 09 - Familiar global
multi-depth grids used in
3.4 Obtaining Standard-Depth Analyzed Parameters from the World Ocean
This exercise will
focus on the first item above, in yellow.
|3. In the various
data product categories, you'll find frequent references to Quality Flags.
The author provides this direct quote from the Pathfinder User Guide to help
explain these flags:
"The overall quality flag is a relative assignment of SST
quality based on a hierarchical suite of tests. The Quality Flag varies from
0 to 7, with 0 being the lowest quality and 7 the highest. For most
applications, using SST observations with quality levels of 4 to 7 is
typical. For applications requiring only the best-available observations (at
the expense of the number of observations), use quality levels of 7 only."
Pathfinder User Guide
You will also find data products identified
as DAY or NIGHT or sometimes DAY-NIGHT. The NODC has reported that
DAY-NIGHT means the average of the daytime and nighttime values. They
recommend this value for routine use, unless you have a special reason to
use only the DAY or NIGHT values.
|4. Select CHOOSE DATASET to
open this main menu. Then navigate down to PATHFINDER 5.2 RI STATISTICS >
GRID > DAY-ONLY
|5. Navigate down and select
the MEAN SEA SURFACE SKIN TEMP IN AVHRR PATHFINDER V5.2 SST QUALITY LEVEL =
|6. This data map window will
open, probably without any data visible (due to lack of data on this
particular day (JAN 1, 1981).
|7. You can pick a different
day to check that the LAS is working.
|8. Now, we'll
leave the MAP MODE of the LAS and use the TIME-SERIES MODE.
|9. In the left-side menu,
select LINE PLOTS > TIME-SERIES
The map changes to show a single cursor
location, marked by a small brown circle. It is located at the main
origin for earth mapping, the 0,0 location in the Gulf of Guinea.
|10. Now we need
an exact latitude-longitude location for our data time-series. Let's
use the capitol of Liberia, Monrovia. We need the Batch Geocoding
database to do that. Open it by clicking the above link.
|11. This is the
complete main page for the site.
|12. Enter the location name
in the INPUT window.
|13. Make these choices and
then click on GEOCODE.
|14. These values will appear
in the OUTPUT window.
|15. Copy the latitude and longitude
values into the LAS geographic location panel.
NOTE: You can also simply drag
the circle to a desired location (approximately)
|16. Select any date range you
want. Here the available maximum window is selected.
|17. Then find and check the
UPDATE PLOT control.
|18. The time-series appears.
Examine it to get a good idea of the size of the signal, the obvious annual
signal, and the unfortunate gap near the middle of the record.
graphic can be captured for use in publication/reports, with the PRINT
control (along the top row. [Don't forget appropriate credit to the
|19. Select SAVE AS along the
top row of controls. There are several format choices,, including
- NetCDF - Binary format, already familiar to you; compatible
with Saga, IDV and ncBrowse.
- CSV - Comma-separated variables (ASCII); useful to load into
Excel or any other software that can analyze time-series data
|20. Here is the dataset you
see above, exported as CSV. There's plenty of good metadata to
identify the data, and they are in a very simple format for loading into
your own software.
If you need to use these data, make sure to save them in an appropriate location with a good, long filename.
|21. Now we need
to look at a "classic climatology".
|22. Navigate in the main menu
to this location for the CLASSIC grids.
Open the 1982-2008 MONTHLY
|23. There are
many products and quality levels provided here, so take the time to explore
through them and get a good idea of what's available.
|24. Navigate to and select
MONTHLY SST CLIMATOLOGY; DAY-NIGHT AVERAGE, QUALITY FLAG 7
term "day-night" means a combination of both, not the difference between
|25. If UPDATE PLOT is
checked, this graph will appear (after a short wait). This is exactly
the same as the climate graphs used by local tourist agencies and travel
companies to describe conditions at coastal locations.
|26. These data
can also be saved for use in other applications, as you did above.
|27. As an example of how to
use these links, here's a GIS-produced map where we can give users a simple
CLICK HERE link to SST climate data.
You can use FrontPage or ArcGIS to
place a "hot spot" on the map at Monrovia, and link that to either of the 2
Go ahead and click on the map to see one possibility. You can do
this to make a national or local "atlas" of seasonal conditions at resorts,
beaches or ports, for example.
|28. As always,
you should copy any URLs of interest into a log where you can keep them for