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Monday, March 2, 2009

SST Anomalies of U.S. “Coastal” Waters

I’ve moved to WordPress.  This post can now be found at SST Anomalies of U.S. “Coastal” Waters
And Two Quick Visual Comparisons To The GISS Contiguous 48 U.S. Surface Air Temperature Anomalies


Figure 2 and Figures 4 through 7 are based on ERSST.v2 data. Figure 8 uses HADISST data for the second SST comparison to GISS U.S. contiguous 48 land surface temperature anomalies.


Figure 1 shows the area and coordinates used for the SST Anomalies of Contiguous United States “Coastal” Waters. It combines “offshore” Atlantic, Gulf of Mexico, and Pacific SST Anomalies.
Figure 1

The time series of the combined Atlantic, Gulf of Mexico, and Pacific SST Anomalies from January 1880 to January 2009 are illustrated in Figure 2. The data presented is raw and smoothed with a 12-month running-average filter. Referring to the smoothed data, SST anomalies for this depiction of U.S. Coastal Waters dropped from ~1880 to ~1910, then rose until ~1940. (This Dip and Rebound is typical of many SST anomaly datasets.) The decline in SST anomalies from ~1940 to the early-to-mid 1970s is interrupted by an exaggerated response to the 1957/58 El Nino. (Considering there was a multiyear La Nina just before it, from April 1954 to January 1957, the response to the 1957/58 El Nino may not be too unusual.) And then from 1976 to present, SST anomalies for the combined Atlantic, Gulf of Mexico, and Pacific dataset rose with what appears to be responses to ENSO events and volcanic aerosols. Much of the rise in last three decades appears to occur from June 1975 to January 1978. This would fall into line with a rebound from another multiyear La Nina that took place essentially from May 1973 to May 1976, compounded by back-to-back El Nino events in 1976/77 and 1977/78.

What stood out, again using the smoothed data as reference, was the fact the SST anomalies are approximately the same now as they were at the beginning of the data, back in 1880.
Figure 2


Figure 3 illustrates the areas and coordinates used for the SST anomaly datasets of the West, Gulf, and East Coast of the contiguous United States.

Figure 3

The SST anomalies for the Northeast Pacific off the coasts of California, Oregon, and Washington are illustrated in Figure 4. There is a definite influence of ENSO, with the major spikes in 1941, 1958, and 1998 corresponding to El Nino events. The Dip and Rebound in SST anomalies from the 1880s to 1940s is also visible. And once more, present SST anomalies are similar to those in 1880.
Figure 4

In the Northern Gulf Coast SST anomalies, Figure 5, the periods of the rises and falls are different than most SST anomaly datasets. The mid-century peak in SST anomalies occurs about 5 years early in 1936, and the late 20th-Century trough bottoms out in the late 1980s, approximately ten years after the global shift in SST anomalies. Note, based on the smoothed data, present SST anomalies for the Northern Gulf of Mexico are lower than they were in 1880.
Figure 5

For the North Atlantic off the East Coast of the U.S., Figure 6, the curve of the long-term SST anomalies are similar to the Gulf Stream Sea Surface Temperature (SST) Anomalies, as illustrated in the linked post. That is, the SST anomalies during the 1930s through 1950s peaked higher than they did during the past thirty years. And again, current SST anomalies are approximately the same today as they were at the beginning of the dataset in 1880.
Figure 6


GISS, the most often blogged about surface temperature dataset, provides a subset for Contiguous 48 U.S. Surface Air Temperature (land-based temperature) Anomalies. For their combined land plus sea surface temperature data, GISS employs a combination of SST anomaly data sources. They use HADSST data from January 1880 until November 1981 and then OI SST data afterwards. While I have not created, and do not intend to create, a mixed SST anomaly dataset to match how GISS created theirs, I have provided comparative graphs of their land surface data for the contiguous U.S. and two long-term SST anomaly datasets, HADISST and ERSST.v2. Refer to Figures 7 and 8. Both of the SST anomaly datasets are for the coordinates illustrated in Figure 1. I used the KNMI Climate Explorer to shift the base years of the SST anomaly datasets to 1951 to 1980 so that they matched the base years of the GISS data. I then converted the monthly data to annual mean data.

Note how in Figure 7 the GISS surface temperature data tends to follow the overall trends established by the ERSST.v2 SST anomalies, with the land surface temperatures amplifying ENSO, volcanic, and other “noise.”
Figure 7

When compared to the HADISST data, the GISS land surface temperature anomalies do not follow SST anomalies as well, especially during the period of ~1910 to ~1940, Figure 8. But the HADISST data does seem to better agree with the GISS data during the 1980s and 1990s. Then again, these comments are based on visual impressions.
Figure 8

The differences between the two SST anomaly data subsets can be seen in the gif animation of the preceding two graphs. Refer to Figure 9. There is a significant difference between the ERSST.v2 and HADISST anomaly data. This was discussed further in my post “Why Does GISS Use HadSST2 Data from 1880 to 1981?
Figure 9

Someone with a statistics background could provide a detailed comparative analysis of the GISS LST and the two SST datasets, so I won’t carry the comparisons any farther.


The GISS U.S. Temperature Anomaly data can be found here:

The ERSST.v2 and HADISST anomaly data are available though the KNMI Climate Explorer website:

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