Climate Observations

Monday, July 13, 2009

Animations of Weekly SST Anomaly Maps from January 3, 1996 to July 1, 2009

The following four animations of Sea Surface Temperature (SST) anomalies were created using the mapping feature (Full Version) of the NOAA NOMADS system for the weekly OI.v2 SST data:
http://nomad3.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?ctlfile=oiv2.ctl&varlist=on&new_window=on&ptype=map&dir=

The “Contour interval for var1” was set at 0.2 deg C to bring out the lower-intensity temperature anomalies. “white” was set at “0” so that blues represented negative anomalies and reds represented positive anomalies. All four videos last for approximately 2 1/2 minutes.

Please click on the videos to watch them in a larger size at YouTube. There they can be expanded to full screen and set to high definition.

ATLANTIC OCEAN

The North Atlantic has the highest SST anomaly linear trend of all of the ocean subsets. Refer to my post Putting The Short-Term Trend Of North Atlantic SST Anomalies Into Perspective. And of the three major ocean subsets, the Atlantic Ocean has the highest OHC linear trend. This is illustrated in my post Levitus et al (2009) Ocean Heat Content – Comparison of The Ocean Basin Data. Does the Atlantic SST Anomaly Animation help show the reasons?

In addition to the surges of heat in the North and South Atlantic during El Nino events, there are a number of paths that warm SST anomalies enter the South Atlantic during ENSO neutral and La Nina periods. Occasionally, the Benguela Current carries these warm water anomalies north along the Southwest Coast of Africa, where they are then carried west by the Atlantic Equatorial Currents. The warm anomalies either return to the South Atlantic, following the currents of the South Atlantic gyre, or they enter the North Atlantic. Once in the North Atlantic, they travel north, and appear to do that quickly. These additions of elevated SST anomalies during La Nina and ENSO-neutral periods also help explain why There Are Also El Nino-Induced Step Changes In The North Atlantic.

http://www.youtube.com/watch?v=yagfQTrwTj0
Atlantic Ocean SST Anomaly Animation 1996 to 2009

INDIAN OCEAN

The Indian Ocean animation shows very “noisy” SST anomalies, without any obvious reoccurring pattern. I was hoping to illustrate evidence of the Indian Ocean Dipole. In a future post, I’ll try to do so.

http://www.youtube.com/watch?v=X17kkriIIKc
Indian Ocean SST Anomaly Animation 1996 to 2009

PACIFIC OCEAN

ENSO events stand out in the Pacific Ocean SST anomaly animation. It is possible to differentiate between traditional El Nino events like the 1997/98 El Nino (initially forms in the eastern equatorial Pacific) and the El Nino Modoki events of 2002/03 and 2004/05 (initially form in the central equatorial Pacific). Occasionally, the Pacific Decadal Oscillation (PDO) pattern in the North Pacific (north of 20N) makes its presence known, as does the basin-wide pattern of the Interdecadal Pacific Oscillation (IPO).

In a future post, I’ll discuss a sequence of events that appears to occur during traditional El Nino events. Note how, before the formation of the 1997/98 El Nino, the Humboldt Current carries warm Southern Hemisphere SST anomalies up along the west coast of South America to the eastern equatorial Pacific. Yet RSS MSU TLT Time-Latitude Plots (refer to RSS MSU TLT Time-Latitude Plots...) clearly show that the majority of the heat from the 1997/98 El Nino was transported to the mid-to-high latitudes of the Northern Hemisphere. Does this mean that El Nino events transport heat from the Southern Hemisphere to the Northern Hemisphere?

http://www.youtube.com/watch?v=d8KupSFlb9w
Pacific Ocean SST Anomaly Animation 1996 to 2009

GLOBAL

In addition to the processes that appear in the videos of the three major oceans and the interactions between them, the Global SST anomaly animation also shows the seasonal shifts in the SST anomalies within the Northern and Southern Hemispheres. There also appears to be a shift between them, where the higher SST anomalies appear during the summer months for each hemisphere.

Note also that the Indian Ocean anomalies no longer seem so noisy.

http://www.youtube.com/watch?v=1ir1w3OrR4U
Global SST Anomaly Animation 1996 to 2009

Sunday, July 12, 2009

Similarities of the Multiyear Periods Following Significant El Nino Events Since 1970

The 1982/83 and 1997/98 El Nino events are considered the significant ENSO events of the 20th century. Their peak SST anomalies stand above all others. Refer to Figure 1. Well…maybe not. As Karl reminded in the El Nino – same but different thread at WattsUpWithThat, the 1972/73 El Nino came in a close third.

http://i28.tinypic.com/14l3vuw.png
Figure 1

Figure 2 is a 150-month-long comparison of NINO3.4 SST anomalies for the 1972/73 and 1997/98 El Nino events and for the decades or so following them. With the exception of the upswing at the end of the 1972/73 El Nino (purple) curve and the downswing at the end of the 1997/98 El Nino (brown) curve (the upswing and downswing are the 1982/83 El Nino and the 2007/08 La Nina, respectively), the two curves of the secondary upsurges in NINO3.4 SST anomalies are remarkably similar.
http://i25.tinypic.com/166y9vt.png
Figure 2

The explosive eruption of El Chichon in 1982 minimized (eliminated?) the heat transport from the 1982/83 El Nino event. This can be seen in an MSU TLT Time-Latitude Plot from RSS, Figure 3. So for this post, we’ll consider the 1982/83 El Nino to be dysfunctional and exclude it from this post.
http://i25.tinypic.com/dopbgj.jpg
Figure 3

And soon after the effects of the volcanic aerosols from El Chichon subsided, the 1986/87/88 El Nino occurred. Referring back to Figure 1, the SST anomalies of the 1986/87/88 El Nino did not peak as high as the 1972/73 and 1997/98 El Nino events, but the 1986/87/88 El Nino lasted through the entire year of 1987. The end result, there was a noticeable redistribution of heat from the 1986/87/88 El Nino, Figure 4. So in that respect, the 1986/87/88 El Nino was also a significant El Nino.
http://i27.tinypic.com/2upwivn.jpg
Figure 4

In Figure 5, I’ve added the NINO3.4 SST anomalies of the 1986/87/88 El Nino to the 150-month-long comparison with the 1972/73 and 1997/98 El Nino events. The 1986/87/88 El Nino also created a multi-year secondary surge in NINO3.4 SST anomalies that was similar in scale to the other two events.
http://i27.tinypic.com/2gt6k5t.png
Figure 5

Smoothing the three curves with 25-month running-average filters, Figure 6, helps illustrate the similarities in the three curves.
http://i29.tinypic.com/sc6fz6.png
Figure 6

CLOSING QUESTION

From 1970 to present (and excluding the 1982/82 El Nino), are the lesser El Nino events that occurred after the significant El Nino events of 1972/73, 1986/87/88, and 1997/98 simply aftereffects?

SOURCES

HADISST anomaly data is available through the KNMI Climate Explorer:
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere

I cut Figures 3 and 4 from Figure 13 in my post RSS MSU TLT Time-Latitude Plots...

The RSS MSU TLT Time-Latitude Plot without my notations is available from RSS here (their Figure 8):

http://www.ssmi.com/msu/msu_data_description.html

Wednesday, July 8, 2009

Comparison of El Nino Modoki Index and NINO3.4 SST Anomalies

I’ve prepared this post for those who want to compare El Nino Modoki Index data to NINO3.4 SST anomalies. I did not standardize the El Nino Modoki Index data. Note also that I scaled the NINO3.4 SST anomaly data by a factor of 0.5 to bring it into line with the El Nino Modoki Index data.

Last, keep in mind that the El Nino Modoki Index is a calculated value. Ashok et al describe the calculation as follows:

“EMI= [SSTA]A-0.5*[SSTA]B-0.5*[SSTA]C (1)

“The square bracket in Equation (1) represents the area-averaged SSTA over each of the
regions A (165E-140W, 10S-10N), B (110W-70W, 15S-5N), and C (125E-145E, 10S-20N), respectively.”

Link to the Ashok et al (2007) paper “El Nino Modoki and its Possible Teleconnection.”
https://www.jamstec.go.jp/frcgc/research/d1/iod/publications/modoki-ashok.pdf

Figure 1 illustrates those regions used in the El Nino Modoki Index. Keep in mind that the declines in the SST anomalies in Regions B and C help raise the El Nino Modoki Index, and vice versa.

http://i31.tinypic.com/33xeziu.png
Figure 1

Figure 2 is a long-term comparison of El Nino Modoki Index data and NINO3.4 SST anomalies. In Figures 3 through 6, I’ve shortened the time spans. I have not attempted to provide the threshold for the El Nino Modoki events on the graphs. You’ll have to scale that value on your own. You can use Figures 2 and 3 and the accompanying dialogue in my post There Is Nothing New About The El Nino Modoki for reference, but remember that the threshold was established for the standardized data.

Here are the graphs without further commentary.