The Japan Meteorological Agency (JMA) has devised a new
SST-based index for determining El Nino and La Nina-El Viejo events. 
(Marine Department Report, Japan Meteorological Agency, 1991):

	(1.) Calculate monthly SST anomalies averaged for the area 4N
                 to 4S and 150W to 90W. 

	(2.) Apply a 5-month running mean of the data. The 5-month
                 running mean of SST anomalies is implemented to smooth 
                 out possible intraseasonal variations.

The data file (jmasst1949-today.filter-5) is the 5-month running mean
of the anomalies for the years 1949 to today. The data are organized so
that there is one record for each year. Each record contains the year
and 12 monthly values. The SST anomalies are in tenths of a degree
(times 10). Values of 999 indicate no value.

The data file (jmasst_recon1868-1949.filter-5) is the 5-month running
mean of the anomalies for the years 1868-1949 based on reconstructed
monthly mean SST fields. The reconstructed SST fields were computed
using orthogonal projection technique (Meyers et al., 1997). The JMA
index was calculated identically to that described previously, meaning
the JMA climatological values given below were used to calculate the
JMA SST anomalies. A 5-month running mean was applied as well to
result in the JMA index. Values of 999 indicate no data available.

The data file (jmasst1868-today.filter-5) is the JMA index based on
reconstructed monthly mean SST fields for the period Jan 1868 - Feb
1949, and on observed JMA SST index for March 1949 to present. In
other words combining previous two files for convenience. Values of
999 indicate no data available.

Thus for the first record:
1949 999 999   0   0  -1  -2  -6  -8 -10 -11 -13 -13 
The anomalies for this year are negative, with a value of -13 indicated a cold
equatorial Pacific SST anomaly of -1.3 Deg-C.

			======
			 Note:
			======
The "normals" or monthly cliamtological means used by JMA are:
Jan=25.4
Feb=26.2
Mar=26.9
Apr=27.1
May=26.6
Jun=26.1
Jul=25.2
Aug=24.6
Sep=24.6
Oct=24.6
Nov=24.6
Dec=24.9

Please see email at the end of this file for description on how these means
were calculated at JMA.

An interesting use of these data can be found in Sittel, M.C., 1994,
"Marginal probabilities of the extremes of ENSO events for temperature
and precipitation in the southeastern United States" Technical Report
94-1. August 1994. 

Available from: Center for Ocean-Atmospheric Prediction Studies,
Florida State University, Room 020 Love Bldg, Tallahassee, FL
32306-3041.

Meyers, S. D., J. J. O'Brien, and E. Thelin, 1997: Reconstruction of
monthly SST in the Tropical Pacific ocean during 1868-1993 using
adaptive climate basis functions. J. Climate, submitted.
=====================================================================

Dr. James J. O'Brien
Center for Ocean-Atmospheric Prediction Studies
Florida State University
235 E. Dirac/Ste 200 Johnson Bldg
Tallahassee, FL  32306-3041

Email:   obrien@coaps.fsu.edu

(904) 644-4581(Voice)   
(904) 644-4841(Fax)

		======================================
		Other Informations regarding JMA Index

		Email from Japan Meteorological Agency
		=======================================

Description of JMA SST index:

From ocean@hq.kishou.go.jp  Wed Sep 13 02:13:42 1995
Subject: JMA SST Index 

Dear Mr. Nunez,

Thank you for your e-mail of 5 September on JMA SST Index.

Unfortunately, we calculated the Index only from 1949. 

JMA determines monthly mean analysed SST from 1946 for each 
two-degree latitude and longitude box over the global ocean 
on the basis of conventional SST observations.  
Normals of monthly mean SST for each 2-deg x 2-deg box in 
the global ocean were calculated from the monthly mean analyzed 
SSTs for the period from 1961 to 1990.  Please refer to our 
publication 'Climatic Charts of Sea Surface Temperatures of 
the Western North Pacific and the Global Ocean'(1991).     

The SST climatology and mean SST  for the area B 
(4N - 4S, 150W-90W, See Table 1 (a) of the Monthly Ocean Report) 
is an area average of the corresponding 120 (4 X 30 boxes) 
monthly mean SST normals and analysed SST values, respectively.  
Thus, the base period of the climatology is from
1961 to 1990.  The anomaly (i.e. so-called JMA SST Index) is an area
average of  a deviation from the normal in each box.

If you have any further questions, please let me know.

Best regards,

Kunio Sakurai
Head, El Nino Monitoring Center
Oceanographical Division
Marine Department