[Previous Article] [Next Article]
Experimental CCA Forecasts of Canadian Temperature
and Precipitation -- Jan-Feb-Mar 1998
Contributed by Amir Shabbar1 and Anthony Barnston2
1Climate Research Branch, Atmospheric Environment Service, Downsview, Ontario, Canada
amir.shabbar@ec.gc.ca
2Climate Prediction Center, NOAA, Camp Springs, Maryland
Over the last few years of this Bulletin, forecasts of Canadian temperature and precipitation using
the multivariate statistical technique of canonical correla-tion analysis (CCA) have been presented.
For Canada, we have developed the predictive relationships between evolving large scale patterns
of quasi-global sea surface temperature, Northern Hemisphere 500 mb circulation, and the
subsequent Canadian surface temperature and precipitation. In this issue we present forecasts for
Dec-Jan-Feb 1997-98 using the predictor fields through May 1997. These forecasts are made with
a lead time (the time from the end of the predictor period to the end of the predictand season) of 9
months. Further detail about Canadian CCA-based seasonal climate prediction is found in Shabbar
(1996a, 1996b) and Shabbar and Barnston (1996).
Figure 1 shows the CCA-based temperature forecast for the Dec-Jan-Feb 1997-98 period,
expressed as standardized anomaly. Table 1 shows the value of the standard deviation in C at
selected stations. The mean skill over all 51 stations, and the associated field significance, are
given in the caption beneath the forecast map. The field of cross-validated historical skill
(correlation) for the Dec-Jan-Feb forecast time period at this lead time is shown in Figure 2. The
forecast has a mean national score of 0.26. The field significance is 0.016, which surpasses the
traditional 0.05 rejection cutoff. Field significance reflects the probability of randomly obtaining
an overall map skill equal to or higher than that which actually occurred. It is evaluated using a
Monte Carlo procedure in which the forecast versus observation correspondences are shuffled
randomly 1000 times. The skill of the temperature forecast is highest in winter in Canada.
Local skill is highest from the southern Canadian Prairies extending into central Quebec, and
modest skill is found over the Mackenzie valley. A large area of Canada from the Yukon through
the Prairies and into Quebec is expected to have positive temperature anomalies; negative
temperature anomalies are forecast over the high arctic Islands.
Figure 3 shows the CCA-based precipitation forecast for the Dec-Jan-Feb 1997-98 period,
expressed as standardized anomaly. Table 1 shows the value of the standard deviation (mm) at
selected stations. The spatial field of cross-validated historical skill (corre-lation) for this lead and
time period is shown in Figure 4. The forecast has moderate expected skill, with a mean national
score of 0.20 and a "perfect" field sig-nificance of 0.000. Local skills are highest over sections
over southern Prairies extending into the Great Lakes region. Most of southern Canada is
expected to have a deficit in Dec-Jan-Feb precipitation. Only western por-tions of Northwestern
Territories show above normal values.
Since early 1997, most atmospheric and oceanic indices are clearly showing the onset of a warm
ENSO episode. Additionally, most statistical and dynamical models are predicting further
evolution of a warm episode for the rest of 1997. The Dec-Feb 1998 forecast recognizes the
continuing influence of the warm event on the Canadian climate over the winter season.
Table 1. Standard deviation of temperature (Temp) and precipitation (Prcp) for the 3 month period Dec-Jan-Feb at selected Canadian stations.
| Station | Temp (oC) | Prcp (mm) |
| Whitehorse | 5.7 | 8.6 |
| Fort Smith | 4.2 | 9.1 |
| Innujjuak | 3.4 | 7.4 |
| Eureka | 3.5 | 2.0 |
| Vancouver | 1.6 | 51.9 |
| Edmonton | 4.5 | 10.8 |
| Regina | 3.9 | 9.3 |
| Winnipeg | 3.4 | 11.9 |
| Churchill | 3.1 | 10.1 |
| Moosonee | 3.1 | 18.6 |
| Toronto | 2.3 | 20.7 |
| Quebec City | 2.6 | 35.8 |
| Halifax | 2.0 | 56.7 |
| St. John's | 2.5 | 55.0 |
Shabbar, A., 1996a: Seasonal prediction of Canadian surface temperature and precipitation by
canonical correlation analysis. Proceedings of the 20th Annual Climate Diagnostics Workshop,
October 23-37, Seattle, Washington, 421-424.
Shabbar, A., 1996b: Seasonal forecast of Canadian surface temperature by canonical correlation
analysis. 13th Conference on Probability and Statistics in the Atmospheric Sciences. American
Meteorological Society, San Francisco, California, February 21-23, 339-342.
Shabbar, A. and A.G. Barnston, 1996: Skill of seasonal climate forecasts in Canada using
canonical correlation analysis. Mon. Wea. Rev., 124, 2370-2385.
Fig. 1. CCA-based temperature forecast for the 3 month mean period of Dec-Jan-Feb 1998.
Forecasts are represented as standardized anomalies.
Fig. 2. Geographical distribution of cross- validated historical skill for the forecast shown in Fig.
1, calculated as a temporal correlation coefficient between forecasts and observations. Areas
having forecast skill of 0.30 or higher are considered to have utility. The mean score over 51
stations is 0.26. Field significance is 0.016.
Fig. 3. As in Fig. 1 (CCA anomaly forecast), except for Dec-Jan-Feb 1998 precipitation.
Fig. 4: As in Fig. 2 (geographic distribution of correlation skill) except for the precipitation
forecast shown in Fig. 3. The mean score over 69 stations is 0.20. Field significance is 0.000 (see
text).
