Experimental CCA Forecasts of Canadian Temperature and Precipitation --- Dec Jan Feb 2002
contributed by Amir Shabbar
Climate Research Branch, Meteorological Service of Canada, Downsview, Ontario, Canada
In the last several issues of this Bulletin, forecasts of Canadian temperature and precipitation using the multivariate statistical technique of canonical correlation analysis (CCA) were presented. For Canada, 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 have been developed. Here, we present the forecasts for Dec-Feb 2002 using the predictor fields through August 2001. This is a 6-month lead forecast. More details about the Canadian CCA-based seasonal climate prediction can be found in Shabbar (1996a, 1996b) and Shabbar and Barnston (1996).
Figure 1 shows the CCA-based temperature forecast for the 3 month period of Dec-Feb 2002 expressed as standardized anomaly. Table 1 shows the value of standard deviation in oC at selected stations. The mean skill over all 51 stations is given in the caption beneath each forecast map. The field significance is also shown, reflecting the probability of randomly obtaining overall map skill equal to higher than that which actually occurred. Field significance is evaluated using a Monte Carlo procedure in which the forecast versus observation correspondences are shuffled randomly 1000 times. The field of cross-validated historical skill (correlation) for the forecast time period is shown in Figure 2. The forecast has a good expected skill: a mean national score of 0.30 and a field significance of 0.016. The skill of the temperature forecast is the highest in winter in Canada. Local skill are highest from the southern Canadian Prairies extending into central Quebec and Newfoundland. Useable skill is also found over the Northwest Arctic. Modest skill is found over the Yukon, southern British Columbia and the Maritime Provinces. A large area of Canada eastward from the Manitoba-Saskatchewan border is expected to have negative temperature anomaly; positive temperature anomalies are forecast over most of western Canada.
Figure 3 shows the CCA-based precipitation forecast for the 3 month period of Dec-Feb 2002 expressed as standardized anomaly. Table 1 shows the value of standard deviation (mm) at a selected few stations. Cross-validated historical skill (correlation) for this time period is shown in Figure 4. The forecast has moderate expected skill: a mean national score of 0.22 and a field significance of 0.000. Local skills are highest over sections over southern Prairies extending into the Great Lakes region. Except for southern Manitoba, most of southern Canada is expected to have a deficit in Dec-Feb precipitation. Only western portions of Northwestern Territories and Newfoundland show sufficiently above normal values.
Over the last several months, both oceanic and atmospheric measurements in the tropical Pacific have indicated ENSO-neutral conditions. A number of dynamical models are indicating the development towards positive sea surface temperature anomalies and an evolution towards a weak warm ENSO episode for the rest of 2001 and early 2002. There is no clear consensus however. In the absence of a strong ENSO influence, the Dec - Feb 2002 forecast recognizes the recent warming trend in western Canada and a cooling trend in eastern Canada. Additionally, natural variability of the mid latitudes forms an important component of the Dec - Feb 2002 forecast.
References:
Shabbar, A., 1996a: Seasonal prediction of Canadian surface temperature and precipitation by canonical correlation analysis. Proceedings of the 20th Annual Climate Diagnostic Workshop, Seattle, Washington, Oct. 23-27, 1995, 421-424.
Shabbar, A., 1996b: Seasonal forecast of Canadian surface temperature by canonical correlation analysis. 13th Conference on Probability and Statistics in Atmospheric Sciences. American Meteorological Society, San Francisco, California, Feb. 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.
Table 1. Standard deviation of temperature (Temp) and precipitation (Prcp) for the 3 month period December through February at selected Canadian stations.
| Station | (oC) | (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 |
Captions
Figure 1. CCA-based temperature forecast for the 3 month mean period of Dec-Jan-Feb 2002. Forecasts are represented as standardized anomalies.
Figure 2. Geographical distribution of cross-validated historical skill for the forecast shown in Fig. 1, calculated as 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 0.30. Field significance is 0.016.
Figure 3. CCA-based precipitation forecast for the 3 month mean period of Dec-Jan-Feb 2002. Forecasts are represented as standardized anomalies.
Figure 4. Geographical distribution of cross-validated historical skill for the forecast shown in Fig. 3, calculated as 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 69 stations is 0.22. Field significance is 0.000.
