This thesis examines the possible teleconnections
between North Pacific sea surface temperatures and synoptic
extended dry spells and droughts on the Canadian Prairies.
Dry spells are a natural occurrence on the Canadian Prairies.
It is also a well known fact that extended dry spells often
lead to droughts. The major synoptic cause of extended dry
spells and droughts on the Canadian Prairies includes the
presence of a quasi-stationary mid-tropospheric ridge over
the area. What causes this ridge to become quasi-stationary
is not certain. Some previous studies have shown that sea
surface temperature anomalies over the North Pacific Ocean
may be a significant factor in affecting upper atmospheric
long wave patterns and abnormal weather conditions over North
America.
The main objective of this study is to determine if
there is a significant statistical relationship between
anomalous North Pacific sea surface temperatures and the
occurrence of extended dry spells and droughts on the
Canadian Prairies during the agricultural growing season (May
- August) for the period 1948-1988. Individual extended dry
spells are identified and then ranked in terms of their
severity. Results show a significant correlation between
these extended dry spells and a positive sea surface temperature anomaly gradient located in the east central
North Pacific. This gradient consists of a region of
anomalously cold water located in the east-central North
Pacific in the area bounded by 30°N to 40°N latitude and
165°W to 135°W longitude and a region of anomalously warm
water found along the west coast of North America bounded by
the coordinates 45°N to 55°N latitude and 130°W to 125°W
longitude. A probability model shows that the longer this
gradient persists, the greater the probability of a major
extended dry spell. A conceptual model is also constructed
and shows a distinctive pattern in sea surface temperature
anomalies and 50 kPa anomalies associated with the major
extended dry spells