3

Weather Forecasting for Health and Society in Canada at
National and Local Scales
Lawrence NKEMDIRIM
Department of Geography, Earth Science 324, University of Calgary,
Calgary, AB, Canada T2N 1N4
e-mail: nkemdiri@ucalgary.ca

Abstract
Canada is a very big country with large relief features resulting in many climates and several
climatic regions. The Canadian Meteorological Service reflecting the diversity of weather conditions in
the country provides weather forecast for the nation through its national, regional and local centres. This
review focuses on Canada’s weather forecasting system both short term, long range and seasonal, andforecast products for people and environments. The Chinook, which causes abrupt and short termchanges in weather, is used to illustrate weather-health relationships in Canada at a regional scale.
Chinook type 1 events cause very poor air quality to which a variety of illnesses among susceptible
populations has been attributed. Chinook type 2 is also correlated with poor health ranging from irritability to severe mental depression, suicides and heart attack.
Key words: chinook, föhn, weather-health forecasting, weather-health relationship, windchill

1. Introduction
Perhaps due to its high latitude location in the
Northern Hemisphere, the most common view ofCanada’s climate is perpetual cold. While the country
above the Arctic Circle may deserve this reputation,
the southern parts where the vast majority of thepeople live, have many climates ranging from mild
Mediterranean types along the Pacific and Atlantic
Coasts to a moderately continental climate around theGreat Lakes. The Prairies which extend width-wisefrom just west of the Great Lakes to the foot of the
Rocky Mountains and length-wise from the CanadaUnited States border to the Boreal forest, is colder
than the rest of southern Canada. Winters in the
Prairies can be very cold and summers cool and short.
However, it is in this region that we find one of themore fascinating examples of short-term weather phenomenon, the Chinook.
In areas of the world where long mountain chainslie more or less at right angle to the prevailing wind,
given the right set of conditions, strong and frequently
gusty winds may occasionally blow down the leeslopes of the mountains affecting weather in large
areas downwind. Some of the best known mountainwinds include the North American Chinook, theZonda in Argentina, Föhn (Germany and Central
Europe), Santa Ana (California, United States),
Bergwind (South Africa) and the Northwester (NewGlobal Environmental Research
11: 3-11 (2007)
printed in Japan

Zealand). These winds which are normally dry andwarm relieve cold weather in winter and exacerbate
high temperatures in spring and summer. Their arrival
is often marked by very steep temperature rise withinshort time intervals. In Spearfish, South Dakota, forexample, temperature rose from –20°C to +7°C in
2 minutes to mark the arrival of the Chinook on
January 20, 1943. Their end can be equally abrupt.
The warm event in Spearfish lasted 90 minutes.
Thereafter temperature dropped 32° in 27 minutes.
Although such mountain winds bring welcome relief
from cold weather in the winter, they can be environmentally unfriendly. They melt winter snow packs
thereby upsetting the natural water balance cycle.
They may fool vegetation into budding in mid-winter,a phenomenon known to damage the long term healthof forests. They fan forest and grass fires. In Canada,
Chinooks are correlated with poor air quality and illhealth among susceptible populations.
Weather forecast is part of life in Canada. People
wake up to it in the morning and retire to bed at nightknowing what the next day’s weather may hold instore. It influences what they wear, how they commute
to work, their leisure activity and even what to eat anddrink. The irony is that most Canadians are not evenaware that those actions reflect their response to theforecast. It is only during severe weather emergency
or when the forecast is wrong does weather forecasting receive the recognition it deserves. Although the©2007 AIRIES

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L. NKEMDIRIM

economic and social benefits to Canadians fromweather forecasting are valued in billions of dollars(Ambury, 2005; Mjelde & Penson, 2000), Canada
accepts that forecasting is a public good and funds it
mostly with tax money.
The main provider of weather forecast in Canada isEnvironment Canada’s Meteorological Service ofCanada (MSC). It does it through its national centre
located in Montreal, and regional and local offices
spread almost evenly across the country. Althoughweather-health relationships are not explicit in daily
forecasts, MSC’s forecast products are being used in
the private sector to develop and market such relationships. As well, MSC has developed or helped develop
indices to measure relationships between well-being
and severe weather. This review does the following:(a) describe Canada’s weather forecasting system,
forecast products and dissemination of forecasts; (b)describe current state of weather-health forecast in
Canada; (c) explain the synoptic conditions associatedwith the Chinook; (d) review present knowledge of
Chinook driven health impacts.

2. Weather Forecasting in Canada
MSC operates a National Prediction Programs
branch which leads and coordinates weather forecastin the country. Within this program, the Canadian
Meteorological Centre (CMC) provides the analysis,
forecast output and guidance used by the national andfive regional prediction centres. Typically, the national
centre prepares the national weather outlook whichforms the broad background for the more detailed regional forecasts performed at the regional centres. The
local forecast uses local knowledge and data to further
detail the prediction at the sub-regional scale. CMC
forecasting system consists of the following major
steps – data collection, data assimilation, numerical
weather prediction and model output-post processing.
The data utilised include the worldwide network ofstations, ships and buoys coordinated by the World
Meteorological Organisation, traditional observationsof surface atmospheric pressure, temperature, windvelocity, humidity and precipitation from hundreds ofmanual and automatic weather stations in Canada andacross the United States, and upper air data fromradiosondes, weather satellites and doppler radar.
The data go through the assimilation phase aimed
at gaining an understanding of current conditions
which MSC considers the most critical part of theforecast. Information gained from the most recent data
is used in conjunction with a numerical model’s forecast for the time of the recent data, to produce meteorological analysis charts. Together the charts present
best three-dimensional estimates of current distribution of temperature, moisture and wind, one for
Canada and a second for the Northern hemisphere.
The next stage in preparing the forecast is numerical
weather prediction (NWP). NWP is a supercomputer

simulation of the atmosphere. In Canada, NWP is
accomplished with the Canadian MeteorologicalCentre’s Global Environmental Multiscale (GEM)model. This model takes the analysis produced at theassimilation stage as a starting point from which it
evolves the atmosphere fast forward through time
based on the laws of physics and fluid dynamics. The
underlying principle is as follows. For a given location,
the weather forecast is determined from knowledge ofthe present weather at both the location and upstream
from where the next weather will likely come. The
forecast is then produced by estimating when the
upstream weather will arrive at the target location andhow it will be modified in transit. The longer the timeframe of the forecast, the further upstream knowledgeof present weather must extend. The configuration of
the GEM model operates on cells that are each 0.3
degree of latitude by 0.45 degree of longitude at time
steps of 45 minutes. In this way the changes that occur
in the state of the fluid (the atmosphere) is captured at
discrete time intervals ranging from hours to days.
The computer output for the intervals serves as thebasis for the forecast. NWP is normally performed
twice daily.
The model output is post processed before it ishanded to the forecaster. Post processing often
involves use of statistical or other numerical techniques to remove from the output known bias built
into the model. It may also require adjustments basedon consensus among other numerical forecast models.
The later procedure, normally referred to ensemble, isperformed in recognition of the chaotic nature of theatmosphere and possible presence of errors which may
have been introduced into the computation by poor orinadequate data that may amplify forward. The detailthat can be given in a forecast therefore decreases withtime as errors and chaos increase to a point where theforecast no longer reflects future weather. Ensemble
procedures help identify the time horizon of a usefulforecast.
At the final stages of the projection, the meteorologist may be guided by experience with similar weather
patterns that occurred in the past to interpret theweather conditions inferred from the post processed
data. The interpretation and guidance are made available to the regional and local centres for use in preparing the final forecast product for the public and otherclients. Regional and local centers further detail theforecast based on local conditions. Particularly at theregional and local levels, forecasters apply a techniqueknown as nowcasting. Nowcasting is used to project
weather in a time scale ranging from now to about
6 hours. It is driven primarily by human interpretationof incoming weather, normally small scale events
ranging from individual shower clouds to severe but
localised storms to frost pockets that are too small tobe resolved with reasonable accuracy by dynamic
models. Nowcasting is aided by late radar, local andsatellite data as well as eye witness reports ofWeather Forecasting for Health and Society in Canada

phenomenon such as funnel clouds.
The main products of Canada’s weather forecasting are as follows:(a) Weather warnings and watches where safety andsecurity of life and property are threatened.
Severe thunderstorms, tornados, hurricanes, blizzards and heavy snow are of particular interest inland areas. Severe storms at sea are of interest to
off-shore oil rig operators, fishing, shipping andaquatic recreational activities.
(b) Weather forecast for use by weather sensitive
activities including aviation and transportation(c) Forecast for agriculture, forestry, construction
and air quality(d) General interest public use forecast.
Seasonal Forecast
In Canada, interest in long range and seasonal
weather forecast, prudently referred to by weather
offices as outlooks, has grown driven in part byexperience with severe El Niño – Southern Oscillation(ENSO) episodes especially the 1982-1983 event andits negative social and environmental impacts. Today,
seasonal forecast is utilized in industries such as
agriculture, forestry, utilities and municipalities forplanning and management. CMC produces outlooks
for temperature and precipitation ranging from
0-9 months ahead. The 0-3 month outlook whichbegan in 1995 is based on an ensemble of 12 modelruns split between two dynamic models (Delorme
et al., 2001), the GEM (Côté et al., 1998) and CMC’s
General Circulation Model 2 (McFarlane et al., 1992).
The models are forced by sea surface temperature(SST), sea ice and snow. In the GEM, the SST
anomalies in the 30 days preceding the forecast are
fixed throughout the forecast period and they areadded to the evolving climatology. The sea ice extent
and snow cover analyses are relaxed toward theclimatology during the first 15 days of the forecast
period. In GCM2, the SST is treated similarly as in
GEM. However, sea ice cover is climatological all
along the numerical integrations. The snow cover is aprognostic variable of the model. Historical data areutilised to reduce drift in the models. The outlook for
air temperature is achieved by (a) determining the
average daily temperature via the model runs and (b)subtracting the climatologies of the models from themean forecast seasonal temperatures to derive theforecast anomalies of each model. The anomalies
derived from the two models are then normalized andaveraged to determine the outlook anomaly, expressed
as above, near normal and below normal. Outlook for
precipitation is prepared in a similar manner exceptthat precipitation totals are used rather averages.
A year later, outlooks for 3-9 months were introduced. However unlike the 0-3 month outlook, thepreferred forecast model is the Canonical Correlation
Analysis (CCA). CCA is an extension of multiple
regression analysis. But unlike traditional regression

5

analysis in which one predictand variable is regressedagainst two or more predictors, CCA regresses a set
containing multiple variables (predictands) against
another set of predictors. This widely used statisticaltechnique was adapted by Environment Canada’s
Climate Monitoring and Data Interpretation Division
to produce seasonal forecasts of surface air temperature and precipitation anomalies for Canada. The
forcing is provided by fields of SST anomalies foreach of the 12 months preceding the forecast. The SST
anomalies are averaged spatially over 10 × 10 degree
grid cells and over three-month periods. The analysed
values are then used to project temperature andprecipitation from a statistical relationship developed
between subsequent SST anomalies (predictors) and
precipitation and temperature anomalies (predictands)
trained with a 35-year data base (Shabbar & Barnston,1996). Skill in the forecast (agreement between
forecast and observation) was determined from thesame data base. CCA forecasts are available for 51
Canadian stations for temperature and 69 stations for
precipitation. The stations were chosen to cover the
Canadian area as uniformly as possible (Environment
Canada, 2005).

3. Destination of the Forecast
The end user is one of the most important component of weather forecast. The users include the generalpublic, the aviation, marine and fishing industries,
environmental agencies, forestry service, power andutility companies, roads and highways, Emergency
services and increasingly hospitals. The forecasterrequires knowledge of the target user and what is
important for its operation to prepare a suitable forecast and do so in appropriate terms and language. For
example, the aviation industry is concerned about fog,
visibility and cloud ceilings that may compromise
landing ease. Turbulence, icing potential, both on the
ground and during flight; thunderstorm activities aswell as the location of jet streams that may enhance or
reduce fuel efficiency are the types of information
given to the crew before take off and updated in flight.
The Canadian Meteorological Service (CMS) provides forecast for all end users from its regional
offices through direct briefing, direct telephone
conversation or via recorded messages and theInternent. In Canada, radio and television which provide regular bulletins to viewers and listeners roundthe clock are typical outlets for CMS forecasts. One ofthem, Weather Network Canada is a cable television
station dedicated exclusively to providing continuous
weather bulletin to the public nation wide. Owned andoperated by Pelmorex Inc, it has a website which
serves the public similarly. As well, MSC operates its
own radio broadcast. Weatheradio Canada is a nationwide network of radio stations broadcasting weather
and environmental news 24 hours a day in English andFrench directly from Environment Canada’s storm

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L. NKEMDIRIM

prediction centres. The majority of these stations
broadcast on VHF band to permit the transmission of
a 1,050 Hz tone that will trigger a Weatheradio
receiver’s internal alert system during an emergency.
In particular, Weatheradio Canada carries timely
warnings and watches for imminent severe weather
for land and sea.

4. Weather and Health Impacts
Weather impacts on human health and sense ofwell being has been suspected for a long time. However, such impacts are often difficult to quantify,
hence difficult to prove. This is in part due to themany variables that make up the weather and thesensitivity of people to different sets of them. Often
the number of “sufferers” is so small that real effects
are dismissed. Over the years, however, a consensus
has emerged that weather affects health. Studies showthat conditions such as migraines are aggravatedamong susceptible persons in areas that experiencesudden warming (Nursall & Phillips, 1980). Chronic
pain and arthritis are worsened by changes in temperature, dampness and precipitation. A rapid change inpressure can cause illness as well. Indeed, anomalous
increases in incidents of heart attacks, high bloodpressure and blood clots have been linked to airmasschange (Stoupel & Shimshoni, 1991). The durationand quality of light is a major factor in Seasonal
Affective Disorder (SAD).
In Germany, the National weather service incorporates weather-health relationships in its daily forecast.
This includes an index which measures the risk to particular health conditions associated with incoming
weather (http://www.donnerwetter.de/). In the United
Kingdom, they have applied this knowledge in aslightly different manner. During the 2000-2001
winter, the meteorological office and the departmentof health conducted a pilot study aimed at forecasting
hospital workload based on the probability of increased incidences of heart attacks, respiratory difficulties, falls and broken bones linked to specificweather types. During a two-week period which forecasted a slower than normal workload, one hospital
was able to schedule an additional 150 elective surgeries at a savings of $1.2 million (EnviroZine, 2001).
The CMC does not provide weather-health forecasts
similar to those available in Europe. However, theWeather Channel, a Cable Network based in the
United States, has been providing health related
weather forecast for some Canadian stations on television and web page. It is also available as a desktop(http://www.weather.com/common/help/maps/achesan
dpains.html). On the channel, the Aches and Pains
Index map, for example, graphically depicts areas ofhigher or lower levels of weather-related pain. The siteclaims that “areas of quiet, dry weather during thewarmer times of the year are most commonly associated with lower levels of aches and pains. High (orrising) surface pressure, low (or falling) humidity values, low probability of precipitation, calm winds, anddaytime temperatures higher than 21°C would all be
expected for lower levels of aches and pains to occur
from a meteorological standpoint.” Maps for common
ill health such as colds and influenza are also available.
MediClimTM developed indices based on 14 groups of
weather conditions to forecast weather related sickness (EnviroZine, 2001). Prototype of weather-healthmaps have been developed for ailments such as
migraine.
Even though the CMS does not provide healthrelated weather forecast, it has developed or helped
develop indices that measure human comfort in severe
weather. Two such indices are the Humidex and Wind
Chill index. The Humidex first used in 1965, describes
how hot humid weather feels to the average person by
combining the temperature and humidity factors into
an expression reflecting the perceived temperature
equivalent of the two factors. Normally used when air
temperature exceeds 30°C, the Humidex reflects not
only how stifling the air feels when the weather ischaracterized by high temperature and high humidity
but the imminent health danger associated with it(Table 1). While the Humidex is a hot season comfort
indicator, the Wind Chill does similarly for cold
weather. The wind chill represents how the temperature would feel on the skin of the average humanunder strong wind condition and cold air temperature.
It is a measure of the effect of the wind in accelerating
the transfer of heat from the warmer skin surface tothe colder atmosphere through direct heat exchange
and evaporative loss. Like Humidex, the Wind Chill
Index carries broad comfort and health warning (Table2). Wind Chill is included in weather forecast duringcold weather.
Table 1 Humidex and human thermal comfort.
Range of Humidex
Less than 29
30 to 39
40 to 45
Above 45
Above 54

Degree of comfort
No discomfort
Some discomfort
Great discomfort; avoid exertion
Dangerous
Heat stroke imminent

Humidex = T + 0.5555 (e – 10.0)
T is air temperature °C, e is the actual vapour pressure (mb).
e ≈ 6.11 × exp{5417.7530 × [(1/273.16) – (1/Td)]},Td is dewpoint temperature °C.

Table 2

Risk factors associated with Windchill (Twc)*.

Risk of frostbite in prolonged exposure (30 minutes) at –28
Frostbite possible in 10 minutes at – 40
(shorter time if sustained wind greater than 50 km/h.)
Frostbite possible in 5 minutes at – 48
(shorter time if sustained wind greater than 50 km/h.)
Frostbite possible 2 minutes or less at – 55
*Twc = 13.112 + 0.6215 T –11.37 U0.16 + 0.3965 T × U0.16
Twc is windchill temp (°C),T is air temp and U is wind speed at
10 m.

Weather Forecasting for Health and Society in Canada

5. The Chinook
In Canada the Chinook is a dry often gusty windwhich occasionally blows down the Rocky Mountains
into the lee side bringing warm weather to the eastern
slopes, the foothills and the western Prairies. These
three contiguous zones collectively known as Canada’s
Chinook belt, covers an area of about 80,000 km2
extending eastward from the Continental Divide to theAlberta-Saskatchewan border (110 W) and northwards
from the Canada-United States border (49°N) to
Latitude 52.5°N. Calgary (51°N, 114°W) is the largest
city in the Belt. The origin of the name, Chinook, is
steeped in legend. One story credits it to the first
European settlers who believed that the wind camefrom a territory occupied by Chinook Indians who
lived in the American northwest along the banks of theColumbia River and the coast of the Pacific Ocean(Ruby & Brown, 1976). A second traces the wordback to another Indian tribe, the Blackfoot, for whom
it means the “snow eater” similar to schneefresser
used by the Swiss for the Föhn. Yet a third legend
celebrates the Chinook as the spirit of an Indian
princess who was abducted in her prime in a war
against a competing tribe. Now we know that the wind
is a mainly pseudo adiabatic process involving the riseof a deep layer of moisture laden air from the Pacific
Ocean over the Rocky Mountains and its descentdown the eastern slopes of that mountain chain into
the foothills and Prairies.
The Chinook begins with orographic lifting on thewindward side of the Rockies which causes the air toinitially cool at the dry adiabatic rate (DALR) tosaturation somewhere up the mountain depending on
its moisture content and temperature of the rising air(Fig. 1). Thereafter, condensation begins and the rateof cooling drops to the wet adiabatic lapse rate
(WALR) which is approximately one-half of the dryrate as latent heat is released into the air stream via
condensation. Precipitation from the air stream
removes the moisture but leaves behind the converted

Fig. 1 Chinook Classic process.

7

latent heat. When the air descends on the leeward
slope, it warms at the dry adiabatic rate. Bearing in
mind that that the air is now enriched with extra heat
due to the moisture lost, it will arrive at various points
on the leeward slopes warmer than it was at equivalentelevations on the windward side (Fig. 1). Chinook
winds characterized by the cooling-condensation-rain
out-warming process are referred to in this review as
Chinook classic. There are occasions when theprocess is wholly adiabatic. This occurs when there is
no rain out behind the mountain. Any condensation
carried in the air stream is re-evaporated during
descent hence the latent heat released duringcondensation is reutilised. Consequently, when the air
arrives on the eastern slopes, for a given elevation, thetemperature is the same as it was at equivalent heighton the windward side. However, because in winter,
this warmer maritime air replaces a retreating shallow
cold and stable Arctic airmass which normallyoccupies the Chinook Belt in winter, the event feels
and behaves like a Chinook. The warmth is further
enhanced by descent to lower grounds in the farther
east (Nkemdirim, 1996). We will call this event
Chinook regular. Normally, for an air stream withsimilar temperature profile upwind (windward of themountain), Chinook classic is warmer than Chinook
regular. This difference in temperature is due to themoisture content of the respective air volume atorigin.
The Chinook events reviewed to this point arethose that reach ground. We classify them as Chinook
Type 2. A similar warm event that remains at heightprecluded from the ground by a fairly deep and stablelayer of cold Arctic air which normally occupies the
Chinook Belt during the winter is also called a
Chinook and designated a Type 1 event. Although
Chinook Type 1 may mark the incipient stage of a
Type 2 condition, it could stay aloft through several
days and may never reach the ground (Fig. 2).
Chinook Type 1 represents an extreme case of temperature inversion in the Belt. The inversion may con-

The numbers progressively indicate the sequence of changes occurring in the air
volume from its Pacific Ocean origin to its Chinook Belt destination.

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L. NKEMDIRIM

Fig. 2 Chinook Type 1 process.

The warm maritime air is precluded from the ground by the stable cold
Arctic air mass.

tinue even when the feature evolves into a Type 2 casefollowing the retreat (advance) of the cold air from theBelt or its erosion. Chinook Type 1 is frequently referred to as a pre-chinook condition (Cooke et al.,2003) even when it ends without ever touching
ground.

6. Synoptic Setting for Chinook Events

Fig. 3 Typical 500 kpa map during a chinook event.

The counterclockwise flow in the Low off the Pacificbecomes a clockwise motion in the ridge over theRockies.

Fig. 4 Typical sea level pressure map during a chinook
event.
10

Temperature (°C)

Figure 3 shows a typical synoptic setting for
Chinooks. This 500 hpa map shows (a) a Low off the
Pacific Coast and (b) a high centred in Northwest
United States ridging over the Canadian Rockies and(c) a Low extending from the Hudson Bay into thewestern prairies. The counter clockwise airflow in
the Pacific low becomes the clockwise motion thatdraws the Pacific air across the mountains towards the
Low in western Prairies. The sea level pressure map(Fig. 4) shows the wind blowing into Calgary from thesouthwest. Oard (1993) used a similar configuration toforecast Chinook weather in Montana, the American
state immediately south of the Canadian Chinook belt.
Arrival of both Chinook classic and regular is announced by the following weather conditions: (1)sustained winds from the west, specifically from any
direction between SSW and WNW inclusive; (2) afairly strong wind, the threshold value is 16.4 km h-1;(3) a sharp rise in temperature with the eventual mean
daily value exceeding the daily normal; (4) a drop in
relative humidity; (5) a requirement that the timing ofitems (3) and (4) correlate perfectly with the shift inwind to the westerly direction (Nkemdirim, 1995).
Some of these features are demonstrated in a Chinook
event recorded February 11-12, 1985 (Fig. 5). While
the patterns shown in Figs. 3 and 4 are identifiable innational prognostic charts, those of Fig. 5 are done in
the region and local centres in the nowcasting mode.
Because the Chinook is not always active simultaneously through the belt, local observation is criticalto a successful forecast of the event especially its
onset and termination.
There is no seasonal forecast for the Chinooks
equivalent to the national outlook provided by MSC.
Although the winds do not exhibit meaningful periodicities, they tend to be more numerous when winters

–5

–10

–15

–20

Fig. 5 A typical Chinook event.

Note the correspondence of rising temperature
with westerly winds.

Weather Forecasting for Health and Society in Canada
Table 3 Probability for runs of Chinook days in Calgary,
Canada.
Run Length (days)
1
2
3
4
5
6
20

Probability
0.36
0.24
0.14
0.12
0.06
0.05
0.0002(Source: Nkemdirim, 1997)

Table 4 Transition probability matrix from Chinook
event of x day(s) to event x + i days.
Event x(days)
1
2
3
4
5
6

1
.40
.32
.39
.29
.41
.52

2
.24
.26
.25
.29
.22
.04

Event x + i days
3
4
.08
.14
.21
.09
.15
.11
.15
.14
.09
.16
.31
.13

5
.07
.06
.05
.08
.09
.00

6
.06
.05
.04
.05
.03
.00

(Source: Nkemdirim, 1997)

are warm but they are not, by themselves, the cause ofwarm winters (Nkemdirim, 1997). That said; planners
may be guided by tables which provide probabilities
of Chinook events for each winter month, the expected monthly run length (the number of consecutive
Chinook days) as well as transitional probabilities
from 1 to 20 days (Nkemdirim, 1997). Tables 3 and 4
are samples taken from those tables.

7. Health Impact of the Chinook
One of the reasons cited by Calgarians for their
deep affection for their city is the Chinook. This warm
wind provides welcome relief from bone chilling prairie winter cold, –30° for example. The wind boosts
commerce, construction, and recreational and otherforms of outdoor activities. However, a small but
statistically significant minority claims to be adversely
affected by the event (Nkemdirim & Baines, 1985).
Their complaints range from irritability to physicaland mental health impairment including attemptedsuicide and a variety of cardio-vascular conditions(Nkemdirim, 1995). Some sufferers claim that they
can predict the arrival of the Chinook several days inadvance because of progressive signs of ill health felt.
Previously, the complaints were mostly anecdotal but
over the last two decades, there are theoretical, empirical and clinical evidence supportive of Chinook
induced health hazards. Normally, air quality in thiscity of 1 million is characterized as clean. Air Quality
Index (AQI) ranges from 1-25 most of the year. However, during Chinook type 1 events, the city’s AQI
often exceeds 100 indicating severe pollution (Hicks& Matthews, 1979). As well in spite of strong winds
air quality is also lower during Chinook Type 2(Nkemdirim & Leggat, 1978; Mintz et al., 2003).

9

Several studies indicate strong quantitative correlation
between air pollution and various forms of ill health.
In Canada, Health Canada estimated that 5,900
Canadians die each year due to air pollution. Experiments in California confirm strong linkage between
asthma and air pollution (McConnell et al., 2002;
Thurston & Bates, 2003). These findings collaborate
the increased number of pulmonary ailments in
Calgary hospitals during both Chinook Types. In an
exhaustive clinical study in Calgary’s Headache
Research Unit, Cooke et al. (2000) measured theprobability of migraine under Chinook and non
Chinook weather. The following paragraph quotes
directly from their paper. Note that pre-Chinook are
the same as Chinook Type 1. Chinook is Chinook
Type 2.
“The probability of migraine onset wasincreased on both pre-Chinook (Chinook Type 1)days (odds ratio 1.24; 95% CI 1.08 to 1.42) and ondays with Chinook winds (Chinook Type 2) (1.19;
1.02 to 1.39) compared with non Chinook days.
Analysis of Chinook wind velocities revealed thatfor Chinook days, the relative risk of migraine
onset was increased only on high-wind Chinookdays (velocity > 38 km/h) (odds ratio 1.41; 95% CI
1.06 to 1.88). A subset of individuals was sensitive
to high-wind Chinook days, and another subset
was only sensitive to pre-Chinook days. Only twopatients were sensitive to both weather conditions,and the majority of patients was not sensitive toeither. Neither weather condition had a protective
effect. Increasing age was associated with highwind Chinook sensitivity (p = 0.009) but not preChinook sensitivity (p = 0.389). Conclusions: Both
pre-Chinook and high-wind Chinook days increase
the probability of migraine onset in a subset of
migraineurs.”
Earlier in this review the connections between
rapidly changing weather, especially the onset ofsudden and rapid warming, and serious illness inhuman was reviewed. It is not surprising that a rise in
hospital visits and phone calls to emergency centres in
Calgary correlate significantly with Chinook weather(Nkemdirim, 1993).
The role played by atmospheric ions in sense ofwell being is controversial. Ions are small particles
that take on an electrical charge. It is believed that innature, ions are generated in abundance whereverenergy is transferred into the air. Ultraviolet light fromthe sun, lightning and thunderstorms, and friction
within wind and rain enrich the air with ions. Whenenough energy acts upon a molecule such as carbon
dioxide, oxygen, water, or nitrogen to eject an electron,
the displaced electron attaches itself to a nearby
molecule, which then becomes a negative ion. In
nature we tend to find between a few hundred to a few
thousand of them per cubic centimeter (Sulman, 1980).
The small particles that take on this charge are either

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L. NKEMDIRIM

negatively charged, positively charged or neutral.
Atmospheric ions are not always in balance at alocation. Waterfalls and their immediate surroundings
and high mountains are negative ion rich while
positive ions dominate just before a thunderstorm.
Chinook type winds in both North America andEurope are also associated with an abundance of
positive ions (Sulman, 1980). Laboratory experiments
show that abnormally high concentration of negative
ion enhances oxygen intake (Bhartendu & Menon,
1978) accounting for the improved well being
experienced in mountain resorts and similar recreational environments. An abundance of positive ions isbelieved to have the opposite effect. Sulman (1980)
showed that the dry Sharav winds which are similar towarm mountain winds cause the types of illnesses
identified with the Chinook. Relationship between
serotonin and atmospheric ions has been used to explain Chinook-induced illness. Serotonin is a hormone
found in the brain, blood and digestive tracts. It acts asa chemical messenger that transmits signals between
nerve cells. It also causes blood vessels to widen or
narrow (Konig & Krueger, 1981; William, 1998).
While serotonin has been used in healing (William,1998), it has also been linked with poor health. While
studying positive ion victims of the hot, dry Sharav
winds in Jerusalem, Sulman demonstrated threeeffects of positive ion excess: irritation and tension,
exhaustion, and hyperthyroid response. Most of these
conditions, along with symptoms of depression,anxiety, headaches, and low-energy physical andmental functions, were shown to be alleviated or
totally eliminated by increasing the negative ion countin the air (Sulman, 1980). Cramer (1995) believes that
Sulman’s conclusions are applicable to Canada andCalifornia because of the Chinook and Santa Ana
respectively. However, extension of Sulman’s conclusion to North America awaits credible empiricalsupport.

8. Conclusion
Polls indicate that 92% of Canadians consult at
least one weather forecast each day. The same percentage said that the information is of some value totheir daily lives and is largely satisfied with access toweather information. At the beginning of the 20th century, weather related disasters numbered less than
20 per year. At the conclusion of that century, that
number had risen to 130. In 1998, Canada spent$3 billion to repair damage caused by high impact
weather. Future outlook on heavy weather is muchbleaker. Global warming, now underway, will causeeven more such weather. The need for improvement inability to predict severe weather with lead time superior to what we have today is imperative. Environment
Canada has identified areas of concern including air
pollution and health for future focus. They are building capacity among users and scientists to improveknowledge on weather-societal connections and optimize benefits.
The private meteorological sector in Canada is extremely small. However, it includes considerable
talent in universities, commercial units and Nongovernmental Organisations (NGO). It is within thisgroup that most progress in health-weather relationships is expected.
References
Ambury, S. (2005) On the economic value of probability of
precipitation forecasts in Canada. Science, 310: 248-249.
Bhartendu, S. and I. A. Menon (1978) Effects of atmosphericsmall negative ions on the oxygen consumption of mouse
liver cells. International Journal of Biometeorology, 22:
43-52.
Cooke, L. J., M. S. Rose and W. J. Becker (2003) Chinook
winds and migraine headache. Neurology, 54: 302-307.
Côté, J., S. Gravel, A. Méthot, A. Patoine, M. Roch and A.
Staniforth (1998) The operational CMC-MRB Global Environmental Multiscale (GEM) model: Part I – Design considerations and formulation. Mon. Wea. Rev., 126: 1373-1395.
Cramer, G. (1995) Advanced research on atmospheric ions andrespiratory problems. Journal of Alternative and Complementary Medicine, 1: 87-92.
Delorme J., G. Brunet, A. Plante, N. Gagnon, G. J. Boer, F. W.
Zwiers, S. J. Lambert, J. Sheng and H. Ritchie (2001)
Seasonal predictions based on two dynamical models. Atmos.
Ocean., 39: 485-501.
Environment Canada (2005) CMC seasonal forecast.
(http:// www.cccma.bc.ec.gc.ca/data/cmc/cmc.shtml)
EnviroZine (2001) Is the weather affecting your health? Issue
15, December 19, 2001.
Hicks, R.B. and T. Matthews (1979) Impact of Chinooks on
Calgary’s air quality: acoustic sounder observations inatmospheric stability. Wat. Air, Soil Poll. 11: 159-172.
Konig, H.L. and A.P. Krueger (1981) Topics in environmental
physiology in medicine. In: K.E. Schaefer, ed., The Biologic
effects of environmental electromagnetism, Springer-Verlag,
Inc. New York-Berlin-Heidelbeg.
McConnell, R., K. T. Berhane and F. Gilliland (2002) Asthma
in exercising children exposed to ozone: A cohort study.
Lancet, 359: 386-91.
McFarlane, N.A., G.J. Boer, J.-P. Blanchet and M. Lazare(1992) The Canadian Climate Centre second-generation
general circulation model and its equilibrium climate. J.
Climate, 5: 1013-1044.
Mintz, R., B.R. Young and W.Y. Svrcek (2003) Fuzzy logic
modelling of air pollution during Chinook winds. Air Pollution XI, Transaction: Ecology and the Environment, 66:
36-41.
Mjelde, J.W. and J.B. Penson (2000) Dynamic aspects of the
impact of the use of perfect climate forecasts in the Corn Belt
region. Journal of Applied Meteorology, 39: 67-79.
Nkemdirim, L.C. (1993) Do Chinooks cause illness, Biometeorology, Proceedings of the International Congress of Biometeorology, September 12-18, Calgary, Canada, 3: 540-554.
Nkemdirim, L.C. (1995) An estimate of horizontal heat transport during a Chinook, Journal of Applied Meteorology,
American Meteorological Society, 34: 2533-2542.
Nkemdirim, L.C. (1996) Canada’s Chinook belt, International
Journal of climatology, Royal Meteorological Society, 16:441-462.
Nkemdirim, L. C. (1997) On the frequency and sequencing of
Chinook events. Physical Geography, 12: 101-113.

Weather Forecasting for Health and Society in Canada
Nkemdirim, L.C. and D. Baines (1985) What Calgarians know
about the Chinook. Applied Climatology in Alberta, Environment Canada, 99: 39.
Nkemdirim L.C. and K. Leggat (1978) The effect of Chinook
weather on urban heat islands and air pollution. J. Wat., Air,
Soil Poll., 9: 53-76.
Nursall, A. S. and D. W. Phillips (1980) The effects of weather
on the frequency and severity of migraine headaches insouthwestern Ontario. Canadian Climate Centre Report 80-7,
unpublished manuscript, Environment Canada, 21.
Oard, M. J. (1993) A method for prediction Chinook winds eastof the Montana Rockies. Weather and Forecasting, 8:
166-180.
Ruby, R. H. and J. A. Brown (1976) The Chinook Indians:
Traders of the lower Columbia River, University ofOklahoma Press, ISBN 0806113251; 0806121076.
Shabbar, A. and A. G. Barnston (1996) Skill of seasonal climate

11

forecasts in Canada using canonical correlation analysis.
Mon. Wea. Rev., 124: 2370-2385.
Stoupel, E. and M. Shimshoni (1991) Hospital cardiovasculardeaths and total distribution of deaths in 180 patients withdifferent cosmic physical activity – a correlative study(1974-1988). Int. J. Biometeor., 35: 6-9.
Sulman, F.G (1980) The effect of air ionization, electric fields,
atmospherics and other electric phenomena on man andanimal. Charles C. Thomas, Bannerstone House.
Thurston G. D. and D. V. Bates (2003) Air Pollution as anunderappreciated cause of Asthma Symptoms, Journal of theAmerican Medical Association, 290: 1915-1917.
Williams, S. P. (1998) The serotonin transporter: a primarytarget for antidepressant drugs. J. Psychopharmacol, 12:
115-121.

(Received 18 January 2007, Accepted 5 March 2007)