Total Solar Eclipse of 1 August 2008
Weather Commentary on the Canadian Archipelago

Credit: Jay Anderson (NASA Eclipse Bulletin: Total Solar Eclipse of 2008 August 01)

 

On August 1, temperatures in the Canadian Arctic have just passed their annual peak. The polar ice pack is retreating rapidly under the onslaught of continuous daylight, headed for its minimum in mid-September. Over southern and central parts of the archipelago, snow cover has melted away from the land and at Alert, the world’s most northerly settlement, has declined to barely a centimeter in depth. It is not a snow-free world however, as all Arctic settlements along the eclipse track can experience snowstorms in July and August—storms that can drop as much as 20 cm of fresh snow. Cyclonic weather systems (lows) tend to frequent the lower latitudes of the Canadian islands, being more common along the north coast of the mainland near Cambridge Bay than farther north at Resolute, Grise Fiord, and Alert. The impact of these systems on cloudiness is rather muted as skies tend to be gray whether or not a cyclonic disturbance is in the vicinity. At Cambridge Bay, the frequency of days with heavy cloud (8–10 tenths) is 70% and at Resolute, 77%. A significant part of this cloudiness comes in the form of fog, which occurs across the archipelago with a frequency of between 20 and 30% in August. The low-level cloudiness and fog are a consequence of the cooling of summer air masses as they pass over the cold Arctic Ocean waters, and suggests that conditions inland record greater amounts of sunshine than those at the coast. Satellite images for the region, however, usually show that the cloud cover simply blots out the landscape according to the weather of the day. Nevertheless, there is probably a small reward in moving inland a few kilometers in order to maximize the climatological probability of sunshine. From a global perspective, cloud cover decreases southward, and so Cambridge Bay, close to where the eclipse begins, should be more inclined to a sunny day than any of the few stations farther north. This is seen quite dramatically in Figure 17, which shows the mean cloud cover along the central line as Total Solar Eclipse of 2008 August 01 measured from polar-orbiting and geostationary satellites. The eclipse track near Cambridge Bay has a mean cloudiness of slightly below 65% compared to values in the mid–and upper 70 s for Resolute and Alert. This Cambridge Bay advantage, however, has a meager reflection in the observations of cloudiness from the surface (Table 18). Hourly records of sunshine—probably the best indication of the prospects of seeing the eclipse—show only a small variation across the Canadian Arctic. At Alert and Cambridge Bay, the percent of possible sunshine is close to 33%; at Resolute, it is only 22% (Table 18). As all of these means are for the month of August, it seems sensible to take an average of July and August to arrive at a more representative value for eclipse day. After making this adjustment, the percent of possible sunshine rises to 40, 31, and 36% for Cambridge Bay, Resolute, and Alert, respectively. The low altitude of the Sun over the Canadian Arctic is attractive for those who want to escape the endemic cloudiness by viewing from an airplane. The high frequency of low cloud is an advantage here, as the cloud top is more likely to be accessible to small aircraft with a limited ceiling. The low cloudiness—particularly the frequency of fog—has a downside, however, as Arctic flight schedules are notorious for being interrupted, sometimes for days on end, by poor visibilities in fog or occasional snowstorms. No seasoned traveler would visit the Canadian archipelago without leaving a few days leeway for bad weather on either side of scheduled events. Once again, Cambridge Bay has all the advantage here: the August climatological record shows a frequency of 9.5 with visibility less than 1 km compared to more than 73 at Resolute.