Surface Climate and SnowWeather Relationships of the Kuparuk Basin
15
In contrast to the uplands, late WS into early EC is typically the cloudiest
time of year on the coast, and it is at this time that BET sees its smallest diurnal
variation in temperature. It is curious to note that by the end of EC, BET has the
highest diurnal range of all sites. The brief warming trend seen in almost all
locations starting in late October is another interesting feature in an otherwise
monotonically decreasing temperature trend at all sites. (This will be considered
further in the discussion section.) It is also noteworthy that the period from the
last week of September through about the third week of October is when tem-
peratures are most homogeneous over the network.
IMN is the first of the sites to reaching sub-freezing minimum temperatures,
this occurring in the last third of August. By the first week in September all sites
are experiencing below-freezing temperatures, and by the end of September tem-
peratures at all sites typically remain below 0C throughout the day. Table 3
contains date statistics for freezes (≤ 0, 3, 6C for at least six consecutive
hours) for each of the sites, based on a frost-free period starting on 15 July. (The
notion of a truly "frost-free season" in the traditional midlatitude sense is some-
what nebulous here, given that temperatures on the Arctic Slope occasionally dip
below freezing for short periods throughout WS. Hence, the six-hour time crite-
rion and negative threshold temperatures give a more realistic measure of "sig-
nificant frosts.") Higher-elevation IMN is the outlying site in this measure, with
mean dates typically preceding the other sites by about two weeks. The two sites
closest to marine modifying influences, BET and FRA, are the latest in each
category. These date trends have a significant impact on the date that snow cover
begins to form.
Table 3. Mean, earliest, and latest dates at each site for the occurrence of temperatures less
than 0, 3.0, and 6.0C lasting for at least six consecutive hours.
≤ 0C for 6 hours
3C for 6 hours
6C for 6 hours
Mean
Early
Late
Mean
Early
Late
Mean
Early
Late
BET
08/25
07/28
09/19
09/18
09/04
10/03
10/02
09/16
10/13
FRA
08/28
08/10
09/12
09/12
08/21
09/30
09/29
09/13
10/10
IMN
08/09
07/25
08/21
08/24
08/10
09/11
09/05
08/22
09/22
SAG
08/21
07/29
09/27
09/08
08/11
09/29
09/20
08/23
10/05
WKU
08/22
08/10
09/06
09/05
08/21
09/22
09/22
09/15
10/04
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