(2)
Labelled Samples
A subset of ADHs were manually labelled with flow regime types. The
determination of flow regime type was based on visual assessment to the
shape of ADHs, which is subjective to some degree. 2480 ADHs were
labelled that represent seven distinctive flow regimes in the WNA domain
(Fig. 2). ADHs selected for the same type typically come from streams
that are geographically clustered. Class 1 is characterized by frequent
rain events during winter and low flows in summer, with streams mostly
located in coastal Pacific North West (PNW). Class 2 is similar to Class
1, but has a distinct snowmelt-driven spring freshet, and are mainly
located in the interior PNW. Class 3 has extremely low winter flows,
large spring freshet and many summer rain events. All of Class 3 gauges
are located in Alaska. Class 4 exhibits a large spring freshet followed
by summer storm events with gauges located in the Northwest Territories
and northern Alberta. Class 5 is similar to Class 4, with later summer
rain events and gauges are located in Yukon and northern British
Columbia. Class 6 is characterized by dominant snowmelt freshet in
spring that accounts for more than 70% of the annual discharge with
gauges primarily located Canadian Rockies between British Columbia and
Alberta. Class 7 has a spring freshet along with occasional winter
events and gauges are most often located in Idaho. The labelled ADHs
were used to evaluate the performance of t-SNE, with details provided in
later sections.
Figure 2: Normalized ADHs for the seven flow regimes. The number in the
parenthesis indicates the number of ADHs in that class.
t-distribution Stochastic Neighbor Embedding
(t-SNE)
t-distribution Stochastic Neighbor Embedding (t-SNE, van der Maaten and
Hinton (2008)) is a state-of-theart technique for dimensionality
reduction and high-dimensional data visualization. It is a variant of
the SNE that was originally proposed by Hinton and Roweis (2002). SNE
represents similarity between datapoints using conditional probabilities
that are converted from pairwise Euclidean distances (Eq. 3).