Geography Reference
In-Depth Information
3
Atlas of the Trend Analysis
In this chapter, the results of the trend analysis for each
index, station or region are presented in the form of maps and
time-series plots. The maps, however, are only used for the
most recent period (1901-2000) due to the limited number of
stations in earlier periods. For each period, seasonal indices
starting with spring (MAM) and ending with winter (DJF)
are presented. The order of presentation is Tmin/Tmax, fol-
lowed by Tmean and Precipitation (see Table 2.2). To make
it easier to ind an index in a given season and for a given
period, a header is put on each page to indicate the period,
season, and index group. The circles in the maps indicate
station locations for the two longer periods where results
for individual stations are presented. All the maps contain a
colour bar symmetric around zero and a title (Fig.
3.1
). The
range is determined by the highest absolute value appear-
ing in the map. An index dependent general colour scheme
is used throughout the whole atlas. For temperature indices,
the colour scale ranges blue-green-red where red colours
indicate warming and blue colours cooling conditions. For
example, an increase in Tmean would be shown in red as
well as a decreased number of days below the second per-
centile. Trends in precipitation indices are visualized using
a brown-yellow-green colour scale where brownish colour
indicate drier and greenish colours wetter conditions. Trend
signiicance is indicated for each symbol marking a station
(circles) or regional averages (squares) using signiicance
levels of
p
< 0.05 and
p
< 0.01. Analysis period, season, index
and the unit of the trend are provided in every igure title.
For the time-series plots, each individual station's data
are separately shown for the two longer periods (1801-2000
and 1851-2000), while the regional means are displayed
for the period 1901-2000 on background plots containing
all contributing individual station time series (in light grey
lines). Each figure shows annual values of an index for a sea-
son, its low-frequency variation and long-term linear trend
(Fig.
3.2
). The smoothed curve emphasizing low-frequency
variation is a 10-year Gaussian filter applied to the original
time-series suppressing variations on time-scales less than 10
years. The straight solid line shows the linear trend estimated
by linear regression for the period in question. The statistical
trend significance is indicated as follows: '*' significant at
p
< 0.05, '**' significant at
p
< 0.01, and '()' not significant.
In each figure analysis period, the names of stations or re-
gion, season, index name and trend unit are indicated. To
save space, two (and sometimes three) indices or two trend
lines for two periods are plotted in the same figure whenever
appropriate and feasible (Figs.
3.3
,
3.4
,
3.5
,
3.6
,
3.7
,
3.8
,
3.9
,
3.10
,
3.11
,
3.12
,
3.13
,
3.14
,
3.15
,
3.16
,
3.17
,
3.18
,
3.19
,
3.20
,
3.21
,
3.22
,
3.23
,
3.24
,
3.25
,
3.26
,
3.27
,
3.28
,
3.29
,
3.30
,
3.31
,
3.32
,
3.33
,
3.34
,
3.35
,
3.36
,
3.37
,
3.38
,
3.39
,
3.40
,
3.41
,
3.42
,
3.43
,
3.44
,
3.45
,
3.46
,
3.47
,
3.48
,
3.49
,
3.50
,
3.51
,
3.52
,
3.53
,
3.54
,
3.55
,
3.56
,
3.57
,
3.58
,
3.59
,
3.60
,
3.61
,
3.62
,
3.63
,
3.64
,
3.65
,
3.66
,
3.67
,
3.68
,
3.69
,
3.70
,
3.71
,
3.72
,
3.73
,
3.74
,
3.75
,
3.76
,
3.77
,
3.78
,
3.79
,
3.80
,
3.81
,
3.82
,
3.83
,
3.84
,
3.85
,
3.86
,
3.87
,
3.88
,
3.89
,
3.90
,
3.91
,
3.92
,
3.93
,
3.94
,
3.95
,
3.96
,
3.97
,
3.98
,
3.99
,
3.100
,
3.101
,
3.102
,
3.103
,
3.104
,
3.105
,
3.106
,
3.107
,
3.108
,
3.109
,
3.110
,
3.111
,
3.112
,
3.113
,
3.114
,
3.115
,
3.116
,
3.117
,
3.118
,
3.119
,
3.120
,
3.121
,
3.122
,
3.123
,
3.124
,
3.125
,
3.126
,
3.127
,
3.128
,
3.129
,
3.130
,
3.131
,
3.132
,
3.133
,
3.134
,
3.135
,
3.136
,
3.137
,
3.138
,
3.139
,
3.140
,
3.141
,
3.142
,
3.143
,
3.144
,
3.145
,
3.146
,
3.147
,
3.148
,
3.149
,
3.150
,
3.151
,
3.152
,
3.153
,
3.154
,
3.155
,
3.156
).
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