Transcript SMHI (part I)

Hydrological response surfaces in the
Nordic Region for use in probabilistic
assessment of climate change
Phil Graham
Sara-Sofia Hellström
Fredrik Wetterhall
Swedish Meteorological and
Hydrological Institute, Norrköping
Our contribution to workpackage
objectives
• Hydrological rainfall-runoff models to
investigate impacts of climate change on
stream discharge
• Using the climate change signal from RCMs
Our contribution to workpackage
objectives
• Response surfaces for selected applications
• Direct use of multiple regional model
projections
• Comparison of outcomes from the two
methods
What have we achieved since Lund?
• In Lund, we showed some preliminary
response surfaces
• Now, we have produced many more
• In Lund, we discussed the question of
seasonality
• Now, we have investigated the details of
representing seasonality
Response Surfaces – Annual Runoff
Lake Vänern
no seasonality
Lake Vänern
Response Surfaces – Annual Runoff
Lake Vänern
with seasonality
Lake Vänern
RS – Representing Seasonality
Method 1
10
2
8
1.8
7
1.6
Precipitation change
Temperature change
9
6
5
4
1.4
1.2
3
1
2
0.8
1
0.6
0
2
4
6
Month
8
Temperature
10
12
2
4
6
Month
8
Precipitation
10
12
RS - Extended Period with Maximum
Lake Vänern
Discharge
Current regulation rules
RS - Extended Period with Maximum
Lake Vänern
Discharge
Current regulation rules
Lake Vänern
RS - Extended Period with Maximum
Discharge with Modified Regulation
Modified regulation can help reduce
risk of high discharge
Lake Vänern
Response Surfaces – Monthly Runoff
Lake Vänern
Response Surfaces – Annual Runoff
Lake Mälaren
Response Surfaces – Annual Runoff
seasonality 1
Lake Mälaren
Response Surfaces – Annual Runoff
seasonality 2
Lake Mälaren
RS – Representing Seasonality
Method 2
Precipitation change type 2
2
2
1.8
1.8
1.6
1.6
%-change precipitation
%-change precipitation
Precipitation change type 1
1.4
1.2
1
1.4
1.2
1
0.8
0.8
0.6
0.6
2
4
6
Month
8
Precipitation
method 1
10
12
2
4
6
Month
8
Precipitation
method 2
10
12
RS – Lake Levels
Lake Mälaren
Low levels
RS – Lake Levels, seasonality 1
Lake Mälaren
Low levels
RS – Lake Levels, seasonality 2
Lake Mälaren
Low levels
Response Surfaces – Monthly Runoff
Lake Mälaren
Monthly Runoff – compared to
previous results
400
400
Lake Mälaren
350
350
300
300
ctrl
RCAO-EA2
runoff (m3/s)
250
250
RCAO-EB2
RCAO-HA2
200
200
RCAO-HB2
RCAO-EA2-rs
150
150
RCAO-EB2-rs
RCAO-HA2-rs
100
100
50
50
0
0
1
2
3
4
5
6
7
month
8
9
10
11
12
RCAO-HB2-rs
Some Conclusions
• Seasonal differences not so apparent for
annual runoff
• Shows up in monthly results, and even more
for thresholds, although not all basins are
equally sensitive
• Different methods for representing
seasonality have an impact
• Representation of evapotranspiration is
problematic (as usual!)
Coming Work
• Contribution to del. 6.7 (RS Report)
• Not too much more on response surfaces
before data starts coming
• Next major effort will be to work with
direct modelling of RCM simulations
(the “Matrix,” as soon as they are available)
Questions for Discussion
• Critical thresholds, we use experience from
critical past events, better ideas?
• What if there is widely differing seasonality
from the climate models?
• What will we actually get from the climate
models
(i.e. probabilistic info.)?
• How many simulations will be available
(perturbed vs. RCM results)?