Olga Zolina

Laboratoire de Glaciologie et Géophysique de l’Environnement Université Joseph Fourier, Grenoble, France

P.P.Shirsov Institute of Oceanology RAS, Moscow, Russia

Changes in continental water cycle and extreme events

Outline:

Hydroclimate extremes and extreme precipitation

Precipitation extremes: definitions, measures and data

requirements

Absolute extremes: impacts on hydroclimate

Precipitation timing: implications for hydroclimate extremes

Scaling of extreme precipitation: data and model issues

Impacts of extremes: summer 2010

H500 height 30.07.2010 – 10.08.2010

Polland, SE Germany, Czech Rep.

Central Russia

Pakistan

Convective precipitation

Stratiform precipitation

space scale & spatial resolution, kilometers 0.1 1 10 100 1000

0.01 0.01

0.1

1

10

100

tim

e s

ca

le &

te

mp

ora

l r

eso

luti

on

, h

ou

rs

Climate models

Reanalyses

Mesoscale models

Daily rain gauge data

HR (10-min to hourly station data)

50+ years

10-50 years

>1-10 years

Periods of availability

Radars

Reanalyses

Spatial data resolution

Convective precipitation

Space time scales and data availability

Satellites

Stratiform precipitation

0 10 20 30 40 50 60 70 80 90days

0

10

20

30

40

50

mm

/day

0

10

20

30

40

50

Absolute

extremes

Relative extremes

(extremeness)

Time-integrated

extremes

•Peaks over threshold •Indices •Percentiles of the theoretical PDFs

Contribution of the wettest

days to totals

Wet spell durations and associated intensities

Approaches for estimating precipitation extremes

Autumn, 2012

10

Absolute extremes Nenastnaja (altitude 1186m)

Distance between

stations is ~100km

Shira (altitude 468m)

Relative extremes:

Nenastnaja: 3 days, R95pTOT=12.7%

Shira: 0 days, R95pTOT=0%

95% for 1966-2012 =27.2 mm/day

95% for 1966-2012 =10.7 mm/day

4 days

total=7mm

intensity=1.7mm/day

Wet spells

12 days

total=85mm

intensity=7.1mm/day

Changes in precipitation total may not necessarily imply same changes in precipitation extremes

Trends in annual precipitation 1951-2010

CRU GHCN GPCC

IPCC, 2013

What is «more wet» in practice?

Higher precipitation total with no (or opposite) change in extremes

No (or downward) change in precipitation total with growing extremes

No change in precipitation totals and extremes with growing fraction of total due to extremes

No (or minor) change in precipitation total and extremes with more prolonged wet spells

Absolute precipitation extremes: observed changes in 95% percentile of precipitation

1951-2008

Zagreb

95th percentile

mean intensity

Changes in absolute extremes differ from those in totals

-

10

0

to

-7

-

7

to

-6

-

6

to

-5

-

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to

-4

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to

-2

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3

to

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to

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5

to

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6

to

7

7

to

1

00

30

40

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60

70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

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60

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70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

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70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

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70

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40

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60

70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

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70

<-7

-7 -

-6

-6 -

-5

-5 -

-4

-4 -

-3

-3 -

-22

- 33

- 44

- 5 5 - 6

6 - 7 >7

(a) (b)

(c) (d)

WPOct-Mar

WPApr-Sep

DPOct-Mar

DPApr-Sep

% per decade

significant at 95% level

Zolina et al. 2005, Geophys. Res. Lett.

winter

Bonn-Friesdorf

December 1994 January 1994 February 1994

December 1967 January 1967 February 1967

Total precipitation = 211 mm

Number of wet days = 50 days

Number of wet periods = 7

Number of dry periods = 8

Longest wet period = 37 days

What is precipitation timing?

Russian Far East August-September 2013

Altai June 2014

0

4

8

12

16

20

24

mm

/day

0

4

8

12

16

20

24

mm

/day

Total precipitation = 224.5 mm

Number of wet days = 27 days

Number of wet periods = 15

Number of dry periods = 16

Longest wet period = 4 days

Changes in the duration of European wet periods

normalized occurrence anomalies

Net effect of the number of wet days (Monte-Carlo simulation of the growing

number of wet days, % per decade)

1% 2% 3%

0.17±0.10 0.31±0.19 0.47±0.25

It is not the effect of changing number of wet days!

long

spells

short

spells

95% level statistical significance

negative

positive

Maximum real increasing in the number

of wet days is 2.6% per decade

Mean real increasing in the duration of

wet spells is 4% per decade

Zolina et al. 2010, GRL

Red is for positive Green is for negative

Where changes in the duration of wet spells and dry spells have the same sign?

October-March April-September

Beads with a fixed number of stones

Zolina et al. 2013, J. Climate

wet day

dry period

Hydroclimate extremes: scaling

The peak appearance of the disastrous floods is typically highly localized extreme precipitation acts locally in space and in time this what makes it different from heavy precipitation

“extreme” depends on the scale

Sochi, Russia 25 June 2015

More than 240 mm dropped within 24 hours 120 mm were falling within 2-hour period

27 km

9 km

1 km

Scaling of extreme precipitation: flooding in Krymsk, Russia

0.8

1.6

2.5

3.3

4.2

5.0

5.8

6.6

7.5

8.3

mm

/5 m

inu

tes

Hourly precipitation for 6 and 7 July 2012 WRF real time simulation

Domain configuration Gelendgik 6-7 July 2012

Scaling of extreme precipitation

20-year seasonal return values ECHAM5 1982-2010

mm/day spatial length scale (°lat/lon)

20-y

r re

turn

val

ues

(m

m/d

ay)

Northern Europe DJF T213 L31 JJA T31 L19 JJA

ECHAM5 T213 L31 JJA EOBS JJA

Volosciuk et al. 2015

mm/day

High resolution precipitation climatology and extreme precipitation over Germany

Task: Long-term homogenized gridded daily precipitation for Germany for 1931 – 2012 with resolutions from 0.1° to 0.5°

Control and preprocessing of 7000+ daily long-term records Different objective analysis methods (KR, LP, GKA and more) Estimation of all sources of errors and uncertainties

STAMMEX-KR (1950-2008)

STAMMEX-KR (1950-2000)

STAMMEX-GCA (1950-2008)

E-OBS (1950-2008)

99% precipitation, 1951-2010 0.25°

STAMMEX-KR (1950-2008)

STAMMEX-KR (1950-2000)

STAMMEX-GCA (1950-2008)

E-OBS (1950-2008)

East German flood, August 2002

Zolina et al., 2014 BAMS

Conclusions

Most of Central and Northern Europe becomes wetter over changing climate, however: Extremes may not necessarily follow tendencies in precipitation totals

Precipitation timing is critically important for understanding the nature of hydroclimate extremes Europe exhibits lengthening of both wet and dry spells due to regrouping of wet days and longer wet spells associated with more abundant rainfalls

To establish more truth in understanding changes in continental water cycle close look on precipitation scaling problem is important for what we need: (i) Seamless (across the scales) modelling efforts from mesoscales to climate scales (ii) New (at least regional) data sets resolving precipitation on minute to hourly scales in time and several kilometers in space

This is a challenge for national metoffices, because many of them operate such networks, but do not make them openly available, thus putting populations of their own nations on risk.

Conclusions

20 km

20 km

European Climate Assessment & Dataset

public data

non-public data

Global Precipitation Measurement (GPM)

Seasonality in extreme precipitation trends

10 20 30 40 50 60 70 80 90 100

P r e c i p i t a t i o n c l a s s e s ( % )

-5

-4

-3

-2

-1

0

1

2

3

4

5

L i n

e a r t r

e n d ( %

)

10 20 30 40 50 60 70 80 90 100

P r e c i p i t a t i o n c l a s s e s ( % )

-5

-4

-3

-2

-1

0

1

2

3

4

5

L i n

e a r

t r e n d ( %

)

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10

0

to

-7

-

7

to

-6

-

6

to

-5

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5

to

-4

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-2

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7

to

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-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

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-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

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-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

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70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

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70

<-7

-7 -

-6

-6 -

-5

-5 -

-4

-4 -

-3

-3 -

-22

- 33

- 44

- 5 5 - 6

6 - 7 >7

(a) (b)

(c) (d)

WPOct-Mar

WPApr-Sep

DPOct-Mar

DPApr-Sep

winter summer

Zolina et al. 2008, J. Geophys. Res.

winter summer

Germany: strong seasonality

% per decade

Linear trends in absolute extreme precipitation

1951-2008

-

10

0

to

-7

-

7

to

-6

-

6

to

-5

-

5

to

-4

-

4

to

-3

-

3

to

-2

2

to

3

3

to

4

4

to

5

5

to

6

6

to

7

7

to

1

00

30

40

50

60

70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

50

60

70

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40

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70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

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30

40

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70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

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60

70

30

40

50

60

70

-10 0 10 20 30 40 50 60

-10 0 10 20 30 40 50 60

30

40

50

60

70

<-7

-7 -

-6

-6 -

-5

-5 -

-4

-4 -

-3

-3 -

-22

- 33

- 44

- 5 5 - 6

6 - 7 >7

(a) (b)

(c) (d)

WPOct-Mar

WPApr-Sep

DPOct-Mar

DPApr-Sep

% per decade

winter

summer

2-D duration-intensity diagrams

All wet periods Extremes (95th percentile)

% per

decade

total precipitation for different wet periods

Wet spells became significantly longer and precipitation intensity during these periods is also increasing!