alexander walther

Regional Climate Group 1http://rc

g.gvc.gu.se

Department of Earth Sciences

http://rcg.gvc.gu.se/


g.gvc.gu.se


Alexander WaltherPhysical GeographerPh.D. studentclimatology

Acknowl. supervisors:Prof. Deliang Chen, Hans Linderholm



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Research topics

Climate extremes (Temperature and

precipitation) in past/present/future

links to atmospheric circulation

the role played by anthropogenic

forcings

Sweden and Europe



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Observations ...

- precipitation- temperatures- daily- hourly- point

measurements with some spatial autocorrelation

... and models- precipitation- temperatures- ...- daily, hourly, 10-

min?- grid averages



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Diurnal variation in precipitation amount and frequency in SwedenCurrent work

Precipitation data in a mountainous catchment in Honduras: quality assessment and spatiotemporal characteristicsWesterberg et al. (accepted)

Thermal Growing Season (GSL)Walther & Linderholm (2006), Linderholm et al. (2008), Song et al. (2009)

Trend Atlas of EMULATE extremesChen et al. (2006)http://rcg.gvc.gu.se/data

http://rcg.gvc.gu.se/data



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Diurnal variation in precipitation amount and frequency in Sweden



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observationsmodel



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Spatial scale of extreme precipitation



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GCM 44km 22km

min # of stations

Prec

1 5 1 5 1 5

40mm 0 0 21 81 55 100

25mm 1 5 27 90 70 98

10mm 7 14 56 91 85 99.9

5mm 22 34 74 97 93 100

2mm 45 58 86 99 96 100

Cases [%] where

interpolated rainfall

matches observed

rainfall



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Twentieth-century trends in the thermal growing season in the Greater Baltic Area

1901-1950 (=5>5F)

0o 10oE 20oE 30oE 40oE 50oE 52oN

56oN

60oN

64oN

68oN

72oN 1951-2000 (=5>5F)


56oN

60oN

64oN

68oN

72oN 1901-2000 (=5>5F)


56oN

60oN

64oN

68oN

72oN

1901-1950 (10d<5)


56oN

60oN

64oN

68oN

72oN 1951-2000 (10d<5)


56oN

60oN

64oN

68oN

72oN 1901-2000 (10d<5)


56oN

60oN

64oN

68oN

72oN

1901-1950 (=5>5Fr|10d)


56oN

60oN

64oN

68oN

72oN 1951-2000 (=5>5Fr|10d)


56oN

60oN

64oN

68oN

72oN 1901-2000 (=5>5Fr|10d)


56oN

60oN

64oN

68oN

72oN

Start

End

Length

GBA Average(1951-2000)

-6.3 days

+1.1 days

+7.4 days



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Trend atlas of the EMULATE indices (Chen et al., 2006)

http://rcg.gvc.gu.se




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TminTmax

Tmin/Tmax indices. Fraction of positive, positive significant, negative, and negative significant trends for 1901-2000. The areas showing the highest fractions for each index and season are colored.

pos pos* neg neg* pos pos* neg neg* pos pos* neg neg* pos pos* neg neg*MEANTN 84.2 61.4 15.8 1.8 91.2 68.4 8.8 3.5 93.0 66.7 7.0 0.0 87.7 35.1 12.3 0.0MEANTX 91.2 50.9 8.8 3.5 87.7 56.1 12.3 3.5 93.0 66.7 7.0 3.5 96.5 49.1 3.5 0.0TN2P 78.9 22.8 21.1 0.0 68.4 31.6 31.6 7.0 77.2 24.6 22.8 0.0 75.4 26.3 24.6 1.8TN5P 75.4 22.8 24.6 0.0 71.9 43.9 28.1 7.0 86.0 26.3 14.0 0.0 71.9 26.3 28.1 1.8TN10P 77.2 29.8 22.8 0.0 82.5 50.9 17.5 7.0 93.0 35.1 7.0 0.0 75.4 26.3 24.6 0.0TN90P 77.2 31.6 22.8 3.5 93.0 63.2 7.0 0.0 87.7 45.6 12.3 0.0 98.2 42.1 1.8 0.0TN95P 66.7 19.3 33.3 10.5 91.2 61.4 8.8 0.0 86.0 40.4 14.0 0.0 96.5 47.4 3.5 0.0TN98P 63.2 14.0 36.8 12.3 87.7 54.4 12.3 0.0 80.7 36.8 19.3 1.8 96.5 54.4 3.5 0.0TX2P 93.0 26.3 7.0 0.0 70.2 24.6 29.8 7.0 98.2 22.8 1.8 0.0 78.9 12.3 21.1 0.0TX5P 93.0 28.1 7.0 0.0 64.9 33.3 35.1 7.0 94.7 26.3 5.3 0.0 91.2 19.3 8.8 0.0TX10P 91.2 26.3 8.8 0.0 70.2 33.3 29.8 3.5 94.7 33.3 5.3 0.0 89.5 19.3 10.5 0.0TX90P 61.4 35.1 38.6 5.3 86.0 50.9 14.0 3.5 82.5 33.3 17.5 3.5 94.7 68.4 5.3 0.0TX95P 63.2 22.8 36.8 3.5 84.2 42.1 15.8 5.3 66.7 21.1 33.3 3.5 96.5 80.7 3.5 0.0TX98P 54.4 15.8 45.6 7.0 84.2 40.4 15.8 5.3 68.4 24.6 31.6 7.0 94.7 80.7 5.3 0.0TN2N 17.5 3.5 82.5 38.6 26.3 7.0 73.7 40.4 21.1 1.8 78.9 42.1 31.6 0.0 68.4 8.8TN5N 21.1 3.5 78.9 45.6 19.3 7.0 80.7 47.4 17.5 3.5 82.5 43.9 28.1 0.0 71.9 19.3TN10N 19.3 5.3 80.7 43.9 15.8 7.0 84.2 50.9 15.8 1.8 84.2 49.1 29.8 0.0 70.2 21.1TN90N 86.0 64.9 14.0 0.0 91.2 59.6 8.8 0.0 93.0 70.2 7.0 0.0 94.7 54.4 5.3 0.0TN95N 86.0 59.6 14.0 0.0 96.5 59.6 3.5 0.0 89.5 64.9 10.5 0.0 96.5 64.9 3.5 0.0TN98N 87.7 54.4 12.3 1.8 94.7 54.4 5.3 0.0 86.0 52.6 14.0 0.0 94.7 68.4 5.3 0.0TX2N 8.8 0.0 91.2 38.6 14.0 3.5 86.0 38.6 3.5 0.0 96.5 49.1 24.6 0.0 75.4 10.5TX5N 14.0 0.0 86.0 43.9 19.3 3.5 80.7 42.1 3.5 0.0 96.5 64.9 26.3 0.0 73.7 17.5TX10N 15.8 1.8 84.2 49.1 22.8 3.5 77.2 45.6 1.8 0.0 98.2 71.9 29.8 0.0 70.2 19.3TX90N 87.7 50.9 12.3 3.5 84.2 52.6 15.8 5.3 89.5 50.9 10.5 5.3 98.2 84.2 1.8 0.0TX95N 86.0 50.9 14.0 3.5 84.2 45.6 15.8 3.5 84.2 45.6 15.8 5.3 98.2 84.2 1.8 0.0TX98N 86.0 43.9 14.0 3.5 84.2 40.4 15.8 3.5 82.5 35.1 17.5 7.0 96.5 82.5 3.5 0.0HWDI 84.2 22.8 15.8 0.0 73.7 21.1 26.3 3.5 64.9 5.3 28.1 3.5 89.5 36.8 5.3 0.0WSDI90 82.5 24.6 17.5 0.0 75.4 24.6 24.6 3.5 73.7 14.0 26.3 3.5 96.5 49.1 3.5 0.0CSDI10 19.3 0.0 80.7 22.8 28.1 0.0 71.9 19.3 17.5 0.0 82.5 35.1 29.8 0.0 70.2 7.0FD 15.8 0.0 84.2 52.6 15.8 0.0 84.2 52.6 15.8 0.0 84.2 52.6 15.8 0.0 84.2 52.6

JJA SON DJF

Tm

in/T

max

MAM

+ - + - + - + -

perc

entil

esco

ldw

arm

cold

war

mco

ld



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Prec indices: Fraction of positive, positive significant, negative, and negative significant trends for 1901-2000. The areas showing the highest fractions for each index and season are colored.

pos pos* neg neg* pos pos* neg neg* pos pos* neg neg* pos pos* neg neg*PRECTOT 68.0 14.0 32.0 3.0 48.0 6.0 52.0 3.0 67.0 21.0 33.0 3.0 78.0 27.0 22.0 2.0PREC90P 65.0 7.0 35.0 4.0 50.0 5.0 50.0 4.0 68.0 19.0 32.0 1.0 76.0 26.0 24.0 4.0PREC95P 74.0 15.0 26.0 1.0 56.0 8.0 44.0 4.0 72.0 20.0 28.0 3.0 79.0 27.0 21.0 1.0PREC98P 80.0 7.0 20.0 2.0 60.0 9.0 40.0 4.0 66.0 19.0 34.0 3.0 72.0 20.0 28.0 2.0R90N 65.0 13.0 35.0 3.0 57.0 6.0 43.0 3.0 67.0 19.0 33.0 1.0 77.0 22.0 23.0 3.0R90T 68.0 11.0 32.0 1.0 68.0 12.0 32.0 2.0 68.0 21.0 32.0 2.0 70.0 28.0 30.0 3.0R90AM 71.0 15.0 29.0 3.0 55.0 9.0 45.0 3.0 68.0 22.0 32.0 3.0 78.0 33.0 22.0 3.0R95N 71.0 15.0 29.0 4.0 64.0 7.0 36.0 3.0 71.0 21.0 29.0 6.0 75.0 22.0 25.0 2.0R95T 72.0 10.0 28.0 0.0 68.0 14.0 32.0 2.0 66.0 15.0 34.0 3.0 73.0 19.0 27.0 2.0R95AM 74.0 14.0 26.0 2.0 62.0 11.0 38.0 3.0 70.0 22.0 30.0 5.0 77.0 31.0 23.0 2.0R98N 72.0 11.0 28.0 2.0 59.0 13.0 41.0 1.0 65.0 22.0 35.0 2.0 77.0 18.0 23.0 1.0R98T 75.0 5.0 25.0 1.0 67.0 14.0 33.0 1.0 68.0 18.0 32.0 1.0 71.0 17.0 29.0 4.0R98AM 72.0 10.0 28.0 2.0 61.0 12.0 39.0 3.0 68.0 21.0 32.0 4.0 79.0 21.0 21.0 2.0SDII90p 70.0 6.0 30.0 0.0 61.0 14.0 39.0 2.0 60.0 14.0 40.0 2.0 73.0 15.0 27.0 0.0SDII95p 63.0 6.0 37.0 1.0 57.0 10.0 43.0 0.0 66.0 8.0 34.0 1.0 70.0 7.0 30.0 2.0SDII98p 56.0 8.0 44.0 0.0 58.0 11.0 42.0 1.0 66.0 12.0 34.0 1.0 66.0 19.0 34.0 0.0SDII 77.0 19.0 23.0 3.0 63.0 14.0 37.0 4.0 66.0 24.0 34.0 5.0 77.0 38.0 23.0 2.0R5d 70.0 10.0 30.0 3.0 67.0 11.0 33.0 1.0 67.0 20.0 33.0 2.0 79.0 20.0 21.0 2.0R1d 65.0 11.0 35.0 0.0 59.0 8.0 41.0 0.0 67.0 13.0 33.0 1.0 73.0 21.0 27.0 3.0CDD 58.0 5.0 42.0 1.0 71.0 1.0 29.0 1.0 57.0 1.0 43.0 3.0 48.0 0.0 52.0 2.0

JJA SON DJF

pre

cip

ita

tio

n

MAM+ - + - + - + -



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Ongoing and planned

• atmospheric circulation mechanisms behind extreme precipitation events

• When does it rain and why• How will precipitation patterns (extremes,

diurnal cycle) evolve in the future• Do anthropogenic forcing plays a role



g.gvc.gu.se


Research topics

Climate extremes (Temperature and

precipitation) in past/present/future

links to atmospheric circulation

the role played by anthropogenic

forcings

Sweden and Europe



g.gvc.gu.se



alexander walther

Documents

rainfallregional climate

daysregional climate

swedenregional climate

sedataregional climate

europe regional climate

negative significant

fraction of positive

indices chen