10th International Congress of the Hellenic Geographical Society, Thessaloniki 23 October 2014

A high resolution regional climate simulation for Greece for the period 1960-2100:

Evaluation and future projections

Prodromos ZanisDepartment of Meteorology and Climatology,

School of Geology, AUTH

Acknowledgments to my co-authors:

Katragkou E., Ntogras C., Feidas H.Department of Meteorology and Climatology, School of Geology, AUTH

Marougianni G, Melas D.Laboratory of Atmospheric Physics, Physics Department, AUTH

Anadranistakis E.Hellenic National Meteorological Service

The work was carried out in the framework of the GEOCLIMA project (http://www.geoclima.eu/)

through the Operational Program “Competitiveness and Entrepreneurship” of the National Strategic Reference Framework (NSRF) – Research Funding Program

COOPERATION 2009.

Climate modeling

• Coupled AOGCMs are the most advanced tools today available for climate simulation

• The resolution of present day AOGCMs (100 – 300 km) is still too coarse to provide fine scale regional climate information useful for impact studies

Regional Climate Modeling:Technique and Strategy

• Technique: A “Regional Climate Model” (RCM) is “nested” within a GCM in order to increase the resolution of a climate simulation.– Initial conditions (IC) and

lateral boundary conditions (LBC) for the RCM are obtained from the GCM.

• Strategy: The GCM is used to simulate the response of the general circulation to large scale forcings, while the RCM is used to simulate the effect of sub-GCM-grid scale forcings and to provide fine scale regional information– The RCM is intended to only

enhance the GCM information• Technique inherited from NWP

Mean precipitation climatology 1961-1990

Obs GGDBObs CRU

50 km RCM 200 km GCM11 km RCM(Tselioudis et al., Int. J. Clim., 2011)

Crete

Peloponnese

Rhodes

Thrace

Macedonia

Aegeansea

Ioniansea

Thessaly

Epirus

Pindus mountains

CentralGreece

Model domainGrid resolution 10 km x 10 kmsimulation period1960-2100

Lateral boundary conditions: RegCM3 (25 km x 25 km) forced by ECHAM5 under A1B IPCC scenario (4.5 TB).Use of the GRID-HELLAS platform

a) b)

c) d)

18 20 22 24 26 28 30

34

36

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Temp - HNMS stations

lon

lat

6

8

10

12

14

16

18

20

18 20 22 24 26 28 303

43

63

84

04

2

Temp - ECHAM 1.9 x 1.9 deg

lon

lat

6

8

10

12

14

16

18

20

e)

Mean annual near-surface temperature (1975-2000) for a) HNMS stations, b) E-obs, c) RCM10, d) RCM25 and e) the forcing GCM ECHAM5

18 20 22 24 26 28 30

34

36

38

40

42

Prec- RegCM 25x25 km

lon

lat

0

500

1000

1500

2000

18 20 22 24 26 28 30

34

36

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42

Prec - RegCM 10x10 km

lon

lat

0

500

1000

1500

2000

a) b)

c) d)

18 20 22 24 26 28 30

34

36

38

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42

Prec- E-obs 0.22 x 0.22 deg

lon

lat

0

500

1000

1500

2000

18 20 22 24 26 28 30

34

36

38

40

42

Prec- HNMS stations

lon

lat

0

500

1000

1500

2000

18 20 22 24 26 28 30

34

36

38

40

42

Prec - ECHAM 1.9 x 1.9 deg

lon

lat

0

500

1000

1500

2000e)

Annual precipitation sum (1975-2000) for a) HNMS stations, b) E-obs, c) RCM10, d) RCM25 and e) the forcing GCM ECHAM5

a) b)

c) d)

Mean annual bias in near surface temperature (0C) and precipitation (mm) over the period 1975-2000 for RCM10 (a and c) and for RCM25 (b and d)

a) b)

c) d)

e) f)

Change between 2021-2050 and 1961-1990

as well as between 2071-2100 and 1961-1990 for the annual mean (a and b),

maximum (c and d) and minimum (e and f)

near-surface temperature (0C) based on the

RCM10 simulation

a)

b)

c)

d)

Annual precipitation change in (%) and in (mm/day) between 2021-2050 and 1961-1990 (a and c) as well as between 2071-2100 and 1961-1990 (b and d) based on the RCM10 simulation

a) b)

c) d)

Seasonal mean near surface temperature change (0C) between 2071-2100 and1961-1990 for a) winter, b) spring, c) summer and d) autumn

based on the RCM10 simulation

a) b)

c) d)

Seasonal mean precipitation change (mm/day) between 2071-2100 and1961-1990 for a) winter, b) spring, c) summer and d) autumn

based on the RCM10 simulation

Indices 2

a) b)

c) d)

e) f)

Annual change between 2021-2050 and 1961-1990 as

well as between 2071-2100 and 1961-1990 for the number of hot days with Tmax>35 oC (a and b),

for the number of warm days with Tmin>20 oC (c and d),

as well as the number of night frost days

with Tmin<0 oC (e and f) based on the RCM10

simulation

a) b)

c) d)

Annual change between 2021-2050 and 1961-1990 as well as between 2071-2100 and 1961-1990

for dry spell days (a and b) and the growing season days (c and d)

based on the RCM10 simulation

Key points - conclusions• A transient high resolution (10 km x 10 km) simulation (RCM10) was carried out with

RegCM3 over the period 1960-2100 that constitutes a climate simulation, for the first to our knowledge, with such a high resolution for Greece.

• A station-based evaluation showed that the mean annual bias in near surface temperature is reduced in RCM10 compared to RCM25 and the bias in annual precipitation is also reduced over mountain regions.

• In the early future period (2021-2050), annual temperature increases mostly over land by less than 1.8οC and precipitation change ranges between ±15%, being mostly negative in the southern part of the domain.

• At the end of the century (2071-2100), the mean annual temperature increases by about 3.4 οC to 4.2 οC over land and by 2.6 οC to 3.4 οC over the sea while precipitation decrease by 10% to 40% with a positive gradient from the north to the south.

• Summer presents the largest future increase in mean near surface temperature over the Greek mainland while winter and spring show the largest decreases in precipitation rate.

• The number of hot days, warm nights, night frost days length of the growing season and continuous dry spell days are projected to increase slightly in the near future period but largely and consistently in the late 21st century future period in accordance with the generally warmer and drier climate projected from the RCM10 simulation for Greece.

Thanks

for your attention