Atmospheric Boundary Layer evening transitions: a comparison between two

experimental sites (CIBA-Spain and BLLAST-France)

M. Sastre (1), C. Yagüe (1), C. Román-Cascón (1), G. Maqueda (2).

(1) Dept. Geofísica y Meteorología. University Complutense of Madrid, Spain. (msastrem@fis.ucm.es)(2) Dept. Astrofísica y Ciencias de la Atmósfera. University Complutense of Madrid, Spain.

12th EMS Annual Meeting &9th European Conference on Applied Climatology

(ECAC)

EUROPEAN METEOROLOGICAL SOCIETY

11th September 2012

Contents1.- Introduction

2.- Methodology

3.- Experimental data

4.- WRF model

5.- Results

6.- Summary and conclusions

1.- Introduction

• Evening transition processes in the ABL: from convection to stability

• Comparison at two experimental sites

• Simulations: differences between sites?

2.- Methodology

• Data from two experimental sites: CIBA site (Spain) and the BLLAST campaign site (France). x

x

2.- Methodology

1

P

BLLAST campaign site: land-use

Forestpines

moor

cropsForestdeciduous

village

industrial

town

meadow

cornmeadow

2.- Methodology

• Data from two experimental sites: CIBA site (Spain) and the BLLAST campaign site (France).

• Days studied from two summer periods: 2009 (CIBA) and 2011 (BLLAST).

• Times related to sunset for every site and day (t=0 => tsunset).

• Simulations using WRF model.

• MRFD technique employed.

xx

3.- Experimental data

• Sonic anemometer (CIBA and BLLAST)• BLLAST 60m-tower instruments (2, 15, 30, 45, 60 m)• CIBA 10m-mast instruments (1.5, 3, 5, 7.5, 10 m)

4/12)'w'v(2)'w'u(

*U

Focus on:

• Wind speed and direction

• Temperature

• Turbulent parameters

Friction velocity:

4.- WRF model

Initial and boundary conditions from NCEP-NCAR (1º resolution; data every 6 hours).

4 nested domains whose grids are: 27, 9, 3 and 1km.

Time step: 81 seconds. 50 eta vertical levels. Spin up: 12 h. SW radiation: Dudhia (1998). LW radiation RRTM. Microphysics package: WSM3.

• Weather Research and Forecast (WRF) mesoscale model.• Test three PBL parameterizations: MYJ, MYNN, QNSE.

• More about model configuration:

5.- Results• Days selected: 28-29-30 August 2009 (CIBA) and 24-25-26 June

2011 (BLLAST).• Similar synoptic situations: stability and weak pressure gradient.

30/August/2009 – 00:00 UTCGeopotential at 500 hPa (gpdm) and surface pressure reduced to sea level

(reanalysis taken from: www.wetterzentrale.de)

5.- ResultsComparison of MRFD

Friction velocity (U*)

time (h)

Tim

esca

le (

s)

U*

-2 -1 0 1 2 3 410

-1

100

101

102

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

-2 -1 0 1 2 3 410

-1

100

101

102

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

time (h)

Tim

esca

le (

s)

-2 -1 0 1 2 3 410

-1

100

101

102

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

29 Aug 2009 (CIBA) 24 Jun 2011 (BLLAST)

time (h)

Tim

esca

le (

s)

U*

-2 -1 0 1 2 3 410

-1

100

101

102

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

m s-1

t=0 => tsunset

5.- ResultsComparison of MRFD

Friction velocity (U*)

time (h)

Tim

esca

le (

s)

U*

-2 -1 0 1 2 3 410

-1

100

101

102

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

-2 -1 0 1 2 3 410

-1

100

101

102

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

time (h)

Tim

esca

le (

s)

-2 -1 0 1 2 3 410

-1

100

101

102

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

29 Aug 2009 (CIBA) 24 Jun 2011 (BLLAST)

time (h)

Tim

esca

le (

s)

U*

-2 -1 0 1 2 3 410

-1

100

101

102

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

m s-1

t=0 => tsunset

5.- ResultsComparison of temperature and friction velocity

U*T

-2 -1 0 1 2 3 410

15

20

25

30

35

time (h)

Tem

pera

ture

(ºC

)

-2 -1 0 1 2 3 40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

time (h)

U* (

m s

-1)

29 Aug 2009

24 Jun 2011

26 Jun 2011

-2 -1 0 1 2 3 40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

time (h)

U* (

m s

-1)

29 Aug 2009

24 Jun 2011

26 Jun 2011

CIBABLLAST

5.- ResultsKatabatic event - CIBA

-6 -4 -2 0 2 4 6 8 0

50

100

150

200

250

300

350

time (h)

Win

d D

irect

ion

(º)

2009/8/30

1.5m

10m

-6 -4 -2 0 2 4 6 8 0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

time (h)

Hor

izon

tal W

ind

Spe

ed (

m s

-1)

2009/8/30

1.5m

10m

wind speed wind direction

-6 -4 -2 0 2 4 6 8

10-2

10-1

100

time (h)

U*

(m s

-1)

2011/06/26-27

MYJ

MYNN

QNSE

obs.

-6 -4 -2 0 2 4 6 810

-2

10-1

100

time (h)

U*

(m s

-1)

2011/06/26-27

MYJ

MYNN

QNSE

obs.

5.- ResultsWRF simulations

Friction velocity(U*)

26 Jun 2011

-6 -4 -2 0 2 4 6 8 0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

time (h)

U*

(m s

-1)

2009/08/28-29

MYJ

MYNN

QNSE

obs.

28 Aug 2009

-6 -4 -2 0 2 4 6 8 10

-2

10-1

100

time (h)

U*

(m s

-1)

MYJ

MYNNQNSE

obs.30 Aug 2009

CIBA

BLLAST

-6 -4 -2 0 2 4 6 810

-2

10-1

100

time (h)

U*

(m s

-1)

2011/06/24-25

MYJ

MYNNQNSE

obs.

24 Jun 2011

-6 -4 -2 0 2 4 6 810

-2

10-1

100

time (h)

U*

(m s

-1)

2011/06/24-25

MYJ

MYNNQNSE

obs.

5.- ResultsWRF simulations

Temperature

-6 -4 -2 0 2 4 6 817

18

19

20

21

22

23

24

25

26

time (h)

Tem

pera

ture

(ºC

)

obs.

MYJMYNN

QNSE

25 Jun 2011 (BLLAST)

-6 -4 -2 0 2 4 6 8 14

16

18

20

22

24

26

28

30

32

time (h)

Tem

pera

ture

(ºC

)

MYJ

MYNNQNSE

obs.

30 Aug 2009 (CIBA)

5.- ResultsWRF simulations

Wind speed

-6 -4 -2 0 2 4 6 8

1

2

3

4

5

6

7

time (h)

Hor

izon

tal W

ind

Spe

ed (

m s

-1)

obs.

MYJMYNN

QNSE

26 Jun 2011 (BLLAST)

-6 -4 -2 0 2 4 6 8 4

5

6

7

8

9

10

11

time (h)

Hor

izon

tal w

ind

spee

d (m

s-1

)

MYJ

MYNNQNSE

obs.

28 Aug 2009 (CIBA)

6.- Summary and conclusions

Evening transition processes have been evaluated at two different experimental sites.

MRFD timescales: similar evolution, but with some differences.

Radiative cooling: seems to be influenced by soil moisture.

Simulations: tend to overestimate the turbulence after sunset at one of the sites (the less dried).

THANK YOUTHANK YOUFOR YOUR FOR YOUR ATTENTIONATTENTION

Acknowledgements: Spanish Ministry of Science and Innovation projects CGL2006-12474-C03-03, CGL2009-

12797-C03-03 and CGL2011-13477-E . UCM fellowship (reference BE45/10). BLLAST project, especially M. Lothon and F. Saïd for the 60m-tower data. EMS Young Scientist Travel Award (YSTA).