C. Spyrou, G. Kallos and N. Bartsotas

Modelling the regional characteristics of desert

dust sources

UNIVERSITY OF ATHENS FACULTY OF PHYSICS, DIVISION OF ENVIRONMENTAL PHYSICS - METEOROLOGY

ATMOSPHERIC MODELING AND WEATHER FORECASTING GROUP

http://forecast.uoa.gr

7th International Workshop on Sand/Duststorms and Associated Dustfall, Frascati (Rome), Italy, 2-4 December 2013

The presence of desert dust in the atmosphere has considerable

impacts

The impacts are ranging from modification of the radiative forcing

to cloud formation and precipitation

Therefore, perturbations in dust particle production can have

impacts on radiative properties, cloud formation and water budget

These feedbacks depend on the physical, chemical and optical

characteristics of mineral particles which in turn are defined by the

characteristics of the different source areas

Due to the importance of these phenomena the accurate

description of dust sources and production is essential

MOTIVATION

This presentation focuses on defining the areas acting as dust sources

More specifically:

A new surface characterization database has been developed for use in

regional and global atmospheric models

The dataset was implemented into SKIRON/Dust atmospheric model

Evaluation based on actual measurements

OBJECTIVES

INPUT DATASETS

Soil texture database: 16

category hybrid STATSGO/FAO

30″

Vegetation database: 24

category U.S. Geological

Survey 30″

INPUT DATASETS

Clay Content database : (%) clay with resolution 0.08°

SLOPE CUTOFF Slope gradients that exceeded a specific threshold are characterised as

areas with reduced dust uptake characteristics

Threshold was set at 5 degrees slope

Areas that met this rule were downgraded in the classification

SLOPE CUTOFF Slope gradients that exceeded a specific threshold are characterised as

areas with reduced dust uptake characteristics

Threshold was set at 5 degrees slope

Areas that met this rule were downgraded in the classification

• #1: Vegetation “desert” and soil is either “sand” or “loamy sand”

• #2: Vegetation “desert” and soil is “sandy loam”

• #3: Vegetation “desert” and soil is “loam”

• #4: Vegetation “semi-desert” and soil is either “sand” or “loamy sand”

• #5: Vegetation “semi-desert” and soil is “sandy loam”

• #6: Vegetation “semi-desert” and soil is “loam”

• #0: All other combinations.

• High clay amounts reduce the category by 1

• Topographic Slopes greater than 5 degrees produce no dust

NEW CLASSIFICATION CRITERIA

NEW CLASSIFICATION

North Africa

NEW CLASSIFICATION

Arabian Peninsula

NEW CLASSIFICATION

Some Features of SKIRON/Dust Model

Eight-size particle bin scheme (Zender et al. 2003; Spyrou et al., 2010)

Dust source identification and flux production by utilizing additional soil classes and properties (rocky soil, clay amounts) (Reynolds et al., 1999, Spyrou et al., 2010)

Updated dry and wet deposition schemes (Slinn and Slinn, 1980; Kumar et al., 1996; Pandis, 1998)

In-cloud scavenging (Pandis, 1998)

Utilization of high resolution SST (Spyrou et al., 2010)

Incorporation of the RRTMG radiative transfer scheme for SW and LW radiation (Iacono et al., 2008, Clough et al., 2005, Mlawer et al., 1997)

Aerosol – Radiation feedback (Spyrou et al., 2013)

New desert dust classification categories

Sensitivity Tests – Model Setup

• Simulation for 3 months March-April-May 2010 using original dust classification (control)

• Simulation for 3 months March-April-May 2010 using new dust classification (new)

• Evaluation using AERONET data

SKIRON/Dust

Input Data

Initial and boundary

conditions (ECMWF

analysis 0.5x0.5)

Topography (30΄΄x30΄΄) –

USGS. Vegetation

(30΄΄x30΄΄) – USGS. Soil

Texture (30΄΄x30΄΄)

FAO/UNESCO.

Horizontal

Resolution 0.15o x 0.15o

Vertical Levels 38 (up to 22Km)

Timestep 60 sec

Radiation

Algorithm RRTMG

SKIRON computational domain

Sensitivity Tests – AERONET data

Data Selection criteria based on Astitha et al., 2012

• AOD 550 > 0.2

• Angstrom exponent (AE 500 − 870 nm) < 1.2

Test Case 16-18 April 2010

Test Case 16-18 April 2010

Dust particles recorded at Lampedusa

Strong winds at 850 hPa transport

dust particles towards Central and

Eastern Mediterranean on the 15th

of April 2010

Test Case 16-18 April 2010

Dust Flux – Control Dust Flux – New

Test Case 16-18 April 2010

Lampedusa

0

0.2

0.4

0.6

0.8

1

1.2

4/15/2010

12:00

4/16/2010

0:00

4/16/2010

12:00

4/17/2010

0:00

4/17/2010

12:00

4/18/2010

0:00

4/18/2010

12:00

4/19/2010

0:00

4/19/2010

12:00

Date

AO

D 5

50

Data Ctrl New

Test Case 16-18 April 2010

Lampedusa

0

0.2

0.4

0.6

0.8

1

1.2

4/15/2010

12:00

4/16/2010

0:00

4/16/2010

12:00

4/17/2010

0:00

4/17/2010

12:00

4/18/2010

0:00

4/18/2010

12:00

4/19/2010

0:00

4/19/2010

12:00

Date

AO

D 5

50

Data Ctrl New

Better agreement between

actual AOD data and the

updated SKIRON model

Further testing with all 4

stations the entire

simulation period is

needed

Simulations March – April – May 2010

April 2010

Athens - April 2010 - AOD 550

y = 0.6539x + 0.0037

R2 = 0.7857

y = 0.8986x + 0.0032

R2 = 0.8183

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Model

AE

RO

NE

T

New Control Linear (Control) Linear (New)

- Control New

BIAS 0.085 -0.029

RMSE 0.228 0.166

Corr 0.886 0.904

FORTH_CRETE - April 2010 - AOD 550

y = 0.9347x + 0.0038

R2 = 0.8078

y = 0.7062x + 0.0044

R2 = 0.7186

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Model

AE

RO

NE

T

New Control Linear (New) Linear (Control)

- Control New

BIAS 0.061 -0.040

RMSE 0.219 0.196

Corr 0.886 0.847

March 2010 – May 2010

- Control New

BIAS 0.138 -0.015

RMSE 0.425 0.383

Corr 0.844 0.881

- Control New

BIAS -0.134 -0.064

RMSE 0.215 0.205

Corr 0.820 0.828

Lampedusa - March - May 2010 - AOD 550

y = 0.931x + 0.0036

R2 = 0.7762

y = 0.6854x + 0.0038

R2 = 0.7135

0.1

0.3

0.5

0.7

0.9

1.1

1.3

1.5

1.7

1.9

0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9

Model

AE

RO

NE

T

New Control Linear (New) Linear (Control)

Rome - March - May 2010 - AOD 550

y = 1.0724x + 0.0015

R2 = 0.6859

y = 0.8842x + 0.0014

R2 = 0.6738

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Model

AE

RO

NE

T

New Control Linear (New) Linear (Control)

Some Concluding Remarks

• Desert uptake is defined by the source characteristics

• Vegetation, soil texture and clay content are the most important aspects of

dust productive areas

• Steep sloped areas reduce dust production

• A new dataset was created to address these factors on a global scale

• By implementing all the above in a new dataset the model was able to

accurately describe dust production

• The physical, chemical and optical characteristics of dust originate from the

source. Therefore it is important to address these issues in the future as well

The presence of dust particles create significant perturbations in the weather and

climate. Therefore it is essential to accurately describe the desert dust cycle: