Mid-Term Science and Technology Meeting RESEARCH ...€¦ · MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Coastal ABL Features over Thiruvananthapuram Diurnal/Seasonal Evolution

Mid-Term Science and Technology Meeting

RESEARCH HIGHLIGHTS

AND MAJOR ACCOMPLISHMENTS

D. BALA SUBRAHAMANYAM

NUMERICAL ATMOSPHERE MODELLING (NAM) BRANCH

SPACE PHYSICS LABORATORY, VIKRAM SARABHAI SPACE CENTRE

THIRUVANANTHAPURAM - 695 022

URL: http://SPL.gov.in/

D. Bala Subrahamanyam (NAM) Mid-Term Science and Technology Meeting 22 - 29 March 2016 1 / 23

MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Why do we bother too much about this Parametrization ?

Why do we bother too much about Parametrization ???

Generally, the physical and atmospheric processes which happen to be sub-grid in

nature, require parametrization as they can not be solved directly !!!


MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Evolution in the Model Topography

Evolution in the Model Topography in the last 2 decades


















COSMO Topography: From Past to Present

⇒

NEED OF THE HOUR:

We need to review and look back at the sub-grid scale processes and their treatment in

the Regional Atmospheric Models.


MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Parametrization of Different Physical Processes

Parametrization of Different Physical Processes

A Schematic on different processes being parametrized in NWP Models


MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Parametrization of the ABL Processes

Criticalities involved in the treatment of ABL Processes

Impact of Convective Thermals on the ABL Structure




Transition of the Laminar Flow to a Turbulent Flow




Important Unknowns in the ABL Characterization



Parametrization of ABL Processes based on K-theory

Assumption : Analogy between turbulent and molecular transfer

Flux is proportional to the local gradient

F = −K ∂A∂z

K is eddy diffusivity/viscosity;

similar to molecular viscosity

Based on the estimation of K, COSMO model offers

two distinct approaches for parametrization of ABL processes:

(1) MYD, Diagnostic approach

(2) MYTKE, Turbulent Kinetic Energy (TKE) based Prognostic approach



ABL Parametrization Schemes in the COSMO Model

MYD

1-D Diagnostic

Closure

=⇒

MYTKE

1-D TKE-based

Diagnostic Closure

⇐=


MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Refinement in COSMO ABL Parametrization Scheme

Refinement in COSMO ABL Parametrization Scheme

A New MYlnew Approach in the ABL Parametrization

In the new approach, instead of treating the l (master length scale) merely as a function of altitude, it is

taken to be dependent on three different length scales (Nakanishi, 2001; Suselj, 2010):

1

l=

1

ls+

1

lb+

1

l∞.

where ls, lb and l∞ represent the surface length scale, buoyancy suppression length scale and an

asymptotic length scale respectively. The ls in the above expression is given as:

κ.z.(1 + 2.7ζ)−1 , ζ > 0

ls = κ.z , ζ = 0

κ.z.(1 − 100.ζ)0.2 , ζ < 0

whereas, lb is expressed as:

α2.q/N ,∂θv∂z

> 0; ζ ≥ 0

lb = (α2.q + α3.q.√

q0l∞

.N)/N ,∂θv∂z

> 0; ζ < 0

∞ ,∂θv∂z

≤ 0


MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Study domain & Details of Numerical experiments

Study domain & Details of Numerical experiments

Numerical Experiments

MYD : Default scheme

MYlnew : modified l

MYTKE : Default TKE based scheme

Model Run Configuration

Horizontal resolution : 0.0625°

Longitudinal Coverage : 74.5°E to 79.5°E

Latitudinal Coverage : 6.0°N to 11.0°N

Database

Observation : Pisharoty GPS Sondes

: ( 3 hourly interval)

Period of study : February 2011-2013

[ Anurose and Subrahamanyam, Mod. Earth. Sys. Env., 2015 ]



Vertical Profiles of Eddy Diffusivity Coefficients

COSMO Model simulations of Km and Kh for 10-Feb-2011

(a-b): daytime

⇐=

⇐=

(c-d): nocturnal



Vertical Profiles of Meteorological Parameters

COSMO Model simulations of vertical profiles for 10-Feb-2011



Vertical Profiles of Meteorological Parameters

Vertical profiles of RMSE for the entire databaseAltitude (m)

0100200300400500600700800900

1,000

θRMSE (οC)

0 1 2 3 4

a

MYD

MYTKE

MYlnew

0100200300400500600700800900

1,000

WSRMSE (m s-1)

0 1 2 3 4 5 6

b

0100200300400500600700800900

1,000

RHRMSE (%)

10 15 20 25 30

c

Altitude (m)

0100200300400500600700800900

1,000

θRMSE (οC)

0 1 2 3 4

d

0100200300400500600700800900

1,000

WSRMSE (m s-1)

0 1 2 3 4 5 6

e

0100200300400500600700800900

1,000

RHRMSE (%)

10 15 20 25 30

f



Diurnal Variability in ABL Heights

COSMO Simulations: Diurnal Variability in ABL Heights

Why does the ABL heights sharply fall down after 1130 LT in the observational data,

whereas none of the parametrization schemes are able to simulate such a deep fall ???



Diurnal Variability in ABL Heights

COSMO Simulations: Diurnal Variability in ABL Heights

Why does the ABL heights sharply fall down after 1130 LT in the observational data,

whereas none of the parametrization schemes are able to simulate such a deep fall ???


MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Coastal ABL Features over Thiruvananthapuram

Sea-breeze & Coastal-breeze Components over TVM

Surface Elevation (m) map around Thiruvananthapuram



Coastal ABL and Sea-breeze Circulation

Schematic of the daytime Coastal ABL and Sea-breeze Circulation



Diurnal Variations in the SBC over

Thiruvananthapuram

Seasonal Pattern in the Diurnal Evolution of SBC over

Thiruvananthapuram



Rainfall Climatology over Thiruvananthapuram

Rainfall Climatology over Thiruvananthapuram

(Data Source: http://www.imd.gov.in/)



Diurnal/Seasonal Evolution of Coastal ABL Structure

Variations in the Sea-breeze Flow Thickness (SBFT)




Variations in the ABL Heights




Variations in the inferred LCL Heights




Variations in the Sea-breeze Flow Thickness

(a) sea-breeze flow thickness (m) [2011]

0 3 6 9 12 15 18 21 24

Local Time

0

2

4

6

8

10

12

Mo

nth

-400-200 0 200 400 600 800 1000 1200 1400 1600 1800 2000

(b) sea-breeze flow thickness (m) [2012]

0 3 6 9 12 15 18 21 24

Local Time

0

2

4

6

8

10

12

Mo

nth

-400-200 0 200 400 600 800 1000 1200 1400 1600 1800 2000

(c) zABL (m) in 2011

0 3 6 9 12 15 18 21 24

Local Time

0

2

4

6

8

10

12

Mo

nth

0

150

300

450

600

750

900

1050

1200

(d) zABL (m) in 2012

0 3 6 9 12 15 18 21 24

Local Time

0

2

4

6

8

10

12

Mo

nth

0

150

300

450

600

750

900

1050

1200

(e) zLCL (m) in 2011

0 3 6 9 12 15 18 21 24

Local Time

0

2

4

6

8

10

12

Mo

nth

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

(f) zLCL (m) in 2012

0 3 6 9 12 15 18 21 24

Local Time

0

2

4

6

8

10

12

Mo

nth

0

250

500

750

1000

1250

1500

1750

2000

2250

2500



Diurnal Evolution of Coastal ABL Structure

Inter-relation between zABL, zLCL, q and TT


Documents

Mid-Term Science and Technology Meeting RESEARCH ...€¦ · MID-TERM SCIENCE & TECHNOLOGY MEETING (MARCH 2016) Coastal ABL Features over Thiruvananthapuram Diurnal/Seasonal Evolution