1 Les règles générales WWOSC 2014 16-21 August, Montréal, Canada Didier Ricard 1, Sylvie Malardel 2, Yann Seity 1 Julien Léger 1, Mirela Pietrisi 1. CNRM-GAME,

1

Les règles générales

WWOSC 2014

16-21 August, Montréal, Canada

Didier Ricard1, Sylvie Malardel2, Yann Seity1

Julien Léger1, Mirela Pietrisi

1. CNRM-GAME, METEO-France, Toulouse

2. ECMWF, Reading

Sensitivity of short-range forecasting with the AROME model to a modified semi-Lagrangian scheme and high resolution.

2

AROME (Seity et al., 2011): operational fine-scale NWP model used at METEO-France since 2008 In 2008: 2.5-km horizontal resolution, 41 vertical levels

Domain 1500 km * 1300 km (600*512 points)

Current version: 2.5-km horizontal resolution, 60 vertical levels

Domain 1875 km * 1800 km (750*720 pts)

In 2015: 1.3-km horizontal resolution, 90 vertical levels

Domain 1996 km * 1872 km (1536*1440 pts)

1 – Introduction

Next version: 1.3 km 90

3

Dynamics package:• Nonhydrostatic model based on a fully compressible system• Spectral model, A grid • Semi-Lagrangian scheme

Tri-linear interpolation for computation of trajectories (origin point) quasi-cubic interpolations for calculating advected variables at origin point

• Time scheme 2 Time Levels semi-implicit scheme with SETTLS option (operational version) ICI (iterative centred implicit) scheme (Predictor-corrector scheme)

• 4th order spectral diffusion and gridpoint SLHD on hydrometeors

Characteristics of the AROME model

Physics package:• one moment mixed-phase microphysical scheme: 5 hydrometeor classes • 1D Turbulence scheme: pronostic TKE equation with a diagnostic mixing length (Bougeault

Lacarrere, 1989)• Surface scheme: SURFEX (ISBA parametrisation, TEB scheme for urban tiles, ECUME for sea tiles)• Radiation scheme: ECMWF parameterization• EDMF Shallow convection scheme

1 – Introduction

4

Evaluation of the AROME model at convective scale for preparing the next operational version

Test of a modified SL scheme at 2.5-km horizontal grid spacing during several periods (in particular between 15 July - 15 September 2013)

Comparison between AROME forecasts at 1.3-km and 2.5-km horizontal resolutions during June-November 2012 for days with thunderstorms

1 – Introduction

5

Motivation

Evaluation on a 2-month period (15 July 2013 - 15 September 2013) including deep convection with important effects of divergence

• Bias for precipitation: too much precipitation

sometimes too strong outflows under convective cells (with a strong diffusion)• Convection:

small-scale processes dominated by divergent modes strong interaction between physics and dynamics excessive behaviour: lack of conservation of SL scheme is suspected

• Solution: more conservative SL schemes (CISL, finite volume …) complex to implement expensive for operational use

• Simpler alternative approach (proposed by S. Malardel): taking into account expansion/contraction of atmospheric parcels associated to each gridpoint small modifications of the SL interpolation weights as a function of deformation

2 – Test of a modified Semi-Lagrangian scheme

6

COMAD scheme (Malardel and Ricard, in review, QJ)


t+1

Departure or origin point

t

* Computation of the trajectories: no modification

O

7



t+1

t

dx

L


* Computation of the value of variables at the origin point modification of the SL interpolation weights

For example, with linear interpolations (2D and regular grid):

Original SL scheme:

• 2 linear zonal interpolations

VB = wx1 VB1 + wx2 VB2 with wx2 = /dx, wx1 = 1 - /dx

VC = wx1 VC1 + wx2 VC2 = 1 - wx2

dy

B1 B2

C2C1

O

8



t+1

t

dx

L




Original SL scheme:



VC = wx1 VC1 + wx2 VC2 = 1 - wx2

dy

B1 B2

C2C1

OB

C

9



t+1

t

dx

L




Original SL scheme:



VC = wx1 VC1 + wx2 VC2 = 1 - wx2

• 1 meridian linear interpolation

VO = wy1 VB + wy2 VC with wy1 = L / dy, wy2 = 1 - L /dy

dy

B1 B2

C2C1

OB

C

10



t+1

t

dx




COMAD scheme:


VB = w’x1 VB1 + w’x2 VB2 with wx2 = /dx, wx1 = 1 - /dx

VC = w’x1 VC1 + w’x2 VC2 = 1 - wx2


VO = w’y1 VB + w’y2 VC with wy1 = L / dy, wy2 = 1 - L /dy

dy

B1 B2

C2C1

O

B

C

w’x1 = x wx1 + 0.5 * (1- x) with x = (1 + U/ x * dt) deformation factor along x axis

w’x2 = x wx2 + 0.5 * (1- x)

w’y1 = y wy1 + 0.5 * (1- y) with y = (1 + U/ y * dt) deformation factor along y axis

w’y2 = y wy2 + 0.5 * (1- y)

L

11



t+1

t

B1 B2

C2C1

O


w’x2 = x wx2 + 0.5 * (1- x)


w’y2 = y wy2 + 0.5 * (1- y)

modified linear weights can also be used after for computing cubic weights

B0 B3

C3C0

A1 A2

D1 D2




COMAD scheme:



VC = w’x1 VC1 + w’x2 VC2 = 1 - wx2



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t+1

t

B1 B2

C2C1

O


w’x2 = x wx2 + 0.5 * (1- x)


w’y2 = y wy2 + 0.5 * (1- y)modified linear weights can also be used after for computing cubic weights

AROME uses quasi-cubic interpolations (2 linear, 3 cubic ones)

B0 B3

C3C0

A1 A2

D1 D2




COMAD scheme:



VC = w’x1 VC1 + w’x2 VC2 = 1 - wx2



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Example: 30 June 2012

24-h precipitation (mm) from 00 UTC - Wind vectors at 10 m (m/s), 00 UTC 1 July

Less precipitationLess intense wind ahead of precipitation area

COMADOPER SL

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3-h precipitation (mm) 15-18 UTC, Wind vectors at 10 m (m/s) 18 UTC 30 June

Less intense convective cells Less intense outflows

COMADOPER SL

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Less intense convective cells Less intense outflows

3-h precipitation (mm) 15-18 UTC, Wind vectors at 10 m (m/s) 18 UTC 30 June

COMADOPER SL

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Virtual potential temperature (K) - Wind vectors at 10 m (m/s), 18 UTC 30 June

Less intense convective cells Less intense cold pools

COMADOPER SL

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15 July - 15 September 2013

Mean 24-h precipitation over the forecast domain

Less precipitation amount

COMAD

OPER SL

18




Less precipitation amountVariation between 1 and –26 %

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24-h precipitation distribution for all gridpoints of the forecast domain

Smaller frequencies of moderate and heavy precipitation

COMAD

OPER SL

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Scores:15 July - 15 September 2013

6-h precipitation: better scoresSurface pressure: slight improvement for bias

6-h precipitation (mm)

Surface pressure (hPa)

Forecast range (hour)


bias

mse

bias

mse

COMAD

OPER SL

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Scores:15 July - 15 September 2013

Near-surface wind and temperature: slight degradation after 18h forecast



2m temperature (K)

10m Wind intensity (m/s)

bias

mse

bias

mse

COMAD

OPER SL

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Fuzzy scores: 15 July - 15 September 2013

Brier Skill Scores for 24-h precipitation (06UTC-06UTC) Better scores for all thresholds and all neighbourhoods

RR24 > 0.2mm RR24 > 5 mm

RR24 > 10 mm RR24 > 20mm

Neighbourhood (km) Neighbourhood (km)


COMAD

OPER SL

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Brier Skill Scores for 6-h precipitation (12UTC-18UTC) Better scores for all thresholds and all neighbourhoods

RR6 > 0.5 mm RR6 > 2 mm

RR6 > 5 mm RR6 > 10mm



COMAD

OPER SL

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Running variance (100 km * 100 km) of wind at 10 m (m/s)², 18 UTC 30 June

Less intense convective cells Less intense downdrafts

COMADOPER SL

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15 July -15 September 2013

Running variance (100 km * 100 km)

(hourly averaged over the forecast domain and the period 15 July - 15 September 2013)

Less variance during the afternoon and eveningLess intense density currents under convective cells

10-m Wind (m²/s²)

10-m downdrafts (m²/s²)

925 hPa Virtual potential temperature (K²)

COMAD

OPER SL

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15 July -15 September 2013

Diurnal cycle of surface covered by convective cells (simulated reflectivities above 30 dBZ)

Less intense convective cells

COMAD

OPER SL

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3 – Evaluation of AROME at kilometric resolution

Methodology

Smaller forecast domain

(720 points *720 points - 1.3km) (360 points *360 points - 2.5km)

Configuration:• for stability: ICI scheme (instead of 2TL SI scheme)• time step: 45s (instead of 60s)• initial conditions: dynamical adaptation from 2.5km 3DVAR Analysis• LBC: from operational AROME• better representation of the orography at 1.3km

Experiments Horizontal grid spacing Vertical levels

2.5km60 2.5 km 60 (21 levels < 2000m)

2.5km90 2.5 km 90 (33 levels < 2000m)1.3km90 1.3 km 90 (33 levels < 2000m)

1.3km90BC 1.3 km 90 (41 levels < 2000m)

Layer thickness (m)

L 60

L 90

L 90BC

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Methodology

Period: 1 June-30 November 2012

Selection of days with moderate and intense convective activity over the forecast domain lightning data (more than 5000 strikes per day)

48 days

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

JuneJuly

AugustSeptember

OctoberNovember

24-h lightning data (21 June) : 88897 lightning strikes

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Scores

• Increase of vertical resolution: better classic scores (temp and humidity) but no better fuzzy scores

2m Temperature

2mHumidity

10m Wind

24-h precipitation

6-h precipitation

1-h Downdraft

Brightnesstemperature

2.5km90 vs 2.5km60 + + - = - - +

1.3km90 vs 2.5km90 - - + + + + +

1.3km90 vs 2.5km60 = - + + + + +

1.3km90BC vs 2.5km60 = - + + + + +

Classic scores (bias, MSE) Fuzzy scores (Brier Skill scores)

30


Scores


• Increase of horizontal resolution: better fuzzy scores degradation for temperature and humidity scores but improvement for wind score

2m Temperature

2mHumidity

10m Wind

24-h precipitation

6-h precipitation

1-h Downdraft


2.5km90 vs 2.5km60 + + - = - - +

1.3km90 vs 2.5km90 - - + + + + +

1.3km90 vs 2.5km60 = - + + + + +

1.3km90BC vs 2.5km60 = - + + + + +


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Scores


• Increase of horizontal resolution: better fuzzy scores degradation for temperature and humidity scores but improvement for wind score

• No further improvement with more levels below 2000m

2m Temperature

2mHumidity

10m Wind

24-h precipitation

6-h precipitation

1-h Downdraft


2.5km90 vs 2.5km60 + + - = - - +

1.3km90 vs 2.5km90 - - + + + + +

1.3km90 vs 2.5km60 = - + + + + +

1.3km90BC vs 2.5km60 = - + + + + +


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Characteristics of convective cells

Comparison to observations using a tracking algorithm (Morel et al., 2002) to detect convective cells (2 thresholds > 30 dBZ and > 40 dBZ) size, number, intensity maximum of convective cells

Simulated reflectivities at 1500 m 21 June 12UTC

2.5km: 76 cells > 40 dBZ

5dbZ

10

15

20

30

50

40

33

5dbZ

10

15

20

30

50

40




2.5km: 76 cells > 40 dBZ


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2.5km: 76 cells > 40 dBZ 1.3km: 122 cells > 40 dBZ

5dbZ

10

15

20

30

50

40


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Characteristics of convective cells > 40 dBZ - 21 June

1.3 km vs 2.5km:o more cellso more numerous small cellso fewer large cells o more realistic

Time evolution of cell number Surface distribution

radar

1.3kmradar

1.3km

2.5km2.5km

36


Characteristics of convective cells > 30dBZ and > 40 dBZ - 48 days

Over the 48 days at the peak of convection, 1.3 km vs 2.5km:o more realistico more numerous small and medium cells o fewer large cells

Surface distribution > 30dBZ Surface distribution > 40dBZ

radar

1.3km

2.5km

radar

1.3km

2.5km

37

Conclusion

• Increase of horizontal grid spacing (1.3km versus 2.5km): more realistic number of cells more numerous small cells, fewer large cells reduction of precipitation amount better fuzzy scores (for precipitation, brightness temperature, downdrafts …)

• Use of the modified SL scheme (COMAD versus original SL scheme) less intense convective cells improvement of QPF, less amount better fuzzy scores for precipitation test on other periods: June 2012, January 2013 (frontal precipitation)

Test of the modified SL scheme at 1.3km

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Brier Skill Scores for brightness temperature 10.8 m (forecast range 18 UTC)

For peak of convection: better scores in particular for lower temperature thresholds better representation of the high clouds

Neighbourhood 20 km

Temperature thresholds (K)

Neighbourhood 52 km


COMAD

OPER SL

40


1-31 January 2013


Less impact on frontal precipitation

COMAD

OPER SL

41


1-31 January 2013


Less impact on frontal precipitationVariation between 1 and –5 %

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Fuzzy scores: 1-31 January 2013

Brier Skill Scores for 24-h precipitation (06UTC-06UTC)

RR24 > 0.2mm RR24 > 5 mm

RR24 > 10 mm RR24 > 20mm



COMAD

OPER SL

43


1-30 June 2012


Less precipitation amount

OPER

MODIFSL

44


1-30 June 2012


Less precipitation amountReduction between –1 and –25 %

45


1-30 June 2012

24-h precipitation distribution for all gridpoints of the forecast domain

Smaller frequencies of moderate and heavy precipitation

COMAD

OPER SL

46


Fuzzy scores: 1-30 June 2012

Brier Skill Scores for 24-h precipitation (forecast range 30h) Better scores for all thresholds and all neighbourhoods

OPER

MODIFSLRR24 > 0.2mm RR24 > 1 mm

RR24 > 10 mm RR24 > 20mm



47


Fuzzy scores: 1-30 June 2012

Brier Skill Scores for brightness temperature 10.8 m (forecast range 18 UTC)

For peak of convection: better scores in particular for lower temperature thresholds better representation of the high clouds

OPER

MODIFSLNeighbourhood 20 km


Neighbourhood 120 km


48



Running variance (100 km * 100 km) of wind at 10 m (m/s)², 18 UTC 30 June


COMADOPER SL

49



Running variance (100 km * 100 km) of downdrafts at 10 m (m/s)², 18 UTC 30 June


COMADOPER SL

50



Running variance (100 km * 100 km) of 925 hPa ϴv at 10 m (K)², 18 UTC 30 June


COMADOPER SL

51


Characteristics of convective cells > 40 dbZ - 21 June

Time step impact:o 30s: slightly more cells, in particular small cellso 60s: slightly less cells in particular small cells


52


Characteristics of convective cells > 40 dbZ - 21 June

Diffusion impact:o Without spectral diffusion: sightly more cellso Spectral diffusion constant on vertical: weak impact o Without SLHD: more cells


1 Les règles générales WWOSC 2014 16-21 August, Montréal, Canada Didier Ricard 1, Sylvie Malardel 2, Yann Seity 1 Julien Léger 1, Mirela Pietrisi 1. CNRM-GAME,

Documents

surface scheme

teb scheme

modified sl scheme

comad scheme malardel

d turbulence scheme

phase microphysical

origin point time scheme

sea tiles radiation