Download pdf - Uncertainty Analysis of Thunderstorm Nowcasts for ... · 20120715 observation is always larger than nowcast in direction right 17.14 km P 90,abs,60min 18.24 km 1.98 km P 90,abs,60min

Uncertainty Analysis of Thunderstorm Nowcasts

for Utilization in Aircraft Routing

1

Manuela Sauer1, Thomas Hauf1, Caroline Forster2

1Leibniz Universität Hannover, Institute of Meteorology and Climatology 2DLR, Institute of Physics of the Atmosphere

25. November 2014 – 4th SESAR Innovation Days

Uncertainty Analysis of Thunderstorm Nowcasts for Utilization in Aircraft Routing

Manuela Sauer et al. 4th SESAR Innovation Days, Madrid 2

Outline

• Thunderstorms, motivation and nowcast data used

• Methodology and results of the uncertainty analysis

• Application in weather avoidance routing



Thunderstorms

• Small scale phenomena

– cell diameter: 5 - 50 km

– life time: 20 - 60 min

• After generation: further life cycle and movement

is in principal predictable

• Prediction of onset?

– generation mechanisms need to be forecasted:

• deterministic components: orography, surface convergence lines

• stochastic components: gravity waves, temperature inhomogeneities

not predictable!

UNCERTAINTY

Source: http://www.bom.gov.au/storm_spotters/handbook/thunderstorms.shtml



Motivation

event

approaching an event in

time and space

lead time

probability



Rad-TRAM nowcast system Radar Tracking and Monitoring

• Based on radar composit

with timely resolution of

5 minutes

• object-based (> 37 dBZ)

• Pyramidal image matcher

displacement

life cycle: growth and decay

of cells

Source: http://www.pa.op.dlr.de/MUCSOMMER/2012/

Further information:

Tafferner, A., C. Forster, 2012: Weather Nowcasting and Short

Term Forecasting, in Atmospheric Physics,

U. Schumann (ed.), Springer Verlag



Rad-TRAM nowcasts

time

lea

d tim

e

t0 t5 t10 t15

t

t+5

t+10

t+15

t+20

t+60

t+55

t55 t65

no further

detection of

this cell

…

timely resolution: 5 minutes

horizontal resolution: 2 km

t60



METHODOLOGY & RESULTS

Nowcast uncertainty determination



Methodology

Δdistright

Δdistleft

Δdistforward

Δdistback

N

- 0 +

t30,right

Δdistright

N

- 0 +

t30,forward

Δdistforward

N

- 0 +

t30,left

N

- 0 +

t30,backward

Δdistback

Δ = obs - nowcast

Frequency distributions



Results

Δdistright

Δdistforward

N

t30,forward

Δdistforward

N

t30,back

Δdistback

N

t30,right

Δdistright

Δdistleft

t30,left

N

90th percentile

Cumulative

distribution function

20120715



Increase of uncertainty with lead time

LEFT RIGHT

lead time

60 min

5 min

35 min

20120715

observation is

always larger

than nowcast in

direction right

17.14 km P90,abs,60min 18.24 km

1.98 km P90,abs,60min 3.79 km



17.14 km 18.24 km

1.98 km 3.79 km

Increase of uncertainty with lead time

LEFT RIGHT

lead time

60 min

5 min

35 min

20120715



80% intervals in all directions

100 km

nowcast time: 35 min

moving

direction

RIGHT, 35 min

BACKWARD, 35 min

LEFT, 35 min

FORWARD, 35 min

nowcast

mean uncertainty

10th and 90th

percentile

20120715



80 % intervals in all directions

moving direction 5 min

60 min

35 min

20120715



Differing results for different days/situations

July 15th, 2012 July 15th & 10th, 2012

No characteristic distribution

on right extent!



Separate uncertainty analysis

– propagation error

gravity center

moving direction

5 min

60 min

35 min

distance lateral to mov direction 50 km

Gravity center displacement (rel. to obs)

dis

tance i

n m

ov

direction

50 km

50 km

50 km

50 km

50 km

50 km

50 km

0 km

No systematic

misplacement!

20120715



Δdistleft

Separate uncertainty analysis

– extension error

gravity center

Δdistright

Δdistforward

Δdistback

5 min

60 min

35 min

distance 30 km

Extension difference in direction RIGHT

rela

tive c

ounts

-30 km

0

1

0

1

0

1

0

30 km -30 km 0

30 km -30 km 0

Relative small

uncertainties

(P90,rel,right,60min = 5.87 km)

20120715



Correlated distances in separate analysis

Regular growth or

shrinkage on both sides

Equivalent correlation

between FORWARD and

BACKWARD deviations

20120715



Regressions:

Integrated uncertainty development

20120715



Integrated uncertainty development

Larger 90th

percentiles

for directions

BACKWARD

and

RIGHT

20120715



APPLICATION IN

WEATHER AVOIDANCE ROUTING

Nowcast uncertainty determination



Add uncertainty margin around a nowcast

movement direction

35 minutes

nowcast

of a point cell

90th

percentile

uncertainty

margin

20120715



movement direction ~ 1.3°

525 km at 480kt

12 km

20120715 Add uncertainty margin around a nowcast

Additional

heading change

to that forced by

the nowcasted

cells extent.



• Spatial uncertainty determination method of nowcast cells

considering extent and displacement

– Isotropic behavior for both components

– BUT: integrated uncertainty shows characteristic features

Conclusion I

Thank you for your attention!

[email protected]

Integral view Separate view



• Spatial uncertainty determination method of nowcast cells considering extent and displacement



• Quantified rate of increasing uncertainty with lead time

.

Conclusion II

Thank you for your attention!

[email protected]



• Spatial uncertainty determination method of nowcast cells considering extent and displacement



• Quantified rate of increasing uncertainty with lead time

• Uncertainty is even higher due to

– new, not yet nowcasted cells

– Other not yet considered statistics

• dissipating cells

• merged/splitted cells

• Further analyses on different thunderstorm situations

Conclusion



THANK YOU

Contact information:

Manuela Sauer [email protected]

Thomas Hauf [email protected]

Caroline Forster [email protected]