QPF verification of DWD-LM and LAMI model using high resolution non-GTS data

in Piedmont region and Northern Italy

Working Group 5: Verification and Case Studies(Co-ordinator C.Cacciamani ARPA-SMR)

4th COSMO meeting 25-27 September 2002 Warsaw

Massimo MilelliElena Oberto

Renata PelosiniPaolo Bertolotto

Overview: the W.P. 5.3.1 since Athens 2001

1 Verification of the QPF based on the Lokal DWD model using high resolution non-GTS data coming from:

– Piedmont Region (from 01/2000 to 06/2002)– Italian Regions (Trentino, Veneto, Emilia Romagna,

Marche, Liguria, Piemonte) from 03/2001 to 06/2002

For Piedmont region we have averaged over warning areas;

for Italian region over boxes sized 0.50° *0.50° (about 50 km * 50 km) that represent the measurement of a mean basin.

Piedmont “warning areas”

• 11 “basins”, 3000 km2

each– 1-2 ECMWF grid points– 60 Lokal Modell grid

points

• Each “basin” is a group of neighbouring hydrological catchments

Verification over Piedmont basins average in 24h

(01/2000-06/2002)•LM12 is slightly better than LM00

•overestimate for low thresholds for the first 24h

•greater underestimate of LM00 for high thresholds

•The first 24h are better than the second (decline with time)

Verification over Piedmont basins average in 24h

(01/2000-06/2002)

•Good results (all the points are in the upper left part)

•LM12+24: good skills for all thresholds (%HR>>%FAR)

•skill decreases with time

Situation of data set for Italy:

data used

data not yet useful

data soon available

period area (kmq) stations resolution (km)Piemonte 01/01-08/02 25400 87 17

Liguria 01/01-08/02 5400 35 12Veneto 03/01-06/02 18000 83 15

Emilia Romagna 12/00-08/02 22000 42 23Trentino 01/01-06/02 6800 18 19Marche 01/01-08/02 9700 12 28

Sardegna 12/00-12/01 24000 49 2287300 277 19

Verification over Italy, box 0.5° average in 24h

(03/2001-06/2002)

Underestimate for thresholds > 10 mm

Are these stations representative of high precipitation?

About 45 grid point/box compare with 4/5 station point: is there any smooth of the forecasted signal ?

Verification over Italy, box 0.5° average in 24h

(03/2001-06/2002)

2 Sensitivity: we have carried out a parametric study of the averaging mesh size, in order to find the optimum area for QPF evaluation.

Data from:

– Piedmont Region (from 01/2000 to 06/2002)– Italian Regions (Trentino, Veneto, Emilia Romagna,

Marche, Liguria, Piemonte) from 03/2001 to 06/2002

box (degrees) Lat (km) Lon (km) n° boxes available n° boxes used n° grid p. n° station p.0.25 28 20 141 51 16 30.5 55 40 55 47 64 60.75 83 60 29 28 144 9

•AA perform slightly better

Sensitivity over Piedmont, boxes average in 24h

01/2000-06/2002

•verification sensitive to the definition of the areas

Sensitivity over Piedmont, boxes average in 24h

01/2000-06/2002

Sensitive to area size

•not all the boxes considered

•all the boxes taken into account

Sensitivity over italian regions,

boxes average in 24h

03/2001-06/2002

Sensitivity over italian regions,

boxes average in 24h

03/2001-06/2002

3 Verification of LAMI model using high resolution non-GTS data from Piedmont

region, warning areas averaged, over period

from 06/2002 to 08/2002

•Lami12 is better than Lami00

•the first 24h overestimate more than the second 24h

A comparison of the two models:• Lami +24 overestimates more than LM +24• Lami +48 has a different behaviour with respect to the thresholds and it is worse than LM +48

Conclusions

• Generally, the 12 runs (LAMI and LM-DWD) have better skills more inertia of the atmosphere at 00 UTC in the triggering of the precipitation

• The model performance decreases with time (known !)

• Lami first 24h overestimates the precipitation: probably due to the missing data assimilation cycle

• Sensitivity tests show a great dependency of the QPF skill on area definition; this definition has to be based on the morphology and on the climatology of severe events

•the QPF skill for hydrogeological risk assessment over Piedmont is good (importance of working with end-user targeted verification)

Toce Sesia Orco Riparia Stura Tanaro Belbo Scrivia Pianura N Pianura S

76 91 96 6699 68 66 63

BASINTHRESHOLD

(mm/24h) 121 122

Precipitation thresholds for warning over Piedmont basins

averaged in 24h 01/2000-12/2001