Verification of lami local area model italy using non gts data over mountainous regions
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Verification of LAMI (Local Area Model Italy) using non-GTS Data over Mountainous Regions. Elena Oberto (*), Stefano Bande (*), Massimo Milelli (*) (*) ARPA Piemonte, Torino, Italy. LAMI model.

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Verification of LAMI (Local Area Model Italy) using non-GTS Data over Mountainous Regions

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Verification of LAMI (Local Area Model Italy) using non-GTS Data over Mountainous Regions

Elena Oberto (*), Stefano Bande (*), Massimo Milelli (*)

(*) ARPA Piemonte, Torino, Italy


LAMI model

  • Non-hydrostatic Limited Area Model (Italian version) developed in the framework of the COSMO (Consortium for Small-Scale Modelling) project between Germany, Poland, Switzerland, Greece and Italy.

  • Technical aspects:

  • Domain: 50°/2°/32°/24° (234*272 grid points)

  • Resolution: 0.0625° (7.5 Km)

  • Vertical layers: 35

  • Forecast time: +48h (+72h available since Dec ‘02: not taken into account because of the poor statistics)

  • Model runs: 00,12 UTC

  • Boundary conditions: GME (DWD)

  • Initial conditions: GME (nudging version available since Dec ‘02: not taken into account because of the poor statistics)


Objectives

  • Verification of precipitation above 1000 m:

    • LAMI model output compared to observations over the western alpine chain. This is a study of high resolution model reliability in case of complex orography in perspective of the XX Olympic Winter Games in 2006.

    • Period considered: Oct ‘02- Feb ‘03.

    • Standard schemes of precipitation verification: contingence tables for different thresholds and statistical indices like BIAS, ETS, FAR and HRR.

    • Very dense non-GTS network of rain gauges (126) in the north-west part of the Alps (Piemonte, Liguria, Valle d’Aosta, Ticino) above 1000 m.

    • Method: comparison between station point and grid point (the one with the closest elevation among the 4 surrounding grid points).


  • Verification of vertical profile:

    • The new radiosounding of Cesana Pariol (1545 m), placed in the Olympic area, is used to compare the observed and forecasted vertical temperature profiles (at 00UTC every day)

    • An other radiosounding in our region is placed near Cuneo Levaldigi Airport (installed in 1999, since 1 year it is a GTS station): we perform the same vertical temperature profile verification to have a comparison with a station in a non-mountainous area.

    • Mean error (BIAS) and Root Mean Square Error for each level (averaged levels every 25hPa) of the temperature vertical profile (00UTC LAMI run for +24h and +48h forecast time) from Dec ‘02 to Feb ‘03.

    • Cesana Pariol (45° N 6.8° E): station point 1545 m

      grid point 1970 m

    • Cuneo Levaldigi (44.5° N 7.6° E): station point 386 m

      grid point 387 m


Rain gauges network

  • 126 station above 1000 m

  • Regions interested: Piemonte, Valle d’Aosta, Liguria, Ticino

  •  Cesana sounding

  •  Cuneo sounding


LAMI00-LAMI12: comparison between the first and

the second 24h versus thresholds

ETS: results between 0.25-0.35  no significative differences between the two runs and between the two days of integration.

BIAS: globally good results, always greater than 1, for high thresholds the first 24h of both runs perform better especially for 12UTC.


ROC diagram confirms previous results: small differences between the two runs, but less FAR for the first integration time


LAMI00-LAMI12: comparison of the 12h-QPF performance

for 3 fixed thresholds

  • For every thresholds there is a diurnal cycle of error.

  • The precipitation is generally overestimated

  • BIAS influenced by the diurnal cycle more than forecast time

  • BIAS better in the morning (00-12UTC)


The same behaviour comes out in ETS index for low thresholds only; for high thresholds (not shown here) the signal is smoothed.

LAMI00-LAMI12: BIAS for the 6h-QPF

Concerning the low thresholds, the same diurnal cycle is evident: the worst results are found during the night (18-00UTC)


Cuneo sounding

  • bad agreement with observation close to the ground

  • bias > 1 in the first levels probably due to a wrong heat flux parameterisation that gives a colder model forecast

  • above 700 hPa: good bias for both forecast times

  • above 800 hPA: +24h rmse is better than +48h rmse, slight worsening of the results with time.


Cesana sounding

  • 800 hPa - 700 hPa: model T is cooler than observation due to the elevation difference and to a systematic underestimation

  • worsening in time: +24h bias is closer to 0 than +48 bias, +24h rmse is higher than +48h.


Conclusions

  • Globally good skills for LAMI QPF verification: general overestimation in precipitation, worsening in time.

  • Diurnal cycle present and quite evident with worst results during the coldest hours.

  • Good results for the vertical temperature profile above 700 hPa.

  • Problems close to the ground probably due to the physical parameterisations.

  • Next step: verification of the other variables of the sounding (Rh, DwT, wind direction and velocity)


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