Simulations of MAP IOPs 14-15 with Lokal Modell: impact of nudging on forecast precipitation

Simulations of MAP IOPs 14-15 with Simulations of MAP IOPs 14-15 with Lokal Modell: impact of nudging on Lokal Modell: impact of nudging on

forecast precipitationforecast precipitationFrancesco Boccanera, Andrea Montani

ARPA – Servizio Idro-Meteorologico Regionale, Bologna, Italy

5th CARPEDIEM Project Meeting

Dublin, December 15, 2003

Lokal Modell (LM)Lokal Modell (LM)• Non-hydrostatic model operational at ARPA-SIM

• Provided of nudging-based data assimilation scheme

• Initial and boundary conditions from 3-hourly ECMWF analyses

Integration domainIntegration domain

Prognostic variablesPrognostic variables•Horizontal and vertical wind components•Temperature•Pressure perturbation•Specific humidity•Cloud water content•Cloud ice content

Diagnostic variablesDiagnostic variables•Total air density•Precipitation fluxes of rain and snow

Horizontal resolutionHorizontal resolution10 Km

Vertical levelsVertical levels35

““Carpediem” model configurationCarpediem” model configuration

The The nudgingnudging-based assimilation scheme-based assimilation scheme

t=t0t= -TnudAssimilation periodAssimilation period forecastforecast periodperiod

During the assimilation period, a term is added to the model’s prognostic variables. This term (called “nudging term”) depends on the difference between observed and model state.

Observations (about 2*104 per day)

),(),,()(

txWGtxFdtd

kkk

kobs

),,,( tzyxWW kk

Nudging term

is the generic prognostic variable of the model

IOP14: performed runs

Name of simulation

Date and hour of start

AssimilationPeriod

Assimilated variables

CNTL_0004/11/9900 UTC No

NUD_0003/11/9900 UTC

Yes24 hours

Horizontal wind Temperature

Surface pressureRelative humidity

03/11 00 UTC

04/11 00 UTC

assimilation forecast

24h precipitation cumulated from 04/11 00 UTC to 05/11 00 UTC24h precipitation cumulated from 04/11 00 UTC to 05/11 00 UTC

IOP 14

Nud_00 (cum 0-24 hr)

Cntl_00 (cum 0-24 hr)

04/11/99 00 UTC 2m-temperature and 10m-wind 04/11/99 00 UTC 2m-temperature and 10m-wind


Nud_00 (analysis)Cntl_00 (analysis)

-6 0 6 12 18

Cntl_00 (fcst +6 hr) Nud_00 (fcst +6 hr)

IOP15: performed runsName of

simulationDate and hour

of startAssimilation Assimilated

variables

CNTL_0006/11/9900 UTC No

NUD_0005/11/9900 UTC

Yes24 hours

Horizontal windTemperature


CNTL_1206/11/9912 UTC No

NUD_1205/11/9912 UTC

yes24 hours

Horizontal windTemperature


24h Precipitation cumulated from 06/11 00 UTC to 07/11 00 UTC24h Precipitation cumulated from 06/11 00 UTC to 07/11 00 UTC



IOP 15




IOP 15


-18 -12 -6 0 6 12 18

Nud_00 (fcst +24 hr)Cntl_00 (fcst +24 hr)

Cntl_12 (fcst +12 hr) Nud_12 (fcst +12 hr)

Main results IOP 14

• The run with data assimilation provides an improvement of precipitation forecast over North-Western Italy (when compared to the control run), although a maximum not observed is also predicted.

• The nudging assimilation scheme has a negligible impact on the forecast of temperature and wind fields

IOP 15

• The run with data assimilation has a non-negligible impact on the forecast of precipitation, but does not bring a substantial improvement.

• The use of the nudging assimilation scheme does not have an appreciable impact on the forecast of temperature fields; on the other hand, it allows the generation of different structures in terms of wind forecast.

Possible developments• Play with the nudging coefficients

• Generate “synthetic” radar images from the forecasts of Lokal Modell


Nud_12

Cntl_12

IOP14: performed runsName of

simulationDate and hour

of startAssimilation

PeriodAssimilated

variables

CNTL_0004/11/9900 UTC No

NUD_0003/11/9900 UTC

Yes24 hours

Horizontal windPotential temperature


CNTL_1204/11/9912 UTC No

NUD_1203/11/9912 UTC

yes24 hours

Horizontal windPotential temperature





IOP 15


Nud_00 (cum 0-6 hr)



Nud_00 (cum 0-6 hr)


IOP 14




IOP 15

Simulations of MAP IOPs 14-15 with Lokal Modell: impact of nudging on forecast precipitation

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