Simulations of MAP IOPs with Lokal Modell: impact of nudging on forecast precipitation Francesco Boccanera, Andrea Montani ARPA – Servizio Idro-Meteorologico Regionale, Bologna, Italy 6 th CARPEDIEM Project Meeting Helsinki, June 24, 2004
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 domain Prognostic variables Horizontal and vertical wind components Temperature Pressure perturbation Specific humidity Cloud water content Cloud ice content Diagnostic variables Total air density Precipitation fluxes of rain and snow Horizontal resolution 10 Km Vertical levels 35 “Carpediem” model configuration
The nudging-based assimilation scheme t=t 0 t= -T nud Assimilation period forecast period 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*10 4 per day) Nudging term is the generic prognostic variable of the model
IOP14: performed runs Name of simulation Date and hour of start Assimilation Period Assimilated variables CNTL_00 04/11/99 00 UTC No NUD_00 03/11/99 00 UTC Yes 24 hours Horizontal wind Temperature Surface pressure Relative humidity 03/11 00 UTC 04/11 00 UTC assimilation forecast
24h 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 06 UTC 2m-temperature and 10m-wind Nud_00 (analysis)Cntl_00 (analysis) Cntl_00 (fcst +6 hr)Nud_00 (fcst +6 hr)
IOP15: performed runs Name of simulation Date and hour of start AssimilationAssimilated variables CNTL_00 06/11/99 00 UTC No NUD_00 05/11/99 00 UTC Yes 24 hours Horizontal wind Temperature Surface pressure Relative humidity CNTL_12 06/11/99 12 UTC No NUD_12 05/11/99 12 UTC yes 24 hours Horizontal wind Temperature Surface pressure Relative humidity
24h Precipitation cumulated from 06/11 00 UTC to 07/11 00 UTC Nud_00 (cum 0-24 hr) Cntl_00 (cum 0-24 hr) IOP 15
24h precipitation cumulated from 06/11 12 UTC to 07/11 12 UTC Nud_12 (cum 0-24 hr) Cntl_12 (cum 0-24 hr) IOP 15
07/11/99 00 UTC 2m-temperature and 10m-wind 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 Multi-analysis experiments (Hirlam-Lokal Modell)
24h precipitation cumulated from 04/11 12 UTC to 05/11 12 UTC Nud_12 Cntl_12
IOP14: performed runs Name of simulation Date and hour of start Assimilation Period Assimilated variables CNTL_00 04/11/99 00 UTC No NUD_00 03/11/99 00 UTC Yes 24 hours Horizontal wind Potential temperature Surface pressure Relative humidity CNTL_12 04/11/99 12 UTC No NUD_12 03/11/99 12 UTC yes 24 hours Horizontal wind Potential temperature Surface pressure Relative humidity
6h precipitation cumulated from 06/11 18 UTC to 07/11 00 UTC Nud_00 (cum 0-24 hr) Cntl_00 (cum 0-24 hr) IOP 15
6h precipitation cumulated from 04/11 06 UTC to 04/11 12 UTC Nud_00 (cum 0-6 hr) Cntl_00 (cum 0-6 hr)
6h precipitation cumulated from 04/11 00 UTC to 04/11 06 UTC Nud_00 (cum 0-6 hr) Cntl_00 (cum 0-6 hr) IOP 14
6h precipitation cumulated from 06/11 18 UTC to 07/11 00 UTC Nud_00 (cum 0-24 hr) Cntl_00 (cum 0-24 hr) IOP 15