SPHERA (High Resolution REAnalysis over Italy): system setup and tests Ines Cerenzia, Tiziana Paccagnella, Andrea Montani Arpae-Emilia Romagna, Regional Service for Environment Protection and Energy, Bologna Italy International Symposium on Regional Reanalysis, Bonn, July 2018
Overview Overview ● Introduction ● Question1: 1step or 2steps nest into driver model? ● Question2: which deep temperature does assign to the regional model?
Motivation Motivation Climate study: provide a high resolution, space and time consistent description of the past decades climate characteristics NWP model evaluation for the operational forecast: provides a testbed for extended period (multi-decadal) evaluation of regional models (e.g. severe weather events) Downstream applications: provide boundary conditions to high Yearly averaged T2m and cumulated precipitation resolution models (e.g. coastal erosion and marine sediment, sea- anomaly over Emilia-Romagna (ERACLITO, Antolini et al. 2015) state,air pollution,..) PM10-2017
Confiuration Confiuration Model: Consortium for Small Scale Modeling ● (COSMO) non-hydrostatic limited area model – convection permitting resolution (2.2km) – Hourly output – Setup based on NWP operational forecast – Initial state from ERA5 ● Boundary conditions: ● Hourly at the border for upper air fields – Sea state daily updated to ERA5 – Soil/snow/lake autonomous – Data Assimilation: continuous nudging of ● surface/upper air convectional observations (no radar and satellite) Temporal Coverage : 1985-2020 ● Production : 09/2018-12/2020 ●
Q1: 1step or 2steps nest into ERA5? Q1: 1step or 2steps nest into ERA5? 2step COSMO (2.2km) COSMO (2.2km) COSMO (2.2km) COSMO (2.2km) COSMO (10km) COSMO (10km) ERA5 - IFS ERA5 - IFS (31km) (31km) COSMO (2.2km) COSMO (2.2km) 1step
Q1: 1step or 2steps nest into ERA5? Q1: 1step or 2steps nest into ERA5? 2step COSMO (2.2km) COSMO (2.2km) COSMO (2.2km) COSMO (2.2km) COSMO (10km) COSMO (10km) Deep convection: Soil/Snow interpolated Tiedtke scheme from COSMO10km Soil/Snow/Lake Lake autonomous autonomous ERA5 - IFS ERA5 - IFS (31km) (31km) COSMO (2.2km) COSMO (2.2km) 1step Soil/Snow/Lake autonomous
Accumulated precipitation 2015 Accumulated precipitation 2015 ERA5 1step 2step
Accumulated precipitation 2015 Accumulated precipitation 2015 ERA5 1step 2step
Daily accumulated precipitation - Obs Daily accumulated precipitation - Obs Verification using boxes of 0.25°x0.25° Observations not ingested in data assimilation WINTER ● 1step performs better than 2step at almost all thresholds (less FA, less BIAS) ● Regional reanalysis improves against ERA5 for precipitation >25mm (more POD and FA)
Daily accumulated precipitation - Obs Daily accumulated precipitation - Obs Verification using boxes of 0.25°x0.25° Observations not ingested in data assimilation SUMMER ● Even larger improvement of 1step to 2step than winter (less FA, less BIAS) ● Regional reanalysis improves against ERA5 for precipitation >10mm (more POD and FA)
T emperature at 2m - Obs T emperature at 2m - Obs Stable PBL Surface warming up 1step performs better than 2 step, especially in uneasy conditions to represent SPHERA improves in bias and rmse over land compared to ERA5
1step performs better than 2step, especially in summertime, and it generates less precipitation than 2 step • Convection is too pumped in 2step due to the deep convection parametrization in the intermediate COSMO integration? • Noise introduced by the intermediate step in the nest? Gravity waves? • Soils develop differently?
SUMMER Energy spectra 4km 14km of the vertical 12UTC wind speed at different altitudes Higher energy in the free atmosphere in 2step than 1step 24/07/2015 at 12UTC: several convective cells over Italy 275m 20m Lower energy in the CBL in 2step than 1step
Soil diferences Soil diferences 1step: self-developing soil at 2.2km 2step: interpolated from the intermediate resolution run at 10km
Q2: Which deep soil temperature? Q2: Which deep soil temperature? Soil can have a large effect on long time scales due to its inertia In regional models, the temperature of the deepest soil level is set: ● By vertically interpolating the driver model.. but not always meaningful (Hdeep in ERA5 = -1.89m >> Hdeep in COSMO = -14.58m) ● By boundary conditions, e.g. flux =0 or T=const .. but it misses the interannual thermal changes and the global warming Idea: Parametrize it using the soil features of the driver model at the deepest levels
Parametrizations Parametrizations 1) 5 stations over Europe with multi-years deep soil temperature observations over (0.5m-12m) 2) 3 parametrizations of the soil annual thermal cycle (iiven two time series of T soil at two shallower depths, and assumini constant thermal difusion below the iiven levels) 1) Method of amplitude (Evett, 2002) 2) Method of phase (Verhoef et al, 1996) 3) Three-yearly runnini mean delayed by a time lai <===== 3) Reconstruct the Tdeep feld at -14.58m required by COSMO 4) Re-run for 12months+6months (spin-up) 1)
Diferences of Tdeep Diferences of Tdeep Standard solution in COSMO: 1) Report deepest temperature of ERA5 to deepest level of SPHERA (-1.89m! =-14.58m 2) Keep it constant from the initialization time Compared to time lai method ------> Diferences depend on the ● Initialization time ● Soil type (lonier lai in Po valley than over Alps) ● Time passed since initialization Diferences can be as larie as 3°C
Diferences of Tdeep Diferences of Tdeep Standard solution in COSMO: 1) Report deepest temperature of ERA5 to deepest level of SPHERA (-1.89m! =-14.58m 2) Keep it constant from the initialization time Compared to time lai method ------> Diferences depend on the ● Initialization time ● Soil type (lonier lai in Po valley than over Alps) Questions: 1) How large is the impact into the soil? ● Time passed since initialization 2) Is there an effect at the surface and in the Diferences can be as larie as 3°C atmpsphere? 3) After how much time?
Conclusions Conclusions ● SPHERA at 2.2km will cover Italy from 1985-2020. First 5 years will be ready by the end of 2018 ● Direct nest (1step) into ERA5 with a 1:15 resolution step between the inteiration domains performs better than traditional resolution steppini (1:3:5) for precipitation and temperature at 2m. ● Reason is likely the diferent soil status in 1step and 2step. ● Deep soil temperature should be considered when settini loni-term inteiration. Update it to a simple runnini mean of the deepest temperature available from the driver model could already be a iood solution ……. Thanks for your attention! 1)
Additional Material COSMO-2Nest COSMO-1Nest COSMO-2I COSMO-10M ● IC : Era5 il primo giorno, poi inizializzazione a caldo IC : Era5 il primo giorno, poi inizializzazione a caldo ● ● BC: Era 5 /1h BC: Era 5 /1h ● ● Suolo/Neve/Laghi autonomi Suolo/Neve/Laghi autonomi ● ● SST aggiornata a ERA5 ogni giorno SST aggiornata a ERA5 ogni giorno ● ● Periodo: 2015 + 6mesi di inizializzazione (7/2014-12/2014) Periodo: 2015 + 6mesi di inizializzazione (7/2014-12/2014) ● ● Osservate: SYNOP/SHIP/TEMP/PILOT/ AIREP (METAR durante Osservate: SYNOP/SHIP/TEMP/PILOT/ AIREP (METAR ● ● i primi 5mesi di inizializzazione) durante i primi 5mesi di inizializzazione) Vers:INT2LM 2.04, COSMO 5.3 in single precision (no Vers:INT2LM 2.04, COSMO 5.3 in single precision (no urban, ● ● Tiedtke convection) urban) Dominio: COSMO-5M Dominio: 16 punti griglia più largo rispetto a COSMO-2I in ● ● ogni direzione ● COSMO-2I IC : COSMO-10M il primo giorno, poi inizializzazione a caldo ● BC: COSMO-10M /1h ● Suolo/Neve/SST interp. da COSMO-10M; laghi autonomi ● Vers:INT2LM 2.04, COSMO 5.3 in single precision (no urban) ● Dominio:COSMO-2I ●
JJA average of the T2m difference 1step-2step
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