Heat and freshwater budgets over the Mediterranean area
from a new 34-year MED-CORDEX hindcast
Béranger K.*(1,2), Anquetin S.(2), Arsouze T.(1,3), Bastin, S.(1), Bouin M.-N.(4), Berthou S.(1),
(2)
(1)
(6)
(2)
(1)
Boudevillain B. , Claud C. , Lebeaupin Brossier , Delrieu G. , Dubois, C.(5), Drobinski P. ,
(2)
(2)
(1)
(1)
(6)
(6)
(1)
Froidurot, S. , Molinié, G. , Polcher J. , Rysman J.-F. , Sevault, F. , Somot, S. , Stéfanon M.
(*[email protected])
(1-IPSL, 2-LTHE, 3-ENSTA-ParisTech, 4-Météo-France/Brest, 5-Mercator Ocean, 6-CNRM)
The companion atmospheric simulations
Introduction : Two atmospheric multi-decadal hindcasts were done for the 1979-2012 period by running a dynamical downscaling of the ERAInterim reanalyses (Simmons et al., 2007) with the non hydrostatic WRF model (Skamarok et al 2009). In the perspective of being coupled to the
ocean NEMO (Madec and the NEMO team, 2008) and land ORCHIDEE (Polcher, 2003) models to run hindcasts and scenarii, we focus our analyses
on the Mediterranean heat (QNET) and freshwater (EMP) budgets, which may play an important role in the changes of the thermohaline circulation.
Results are presented here for QNET and EMP, which climatological values are considered close to -5 W/m 2 and 0.7 m/yr respectively. Comparisons
are done with several climatologies, for which a lart part is reported in Sevault et al. (2014). Besides, we looked at the precipitation over land too,
which may have impacts on river runoff. Comparisons over regional to sub-regional land areas are done with the EOBS dataset for the precipitation
and 2-m temperature (Haylock et al. 2008).
The atmospheric companion simulations: The non hydrostatic WRF model (Skamarok et al 2009) (version 3.6.1) is used with 20-km horizontal
resolution. The model is run over two areas covering the MED-CORDEX basin, that are called the MORCE1 and MORCE2 domains. The MORCE1
domain is those described by Drobinski et al. (2012) and MORCE2 is slightly larger to the north and east in order to better simulate the catchment
basins. Compared to the previous configuration MORCE1 of Lebeaupin Brossier et al. (2011), the vertical resolution was increased from 28 to 44 σlevels and new parameterization sets are applied according to Di Luca et al. (2014). The radiative scheme is based on the Rapid Radiative Transfer
Model (RRTM) (Mlawer et al., 1997) and the Dudhia (1989) parameterization for the longwave and shortwave radiation, respectively. The aerosol
feedbacks from the parameterization of Alapathy et al. (2012) was applied with the climatology of Tegen et al. (2007). Precipitation and evaporation
are solved throught the WRF Single-Moment 5-class microphysical scheme (Hong et al. 2004) and the Kain-Fritsch convection scheme (Kain 2004).
The planetary boundary layer (PBL) scheme and a 2.5 level TKE scheme for the turbulent fluxes (MYNN; Nakanishi and Niino 2006) are applied.
For the land surface, the RUC scheme with 6 layers (Smirnova et al. 1997) is used. The model time-step is 60s. A spectral nudging is applied for
temperature, humidity and velocity components above the PBL to keep the chronology of the large scale atmospheric circulation. These simulations
are compared to previous works of Lebeaupin Brossier et al. (2014,CLB2014) and Berthou et al. (2014, SB2014).
The Mediterranean Sea heat budgets
(W.m-2)
Net heat flux
(Lebeaupin Brossier C. et al. 2014)
(Berthou S. et al. 2014)
The 34-year climtology of precipitation from EOBS dataset. Full lines indicated the
MORCE1 and MORCE2 domains of the companion simulations while small boxes
indicate land areas of precipitation and 2-m temperature averages in both products.
Net surface shortwave flux
(W.m-2)
-2
(W.m )
MORCE2
METEOSAT
METEOSAT
MSG
NOCS
SRB-QC
ISCCP
Seasonal cycle (1983-2005)
(months)
December
Net surface shortwave flux
(yr)
July
(yr)
(figure including climatological estimates reported by Sevault et al. (2014))
(m/yr)
Freshwater flux
(yr)
MORCE1
MORCE2
QNET (W.m-2)
+2.42
-2.52
QLAT (W.m-2)
-101.91
-105.61
QSNS (W.m-2)
-14.63
-15.24
Q_IR (W.m-2)
-81.31
-82.39
QSOL (W.m-2)
200.27
200.72
EMP (m/yr)
0.86
0.90
EVAP (m/yr)
1.29
1.33
PRECIP (m/yr)
0.43
0.43
(W.m-2)
Latent heat flux
NOCS
OAFLUX
(yr)
34-year climatological averages
METEOSAT
METEOSAT
MORCE2
MORCE2
→ The 34-year average QNET of -2.5W.m-2 in MORCE2 is in agreement with climatological estimates whereas its corresponding EMP of 0.9 m/yr
is higher by 0.3 m/yr compared to climatological values. The cold period since 1999 is well reproduced as it is for the freshwater positive trend.
Precipitation in sub-regions
MED area (1979-2012)
Alps (1979-2008)
Cévennes-Vivrais (2008-2012)
30-year precipitation climatology
11-year precipitation occurrence climatology (2002-2012)
Autumn (SON)
Summer (JJA)
MORCE2
(mm/day)
MORCE2
(mm/day)
MORCE2
(mm/month)
34-year precipitation climatology in MORCE2
(mm/day)
(Isotta et al., 2014)
(months)
EOBS (Haylock et al., 2008)
Its corresponding precipitation occurrence climatology
MORCE2
OHMCV (Delrieu et al. 2014)
2008
2009
2010
2011
AMSU (Rysman et al. 2015)
2012
Interannual variability of P
in OHMCV box
P in Alpes box (1979-2008)
(mm/month)
→ The precipitation climatology in MORCE2 is in agreement with the EOBS dataset. Using other datasets
allow to identify some bias at sub-regional scales, maybe due to lacks in the EOBS station network. In the
Alps zone, the interannual variability is better simulated than the seasonal cycle. In the Cevennes-Vivarais
area, the simulated precipitation is underestimated, although the raining episodes are reproduced by the
model. Compared to AMSU, the precipitation occurrence patterns are in some place well simulated, in
particular over the sea, but the precipitation occurrence values seem to be surestimated by the model.
EOBS (Haylock et al., 2008)
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Acknowledgments :The METEOSAT-MSG datasets were available by www.csmaf.eu (DOI:10.5676/EUM_SAF_CM/CLARA_AVHRR/V001). We
acknowledge the E-OBS dataset from the EU-FP6 project ENSEMBLES (http://ensembles-eu.metoffice.com) and the data providers in the ECA&D project
(http://www.ecad.eu). This work is funded by REMEMBER (French ANR project).