Lateral boundary conditions and forecast errors in the mid-latitudes
– first results
Luka Honzak, Nedjeljka Žagar, Gregor Skok
CE Space-SI and University of Ljubljana
1
ErrorsError sources in RCM:
•domain size
•nesting approach
•resolution difference between GCM and RCM
•temporal density of LBCs update
•LBCs errors
We limit our study to the domain size:
•LBC update and nesting the same in all simulations
•resolution of GCM and RCM the same
•LBCs are assumed “truth” (analyses)
2
Hch
WRF setup
Ch: Mid-latitude channel, 1439139 points (35oN and 70oN)
Hch: Euro-Atlantic sector (100oW and 60oE), 639139 points
Eu: Europe (45oW and 45oE), 319139 points
Horizontal resolutions: 0.250.25 degrees
IC/LBC: operational analyses of ECMWF on the same grid available with time frequency of 6 hours. Pre-processing: 91 ECMWF model levels interpolated to 31 WRF levels.
Top level at 10 hPa, six levels below 850 hPa, 20 levels between 850 and 100 hPa and five levels are in the stratosphere. =0 at the top.
Ch Eu
3
Hch
WRF simulations
Ch Eu
Three simulations carried out on each domain
Starting dates 6 days apart (1.1.2009, 7.1.2009, 13.1.2009)
Simulation length 3 months (31.3.2009)
Verification against ECMWF on the same grid
Fields: wind, geopotential, temperature on 30, 100, 250, 300, 500, 700, 850 and 925 hPa
4
Total precipitation accumulated between 15.1.2009 and 31.3.2009
Ch, exp 1
TRMM
ECMWF
5
Ch Ch
Meridional wind at 250 hPaeridional wind at 250 hPa
Geop. height at 500 hPa Geop. height at 500 hPa
Zonal wind at 250 hPa Zonal wind at 250 hPa
Time averaged rmse: Ch 6
Ch Ch
MMeridional wind at 250 hPaeridional wind at 250 hPa
Geop. height at 500 hPa Geop. height at 500 hPa
Zonal wind at 250 hPa Zonal wind at 250 hPa
Time averaged rmse: Hch
HHcchh
7
Ch Ch
MMeridional wind at 250 hPaeridional wind at 250 hPa
Geop. height at 500 hPa Geop. height at 500 hPa
Zonal wind at 250 hPa Zonal wind at 250 hPa
Time averaged rmse: Eu
HHcchh EuEu
8
Average meridional profiles of rmse
HcHchh ChCh
EuEu
U U windwind at at 250 hPa250 hPa
V V windwind at at 250 hPa250 hPa
Geop. height at 500 hPaGeop. height at 500 hPa
9
Internal variability: total precipitation
Ch, experiment 3
Ch, experiment 1
Ch, experiment 2
10
ChCh
Internal variability: zonal wind at 250 hPa
HHcch h
1. experiment (1.1.2009)1. experiment (1.1.2009)
2. experiment (7.1.2009)2. experiment (7.1.2009)
3. experiment (13.1.2009)3. experiment (13.1.2009)
11
Internal variability: zonal wind at 250 hPa
Ch Ch HHcchh Ch on Ch on HHcchh
ChCh on on EuEu HcHchh on on EuEu EuEu
12
Internal variability: zonal wind at 250 hPa
HcHchh ChCh
EuEu
1. experiment1. experiment
2. experiment2. experiment 3. experiment3. experiment
13
Future work
Coupling WRF Ch, Hch, Eu into meridionally larger WRF channel (Lch: 30oN and 80oN)
14
Top Related