Lateral boundary conditions and forecast errors in the mid-latitudes – first results Luka Honzak, Nedjeljka Žagar, Gregor Skok CE Space-SI and University.

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