Upload
jacob-golden
View
220
Download
0
Tags:
Embed Size (px)
Citation preview
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 1
Status Report PP KENDA
Christoph SchraffDeutscher Wetterdienst, Offenbach, Germany
Contributions / input by:
Hendrik Reich, Andreas Rhodin, Annika Schomburg, Ulrich Blahak, Yuefei Zeng, Roland Potthast
Yuefei Zeng, Klaus Stephan, Africa Perianez, Michael Bender (DWD)
Chiara Marsigli, Tiziana Paccagnella (ARPA-SIM)
Lucio Torrisi (CNMCA)
Daniel Leuenberger, Luca Weber (MeteoSwiss)
Mikhail Tsyrulnikov, Igor Mamay (HMC)
Amalia Iriza (NMA)
• general overview
• assimilation of SEVIRI-derived cloud top height in LETKF
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 2
LETKF: implementation
experiment chain in NUMEX set up
• GME LETKF exp. (Nens = 40) June 2011 for lateral BC:
somewhat too little spreadparticularly over Europe,but LBC spread at least aslarge as from COSMO-SREPS
(Nens = 12)
ana. spread
ana. rmse
• for COSMO-LETKF: .
lateral BC by direct interpolationfrom 60 km to 2.8 km(moderate noise at model top & surface, acceptable)
• MCH / ARPA-SIM: resolution gap IFS-EPS(32 km to 2.8 km) tested: ok
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 3
LETKF: implementation
experiment chain in NUMEX set up
• lateral BC by direct interpolation from 60 km to 2.8 km
• KENDA:
– 1-hourly cycling, radiosonde, aircraft, wind profiler, synop; 40 ens. members
– assimilation only, optimally takes ~ 1 real day for 1 day of assimilation,but in fact: ~ 1 – 4 real months for 1 week of
assimilation !(without forecasts !!) only 3 experiments so far
• Hendrik: new flexible stand-alone scripts to run LETKF experiments without using NUMEX / archive very limited disk space
1 real day for 1 day of LETKF assimilation
• to do: implement evaluation / verification tools in script suite
• may become very suitable tool for users outside DWD (academia)
• offline adaptive estimation of obs errors in observation space
• multi-step analysis approach (different localization radii for different sets of obs)
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 4
LETKF: ensemble forecasts (20 ens. members)
KENDA / COSMO-DE-EPS
max. 10-m wind gusts 2-m temperature precipitation
results of LETKF (without explicit surface / soil perturbations) :
4 – 12 June 2011
larger rmse,initially larger spread
larger rmse,equal spread
larger rmse,larger spread
RMSE
spread
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 5
• LETKF technically works
• comparison with surface observations suggest
– generally: LETKF better than NO_OBS, but worse than nudging
– assimilation of surface pressure appears to work particularly well
• LETKF_DET analysis very close to LETKF ensemble mean
• SPPT has only small but positive impact
LETKF at MCH, compare det. LETKF analysis with nudging
• COSMO-2, Nens = 40, LETKF as at DWD
• lateral BC from IFS (det./EPS); soil moisture from COSMO-2
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 6
LETKF: implementation of verification
• production of ‘full’ NetCDF feedback files
done: COSMO observation operators (conventional obs) integrated in 3DVAR package
to be done (this autumn !) : extend flow control (read correct Grib files etc.)
• ensemble-related diagnostic + verification tool, using feedback files :(Iriza, NMA)
– ensemble scores implemented, further testing required
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 7
accounting for model error
• stochastic perturbation of physics tendencies (SPPT)(Torrisi)
–implemented in (private) V4_26
–tests at CNMCA / MCH / ARPA-SIM (WG7)
• Pattern Generator (for random fields with prescribed correlation scales)(Tsyrulnikov et al.)
–based on a stochastic partial differential equation approach
–basic version developed, being revised to make it efficient
–being embedded in COSMO code
–2-D version planned for next year
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 8
high-resolution obs
• radar
–obs operators finished, assimilation works technically
–radial winds vr in LETKF: Yuefei Zeng (DWD, until summer 2014)
need to test thinning / superobbing strategies
3-hour assimilation with 1-hrly cycle done (different localization radii)
–vr + reflectivity Z in LETKF: Theresa Bick (HErZ-I Bonn, until end 2014 at least)
• GPS slant path delay
–obs operator (incl. TL / adjoint) implemented in 3DVar, approximations tested
–implementation in COSMO should start soon
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 9
high-resolution obs
• (SEVIRI-based, radiosonde-corrected) cloud top height : see next slides(Schomburg)
• new task: microwave radiometer & Raman lidar T- , q- profiles(Haefele, MCH)
• direct assimilation of SEVIRI radiances (window channels for cloud info)(Perianez)
–technically implemented (obs operator (RTTOV), reading / writing)
–work on monitoring / assimilation start in Nov.
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 10
• avoid too strong penalizing of members with high humiditybut no cloud
• avoid strong penalizing of members which are dry at CTHobs but have a cloud or even only high humidity close to CTHobs
search in a vertical range hmax around CTHobs fora ‘best fitting’ model level k, i.e. with minimum ‘distance’ d:
Z [km]
RH [%]
CTHobs
2
max
2 )(1
))()((min obskobskk
CTHhh
RHfRHfd
function of relative humidity
height ofmodel level
k
= 1
• use f (RHobs=1) – f (RHk)
and CTHobs – hk
as 2 separate obs increments in LETKF
if cloud observed with cloud top height CTHobs ,what is the appropriate type of obs increment ?
(if above a layer with cloud fraction > 70 %, then choose top of that layer)
use of (SEVIRI-based) cloud top height (CTH) ‘observations’ in LETKF: method
k1
k2
k3
k4
k5
Cloud top
model profile
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 11
3
6
9
Z [km]
„no high cloud“
„no medium cloud“
„no low cloud“
CLC
• assimilate cloud fraction CLCobs = 0
separately
for high, medium, low clouds
• model equivalent:
maximum CLC within vertical range
type of obs increment , if no cloud observed ?
use of (SEVIRI-based) cloud top height (CTH) ‘observations’ in LETKF: method
model profile
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 12
relative humiditycloud covercloud water
cloud iceobserved cloud top
3 lines on one colour indicate ensemble mean and mean +/- spread
• 1 analysis step , 17 Nov. 2011, 6 UTC (wintertime low stratus)
vertical profiles
• example: missed cloud event
CTH single-observation experiments
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 13
observed cloud top
observation location
• example: missed cloud event
specific water content [g/kg]
relative humidity [%]
cross section of analysis increments for ensemble mean
CTH single-observation experiments
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 14
CTH single-observation experiments
temperature profile (mean +/- spread)
• example: missed cloud event
first guess analysis
1000 m
2000 m
3000 m
observed cloud top
LETKF introduces inversion due to RH(CTH) T cross correlations in first guess ensemble perturbations
270 K 280 K 290 K 270 K 280 K 290 K
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 15
relative humiditycloud covercloud water
cloud iceobserved cloud top
3 lines on one colour indicate ensemble mean and mean +/- spread
vertical profiles
• example: false alarm cloud assimilated quantity: cloud fraction (= 0)
CTH single-observation experiments
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 16
high cloud cover [octas]
FG
ANA
LETKF decreases erroneous cloud cover despitevery non-Gaussian distributions
mid-level cloud cover [octas]
FG
ANA
• example: false alarm cloud assimilated quantity: cloud fraction (= 0)
FG
ANA
low cloud cover [octas]
cover
CTH single-observation experiments
observation increments - histogram over ensemble members
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 17
0:00 UTC 6:00 UTC 12:00 UTC 17:00 UTC
cycled assimilation of dense CTH obs
observed cloud top height (CTH)
1-hourly cycle over 21 hours, 13 Nov., 21 UTC – 14 Nov. 2011, 18 UTC(wintertime low stratus)
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 18
18
0:00 UTC 6:00 UTC 12:00 UTC 17:00 UTC
cycled assimilation of dense CTH obs :LETKF setup
• thinning: use obs at every 5th grid pt.
• adaptive covariance inflation, adaptive localisation scale ( ~ 35 km)
• Observation error variances : relative humidity = 10 %cloud cover = 3.2 octa
cloud top height [m] :
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 19
19
cycled assimilation of dense CTH obs
RMSE
spread
time series of first guess errors of ensemble mean / spread of ensemble
averagedover
cloudy obs
locations
averagedover
cloud-free obs
locations
underdispersive,but no trend for reductionof spread
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 20
RMSE
bias
time series of first guess errors of RH at observed CTH (det. run), averaged over cloudy obs locations
cycled assimilation of dense CTH obs
no assimilationwith cloud assimilation
CTH assimilation : reduces RH (1-hour forecast) errors
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 21
RMSE
bias
time series of first guess errors of RH at observed CTH (det. run), averaged over cloudy obs locations
cycled assimilation of dense CTH obs
no assimilationwith cloud assimilation
CTH assimilation : reduces RH (1-hour forecast) errors
assimilation of conventional obs only assimilation of conventional + cloud obs
localization scale: adaptive / 20 km
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 22
cycled assimilation of dense CTH obs
time series of first guess errors, averaged over cloud-free obs locations(errors are due to false alarm cloud)
mean square error of cloud fraction [octas]
error reduced(almost) everywhere
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 23
23
No assim
no assimilation cloud assimilation
conventional only conventional + cloud
total cloud coverof first guessfields after
20 hours of cycling
CTH obs
satellite obs
cycled assimilation of dense CTH obs
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 24
Summary
•assimilation of CTH by LETKF reduces errors of first guess (1-h forecast)
tends to introduce humidity / cloud where it should (+ temperature inversion)
tends to reduce ‘false-alarm’ clouds
despite non-Gaussian pdf’s
•no sign of filter collapse (decrease of spread)
•next: evaluate forecast impact
use of (SEVIRI-based) cloud top height (CTH) ‘observations’ in LETKF
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 25
Thank you for your attention
Questions ?
Status of PP KENDA
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 26
LETKF: implementation
GME COSMO
ensemble members 40 + 1 (3DVar) 40 + 1 (det. Run)
horiz. resolution (ens.) ~ 60 km (ni128) 2.8 km
horiz. resolution (det.) ~ 30 km (ni256) 2.8 km
vertical localis. length scale (ln p) 0.3 (fut.: 0.075 - 0.5) 0.3 ; 0.075 – 0.5
horiz. localisation length scale 300 km 100 km
adaptive horiz. localisation - (not used) used in latest exp.
additive covariance inflation 3DVar - B -
adaptive multiplicative cov. infl. yes yes
conventional obs yes yes
satellite radiances AMSU-A -
GPS-RO new exps -
radar data - passive
update frequency 3 h 1 h ( 30 / 15 min)
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 27
LETKF: implementation
• multistep analysis (batch assimilation) implemented motivation:
• local / nonlocal observations (e.g. radiances)
• different observation errors better use different localization scales
• in view of adaptive localization: different obs densities (conventional / radar)
(Perianez et al.: work on paper with theoretical concept + toy model/ idealised experiments)
next step: test with radar / SEVIRI CTH data
• Hendrik: new flexible stand-alone scripts to run LETKF experiments without using NUMEX / archive very limited disk space
1 real day for 1 day of LETKF assimilation
• to do: implement evaluation / verification tools in script suite
• may become very suitable tool for users outside DWD (academia)
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 28
low clouds mid-level clouds high clouds
cycled assimilation of dense CTH obs
‘false alarm’ cloud cover
(after 20 hrs cycling)
conventional+ cloud
conventionalobs only
[email protected] of PP KENDACOSMO General Meeting, Sibiu, 2 – 5 Sept. 2013 29
Low cloud cover (COSMO)
PBPV – 03/2013
29
17:00 UTCCloud assim
convCloud +conv
No assim