Slide 1 EUMETSAT Fellow Day, 9 March 2015 Observation Errors for AMSU-A and a first look at the...
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Transcript of Slide 1 EUMETSAT Fellow Day, 9 March 2015 Observation Errors for AMSU-A and a first look at the...
Slide 1
EUMETSAT Fellow Day, 9 March 2015
Observation Errors for AMSU-A and a first
look at the FY-3C MWHS-2 instrument
Heather Lawrence, second-year EUMETSAT fellow, ECMWF
Supervised by: Niels Bormann & Stephen English
Slide 2
EUMETSAT Fellow Day, 9 March 2015
AMSU-A Observation Errors
Slide 3
EUMETSAT Fellow Day, 9 March 2015
The AMSU-A Instrument
10 Temperature sounding
channels6 satellites: good global coverage
(RIP NOAA-16 June 2014)
Microwave Temperature Sounder
Slide 4
EUMETSAT Fellow Day, 9 March 2015
Chs 9 – 14: used globally after thinning and
VarQC
Chs 5 – 8: also screened for cloud, orography,
some sea-ice
6h metop-A, metop-B
orography
cloud
AMSU-A current data usage: clear-sky assimilation
Sea-ice, orography
Slide 5
EUMETSAT Fellow Day, 9 March 2015
New Observation Errors and screening part 1: channels 5 - 8
OLD METHOD
orography
cloud
cloud
orography
NEW METHOD
• Clear-sky forward model RTTOV
• Filter cloud and orography
• Constant observation errors
• Clear-sky forward model RTTOV
• Keep some cloud and orography
• Use more physical observation errors
Slide 6
EUMETSAT Fellow Day, 9 March 2015
Different satellite instruments have
different noise terms:
Instrument NedT
Cha
nnel
Num
ber
NedT values from Nigel Atkinson, UKMO
NOAA-18
Aqua
Cha
nnel
Num
ber
Observation Error
Aqua
NOAA-18
Use different observation errors for
different satellite AMSU-As:
New Observation Errors and screening part 2: Satellite-dependent Observation Errors
Slide 7
EUMETSAT Fellow Day, 9 March 2015
New Observation Errors and Screening
1. Situation-dependent observation error model for channels 5 – 7
2. Remove first guess check for channels 6 – 8 in cloudy regions (use lwp and scatter index check)
3. Replace orography screen with observation error screen over land
4. Satellite-dependent observation errors
Increased number of used data:
Ch 5 - 6: orography Ch 6 – 8: over ocean
ch 5: 6%
ch 6: 11%
ch 7: 8%
ch 8: 3%
Slide 8
EUMETSAT Fellow Day, 9 March 2015
SUMMER: Improved fit of 12-hour forecast
to ATMS
improvement
SUMMER: improved forecast scores
Contribution to CY41R2
Impact on forecast accuracy
WINTER: neutral forecast scores
No
rma
lise
d d
iffe
ren
ce
Forecast day
No
rma
lise
d d
iffe
ren
ce
Forecast day
WINTER: Improved fit of 12-hour forecast
to ATMS
improvement
improvement
6 months of Assimilation Trials with:
Slide 9
EUMETSAT Fellow Day, 9 March 2015
FY-3C MWHS-2
Slide 10
MWTS
MWHS
MWRI
IRAS
MWTS-2
MWHS-2
IRAS
MWRI
GNOS
See Lu et al (2011a & b), Chen et al (2014).
FY-3B MWHS assimilated operationally since September 2014.
EUMETSAT Fellow Day, 9 March 2015
China’s FY-3 polar orbiting satellite series
FY-3A/B: launched 2008, 2012
FY-3C: launched Sep 2013
Slide 11
EUMETSAT Fellow Day, 9 March 2015
CMA
ECMWF UKMO
FY-3C collaboration
Qifeng Lu, et al
Bill Bell, Katie Lean, Nigel
Atkinson…
• Regular teleconferences, feeding back findings to CMA
• My focus: MWHS-2
Slide 12
EUMETSAT Fellow Day, 9 March 2015
FY-3C MWHS-2 study
Use a 6 month sample dataset to:
1. Assess data quality
2. Prepare for All-sky assimilation
Slide 13
EUMETSAT Fellow Day, 9 March 2015
• Keep all cloud-affected data
• Apply higher observation errors in cloudy regions
• Use an all-sky forward model RTTOV-SCATT
e.g. MHS channel 4 observations MHS channel 4 observation errors
All-sky Assimilation
All-sky Assimilation reference: Alan Geer et al (2014), ECMWF Tech. Memo 741:
http://old.ecmwf.int/publications/library/do/references/show?id=91235
AIM: Assimilate in all-sky conditions
Slide 14
EUMETSAT Fellow Day, 9 March 2015
MWHS-2 Instrument
5 183 GHz channels like ATMS (similar to MHS)
8 new 118 GHz channels
Slide 15
EUMETSAT Fellow Day, 9 March 2015
• 10:30 descending orbit
• 90 FOV (scan angles)
• Swath of 2700km
• Horizontal resolution 16 km (183 GHz) 32 km (118 GHz)
MetOp-B MHS
Suomi-NPP ATMS
FY-3C MWHS-2
MWHS-2 Instrument
Slide 16
EUMETSAT Fellow Day, 9 March 2015
MWHS-2 183 GHz channels
5 183 GHz channels
Slide 17
EUMETSAT Fellow Day, 9 March 2015
1. Compare Observations to ECMWF background
MWHS-2 Channel 13 Observation - Background
The main differences are cloud features
Slide 18
EUMETSAT Fellow Day, 9 March 2015
2. Compare to Other Instruments
MWHS-2 channel 13 ATMS channel 20
Maps of observation minus background look very similar…
Slide 19
EUMETSAT Fellow Day, 9 March 2015
mean(o-b) mean(o-b) stdev(o-b)
MW
HS
-2 c
ha
nn
el n
um
be
rMonthly mean and standard deviation of o-b
• Higher biases than ATMS and MHS
• Similar standard deviation
MWHS-2
ATMS all-sky
MHS all-sky
1 month, cloud-filtered
Mean before bias correction Mean after bias correction Standard deviation
window
channels
High
peaking
Low peaking
Slide 20
EUMETSAT Fellow Day, 9 March 2015
183 GHz Data Quality: Summary
• Higher global biases for some channels (14 and 15)
• Most bias removed by the ECMWF Variational Bias Correction Scheme
• Standard deviation of background departures similar to ATMS/MHS
Slide 21
EUMETSAT Fellow Day, 9 March 2015
Assimilation Trials for 183 GHz channels
Objective:
• Test the quality of the data in the full observing ECMWF
system
• Prepare for operational assimilation
Assimilation Trials:
1. Control: Full observing system T511 horizontal resolution
2. Full assimilation: Assimilate all 5 channels globally
Slide 22
EUMETSAT Fellow Day, 9 March 2015
Temperature: 1 – 2% change Vector Wind: 1 – 2 % change
Humidity: 1 – 5 % change
Assimilation Trial Results: Change in Analysis Increments
6 months data
Change in root mean square (12h forecast – analysis):
0.04
0.02
-0.02
-0.04
0.00
Slide 23
EUMETSAT Fellow Day, 9 March 2015
Change in short-range forecasts (12-hour)Improved fits to humidity observations:
AIRSIASI
ATMSMHS
improvementimprovement
improvementimprovement
Slide 24
EUMETSAT Fellow Day, 9 March 2015
Change in 1 – 10 day forecasts
No significant change to forecast scores:
improvement
degradation
e.g. geopotential and vector wind at 500hPa over Southern Hemisphere
Forecast Day Forecast Day
Nor
mal
ised
Diff
eren
ce
stde
v(fc
– a
n)
6 months data
Slide 25
EUMETSAT Fellow Day, 9 March 2015
Summary
Assimilating 183 GHz MWHS-2 channels over 6 months leads to:
• Increased increments of humidity, vector wind, temperature
• Improved fits of other observations to 12-hour forecasts (ATMS, IASI, AIRS)
• Neutral impact on forecast scores (days 1 – 10 forecasts)
Slide 26
EUMETSAT Fellow Day, 9 March 2015
FY-3C MWHS-2: 118 GHz channels
Slide 27
EUMETSAT Fellow Day, 9 March 2015
118 GHz:
• Oxygen band – Temperature sensitivity
• Water vapour continuum – Humidity sensitivity
• Cloud effects: absorption, emission, strong
scattering
MWHS-2 118 GHz channels
8 new 118 GHz channels
Slide 28
EUMETSAT Fellow Day, 9 March 2015
MWHS-2 118 GHz channel clear-sky Jacobians
• Channels 2 – 4: Temperature
• Channels 4 – 6: Temperature + cloud
• Channel 7: Temperature + cloud + humidity
Slide 29
EUMETSAT Fellow Day, 9 March 2015
Observation minus model background: Striping
STRIPING observed
MWHS-2 ch 3:
MetOp-B AMSU-A ch 9:ATMS ch 10 (unaveraged):1.4 K scale
5 K scale
2 K scale
Slide 30
EUMETSAT Fellow Day, 9 March 2015
Observation minus model background: cloud information6 K scale
16 K scale
channel 6
channel 7
Slide 31
EUMETSAT Fellow Day, 9 March 2015
Monthly mean observation minus background
Before bias correction After bias correction
MWHS-2
ATMS clear-sky
MetOp-B AMSU-A all-sky
All AMSU-A’s all-sky
1 month, filtered for cloud:
Slide 32
EUMETSAT Fellow Day, 9 March 2015
• Cloud-free Temperature information noisier than AMSU-A/ATMS
Monthly standard deviation of observation minus background
1 month, filtered for cloud:
Slide 33
EUMETSAT Fellow Day, 9 March 2015
3 month All-sky Assimilation Trials:
• Control
• Assimilate channels 2 – 7 over ocean
118 GHz First Assimilation Trials
Apply higher observation errors to cloud-affected data for channels 5 - 7:
Channel 7 observation error
Slide 34
EUMETSAT Fellow Day, 9 March 2015
Mostly neutral:
Small degradation of 1000hPa temperature:
Results: Impact on Forecast Accuracy
Work is still ongoing
Forecast day
Slide 35
EUMETSAT Fellow Day, 9 March 2015
MWHS-2 118 GHz channels: Summary
• New channels with temperature, humidity, cloud sensitivity
• Potential for additional cloud information
• Temperature information more noisy than AMSU-A, striping observed
• On-going experimentation with 118 GHz channels – attempting to use them
in all-sky (Will 4DVar be able to correctly adjust temperature, humidity
increments?)
Slide 36
EUMETSAT Fellow Day, 9 March 2015
Summary
Slide 37
EUMETSAT Fellow Day, 9 March 2015
AMSU-A:
• New Situation-dependent observation errors: AMSU-A channels 5 - 7
• Satellite-dependent observation errors: AMSU-A channels 5 – 13
• Introduced more data over orography and ocean for channels 5 - 8
• New observation errors and screening changes are implemented in CY41R2 with a
small positive impact on short-range forecasts
FY-3C MWHS-2:
• FY-3C MWHS-2 183 GHz data quality looks comparable to ATMS
• FY-3C MWHS-2 118 GHz channels have higher noise than AMSU-A but more cloud
information
Summary
Slide 38
EUMETSAT Fellow Day, 9 March 2015
Ongoing and Future work
• Monitor FY-3C MWHS-2 183 GHz channels and make operational (winter
2015?)
• Investigate further the usage of the new 118 GHz channels
Slide 39
EUMETSAT Fellow Day, 9 March 2015
Thank you for listening!
Any questions?