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TAMDAR Data Characteristics

Bill Moninger, Stan Benjamin, Tracy Smith*, Brian Jamison*, Ed Szoke*, Tom

Schlatter, Randy Collander*

NOAA / ESRL / Global Systems Division

* also affiliated with CIRA

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Our TAMDAR verification tool: the RUC

• RUC: Rapid Update Cycle• Used operationally at NCEP• Multiple versions run at GSD

– hourly cycle time– 20 km grid (13 km at NCEP)– ingests many kinds of asynoptic data

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A Detailed look at TAMDAR/AMDAR, compared with the RUC model

The following plots show:• Differences between observations and RUC 1h forecasts

interpolated to the location of the observations• We use the RUC forecast valid at the nearest hour to the

time of the observation.• We include more data than what passes RUC QC• Two models are used, as appropriate

– ‘dev’ does not include TAMDAR. This is used in TAMDAR time histories

– ‘dev2’ includes TAMDAR. Used when we’re comparing TAMDAR with other airlines

– otherwise, both ‘dev’ and ‘dev2’ are identical

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Temperature (last summer, and in Jan)

Best current TAMDAR sensors* compared against the “dev” model.

* GSD TAMDAR ID’s: 5519,5527,5552,5602,5605,7010,7159,8669,

8671,8678,8679

Ascent-Descent bias differences have

been much reduced

Overall bias reduced above 900 mb

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Temperature bias (April 2006)

All TAMDAR sensors compared against the “dev”

model.

Green (“er”) shows either en-

route or an unrecognized

sounding

Good improvement in temperature bias at

all levels

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Temperature bias (TAMDAR minus dev) time history (all altitudes)

All TAMDAR sensors compared against the “dev”

model, 10-day averages.

Very good performance in

April.

The dev is not perfect, of course.

For 1 h fcst, 850 - 500 mb, 0 UTC, bias w.r.t. RAOBs is recently between -0.1°C and -0.2°C

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TAMDAR compared with AMDAR jetsAll TAMDAR sensors

compared with traditional AMDAR jets in the TAMDAR

time and space region:

lat: 37N to 49Nlon: 79W to 101Whour: 12 to 03 UTC

Using ‘dev2’ model to be fair to all airlines.

TAMDAR T Bias now generally as good

as AMDAR jets (except low-level

ascents).

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rms Vector Wind difference time history (all altitudes)

All TAMDAR sensors compared against the ‘dev’ model, 10-day

averages.

Slowly improving descent wind

error characteristics

On March 8, AirDat started

flagging descent winds above

10 Kft.

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rms Vector Wind difference with dev2 (Jan.)

Best current TAMDAR sensors compared

with traditional AMDAR (jet aircraft) in TAMDAR time and

space region.

TAMDAR Winds are worse than the traditional fleet, particularly on

descent

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rms Vector Wind difference with dev2 (April)

All TAMDAR sensors compared with AMDAR jets in

TAMDAR time and space region

TAMDAR Ascent Winds have

improved; not much change in descent winds in spite of AirDat’s

new flagging scheme.

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RH Bias, Last Aug and January

Best current TAMDAR sensors compared with

the ‘dev’ model.

Includes all obs with RH Uncertainty < 49%

RH Bias on ascent was worse in

January than last August

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RH Bias, this April

RH Bias on ascent is much improved

since January, and descent is about the

same.

Best current TAMDAR sensors compared with

the ‘dev’ model.

Includes all values of RH Uncertainty < 49%

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RH Bias time history, all altitudes (TAMDAR minus dev)

All sensors compared against the “dev” model, 10-day averages.

RH Bias for all flight phases has

improved recently. All phases at about

+1.5%

Current dev bias for 1h fcst. w.r.t. RAOBs

at 850-500 mb, 0 UTC

is about -0.5%

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RH RMS Error time history, all altitudes

All TAMDAR sensors compared against the ‘dev’

model.

RH RMS for en-route is higher, not surprisingly.

For ascent/descent RH RMS is currently

~13%

Current dev RH RMS w.r.t. RAOBs at

850-500 mb, 0 UTC, is ~15%

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Possible reasons for recent improvement

• AirDat temperature sensor lag compensation

• AirDat RH improvements– replacement of suspect sensors– reorientation of outboard RH sensor

• AirDat flagging of upper level descent winds(?)

• Climatology? (warmer in April)

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Summary: TAMDAR Error Characteristics

• TAMDAR data have improved considerably since January.• Temperature

– Biases are now generally commensurate with AMDAR jets– RMS errors are worse than AMDAR jets

• Wind– Ascent wind errors have recently improved– Descent wind errors are slowly improving– Removal of upper level descent winds does not seem to make much

difference

• Relative Humidity– Bias is now within +/- 5% at all levels– RMS is commensurate with RAOBS

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Possible future work at GSD (1)

• Institute automated reject list updating• Evaluate effect of improved vertical resolution• Improve the RUC-AMDAR database

– to include more detailed reject information

• Perform case studies of notable events• Perform OSE’s (not to be confused with OSSE’s)

– to compare different RH errors– to compare different vertical resolutions– to compare different reject criteria

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Possible future work at GSD (2)

• Evaluate TAMDAR on new fleets– next generation TAMDAR sensor– multiple platform types (possibly 7 in the

near term)– higher altitudes and speeds

• Codify our evaluation strategies– to form a basis for operational data

acceptance criteria

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Questions?

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RUC ‘dev’/’dev2’ time history (1)• 9 Feb 2005

– matched the ‘dev’ and ‘dev2’ cycles

• 4 March 2005– profiler-related changes

• 8 June 2005– new aircraft reject list– separate lists for W, T, and RH– (injected an occasional T bug when T is missing from an

observation but W exists)

• 21 June 2005– attempt to fix occasional T bug above

• 26 July 2005– correct fix of T bug above

• 1 Sept 2005– updated aircraft reject list

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• 13 Sept 2005– New moisture analysis, to match 13km operational RUC

• 3 Nov. 2005– New aircraft reject list installed

• 15 Nov. 2005– Reject obs if ob-background difference is too large

• 1 Dec. 2005– Change aircraft moisture characteristic from 4% to 10% to

match RAOB characteristic

• 15 Dec. 2005– reject winds from TAMDAR obs that are part of a identified

descent soundings

RUC dev/dev2 time history (2)

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• 14 Feb 2006– Increased aircraft moisture error characteristic from 10% to 12%

• 8 March 2006– (AirDat started eliminating upper level descent winds)

• 15 March 2006– Correctly read GSD QC flags. But started accepting all RH obs with

uncertainty < 49% when wind and/or temperature are QC-flagged as bad.

• 22 March 2006– Accept all RH with RH uncertainty < 29%. (But error above

remained.)

• 28 March 2006– AirDat starts high-vertical-resolution data

• 31 March 2006– Reverted to pre 15 March 2006 code.

RUC dev/dev2 time history (3)