Comparison of LM Verification against Multi Level Aircraft Measurements (MLAs)
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Transcript of Comparison of LM Verification against Multi Level Aircraft Measurements (MLAs)
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Comparison
ofLM Verification against Multi Level Aircraft Measurements (MLAs)
with LM Verification against Temps
Ulrich Pflüger, Deutscher Wetterdienst
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Comparisonof
LM Verification against Multi Level Aircraft Measurements (MLAs)with LM Verification against Temps
• by means of Time Series (June 2001 until May 2003) of monthly average of – bias and rmse of 00h, 24h, 48h Forecasts based on all MLAs/Temps in
LM area
– Variables are• temperature
• wind velocity
• wind direction
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Multi Level Aircraft Measurementsare
• Several (not less than 4) single Aircraft Measurements during the climb or descent flight
• which are piecewise combined– beginning with the lowest
– next < 20 km horizontal distance of the first
– vertical distance < 55 hPa
– etc.
• and then used like a Temp Measurement
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LM Area
All MLAs at 12 UTC
2003/05/01-2003/05/19
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LM Area
All Temps Stations
12 UTC
2003/05/01-2003/05/19
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Bias of LM-Temperatureagainst
MLA Temps
00 UTC
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Analysis Analysis
24 h Forecast 24 h Forecast
48 h Forecast 48 h Forecast
small bias, similar structures in both cases
Forecasts have annual cycle, in upper and middle tropospherepositive bias in Summer, negative in Winter, near ground predominantly negativ bias
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RMSE of LM-Temperatureagainst
MLA Temps
00 UTC
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1.41.6
1.61.4
2.22.01.8 2.0
similar structures in both cases
0.8 0.8
similar structures in both cases, rmse(Temps) overall about 0.2 K greater than rmse(MLA)
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Bias of LM-Temperatureagainst
MLA Temps
12 UTC
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Negative bias> -0.3 K
positiv bias< 0.4 K
below 800 hPApredominantly negativ,
below 800 hPApredominantly negativ
below 800 hPASummer negativ,Winter positiv
below 800 hPASummer negativ,Winter positiv
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RMSE of LM-Temperatureagainst
MLA Temps
12 UTC
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1.41.6
1.61.4
2.22.01.6 1.8
Same as 00 UTC
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Differences at Temperature Verification
• Relative few differences between Verification based on MLAs and Temps
• When bias is small there is predominantly a negative bias against MLAs and a positive bias against Temps
• Overall rmse of 24/48 h Forecast is about 0.2 K greater in Verification based on Temps
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Bias of LM-Wind Velocityagainst
MLA Temps
00 UTC
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Below 800 hPa, annual cycle, in winter strong positive bias Max.: 1.4 m/s
Below 800 hPa , annual cycle, in winter strong positive bias Max.: 1.8 m/s
Below 800 hPa , annual cycle, in winter strong positive bias Max.: 1.8 m/s
Below 900 hPa predominantly negative bias Min.: -1.1 m/s, Winter less
Below 900 hPa predominantly negative bias Min.: -0.8 m/s, Winter partly positive Max 0.2 m/s
Below 900 hPa predominantly negative bias Min.: -0.8 m/s, Winter partly positiv Max 0.2 m/s
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RMSE of LM-Wind Velocityagainst
MLA Temps
00 UTC
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Overall rmse(MLA) is about 0.5-1 m/sgreater than rmse(Temps)
Overall rmse(MLA) is equalto rmse(Temps)
Above 400 hPa rmse(Temps) is greaterthan rmse(MLA)
3.5 3 3.5 3
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Bias of LM-Wind Velocityagainst
MLA Temps
12 UTC
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Below 800 hPa, annual cycle, in winter strong positive bias, Max.: 1.9 m/s
Below 800 hPa , annual cycle, in winter strong positive bias, Max.: 2.4 m/s
Below 800 hPa , annual cycle, in winter strong positive bias, Max.: 2.3 m/s
Below 900 hPa predominantly negative bias Min.: -1.1 m/s,Winter partly positive, Max.: 0.2 m/s
Below 800 hPa Summer negative bias Min.: -0.6 m/s, Winter positive, Max 0.7 m/s
Below 800 hPa Summer predominantly negative bias Min.: -0.6 m/s, Winter predominantly positive, Max 0.8 m/s
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RMSE of LM-Wind Velocityagainst
MLA Temps
12 UTC
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3 2
4 3 4 3
Same as 00 UTC
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Differences at Wind Velocity Verification
• bias with annual cycle– below 800 hPa
• positive against MLA
• negativ(Winter) to slight positive(Summer) 00 UTC
• negativ(Winter) to positive(Summer) 12 UTC
• rmse with annual cycle – at Analysis overall 0.5 -1 m/s higher against MLA
(wind is nudged to Temps)
– at Forecasts higher rmse against Temps above 400 hPa
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Bias of LM-Wind Directionagainst
MLA Temps
00 UTC
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Below 800 hPa, strong positive bias Max.: 7.4 degree, smaller in spring and autumn
Below 800 hPa, strong positive bias Max.: 10.3 degree
Below 800 hPa, strong positive bias Max.: 13.5 degree
Below 900 hPa negative bias Min.: -4.9 degree, Winter less
Below 900 hPa predominantly negative bias Min.: -7 degrees, Winter partly positive Max.: 6 degrees
Below 900 hPa predominantly negative bias Min.: -10 degrees, Winter partly positiv Max 6 degrees
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RMSE of LM-Wind Directionagainst
MLA Temps
00 UTC
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20
30 30
40 40
10
Overall rmse(MLA) is about 5-10 degreesgreater than rmse(Temps)
Overall rmse(MLA) is equalto rmse(Temps), except Summer
Above 400 hPa rmse(Temps) is partly greater than rmse(MLA)
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Bias of LM-Wind Directionagainst
MLA Temps
12 UTC
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Below 800 hPa, strong positive bias Max.: 6.1 degree, smaller as 00 UTC
Below 800 hPa, strong positive bias Max.: 10.1 degree
Below 800 hPa, strong positive bias Max.: 10.6 degree, smaller than 00 UTC
Below 900 hPa Winter negative bias Min.: -4.1 degree, Summer positive
Below 900 hPa predominantly positive Max.: 8 degrees, Winter smaller or negative
Below 900 hPa predominantly positive, Max.: 9 degrees, single months in winter positive
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RMSE of LM-Wind Directionagainst
MLA Temps
12 UTC
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Overall rmse(MLA) is about 5-10 degreesgreater than rmse(Temps)
Below 400 hPa rmse(MLA) is equalto rmse(Temps) except Summer
Above 400 hPa rmse(Temps) is partly greater than rmse(MLA)
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Differences at Wind Direction Verification
• bias with annual cycle– below 800 hPa
• Analysis and Forecast against MLAS strong positive
• Analysis against Temps slight negative below 900 hPa, slight positve above against Temps
• Forecasts against Temps partly slight negativ(Winter) to slight positive(Summer) 12 UTC
• rmse with annual cycle – at Analysis overall 5 -10 degrees higher against MLA (wind is
nudged to Temps)– at Forecasts higher rmse against Temps above 400 hPa– at Forecasts higher rmse against MLA in Summer
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Summary
• Temperature Verification shows only few differences between the two measuring systems
• Wind Verification shows below 800 hPa great differences between the two measuring systems
• Regarding the Wind Verification results up to now (Synop, Temp) LM is more likely to underestimate wind velocity
• Regarding the verification against aircraft measurements it seems that aircraft measurements below 800 hPa underestimate wind velocity (up to 2 m/s in the boundary layer).