WAARSCHUWINGEN GEVAARLIJK WEER

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Validation of Cloud Top Temperature with CLOUDNET
cloud radar data during the BBC2 Period
Erwin Wolters (D. Donovan Presenting)
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Introduction

• Short outline of CTT satellite algorithm
• Used methods (satellite and ground data)
• Results
• Some cases
• Summary

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Satellite Cloud Top Temperature

• Emissivity is calculated
• Then, CTT is calculated

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BBC2 ground stations
NOAA16, April 24th 2003, 1201 UTC
Cabauw
Chilbolton
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Methods satellite data

• 44 NOAA16 and NOAA17 overpasses during April and
  May 2003
• Pixel area of 81 pixels around Chilbolton and
  Cabauw
• Cloud cover in pixel area gt 50
• Result 53 mean satellite CTT values

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Methods cloud radar data

• Cabauw 35 GHz cloud radar, sample time 15s
• Chilbolton 94 GHz cloud radar, sample time 30s
• Data in NET-CDF format
• Averaging time for Cloud Top Height 30 min

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Methods cloud radar data (2)

• Cloud cover gt 50.
• Time period centered on satellite overpass
• 53 mean Cloud Top Height values

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Methods cloud radar data (2)
Satellite overpass
Chilbolton
Cabauw
April 24th 2003, 1201 UTC, NOAA16 (left), cloud
radar Cabauw (right)
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ECMWF model data

• Cloud Top Height Cloud Top Temperature
• Only sounding data of de Bilt
• Use of ECMWF model data allowed?
• Model temperatures vs sounding temperatures

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ECMWF data vs sounding data
Correlation0.9916
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Results (1)
Correlation0.7497
28-4-2003,945, CA
24-4-2003,1201,CA
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Results (2) Cases with ?sattgt5
Correlation0.8437
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Ice clouds April 24th and 28th 2003
Satellite overpass
Satellite overpass
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Brightness temperature differences

• BTD10.8-11.9 calculated for each pixel
• 81 pixel values for each case
• Plotted against
• 1) pixel values of ?.
• 2) pixel values of temperature 10.8?m
• Are cases separated?

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BTD vs ?
?1.3?
?9.6
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BTD vs T10.8 ?m
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BTD10.8?m-11.9?m?
Cabauw
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Summary/conclusions

• CPP algorithm works good
• Weakness - optically thin cases
• - clouds containing ice
• BTD10.8-11.9 for detecting ice clouds
• Possible tool for improvement of algorithm
• However, further research needed

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Thanks for the attention
any questions?