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The SMHI AVHRR & Cloud Type dataset for CNN-I/II & BBC Adam Dybbroe The AVHRR dataset Navigation, Coverage, Re-mapping, Resolution The Cloud Type product.

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Presentation on theme: "The SMHI AVHRR & Cloud Type dataset for CNN-I/II & BBC Adam Dybbroe The AVHRR dataset Navigation, Coverage, Re-mapping, Resolution The Cloud Type product."— Presentation transcript:

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2 The SMHI AVHRR & Cloud Type dataset for CNN-I/II & BBC Adam Dybbroe The AVHRR dataset Navigation, Coverage, Re-mapping, Resolution The Cloud Type product Cloud cover products for model intercomparison Post-processing to lower resolution Mean cloud cover maps Data around sites Comparing Cloud Type to surface observations...or what I would like to do if I had time...

3 Satellite overpass times CNN-I NOAA14: * NOAA12: x

4 Satellite overpass times CNN-II NOAA16: o NOAA15: + NOAA14: * NOAA12: x

5 Satellite overpass times BBC NOAA16: o NOAA15: + NOAA14: * NOAA12: x

6 Navigation Automatic Navigation Adjustment using ANA (©Météo-France) Applied during CNN-II and BBC NOAA 16 ANA estimates the “true” satellite attitude (yaw-roll-pitch) using: An image deformation model Automatic adjustment on coastal landmarks

7 Navigation Navigation errors: NOAA 16 CNN-I: Usually around 3- 5 km. Ocassionally up to ~10 km. CNN-II: ~1-2 km BBC: ~1-2 km

8 Regional domains Resolution CNN-I: 1000 m CNN-II: 1100 m BBC: 1100 m Projection: Aziumthal Equal Area Resampling: Nearest Neighbour

9 The AVHRR Cloud Type Multispectral dynamic grouped thresholding approach Cloud Mask thresholds derived using RTM simulations of the AVHRR signal assuming cloud free but otherwise similar conditions Separation of opaque and semi- transparent & sub-pixel clouds using IR split-window feature Opaque clouds divided according to the cloud top temperature using NWP short range forecasts.

10 Mean error and standard deviation - all data (34 months from 1998 to 2001): N=146963 Cloud Type quality Mean error & STDV

11 Inland Coast Cloud Type quality Inland versus coastal conditions:

12 Which Cloud types are potentially raining? All cloudfree typesP(rain) < 2.6 % Very low cloudsP(rain) = 2.1 % Low cloudsP(rain) = 5.5 % Medium level cloudsP(rain) = 21.2 % High opaque cloudsP(rain) = 38.9 % Very high opaque cloudsP(rain) = 47.0 % Very thin cirrusP(rain) = 4.9 % Thin cirrusP(rain) = 8.4 % Thick cirrusP(rain) = 11.1 % Cirrus over lower cloudsP(rain) = 16.5 % Fractional cloudsP(rain) = 3.5 % (1 year of collocated BALTRAD data and NOAA 15 AVHRR) Cloud Type quality

13 Known problems: Misses small cumuli and thin cirrus over land (especially wintertime) Sometimes low clouds at twilight go undetected – especially a problem in situations with a low level temperature inversion Misses arctic low clouds at night in wintertime (ice contamination or big water droplets) Ambiguous separation between thin cirrus and small cumuli and cloud edges: Often small cumulus and edges of water clouds are classified as thin cirrus Thin cirrus over mid-level or low cloud may be mis- classified as mid-level (opaque) cloud Sunglint may be classified as low or very low stratus

14 BBC: NOAA 15, 4 August 2001, 16:59 UTC Cloud Type RGB: Channel 1,2,4 Cloud Type quality Example:

15 Cloud Type quality BBC: NOAA 15, 4 August 2001, 16:59 UTC Example:

16 Cloud Type post-processing - for model validation: Cloud Type – 1.1 km resolution Frequency of cloud type - 11 km resolution Post-processing

17 Mean Cloudiness CNN-I 0 20 40 60 80 100 Mean cloud cover – August, 2000 156 scenes - Average time = 09:46 UTC Total cloud coverIce cloudsWater clouds

18 Mean Cloudiness CNN-I 0 20 40 60 80 100 Mean cloud cover – September, 2000 101 scenes - Average time = 11:40 UTC Total cloud coverIce cloudsWater clouds

19 Mean Cloudiness CNN-I 0 20 40 60 80 100 Morning versus afternoon cloud cover – August, 2000 MorningAfternoon

20 Mean Cloudiness CNN2 0 20 40 60 80 100 Mean cloud cover - April, 2001 318 scenes - Average time = 09:19 UTC Total cloud coverIce cloudsWater clouds

21 Mean Cloudiness CNN2 0 20 40 60 80 100 Mean cloud cover - May, 2001 363 scenes - Average time = 09:45 UTC Total cloud coverIce cloudsWater clouds

22 0 20 40 60 80 100 Diurnal cloud cover: Total - May, 2001 66 scenes: 23-04 UTC - Average = 02:04 UTC Night 122 scenes: 04-10 UTC - Average = 06:26 UTC MorningAfternoon 104 scenes: 10-15 UTC - Average = 12:48 UTC Evening 71 scenes: 15-20 UTC - Average = 16:48 UTC Mean Cloudiness CNN2

23 0 20 40 60 80 100 Diurnal cloud cover: Water clouds - May, 2001 66 scenes: 23-04 UTC - Average = 02:04 UTC Night 122 scenes: 04-10 UTC - Average = 06:26 UTC MorningAfternoon 104 scenes: 10-15 UTC - Average = 12:48 UTC Evening 71 scenes: 15-20 UTC - Average = 16:48 UTC Mean Cloudiness CNN2

24 0 20 40 60 80 100 Diurnal cloud cover: Ice clouds - May, 2001 66 scenes: 23-04 UTC - Average = 02:04 UTC Night 122 scenes: 04-10 UTC - Average = 06:26 UTC MorningAfternoon 104 scenes: 10-15 UTC - Average = 12:48 UTC Evening 71 scenes: 15-20 UTC - Average = 16:48 UTC Mean Cloudiness CNN2

25 0 20 40 60 80 100 Diurnal cloud cover: Total - April-May, 2001 130 scenes: 23-04 UTC - Average = 02:11 UTC Night 216 scenes: 04-10 UTC - Average = 06:12 UTC MorningAfternoon 207 scenes: 10-15 UTC - Average = 12:47 UTC Evening 128 scenes: 15-20 UTC - Average = 16:32 UTC Mean Cloudiness CNN2

26 0 20 40 60 80 100 Diurnal cloud cover: Total – August, 2001 NightMorningAfternoonEvening 47 scenes: 23-04 UTC - Average = 02:09 UTC 80 scenes: 04-10 UTC - Average = 05:35 UTC 57 scenes: 10-15 UTC - Average = 12:53 UTC 51 scenes: 15-20 UTC - Average = 16:10 UTC Mean Cloudiness BBC

27 0 20 40 60 80 100 Diurnal cloud cover: Total – September, 2001 NightMorningAfternoonEvening 48 scenes: 23-04 UTC - Average = 02:05 UTC 82 scenes: 04-10 UTC - Average = 05:46 UTC 49 scenes: 10-15 UTC - Average = 12:53 UTC 40 scenes: 15-20 UTC - Average = 16:05 UTC Mean Cloudiness BBC

28 0 20 40 60 80 100 Diurnal cloud cover: Water/Ice clouds – August, 2001 NightMorningAfternoonEvening Mean Cloudiness BBC Water clouds Ice clouds

29 Cloud Type around sites 20010801 01 18 0.50 0.50 0.00 99.50 0 0.00 20010801 02 58 90.63 90.63 0.00 9.38 0 86.88 20010801 04 18 9.50 9.50 0.00 90.50 0 6.00 20010801 05 22 69.25 69.00 0.25 30.75 0 65.50 20010801 05 59 51.63 44.88 6.75 48.38 0 37.38 20010801 06 41 53.75 50.75 3.00 46.25 0 40.25 20010801 11 10 64.00 59.00 5.00 36.00 0 47.00 20010801 12 51 83.13 80.13 3.00 16.88 0 61.38... YYYYMMDD HH MM Total Water Ice Cl-free NoP Mixed Water clouds: Very Low + Low + Medium Fractional (50%) Ice clouds: High + Very high + 4 cirrus classes Mixed phase clouds: Medium + Very thin cirrus + Thin cirrus Fractional (50%)

30 Frequency of cloud types inside a 20 by 20 pixel box (22kmx22km for BBC&CNN-II) around sites: Cloud Type around sites Around Cabauw, 31/7-5/8, 2001

31 Cloud Type around sites Frequency of cloud types inside a 5 by 5 pixel box around sites: Cabauw, 31/7- 5/8, 2001

32 # AVHRR Cloud Type # Cabauw # Column 1: YYYYMMDD # Column 2: HH (hour) # Column 3: MM (minutes) # Column 4: nonproc # Column 5: cloudfree_land # Column 6: cloudfree_sea # Column 7: snowice_land # Column 8: snowice_sea # Column 9: verylow # Column 10: low # Column 11: medium # Column 12: high_opaque # Column 13: veryhigh_opaque # Column 14: verythin_cirrus # Column 15: thin_cirrus # Column 16: thick_cirrus # Column 17: cirrus_above # Column 18: fractional # Column 19: unclass # Column 21->: (ClassN_0,Frequency0),(ClassN_1,Frequency1)... EOH 20010801 01 18 0 21 4 0 0 0 0 0 0 0 0 0 0 0 0 0 # 1 21 2 4 20010801 02 58 0 21 4 0 0 0 0 0 0 0 0 0 0 0 0 0 # 1 21 2 4 20010801 04 18 0 21 4 0 0 0 0 0 0 0 0 0 0 0 0 0 # 1 21 2 4 20010801 05 22 0 21 4 0 0 0 0 0 0 0 0 0 0 0 0 0 # 1 21 2 4 20010801 05 59 0 3 0 0 0 0 8 8 0 0 0 0 0 0 6 0 # 6 8 7 8 14 6 1 3 20010801 06 41 0 0 0 0 0 0 23 0 0 0 0 0 0 0 2 0 # 6 23 14 2 20010801 11 10 0 0 0 0 0 0 14 8 0 0 0 0 0 0 3 0 # 6 14 7 8 14 3 20010801 12 51 0 6 0 0 0 5 0 0 0 0 9 0 0 0 5 0 # 10 9 1 6 5 5 14 5 20010801 15 09 0 20 4 0 0 0 0 0 0 0 1 0 0 0 0 0 # 1 20 2 4 10 1 20010801 15 51 0 21 4 0 0 0 0 0 0 0 0 0 0 0 0 0 # 1 21 2 4 20010802 05 47 0 14 0 0 0 0 0 11 0 0 0 0 0 0 0 0 # 1 14 7 11 20010802 07 58 0 0 0 0 0 0 0 7 0 0 14 0 0 4 0 0 # 10 14 7 7 13 4 20010802 12 40 0 0 0 0 0 0 0 0 16 0 0 0 1 8 0 0 # 8 16 13 8 12 1 20010802 14 45 0 6 0 0 0 0 1 0 0 0 15 0 1 0 2 0 # 10 15 1 6 14 2 6 1 12 1

33 Cloud Type around sites Cabauw 31/7-5/8 5.5x5.5k m 22x22km

34 BBC – Chilbolton – Diurnal cycle Diurnal variation at sites September August

35 BBC/August – Chilbolton – Diurnal cycle Water clouds Ice clouds Diurnal variation at sites

36 BBC/August – Palaiseau – Diurnal cycle Diurnal variation at sites All cloudsWater clouds Ice clouds

37 Around Cabauw Sea/Coast North of Cabauw Inland South of Cabauw Land versus Sea (coast): Diurnal variation at sites BBC - August 2001

38 Potential future intercomparison studies Using first of all ground based Radar products (cloud mask): Quantify the “underdetection” of thin cirrus and sub-pixel (small cumulus) clouds over land Quantify the “overlap” or mis-match of fractional and thin cirrus Validate the thin cirrus versus opaque separation Validate the Nowcasting SAF cloud top temperature and height retrieval...

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