1. Satellite based instability indices for very short range forecasting of convection Estelle de Coning South African Weather Service Contributions from Marianne Koenig (EUMETSAT) 1

2. Content EUMETSAT MPEF products Satellite based instability indices (GII) GII validated over SA Summary 2

3. EUMETSAT MPEF (Meteorological Products Extraction Facility) MPEF is part of the the source of the Meteorological Products provided by the MSG system The list of products to be extracted from the MSG imagery has been agreed by EUMETSAT member states As a general principle, the MPEF will extract products on a synoptic scale (< 100 km) 3

4. Radiative Transfer Model (RTM) SCE (scenes analysis) Cloud Aanalysis int Satellite Model Data AMVCLACSR THTOZHPI CTH GII Algorithm Overview 4

5. MSG MPEF Products Baseline (distributed via GTS/EUMETCast/UMARF) Atmospheric Motion Vectors (AMV) Calibration Monitoring (CAL-MON) Clear Sky Radiance (CSR) Clear Sky Reflectance Map (CRM) Climate Data Set (CDS) Cloud Analysis (CLA) Cloud Top Height (CTH) Global Instability Index (GII) ISCCP Dataset (IDS) Precipitation Index (PI) Total Ozone (TOZ) Tropospheric Humidity (TH) Some internal Products: Sea Surface temperature (SST) Scenes Analysis (SCE) Radiative Transfer Model (RTM) 5

6. Atmospheric instability: Using upper air ascents Traditionally, these indices are taken from temperature and humidity soundings by radiosondes. Instability indices are calculated using the vertical profile of moisture and temperature 6

7. Atmospheric instability: Using NWP Since numerical weather prediction models can forecast these factors of the atmosphere, they can forecast the instability as well.

8. Atmospheric instability: The Global Instability Index (GII) As radiosondes are only of very limited temporal and spatial resolution there is a demand for satellite-derived indices which can provide the information every 15 minutes! The basis of the GII methodology is: –Together with the satellite measured brightness temperatures and some a priori information of the atmospheric profile (from the Numerical Weather Prediction model) a local profile is derived, and instability indices are computed from this local profile. 8

9. History – USA and GOES A global (Meteosat) coverage of instability information (GII = Global Instability Indices) satellite product was one of the drivers of the channel definition on MSG Heritage: Similar products from the GOES Sounder, provided by CIMSS (Univ. Wisconsin) Shades of brow  stable air Blue to yellow to red  increasing instability 9

10. MSG Channels 1 = VIS0.62=VIS0.83=NIR1.612=HRV 4=IR3.95=WV6.26=WV7.37=IR8.7 8=IR9.79=IR10.810=IR12.011=IR13.4 12 available channels on MSG, 4 in the solar spectral range (VIS), 8 in the infrared (IR) 10

11. MSG channels we cannot use for a vertical profile of temperature and humidity 1 = VIS0.62=VIS0.83=NIR1.612=HRV 4=IR3.95=WV6.26=WV7.37=IR8.7 8=IR9.79=IR10.810=IR12.011=IR13.4 No temperature/humidity information in solar channels Temperature information in IR3.9 mixed with solar contribution (during daytime) Too much ozone information in IR9.7 11

12. MSG channels useful for a vertical profile 5=WV6.26=WV7.37=IR8.7 9=IR10.810=IR12.011=IR13.4 Humidity information in various levels 12

13. MSG Information Content 5=WV6.26=WV7.37=IR8.7 9=IR10.810=IR12.011=IR13.4 Humidity information in various levels Information on surface temperature 13

14. MSG Information Content 5=WV6.26=WV7.37=IR8.7 9=IR10.810=IR12.011=IR13.4 Humidity information in various levels Information on surface temperature Information on mid-level air temperature 14

15. Retrieval Concept (1) From NWP: Forecast temperature and humidity profile: T(p), q(p) 15

16. Retrieval Concept (1) From NWP: Forecast temperature and humidity profile: T(p), q(p) Expected MSG brightness temperatures in 6 channels TB (MSG) Radiative transfer model 16

17. Retrieval Concept (1) From NWP: Forecast temperature and humidity profile: T(p), q(p) Expected MSG brightness temperatures in 6 channels TB (MSG) Radiative transfer model Compare with measurements TB(NWP) – TB(MSG) : The temperature differences are used to change the initial profile, T n (p), q n (p) 17

18. Retrieval Concept (1) Updated temperature and humidity profile: T n (p), q n (p) Expected MSG brightness temperatures in 6 channels TB (MSG) Radiative transfer model Compare with measurements TB TB(NWP) – TB(MSG) : The temperature differences are used to change the initial profile 18

19. Retrieval Concept (1) In every iteration of this process we check: Is (TB(NWP) – TB(MSG)) small? If yes, the process is stopped and the last profile is taken as the “best” solution 19

20. MSG channels 5,6,( WV) 7,9,10 and 11 (IR) are currently used for calculations The GII product consists of a set of instability indices which describe the layer stability of the atmosphere: –K index, –Lifted Index, –Precipitable Water –KO Index –Maximum Buoyancy The retrieval of these parameters from satellite data is only possible under cloud-free conditions. 20

21. 21

22. > 0Thunderstorms unlikely 0 - -2Thunderstorms possible – triggered needed -3 - -5Thunderstorms probable -5 - -7Strong/severe thunderstorms. Tornadoes possible Lifted Index Sturtevant (1995)

23. 0 – 15No thunderstorms 16 – 19Thunderstorms unlikely 20 – 25Isolated thunderstorms 26 – 29Widely scattered thunderstorms 30 – 35Numerous thunderstorms 36 – 39Thunderstorms very likely 40+100% chance of thunderstorms Sturtevant (1995) K-Index

24. MSG MPEF Product: Global Instability Index (GII) example of PW 10 16 14 16 12 34 41 14 15 13 21 13 52 59 35 Example of a total precipitable water retrieval, co-located radiosonde observations are also shown 24

25. K Index for 08:45 UTC on 6 Nov 2005 from GII product

26. MSG Convection RGB (Ch5-6,Ch4-9,Ch3-1) at 14:42 UTC on 6 Nov 2005

27. CASEPODFARatioACCURACY 15 Jan 20070.470.310.63 16 Jan 20070.910.420.65 17 Jan 20070.730.330.70 28 Dec 20060.830.210.81 4 Mar 20070.930.380.71 6 Oct 20070.480.040.76 6 Nov 20071.00.130.9 4 Jan 20080.880.320.74 AVERAGE0.780.270.74 GII : Evaluation against lightning data: K index

28. Summary Satellite based instability indices make it possible to say something about atmospheric stability/instability for thunderstorm forecasting in areas where upper air ascents are not available Combining the vertical profile of the satellite data (using 6 channels) with the NWP profile, adds observation data (from satellite) to the NWP fields Satellite instability indices can be calculated every 15 min (MSG) Data sources should always be used to complement one another and not to replace one another. 28