Tephigrams for Dummies

1. Tephigrams for Dummies An introduction NEXT

2. Introduction to Tephigrams Te phi gram “T” is the symbol used for Temperature “Phi” φis the symbol used for pressure “gram” means graph (Invented by Napier Shaw in 1915) NEXT NEXT NEXT NEXT NEXT NEXT

3. Introduction to Tephigrams Temperature normally reduces with height. But not always Pressure NEXT NEXT NEXT Temperature

4. Introduction to Tephigrams Air Pressure REDUCES with altitude Lower pressure Pressure Higher Pressure NEXT NEXT Temperature

5. Introduction to Tephigrams Lower pressure Pressure ALTITUDE Higher pressure NEXT NEXT Temperature

6. Introduction to Tephigrams Bronze C question The surface temperature is 20°C, The Environmental Lapse Rate (ELR) is 2°C/1000ft. Trigger temperature is 24°C. The Dry Adiabatic Lapse Rate (DALR) is 3°/1000ft. How High will the thermals go? NEXT

7. Introduction to Tephigrams ENVIRONMENTAL LAPSE RATE 2°C/1000ft 7000ft But this is idealised---In reality the ELR is never a steady reduction like this 6000ft 5000ft 4000ft ALTITUDE 3000ft 2000ft TEMPERATURE 1000ft NEXT NEXT NEXT NEXT 10°C 20°C

8. Introduction to Tephigrams ACTUAL or FORECAST SOUNDING 7000ft It is far more usual to see it like this. 6000ft 5000ft 4000ft OR THIS 3000ft 2000ft 1000ft NEXT NEXT NEXT NEXT 10°C 20°C

9. Introduction to Tephigrams Adiabatic Heating and Cooling of a parcel of air As air is compressed it gets warmer As air expands it also cools Warmer cooler NEXT NEXT NEXT NEXT NEXT NEXT

10. Introduction to Tephigrams Air pressure decreases with Altitude If a parcel rises, it expands in the lower pressure above It cools adiabatically NEXT NEXT NEXT

11. Introduction to Tephigrams • In this context, if air has not cooled to its Dew point, it is considered to be dry. • The Dry Adiabatic Lapse Rate (DALR) is 3°C/1000ft • Air below its Dew Point temperature is saturated. • The Saturated Adiabatic Lapse rate (SALR) is approximately 1.5°C/1000ft. NEXT NEXT NEXT NEXT NEXT

12. Introduction to Tephigrams When shown on our graph these lines look like this 7000ft 6000ft DALR≈ 3°/1000ft SALR≈ 1.5°C/1000ft 5000ft 4000ft 3000ft 2000ft 1000ft NEXT NEXT 10°C 20°C

13. Introduction to Tephigrams Remember our question? The surface temperature is 20°C, The Environmental Lapse Rate (ELR) is 2°C/1000ft. Trigger temperature is 24°C. The Dry Adiabatic Lapse Rate (DALR) is 3°/1000ft. How High will the thermals go? NEXT

14. 24°C Introduction to Tephigrams Environmental air temp The Sun heats the ground Surface temperature is 20°C 7000ft 6°C The environmental Lapse rate is 2°C/1000ft 6000ft 8°C 5000ft 10°C 4000ft 12°C 14°C 3000ft Local Hotspot Warms to Trigger Temp The local surface warms the air 18°C 2000ft 16°C 1000ft NEXT NEXT NEXT NEXT

15. Introduction to Tephigrams Environmental air temp BUT What if the dew point happened to be 15°C ? 7000ft 6°C Well Cloud would form from 3000ft 6000ft 8°C The packet of air stopped rising because it is the same temperature as the environment. 5000ft 10°C 4000ft 12°C 12°C The answer to the Bronze C question is 4000ft 3000ft 14°C 15°C 2000ft 16°C 18°C The parcel of air is cooling at the DALR, 3°C/1000ft 18C 21°C 1000ft NEXT NEXT NEXT NEXT NEXT 20°C 24°C

16. Introduction to Tephigrams Environmental air temp 7000ft 6°C Well Cloud would form from 3000ft 6000ft 8°C Dewpoint Temp 5000ft 10°C Cloudbase 4000ft 12°C 12°C 3000ft 14°C 15°C If it does, Cloud will form 2000ft 16°C 18°C As it rises and cools, it might reach its dewpoint 18C 21°C 1000ft The dewpoint of the air near the surface is (say)15°C 20°C 24°C NEXT NEXT NEXT NEXT NEXT NEXT

17. Introduction to Tephigrams Environmental air temp SO if the dew point happened to be 15°C 7000ft 6°C 9°C 6000ft 8°C 10.5°C Once saturated, the parcel cools at the SALR 5000ft 10°C 12°C 4000ft 12°C 13.5°C The air has now become unstable 3000ft 14°C 15°C 2000ft 16°C 18°C The parcel of air is cooling at the DALR, 3°C/1000ft 18C 21°C 1000ft NEXT NEXT NEXT NEXT 20°C 24°C

18. Introduction to Tephigrams SALR≈ 1.5°C/1000ft Remember this? 7000ft If the slope of the ELR falls here DALR≈ 3°/1000ft 6000ft Conditionally Unstable The airmass is Unstable Stable 5000ft 4000ft 3000ft 2000ft 1000ft NEXT NEXT NEXT NEXT 10°C 20°C

19. Introduction to Tephigrams UDCSS =Urban District Council Shovels Snow 7000ft 6000ft Conditionally Unstable SALR≈ 1.5°C/1000ft Stable 5000ft DALR≈ 3°/1000ft 4000ft 3000ft 2000ft Unstable 1000ft NEXT 10°C 20°C

20. Introduction to Tephigrams Location, N 52.00° W 2.00° The minus figure indicates West of the prime meridian Valid for Date 30th January 2008 Valid time 12.00hrs Zulu Prediction 0 hours ahead NEXT NEXT

21. Introduction to Tephigrams A forecast tephigram. TheNational Oceanic and Atmospheric Administration(NOAA) Pressures not Altitudes About 30,000ft About 10,000ft About sea level NEXT NEXT NEXT NEXT NEXT NEXT

22. Introduction to Tephigrams Temperatures, lines skewed at 45° About 30,000ft About 10,000ft About sea level NEXT

23. Introduction to Tephigrams 2°C temperature divisions An aid to working out the temperature -6°C NEXT

24. Introduction to Tephigrams Wind strength and direction Northwest 60 knots Northwest 35 knots NEXT

25. Introduction to Tephigrams Dry Adiabatic Lapse lines Approx 3°C/1000ft For your convenience Saturated Adiabatic lapse lines Approx 1.6°C/ 1000ft NEXT

26. Introduction to Tephigrams Moisture content lines The amount water the air can hold at that temperature in grammes per Kg NEXT

27. Introduction to Tephigrams So far we have only described the graph paper The two traces on it are Red line is the predicted temperature as we climb through the atmosphere. The Green line is the dew point NEXT

28. Introduction to Tephigrams NEXT