Tephigrams for Dummies An introduction NEXT Don Puttock Introduction to Tephigrams Te phi gram “T” is the symbol used for Temperature “Phi” φ is the symbol used for pressure “gram”
Download ReportTranscript Tephigrams for Dummies An introduction NEXT Don Puttock Introduction to Tephigrams Te phi gram “T” is the symbol used for Temperature “Phi” φ is the symbol used for pressure “gram”
Tephigrams for Dummies An introduction NEXT Don Puttock 1 Introduction to Tephigrams Te phi gram “T” is the symbol used for Temperature “Phi” φ is the symbol used for pressure “gram” means graph (Invented by Napier Shaw in 1915) NEXT Don Puttock 2 Introduction to Tephigrams Temperature normally reduces with height. But not always Pressure NEXT Don Puttock Temperature 3 Introduction to Tephigrams Lower pressure Air Pressure REDUCES with altitude Pressure Higher Pressure NEXT Don Puttock Temperature 4 Introduction to Tephigrams Lower pressure Pressure ALTITUDE Higher pressure NEXT Don Puttock Temperature 5 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 Don Puttock 6 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 1000ft TEMPERATURE NEXT Don Puttock 7 10°C 20°C 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 Don Puttock 8 10°C 20°C Introduction to Tephigrams Adiabatic Heating and Cooling of a parcel of air Asair airexpands is As it Warmer compressed cooler it also cools gets warmer NEXT Don Puttock 9 Introduction to Tephigrams Air pressure decreases with Altitude If a parcel rises, it expands in the lower pressure above It cools adiabatically NEXT Don Puttock 10 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 Don Puttock 11 Introduction to Tephigrams When shown on our graph these lines look like this 7000ft 6000ft 5000ft DALR≈ 3°/1000ft SALR≈ 1.5°C/1000ft 4000ft 3000ft 2000ft 1000ft NEXT Don Puttock 12 10°C 20°C 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 Don Puttock 13 Introduction to Tephigrams Environmental air temp 7000ft 6°C 6000ft 8°C 5000ft 10°C 4000ft 12°C 3000ft 2000ft The environmental Lapse rate is 2°C/1000ft 14°C 18°C 16°C 1000ft Don Puttock The Sun heats Surface temperature is 20°C the ground Local Hotspot Warms to Trigger The localTemp surface warms the air NEXT 24°C 14 Introduction to Tephigrams Environmental air temp 7000ft BUT What if the dew point happened to be 15°C ? 6°C Well Cloud would form from 3000ft 6000ft 8°C 5000ft 10°C 4000ft 3000ft 12°C 14°C The packet of air stopped rising because it is the same temperature as the environment. 12°C 15°C 2000ft 16°C 18°C 1000ft 18C 21°C 20°C 24°C Don Puttock The answer to the Bronze C question is 4000ft The parcel of air is cooling at the DALR, 3°C/1000ft NEXT 15 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 3000ft 14°C 12°C 15°C If it does, Cloud will form 2000ft 16°C 18°C 1000ft 18C 21°C 20°C 24°C Don Puttock As it rises and cools, it might reach its dewpoint The dewpoint of the air near the surface is (say)15°C 16 NEXT 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 5000ft 10°C 12°C 4000ft 12°C 13.5°C 3000ft 14°C 15°C 2000ft 16°C 18°C 1000ft 18C 21°C 20°C 24°C Don Puttock Once saturated, the parcel cools at the SALR The air has now become unstable The parcel of air is cooling at the DALR, 3°C/1000ft NEXT NEXT 17 Introduction to Tephigrams SALR≈ 1.5°C/1000ft 7000ft 6000ft DALR≈ 3°/1000ft Remember this? If the slope of the ELR falls here The airmass is Conditionally Unstable Stable Unstable 5000ft 4000ft 3000ft 2000ft 1000ft NEXT Don Puttock 18 10°C 20°C Introduction to Tephigrams UDCSS 7000ft 6000ft 5000ft 4000ft Conditionally Unstable SALR≈ 1.5°C/1000ft DALR≈ 3°/1000ft =Urban District Council Shovels Snow Stable 3000ft 2000ft Unstable 1000ft NEXT Don Puttock 19 10°C 20°C 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 Don Puttock 20 Introduction to Tephigrams A forecast tephigram. The National Oceanic and Atmospheric Administration (NOAA) Pressures not Altitudes About 30,000ft About 10,000ft About sea level NEXT Don Puttock 21 Introduction to Tephigrams Temperatures, lines skewed at 45° About 30,000ft About 10,000ft About sea level NEXT Don Puttock 22 Introduction to Tephigrams 2°C temperature divisions An aid to working out the temperature -6°C NEXT Don Puttock 23 Introduction to Tephigrams Wind strength and direction Northwest 60 knots Northwest 35 knots NEXT Don Puttock 24 Introduction to Tephigrams Dry Adiabatic Lapse lines Approx 3°C/1000ft For your convenience Saturated Adiabatic lapse lines Approx 1.6°C/ 1000ft NEXT Don Puttock 25 Introduction to Tephigrams Moisture content lines The amount water the air can hold at that temperature in grammes per Kg NEXT Don Puttock 26 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 Don Puttock 27 Introduction to Tephigrams NEXT Don Puttock 28