Don Puttock 1
Tephigrams for Dummies
An introduction
NEXT
Don Puttock 2
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) NEXTNEXTNEXTNEXTNEXTNEXT
Don Puttock 3
Introduction to Tephigrams
Pressure
TemperatureNEXT
Temperature normally reduces with height.
But not always
NEXTNEXT
Don Puttock 4
Introduction to Tephigrams
Pressure
Temperature
Lower pressure
Higher Pressure
NEXT
Air Pressure REDUCES with altitude
NEXT
Don Puttock 5
Introduction to Tephigrams
Pressure
Temperature
Higher pressure
Lower pressure
ALTITUDE
NEXTNEXT
Don Puttock 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
Don Puttock 7
Introduction to TephigramsENVIRONMENTAL LAPSE RATE 2°C/1000ft
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ft
20°C10°C
ALTITUDE
But this is idealised---In reality the ELR is never a steady reduction like this
TEMPERATURENEXTNEXTNEXTNEXT
Don Puttock 8
Introduction to TephigramsACTUAL or FORECAST SOUNDING
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ft
20°C10°C
It is far more usual to see it like this.
OR THIS
NEXTNEXTNEXTNEXT
Don Puttock 9
Introduction to Tephigrams
Adiabatic Heating and Cooling of a parcel of air
As air expands it also cools
As air is compressed it gets warmer
cooler
NEXTNEXTNEXT
Warmer
NEXTNEXTNEXT
Don Puttock 10
Introduction to Tephigrams
Air pressure decreases with Altitude
If a parcel rises, it expands in the lower pressure above
It cools adiabatically
NEXTNEXTNEXT
Don Puttock 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.
NEXTNEXTNEXTNEXTNEXT
Don Puttock 12
Introduction to Tephigrams
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ft
20°C10°C
DALR≈ 3°/1000ft SALR≈
1.5°C/1000ft
When shown on our graph these lines look like this
NEXTNEXT
Don Puttock 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
Don Puttock 14
Introduction to Tephigrams
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ftSurface temperature is 20°C
The environmental Lapse rate is 2°C/1000ft
Environmental air temp
18°C16°C
14°C
12°C
10°C
8°C
6°C
The Sun heats the ground
Local Hotspot Warms to Trigger Temp
24°C
The local surface warms the air
NEXTNEXTNEXTNEXT
Don Puttock 1524°C
Introduction to Tephigrams
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ft
20°C
Environmental air temp
16°C
18C
12°C
10°C
8°C
6°C
21°C
18°C
12°C
The packet of air stopped rising because it is the same temperature as the environment.
The answer to the Bronze C question is 4000ft
BUT What if the dew point happened to be 15°C ?
The parcel of air is cooling at the DALR, 3°C/1000ft
Well Cloud would form from 3000ft
14°C 15°C
NEXTNEXTNEXTNEXTNEXT
Don Puttock 1624°C
Introduction to Tephigrams
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ft
20°C
Environmental air temp
16°C
18C
12°C
10°C
8°C
6°C
21°C
18°C
12°C
Well Cloud would form from 3000ft
14°C 15°C
Dewpoint Temp
The dewpoint of the air near the surface is (say)15°C
As it rises and cools, it might reach its dewpoint
If it does, Cloud will form
Cloudbase
NEXTNEXTNEXTNEXTNEXTNEXT
Don Puttock 1724°C
Introduction to Tephigrams
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ft
20°C
Environmental air temp
16°C
18C
12°C
10°C
8°C
6°C
21°C
18°C
SO if the dew point happened to be 15°C
The parcel of air is cooling at the DALR, 3°C/1000ft
14°C 15°C
12°C
9°C
10.5°C
13.5°C
Once saturated, the parcel cools at the SALR
The air has now become unstable
NEXTNEXTNEXTNEXT
Don Puttock 18
Introduction to Tephigrams
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ft
20°C10°C
DALR≈ 3°/1000ft
SALR≈ 1.5°C/1000ft
Remember this?
If the slope of the ELR falls here
The airmass is UnstableConditionally Unstable
Stable
NEXTNEXTNEXTNEXT
Don Puttock 19
Introduction to Tephigrams
1000ft
4000ft
3000ft
2000ft
5000ft
6000ft
7000ft
20°C10°C
DALR≈ 3°/1000ft
SALR≈ 1.5°C/1000ft
Unstable
Conditionally Unstable Stable
UDCSS =Urban District Council Shovels Snow
NEXT
Don Puttock 20
NEXT
Location, N 52.00° W 2.00°
Valid for Date
30th January 2008
Prediction 0 hours ahead
The minus figure indicates West of the prime meridian
Introduction to Tephigrams
Valid time
12.00hrs Zulu
NEXT
Don Puttock 21
Introduction to TephigramsA forecast tephigram. The National
Oceanic and Atmospheric Administration (NOAA)
Pressures not Altitudes
About 30,000ft
About sea level
About 10,000ft
NEXTNEXTNEXTNEXTNEXTNEXT
Don Puttock 22
Introduction to Tephigrams
About 30,000ft
About sea level
About 10,000ft
Temperatures, lines skewed at 45°
NEXT
Don Puttock 23
Introduction to Tephigrams
An aid to working out the temperature
-6°C
NEXT
2°C temperature divisions
Don Puttock 24
NEXT
Introduction to TephigramsWind strength and direction
Northwest 35 knots
Northwest 60 knots
Don Puttock 25
Introduction to Tephigrams
NEXT
Dry Adiabatic Lapse lines
Approx 3°C/1000ft
For your convenience
Saturated Adiabatic lapse lines
Approx 1.6°C/ 1000ft
Don Puttock 26
NEXT
Moisture content lines
Introduction to Tephigrams
The amount water the air can hold at that temperature in grammes per Kg
Don Puttock 27
Introduction to Tephigrams
NEXT
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
Don Puttock 28
Introduction to Tephigrams
NEXT
Top Related