Don Puttock1 Tephigrams for Dummies An introduction NEXT.

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Don Puttock 1 Tephigrams for Dummies An introduction NEXT

Transcript of Don Puttock1 Tephigrams for Dummies An introduction NEXT.

Page 1: Don Puttock1 Tephigrams for Dummies An introduction NEXT.

Don Puttock 1

Tephigrams for Dummies

An introduction

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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

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Introduction to Tephigrams

Pressure

TemperatureNEXT

Temperature normally reduces with height.

But not always

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Introduction to Tephigrams

Pressure

Temperature

Lower pressure

Higher Pressure

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Air Pressure REDUCES with altitude

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Introduction to Tephigrams

Pressure

Temperature

Higher pressure

Lower pressure

ALTITUDE

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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

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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

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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

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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

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Warmer

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Introduction to Tephigrams

Air pressure decreases with Altitude

If a parcel rises, it expands in the lower pressure above

It cools adiabatically

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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.

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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

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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?

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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

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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

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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

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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

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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

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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

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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

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Introduction to TephigramsA forecast tephigram. The National

Oceanic and Atmospheric Administration (NOAA)

Pressures not Altitudes

About 30,000ft

About sea level

About 10,000ft

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Introduction to Tephigrams

About 30,000ft

About sea level

About 10,000ft

Temperatures, lines skewed at 45°

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Introduction to Tephigrams

An aid to working out the temperature

-6°C

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2°C temperature divisions

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Introduction to TephigramsWind strength and direction

Northwest 35 knots

Northwest 60 knots

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Introduction to Tephigrams

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Dry Adiabatic Lapse lines

Approx 3°C/1000ft

For your convenience

Saturated Adiabatic lapse lines

Approx 1.6°C/ 1000ft

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Moisture content lines

Introduction to Tephigrams

The amount water the air can hold at that temperature in grammes per Kg

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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

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Introduction to Tephigrams

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