3d case:

3.' ' a , '' a

•Updraft air is saturated and downdraft flux is not.

	'		S '			'
T ( a		)			( a ) w		t	(10.18)
			S	''

• Cu clouds development

Lecture 10. Slice method

11

• From (10.18)

T 0 at a and

T 0 at ' a

•Stability criteria of both methods are coincide if the stratification is absolutely unstable and absolutely stable. However,

often	' a a

T on but also S ' S ''

Lecture 10. Slice method

12

Let’s introduce a critical lapse rate

cr

at

T 0

'

S '

'

(

)

( )

w

t 0

''

a

S

a

w '

0,

t

0

S

'

( a '

)

( a )

0

S

''

' a a

(S

'

'' )

cr

S

(10.19)

1 S

'

S ''

Lecture 10. Slice method

13

cr

a'

at small values

of

(S '

S

'' )

cr

a

at l arg e values

of

(S '

'' )

S

cr

( T 0)

cr

( T 0)

S '

' a

at

T 0

(10.20)

S ''

a

S '

' a

at

T 0

(10.21)

S ''

a

• at conditionally unstable stratification the atmosphere is unstable for small size particles

and it’s stable for LARGE size particles =>>the atmospere is said to be selectively unstable

Lecture 10. Slice method

14