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KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) The...
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Transcript of KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) The...
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
The dependence of convection-related parameters on surface and boundary layer conditions
over complex terrain: results from the COPS experiment
N. Kalthoff, M. Kohler, Ch. Barthlott, L. Krauss, U. Corsmeier,
T. Foken, R. Eigenmann, S. Khodayar, P. Di Girolamo
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
The surface - atmosphere feedback loop consists of:
The impact of soil moisture on the surface fluxes
The influence of surface fluxes on the PBL conditions and convection-related parameters
The triggering and modification of convection by surface and PBL inhomo-geneities
The impact of convection on the condi-tions of the surface and atmosphere
Here we focus on part and :
CAPE, CIN
H E
PBL
Soil moisture
1
2
3
4
1
2
3
4
How strong is the impact of soil moisture > surface fluxes > PBL conditions >
convection-related parameters during COPS (i.e. over complex terrain)
1 2
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
1 COPS experimental setup
COPS domain (left) and measurement sites in the northern part of the COPS domain (right).
• Soil moisture network
• Energy balance and surface flux network
• Radiosonde network
Rhine valley: FZK, Achern/Baden Airpark
Black Forest: Hornisgrinde, Heselbach
We used data from the:
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
2.1 Impact of soil moisture on the surface characteristics
10
15
20
25
30
35
40
45
50
TS in
°C
15 20 25 30 35
vol,5 in %
FZK
Baden Airpark
10
15
20
25
30
35
40
45
50
TS in
°C
30 35 40 45 50 55 60 65 70
vol,5 in %
Heselbach
Hornisgrinde
a)
b)• Soil moisture increases with the elevation
• No dependence of the albedo on θvol
• Only in the Rhine valley: A dependence of the surface temperature, Ts, on θvol
=> Only in the Rhine valley a weak dependence of net radiation (available energy) on θvol was
observed
H E
1
Soil moisture
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
0.26
0.28
0.30
15 20 25 30 35 40 45 50 55 60 65 70
vol,5 in %
FZK
Baden Airpark
Heselbach
Hornisgrinde
alb
ed
o
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
0.0
0.2
0.4
0.6
0.8
1.0
H0/
Q0,
E0/
Q0
15 20 25 30 35
vol,5 in %
H0/Q0 E0/Q0
0.0
0.2
0.4
0.6
0.8
1.0
H0/
Q0,
E0/
Q0
15 20 25 30 35
vol,5 in %
H0/Q0 E0/Q0
a) b)
0.0
0.2
0.4
0.6
0.8
1.0
H0/
Q0,
E0/
Q0
25 30 35 40 45
vol,5 in %
H0/Q0 E0/Q0
c)
0.0
0.2
0.4
0.6
0.8
1.0
H0/
Q0,
E0/
Q0
55 60 65 70 75
vol,5 in %
H0/Q0 E0/Q0
d)
2.2 Impact of soil moisture on the surface fluxes
Rhine valley
•Ho/Qo is slightly lower for higher soil moisture
•Eo/Qo is slightly higher for higher soil moisture
Black Forest
•No dependence of Ho/Qo and Eo/Qo on soil moisture
=> During the COPS period the impact of soil moisture on the surface
characteristics and on the surface fluxes was weak – probably due to the high
vegetation coverage!
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
3.1 The dependence of zi on the sensible heat flux
0
500
1 000
1 500
2 000
2 500
zi i
n m
ag
l
0 20 40 60 80 100 120 140 160
H0 in W m-2
0
500
1 000
1 500
2 000
2 500
z i in
m a
gl
0 20 40 60 80 100 120 140 160
H0 in W m-2
FZK
Achern
Heselbach
0
500
1 000
1 500
2 000
2 500
z i in
m a
gl
0 20 40 60 80 100 120 140 160
H0 in W m-2
Hornisgrinde
a)
b)
c)
• In the Rhine valley (FZK, Achern) and at Heselbach a weak correlation between zi and Ho was found
• Over the mountain crest (Hornisgrinde) zi is independent of Ho
2
3
H E
PBL
Soil moisture
1
2
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
3.2 The impact of the surface fluxes on Θe in the PBL
-3
-2
-1
0
1
2
3
4
5
et
-1 in
K h
-1
0 100 200 300 400 500 600
H0 + E0 in W m-2
-3
-2
-1
0
1
2
3
4
5
e t
-1 in
K h
-1
0 100 200 300 400 500 600
H0 + E0 in W m-2
Baden Airpark
FZK
Heselbach
Hornisgrinde
a)
b)
• The dependence of the diurnal increase of moist static energy / Θe in the Rhine valley (FZK, Baden Airpark) and at Heselbach is weak
• There is nearly no dependence of the evolution of the moist static energy / Θe at the mountain crest (Hornisgrinde)
=> Especially in the Black Forest the impact of the surface fluxes on the PBL conditions (zi, Θe ) is weak, i.e. advection processes must be important for the evolution of the PBL
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
4.1 Dependence of convection indices on PBL conditions
0
200
400
600
800
1 000
1 200
1 400
CA
PE
in J
kg
-1
300 310 320 330 340 350
e in K
a) b)
-20
-15
-10
-5
0
5
10
15
20
KO
in K
300 310 320 330 340 350
e in K
c)
-20
-15
-10
-5
0
5
10
15
20
KO
in K
300 310 320 330 340 350
e in K
d)
0
200
400
600
800
1 000
1 200
1 400
CA
PE
in J
kg
-1
300 310 320 330 340 350
e in K
Achern
FZK
Heselbach
Hornisgrinde
Heselbach
Hornisgrinde
Achern
FZK
-10
-5
0
5
10
15
20
25
30
LI i
n K
300 310 320 330 340 350
e in K
e)
-10
-5
0
5
10
15
20
25
30
LI i
n K
300 310 320 330 340 350
e in K
f)
Heselbach
Hornisgrinde
Achern
FZK
• The convection indices CAPE, LI (conditional instability)
and
KO (potential instability) are highly correlated with Θe in the PBL
• This finding is valid for the Rhine valley and the Black Forest!
H E
PBL
Soil moisture
1
2CAPE, CIN
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
4.1 Dependence of evolution of the convection indices on the PBL evolution
• The diurnal increase of CAPE, LI and KO was caused by the PBL evolution on most of the days
Original CAPE, LI and KO values at Heselbach
Modified CAPE, LI and KO values:
initial nocturnal profile but in PBL the data are replaced by the conditions at noontime
Strong changes in the mid- and upper troposphere
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
0
50
100
150
200
250
300
350
400C
IN i
n J
kg
-1
0 500 1 000 1 500 2 000 2 500
zi in m agl
0
50
100
150
200
250
300
350
400
CIN
in
J k
g-1
0 500 1 000 1 500 2 000 2 500
zi in m agl
a) b)
c) d)
Achern
FZK
Heselbach
Hornisgrinde
0
2
4
6
8
10
CA
P in
K
0 500 1 000 1 500 2 000 2 500
zi in m agl
0
2
4
6
8
10
CA
P in
K
0 500 1 000 1 500 2 000 2 500
zi in m agl
Heselbach
Hornisgrinde
Achern
FZK
4.2 Dependence of convection inhibition on PBL conditions
• The higher zi the lower the upper threshold for CIN and CAP strength
This was observed at all sites!
• CIN and CAP strength were independent of Θe in the PBL
CAP=max(Te-Tp)
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
0
100
200
300
400
500
600
CIN
in J
kg
-1
0 2 4 6 8 10
CAP in K
Achern
FZK
Heselbach
Hornisgrinde
a)
b)
0
100
200
300
400
500
600
CIN
in J
kg
-1
0 200 400 600 800 1 000 1 200 1 400
CAPE in J kg-1
Achern
FZK
Heselbach
Hornisgrinde
0
10
20
30
40
50
60
70
freq
uen
cy in
%
0 50 100 150 200 250 300 350 400 450 500
CIN in J kg-1
Rhine valley
Black Forest
• A good correlation between CIN and CAP strength existed at all sites
• The occurrence of low CIN values was higher over the Black Forest than over the Rhine valley
=> Lower CIN values are favourable for convection initiation over the mountains
4.3 Characteristics of convection inhibition
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
5 Conclusions
Soil > surface
The impact of soil moisture on the surface parameters (α, Ts, Qo) and on the energy transformation at the Earth‘s surface (β) is weak
Surface > PBL
Rhine valley: The dependence of the PBL characteristics like Θe and zi on the surface fluxes is weak
Black Forest: Nearly no dependence of the PBL characteristics like Θe and zi on the surface fluxes
=>Consequently, advection processes must be important for the evolution of the PBL - especially over the mountains
PBL > Convection-related parameters
CAPE, LI and KO depend on Θe in the PBL (observed at all site)The impact of PBL conditions on CIN and CAP is weak (except: max CIN and max CAP depend on zi) CAP and CIN are highly correlatedThe frequency of occurrence of low CIN values is higher over the Black Forest than over the Rhine valley => Favours CI over the mountains
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
Outline
1 Introduction
2 Experimental setup
3 Impact of soil moisture on the surface characteristics and
the turbulent fluxes
4 The dependence of CBL conditions on the turbulent fluxes
5 The dependence of convection-related parameters on
boundary-layer conditions
6 Conclusions
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
3 Impact of the surface fluxes on the CBL conditions
For homogeneous terrain:
• zi is higher for higher Ho and for higher
Bowen ratio
• CIN and CAPE depend the surface and PBL conditions in the PBL (β => q, Θ, Θe, zi)
• What about the dependences over complex terrain?
2
3
H E
PBL
Soil moisture
1
2
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
2 Impact of soil moisture on the surface characteristics and the turbulent fluxes
• Precipitation increases with elevation
• Soil moisture, θvol, increases with elevation
H E1
Soil moisture
KIT – die Kooperation von Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH)
4
H E
1
Soil moisture
CAPE, CIN
2
H E
PBL
Soil moisture
1
2