4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

4th Symposium on Lidar Atmospheric Applications

4.4 Short time fluctuations of the convective boundary layer height and

entrainment observed with Doppler lidarK. Träumner, A. Wieser,

Ch. Kottmeier and U. Corsmeier

Institute for Meteorology and Climate Research, KIT

Karlsruhe, Germany

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Questions, which will be addressed

• Is it possible to visualize and identify different entrainment mechanisms in the atmospheric boundary layer?

• What is the entrainment zone?

• Are small-scale boundary layer height fluctuations linked to the current wind field?

• Is there a correlation between entrainment velocity and entrainment zone thickness?

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Introduction

Using the 2 µm Doppler lidar an aerosol backscatter as well as vertical wind information are available.

Small-scale fluctuations Diurnal increase CBL

Entrainment

1 hour

5 to 22 UTC

We use the CSIP, 2005 data set (gently rolling terrain)

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Boundary layer height (BLH) determination

4 +1 automatically working algorithms for high resolution determination usingaerosol backscatter information and vertical velocity variance

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Visualizing entrainment processes

Entrainment at the edges of plumes

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Entrainment due to large scale engulfment

Visualizing entrainment processes

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Concepts of entrainment zone thickness (EZT)Statistical concepts vs transition zone

• strongly correlated• transition zone is mostly wider• all approaches show variations during the day, but no typical diurnal cycle

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Relationship between EZT and BLH

iza=Δh

Measured ratios corresponds to

09.023.0''

''

0

w

w iz

Δh

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

d+Ric=z

Δh α

i

Relationship between EZT and BLH

Δh/

h

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Correlation vertical wind

• no simple correlation connecting BLH lifting to updraft and vice versa• deformation due to thermals• variations reflect processes the air mass experienced upstreams

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Entrainment velocity

2αe

1α

i

RiU

w

Riz

Δh

Δh/h

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Conclusions

• It is possible to visualize different entrainment processes using Doppler lidar

• Statistically concepts and the transition zone concept of the EZT differ but are correlated; mixing, and so entrainment, reaches deeper than varying tops of BLH

• There is no general relationship between EZT and BLH• BLH short-time fluctuations are in principle not linked to the

current vertical wind field • There is a relationship between entrainment velocity and EZT

Results from laboratory studies and simulations were comparable to atmospheric boundary layer measurements

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Thanks

Thanks for attention.

For details please see manuscript.

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Additionally information

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

BLH from aerosol and turbulence profile

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Concepts of EZTCorrelation of different statistically concepts (h0,h2 using Percentile analysis and σz standard deviation)

Correlation of statistical concepts and transition zone

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Visualizing entrainment processes

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Entrainment velocity

αe Rib=U

w

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Entrainment velocity

αe Rib=U

w

4.4 Short time fluctuations of the convective boundary layer height and entrainment observed with Doppler lidar

K. Träumner, A. Wieser, C. Kottmeier and U. Corsmeier

KIT – die Kooperation vonForschungszentrum Karlsruhe GmbHund Universität Karlsruhe (TH)

Entrainment velocity

αe Rib=U

w