UMBC PBL Height Study

UMBC PBL Height Study

Chris Wilson, Ruben Delgado, W. Wallace McMillan, Ray Hoff

Overview

• Description of the ProblemBoundary layer depth!

• Instruments and measurement techniques(LIDAR, BBAERI)

• Preliminary results

The diurnal evolution of the atmospheric boundary layer over land (from Wyngaard, 1992)

BBAERI vs. ELF

Expected collapse of PBL after sunset seen by both instruments

B.L. top

Residual Layer

B.L. TopB.L. Top

AERI• Atmospheric Emitted Radiance

Interferometer

• Measures downwelling IR radiation spectra (3 – 18 μm) passively

• 1 cm -1 Resolution

H2O

H2O

CO2

O3

CO2

CO

AERI T/q

Statistical regression (training sondes)

Spectra, surface, RUC

“Onion Peel”

Physical Retrieval

T(p), q(p), theta(p), RH(p)

* From Smith ET AL. 1999

* *

Covariance Wavelet TechniqueCovariance Wavelet Technique

W a ba

f z hz b

adz

zb

zt( , ) ( ) ( )

1

Covariance transform defined by Gamage and Hagelberg (1993):

• zt and zb are the top and bottom altitudes in the lidar backscatter profile• f(z)is the lidar backscatter profile as a function of altitude, z• a-1 is the normalization factor

Haar function

• z=vertical distance in this application• a=spatial extent dilation of the function• b=center of Haar function- translation of the function

PBL Determination:

•Compute convolution of the backscatter profile, f(z), and the Haar function.

•Taking a lidar backscattering profile, calculate a local minimum in W (a,b) using a scale of a located at z = b

•This process is repeated for all individual lidar backscatter profiles to create a time series of boundary locations.

The key of the wavelet analysis is the selection of an appropriatedilation (vertical scale).

BBAERI Height Methods

• Gradient in Virtual Potential Temperature

• Temperature Inversion

• Parcel Method

• Minimum gradient in q (water vapor mixing ratio)

Inversion

Parcel Method

VPT

Gradient

Minimum in gradient of q

Hei

ght

(met

ers)

Time (GMT)

Hei

ght

(met

ers)

Time (GMT)

Final Remarks

• Sonde measurements are needed

• Many more days are needed to create robust statistics

• BBAERI water vapor product may be to coarse to accurately measure PBL height

Hei

ght

(met

ers)

Time (GMT)