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K. Davis, K. Craig, A. Desai, S. Kang, B. Reen, and D. Stauffer

Department of MeteorologyThe Pennsylvania State University

University Park, PAUSA

Observations (and simulations) of ABL and land surface

heterogeneity during IHOP

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Acknowledgements and Collaborators

• DIAL groups– LASE– LEANDRE– DLR DIAL

• University of Wyoming King Air team– Field crew– LeMone et al, NCAR

• Land surface modeling/fluxes– ALEXI project, U. Wisconsin/U. Alabama, J. Mecikalski– NOAH LSM, Chen and Manning, NCAR

• NCAR/UCAR– many

• NSF Atmospheric Sciences Division• NASA Land Surface Hydrology program

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outline

• Goals/research agenda• Products available to IHOP investigators

– Lidar ABL depths– King Air flux calculations– Regional surface fluxes (?)

• Results– Lidar aircraft track analyses (~300km)– King Air track analyses (~60km)– Mesoscale circulations over Homestead

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Research agenda

• Is there significant land surface and ABL heterogeneity in the IHOP region?

• Is land surface heterogeneity a cause of the ABL heterogeneity?

• Can this heterogeneity (surface and ABL) be simulated?– Using simple 1-D thermodynamic arguments?– Using mesoscale numerical weather prediction models?

• Does ABL heterogeneity have a significant impact on CI or precip forecasting?

• Can unique IHOP observations be assimilated into NWP models to improve ABL (and therefore CI or precip) simulation?

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Research agenda

• When are persistent, surface-heterogeneity driven mesoscale flows important in the ABL?

L >> zi

L ~ zi

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Scope of investigations

• 12 BLH missions with joint airborne H2O lidar and flux aircraft operations.– No cases that led directly to deep convection.– Dates span 19 May through 22 June, 2002.

• Particular focii include:– 19 and 20 May vs. 29 May. (strongly vs. weakly

capped ABLs)– 19, 20, 25, 29 May and 7 June. (western track King

Air flights)– 10 June failed CI day – collaboration with Y.

Richardson, N. Arnott.

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Products• ABL depths derived from lidar backscatter

– LEANDRE, DLR, LASE. – ~500m horizontal and 15m vertical resolution

• UWKA turbulent flux calculations– Leg averages, segments down to 2 km, daily

composites for surface level legs

• Surface flux maps (ALEXI, Mecikalski)– 5km resolution. Numerous gaps due to cloud cover,

but whole domain coverage if clear

• ABL/LSM model combination tests within MM5– Talk by B. Reen

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449BOUNDARY LAYER DEPTH RETRIEVALIHOP 2002 EXPERIMENTFile: LEANDRE0529leg07zi.ascCreated: Fri Jan 16 08:14:21 EST 2004Platform: LEANDRE LidarDate: 05/29/2002Time: 18:00:36 - 18:39:09Number of Data Points: 449Average Aircraft Speed (m/s): 130.415Starting Aircraft Altitude (m MSL): 3795.53Ending Aircraft Altitude (m MSL): 4394.84PI: Dr. Ken Davis (davis@met.psu.edu). Contact: Ken Craig (kcraig@met.psu.edu).503 Walker Building, University Park, PA 16802-5013

TIME LATITUDE LONGITUDE ZI_MSL ZI_AGL18:00:36 36.610 -99.811 1835.00 1440.0018:00:41 36.615 -99.812 1895.00 1500.0018:00:46 36.621 -99.814 1985.00 1590.0018:00:51 36.626 -99.816 1760.00 1365.0018:00:56 36.631 -99.818 1595.00 1200.0018:01:01 36.636 -99.820 1925.00 1530.0018:01:06 36.642 -99.821 1865.00 1485.0018:01:11 36.647 -99.823 1745.00 1365.0018:01:16 36.652 -99.825 1745.00 1365.0018:01:21 36.657 -99.827 2000.00 1605.0018:01:26 36.663 -99.829 1940.00 1545.0018:01:31 36.668 -99.831 1775.00 1395.0018:01:36 36.673 -99.833 -999.00 -999.0018:01:41 36.679 -99.834 1595.00 1215.0018:01:47 36.684 -99.835 1640.00 1245.00

BOUNDARY LAYER DEPTH DATA

Derived from airborne lidar backscatter data for all boundary layer missions using Haar Wavelet method

May 19, 20, 21, 25, 27, 28, 29, 30, 31June 6, 7,16, 25

5-6 s (~1 km) horizontal resolution15-30 m vertical resolution

Ground spike used to compute AGL depths

http://ihop.psu.eduClick the “PBL-DEPTH DATA” link

Sample read routines available in IDL and FORTRAN

SAMPLE

FIL

E

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East – West surface gradient and its impact on the ABL

(~300km scale)

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BL

Het

erog

enei

ty M

issi

on

Exa

mpl

e29

May

, 200

2

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Conclusions – 300km scale• Substantial and persistent E-W

heterogeneity in the surface energy balance.

• Surface energy balance gradient captured by ALEXI

• ABL heterogeneity (ABL depth) coarsely matches SEB gradient, but strongly modulated by inversion strength.

• Abrupt transitions in ABL depth may be due to upper atmospheric structure.

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Station7(E)

Station1(W)

Station4(C)

Persistent west to east soil moisture gradient

Station 1 = west. Station 4 = central. Station 7 = east.

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ISFF TOWER FLUXES

Significant heterogeneity at 250 km scale

Nearly homogeneous at smaller scales over OK Panhandle & SW Kansas

ALEXI SENSIBLE HEAT FLUX

EAST = 150-250 W m-2

WEST = 400-450 W m-2

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Eas

t-w

est

soil

moi

stur

e gr

adie

nt s

urfa

ce

flux

grad

ient

bas

ed o

n sa

telli

te s

urfa

ce t

emps

.

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East – West surface gradient with a strongly-capped ABL

(~300km scale)

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19 May 2002Frontal Passage

leaves IHOP region under a cool, dry, and well-capped airmass

DLR Falcon morning

Dropsonde

On LEANDRE track north of Homestead

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1

43

2

1

3

4

2

PBL DEPTH (AGL) FROM LEANDRE LIDAR

“reverse” gradient east of -100 W

Zi “jumps” at intersection with elevated boundary

Only a modest large-scale Zi gradient despite the significant flux variability at 250km scale

WEST: Zi ~1.0-1.5 kmEAST: Zi ~1.0-1.2 km

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LEANDRE LIDAR IMAGERY (5/19)

1

43

2

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Conclusions – strongly capped ABL

•Modest E-W ABL depth difference• Strong E-W ABL moisture difference (?)

• Sharp change in ABL depth is co-located with anelevated layer. Not exactly co-located with E-W

surface flux boundary.

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East – West surface gradient with a weakly-capped ABL

(~300km scale)

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ALEXI Sensible Heat flux indicates a sharp discontinuity on western end of P-3 track (but ALEXI predicts lower fluxes than on 19 May)

29 May 2002

Dropsonde north of Homestead indicates a weaker cap than on 19 May

500

400

300

200

125

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1

43

2

5

7

6

29 May PBL-Depth data fromLEANDRE lidar

Extreme Zi variability

“low point”

1

4 5

2

3 6

7

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29 May

LEANDREImages

2

54

3

76

P-3 flies into CBL

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Extreme Zi variability associated with strong moisture gradient

May 29 LEANDRE Water Vapor (leg 4)

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Conclusions – weakly capped ABL

• Extreme E-W ABL depth and moisture difference•Sharp change in ABL depth is co-located with the

the surface energy balance boundary?

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Zi Data composite from east/west tracks for all Boundary-Layer Missions

Deviation from leg-average is plotted

200-km scale gradient as expected

East of -100W, BL seems to get larger to the east

Same as above, but without 29 May and 7 June data

Regional gradients in ABL depth are gone?

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Conclusions – ABL climatology

• E-W ABL depth contrasts most pronounced for weakly-capped ABL.

• Need to add a climatology of ABL water vapor from DIAL, and correlate with surface flux

climatology.

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Smaller scale heterogeneity: Along the UW King Air western

(Homestead) flight track

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Conclusions – 60km scale• Persistent surface heterogeneity exists along the

western King Air track• ALEXI appears to capture this heterogeneity• The ABL mirrors this surface heterogeneity.

Substantial spatial variability exists throughout the depth of the ABL.

• Surface structure varies with:– Rainfall– Soil characteristics– Vegetation cover

• With light winds(only?), stationary mesoscale flow develops?

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station7 station9station8

Eastern soil moisture conditions remain fairlyhomogeneous throughout the study.

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Western track BLH cases

• 19, 20, 25, 29 May, 2002

• 7 June, 2002

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N-S variability of surface radiometric temperatures

Cool to the south,warm to the north,every day, all ofIHOP.

Additional cool region mid-track on25 May.

Heavy precipitationon the southern twostations 27-28 May.

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N-S variability of surface sensible heat fluxes

Lower H to the south,higher H to the north,evident on most days.

Additional low H region mid-track on25 May. Maybe 7June as well.

Heavy precipitationon the southern twostations 27-28 May.

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N-S NDVI gradientVery little vegetation in May.

Green spot in a small river valley.

Greenness increases a little by June.

Southern end becomes relatively lush.

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500

400

300

200

125

ALEXI Latent Heat Flux

TOWER Sensible and Latent Heat FluxUYKA Latent Heat Flux

SURFACE FLUX HETEROGENEITY at <50km

scale documented by multiple data sources

UYKA Western

Track

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29 May 2002

Surface conditions in parts of western

IHOP domain affected by

antecedent rainfall

Rainfall: 27 May 12Z to 28 May 12Z

station2station1

station3

UYKA Western Track Soil Moisture

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N-S variability of surface radiometric temperatures

Cool to the south,warm to the north,every day, all ofIHOP.

Additional cool region mid-track on25 May.

Heavy precipitationon the southern twostations 27-28 May.

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Temporal variability of sensible heat fluxesand tower-aircraft intercomparison

• H flux lowest in the south.

• H flux decreases with time as vegetation grows, rain falls.

•Aircraft H matches ISFF H quite well. Modest systematic offset.

Station 1

Station 2

Station 3

+: average over station 1, 2, and 3 Solid Line: leg average of the a/c fluxes

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BL

Het

erog

enei

ty M

issi

on

Exa

mpl

e29

May

, 200

2

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Temporal Variability of the ABL depth

• The ABL depth on 19, 20, May and 7 June is relatively high

• The ABL depth on 25 and 29 May is relatively low

• A 1-D thermodynamic model explains the within-day temporal and spatial variability, and day-to-day mean variability fairly well.

Dotted line: ABL depth estimated from the DLR Falcon backscatter.

Solid line: ABL depth estimated from UWKA in situ soundings.

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N-S 65 m air temperature variability

Close match to the surface conditions.

Small mid-track surface minimum on 25 May is apparent.

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N-S 65 m mixing ratio variabilityFairly close match to the surface conditions.

Moisture spectra have greater low-frequency variability than temperature spectra.

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Do spatially persistent mesoscale circulations exist?

• 19 and 20 May, large surface H and strong winds.

• 7 June, smaller surface H and strong winds.

• 29 May, smallest surface H and moderate winds.

• 25 May, large surface H and light winds. Ideal for development of mesoscale flows driven by the land surface.

Zi:ABL depth, L:Obukhov Length

19 May

20 May

7 June

25 May

29 May

very dry& windy

very dry& calm

Moist & calm

Moist & windy

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Blending heights for western track UWKA flight days

Date M(ms-1)

u*

(m s-1)

w’v’

(Kms-1)

Lblend

(m)

Lwm

(m)

-zi/L

May 19 13.2 299.7 0.76 0.31 12769 2869 12.8

May 20 13.2 300.4 0.76 0.29 12449 2958 12.2

May 25A 1.1 296.5 0.26 0.19 704 366 117.8

May 25B 3.4 300.3 0.29 0.21 5677 1070 113.4

May 29 4.9 308.3 0.39 0.14 7030 2879 37.4

June 7 10.2 310.3 0.54 0.17 13434 4135 20.5

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N-S upper CBL air temperature variability

Temperature variations at the surface persist throughout the CBL!

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DLR lidar observations along this N-S gradient.

Pattern was repeated on multiple DLR Falcon passes over 3 hours.

Sou

th N

ort

h

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• On 19, 20, and 29 May, the ABL depth increases with latitude.

• On 25 May, and 7 June, ABL depth is more homogeneous.

• ABL depth patterns match the surface H patterns surprisingly well.

N-S variability in ABL depthDLR lidar backscatter data

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Persistent, land-driven mesoscale flow? 65 m wind direction

Wind directions appear to respond to the surface forcing as well.

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Persistent, land-driven mesoscale flow? 65 m wind speed

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Plan

• E-W ABL, land-surface climatology– Add DIAL water vapor– Add ground-based ABL profilers

• Publish western track work– Add DOWs, UWKA cloud radar?

• Model whole domain BLH days (Reen, Craig) and western track (Kang)

• Analysis of ability to model ABL, especially land-surface driven spatial variability and mesoscale flows (all).