Penn State
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 ([email protected]). Contact: Ken Craig ([email protected]).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).