Observations (and simulations) of
ABL and land surface
heterogeneity during IHOP
K. Davis, K. Craig, A. Desai, S. Kang, B. Reen,
and D. Stauffer
Department of Meteorology
The Pennsylvania State University
University Park, PA
USA
Penn State
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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BOUNDARY LAYER DEPTH DATA
449
BOUNDARY LAYER DEPTH RETRIEVAL
IHOP 2002 EXPERIMENT
File:
LEANDRE0529leg07zi.asc
Created: Fri Jan 16 08:14:21 EST 2004
Platform: LEANDRE Lidar
Date:
05/29/2002
Time:
18:00:36 - 18:39:09
Number of Data Points:
449
Average Aircraft Speed (m/s):
130.415
Starting Aircraft Altitude (m MSL): 3795.53
Ending Aircraft Altitude (m MSL):
4394.84
PI: Dr. Ken Davis (davis@met.psu.edu). Contact: Ken Craig
(kcraig@met.psu.edu).
503 Walker Building, University Park, PA 16802-5013
Derived from airborne lidar
backscatter data for all boundary layer
missions using Haar Wavelet method
TIME
18:00:36
18:00:41
18:00:46
18:00:51
18:00:56
18:01:01
18:01:06
18:01:11
18:01:16
18:01:21
18:01:26
18:01:31
18:01:36
18:01:41
18:01:47
5-6 s (~1 km) horizontal resolution
15-30 m vertical resolution
LATITUDE
36.610
36.615
36.621
36.626
36.631
36.636
36.642
36.647
36.652
36.657
36.663
36.668
36.673
36.679
36.684
LONGITUDE
-99.811
-99.812
-99.814
-99.816
-99.818
-99.820
-99.821
-99.823
-99.825
-99.827
-99.829
-99.831
-99.833
-99.834
-99.835
ZI_MSL
1835.00
1895.00
1985.00
1760.00
1595.00
1925.00
1865.00
1745.00
1745.00
2000.00
1940.00
1775.00
-999.00
1595.00
1640.00
ZI_AGL
1440.00
1500.00
1590.00
1365.00
1200.00
1530.00
1485.00
1365.00
1365.00
1605.00
1545.00
1395.00
-999.00
1215.00
1245.00
May 19, 20, 21, 25, 27, 28, 29, 30, 31
June 6, 7,16, 25
Ground spike used to compute AGL
depths
http://ihop.psu.edu
Click the “PBL-DEPTH DATA” link
Sample read routines available in IDL
and FORTRAN
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East – West surface gradient and
its impact on the ABL
(~300km scale)
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BL Heterogeneity Mission Example
29 May, 2002
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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Persistent west to east soil moisture gradient
Station7(E)
Station4(C)
Station1(W)
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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East-west soil moisture gradient surface flux
gradient based on satellite surface temps.
East – West surface gradient with a
strongly-capped ABL
(~300km scale)
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19 May 2002
Frontal 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
2
PBL DEPTH (AGL) FROM
LEANDRE LIDAR
“reverse” gradient east of
-100 W
3
4
Only a modest large-scale Zi gradient
despite the significant flux variability at
250km scale
WEST: Zi ~1.0-1.5 km
EAST: Zi ~1.0-1.2 km
Zi “jumps” at intersection
with elevated boundary
3
2
1
4
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LEANDRE LIDAR IMAGERY (5/19)
1
2
3
4
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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 an
elevated 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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29 May 2002
500
ALEXI Sensible Heat flux
indicates a sharp discontinuity
on western end of P-3 track
(but ALEXI predicts lower
fluxes than on 19 May)
400
300
200
125
Dropsonde
north of
Homestead
indicates a
weaker cap
than on 19
May
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1
2
29 May PBL-Depth data from
LEANDRE lidar
Extreme Zi variability
“low point”
3
4
5
6
4
5
3
7
2
7
6
1
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2
3
29 May
LEANDRE
Images
4
5
P-3 flies
into CBL
6
7
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May 29 LEANDRE Water Vapor (leg 4)
Extreme Zi variability associated with strong
moisture gradient
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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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Eastern soil moisture conditions remain fairly
homogeneous throughout the study.
station7
station9
station8
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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 of
IHOP.
Additional cool
region mid-track on
25 May.
Heavy precipitation
on the southern two
stations 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 on
25 May. Maybe 7
June as well.
Heavy precipitation
on the southern two
stations 27-28 May.
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N-S NDVI gradient
Very 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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UYKA Latent Heat Flux
500
TOWER Sensible and Latent Heat Flux
SURFACE FLUX
HETEROGENEITY at <50km
scale documented by multiple
ALEXI Latent Heat Flux
data sources
400
300
UYKA
Western
Track
200
125
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Rainfall: 27 May 12Z to 28 May 12Z
29 May 2002
Surface conditions
in parts of western
IHOP domain
affected by
antecedent rainfall
UYKA Western Track Soil Moisture
station1
station2
station3
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N-S variability of surface radiometric
temperatures
Cool to the south,
warm to the north,
every day, all of
IHOP.
Additional cool
region mid-track on
25 May.
Heavy precipitation
on the southern two
stations 27-28 May.
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Temporal variability of sensible heat fluxes
and 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
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fluxes
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BL Heterogeneity Mission Example
29 May, 2002
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 variability
Fairly close
match to the
surface
conditions.
Moisture spectra
have greater lowfrequency
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.
very dry&
windy
very dry&
calm
19 May
20 May
25 May
• 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.
7 June
Moist &
windy
Moist &
calm
29 May
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Zi:ABL depth, L:Obukhov Length
Blending heights for western track UWKA
flight days
Date
M
(ms-1)
Q
(K)
u*
(m s-1)
w’qv’
(Kms-1)
Lblend
(m)
Lwm
(m)
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
-zi/L
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N-S upper CBL air temperature
variability
Temperature variations
at the surface persist
throughout the CBL!
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South
North
DLR lidar observations along this N-S gradient.
Pattern was repeated on multiple DLR Falcon passes over 3 hours.
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N-S variability in ABL depth
DLR lidar backscatter data
• 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.
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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 landsurface driven spatial variability and mesoscale
flows (all).
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