Penn State

1
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

2
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

3
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

4
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?

5
Research agenda

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

6
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.

7
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

8
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,
31 June 6, 7,16, 25 5-6 s (1 km) horizontal
resolution 15-30 m vertical resolution 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
SAMPLE FILE
9
East West surface gradient and its impact on
the ABL(300km scale)
10
BL Heterogeneity Mission Example 29 May, 2002
11
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.

12
Persistent west to east soil moisture gradient
Station7(E)
Station4(C)
Station1(W)
Station 1 west. Station 4 central. Station
7 east.
13
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-2WEST 400-450 W m-2
14
East-west soil moisture gradient surface
flux gradient based on satellite surface temps.
15
East West surface gradient with a
strongly-capped ABL(300km scale)
16
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
17
PBL DEPTH (AGL) FROM LEANDRE LIDAR reverse
gradient east of -100 W Zi jumps at
intersection with elevated boundary
2
1
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
3
2
1
4
18
LEANDRE LIDAR IMAGERY (5/19)
1
2
4
3
19

• 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.

20
East West surface gradient with a weakly-capped
ABL(300km scale)
21
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
22
29 May PBL-Depth data fromLEANDRE lidar Extreme
Zi variability low point
2
1
4
3
5
6
4
5
3
6
7
2
7
1
23
2
3
29 May LEANDREImages
5
4
P-3 flies into CBL
7
6
24
May 29 LEANDRE Water Vapor (leg 4)
Extreme Zi variability associated with strong
moisture gradient
25

• 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?

26
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?
27

• 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.

28
Smaller scale heterogeneity Along the UW King
Air western (Homestead) flight track
29
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?

30
Eastern soil moisture conditions remain
fairly homogeneous throughout the study.
station7
station9
station8
31
Western track BLH cases

• 19, 20, 25, 29 May, 2002
• 7 June, 2002

32
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.
33
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.
34
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.
35
TOWER Sensible and Latent Heat Flux
UYKA Latent Heat Flux
SURFACE FLUX HETEROGENEITY at lt50km scale
documented by multiple data sources
ALEXI Latent Heat Flux
500
400
UYKA Western Track
300
200
125
36
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
37
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.
38
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
average over station 1, 2, and 3
Station 2
Solid Line leg average of the a/c fluxes
Station 3
39
BL Heterogeneity Mission Example 29 May, 2002
40
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.
41
N-S 65 m air temperature variability
Close match to the surface conditions. Small
mid-track surface minimum on 25 May is apparent.
42
N-S 65 m mixing ratio variability
Fairly close match to the surface
conditions. Moisture spectra have greater
low-frequency variability than temperature
spectra.
43
Do spatially persistent mesoscale circulations
exist?
very dry windy
very dry calm

• 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.

19 May
20 May
25 May
7 June
Moist calm
Moist windy
29 May
ZiABL depth, LObukhov Length
44
Blending heights for western track UWKA flight
days
45
N-S upper CBL air temperature variability
Temperature variations at the surface persist
throughout the CBL!
46
DLR lidar observations along this N-S gradient.
North
South
Pattern was repeated on multiple DLR Falcon
passes over 3 hours.
47
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.

48
Persistent, land-driven mesoscale flow? 65 m
wind direction
Wind directions appear to respond to the surface
forcing as well.
49
Persistent, land-driven mesoscale flow? 65 m
wind speed
50
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).