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
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. ALEXI SENSIBLE HEAT FLUX
ISFF TOWER FLUXES
Significant heterogeneity at 250 km scale
Nearly homogeneous at smaller scales over OK Panhandle & SW Kansas
ALEXI SENSIBLE HEAT FLUX
EAST = W m-2 WEST = 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 1 2 3 4
Only a modest large-scale Zi gradient despite the significant flux variability at 250km scale
WEST: Zi ~ km EAST: Zi ~ km 3 2 1 4

18. LEANDRE LIDAR IMAGERY (5/19)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 from LEANDRE lidar Extreme Zi variability
“low point” 1 2 3 4 5 6 4 5 3 6 2 7 7 1

23. 2 3
29 May
LEANDRE Images 4 5
P-3 flies into CBL 6 7

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. Deviation from leg-average is plotted
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 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 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
TOWER Sensible and Latent Heat Flux
SURFACE FLUX HETEROGENEITY at <50km scale documented by multiple data sources
ALEXI Latent Heat Flux
500
400
UYKA Western Track
300
200
125

36. UYKA Western Track Soil Moisture
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 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 & windy
Moist & calm
29 May
Zi:ABL depth, L:Obukhov Length

44. 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
-zi/L
May 19
13.2
299.7
0.76
0.31
12769
2869
12.8
May 20
300.4
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
0.21
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

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.
South
North
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 Publish western track work
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).