Observations (and simulations) of ABL and land surface heterogeneity during IHOP

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 weakercap 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 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. 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. 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. 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 & windy Moist & calm 29 May Zi:ABL depth, L:Obukhov 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).