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

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

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

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?

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

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.

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

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

East – West surface gradient and its impact on the ABL (~300km scale)

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.

Persistent west to east soil moisture gradient Station7(E) Station4(C) Station1(W) Station 1 = west. Station 4 = central. Station 7 = east.

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 = 150-250 W m-2 WEST = 400-450 W m-2

East-west soil moisture gradient surface flux gradient based on satellite surface temps.

East – West surface gradient with a strongly-capped ABL (~300km scale)

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

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 ~1.0-1.5 km EAST: Zi ~1.0-1.2 km 3 2 1 4

LEANDRE LIDAR IMAGERY (5/19) 2 4 3

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.

East – West surface gradient with a weakly-capped ABL (~300km scale)

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

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

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

May 29 LEANDRE Water Vapor (leg 4) Extreme Zi variability associated with strong moisture gradient

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?

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?

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.

Smaller scale heterogeneity: Along the UW King Air western (Homestead) flight track

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?

Eastern soil moisture conditions remain fairly homogeneous throughout the study. station7 station9 station8

Western track BLH cases 19, 20, 25, 29 May, 2002 7 June, 2002

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.

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.

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.

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

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

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.

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

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.

N-S 65 m air temperature variability Close match to the surface conditions. Small mid-track surface minimum on 25 May is apparent.

N-S 65 m mixing ratio variability Fairly close match to the surface conditions. Moisture spectra have greater low-frequency variability than temperature spectra.

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

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

N-S upper CBL air temperature variability Temperature variations at the surface persist throughout the CBL!

DLR lidar observations along this N-S gradient. South North Pattern was repeated on multiple DLR Falcon passes over 3 hours.

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.

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

Persistent, land-driven mesoscale flow? 65 m wind speed

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).