Transcript Davis ABL Presentation

Mesoscale variability in
convective boundary layer
structure observed during IHOP:
Causes and implications for
convective initiation
K. Davis, K. Craig, A. Desai, S. Kang, B. Reen,
S. Richardson, N. Seaman and D. Stauffer
Department of Meteorology
The Pennsylvania State University
University Park, PA
Penn State
•
Acknowledgements and
Collaborators
DIAL groups
– NASA Langley, LASE, Browell, Ismail et al
– CNRS France, LEANDRE, Flamant et al
– DLR Germany, DLR DIAL, Ehret et al
• University of Wyoming King Air team
– Field crew
– LeMone et al, NCAR
• Land surface modeling/fluxes
– ALEXI project, U. Wisconsin, J. Mecikalski
– NOAH LSM, Chen and Manning, NCAR
• Add ground-based profiling groups, NAST
• NCAR-ATD
– ISFF group
– Parsons, Weckwerth, Tignor, Baeuerele, many others
• UCAR/JOSS
• NSF Atmospheric Sciences Division (IHOP)
• NASA Land Surface Hydrology program (SGP97)
Penn State
overview
• Goals/background
• Products we propose to create
• Preliminary results
– Large scale ABL heterogeneity
– Small scale ABL heterogeneity
– Attempt to model ABL heterogeneity
Penn State
Background – land surface
processes and ABL development
• Modeling studies have suggested that land surface conditions are
critical to properly predict moist convection in the Great Plains
(Avissar et al). RAMS, cloud fields
• Surface observations have shown little climatological connection
between surface energy balance heterogeneity and mesoscale flow
(Shaw, Doran et al). OK surface met data
• ABL observations are often absent or scarce in previous studies.
The ABL is critical to this question.
• Where available, ABL observations have shown only modest
mesoscale flow in the presence of strong but fairly small scale (1020 km) flux heterogeneity (Sun et al, Ehret et al). BOREAS - DLR
• Larger-scale (~250 km) ABL heterogeneity has been observed and
tentatively linked to the surface energy budget (Desai et al, Reen et
al). SGP97 – LASE
Penn State
Goals
• Building blocks
– Document mesoscale heterogeneity in the atmospheric boundary layer
(ABL). DIAL, DOW, HRDL, UWKA
– Map the surface energy budget over the same mesoscale region.
ALEXI, NOAH, ISFF, UWKA
• Role of the land surface
– Examine the degree to which land surface heterogeneity is responsible
for ABL heterogeneity. MM5, observations
– Examine the potential for land-atmosphere interactions to focus the
initiation of moist convection. MM5, observations
• Data assimilation
– Examine the degree to which improved ABL and land surface data
improve model predictions of ABL development and moist convection.
MM5, observations
• Model development
– Evaluate the ability of ABL and land surface models to simulate the
structures observed during IHOP. MM5, observations, ABL and LS
model choices
• New area of focii?
– Mesoscale rolls – appeared on many BLH day, possibly important for CI
– Microscale structure of the entrainment zone
Penn State
Methods (to date)
• Airborne lidar. 200-300 km scale.
– Backscatter for ABL depth. ~10m x 10m resolution.
– Differential absorption lidar (DIAL) for ABL H2O mixing ratio
– Doppler lidar for turbulent vertical winds
• U. Wyoming King Air. 60 km scale.
– Turbulent variables, fluxes
• Surface flux towers
– Spaced along King Air flight tracks
• Remote sensing, land surface models. IHOP domain
– Map surface energy budget
• Mesoscale model. IHOP domain.
– Determine the degree to which the surface energy budget
governs mesoscale heterogeneity in the ABL.
• Collect observations for at least 10 days over the same
region. Go beyond case studies. All BLH days.
Penn State
Completed Missions
• 12 BLH missions with joint airborne H2O
lidar and flux aircraft operations.
• No cases that led directly to deep
convection.
• Dates spanning 19 May through 22 June,
2002.
Penn State
Penn State
BL Heterogeneity Mission Example
29 May, 2002
Expected Products
• High-resolution ABL depth and water vapor
maps for all BLH missions (joint with lidar
groups). Add ground-based profilers, NAST?
• Surface energy balance maps for all BLH
missions (joint with NCAR, UWisconsin).
• MM5 reanalysis fields for all BLH missions,
including airborne lidar data assimilation.
Suitable to submit to JOSS as merged “data”
products? Would IHOP scientists use these
products?
Penn State
Preliminary findings
• Surface energy budget heterogeneity was
extreme Kang
– Persistent, climatological east-west gradient
– Local variations due to recent precipitation
• ABL heterogeneity was evident
– East-west gradient was realized in different ways
depending on atmospheric environment Craig
– Some local heterogeneity was also persistent over
time, suggesting land-surface origins Kang, Craig
• Comparisons of ABL-LSM schemes within MM5
show a great deal of variability among model
formulations. Reen
Penn State
East – West moisture gradient
and its impact on the ABL
Penn State
Persistent west to east soil moisture gradient
Intense rainfall associated with frontal passage.
Station7(E)
Station4(C)
Station1(W)
Station 1 = west. Station 4 = central. Station 7 = east.
Penn State
East – west soil moisture gradient is reflected
in U. Wyoming King Air flux measurements
WEST: L=125 W m-2
Line represents 10km
UWKA latent heat
flux measurements.
station1
station2
station3
EAST: L=300 W m-2
Apparent error in
eastern flux towers
on this date.
Penn State
Penn State
East-west soil moisture gradient also evident
in indirect flux estimates derived via computer
models, and based on satellite surface temps.
SOUNDINGS (Dodge City)
19 May 12 UTC
Strong capping inversion
Strong surface energy balance gradient
29 May 12 UTC
Weak capping inversion
Strong surface energy balance gradient
Penn State
LEANDRE FLIGHT TRACKS
19 May 2002
29 May 2002
1845-1926 UTC
1839-1913 UTC
Strong capping inversion
Strong surface energy balance gradient
Weak capping inversion
Strong surface energy balance gradient
Penn State
Pre-front of 23-24 May. Strong capping inversion.
300 km scale CBL heterogeneity.
CBL depth as seen via lidar backscatter.
LEANDRE: 19 May 2002
West
East
35 km
Penn State
LEANDRE: 19 May 2002
West
35 km
EastPenn State
Post-front of 23-24 May. Weak capping inversion.
300 km scale CBL heterogeneity.
CBL depth as seen via lidar backscatter.
LEANDRE: 29 May 2002
West
37 km
East
Penn State
LEANDRE: 29 May 2002
East
West
37 km
Penn State
LEANDRE H2O VAPOR
29 May 2002
Penn State
Penn State
BL Heterogeneity Mission Example
29 May, 2002
LASE: 30 May, 2002.
An additional view of CBL heterogeneity with a weak capping inversion.
CBL depth via lidar backscatter, and CBL H2O content via DIAL.
Penn State
Visible Satellite: 30 May 2002, 2007 UTC
Penn State
Smaller scale heterogeneity:
Along the UW King Air flight track
Penn State
Eastern soil moisture conditions remain fairly
homogeneous throughout the study.
station7
station9
station8
Penn State
Western soil moisture conditions become quite
Heterogeneous, especially around 27 May.
station1
station2
station3
Penn State
U Wyoming King Air flux latent heat flux observations (line)
reflect the south to north soil moisture gradient along the
“Homestead track”
station1
station2
station3
Penn State
Penn State
BL Heterogeneity Mission Example
29 May, 2002
South
North
DLR lidar shows the context of the UW King Air
observations along this N-S gradient.
Is the ABL heterogeneity closely tied to soil conditions?
Pattern was repeated on multiple DLR Falcon passes over 3 hours.
Penn State
Moist soils, North; Dry soils, South.
NASA LASE backscatter from the NASA P-3.
Wavelet ABL top derivation, Davis et al, 2000.
250 km, N-S flight track in central Oklahoma.
Case study: Southern Great Plains
97 Experiment, 12-13 July, 1997
Desai et al, in prep; Reen et al, in prep
Penn State
Reen et al, in prep
Approx wet/dry soil line
South, dry
North, moist, recent rainfall
Attempts to model coupled land surface - ABL
development using MM5:
SGP97 example
•Spatial variability is difficult to reproduce. Role of the surface energy
balance is not entirely clear.
•Different ABL-LSM schemes give very different mean ABL heights
and mixing ratios.
Penn State
Good ideas?
• Centrally choreographed instrument
intercomparison work
• Centrally choreographed data assimilation
efforts
• Central guidance on the creation(?) of a
project reanalysis product
Penn State