Post on 17-Jan-2016
transcript
The Effects of Surface Heterogeneity on Boundary-Layer Structure and Fluxes
Margaret LeMone and Fei Chen, with acknowledgments to collaborators:
T. Horst, S. Semmer, R. Roberts, Jim Wilson (NCAR) B. Geerts (Univ. of Wyoming) R. Cuenca (Oregon State) + R. Grossman
(CoRA) + P. Blanken (CU) + D. Niyogi (NCSU) + E. Small (CU) + D. Stauffer and K. Davis (PSU), T. Holt (NRL)
Goals: 1. Collect and analyze IHOP surface/vegetation/soil/aircraft
data 2. Validate and improve models (Noah LSM, CLM, HRLDAS,
Coupled WRF/Noah system)3. Investigate the relationships between land variability and
convection initiation
15 King-Air BLH Missions + 10 NCAR Surface, Soil, and Vegetation Stations
ABLE Network
OK MesonetWestern TrackSites 1, 2, 3CU station 10
Central TrackSites 4, 5, 6
Eastern TrackSites 7, 8, 9
Characteristics of the Flight Tracks
The Eastern Track
Compare CASES-97To IHOP
David Gochis (left) and Bob Grossman (right)
Eastern Track:Radiometric Surface Temperature
IHOP: Riparian areas warm
CASES97: Riparian areas cool
Winter wheat effect?
Eastern Track: Potential Temperature
IHOP: West warm
CASES97: Center warm
CASES-97: Mesoscale Circulations
Flight Track
Evaluation of flux measurements for relating to surface heterogeneity
Lx = record lengthF = flux (average w’s’)F = turbulence integral scalerw’s’’
2 = correlation between w’ and s’
2''
2''
2
1
12
sw
sw
x
FF
r
r
LF
1. Statistics
2. Adherence to surface energy balance constraint:
H + LE = Rn – G ~ constant spatially H = sensible heat flux LE = latent heat flux Rn = net radiatioin G = heat flux into ground
3. Existence of horizontal variability
June 17, 20, 22 composite (21 legs)
17 J 201 deg at 7.7 m/s20 J 163 deg at 5.3 m/s22 J 179 deg at 9.4 m/s
Last rain on15 June
For comparison…CASES-97 Sensible Heat Flux (H)
-96.9o is site of lowH; maximumshifted to east
CASES-97 LE (-96.9o High LE)
Net result of flux difference: boundary-layer depth 150-250 m deeper at west end of track
17 June – W 250 m deeper than E20 June – W 150 m deeper than E22 June – W 240 m deeper than E
Eastern Track Synthesis reinforces findings of Grossman et al. 2004.
Land use affects radiometric surface temperature (Ts),potential temperature () , fluxes (H and LE),
and turbulence level (w’2)
Ts, , H, w’2 higher and LE lower over dormant vegetation; reverse for green vegetationVegetation related to terrain April-early May (CASES): Winter wheat to W and
in riparian zones green, grass dormant late May-June (IHOP): Grass green, winter wheat
senescent and then harvested.Soil moisture effect less obvious (long drydown for 17,20, 22 June)
Western Track: Radiometric Surface Temperature
Rainfall:16-17 May < 5 mm23 May ~ 3 mm26-27 May: 20-30 mm
in north to >80 mm to south
4-5 June ~15-20 mm
Silty Clay Loam Sandy Loam Soils Land cover
Air Temperature
Rainfall:
16-17 May < 5 mm 23 May ~ 3 mm26-27 May: 30-30 mm north 90 mm south 4-5 June 15-20 mm
Distribution of Fluxes (Sensible Heat)
177/13.2
191/4.9
133/2.5199/10.6
Distribution of Fluxes (Latent Heat)
29 May 2002: Contrast Between Station 3 (north) and Station 1 (south) ~50 km apart
Site 1 (western track) Site 3 (western track)
rain
Soil moisture
Net RadLatent heat
Sensible heat
Site3: drier, larger sensible heat flux
Turbulence – 29 May 2002
Wyoming Cloud Radar: Independent Confirmation of More vigorous BL to north on 29 May
NORTH – More Vigorous Convection
SOUTH – Less Vigorous Convection Bart Geerts
Synthesis for Western Track
Potential temperature H, and Ts larger tonorth most days (but not all)-- Sandy soil to north (better drained)-- More rain to south
29 May strong heterogeneity due heavy rain onsouth end of track 2 days previous.
Mesoscale variability on some days of currentlyunknown origin
IHOP Boundary Layer/Surface Data
• Data sets completed – Near-surface weather conditions, PAR, surface incoming and net radiation
(full component at sites 1,8, and 9), precipitation, surface heat fluxes, ground heat flux
– Latent heat fluxes recalculated from energy budgets– Soil bulk density, soil texture, saturated hydraulic conductivity, unsaturated
hydraulic conductivity function, thermal conductivity, and the soil-water retention function
– Weekly vegetation data: NDVI, leaf area index (LAI), stomatal resistance, transpiration
– CO2 concentrations at sites 1 and 8– MODIS data – Diurnal cycle of stomatal resistance and transpiration for a few selected
sties– Aircraft fluxes and NDVI along the flight tracks– Available @ www.rap.ucar.edu/projects/land/IHOP/index.htm
• Data sets being processed – Soil moisture content, soil water tension (potential), and soil temperature
profiles from the surface to a depth of 90 cm (about seven weeks). Three profiles at sites 1 and 9
– Landsat data
Modeling and Analysis Effort
• Validate and improve LSMs– Weather Community Noah LSM (CU/NCAR, NCSU/NCAR): – CLM (CU/NCAR)
• Verify WRF/Noah LSM coupled model (NCAR)• Verify high-resolution land data assimilation
system (HRLDAS) • Understand relationships between soil moisture
and convection initiation (extension of our USWRP work)
High-Resolution Land Data Assimilation System (HRLDAS) : Capturing Small-Scale Variability
• Input: – 4-km hourly NCEP Stage-II
rainfall– 1-km landuse type and soil
texture maps – 0.5 degree hourly GOES
downward solar radiation – 0.15 degree AVHRR vegetation
fraction – T,q, u, v, from model based
analysis• Output: long term evolution of
multi-layer soil moisture and temperature, surface fluxes, and runoff
4-km HRLDAS surface soil moisturein IHOP domain 12 Z May 29 2002
High-Resolution Land Data Assimilation System (HRLDAS) Concept
Run uncoupled LSM on the same grid as MM5/WRF to avoid:• Mismatch of terrain, land use
type, soil texture, physical parameters between sources of soil data and NWP models
• Need for interpolation
4-month (2002) HRLDAS Soil Moisture vs Oklahoma Mesonet Observation
Surface (0-10 cm) volumetric soil moisture averaged for Mesonet 62 stations
IHOP Data Improve HRLDAS
monthly average diurnal cycle of downward solar radiation fluxes (9 sites)
GOES derived downward solar radiation have high bias for low solar angle
An adjustment of radiation input has been made to HRLDAS
14:00
Refractivity
IHOP Refractivity Hourly HRLDAS Evaporation (mm)
Refractivity
12:00 12:00
14:00
IHOP Refractivity Hourly HRLDAS Evaporation (mm)
18:00
Refractivity
16:00
Refractivity
16:00
18:00
Comparison between WRF/Noah (10-km) and Wyoming King Air data
Surface heat flux along the western leg valid @ 19Z 29 May 2002
Comparison between WRF/Noah (10-km) and Wyoming King Air data
Variance of surface heat flux along the western legvalid @ 19Z 29 May 2002
Where from here
Generalize fluxes using surface, aircraft, satellite infoUse data to test models (LSMs, WRF PBL, CI)
How much can models do?How can we improve models?Does this improve prediction of convective
initiation?
Iterate….
Comparison between HRLDAS (4-km) and Wyoming King Air data
Surface heat flux along the western legvalid @ 19Z 29 May 2002
Comparison between HRLDAS (4-km) and Wyoming King Air data
Variance of surface heat flux along the western legvalid @ 19Z 29 May 2002