Upload
buddy-melton
View
213
Download
0
Embed Size (px)
Citation preview
More on Wind Shear Statistics: Intercomparison of Measurements from Airborne DWL and Ground-
based Sensors S. Greco and G.D. Emmitt
Simpson Weather AssociatesCharlottesville, VA
Working Group on Space-Based Lidar Winds Wintergreen, VA 8 July 2008
Motivation
• Shear is a major component of atmospheric instability
• From space and airborne platforms, a Doppler wind lidar offers the capability to measure high resolution vertical profiles of the wind, thus providing a direct, vertically contiguous measure of shear
• Shear can be persistent as well as transient (representativeness issue)
Overview
• What is Wind Shear?• Wind Shear Climatologies• Sounding comparisons of winds and wind
shear– RAOBs– Microwave sounders– Airborne Doppler Wind Lidar (TODWL)
Wind Shear
• Wind Shear is defined in NOAA Technical Memorandum NWS FCST-23 as “a change in horizontal wind speed and/or direction, and/or vertical speed with distance, measured in a horizontal and/or vertical direction”
• As defined by the National Weather Service, Low-Level Wind Shear is wind shear of 5 m/s or more per 30m
(.169s-1) in a layer more than 60m thick within the lowest 600m of the atmosphere
Wind Shear
• Vertical wind shear is not a scalar quantity, but a vector. Using just “speed shear” will often underestimate the amount of shear present. Direction of the horizontal winds must be considered as well
• On benign days, wind shear values are typically < 0.08 s-1. Wind shear meeting official criteria is 0.169 s-1
Wind Shear Climatologies
• Very limited and usually averaged (hourly,monthly, seasonally, annually)
• Deep layer (850 -200mb) shear for tropics but no full column shear values
• Mostly based on tower level data (0 -150m)
- Central Plains network
Observations
Global Radiosonde Network
NOAA Profiler Network (Central US)
COOPERATIVE AGENCY PROFILERS
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
0
400
800
1200
1 = < -.052 = -.05 t0 -.043 = -.04 to -.034 = -.03 to -.025 = -.02 to -.016 = -.01 to zero7 = zero8 = zero to .019 = .01 to .0210 = .02 to .0311 = .03 to .0412 = .04 to .0513 = > .05
Wind Speed Shear (All Levels)Miramar CA 12Z RAOB
August 2007
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
0
200
400
600
800
1 = < -.052 = -.05 t0 -.043 = -.04 to -.034 = -.03 to -.025 = -.02 to -.016 = -.01 to zero7 = zero8 = zero to .019 = .01 to .0210 = .02 to .0311 = .03 to .0412 = .04 to .0513 = > .05
Wind Speed Shear (All Levels)Lamont OK 12Z RAOB
August 2007
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16SHEAR CATEGORY
0
1000
2000
3000
4000
5000
Number of Occurences
1 = < -.052 = -.05 t0 -.043 = -.04 to -.034 = -.03 to -.025 = -.02 to -.016 = -.01 to zero7 = zero8 = zero to .019 = .01 to .0210 = .02 to .0311 = .03 to .0412 = .04 to .0513 = > .05
Wind Speed Shear (All Levels)Miramar CA PROFILER - HIGH RES
August 2007
0 50 100 150 200 250Number of Occurneces
0
1000
2000
3000
Height (m)
WIND Shear for AUG 2007 Miramar, CA Profiler (High Res)
Category 3 - (-.04 to -.03)
0 50 100 150 200 250Number of Occurneces
0
500
1000
1500
2000
2500
3000
Height (m)
WIND Shear for AUG 2007 Miramar, CA Profiler (High Res)
Category 11 - (.03 to -.04)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16SHEAR CATEGORY
0
4000
8000
12000
Number of Occurences
1 = < -.052 = -.05 t0 -.043 = -.04 to -.034 = -.03 to -.025 = -.02 to -.016 = -.01 to zero7 = zero8 = zero to .019 = .01 to .0210 = .02 to .0311 = .03 to .0412 = .04 to .0513 = > .05
Wind Speed Shear (All Levels)NPS, CA PROFILER - HIGH RES
August 2007
TODWL
• TODWL - Twin Otter Doppler Wind Lidar • Joint ONR and NPOESS IPO research project• Flown aboard the Navy CIRPAS Twin Otter aircraft• Flights supported by Army, Navy and DARPA• Series of seven flight missions conducted near the
coast of Monterey, CA since 2002 (125 hours)• Most recent campaign in November 2007• Develop calibration/validation procedures for all
wind profiling systems
TODWL DATA & OBSERVATIONS
• Corrected for aircraft induced pointing errors• Corrected for lidar beam pointing errors• Employ threading near ground• Complete wind profiles every 250m• Accuracy of .05 m/s for wind observations• 25-50 m vertical resolution
TODWLscanner
STV
Particleprobes
SurfaceTemperatureSensor
Leg 1Leg 2
Leg 3
Leg 4
Leg 5Monterey Bay
November 12, 2007
0 2 4 6 8 10 12 14 16 18
WIND SPEED (M/S )
250
500
750
1000
1250
1500
1750
2000
2250
2500
HEIGHT (M)
NOVEMBER 12, 2007TIME RANGE: 1520 - 1530SW LEG 5 (PASSING OVER FT ORD)ORDER OF PROFILES (FROM NE TO SW):BLACK (S,D), BLUE (S,D), RED (S,D), GREEN (S,D), PURPLE (S,D)S = SOLID, D = DASHED
Leg 5 NE - SW
Intercomparisons
0 2 4 6 8 1 0 1 2 1 4W IN D S P E E D (M /S )
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
2 5 0 0
HEIGHT (M)
N O V E M B E R 1 2 , 2 0 0 7W IN D S P E E DB L A C K : F T O R D P R O F IL E R A T 1 5 3 5R E D : L ID A R P R O F IL E A T 1 5 2 5B L U E : L ID A R P R O F IL E A T 1 5 2 6
240 270 300 330 360WIND DIRECTION (DEG)
0
500
1000
1500
2000
2500
HEIGHT (M)
NOVEMBER 12, 2007WIND DIRECTIONBLACK: FT ORD PROFILER AT 1535RED: LIDAR PROFILE AT 1525BLUE: LIDAR PROFILE AT 1526
TODWL vs. microwave sounder
0 2 4 6 8 10
WIND SPEED
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
HEIGHT
NOVEMBER 16 NOONWIND SPEED PROFILES (DOWN)THICK: BALLOON SOUNDINGTHIN: LIDAR SOLID: 1156 #2 DASH: 1204 #7RED: NOON PROFILER
0 30 60 90 120 150 180 210 240 270 300 330 360
WIND DIRECTION
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
HEIGHT
NOVEMBER 16 NOONWIND DIRECTION PROFILES (DOWN)THICK: BALLOON SOUNDINGTHIN: LIDAR SOLID: 1156 #2 DASH: 1204 #7RED: NOON PROFILER
TODWL vs. Rawinsondes
November 16, 2007 Calibration Flight
0 2 4 6 8 10Wind Speed (m/s)
0
0.4
0.8
1.2
1.6
2
Height (Km)
1834 GMT - Blue1904 GMT - Black1934 GMT - Red2004 GMT - Yellow
NPS Profiler Wind Speeds (High Res)Nov 16, 2008
0 2 4 6 8 10Wind Speed (m/s)
0
1
2
3
4
5
Height (Km)
1835 GMT - Blue1905 GMT - Black1935 GMT - Red2005 GMT - Yellow
NPS Profiler Wind Speeds (Low Res)Nov 16, 2008
0 2 4 6 8 10Wind Speed (m/s)
0.4
0.8
1.2
1.6
2
2.4
2.8
Height (KM)
TODWL (1844 -1854 Ave) - BlueTODWL (1857 -1906 Ave) - RedTODWL (1909 - 1919 Ave) - BlackTODWL (1921 - 1930 Ave) - YellowTODWL (1932 - 1940 Ave) - Purple
Lidar Averaged Profiles (leg)Nov 16, 2007
0 2 4 6 8 10Wind Speed (m/s)
0
1
2
3
4
Height (KM)
NPS LoRes 1835 - Black SolidNPS HiRes 1835 - Black DashedTODWL (1844 -1854 Ave) - BlueTODWL (1857 -1906 Ave) - Red
NPS Profiler vs Lidar Averaged Profiles (leg)Nov 16, 2007
0 2 4 6 8 10Wind Speed (m/s)
0
0.5
1
1.5
2
2.5
3
Height (KM)
NPS LoRes 1905 - Black SolidNPS HiRes 1904 - Black DashedTODWL (1909 -1918 Ave) - BlueTODWL (1921 -1930 Ave) - Red
NPS Profiler vs Lidar Averaged Profiles (leg)Nov 16, 2007
-0.04 -0.02 0 0.02 0.04Wind Shear(sec-1)
0
1000
2000
3000
Height(m)
Black - TODWL Profiles (113)Blue - Profiler High Res (4)Red - Profiler Low Res (4)
Nov 16, 2007TODWLS vs Fort Ord Profiler (calibration mission)
1835 - 2005 GMT
Concluding Thoughts
• High resolution shear measurements represents a primary target of both current airborne and future space-based observations and a challenge to signal processing
• Shear represents a major source of bias and possible error in estimating an average wind over a layer
• Airborne lidar provide excellent data bases for simulating space-based DWL observations of shear.
Aerosol weighted shear processing
0 4 8 12 16Wind Speed (m/s)
0
500
1000
1500
2000
2500
Height (Above MSL)
Leg 5 (1520 - 1530) - W ind Speed Profiles
NE to SW Leg1520-1521 - Black1522-1523 - Blue1524-1525 - Red1526-1528 - Green1529-1530 - Yellow
-10 0 10 20 30 40SNR
0
500
1000
1500
2000
2500
Height (Above MSL)
Leg 5 (1520 - 1530) - SNR Profiles
NE to SW Leg1520-1521 - Black1522-1523 - Blue1524-1525 - Red1526-1528 - Green1529-1530 - Yellow
0 4 8 12 16Wind Speed (m/s)
0
500
1000
1500
2000
2500
Height (Above MSL)
Leg 5 (1530 - 1536) - W ind Speed Profiles
NE to SW Leg1530-1531 - Black1532-1533 - Blue1535-1536 - Red
-10 0 10 20 30 40SNR
0
500
1000
1500
2000
2500
Height (Above MSL)
Leg 5 (1530 - 1536) - SNR Profiles
NE to SW Leg1530-1531 - Black1532-1533 - Blue1535-1536 - Red
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
2 5 0 0
Height (Above MSL)
0 t o 3 3 t o 6 6 t o 9 9 t o 1 2 1 2 t o 2 0
Wind Speed (m/s)Leg 5
152015281537TIME (LST)
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
2 5 0 0
Height (Above MSL)
-4 . 9 3 t o 5 5 t o 7 . 5 7 . 5 t o 1 0 1 0 t o 1 5 1 5 t o 3 4 . 6 5
15201537 1528TIME (LST)
LEG 5
SNR
Profile 1
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60 70 80 90 100
Signal Strength
Height AGL (m)
Series1
Profile 1
0
500
1000
1500
2000
2500
0 2 4 6 8 10 12 14 16 18 20
Wind Speed (m/s)
Height MSL (m)
Actual wind
Unweighted 500m
Weighted 500m
Weighted 1000m
Signal strength
0
500
1000
1500
2000
2500
3000
0 10 20 30 40 50 60 70 80 90 100
Signal strength
Height AGL (m)
Signal strength
Profile 1530
0
500
1000
1500
2000
2500
3000
0 2 4 6 8 10 12
Wind speed (m/s)
Height AGL (m)
Actual wind
Unweighted 500m
weighted 500m
Weighted 1000m