more on wind shear statistics: intercomparison of measurements from airborne dwl and ground- based...

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