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Institut für
Physik der Atmosphäre
Institut für
Physik der Atmosphäre
High Resolution Airborne DIAL Measurements of Water Vapour and Vertical Humidity Fluxes during IHOP
Christoph Kiemle, G. Ehret, A. Fix, H. Flentje, G. Poberaj, M. Wirth (DLR)R. M. Hardesty, W. A. Brewer, S. P. Sandberg (NOAA)
6. ISTP, Leipzig, 17.9.2003
Overview
• Differential-Absorption-Lidar (DIAL) in the DLR Falcon aircraft• High resolution water vapour measurements of the boundary layer• Co-located wind lidar measurements and vertical humidity fluxes
Institut für
Physik der Atmosphäre
IHOP Objectives and DIAL Performance
IHOP 2002missions
Objectives Falconflights
H2Odata
(hh:mm)
aerosoldata
(hh:mm)
H2O /aerosol
in %
BLheterogeneity
11 10:21 25:57 39,9
BL evolution
Improve understanding of the relationshipbetween atmospheric water vapor,surface fluxes and boundary layer
processes as they relate to quantitativeforecasts of precipitation
2 2:29 5:09 48,1
ConvectionInitiation
3 3:19 9:32 34,8
Low level jet
understand and predict the processesthat determine where and when
convection forms5 4:34 10:43 42,7
TOTAL 21 20:43 51:21 40,4
Institut für
Physik der Atmosphäre
H2O DIAL: Operators’ seat
with quick-look displayH2O DIAL: Telescope, detectorsand passive cooling unit
On board the DLR Falcon
Institut für
Physik der Atmosphäre
DIAL System Parameters and Set-up
Wavelength(nm)
927 1064 532
Pulseenergy (mJ)
12 50 40
Repetitionrate (Hz)
50(on/off)
100 100
Pulselength (ns)
7 15 11
Bandwidth(GHz)
0.14 / 90 0.05 0.05
Detector Si:APD Si:APD(s&p pol)
PMT(s&p pol)
FilterFWHM (nm)
1 1 1
Filter trans.(%)
65 40 55
Telescope Cassegrain, Ø35 cmfield-of-view: 1 - 2 mrad
Dataacquisition
14 bit, 10 MHz
Institut für
Physik der Atmosphäre
T,P,q
u,v,w,TAS
Dropsondes:u,v, P,T,q
HRDL:Horizontal & vertical wind speed
DIAL:H2O, AerosolsW'u,v
Falcon payload during IHOP_2002
Institut für
Physik der Atmosphäre
H2O DIAL Comparisons with Dropsondes
1
2
3
4
5
6 8 10 12 14
100.21W, 36.56N
June 9, 2002, 12:51 UT
H2O DIAL
Dropsonde
H2O Mixing Ratio [g/kg]
Alt
itu
de
[km
]
1
2
3
4
5
2 4 6 8 10 12 14
102.71W, 36.55N
June 9, 2002, 13:17 UT
H2O DIAL
Dropsonde
H2O Mixing Ratio [g/kg]
Alt
itu
de
[km
]
Institut für
Physik der Atmosphäre
High Resolution Backscatter and Water Vapour Cross Section
H2O data: 73 m hor. res., 100 m vert. res. in near range, 300 m in far range; overall stat. error 7%
Institut für
Physik der Atmosphäre
Water Vapour Spectra and Variance Profile
0.0 0.2 0.4 0.6 0.8 1.0 1.2
km asl.
water vapor variance profile (g/kg)
uncorr. stat. err. variance (dashed)
2
3.0
2.5
2.0
energy spectra of horizontal water vapor series at 2450m asl.
0.0001
0.001
0.01
0.1
(g/kg)2
10000 1000wavelength [m ]
energy spectra of horizontal water vapor series at 1820m asl.
0.0001
0.001
0.01
0.1
(g/kg)2
10000 1000wavelength [m]
Institut für
Physik der Atmosphäre
Method for Estimating the Statistical (Random) Error
autocovariance of horizontal water vapor series at 1820m asl.
-0.2
0.0
0.2
0.4
0.6
(g/kg)2
-2000 -1000 0 1000 2000 3000 4000lag [m]
1.0
1.5
2.0
2.5
3.0
3.5
0 10 20 30
Mean of 450 profiles with zeff = 100 m, x = 146 m (Reference = High resolutions)
Mean of 450 profiles with zeff = 150 m, x = 146 m (Low vertical resolution)
Mean of 225 profiles with zeff
= 100 m, x = 292 m (Low horizontal resolution)
IHOP, 7 June 2002, 17:39 - 17:46:30 UTC
Rel. Stat. Uncert. of Water vapor Mixing Ratio (RMS), %H
eig
ht a
.s.l.
, km
2321 zxq
q
σ2q,instr.
σ2q, atmos.
qerrorRMS noise
Assumption: hor. homogeneity DIAL resolution scaling law
Institut für
Physik der Atmosphäre
High Resolution Water Vapor and Vertical Wind
-101.92 -101.90 -101.88 -101.86 -101.84 -101.82lo ng itud e
1.01.5
2.0
2.5
3.0
heig
ht (k
m)
1 .01.5
2.0
2.5
3.0
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 g /kg
DLR DIAL wa te r va p o ur m ixing ra tio
0 2 4 6 8 10d ista nc e (km )
1.5
2.0
2.5
3.0
3.5
heig
ht (k
m)
1 .5
2.0
2.5
3.0
3.5
-3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 m /s
NO AA HRDL ve rtic a l wind ve lo c ity
DLR-DIAL:
x = 150 m
y = 150 m
NOAA-HRDL:
x = 150 m
y = 150 m
Institut für
Physik der Atmosphäre
Co-located Airborne Water Vapour and Wind Lidars
Institut für
Physik der Atmosphäre
Estimation of Latent Heat Flux Profile by Eddy Correlation
Flux F = w’q’ q’ = q - q
statistical error (solid):
σ2F, instr. = Δt/T σ2
w atm. σ2q, instr.
Ritter et al., JGR, 1990
sampling error (dashed):
σ2F, sampling =
2 ISF/T (F2 + σ2w atm. σ2
q, atm.)
Lenschow and Stankov, JAS, 1986
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