marc schröder et al., fub bbc workshop, leipzig, 05.´02 the airborne research platform of the fu...

Marc Schröder et al., FUB BBC Workshop, Leipzig, 05.´02

The airborne research platform of the FU Berlin: Overview of measurements taken during the BBC campaign and

presentation of first products and analysis

Marc Schröder, Thomas Ruhtz, Eyk Bösche,Jürgen Fischer

Institut für WeltraumwissenschaftenFreie Universität Berlin

Germany


Table of contents

• Overview of measurements

• Calibration

• BBC casi data catalog

• casi cloudmask

• Statistical characterisation of clouds


Overview of measurements

Instrument

casi

FUBISS classic

HDRAD

FUBISS extended

HMR, G12

MIDAC

Description

Compact airborne spectrographic imager, nadir radiances (vis)

FUB integrated spectrographic sys-tem (radiances): 1 nadir,1 zenith(vis), 1nadir (highvis), 1 nadir (NIR)

Radiometer from the University of Heidelberg, 4 visible channels

Irradiances (vis), nadir, zenith

Flight attitude (20 Hz), GPS (10 Hz)

Fourierspectrometer (5-17 m)

Status

ok

ok, except for NIR

ok

no

HMR since 20.09., GPS ok

no

Amount

54 G

2 G

9 M

4 G

0.5 G

1 G


Calibration

examplary results for FUBISS vis nadir

absolute calibrationspectral calibration


Calibration: Spectral comparison

• Hintergrund • Radiative smoothing • (Bounded) cascade models• Multifraktalität

• data taken from the 22.09.01 leg04

time: 10.223 utctime: 10.292 utc


Calibration: Time series comparison

• data taken from the 22.09.01 leg04

wavelength: 753 nm


BBC casi data catalog

• Hintergrund • Radiative smoothing • (Bounded) cascade models• Multifraktalität


BBC casi data catalog: Track overview

start time stop time section lengthleg01 leg02 leg03 leg04

09:30:48 10:31:17 10km length: 28.69km / sections: 2length: 30.22km / sections: 3length: 29.27km / sections: 2length: 57.11km / sections: 5

Date: 010928 Leg: 02


BBC casi data catalog: Images

34.2°

altitude

swath

• top of image correspondes to geograhpic north

casi


casi cloudmask: Algorithm development

casi nadir radiances, one received over cloud, the other over meadow, normalised

to the respective radiance at 780 nm

define ratio:r = L(490 nm) / L(780 nm)

find thresholds:• cloud if r rT and

• cloud if L(490 nm) LT(490 nm)


casi cloudmask development:Thresholds

histograms of casi nadir radiances at 490 nm and the ratio r,data from 13.09.01, leg5

thresholds: rT = 0.5 and LT(490 nm) = 60 Wm-2sr-1m-1


casi cloudmask development:Cloud shadow on clouds

white: cloudmask with previous condition

only

2nd condition: rT 1.35 and LT(490 nm) 35 Wm-2sr-1m-1

gray: advanced cloudmas-king technique

23.09.01 pm, leg2


casi cloudmask: Results I

• data from 23.09.01 pm, leg6


casi cloudmask: Results II

• data from 18.09.01, leg7


casi cloudmask: Results III•

data

from

22.

09.0

1, le

g1


Power spectra

Definition:

Scale invariance:

• stationarity if

• stationary incre-ments if

E(k) ~ |F(k)|2

E(k) ~ k-

< 1

1 < < 3

314 m

=2.52

=1.37

• data from 20.09.01, leg3 • cloud fraction b = 0.97


Structure function analysis

1) (r;x) = (x+r) - (x) = i+r - i

with i=1,...,N-r and N=L/l

2) < |(r;x)|q > ~ (r/L)(q)

with q0

Results for H(q) = (q) / q

• small scales r: H(q=1) = 0.47• large scales r: H(q=1) = 0.22


• small scales r: C(q=1) = 0.11• large scales r: C(q=1) = 0.07

Singulare measures

1) (1;x) = (x+1) - (x) = i+1 - i

with i=1,2,...,N-1 and N=L/l

2) (1;x) = |(1;x)| / <|(1;x)|>

with <|(1;x)|> = 1/(N-1)|(1;x)|

3) (r;x) = 1/r (r;x)

4) <[(r;x)]q> ~ (r/L)-K(q) with q0

Results for C(q) = K(q) / (q-1)and C(q=1) = K´(q) |q=1


Summary

• calibrated level 1b data for casi and FUBISS highvis, shortly available: FUBISS vis (nadir, zenith)

• delivered level 0b data to the IUP

• BBC casi data catalog, available for each day

• casi cloudmask, partly processed

• statistical characterisation of clouds: to be completed for days with high cloud fraction

marc schröder et al., fub bbc workshop, leipzig, 05.´02 the airborne research platform of the fu...

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