Post on 06-Jan-2016
description
Optical particle sizing in vertically inhomogeneous turbid media
Alexander A. Kokhanovsky, Vladimir V. RozanovInstitute of Remote Sensing, Bremen University
P. O. Box 330440 Bremen, Germany
alexk@iup.physik.uni-bremen.de
Contents
• Introduction• Functional derivative of reflectance• Algorithm• Application to synthetic data• Conclusions
Functional derivative of reflectance
_
ln,
ln ( )a ef k k kef k
RS z f z
a z
1
_
0
( )
( )a ef efef
RR a z dz
a z
z=Z/H
variation of droplet size at depth z
_ _
1
/ ,kN
ef k ef ka ef a ef k
k ef
a z a zR R S z
a z
efa z
plots
00
,ˆ, , ,
4
dSS P S d B
d
0ˆ, ,surf
AS R S d
,0 0S
Upwelling diffuse radiation at the bottom
Downweling diffuse radiation at the top
0 0 0E I
Solar radiation at the top
Theory
SCIATRAN: software package for the solution of direct and inverse problems of atmospheric optics
(Rozanov et al., 2011)
Free download: www.iup.physik.uni-bremen.de/sciatran
Results of calculations
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14
1.0
1.2
1.4
1.6
1.8
2.0 = 1.0a
ef=12m
SZA = 60degreesVZA = 0degrees
z, k
m
|S|, km-1
0.865m 1.24m 1.6m 2.13m 3.7m
0.0 0.1 0.2 0.3 0.4
1.0
1.2
1.4
1.6
1.8
2.0
= 5a
ef=12m
SZA = 60degreesVZA = 0degrees
z, k
m
|S|, km-1
0.865m 1.24m 1.6m 2.13m 3.7m
0.0 0.2 0.4 0.6 0.8 1.0
1.0
1.2
1.4
1.6
1.8
2.0
= 10a
ef=12m
SZA = 60degreesVZA = 0degrees
z, k
m
|S|, km-1
0.865m 1.24m 1.6m 2.13m 3.7m
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
1.0
1.2
1.4
1.6
1.8
2.0
= 20a
ef=12m
SZA = 60degreesVZA = 0degrees
z, k
m
|S|, km-1
0.865m 1.24m 1.6m 2.13m 3.7m
0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6
1.0
1.2
1.4
1.6
1.8
2.0
= 50a
ef=12m
SZA = 60degreesVZA = 0degrees
z, k
m
|S|, km-1
0.865m 1.24m 1.6m 2.13m 3.7m
0 2 4 6 8 10
1.0
1.2
1.4
1.6
1.8
2.0
= 100a
ef=12m
SZA = 60degreesVZA = 0degrees
z, k
m
|S|, km-1
0.865m 1.24m 1.6m 2.13m 3.7m
Algorithm
,
,
a z A zB N const C
a A z B N C
1 2 3
1ˆ ˆ ˆ ˆ ˆ ˆ ˆ, , [ ]T T T T
R c A c B c C
y cx c y c cx x c c c y
2 2
1 1
, ,z z
z z
a z N zR K z dz K z dz
a z N z
Results of retrievals for synthetic data
4 5 6 7 8 9 10 11 12 13 14 15 161.0
1.2
1.4
1.6
1.8
2.04 5 6 7 8 9 10 11 12 13 14 15 16
solid lines - exact profiles
he
igh
t, km
effective radius, m
865nm1240nm1600nm2100nmnaidr,SZA=60degA=0
N_t
1/cm3
N_r
1/cm3
COT(true
)
COT
(retrieved)
ER profile
(true),
ER profile
(retrieved),
ER(retrieved
using
SACURA),
40 39.2 9.5 9.7 15-11.25-7.5 14.9-11.4-7.9 13.0
40 39. 11.5 11.5 15-12.5-10 14.9-12.7-
10.5
14.3
LWP(inh)=73.3kg/m^2, LWP(hom)=83.9kg/m^2, difference:16.6kg/m^2
0.5-0.9km
Conclusions
• It is possible to retrieve vertical profiles of effective radius of droplets in clouds using passive spectral measurements in some cases
• The accuracy of the technique is higher for moderately thick clouds (COT=10-30)
• The new approach enables the improvement of the liquid water path estimation