News concerning the cloud microphysical measurements during...
Transcript of News concerning the cloud microphysical measurements during...
Thermodynamic correction of particle concentrations
measured by underwing probes on fast flying aircraft
Ralf Weigel, Peter Spichtinger, Christoph Mahnke, Marcus Klingebiel,
Armin Afchine, Andreas Petzold, Martina Krämer, Anja Costa, Sergej Molleker,
Max Port, Lucas Grulich, Andreas Minikin, Stephan Borrmann
ACRIDICON-CHUVA Workshop
News concerning the cloud microphysical
measurements during
ACRIDICON-CHUVA 2014:
-Christoph Mahnke-
Ilha Bela (Brazil), 01.03.2016
Ilha Bela (Brazil), 01.03.2016
CCP PIP
DLR HALO, right wing (A.Minikin, 2013) DLR HALO, left wing (A.Minikin, 2013)
CCP and PIP in HALO PMS-Configuration
Measurement principle of
optical array probes (OAP)
e.g. the CCP
CIPgs detector
pitot-tube
CDP detector
Source: Baumgardner and Korolev (1997)
Ilha Bela (Brazil), 01.03.2016
distance covered over Δt
����� = � · 1
�� · �� ·
1
∆�
= �
�����
Ingredients � particle number concentrations:
• Number of particles n,…
• …detected per time unit Δt,…
• …over which the sample area As is
penetrated by the air volume Vmeas .
flight direction Measurement principle of
optical array probes (OAP)
e.g. the CCP
Source: Baumgardner and Korolev (1997)
Source: Marcus Klingebiel
Ilha Bela (Brazil), 01.03.2016
Unaware the air speed
(e.g. no pitot tube)
� = �
�� · �� ·
1
∆������ = � ·
1
�� · �� ·
1
∆�
Alternatively: own air speed
measurements available
· ��
��
with the purpose
to correct
Nmeas� Namb
����� · ��
�� =
�
�� · ∆� · �� · ��
��
With own air speed
(with pitot tube)
����� =�
�� · �� ·
1
∆�
� = �
�� · �� ·
1
∆�
believing
PAS represents
particle speed
believing
TAS represents
particle speed
Hypothesis: None of these approaches really gives Namb
� = �
�� · �� ·
1
∆�� =
�
�� · �� ·
1
∆�
Different ways of treating the data
Ilha Bela (Brazil), 01.03.2016
distance covered over Δt
����� = � · 1
�� · �� ·
1
∆�
= �
�����
Ingredients � particle number concentrations:
• Number of particles n,…
• …detected per time unit Δt,…
• …over which the sample area As is
penetrated by the air volume Vmeas .
flight direction
Ilha Bela (Brazil), 01.03.2016
����� = � · 1
�� · �� ·
1
∆�
= �
�����
Ingredients � particle number concentrations:
• Number of particles n,…
• …detected per time unit Δt,…
• …over which the sample area As is
penetrated by the air volume Vmeas .
remains as suchremains as such
remains as such
Increased by linear
expansion in line with
flight direction.
� · 1
�� · �� ·
1
∆�
= �
���������
enlarged distance covered over Δt
≠
flight direction
Ilha Bela (Brazil), 01.03.2016
T1
p1
ρ1
v1=TAS
vp ≈ v1
T2>T1
p2>p1
ρ2>ρ1
v2=PAS
PAS<TAS
vp ≈ PAS
Fundamental
assumption:
otherwise
spheroidal drops
would generally show
distorted images
Ambient conditions
versus
Measurement conditions
Ilha Bela (Brazil), 01.03.2016
vp ≈ PASFundamental assumption:
for calibrations with spinning disk:
PAS is manually set to be equal to
disk’s rotation speed: ~24 m s-1
set PAS
HIGHER than
disk’s rotation speed
� scanning frequency increased
� particle is reconstructed based on more
slides than necessary � elongated images
set PAS
LOWER than
disk’s rotation speed
� scanning frequency decreased
� particle is reconstructed based on lesser
slides than necessary � squeezed images
dir
ect
ion
of
pa
rtic
lefl
ow
Ilha Bela (Brazil), 01.03.2016
���� =����� · ��
�� ·
1 + ��� − ��
�
2008!
"# · $
·1
��
���� = ����� · %
���� = �����· ��
��= ����� ·
��
����
��
Ambient conditions
versus
Measurement conditions
T1
p1
ρ1
v1=TAS
vp ≈ v1
T2>T1
p2>p1
ρ2>ρ1
v2=PAS
PAS<TAS
with Bernoulli‘s law
1
2��
� +&� +ℎ� =1
2��
� +&� +ℎ�
ΔT (or T2) calculated via increasing enthalpy
(Δh) accompanied with Δv.
Ilha Bela (Brazil), 01.03.2016
Three different positions of underwing probes
ML-CIRRUS instrumentation ⟺ ACRIDICON instrumentation
Outboard
position
Inboard
position
Intermediate
position
Ilha Bela (Brazil), 01.03.2016
Probe‘s individual PAS
measurement (ML-CIRRUS)
systematic offset between
CCP and NIXE-CAPS as well as
CCP and PIP of less than 10%.
� within uncertainty
Probe‘s individual static pressure
measurement (ML-CIRRUS)
Strong agreement between
Three independent instruments.
� Measurement seems robust!
Ilha Bela (Brazil), 01.03.2016
Impact of different corrections on PMS-measured number concentrations (ACRIDICON AC13)
uncorrected Nmeas vs PAS/TAS-corrected vs ξ-corrected Nmeas
- straight level flight with 215 m s-1 < TAS < 225 m s-1 (�� = 222 m s-1)
- liquid droplet regime
� spheroids are imaged as such
� eff. correction CCP & NIXE & PIP: 27-30 %
� eff. correction CCP & NIXE & PIP: ~12 %
Ilha Bela (Brazil), 01.03.2016
Icing problem of the pitot-tube airspeed measurement(CCP) at flight AC07
Corrupted CCP-PAS
measurement due
to icing!
Ilha Bela (Brazil), 01.03.2016
Parameterization of 1Hz-resolved CCP-PAS-values for ML-CIRRUS
PASCCP-Para = K0 + K1 * TAS + K2 TAS2
K0 = -12.789 ± 0.0552
K1 = 0.99788 ± 0.000631
K2 = -0.00095938 ± 1.75e-006
Reconstruction of the PAS gives us the possibility to:
• Rescue all Icing-corrupted CDP-Data
• Rescue big parts of the CIPgs-Data
• Depending on degree of false-imaging
• PIP-PAS reconstruction will follow (work in
progress)
Ilha Bela (Brazil), 01.03.2016
Note: data reassessed
concerning outliers!
Parameterization of calculated 1Hz-resolved ξ-values
for ML-CIRRUS
Outboard position Inboard position Intermediate position
� Comparatively compact behaviour as a function of TAS
> 130 000 single data points (> 36 flight hours)
flight dates
Ilha Bela (Brazil), 01.03.2016
ACRIDICON-CHUVA 2014 AC17: Cloud constrast (forested-deforested)
Leg1
Leg2
Leg1: Cloud contrast
• West: Forested area
• East: Deforested area
Leg2: Cloud contrast
• North: Forested area
• South: Deforested area
Ilha Bela (Brazil), 01.03.2016
ACRIDICON-CHUVA 2014 AC17: Cloud constrast (forested-deforested)
Leg1
ca. 120 km
1: Forested area 2: Deforested area
2 1 1 2 2 1Sample area:
Ilha Bela (Brazil), 01.03.2016
ACRIDICON-CHUVA 2014 AC17: Cloud constrast (forested-deforested)
Forested area Deforested area
843 hPa
812 hPa
753 hPa
Pressure level
Ntotal = 64 cm-3
Ntotal = 90 cm-3
Ntotal = 54 cm-3 Ntotal = 256 cm-3
Ntotal = 381 cm-3
Ntotal = 215 cm-3
Ilha Bela (Brazil), 01.03.2016
Distillate:
1) For a correction from Nmeas to Namb air compression (Δp and ΔT)
has to be considered!
2) the ξ-factor
a) originates from a thermodynamic perspective (accounting for Δp and ΔT)
b) demonstrated consistency over three underwing positions
c) is compact as function of TAS
d) has a plausible effectiveness as a function of TAS
Complete story with more datails is subject of publication at AMTD entitled:
Thermodynamic correction of particle concentrations
measured by underwing probes on fast flying aircraft
Ilha Bela (Brazil), 01.03.2016
Distillate:
4) ACRIDICON-CHUVA 2014 : Cloud contrast between forested and deforested areas.
a) Higher number concentrations over the deforested areas compared to the
forested areas
b) Broadening of the maximum of the size distribution with increasing altitude
c) No significant difference in the shape of the size distributions between the
forested and deforested area
3) Parametrization of the PAS as function of TAS gives us the possibility to:
a) rescue icing corrupted measurements (e.g.: CDP, CIPgs, PIP)
b) calculate the PAS for probes without an own pitot-tube
(more wing positions will follow)
Ilha Bela (Brazil), 01.03.2016
Thanks for
your attention!
Ilha Bela (Brazil), 01.03.2016