aerosol indirect effect experiments on the j-31
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Aerosol Indirect Effect Experiments on the J-31
In coordination with the R/V Ron Brown
(Radar data: Pavlos Kollias)
Science Objectives
• Study effect of aerosol on cloud microphysics
• Compare different drop size retrieval methods– Remote sensing from surface (radar/wave on RHB)– Remote sensing from J-31(SSFR)– Remote sensing from P-3 (MIDAS, SSFR)– In-situ from P-3 (FSSP)
J31: Aerosol and cloud radiative properties; AOT, aerosol extinction profiles, cloud optical depth, drop size, LWP
Instrumentation: AATS-14, SSFR
P-3:Emphasis on gasphase chemistry, aerosol size distribution / composition and cloud radiative properties;longer range, chasing pollution plumes
Relevant Instrumentation: SSFR, MIDAS, FSSP
LWP
Satellite
Lidar: backscatterprofiles
Surface aerosol
microwave radiometer
effective radius, re (z)
Radar
R/V Brown
Sunphotometer
AATS-14 + SSFR:re ,d , , LWP(z) J31
Satellite
Cloud free
Aerosol: n(a), , , chemCloud: re , w, LWP
AOT,(z)
Method for Indirect Effect Studies
• Use Lidar backscatter or extinction as proxy for CCN• Various re retrievals
– Requires non-precipitating warm clouds (single layers) with high enough bases for lidar to sample aerosol (identified 5 possible candidates)
Effe
ctiv
e ra
dius
aerosol
Example from ARM/SGP
IE= - dlnre/dln
Stratocumulus observations after another front passage (14-15 July). The MWR measurements show good correspondence with the reflectivity structure and the ceilometer data along with the reflectivity data can be used to infer the cloud thickness
Cloud Fraction during NEAQS from RHB
A ceilometer-based distribution of hourly averaged cloud fraction during NEAQS. More than30% of the time, clear skies were observed, while overcast cloud and precipitation conditionsoccurred 25% of the time.
NEAQS Leg-averaged cloud fraction. Note: During leg 2,
More middle and upper clouds were observed and less BL clouds
Ceilometer cloud base time series
Ceilometer Hourly mean cloud base. Note: During the second leg very few boundary layer clouds were observed. Furthermore as the lower panel shows, many of the low level bases in leg one were associated with fog and frontal precipitation
Precipitation hourly fractional coverage as observed by the ceilometer.High fractional coverage (close to 1) may mean continuous precipitating conditions
Fra
ctio
nal C
over
age
He
igh
t, km
Clear Skies LWP Overcast BL clouds LWP
LWP time series: Red shows periods with stratus clouds
Components of aerosol-cloud interactions
• Cloud properties: re , d , reflectance,
• Aerosol properties: size distr., composition, f(RH), mass loading, extinction, scattering, CCN
• LWP
Verification/intercomparison of independent components through redundant measurements
Changes in cloud parameters as a function of changes in aerosol parameters
Detecting and Quantifying AIE
(re , d , ) (aerosol size distr., extinction, etc)
At constant LWP
_ d ln re
d ln
Cloud Aerosol
Changes in cloud parameters (re , d , ) as a function of changes in aerosol parameters
_ d ln d ln
_ d ln d
d ln
CCN proxies
14:00 UTC
RadarReflectivity
Precipitation scavenging by Altocumulus July 10th
Cloud base~ 3km
Sca
tteri
ng
(R, G
, B)
20:00 UTC
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