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