ARM Aerosol Working Group IOP Meeting Agenda

December 11, 2002 (8 am -- 4 pm) NASA Ames Visitors Center

1\. Welcome (Ferrare) (8:00)

2\. Meeting Logistics (Strawa) (8:05)

Logistics, lunch \$15

3\. Overview of IOP objectives (Ferrare) (8:10)

Cress, cont. resolution WILL affect us unless resolved in Jan.

Objectives:

> 1: absorption and aot closure
>
> How well do CARL and IAP measure these, can surface measurement be
> used aloft?
>
> 2\. Clousure of irradiance and flux under low AOT
>
> 3\. CCN and clouds, use lidar and surface measurement to infer CCN at
> cloud base
>
> 4\. Indirect Effect and Clouds: how does cloud drop respond vs changes
> in aerosol ext. for similar water paths?

Schmid discussed relative success of past AOT, abs closure experiments,
current expectations. Also outline instruments used in previous and
current closure experiments.

Desire vertically resolved aerosol properties over SGP

Motivation: unrealistic SSA, no closure IAP, needed for input to BBHRP

Address ext closure, abs closure

Closure means: in situ measurements of aerosol properties explain solar
direct atten. by aerosol layer

Ghan outlined CCN closure exp

Q is ext or backscat more closely related to CCN? Showed curves with
different peaks --\> this is a testable retrieval. Measure profile of
size dist and comp. Compare CCN profile scaled by extinction.

Feingold, indirect effects. General idea is to provide basis for
validating satellite inferred indirect effect.

Presented results with backscat equiv. f(RH) vs r_e

Tho is high, it is reduced by constraining to similar LWP

Schwartz sfc chem. and microphys.

> Direct effect holy grail

Sources of aer and precursor  transport models  aersol loading and
properties 

> Mie scattering etc.  aer opt props ...

surf meas are long term while aircraft or not.

List of instruments and/or PI:

Wang, BNL

PILS by Lee (chem. composition meas)

Also total organic carbon (Lee)

AMS : size reslved chem.. comp. not as quantitative as PILs

OC-EC analysis (Kirchstetter) also meas ext of C?

Aerosol ionic composition (Schwart asks: routine at CART, A: yes.) Maybe
need higher temporal resolution (currently daily)

Aersol opt prop meas

Aerosol scattering Neph at 3 lambda

Green scat as f(rh)

...

closure experiments

local optical prop closure

hygroscopic closure \\

mass closure \| hanging off 1 micron inlet? Under discussion.

CCN closure /

This went VERY fast, luckily also at:
www.tap.bnl.gov/arm_acp_aerosol-iop

4\. Brief Status Report of Measurements/Instruments (8:50)

**4.1 Summary of Reno Aerosol Optics Study (Sheridan)**

-   Objectives: characterize new and exist instrum.

-   \* Quantify uncertainty, etc. of aer lighy abs coef used by NOAA and
    ARM

-   derive methods for determ spectral aerosol abs from multi-lambda
    meas of abs and (ext -- scat)

> all done at low RH (primary external mixtures)
>
> Summary of results

-   agreement of standard methods for abs is +-5%

-   PSAP agrees with standard within same 5%

-   Filter transmission methods (PSAP, aethalometer) require improved
    corrections for mult scat and filter loading effects

-   Cavity ringdown ext cells appear to be have low bias by 10-15%
    (relative to classical ext and scat+abs

-   All results for low RH (lt 20pct) externally mixed black and white
    aerosols

> Continuing annals

-   compare kerosene soot with diesel soot and carbon vane pump exhaust

-   comare run-avg to time-series data

-   derive lambda-dep of abs to extend ext --sca cals to ovther lambda

-   derive corrections for filter base methods at all lambda

-   investigate reasons for low cavity ringdown

**4.2 Surface IOP measurements/aerosol trailer (Sheridan)**

additions to existing AOS measurements for IOP

-   photoacoustic abs 532nm

-   three-lambda ext cell

-   filter sampler for aer TC,OC,BC (kiirchstetter/novakov)

-   CCN (Hudson), probly too big for AOS, in GIF instead

-   PILS (Lee)

-   Ultrafine size dist (Wang)

-   Aerodyne mass spec (Worsnop), GIF

-   Size-segregated aerosol com, 3hr time resolution (Cahill), maybe AOS

**4.3 SMART measurements (Ji)**

> First trailer, contributions for Radiative closure, faster more
> channels photometer
>
> Second trailer, probably won't be deployed...

-   NOx, CO, SO2, O3

-   3 lambda neph

-   3 single lambda neph

-   impactor

**4.4 CCN surface measurements (Hudson)**

good comparisons between two CCN instruments, one over large range (1%
to 0.01%;), one narrow (0.1% to 0.01%).

Also nice agreement in differential plot.

Have extended measurements to .001or .002% equivalent to about 100-1000
nanometers

Could do size/supersaturation measurement

**4.5 Photoacoustic (Arnott)**

1.  ground based unit ready. May have 2 lambda ready for IOP 532nm and
    675or1047

2.  Trying to reduce size for aircraft use. Parts are being machined.
    675nm would match NASA CRD

3.  If necessary could use existing unit for aircraft.

> Aircraft leg lengths increases with altitude from \~7km at low alt to
> 75 km at hi alt

**4.6 CRD (Strawa)**

Aircraft-designed so pretty small... twin-otter rack-mountable

Uses CW-CRD technique

Measures at 690nm and 1550 nm

Discrepancy comments...

-   CRD agree with one another but

-   Are below nephelometer measurements, why? Not yet sure... January
    comparison planned.

-   On upside, agreement seems to be getting better, finer corrections
    are now the concern

**4.7 Stabilized Platform (Bucholtz)**

Flux radiometers, Kipp and Zonen modified for aircraft apps.

No real news regarding stabilized platform, funding issues (due to
continuing resolution?)

Date is so late that even with funding it's not clear if target is
reasonable now...

**4.8 SSFR (Pilewskie)**

instr. Details on web site

Will be able to support cloud liquid path initiative

Plot of dwnwell flux at 1600nm shows spikes for turns and otherwise
nicely smooth

Some problems with stabilized platform, incomplete run.

**4.9 Sun photometer (Schmid)**

Added new channel to help with large particles but otherwise as
previously deplyd.

Pilewski measures upwelling and downwelling flux. At multiple levels
yields flux divergence.

From ace asia, ssa of 0.8 too low, .9 too high, forms basis of
retrieval.

Without stabilized platform retrieved SSA errors will be large.

Proteus has stabilized platform.

Will have abs from flux divergence, abs from CRD, from Photoacoustic,
and more.. This is a first-ever.

**4.10 CIRPAS aerosol measurements (Jonsson)**

Some particle probe issues...

PCASP: wide angle scatter

FSSP-100: forwd angle scatter

APS, aerodynamic diameter rather than scattering diameter, cut at about
10 micrometers.

CAPS: forward scatter prove, back scatter probe, occultation., multiple
channel boundaries

If refractive index is unknown, uncertainties in CAPS probe calibration
is large

Practically impossible to derive particle size dist. from backscatter
probe unless refr ind is known.

Not as bad for forward probe.

Typically run dry, heaters used if necessary

PCASP/FFSP:

FFSP similar probe to forward of CAPS but with adjustable range of
particle size, usually prior to flight but potentially even during
flight. Particularly important for combined cloud and aerosol study.

If used in connection with size-distribution measurement, indices may be
inferred.

Sometimes, comparison between forward and backward CAS probes
(especially in volume) may help indicate index of refraction.

This is all based on spherical assumptions. Unfortunately, (especially
for backscatter) all bets are off when shape becomes an issue (such as
large, dust-like particles).

**4.11 CCN on aircraft (Rissman)**

Aircraft: 3 columns, 3 super saturation levels

Ground level instrument, just one super-saturation.

Based on instrument used in crystal face, fewer adjustable columns

During Crystal Face, tracked pretty well with CPC except for some
notable structure missed, Interstate HWY?

Desired to have at SGP near Hudson.

**4.12 Univ. of Washington (Covert???)**

**4.13 Aerosol chemistry (Schwartz)**

**4.14 Update on possible Proteus aircraft depolyment (Ferrare)**

Not really much solid info, lingering serious budget considerations.

Cress will pursue what would be required to move the platform from one
aircraft to another.

Generally pessimistic about this possibility...

**4.15 Others??**

**5. Refreshment Break (10:00)**

**6. Aircraft logistics (Jonsson, others) (10:15)**

a.  **aircraft layout, performance, capabilities, restrictions, etc.**

**b. Standard operational procedures**

**g. aircraft inlet(s)**

Schematic of CIRPAS...

Much nose-mounted, radome, temp, dewpoint, Vaisala system as backup.
Pito tube for dynamic pressure. Liquid water probe from Graham Stevens,

Right wing: PCASP FSSP CAPS, also another Pito tube, used with
nose-mount for differential

Left wing: MOUDI, APS

Cabin: DAQ, two (or three) PC, 1 dedicated for AQ, second for display
and air to buffered real time ground data transfer showing essentially
same display as that on aircraft along with a IRC. Voice-fon is tricky,
loud ambient noise levels.

Down-looking hatch with replaceable plates, Pilewski

Upward looking hatch for sun photometer, Schmid

APS, with scalper to protect from water (in cloud), upside down in rack,
mounted in exo-pod

MOUDI also in pod, inlets characterized to 10 micron cutoff, filter
prep, long legs (30 min)

Integration done locally (not at SGP) in March prior to IOP, with full
payload, power-up. Then test fly with max alt, max speed, etc to
shake-out issues

Jonsson to be flight scientist, Schmid in reserve

Recommendation regarding operation of PCs. Hard disks rated for 10K' due
to riding on air cushion. Sometimes HD crash increases with vibration
and altitude. Most reliable with platter parallel to g.

DOE aircraft safety review has been conducted, so far no problems.

Prior to launch, 1hr (flexible) hands-off period.

Prior to hands-off, several hour hand-on period for PI access.

Power for aircraft, transformer (with special connectors) from local
airport grid.

Shift from transformer to aircraft generator usually smooth process.

**c. Ponca City operations**

Ponca Airport visit TBD for variety of logistics details.

**d. Safety and coordination with Vance and FAA**

January meeting with Cress, DOE safety committee (flight plans)

Meeting of FAA, Vance, Twin-Otter representative (pilot) too. Airspace
coordination, Cress.

**e. flight plans**

Ferrare detailed some already discussed details re: flight coordination
with IAP, twin otter.

Night flights cancelled, GSFC lidar not coming.

Twin otter as low as 300' when not coordinating with IAP, clear air
flights

Schmid: Coordination with Proteus? Cress: No problem since Proteus will
not fly at same altitudes.

Bigger issue: Ponca City Airport logistics if Proteus comes. ARESE
experience suggests doable.

2-3 wing-tip comparisons between IAP and twin-otter.

Division of flight hours: 2/3 for direct aerosol issues, 1/3 for
indirect effect.

Free of Vance airspace below 7000'

IAP pattern: 1.5, 2, 3, 4, 5, 6, 8, 10, 12 K', 5 min leg for lower, 10
min leg for hi-est 4. Either increase leg duration or reduce legs for
purposes of instrument acquisition on the twin-otter (during matched
legs)

Instead of ramped coordinated flight, staggered helps for flight
coordination.

Cress is concerned whether this can be done in the restricted airspace
that will likely be permitted by Vance.

Cress recommends modeling approach after ARESE flight plans (web
accessible). In particular, detail several (short) flight plans that
could be inter-combined according to the details of the given day.

FAA is only an issue from 25K-40K'. Vance MOA is M-F, rarely on
weekends.

**f. integration times for sensitivity to low aerosol amounts (Arnott)**

Varied discussion of leg durations and instruments most impacted by
shorter legs including MOUDI. Tenor of discussion suggests that
composition results will be stressed by short legs. Possibly have to use
surface values. Schwartz suggests lidar results even in nominally
well-mixed layers show structure, but that may be humidity not
composition. Some issues involved to avoid own exhaust/contrail.
Schmidt: Spirals good for rapid altitude changes but for our purposes
not good for radiometers. Rapid spirals aren't good for in-situ
measurements. Preferred is rapid ascent followed by slant descents with
level legs.

Arnot instrument (with 10+ minute legs) are also impacted. Straight and
level not absolutely necessary but clearly same atmosphere is desired.

Graham Feingold:

One aircraft approach:

Fly beneath clouds to measure pdf of w \[SSA\] and n(a), non-convective
boundary layer strato-cumulous, broken,

Then fly in clouds to measure PDF of w, N_d, r_e, n®

Look at N_d = f(n(a),w,T,P)

Verification of remotely sensed measure of IE

-   fly daisy or racetrack over CF

-   3-4 overpasses of CF velow cbh (\<300m)

-   8-10 over CF in upper 1/3 of cloud for r_e, tau_d, rho

> CF provides context of LWP, r_e, alpha

Feingold to Cress: please provide layman's description of flight regs
(altitudes, time of day, ...)

Cress: go ahead and plan "reasonable flight profiles" and let the FAA
folks adjust/discuss.

Ferrare to group, esp PI on aircraft: send desired flight plans,
experiments

Schwartz to Feingold: put it in feet for FAA.

' to Ferrare: Denote a recipient to help coalesce flight plans?

"Modest" variations from proposed flight plans can be accommodated.

**h. others?**

**7. Working Lunch (Box lunches provided) (12:00)**

Cress, IOP planning flow diagram, Questionnaire is important

**d. SGP logistics (Liljegren)**

Liljegren

> SGP Facilities to support guest instruments
>
> Central Facility, 3 Instrument Development Pads (IDP), 3-phase,
> 1-phase, and 50 Hz available
>
> Guest Instrument Facility
>
> Visits to the SGP require a site visit request be filled out IN
> ADVANCE.
>
> Non-citizens should allow at least 2 weeks for clearance.
>
> Visits by citizens of sensitive countries are difficult to arrange.
>
> Computer network access from within the SGP facility is possible but
> must be specifically requested and arranged. Access to SGP computers
> (for data delivery and use) from outside is restricted. User must
> request that an account be created. The account is only accessible via
> "secure means", that is through SSH encrypted protocols such as ssh,
> sftp, scp, etcetera.

**8. Surface logistics (12:30)**

**a. AOS and guest trailer (Sheridan)**

Showed aerosol stack used in Bondeville as an example of what can be
done. This would need to have a design review by SGP/ANL personnel.

Cress to Sheridan: please submit a cost estimate ASAP

Supplements to normal AOS measurements:

> Photoacoustic abs at 532nm
>
> 3 lambda extinction
>
> filter sampler for aero TC, OC, BC
>
> CCN
>
> PILS
>
> ultrafine size dist
>
> Aerodyne mass spec
>
> size segregated aerosol composition

These changes will require BCRs to existing system as well as space for
another pump facility and housing.

Add stack and equipment either to GIF or to U-Van.

> GIF -- lots of room, but stack has negative impact on radiative
> platform
>
> U-Van, less room but no implications on existing facilities.
>
> Flynn will contact Sheridan with dimensions and specs of surplus TWP
> racks.

b.  **Aerosol - Chemistry (Schwartz)**

> No one is ready to commit, but neither are they ready to bow out...

c.  **Absorption intercomparison (Sheridan, others)**

> This seems like a good idea but will take time/effort.

-   aerosol generation facility capable of mixing white and black
    aerosol

-   perhaps not as complex as that designed for Reno experiment.

> Ferrare: budget is a constraint, how important is it. Integration of
> equipment with aircraft is always a concern. The intercomparison would
> in principle involve some instruments already integrated on aircraft.
> Perhaps by moving only the PSAP on the twin otter (using it as a
> transfer standard) would be good. However, it is very forward on the
> aircraft and is tied to a nephelometer. On the other hand, the PSAP on
> the IAP is more accessible and could be used in the proposed manner.
> Some details feeding the mixture to a stationary inlet remain.
> Portions of this suggestion have been tried before. Another concern is
> the impact on flight times/schedules. The aircraft won't be available
> in advance. Possibly this can be done during "down days" but the
> varied science goals may reduce the window of opportunity. Strawa: how
> different is this than the comparisons during flight? Arnot: pressure
> responses of instruments is open question during flight. Sheridan: not
> a huge job to get aerosol source ready but not trivial. Not too many
> "Pat"s available. Personal resources need to be considered. Strawa:
> are there inlet sampling issues? ... diverse discussions ...
>
> Ferrare: Two Pat's, Tony, whomever, get together to discuss this, set
> up scenarios, cost, time frame, say end of January.

**e. Others?**

**9. Refreshment Break (2:00)**

**10. Experiment logistics (2:15) (Ferrare, Schmid, Sheridan, others?)**

Schmid: Ponca City Airport details/logistics

Who will be at the airport?

Ogren/Sheridan: 1 person alternating tween CART and airport, no space
required

Schmid: always at least 2 people in the field

Bucholtz, he will cover entire IOP himself

Strawa: Always 2 people in the field

Feingold: Himselft for about two weeks. Hopefully Steve Ghan will cover
the rest

Arnot: Two people for entire IOP.

Cress: Desktop (office space) for just a few people. Briefing room space
for larger group (30-40 people). Lab space for working on instruments.

Aircraft data link to briefing room or to desktop room? Sat phone will
need a dedicate phone while flying. Also good for pilot and crew to have
a dedicated phone line for planning. Contract to be written once we
define our requirements. What kind of network facilities would be
available and how would they be setup, administered, etc. Can ARM
support this? Essentially, a private network hub (wireless, wired?) with
reserved (internal only) subnet along with a firewall/router to the
outside world. Will people mainly want this for data exchange locally or
for transfer and/or collection externally?

**Site visit/aircraft coordination meeting**

Briefing meetings, flight planning, and so on.

Morning briefing at 8:00 AM Ponca Airport to make go / no-go decision.

Post-flight debriefing immediately following flight.

Also, evening 8:30 PM or later for next-day planning.

Flight planning with Terra and/or Aqua? Both overpass times appear to
fit in a mid-morning flight plan.

Aerosol WG meeting at STM along with IOP discussions. Like on Monday
morning... Other WG meetings on Monday afternoon

**Weather Forecasting:**

Don Bond: SST can provide forecasting support. Ferrare: would they be
willing to provide this support locally? Bond: How often, 24/7? Ferrare:
Yes. Bond: Willing, will check with SST for authority.

SGP (Teske) has subsciption service that supplies some customizable
forecasting capability.

Key forecasting ability would be to flag clear sky possibilities. Precip
is a bad weather type.

**Data policy:**

ARM US GCR Policy says "data should be available as soon as is
reasonably possible". ARM has interpreted this as 6 months. Strawa: kind
of tight; preliminary ASAP, final 6 mnths pretty tight. Some concern
raised over access to IOP data by non-PIs.

**11. Final words of (ARM IOP) wisdom (3:30) (Cress)**

One of the more complex IOPs at site considering both aircraft and
ground-based.

> Setting up network, Guy Wilcox
>
> Coordinating two aircraft in Vance airspace
>
> Rich Ferrare doing a great job leading this.
>
> Beat Schmid really pulling facility requirements together well
>
> Note to all: don't let ambiguities slip by. Force infrastructure to
> clarify details, it will pay off in helping to achieve the science
> goals.

**12. Summary of action items (3:45) (Ferrare)**

Guy Wilcox: networking considerations at hanger.

Discuss time for leg, mission plans: PIs to send plans to Rich by
January 7-8. Rich will collect and post on BNL website.

PIs get info to Beat Schmid regarding who will be at airport.

Beat to collect facilities requirement according to participants above.

Splitter in second air-supply stack to match AOS.

Pat's get together for intercomparison of PSAP issues.

Weather forecasting, support by SST, Teske

Floor plan of U-Van to determine if it can house the aerosol
instruments.

Flynn: get rack dims and specs to Sheridan

Pat Sheridan, 2 BCRs, one for stack, one for mods to AOS