• Preamble
• Implementation
• US INDOEX Instruments: Priority, Description, Calibration and Performance
  

Resilient: Capable of withstanding  shock without permanent deformation
Streamlined: Contoured to reduce resistance to motion

Preamble:  INDOEX, as described in the US proposal, has three interrelated objectives dealing 
with aerosol climate forcing including the anthropogenic effects) solar absorption and ITCZ 
transport of trace species. The proposal was submitted to NSF, DOE and NASA for a total amount 
of $ 6.8M, for 2 aircraft ( NCAR WB-57 or NASA/ER-2, NCAR/C-130 ), 1 surface stations 
(Male), participation in ship cruises, modeling and data analyses and integration. The total cost of 
the program (including European and Indian components) is about $ 18 M, which includes 3 island 
stations (Mauritius, Reunion and Male), 4 aircraft (NOAA-P3 and Dutch Citation-II, in addition to 
the above 2 aircraft), 2 ships (German Die Sonne, and Indian Sagar Kanya) and new satellite 
aerosol and radiation experiments including TRMM, POLDER and EOS-AM. 

Uncertainties in the federal budget over the 3 year life time of the project, complexities in multi-
agency cost sharing and problems with high altitude aircraft have persuaded us to develop an  
implementation plan that is relatively resilient to budgetary shocks and reduces the risk of losing 
the impressive momentum behind this project. 

Implementation Plan:  The streamlined execution plan outlined below (and elaborated further 
in the attached document) has two components: I) Aerosol Component and II) The full INDOEX 
program, which includes the Component I. The attached budget sheet separates the total $ 6.8M 
budget under these two components.


(1) Aerosol Component:  The salient features of this component are listed below:

	*It can be done at about $ 4.5 to $5 M, or roughly 70% of the cost of the full program. 
This cost includes field operations, but does not include the following:
	 a) deployment costs for C-130, the integrated Sounding System from NCAR and drop 
sondes from NCAR.  We have assumed that NSF will pay for these items.
	b) About $2M for the participation of 6 C4 PIs (at SIO, NCAR, Maryland and OSU), 
1 site scientist for Male, 3 post-docs, 4 grad students, 4 undergrad students and 1 programmer for 
data integration. These will be paid by C4 from base funding to C4 from NSF.
	*It does not require ER-2 or  WB-57 or NOAA P-3. 
	*It requires NCAR C-130 and Dutch Citation-II (already approved by the Dutch Govt.).  
We are requesting 120 hours instead of the original 100 hours. See closure diagrams shown in 
Figs 1 and 2 of how the aircraft data will be combined with other correlative data to obtain the 
direct and indirect aerosol forcing.
	*All other surface and satellite platforms are as mentioned in the US proposal.
	*It has a focused new program on the indirect effects, which includes 3 new PIs, new 
CCN spectrometer (J. Hudson) and CVI (C. Twohey) measurements of the in-cloud aerosol and 
radiation properties, modeling of cloud-aerosol interactions ( M. Baker) and a three-fold increase in 
flight hours dedicated to cloud sampling (15 hours in the original proposal to 40  hours in the 
current plan ). The following new developments encouraged us to take a more aggressive approach 
on the indirect effect: 

	I) A joint French/US study  by S. Bony and W. Collins (sponsored by C4) developed a 
new technique to identify low clouds that are not obscured by high clouds from INSAT Vis/IR 
data. The study which uses 4 years of winter time INSAT data, reveals a preponderance (30 to 
40% of the time) of low-level clouds  within 3 hours of flight from Male island. The surface based 
Hahn et al reveal even larger frequencies of low-level clouds for this region. Thus, with the C-130 
(flight range of 3000 nm) and the Citation (flight range of 1300 nm) we have an excellent 
opportunities for sampling polluted low clouds using the closure approach outlined in the attached 
diagram.
	II) The delay of INDOEX by 1 year, will enable us to access high resolution aerosol and 
cloud data that will be generated by CERES, MODIS (EOS-AM) and POLDER (ADEOS). These 
will be in addition to our in-house efforts (Coakley, Collins, Desbois and Bony) at retrieving 
aerosol and cloud effective drop size from AVHRR. Thus we are quite optimistic of combining in-
situ data with satellite data to gain some understanding of the aerosol forcing effects on larger 
regional scales of relevance to climate studies.

The aerosol component has been described in the US proposal under Objective 1. Its  
implementation in the present context is described further in the attached section.

II. The full INDOEX program: The salient features of the implementation plan for the full program 
are listed below.

	*The aerosol component described above
	*An add-on of $ 2.2 M in hard funds, deployment costs for WB-57 and P-3 (NOAA has 
agreed to pay for P-3 costs as per Fahey & Tuck) to address the overall science described in the 
US proposal including objectives 2 and 3. 
	*In addition to the platform mentioned above under the Aerosol Component, it requires
a high altitude aircraft ( WB-57 or ER-2) and NOAA-P3. 
	*The following  scientific results (in addition to those mentioned under component-I) will 
be obtained from this new capability: i) New aerosol particle production in the upper troposphere in 
the cirrus outflow region; ii) A much better calibration with EOS and TRMM satellite aerosol 
optical properties and radiation fluxes, since the satellite radiances includes effects of aerosols 
above the 20000 ft (C-130) to 40000 ft (Citation-II) flight range of the component I aircraft; iii) A 
complete characterization of the ITCZ chemistry of the low troposphere (through P-3) and the 
upper troposphere (e.g. WB-57); iv) An accurate description of the column cloud radiative forcing 
at the tropopause; v) A detailed description of ITCZ-cirrus microphysics and optical properties and 
their role in modulating the radiative heating of the ocean; vi) With the latent heating  obtained from 
TRMM and the column cloud forcing obtained by INDOEX, we obtain a first-time estimate of the 
diabatic heating for the ITCZ cloud systems.

This program is listed in full in the US proposal.

Additional Aspects of the Implementation Plan:
	
	  Calibration: We will be relying on  PIs from Europe (for ship, surface and aircraft data) 
and India (for data on 3 Indian stations and ship) to gather data that will help fill important gaps. 
Comparability and compatibility of the various instruments are critical for this purpose. The key 
issue is calibration. We will adopt the following general strategy. An instrument by instrument 
description is given separately as part of this plan (available by March 18th).

	*Calibration of US radiometric instruments at the new DOE facility in ARM-Oklahoma 
site. These include broad and narrow band radiometers including the spectral radiometers used for 
aerosol optical depths. The same instruments will be on Male and the ship. The Indian, European 
and US instruments will be compared by docking the ship at Male during the field phase and 
during 1998 cruise for at least 3 days

	*The European and US aerosol and chemistry instruments will be compared by flying the 2 
aircraft (C-130 and Citation) over the same air-mass at near real time (subject to safety constraints).

	*Sailing the German and Indian ships side by side combined with aircraft overflights and 
satellite over passes.  In addition, the US instruments will be on both the Indian and German 
ships, thus facilitating comparisons.

	Open Data Sharing:  The success of the above depends on sharing data freely across 
institutional and national boundaries. We will have a data  sharing policy that is compatible with 
US government and WMO policy.  This policy is being drafted by S. Williams (UCAR) and A. 
Swathe (India) to be sent to the INDOEX International Steering Committee for approval.  In effect, 
there will be a 1 year period (immediately after gathering the data) during which the instrument PI 
has sole access to her/his data. After this 1 year period, the original data will be archived in 
CODIAC (UCAR)  and the integrated data will be on CIDS with a password, during the second 
year, that will enable all INDOEX PIs to access the data. However,  conference presentation or 
journal publication within this second year period require written permission from the instrument 
PI. After the end of the second year, the password will be removed (provided the data are certified 
by the science team) and will be placed on WWW through CIDS.

	Prioritization:  Another tool for handling unanticipated budget surprises is prioritization of 
all of the instruments. We have prepared a comprehensive table of all instruments with priorities 
ranging from 1 (must have) to 3 (highly desirable).







                      I. Aerosol Forcing Component of INDOEX

	The primary focus of this component is the characterization of the direct and indirect 
radiative forcing by anthropogenic and natural aerosols over the Indian Ocean.  It is important to 
note that, the term ³radiative forcing² denotes not only the optical properties of aerosols (such as 
optical depth, single scattering albedo and phase function) but also the changes in radiative fluxes 
(in Wm-2) due to aerosols in clear and cloudy skies.  The aerosol objective will be obtained through 
measurements made from surface-based stations, satellites, and aircraft.

	The aerosol forcing, both direct and indirect and due to both natural and anthropogenic 
aerosols, will be determined for the Indian ocean during the winter monsoon season.  The 
measurement of this forcing will be accomplished as follows:  Prior to the deployment of the 1999 
aircraft campaign, a climatological data base will be developed through a continuous program of 
ground-based measurements made at stations in India and various islands in the Indian ocean.  In 
addition, ship cruises will periodically transect the ocean.  Ground-based lidars deployed during 
the pre-INDOEX period will serve to characterize the temporal and vertical distributions of 
aerosols.  Likewise, satellite observations (AVHRR and INSAT imagery, and after the TRMM 
launch, VIRS and CERES) will be used to infer the direct effect of aerosols on reflected sunlight.  
The satellite observations will be linked to surface and shipboard measurements of aerosol optical 
depths and surface radiative fluxes collected during the 1996, 1997, and 1998 pre-INDOEX 
cruises and surface station observing periods.  AVHRR and VIRS observations will be used to 
retrieve cloud droplet effective radii and cloud optical depths for the low-level clouds in the Indian 
ocean both north and south of the ITCZ.  Links will be sought between the direct effect of the 
aerosols, low-level cloud optical depths, and droplet radii.  Thus, prior to the aircraft campaign, 
surface, ship, and satellite observations will be combined to establish a data base associated with 
the direct and indirect forcing for the Indian ocean.  

	The aircraft campaign is crucial to the accurate characterization of the aerosol forcing.  
Flights with the NCAR C-130 and Dutch Citation (model CITATION II) will be used to probe the 
vertical structure of the atmosphere and link its composition to the sources of pollution and to the 
top of the atmosphere and surface radiative forcing.  The NCAR C-130 will be used to obtain 
radiation, cloud and aerosol properties (see Table 6a of US proposal, hereafter described as USP).  
The Dutch Citation will be used to obtain concentrations of chemical tracers, and to probe cloud 
and aerosol properties ( See Table 16a, P. 62 of the USP for list of Citation instruments ).  The 
aircraft performance are compared in Table 10 (p. 33) of USP and flight hour allocation is shown 
in Table 11 (P. 3) of USP.  The range, speed and ceiling for Citation-II are respectively 1350nm, 
400 knots and 12.5 km and for C-130 these are respectively: 3000 nm, 290 knots and
8 km.

	As described in the USP there are three types of aerosol forcing flights (P. 26, P. 34 and 
Fig. 19):  1) Radiation-Aerosol Gradient/profiling flights consisting of constant level flight during 
the outbound route and top-hat style (Fig. 19c, P. 35) profiling return flight pattern.  These flights 
will yield horizontal gradient in aerosol forcing and a statistical data base for cloud and aerosol 
properties in pristine and polluted air.   2) Aerosol Direct Forcing Closure flight during which the 
radiative forcing will be linked with aerosol physics, optical and chemical properties.  3) Aerosol 
Indirect Effect Closure flights, during which low-level clouds will be profiled  for indirect effects.  
The flight hour allocation for the C-130 are as follows:

Gradient/Profiling Flights: 			 60 Hours
Aerosol Direct Forcing Closure Flights:	         20 Hours
Aerosol Indirect Forcing Closure Flights:	 40 Hours

The above numbers are approximate estimates. The actual distribution will be decided in the field 
by the aircraft scientist ( in consultation with the steering group) based on the success of each 
mission.

Missions will be selected and planned based on the analysis of real-time satellite imagery that will 
be available at the control center as described in the original INDOEX proposal.  The C-130 flights 
will begin with an outbound leg, to be flown at about 20 Kft, during which SABL, the lidar on the 
C-130, will be used to characterize the vertical structure of the aerosol and cloud layers to be 
probed during the flight.  The Citation will profile the region up to about 40 Kft for about 500 nm 
(from Male) along the flight track of C-130.  Since it carries a Mass spectrometer for SO2 (and 
other reactive species) and other instruments for CO, CO2, CH4 and NOy and O3 (see Table 16a in 
the USP), it will be invaluable for characterizing the source of the airmass influencing aerosol 
properties. In addition the DMA, OPC, CVI and FSSP instruments will characterize aerosol 
properties from the lower troposphere to about 12 km. These data will be critical (particularly in the 
absence of the WB-57) for separating the lower troposphere aerosol effects from mid troposphere 
aerosols, while correlating C-130 data with satellite aerosol optical depths.  In addition these data 
will provide the much needed redundancy in aerosol measurements in the lower troposphere.

To reach the region south of the ITCZ, about 2 of the C-130 flights will require refueling at 
Mauritius or Seychelles. For these flights, the Citation will be flown to Seychelles or Mauritius 
(ahead of time) to accompany the C-130 and profile the region south of the ITCZ

For the direct radiative forcing, flight legs below, in, and above the various distinct aerosol layers 
will be flown.  For closure flights within about 500 nm of the base of operations, the Citation and 
C-130 will be used to obtain simultaneous sampling of the lower and middle troposphere. These 
flights were referred to as closure flights in the INDOEX proposal.  The goal is to link the 
physical, chemical, and optical properties of the aerosol layers with the radiances measured by the 
surface, aircraft, and satellite radiometers.  

Likewise, for the indirect radiative forcing, flight legs below the low-level cloud layer, in the 
cloud, and above the cloud will be flown.  The goal is to link cloud droplet concentrations and 
chemical composition to the physical and chemical properties of the subcloud CCN, and in turn, to 
link the properties of the CCN to the aerosol plume.  Effects due to the mixing of air from above 
the cloud layer are to be accounted for through observations of conserved tracers by the Citation II.  
The in situ cloud observations are also used to link the cloud optical depths and droplet sizes 
derived from satellite and aircraft radiometer data to those actually found in the clouds.  At least 
two and possibly three conjunctions with satellites carrying either AVHRR or VIRS should arise 
during each research flight.  The above objectives will be met with the C-130 flying legs that probe 
the vertical structure of the atmosphere over time periods of about 2 hrs or less.  The vertical 
probes will start and finish with the C-130 above the system being probed.  Radiometric data 
collected by the C-130 before and after the vertical probe will be used to assess the evolution of the 
systems during the vertical probe.

	The INDOEX Science Team (the authors of the INDOEX proposal) would invite Drs. J. 
Hudson, M. Baker and C. Twohy to join the experiment.  Dr. Hudson would be recruited to 
measure the characteristics of CCN from the C-130 (in addition to the CCN measurements by 
Andreae, MPI-Mainz).  Dr. Baker would provide expertise in cloud physics for determining the 
indirect effect.  Dr. Twohy will participate with the CVI on the C-130 (in addition to the CVI 
measurements on the Citation by Strom, Stockholm Univ) which will be used to characterize the 
properties of cloud droplet nuclei.

Comment on Radiometric Measurements: In view of  emerging recent concerns (e.g. the recent San 
Antonio DOE-ARM meeting) about  broadband, narrowband and multi-band sun-photometer 
radiometric measurements, we will employ the following procedures. The new calibration facility 
at the DOE-ARM SGP site will be used to calibrate the instruments used in INDOEX. These 
include pyrheliometers, diffuse flux pyranometers, sun photometers, shadow band radiometers 
and Valero radiometers (these are already at the ARM site and are being compared with other 
instruments). In addition, we will contact Dr. Mike King for the use of the new calibration facility 
at Goddard.  Additionally, we will also use the NOAA-CMDL facilities at Boulder (Ellsworth 
Dutton). We will participate at the ARM-shortwave intensive observing period that is coordinated 
by Wiscombe. Lastly, all of the radiometers will be calibrated before and after an mission, be it 
from a ship, an island or aircraft.

	As highlighted in the original proposal, INDOEX offers a first-time opportunity for 
measuring the radiative forcing due to aerosols on the continental (the Indian ocean north of the 
ITCZ), monthly mean (the winter monsoon season, January-March) scales relevant to the climate 
system.  While the strategy for obtaining the aerosol forcing outlined above can be undertaken in 
any location, INDOEX offers advantages not common to other parts of the globe.  INDOEX will 
take advantage of the circulation unique to this region during the winter monsoon:  Polluted plumes 
from the Asian subcontinent blow over a largely cloud-free ocean.  The cloud-free oceans not only 
facilitate the measurement of the direct radiative forcing, but also, the stability of the atmosphere
in the region during the winter monsoon favors the development of single-layered, low-level clouds, 
which can be used to address the indirect forcing.  The contrast between the high concentrations of 
pollutants near the continent and the low concentrations near the ITCZ, only 1500 km south of the 
continent, produces a strong gradient in aerosol concentrations.  This gradient is to be used in 
INDOEX to determine the radiative forcing.  Gradients in pollutants and aerosol optical depths 
were observed during the 1995 and 1996 INDOEX cruises.  Relatively high concentrations of 
sulfates, nitrates, black carbon, and mineral dust aerosols were observed, often in conjunction with 
relatively high concentrations of O3, CO and the oxides of nitrogen.  In addition, within two 
decades, population growth and the consequent increase in energy usage is expected to greatly 
increase emission rates in Asia thereby greatly increasing the forcing due to anthropogenic aerosols 
over the Indian ocean.  As a result, the forcing derived during INDOEX will serve as a benchmark 
by which global change could be measured.  Furthermore, INDOEX provides a unique 
opportunity for scientists from developing countries to work side-by-side with scientists from 
developed nations to assess the effects of pollution on global change.