1. Overview of ATom mission objectives
ATom 1st Science Team Meeting
22-24 Jul 2015
Overview of ATom mission objectives
Steve Wofsy, PI
Michel Prather, Deputy PI
ATom Mission Objectives
[Project Implementation Plan – due soon, affects all of us]
Level 1 Threshold & Baseline Requirements
Generic Flight Cycle (Paul Newman)
Data Management Plan (Tom Ryerson)

2. ATom Mission Objectives – What is really new here?
ATom 1st Science Team Meeting
22-24 Jul 2015
ATom Mission Objectives
– What is really new here?
ATom will calculate the chemical evolution of the air parcels it measures; this includes rates for gases (O3, CH4) as well as aerosols (BC, sulfate, SOA)
ATom will build a chemical climatology of tropospheric constituents and reactivity that can be used to evaluate chemistry-climate models and assess human influence on the remote troposphere.
ATom will build a chemical climatology with the resolution and range of species and conditions necessary for satellite algorithms.

3. Atmospheric TOMography experiment
Tier 1 Science Questions for ATOM:
What are chemical processes that control the short-lived climate forcing agents CH4 and O3 in the atmosphere?
How is the chemical reactivity of the atmosphere affected by anthropogenic emissions on the global scale?
How can we improve chemistry-climate simulations of these processes?

4. ATom Tier 1 Science Objectives
• Acquire global scale tomographic data for reactive gases and aerosols, focusing on the remote troposphere over the major ocean basins.
• Determine the rates and frequency of occurrence of the chemical processes that control short-lived climate forcing agents CH4, O3, and black carbon in the atmosphere.
• Evaluate the impacts of pollutants from industrialized and emerging economies on global chemistry and composition.
• Improve Chemistry-Climate Model (CCM) simulations of the wide range of conditions in the present atmosphere.
•Place this chemistry in a global change and climate context

5. ATom Tier 2 Science Questions
Tier 2a: Aerosols
What are the distributions in remote areas of BC and other aerosols important as short-lived climate forcers?
What are the sources of new particles, and new material for current aerosols, in the remote troposphere? How rapidly do particles evolve (e.g., into CCN), and how well is this evolution of aerosols represented in CCMs?
Tier 2b: Greenhouse Gases & Ozone Depleting Substances
What are the vertical and horizontal gradients of GHGs and ODSs over remote ocean regions?
How can we use observed gradients to help identify influences on photochemical reactivity in air parcels, validate satellite data, and help refine knowledge of sources and sinks?

6. ATom Tier 2 Science Objectives
• Aerosols: measure distributions, composition, and growth; analyze sources, transformations and removal.
• Greenhouse gases: measure distributions, analyze to determine sources, sinks, and validate satellites.
• ODSs: measure distributions, analyze sources, budgets

7. ATom satellite & CCM validation objectives
ATom measurements are closely linked to satellites that measure atmospheric chemical composition and to global chemistry-climate models (CCMs)
ATom provides unique validation and calibration data for OCO-2, GOME-2, TROPOMI, GOSAT, and satellites in the Geostationary Monitoring Constellation.
ATom uses satellite data to extend its airborne in situ observations to global scale.
ATom directly engages CCM groups and delivers a single, large-scale, contiguous in situ data set for model evaluation and model improvement.

8. Atmospheric TOMography experiment
What is new since the proposal?
Although there are no new funds, ATom has encouraged the enhancement of the ATom science objectives. As a result, we have augmented the originally proposed mission for ATom-1 with enhanced WAS sampling and 3 new instruments:
WAS (Blake) – increased number of flasks will be taken in flight (analysis money still being sought)
PFP (Montzka) – independent flask sampling, increases the frequency of whole air data stream (Tier 1, 2b)
PALMS (Froyd) – new characterization of aerosols, including dust and origins (Tier 2a, 1).
AO2/MEDUSA (Stephens) – in situ O2/N2/CO2, O/C isotopes with flasks (Tier 2b, new science on air-sea fluxes)

9. Atmospheric TOMography experiment
ATom motivation and approach:
What is out there?
What are we looking for?

10. There is a lot of structure and variability in key species:
snapshots on the 720 hPa surface
NOx H2O2
Figure Global NOx (ppt, precursor for NO radical) and H2O2 (ppt, precursor for OH radical) on the 720 hPa surface (1°x1° UCI CTM simulation at 1200Z 16 Jan 2005, Holmes et al., 2013). Note the extensive rivers of high photochemical activity in the mid-troposphere, where precursors vary by a factor of ten, and the absence of a diurnal cycle in precursors (the sun is over the dateline).

11. Even in terms of columns, there are rivers of water
and rivers of CH4 loss (OH)

12. Chemistry models cannot agree on how much HCHO is out there.
VOCs + OH
 HCHO, HCOCH3, glyoxyl, …
 regenerate HOx
 more loss of CH4, O3

14. A Tomographic slice down the dateline shows large (daily)
A Tomographic slice down the dateline shows large (daily) variability in P/L-O3, L-CH4
When averaged over lat.-height bins, the slice is representative of the Pacific basin within ~15%

15. HIPPO CH4 in isentropic coordinates:
stratification and influence regions

16. Do we need this also? – explain what is important in headline

17. ATom sampling of different model realizations of new particle formation rates.

20. Current plan

21. Proposed deployment – Current ATom-1 discussed later
Instrument
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22. Proposed DC-8 layout – Current DC-8 discussed later
update this from Adam Webster
Added: more WAS flasks, added sensors
PALMS (particle composition);
PFP (ODS flasks - tbd);
MEDUSA/AO2

23. ATom Confirmation Review requires
Level 1 Science Objectives (!now)
and
(Science Traceability Matrix)
. . .

24. Level 1 Threshold & Baseline Requirements
ATom 1st Science Team Meeting
22-24 Jul 2015
Level 1 Threshold & Baseline Requirements
These requirements are critical elements in HQ Confirmation Review and part of Project Implementation Plan. These are minimum success goals and do NOT constrain our science.
You should worry about them only if you think there is a chance that we could not meet these minimum goals.
Threshold = bare minimum to declare ATom was worth the money
Baseline = core mission declared ‘accomplished’

25. Level 1 Threshold & Baseline Requirements
ATom Goals and Objectives
The Tier 1 objective for ATom is founded on delivering atmospheric measurements and related chemical rate computations for a statistical ensemble of air parcels widely distributed over the globe. ATom measures the chemical species required to compute the chemical reactivity of the atmosphere: <P-Ox>, <L-Ox>, <L-CH4>, where <P> and <L> denote 24-hour average production and loss rates for ozone (Ox) and methane (CH4). The goal is to define these controlling chemical rates in the vast remote regions of the atmosphere, and to quantify the diffuse effects of global anthropogenic emissions.

26. Level 1 Threshold & Baseline Requirements
(continued)
The sampling strategy is therefore global, and the observations and computations provide a measure of the contrast between the Northern and Southern Hemispheres in multiple seasons, and between Pacific and Atlantic Ocean basins, over a wide range latitudes.

27. Level 1 Threshold & Baseline Requirements (draft document distributed)
ATom 1st Science Team Meeting
22-24 Jul 2015
Level 1 Threshold & Baseline Requirements (draft document distributed)
ATom Scientific Design
ATom’s direct, point-to-point flight plans include frequent vertical profiles that provide sampling of air parcels as unbiased as possible with respect to prior human influence or meteorological regime. Sampling takes place from the lowest accessible altitudes (0.15 km over the ocean, 0.5 km over land) to ATom’s flight ceiling of ~12 km. Restrictions imposed by air traffic control and by weather (visibility, icing, storms) may limit the sampling to 0.5 to 8 km altitude over portions of the ocean basins.
The core measurements in ATom include the necessary precursors to initiate 24-hour chemical model integrations to compute, from the observations, the chemical production (P) and loss (L) rates in the Tier I objectives. The required species to constrain P and L are: O3, H2O, NOx (=NO+NO2), PAN, HNO4 and HNO3, HCHO, H2O2, CO, CH4, plus diagnostic tracers of transport (CO2, SF6, or other long-lived species). In addition ATom core data may include other volatile organic compounds (VOCs) and aerosol surface area where abundances are high enough to impact overall reactivity, for example, in polluted air masses encountered over the sea. “Air Parcels” used in this computation are defined at 10 – 30 second sampling intervals (approximately 2 – 8 km in the horizontal and 300 – 1000 m in the vertical). For those measurements made at slower rates, binning, smoothing, and covariance analysis are used to interpolate species information to shorter intervals as required for each computation. The air parcel measurement and computational data are grouped into statistically robust ensembles by aggregating over altitude and latitude domains.

28. Level 1 Threshold & Baseline Requirements
ATom 1st Science Team Meeting
22-24 Jul 2015
Level 1 Threshold & Baseline Requirements
ATom Level 1 Requirements
Our Level 1 Threshold and Baseline requirements for ATom core measurements specify a 30-second averaging period (spanning ~8 km along the flight track) resulting in the measurement of more than 7,000 independent air parcels per 10-hour flight. Air parcels pass the Level 1 requirement if all the species listed above are either measured directly or filled with observed correlation patterns, providing initial conditions for (at least) one chemical model to integrate the 3 key reactivity rates over the daily period. The outputs from these constrained model computations, combined with the underlying measurements, represent the deliverables against which the Level 1 requirements are to be measured. The statistical distributions of reactivity versus the key initiating species are accumulated into ensembles over latitude-height domains and compared with results from global chemistry models.

29. Level 1 Threshold & Baseline Requirements
ATom 1st Science Team Meeting
22-24 Jul 2015
Level 1 Threshold & Baseline Requirements
The Level 1 Baseline Mission requirements are defined to achieve the full Tier 1 science objectives:
Statistically robust distributions of the core measurements defined above, plus the associated along-track reactivity computations, from 0.3 to 8 km. The Level 1 minimum spatial resolution for ensembles of core measurements is 2.5 km in altitude and 15 degrees in latitude, from 0.5 to 8 km altitude, spanning 65 S to 85 N latitude in the Pacific Ocean basin, and portions of the Atlantic Ocean basin. The Baseline Mission is achieved when these data ensembles have been obtained over three deployments that include one summer and one winter season.
The Level 1 Threshold Mission requirements are defined as the set necessary to achieve the minimum science return acceptable for the investment:
Statistically robust distributions of the core measurements defined above, plus the associated along-track reactivity computations, from 0.5 to 8 km, combined into statistical ensembles at 3.5 km height intervals and 20 degrees of latitude, spanning 45 S to 45 N latitude in two deployments.