The Tropical Pacific Observing System 2020 Project in NOAA

William S. Kessler
NOAA/Pacific Marine Environmental Laboratory
3pm June 16 in Room 2155

Spurred by the crisis of TAO in 2012-14, NOAA and partners are rethinking the Tropical Pacific Observing System through an international project, TPOS 2020, that will take advantage of new technology and reflect current scientific issues. ENSO remains a key driver for the TPOS, but subseasonal phenomena are also important. We will live with a redesign for decades, so are framing requirements carefully. Our first customers are the operational centers, and we consider the role of in situ sampling in the entire system: Observations => Analyses => Forecasts. Recognizing that current generation assimilation/forecast systems do not make effective-enough use of observations, we will target sampling where these systems need guidance for initialization, validation, and model improvement. Shaping these targets is a principal reason for this discussion, and a set of questions below gives some of the issues where EMC/CPC could help us set direction. A brief talk will describe the organization and process of the TPOS 2020 project, followed by discussion of the issues raised below.
     1) We've heard from CPC and other centers that TAO buoy humidity sampling and ability to estimate evaporation and latent heat fluxes from the buoys is valuable, especially for subseasonal forecasts and analyses. How is this information used? How does it complement satellite moisture soundings?
     2) What other surface met sampling would be useful? (e.g. BP, SW/LW radiation, precip, ...)
     3) Another set of questions concerns the geographical shape of the sampling. Is the present TAO grid appropriate? Any changes to suggest? (examples might be to contract TAO to denser spacing near the equator, or on the other hand to extend a few lines across the ITCZ or SPCZ). Would a few highly-instrumented sites (e.g. for direct surface flux measurements) be useful? Where should those be? How would they be used? (for realtime assimilation or delayed-mode validation?)
     4) What about the near-surface ocean? We now have the capability to make profiles of T,S,velocity at much higher resolution than present TAO for the upper 50m, thus to resolve the diurnal warm layer, its formation and nighttime dissipation. Is this a valuable target?
     5) TAO now makes delayed-mode velocity profiles at 4 sites along the equator. CPC said those were important as independent validation. Agree? If we measured velocity at more sites, would that be useful? For example, we are considering adding velocity sampling for two additional targets: the ocean mixed layer everywhere (could be realtime), and delayed-mode full-depth profiles at near-equatorial sites which would describe the meridional structure of the EUC and velocity gradients.
     6) How do you see the combination of TAO and Argo being used? One strawman idea would refocus TAO:
(a) towards the near-surface (where Argo is less useful because its sampling is so slow), and
(b) away from the thermocline and subthermocline (where Argo gives salinity and better vertical resolution)? Would a rearrangement like this make sense for your work?
     7) Since whatever system we design will be in place for decades, we need to think ahead to what future models/forecasts will need. Looking back from 2030, what will we wish we had started measuring in 2016? What observations would guide model improvement?