Pilot projects are a small-scale preliminary activity/study conducted in order to evaluate feasibility, cost, risks and sampling strategy ahead of a full-scale field campaign or sustained backbone implementation. They were initiated in support of the TPOS 2020 project starting in 2016 to advance the readiness of in situ observing platforms (e.g. floats, gliders, moorings) and assess their potential to address observational requirements and gaps in the tropical Pacific Ocean region. These projects were designed to develop, calibrate, and demonstrate the capability of instruments and platforms that may eventually be integrated into the sustained observing system.

• Autonomous Surface Vessels as Low-Cost TPOS Platforms for Observing the Planetary Boundary Layer and Surface Biogeochemistry

  PIs: Meghan Cronin (NOAA PMEL), Dongxiao Zhang (UW CICOES), Adrienne Sutton (NOAA PMEL), Chris Meinig (NOAA PMEL)

• China Experimental Observing Project in the Western Tropical Pacific

  PIs: Feng Zhou, Dake Chen, Fei Chai, Xiaohui Xie, Weidong Yu

• Developing an autonomous biogeochemical profiling float to monitor biological productivity, ocean-atmosphere CO2 fluxes, and hypoxia

  PIs: Sarah Purkey, Todd Martz, Lynne Talley, Dean Roemmich, Matthew Mazloff, Daniel Rudnick, Ariane Verdy (SIO-UCSD); Neil Bogue (MRV Systems LLC); Ken Johnson (MBARI)

• Development and Testing of Direct Covariance Turbulent Flux Measurements for NDBC TAO Buoys

  PIs: James Edson and Tom Farrar (WHOI), Meghan Cronin (NOAA PMEL), Chris Fairall (NOAA PSL)

• Enhanced Ocean Boundary Layer Observations on NDBC TAO Moorings

  PIs: Karen Grissom (NOAA/NWS/NDBC), William Kessler (NOAA/PMEL), Meghan Cronin (NOAA/PMEL), and Jessica Masich (NRC, NOAA/PMEL)

• Flux Surface Glider Experiment

  PIs: Iwao Ueki, Tatsuya Fukuda, Makito Yokota,Ken Ando, and Yasuhisa Ishihara (JAMSTEC)

• Improvements to Profiling Float Technology in Support of Equatorial Pacific Biogeochemical Studies

  PIs: Stephen C. Riser (University of Washington), Ken Johnson (MBARI), Brendan Carter, (JISAO/UW), Thomas Mitchell (Seabird)

• Profiling Floats Equipped with Rainfall, Wind Speed, and Biogeochemical Sensors for Use in the Tropical Pacific Observing System

  PIs: Stephen Riser (University of Washington, School of Oceanography), Jie Yang (University of Washington, Applied Physics Laboratory)

Process studies were outlined in broad terms in the First and Second Reports to guide potential study areas that are needed to resolve phenomenological questions and provide better parameterisation for models. Studies at the northern and eastern edge of the Warm Pool were kicked off during the Years of the Maritime Continent study that took place in 2017-2019. Additional pre-field modeling studies were funded in 2019 in support of Pacific Upwelling and Mixing Physics (PUMP) and Air‐sea interaction at the eastern edge of the Warm Pool. The results these studies may point to future sustained observations or refinement of the Backbone sampling.

• Air-sea interaction at the edges of the Warm pool.

  PIs: Masaki Katsumata, Akira Nagano, Kunio Yoneyama, Iwao Ueki,, Ken Ando, Meghan Cronin, and Dongxiao Zhang

• Improved Understanding of air-sea interaction processes and biases in the Tropical Western Pacific using observation sensitivity experiments and global forecast models

  PIs: Aneesh Subramanian (CU Boulder), Kris Karnauskas (CU Boulder), Charlotte DeMott (CSU Fort Collins), Matthew Mazloff (SIO, UCSD)

• Multi-Timescale Near-Surface Salinity Variability at the Eastern Edge of the Warm Pool: A Modeling and an OSSE Study in Support of TPOS 2020

  PIs: Arun Kumar (NOAA/NCEP/CPC), Avichal Mehra (NOAA/NCEP/EMC), Meghan Cronin (NOAA/PMEL), Jieshun Zhu (NOAA/NCEP/CPC & UMD/ESSIC), and Dongxiao Zhang (UW/JISAO)

• A Pre-Field Modeling Study of Scales, Variability and Processes in the Near Surface Eastern Equatorial Pacific Ocean in Support of TPOS

  PI’s: Frank Bryan (NCAR), William S. Kessler (NOAA/PMEL), LuAnne Thompson (UW)

• Simulations and analysis of mesoscale to turbulence scale process models to facilitate observational process deployments in the Equatorial Pacific Cold Tongue

  PIs: D. Whitt (NCAR; now at NASA/ARC), R.-C. Lien (UW/APL), D. Cherian (NCAR), S. Bachman (NCAR), R. Holmes (UNSW), W. Large (NCAR)

• State estimates for the tropical Pacific: a reanalysis for evaluating the model, observations, and mass, heat, and salt fluxes

  PIs: Bruce Cornuelle, Ariane Verdy (Scripps Institution of Oceanography, University of California San Diego)

• Understanding Coupled Ocean-Atmosphere Processes at the Eastern Edge of the Warm Pool in Support of TPOS 2020

  PI: Shuyi Chen, University of Washington

• Understanding Processes Controlling Near-Surface Salinity in the Tropical Ocean Using Multiscale Coupled Modeling and Analysis

  PI: Carol Anne Clayson, Woods Hole Oceanographic Institution

• Use of high resolution ocean model to assess sampling strategies for TPOS 2020 process studies

  PIs: Kelvin Richards, H. Annamalai and Yanli Jia, University of Hawaii

Note – In some cases, the target period of the pilot projects and process studies is wholly within the timeframe of TPOS 2020, while in other cases the period may go beyond 2020.