NOAA Climate and Operational Applications from Satellite Altimetry
- (National Oceanic and Atmospheric Administration)
The planned launch of Jason-3 in 2014 will mark an important transition point for NOAA. NOAA, along with its partner EUMETSAT, will assume primary responsibility for maintaining the TOPEX/Jason reference series of altimeters and the climate data record of global sea level pioneered by NASA and CNES. To ensure the scientific and operational success of this effort, we propose a series of closely related research and development projects focusing on the main scientific goal: the study of global and regional sea level rise. Included in this work will be an extensive program of calibration/validation and operational activities. First, having shown that the global sea level budget can be closed using Jason, GRACE, and Argo measurements, we propose to move one step further and produce accurate regional sea level budgets to investigate the causes of recent regional variations in sea level rise. While altimeter and Argo observations show similar patterns of sea level and ocean heat storage trends, the causes of these phenomenon are still unknown. We will investigate whether this is the result of natural or anthropogenic climate change by studying the variability of the sea level budget. As part of this work, we plan to evaluate the regional impacts of reprocessing the GRACE fields, the periodic loss of GRACE data, and a potential gap between GRACE and GRACE-Follow-On. Second, to help interpret our present-day budget analysis in relation to past and future sea level change, we plan to investigate the effects of gyre-scale atmospheric forcing on coastal sea level. Recent studies suggest that what has previously been identified as an acceleration in global sea level in the 1920s-1930s may only reflect a re-distribution of water caused by gyre-scale forcing. We will conduct historical analyses and model simulation experiments to determine the sensitivity of regional sea level to multi-decadal changes in the atmosphere and subsequently examine the IPCC AR5 model projections for evidence of these types of signals. Third, at the core of the climate work will be an intensive effort to verify, calibrate, and improve the accuracy of observations from multiple altimeter missions. For this, we plan a suite of intercomparison studies using the Radar Altimetry Database System. We will extend the NOAA Jason Radiometer Stability Monitoring System to Jason-3 and evaluate the performance of Jason-2 and Jason-3 pitch maneuvers on the radiometer calibrations. We propose to build an operational tide gauge calibration system for system drifts, expand our calibration activities to include AltiKa and Sentinel-3, and study the use of tide gauges and the non-reference missions to bridge any potential gaps in the Jason series. Fourth, we propose to expand two National Weather Service (NWS) operational applications: high-seas wind/wave nowcasting and tropical cyclone intensity forecasting. Both of these are 'data starved' and will benefit from the addition of Cryosat-2, Altika, and Sentinel-3 data. We recently began producing near-real time CryoSat-2 wave data for the NWS and plan to extend this to the US Naval Oceanographic Office and to weather services in developing countries. We have also developed a retracked Cryosat-2 ?IGDR? which will provide an additional source for intensity forecasting efforts at the National Hurricance Center. Finally, although our primary focus is on the Jason missions, we are also deeply interested in new technologies, particularly the synthetic aperture radar (SAR) sampling technique employed on CryoSat-2, and soon also on Sentinel-3 (2013) and Jason CS (2017). This technology is expected to yield greater range precision and improved spatial resolution, but will require research to ensure that the accuracy of the derived sea level can be tied to the existing 20-year record from conventional measurements. A series of studies will be carried out, initially with CryoSat-2 data, to determine the best processing strategies.