Assessing the impact of observations on ocean forecasts and reanalyses: Part 1, Global studies

Abstract

h GODAE OceanView Observing System Evaluation Task TeamUnder GODAE OceanView the operational ocean modelling community has developed a suite of global ocean forecast, reanalysis and analysis systems. Each system has a critical dependence on ocean observations -routinely assimilating observations of in-situ temperature and salinity, and satellite sea-level anomaly and sea surface temperature. This paper demonstrates the value and impact of ocean observations to three global eddy-permitting forecast systems, one global eddy-permitting model-independent analysis system, one eddy-resolving reanalysis system, and two seasonal prediction systems. All systems have been used to assess the impact of Argo profiles, including scenarios with no Argo data, and a degraded Argo array -unanimously concluding that Argo is a critical data set -the most critical for seasonal prediction, and as critical as satellite altimetry for eddy-permitting applications. Most systems show that TAO data are as important as Argo in the tropical Pacific, and that XBT data have an impact that is comparable to other data types in the vicinity of XBT transects. It is clear that no currently available data type is redundant. On the contrary, the components of the global ocean observing system complement each other remarkably well, providing sufficient information to monitor and forecast the global ocean.

Assessing the impact of multiple altimeter missions and Argo in a global eddy-permitting data assimilation system

“…This was also found in OSEs conducted with different real-time forecasting systems (e.g. Lea et al, 2014;Oke et al, 2015), where the first altimeter contributes the most to the sea level error reduction. Forecasts of sea level and ocean currents continue to be improved when moving from one altimeter to two altimeters with a relative error reduction of almost 30 %.…”

“…OSEs carried out in the context of the GODAE OceanView international programme (Bell et al, 2015) have demonstrated the impact of assimilating several altimeters and Argo (e.g. Lea et al, 2014;Oke et al, 2015;Turpin et al, 2016). They show, in particular, that the addition of the first altimeter has the largest impact but that there are quantitative improvements seen by the addition of a second and third altimeter.…”

An introduction to GODAE OceanView

“…The aim of the OSE-TT is to produce coordinated and timely assessments of the impact of observing systems on the GOV forecasting systems and to communicate the results so that they are used to inform the maintenance and adaptation of the observing system. Very good progress has been made in this direction using global (Oke et al 2015a) and regional (Oke et al 2015b) prediction systems in the last five years and there is great potential for further progress.…”

A Review of Ocean/Sea Subsurface Water Temperature Studies from Remote Sensing and Non-Remote Sensing Methods

“…Information about SST is required by scientific, commercial, and social interest activities [69], such as weather forecasting, air-sea interaction modeling, climate change studies, fisheries, and coastal zone management [44]. Figure 6 shows the monthly diurnal Sea Surface Temperature (dSST) from Karagali et al [44] as the mean hourly difference from the night-time reference SST from March to August.…”