The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Oscar Alves, Maggie Zhao, Robin Wedd, Harry Hendon, David Anderson, Yonghong Yin CAWCR, Australian Bureau of Meteorology Salinity Initialisation and Seasonal Prediction

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology 1.How well can PEODAS assimilation salinity, especially pre Argo 2.Impact of salinity on seasonal forecasts 3.Asymmetry between salinity and temperature errors 4.Conclusions Plan

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology PEODAS vs Old System OLD POAMA-OI PEODAS System Optimum Interpolation Pseudo EnKF Covariances 2D Univariate Static 3D Multi-variate Time-evolving Observations Temperature Temperature and salinity ForcingNCEP Re-analysis ERA-40 Re-analysis Bias Correction Re-analysis None 3D relaxation to Levitus 1980-present 1960-present

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology How good is PEODAS salinity pre Argo ? How does PEODAS compare with POAMA-OI ?

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Observation distribution Produced by Yonghong Yin Pre-Argo During-Argo

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Salinity Error at 156E Produced by Robin Wedd FULL_S (PEODAS) T/S Assim UPDATE_S T and S(T) NO_S T Only CONTROL No Assim

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Impact on Equatorial Salinity Mean State The CONTROL equatorial salinity mean state and the differences of each of the assimilation runs. 1: NO_S shows degradation of salinity stratification: spurious vertical mixing. 2: Saltier salinity maximum in both UPDATE_S and FULL_S runs. 3: Saltier western Pacific warm pool in all assimilation runs.

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Saltier Pacific Salinity Maximum The CONTROL average salinity to 300m mean state and the differences of each of the assimilation runs. Spurious vertical mixing in NO_S is not confined to the equator. Large saltier area north-west of the salinity maximum in UPDATE_S and FULL_S is believed to be a correction of model error. It is then advected to the equator.

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology How does salinity impact forecasts ? Impact of PEODAS vs POAMA-OI on the forecasts

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Impact of T/S differences on forecast mean state (Using same model, mean state of hindcasts over 27 years)

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology PEODAS – POAMA-OI Long term impact due to salinity differences in initial state Showed by adding T and S differences separately as perturbation to a model forecast Time longitude View

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Idealised Perturbation Experiments T Pert S Pert T/S Pert After 25 days

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Sections along the dateline Red – Sal Pert, Black – T Pert

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Easy to mess up salinity (e.g. with T only) Cross-covariances in PEODAS to a good job when there is no salinity data Salinity errors can have a long term impact on forecasts (important for multi-year forecasts ?) Temperature errors – generate Kelvin (and Rossby wave) with Temperature signal Salinity errors – generate Kelvin wave with Temperature signal But also the initial adjustment process generates local T and S errors that only decay on much longer timescales Conclusions