The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Studying the impact of hourly RAMSSA_skin SSTs on the assimilation of satellite radiance data in ACCESS-R Chris Tingwell Data Assimilation Team Earth Systems Modelling program CAWCR GHRSST workshop, Melbourne March

The standard approach to diurnal variation of SST in most NWP systems is to ignore it. Generally daily SST fnd analyses are used as a proxy for SST skin and persisted through the assimilation cycle and subsequent forecast. The availability of hourly TWP+ RAMSSA_skin fields, generated by a fast DV model, presents an opportunity to test their impact on the assimilation of satellite radiances in ACCESS. Here, we’ll give an brief overview of ACCESS satellite assimilation and what we plan to do.

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology AMOS 2012 Sydney Jan 31 - Feb 3 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Australian Community Climate and Earth System Simulator A collaboration between the Bureau of Meteorology, CSIRO and universities ACCESS-NWP Earth Systems Modelling Program Leader: Kamal Puri Data Assimilation Team Leader: Peter Steinle Atmospheric Modelling Team Leader: Gary Dietachmayer Model Systems Team Leader: Martin Dix Atmosphere-Land Observation and Assessment Program Remote Sensing Team Leader: John Le Marshall Special acknowledgement to the Met Office

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology ACCESS NWP APS0 and APS1 domains G 80km 4dVAR R o 4dVAR APS0: all systems L50 A 0.11 o 4dVAR C 0.05 o no DA T 0.375º 4dVAR (boundaries not shown) TC 0.11º APS1: all systems L70 C 0.04 o no DA R o 4dVAR G 40km 4dVAR TC 0.11º APS0: domains chosen to reproduce Bureau’s previous NWP systems (which they replaced in 2010) APS1: significant rationalisation of domains + increased horizontal and vertical resolution

ACCESS-R (APS0) 37km L50 65°S to 17°N / 65°E to 184°E Met Office Unified Model (UM) Observation Processing System (OPS) SURF 4dVAR Has run continuously in Bureau since 2009, nested in ACCESS-G Operational regional NWP system since 2010

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology OBSERVATION TYPES ASSIMILATED IN ACCESS APS0Surface: synop, ship, buoy Balloons, profilers Aircraft: AIREPS, AMDARS Satellite observations Winds Scatterometer surface winds, Atmospheric Motion Vector tropospheric winds Radiances Microwave: ATOVS (AMSU A,B and MHS) Infrared: ATOVS (HIRS), AIRS APS1All of the above, plus: IASI Infrared radiances GPS-RO bending angle observations

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology 06Z 12Z 18Z00Z ACCESS-R Daily ATOVS coverage ATOVS, AIRS radiance data contribute a significant amount of forecast skill in SH and Aus region

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology ACCESS-R AIRS usage Received Accepted

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology DATA ASSIMILATION: 4dVAR time 6 hours model state observations new forecast (3 days/10 days) JoJo JoJo JoJo JoJo JoJo JbJb first guess (previous forecast) t0t0 t+3 t-3t-3 analysis Assimilation cycle repeats every 6 hours

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology BUFR DATA ASSIMILATION: Data Processing RTDB MARS ODB OPS 1dVAR QC Thinning Bias Correction Cloud Screening VAR VAROBS CX model values at obs locations Met Office ECMWF Radiance bias monitoring Updated bias predictors

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Observation Processing System OPS VAR OBS VAROBS Model background state ODB

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology J(x) = ½(x – x b ) T B -1 (x – x b ) + ½(y – H(x)) T R -1 (y – H(x)) J(δy) = -½(δy) T (H T BH + R) -1 δy + C δy = y o – y b J(δy) < J threshold δy > 0 x atmospheric state vector x b background (first guess)... includes SST field H(x)radiances generated from foward model H (RTTOV) Bbackground error covariance Robservation error covariance final x includes retrieved T skin 1d-VAR Cloud detection

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology ATOVS

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology ATOVS

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Each forecast provides hourly background fields for the next analysis cycle 06 UTC 12 UTC 18 UTC 00 UTC Daily RAMSSA SST fnd as proxy for SST skin 6h assimilation window

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Beggs, Gentemann & Steinle 2009

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Each forecast provides hourly background fields for the next analysis cycle, but the SST field is persisted for 24 hours. 06 UTC 12 UTC 18 UTC 00 UTC Daily RAMSSA SST fnd as proxy for SST skin 6h assimilation window

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology 06 UTC 12 UTC 18 UTC 00 UTC Hourly RAMSSA_skin SST skin

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology TWP+ RAMSSA_skin SST skin = RAMSSA SST fnd + ΔSST − 0.2°C ΔSST = f (insolation, u 10m, v 10m ); u 10m, v 10m from ACCESS Gentemann et al., 2003 The study period will be Jan-Apr 2010 DATASET

Plan Identify suitable cases of strong diurnal SST variation Run standalone OPS jobs with RAMSSA_skin inserted into model background inputs Examine ATOVS and AIRS radiance usage statistics compared against standard configuration Run full assimilation cycles employing RAMSSA_skin: assess resultant forecasts using standard skill metrics

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Issues RAMSSA_skin may underestimate full diurnal variation due to RAMSSA SST fnd not sampling times close to local sunrise ? Radiance bias corrections are calculated from static bias predictors generated from long runs of output statistics. Should they be regenerated here ? Or should the bias corrections be continuously updated ? How should the results be assessed ? Forecast skill only ? Can we repeat the exercise with ACCESS-R APS1 ? When ?

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Thank you

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology DATA ASSIMILATION: 4dVAR Full forecast model Perturbation Forecast (PF) model Adjoint PF model Descent algorithm Background observations y 1 y 2 y 3 y 4 final analysis linearisation states 6 hour window VAR FORECAST VAR FORECAST VAR FORECAST Assimilation and forecast cycle Obs First guess Linearisation states ESM

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology