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Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system - PubMed

  • ️Fri Jan 01 2016

Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system

Samantha A Siedlecki et al. Sci Rep. 2016.

Abstract

Resource managers at the state, federal, and tribal levels make decisions on a weekly to quarterly basis, and fishers operate on a similar timeframe. To determine the potential of a support tool for these efforts, a seasonal forecast system is experimented with here. JISAO's Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE) features dynamical downscaling of regional ocean conditions in Washington and Oregon waters using a combination of a high-resolution regional model with biogeochemistry and forecasts from NOAA's Climate Forecast System (CFS). Model performance and predictability were examined for sea surface temperature (SST), bottom temperature, bottom oxygen, pH, and aragonite saturation state through model hindcasts, reforecast, and forecast comparisons with observations. Results indicate J-SCOPE forecasts have measurable skill on seasonal timescales. Experiments suggest that seasonal forecasting of ocean conditions important for fisheries is possible with the right combination of components. Those components include regional predictability on seasonal timescales of the physical environment from a large-scale model, a high-resolution regional model with biogeochemistry that simulates seasonal conditions in hindcasts, a relationship with local stakeholders, and a real-time observational network. Multiple efforts and approaches in different regions would advance knowledge to provide additional tools to fishers and other stakeholders.

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Figures

Figure 1
Figure 1. Forecast and hindcast simulated anomalies of the J-SCOPE forecast system averaged over the upwelling season (April–September) from 2013.

The hindcast anomaly is on top, the January initialized forecast anomaly in the middle, and the April initialized forecast anomaly on the bottom. Each column displays a different model field. The first column shows bottom oxygen (ml/l), the second, surface chlorophyll, the third is SST, and the last column is bottom pH. Below the maps, a time series of the 8-day upwelling index (calculated following methods from Austin and Barth 2002) is plotted from the hindcast (black), the January initialized forecast (blue) and the April initialized forecast (green). The vertical dotted lines on the time series bracket the upwelling season over which the maps are averaged. Figure generated using Matlab version 2015b (

http://www.mathworks.com/products/new_products/latest_features.html

) and Adobe Illustrator CS5 (

http://www.adobe.com/products/illustrator.html

).

Figure 2
Figure 2. Comparisons for CFS forecasts from 1997 to 2009 and the hindcasts from that same period.

Mean fields and skill metrics for sea surface temperature (SST, °C), density at 40 meters (σ 40m, kg/m3), north/south winds at the sea surface (Vwind, N/m2), and downward shortwave radiation at the sea surface (SW, W/m2). Boxed region indicates the J-SCOPE domain. Shown from left to right are: 1) mean July forecast (initialized from previous January); 2) mean July reanalysis; 3) “forecast skill” (correlation between July reanalysis and July forecast); 4) “skill over persistence” (forecast skill minus correlation between January reanalysis and July reanalysis); 5) “tendency forecast skill” (correlation of the change from January to July with predicted tendency over that period). The first two columns use the same colorbar (on the first column). The latter three columns use the colorbar in the 3rd column. Figure generated using Ferret version 6.93 (

http://www.ferret.noaa.gov/Ferret/

) and Adobe Illustrator CS5 (

http://www.adobe.com/products/illustrator.html

).

Figure 3
Figure 3

Forecasted and reanalysis product of the (a) 15-day averaged shortwave radiation forcing (W/m2) for the study region and (b) the 8-day wind stress for the J-SCOPE forecast system from CFS for 2013. For the shortwave radiation (a), the reanalysis product is in black while the forecasts from January and April are in blue and green, respectively. The CFS model is known to be biased high. For the winds (b), the observations are in black, the reanalysis from CFS-R is in blue, the April and January initialized forecasts are in red and green, respectively. The CFS model forecasts miss the duration of the upwelling seasons, as well as the relaxations/reversals in the winds over the upwelling season.

Figure 4
Figure 4. Time series of the observational climatology (red) from the OCNMS mooring location, CE015, off the Washington shelf in 15 m of water.

The model climatology (black) is the average of the 2009–2014 hindcasts. The time series have been smoothed with a 30-day filter. The standard deviation around each climatology is shaded in the background. (a) SST, (b) bottom temperature, and (c) bottom oxygen (mg/l). Statistics summarized in Table 1.

Figure 5
Figure 5. Time series of the climatology from the OCNMS mooring location, CE042, off the Washington shelf in 42 m of water.

The climatology uses the 2009–2014 hindcasts averaged together as a reference climatological field. The time series have been smoothed with a 30-day filter. The standard deviation around each climatology is shaded in the background. (a) SST, (b) bottom temperature, and (c) bottom oxygen (mg/l). Statistics summarized in Table 1.

Figure 6
Figure 6. A comparison of model and observational climatologies from three locations (inner, mid, and outer shelf) along the Newport Line on the Oregon shelf.

The model climatology (black) is the average of the 2009–2014 hindcasts, at each location and depth. The observational climatology (red) is based on twice-monthly samples. wThe standard deviation around each climatology is shaded in the background. Temperature and oxygen (ml/l) profiles are shown from spring (April-June) and summer (July–September). Fall and winter appear in the Supplemental Information. Statistics summarized in Table 1. In addition, time series from a mooring at the NH10 site (red, 2009–2014) and hindcast climatology (black) are provided in the bottom two panels: SST (2 m, top) and BT (70 m, bottom).

Figure 7
Figure 7. Time series of the anomalies from the OCNMS mooring location, CE015, off the Washington shelf in 15 m of water.

The anomalies use the 2009–2014 hindcasts averaged together as a reference climatological field, shown in Fig. 4. All anomalies are for the 2013 forecasts (January initialized is blue, April initialized is green) and hindcast (black). The time series have been smoothed with a 30-day filter. R for each forecasted anomaly is reported on the figure as well as in Table 1. (a) SST, (b) bottom temperature, and (c) bottom oxygen (ml/l).

Figure 8
Figure 8. Time series of the anomalies from the OCNMS mooring location, CE042, off the Washington shelf in 42 m of water.

The anomalies use the 2009–2014 hindcasts averaged together as a reference climatological field shown in Fig. 5. All anomalies are for the 2013 forecasts and hindcast. The time series have been smoothed with a 30-day filter. R reported on the figure as well as in Table 1. (a) SST, (b) bottom temperature, and (c) bottom oxygen (ml/l).

Figure 9
Figure 9. A comparison of forecast versus hindcast anomalies from the NH10 location (mid-shelf) along the Newport Line on the Oregon shelf.

All anomalies were calculated as the difference from a climatology based on the average of 2009–2014 hindcasts. January forecast is in blue, the April forecast in green, and the hindcast is in black. Temperature (left) and oxygen (right) profiles are shown from spring (April-June) and summer (July-September), fall (October-December) and winter (Jan-March). Statistics summarized in Table 1.

Figure 10
Figure 10. Plot of model performance comparing forecasted anomalies to hindcasted anomalies, for four forecasts and three ocean conditions.

Each map shown represents R (as in Table 1), based on six monthly anomaly maps (April, May, June, July, August, September). The comparison demonstrates skill when R > 0.5. Each panel displays a different model field (a) SST, (b) bottom temperature (°C) (c) bottom oxygen (ml/l)). The bottom maps show model fields shallower than 500 meters. All panels highlight the 200-meter isobaths as an indication of the shelf break. Figure generated using Matlab version 2015b (

http://www.mathworks.com/products/new_products/latest_features.html

) and Adobe Illustrator CS5 (

http://www.adobe.com/products/illustrator.html

).

Figure 11
Figure 11. Time series of the residuals of the forecasted and hindcasted anomalies (i.e. forecast anomaly – hindcast anomaly) from the OCNMS mooring location, CE042, off the Washington shelf in 42 m of water.

The x-axis is day of year. The anomalies use the 2009–2014 hindcasts averaged together as a reference climatological field shown in Fig. 5. All four forecasted anomalies from Table 1 are plotted here. January- initialized forecasts from 2009 (solid) and 2013 (dashed) are blue. April-initialized forecast from 2013 (solid) and 2014 (dashed) are green. The time series have been smoothed with a 30-day filter (a) SST, (b) bottom temperature, and (c) bottom oxygen (ml/l).

Figure 12
Figure 12. Maps of the percent of upper 100 m of water column that is undersaturated with respect to aragonite for the April-initialized forecast of May –August conditions (top).

The lower panel compares the observed percentage in August to the forecasted percentage. Figure generated using Matlab version 2015b (

http://www.mathworks.com/products/new_products/latest_features.html

) and Adobe Illustrator CS5 (

http://www.adobe.com/products/illustrator.html

).

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