WGSIP Summary

The aim of this initiative is to evaluate the ability of the current state-of -the-art dynamical forecasting systems in representing the tropical-extratropical teleconnections. The analysis, based on observational and model data from several seasonal forecast systems, uses a common framework for a straightforward intercomparison. Tropical rainfall anomalies are used to represent the response to anomalous tropical atmospheric heat sources.

Participating members (so far): ECMWF (UK), Met Office (UK), Meteo France (France), NCEP (USA), CMC (MSC) (Canada), CMA/BCC (China), BOM (Canada)

Planned analysis:

Precipitation:

• precipitation variability relationship across the tropical regions / SST-precipitation relationship;
• the predictive skill of precipitation across the different tropical basins;

Covariance and Rossby wave source analysis:

• the predictive skill of the NAO and PNA via tropical teleconnections

Precipitation analysis is almost completed

Data: The model data is taken from CHFP and EUROSIP archive

Expected outcome:

• estimate the model accuracy in representing remote atmospheric responses originated in the tropics.
• improved and more reliable seasonal forecast predictions for the extratropical regions

REFERENCES:

Kumar et al. 2013: “Understanding prediction skill of seasonal mean precipitation over the tropics” Journal of Climate Vol. 26 p.5674-5681

Manola et al 2013: “Drivers of North Atlantic Oscillation Events”, Tellus A, 65, 1-13.

Molteni et al. 2014: “Understanding and modelling extra-tropical teleconnections with the Indo-Pacific region during the northern “. Climate Dynamics. Ref.: Ms. No. CLDY-D-14-00256R2

Scaife et al. 2016: « Tropical rainfall, rossby waves and regional winter climate predictions». QJRMSVersion of Record online: 20 OCT 2016 | DOI: 10.1002/qj.2910

The aim of this initiative is to evaluate the impact of realistic snow initialisation on skill of subseasonal-to-seasonal forecasts by state-of-the-art dynamical forecast systems. The modeling strategy follows the one developed during the GLACE2 initiative, which was aimed at assessing the impact of soil moisture on seasonal forecast (e.g. Koster et al., 2011). These forecast experiments would be relevant for the assessment of forecasting skill, for the attribution of climate pattern variability and extreme weather/climate events to snow forcing, and for subseasonal-to-seasonal predictions during the Year of Polar Prediction (YOPP).

Participating members (so far) : ECMWF (UK), BSC (Spain), NILU (Norway), Chonnam National University - UNIST (South Korea), KOPRI (South Korea), IAP (China), Gøteborg University (Sweden)

Planned experiments : multi-model seasonal (about 3-month) simulations covering at least a decade (2004 à…), with either realistic or else climatological snow conditions, and start dates throughout fall to spring.

• Completed experiments : ECMWF
• Analysis : deterministic and probabilistic forecast (skill score, reliability diagrams,…)

Data Center: to be established in Korea (KOPRI), with support of 1 person

Expected outcome:

• estimate the impact of snow on surface air temperature and circulation at subseasonal time-scale
• improved and more reliable snow prediction

REFERENCES:

Koster R.D. et al. (2011), GLACE2: the second phase of the global land atmosphere coupling experiment: soil moisture contributrion to subseasonal forecast skill. J Hydrometeorol 12:805–822.

Orsolini, Y.J., Senan, R., Balsamo, G., Doblas-Reyes, F., Vitart, D., Weisheimer, A., Carrasco, A., Benestad, R. (2013), Impact of snow initialization on sub-seasonal forecasts , Clim. Dyn., DOI: 10.1007/s00382-013-1782-0

Jeong, J.H., H.W. Linderholm, S.-H. Woo, C. Folland, B.-M. Kim, S.-J. Kim and D. Chen (2013), Impact of snow initialization on subseasonal forecasts of surface air temperature for the cold season, J. Clim., 26, 1956-1972, doi:10.1175/JCLI-D-12-001.59.1