TY - JOUR
T1 - Examining the Predictability of the Stratospheric Sudden Warming of January 2013 Using Multiple NWP Systems
AU - Tripathi, Om P.
AU - Baldwin, Mark
AU - Charlton-Perez, Andrew
AU - Charron, Martin
AU - Cheung, Jacob C.H.
AU - Eckermann, Stephen D.
AU - Gerber, Edwin
AU - Jackson, David R.
AU - Kuroda, Yuhji
AU - Lang, Andrea
AU - McLay, Justin
AU - Mizuta, Ryo
AU - Reynolds, Carolyn
AU - Roff, Greg
AU - Sigmond, Michael
AU - Son, Seok Woo
AU - Stockdale, Tim
N1 - Publisher Copyright:
© 2016 American Meteorological Society.
PY - 2016/5/1
Y1 - 2016/5/1
N2 - The first multimodel study to estimate the predictability of a boreal sudden stratospheric warming (SSW) is performed using five NWP systems. During the 2012/13 boreal winter, anomalous upward propagating planetary wave activity was observed toward the end of December, which was followed by a rapid deceleration of the westerly circulation around 2 January 2013, and on 7 January 2013 the zonal-mean zonal wind at 60°N and 10 hPa reversed to easterly. This stratospheric dynamical activity was followed by an equatorward shift of the tropospheric jet stream and by a high pressure anomaly over the North Atlantic, which resulted in severe cold conditions in the United Kingdom and northern Europe. In most of the five models, the SSW event was predicted 10 days in advance. However, only some ensemble members in most of the models predicted weakening of westerly wind when the models were initialized 15 days in advance of the SSW. Further dynamical analysis of the SSW shows that this event was characterized by the anomalous planetary wavenumber-1 amplification followed by the anomalous wavenumber-2 amplification in the stratosphere, which resulted in a split vortex occurring between 6 and 8 January 2013. The models have some success in reproducing wavenumber-1 activity when initialized 15 days in advance, but they generally failed to produce the wavenumber-2 activity during the final days of the event. Detailed analysis shows that models have reasonably good skill in forecasting tropospheric blocking features that stimulate wavenumber-2 amplification in the troposphere, but they have limited skill in reproducing wavenumber-2 amplification in the stratosphere.
AB - The first multimodel study to estimate the predictability of a boreal sudden stratospheric warming (SSW) is performed using five NWP systems. During the 2012/13 boreal winter, anomalous upward propagating planetary wave activity was observed toward the end of December, which was followed by a rapid deceleration of the westerly circulation around 2 January 2013, and on 7 January 2013 the zonal-mean zonal wind at 60°N and 10 hPa reversed to easterly. This stratospheric dynamical activity was followed by an equatorward shift of the tropospheric jet stream and by a high pressure anomaly over the North Atlantic, which resulted in severe cold conditions in the United Kingdom and northern Europe. In most of the five models, the SSW event was predicted 10 days in advance. However, only some ensemble members in most of the models predicted weakening of westerly wind when the models were initialized 15 days in advance of the SSW. Further dynamical analysis of the SSW shows that this event was characterized by the anomalous planetary wavenumber-1 amplification followed by the anomalous wavenumber-2 amplification in the stratosphere, which resulted in a split vortex occurring between 6 and 8 January 2013. The models have some success in reproducing wavenumber-1 activity when initialized 15 days in advance, but they generally failed to produce the wavenumber-2 activity during the final days of the event. Detailed analysis shows that models have reasonably good skill in forecasting tropospheric blocking features that stimulate wavenumber-2 amplification in the troposphere, but they have limited skill in reproducing wavenumber-2 amplification in the stratosphere.
KW - Circulation/Dynamics
KW - Ensembles
KW - Forecasting
KW - Model evaluation/performance
KW - Models and modeling
KW - Numerical weather prediction/forecasting
KW - Operational forecasting
KW - Stratospheric circulation
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U2 - 10.1175/MWR-D-15-0010.1
DO - 10.1175/MWR-D-15-0010.1
M3 - Article
AN - SCOPUS:84966349350
SN - 0027-0644
VL - 144
SP - 1935
EP - 1960
JO - Monthly Weather Review
JF - Monthly Weather Review
IS - 5
ER -