High sensitivity to the initial condition for the prediction of stratospheric sudden warming

Mukougawa, Hitoshi; Sakai, Hirokazu; Hirooka, Toshihiko

doi:10.1029/2005gl022909

Cited by 54 publications

(59 citation statements)

References 13 publications

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“…This result illustrates why the forecast of a cold December is sensitive to the North Atlantic blocking high in midNovember. It is interesting to note that high sensitivity to initial atmospheric conditions has also been found in forecast experiments of the sudden stratospheric warming of December 2001 (Mukougawa et al 2005). In this case too, successful forecast of sudden warming critically depends on the forecast of the North Atlantic blocking occurring two weeks earlier.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 98%

Forecast Study of the Cold December of 2005 in Japan: Role of Rossby Waves and Tropical Convection

Inaba¹,

Kodera

2010

Journal of the Meteorological Society of Japan

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Japan experienced unusually heavy snowfall and low temperatures in December 2005 owing to the cold air advected from Siberia. As a result of this strong and sustained cold surge, record-breaking snowfalls occurred repeatedly along the coast of the Sea of Japan. To determine the cause and to examine the accuracy of numerical forecasts of such unusual weather as well as to investigate the impact of initial and boundary conditions on the forecasts, we conducted one-month ensemble forecasts for December 2005 by changing lower boundary conditions, such as sea-surface temperature (SST) and sea-ice coverage (SIC). Forecasts were initiated every day between November 1 and December 1 to investigate their dependency on initial atmospheric conditions. Our results showed that SST and SIC appeared to have little impact on the forecasts of a cold December in Japan. Instead, high sensitivity to initial atmospheric conditions was found. Almost all forecasts initiated before November 16, 2005 failed to reproduce the cold December; however, those initiated after that date successfully predicted it.By comparing the di¤erences between successful and unsuccessful members for predicting the cold December, we identified the processes producing the cold December of 2005. In the successful forecasts, we found that blocking developed over the North Atlantic in mid-November 2005. When it decayed, the emitted Rossby waves propagated along the subpolar jet across Siberia, inducing a cold surge over Japan. Moreover, the Rossby waves propagating over the Indian sector along the subtropical jet gave rise to intense convection over the Bay of Bengal and the South China Sea, which led to the deepening of a low-pressure trough over Japan. The unusual weather conditions in December have been due to the simultaneous occurrence of these two processes.

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Section: Discussion and Concluding Remarksmentioning

confidence: 98%

Forecast Study of the Cold December of 2005 in Japan: Role of Rossby Waves and Tropical Convection

Inaba¹,

Kodera

2010

Journal of the Meteorological Society of Japan

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“…In fact, such skill improvement during a stratospheric sudden warming (SSW) event was demonstrated by Reichler et al (2005) and Kuroda (2008). In addition, the predictability of the stratosphere during the occurrence periods of SSW events quickly has attracted much interest (e.g., Mukougawa and Hirooka 2004;Mukougawa et al 2005;Marshall and Scaife 2010), as described below.…”

Section: Introductionmentioning

confidence: 99%

“…It was also revealed that the RMSE was enlarged during the SSW and then the circulation was difficult to predict, which was mainly caused by the poor prediction of the phase of planetary waves, i.e., the location of their troughs and ridges. Mukougawa et al (2005) further investigated the predictability of a major warming in December 2001 using all ensemble members of the JMA 1-month forecasts. They reported that the warming peak was predictable at least from 2 weeks in advance in terms of the 10-hPa zonal-mean temperature at 80°N.…”

Section: Introductionmentioning

confidence: 99%

Predictability Changes of Stratospheric Circulations in Northern Hemisphere Winter

Ichimaru

Noguchi

Hirooka

et al. 2016

Journal of the Meteorological Society of Japan

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Practical predictability of the stratospheric circulation in the boreal winters during the period [2001][2002][2003][2004][2005][2006] has been examined using the archive of 1-month ensemble forecast datasets provided by the Japan Meteorological Agency. To investigate the predictability limit, two measures of the Root-Mean-Square Error (RMSE) and Anomaly Correlation (AC) have been used for the 10-hPa geopotential height field. In the winter stratosphere, an intermittent character of planetary wave activity causes two specific periods of the stratospheric circulation, i.e., an undisturbed phase with inactive planetary waves and a disturbed phase with active ones. Therefore, the predictability needs to be evaluated taking account of this feature. On the basis of careful consideration, the mean predictable period can be estimated to about 10 days during the disturbed phase; it is longer than the tropospheric predictable period of about 7 days. However, it exhibits large variability because of different growth rates of forecast errors caused by contributions of both wave and zonal-mean fields. During the undisturbed phase, the predictable period based on the AC is almost the same as that of the disturbed phase, although the predictable period based on the RMSE is extremely long, since the RMSE predictability is measured against the climatological standard deviation affected by disturbed phases. Therefore, the horizontal pattern of the stratospheric circulation is less predictable even though the forecast error is quite small.

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“…For example, Mukougawa et al (2005) have shown that the formation of a blocking ridge over the North Atlantic was important for the enhancement of upward propagation of planetary-wave activity into the stratosphere and the warming of the polar stratosphere observed in December 2001. Mukougawa et al (2007) have confirmed the above result through hindcast experiments with initial conditions in which the observed blocking-flow configuration was artificially perturbed.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional evolution of ensemble forecast spread during the onset of a stratospheric sudden warming event in January 2006

Nishii

Nakamura

2010

Q.J.R. Meteorol. Soc.

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A singular value decomposition and a simple sensitivity analysis applied to an operational ensemble of monthly forecasts reveal that the prediction skill of a stratospheric sudden warming event observed in late January 2006 is particularly sensitive to uncertainty in the initial state in the vicinity of a developing synopticscale cyclone that was observed over the North Pacific more than two weeks prior to the peak of the event. For the first few days in the forecast, a local maximum of the forecast spread around the cyclone is translated eastward across the Pacific in association with observed downstream development of synoptic-scale disturbances. The spread then reaches the subpolar North Atlantic, where a blocking ridge was developing as the source of an upward-propagating Rossby-wave packet that gave rise to the deceleration of the stratospheric polar-night jet (PNJ). Following the observed wave packet, the maximum forecast spread is translated upward from the ridge and finally reaches the stratosphere, causing a large forecast spread in the PNJ deceleration.

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High sensitivity to the initial condition for the prediction of stratospheric sudden warming

Cited by 54 publications

References 13 publications

Forecast Study of the Cold December of 2005 in Japan: Role of Rossby Waves and Tropical Convection

Forecast Study of the Cold December of 2005 in Japan: Role of Rossby Waves and Tropical Convection

Predictability Changes of Stratospheric Circulations in Northern Hemisphere Winter

Three-dimensional evolution of ensemble forecast spread during the onset of a stratospheric sudden warming event in January 2006

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