scholarly journals Summer Regional Daily‐Precipitation Extreme Events in Huang‐Huai Rivers Region of China and Their Relationships with Rossby Wave Packet Activities

2021 ◽  
Author(s):  
Siyuan Sun ◽  
Zhaoyong Guan ◽  
Dechao Ye
Keyword(s):  
Wave Packet ◽  
Rossby Wave ◽  
Extreme Events ◽  
Daily Precipitation ◽  
Precipitation Extreme

Estimating return periods for daily precipitation extreme events over the Brazilian Amazon

2015 ◽  
Vol 126 (3-4) ◽  
pp. 585-595 ◽  
Author(s):  
Eliane Barbosa Santos ◽  
Paulo Sérgio Lucio ◽  
Cláudio Moisés Santos e Silva
Keyword(s):  
Extreme Events ◽  
Daily Precipitation ◽  
Brazilian Amazon ◽  
Precipitation Extreme ◽  
Return Periods

scholarly journals Ensemble Sensitivity Tools for Assessing Extratropical Cyclone Intensity and Track Predictability

2013 ◽  
Vol 28 (5) ◽  
pp. 1133-1156 ◽  
Author(s):  
Minghua Zheng ◽  
Edmund K. M. Chang ◽  
Brian A. Colle
Keyword(s):  
Wave Packet ◽  
Great Plains ◽  
Rossby Wave ◽  
Short Wave ◽  
Empirical Orthogonal Functions ◽  
Track Forecast ◽  
Forecast Errors ◽  
Southern Great Plains ◽  
Cyclone Intensity ◽  
Wave Trough

Abstract This paper applies ensemble sensitivity analysis to a U.S. East Coast snowstorm on 26–28 December 2010 in a way that may be beneficial for an operational forecaster to better understand the forecast uncertainties. Sensitivity using the principal components of the leading empirical orthogonal functions (EOFs) on the 50-member European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble identifies the sensitive regions and weather systems at earlier times associated with the cyclone intensity and track uncertainty separately. The 5.5-day forecast cyclone intensity uncertainty in the ECMWF ensemble is associated with trough and ridge systems over the northeastern Pacific and central United States, respectively, while the track uncertainty is associated with a short-wave trough over the southern Great Plains. Sensitivity based on the ensemble mean sea level pressure difference between two run cycles also suggests that the track's shift between the two cycles is linked with the initial errors in the short-wave trough over the southern Great Plains. The sensitivity approach is run forward in time using forward ensemble regression based on short-range forecast errors, which further confirms that the short-term error over the southern plains trough was associated with the shift in cyclone position between the two forecast cycles. A coherent Rossby wave packet originated from the central North Pacific 6 days before this snowstorm event. The sensitivity signals behave like a wave packet and exhibit the same group velocity of ~29° longitude per day, indicating that Rossby wave packets may have also amplified uncertainty in both the cyclone amplitude and track forecast.

scholarly journals Diagnosing the Horizontal Propagation of Rossby Wave Packets along the Midlatitude Waveguide

2017 ◽  
Vol 145 (8) ◽  
pp. 3247-3264 ◽  
Author(s):  
Gabriel Wolf ◽  
Volkmar Wirth
Keyword(s):  
Wave Packet ◽  
Rossby Wave ◽  
Wave Breaking ◽  
Wave Packets ◽  
Wave Activity ◽  
Severe Weather ◽  
Robust Methods ◽  
Misleading Information ◽  
Individual Wave ◽  
Wave Activity Flux

It has been suggested that upper-tropospheric Rossby wave packets propagating along the midlatitude waveguide may play a role for triggering severe weather. This motivates the search for robust methods to detect and track Rossby wave packets and to diagnose their properties. In the framework of several observed cases, this paper compares different methods that have been proposed for these tasks, with an emphasis on horizontal propagation and on a particular formulation of a wave activity flux previously suggested by Takaya and Nakamura. The utility of this flux is compromised by the semigeostrophic nature of upper-tropospheric Rossby waves, but this problem can partly be overcome by a semigeostrophic coordinate transformation. The wave activity flux allows one to obtain information from a single snapshot about the meridional propagation, in particular propagation from or into polar and subtropical latitudes, as well as about the onset of wave breaking. This helps to clarify the dynamics of individual wave packets in cases where other, more conventional methods provide ambiguous or even misleading information. In some cases, the “true dynamics” of the Rossby wave packet turns out to be more complex than apparent from the more conventional diagnostics, and this may have important implications for the predictability of the wave packet.

scholarly journals Implications of the Semigeostrophic Nature of Rossby Waves for Rossby Wave Packet Detection

2015 ◽  
Vol 143 (1) ◽  
pp. 26-38 ◽  
Author(s):  
Gabriel Wolf ◽  
Volkmar Wirth
Keyword(s):  
Wave Packet ◽  
Rossby Wave ◽  
Hilbert Transform ◽  
Wave Packets ◽  
Meridional Wind ◽  
Coordinate Space ◽  
Single Wave ◽  
Planetary Scale ◽  
Complex Demodulation ◽  
The Hilbert Transform

Abstract Upper-tropospheric Rossby wave packets have received increased attention recently. In most previous studies wave packets have been detected by computing the envelope of the meridional wind field using either complex demodulation or a Hilbert transform. The latter requires fewer choices to be made and appears, therefore, preferable. However, the Hilbert transform is fraught with a significant problem, namely, a tendency that fragments a single wave packet into several parts. The problem arises because Rossby wave packets show substantial deviations from the almost-plane wave paradigm, a feature that is well represented by semigeostrophic dynamics. As a consequence, higher harmonics interfere with the reconstruction of the wave envelope leading to undesirable wiggles. A possible cure lies in additional smoothing (e.g., by means of a filter) or resorting to complex demodulation (which implies smoothing, too). Another possibility, which does not imply any smoothing, lies in applying the Hilbert transform in semigeostrophic coordinate space. It turns out beneficial to exclude planetary-scale wavenumbers from this transformation in order to avoid problems in cases when the wave packet travels on a low wavenumber quasi-stationary background flow.

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