scholarly journals Long-term Variation of the Sea Level Pressure Field in the East Asia and Western Pacific Region

1996 ◽  
Vol 69 (10) ◽  
pp. 793-816
Author(s):  
Motoki NISHIMORI ◽  
Tetsuzo YASUNARI
2021 ◽  
Vol 28 (2) ◽  
Author(s):  
I. G. Shokurova ◽  
A. A. Kubryakov ◽  
M. V. Shokurov ◽  
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Purpose. The paper is aimed at studying the relationship between the wind regime and the wind stress curl in the Black Sea and the long-term changes in the large-scale sea level pressure field in winter months. Methods and Results. The data on wind speed and sea level pressure in January – February from the NCEP/NСAR reanalysis for 1948–2018 are used. Based on the 6-hour data, the synoptic conditions accompanied by high and low values of the wind stress curl in the sea were determined. The synoptic situations in which a vast anticyclone is located north and northeast of the sea, and the area of low pressure – to the southwest of the sea in the Mediterranean region, are accompanied by the northeast and east winds, and by the cyclonic curl predominance. On the contrary, passing of the cyclones to the north of the sea and increase of pressure to the southwest are followed by the westerly and southwesterly winds, and by the anticyclonic curl predominance. Extremely high monthly mean values of the cyclonic curl were observed in those years, when the area occupied by the Siberian anticyclone increased and expanded westward, so that the Black Sea was on the southwestern periphery of its spur. Extremely low values of the anticyclonic curl were noted when the Azores anticyclone area expanded to the Mediterranean region. The wind stress curl changes on the multidecadal scales have shown its relation to the global changes in the field of the sea level pressure and the sign of the pressure anomalies at the low latitudes. Conclusions. The opposite sign of the surface pressure anomalies to the northeast and southwest of the sea is accompanied by the highest values of the wind stress curl.


2013 ◽  
Vol 141 (11) ◽  
pp. 3769-3785 ◽  
Author(s):  
Akira Kuwano-Yoshida ◽  
Takeshi Enomoto

Abstract The predictability of explosive cyclones over the northwestern Pacific region is investigated using an ensemble reanalysis dataset. Explosive cyclones are categorized into two types according to whether the region of the most rapid development is in the Sea of Okhotsk or Sea of Japan (OJ) or in the northwestern Pacific Ocean (PO). Cyclone-relative composite analyses are performed for analysis increments (the differences between the analysis and the 6-h forecast) and ensemble spreads (the standard deviations of ensemble members of the analysis or first guess) at the time of the maximum deepening rate. The increment composite shows that the OJ explosive cyclone center is forecast too far north compared to the analyzed center, whereas the PO explosive cyclone is forecast shallower than the analyzed center. To understand the cause of these biases, a diagnosis of the increment using the Zwack–Okossi (Z-O) development equation is conducted. The results suggest that the increment characteristics of both the OJ and PO explosive cyclones are associated with the most important cyclone development mechanisms. The OJ explosive cyclone forecast error is related to a deeper upper trough, whereas the PO explosive cyclone error is related to weaker latent heat release in the model. A diagnosis of the spread utilizing the Z-O development equation clarifies the mechanism underlying the uncertainty in the modeled sea level pressure. For OJ explosive cyclones, the spread of adiabatic warming causes substantial sea level pressure spreading southwest of the center of the cyclones. For PO explosive cyclones, the latent heat release causes substantial sea level pressure spreading around the cyclone center.


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