Search Results

You are looking at 71 - 80 of 2,386 items for :

  • Cold air surges x
  • All content x
Clear All
Niklas Boers, Henrique M. J. Barbosa, Bodo Bookhagen, José A. Marengo, Norbert Marwan, and Jürgen Kurths

fronts on large-scale circulation and associated precipitation anomalies has been thoroughly studied (e.g., Kousky 1979 ; Kiladis and Weickmann 1992 ; Liebmann et al. 1999 ; Siqueira and Machado 2004 ; Siqueira et al. 2005 ). In particular, northward migrating convective disturbances over SESA have been associated with southerly incursions of cold air from midlatitudes ( Garreaud and Wallace 1998 ; Garreaud 2000 ). These authors showed that the convective bands add an important contribution to

Full access
D. Finn, B. Reese, B. Butler, N. Wagenbrenner, K. L. Clawson, J. Rich, E. Russell, Z. Gao, and H. Liu

, about 3–4 h after transition, the cold air pool in the upper valley reached a critical point and spilled over and through the midvalley constriction and accelerated into the lower valley. High downvalley winds persisted downwind of the constriction in the lower valley from 2300 h until after sunrise (~0700–0800 h), tending to gradually decrease following maxima usually occurring between 0100 and 0400 h. GAP was best developed with higher U along the bottom of the lower valley (BLU) and weaker on

Full access
Annick Terpstra, Ian A. Renfrew, and Denis E. Sergeev

1. Introduction In the North Atlantic region heat, moisture, and momentum exchange between the ocean and atmosphere modulates the global oceanic heat transport ( Buckley and Marshall 2016 ; Renfrew et al. 2019 ). Atmospheric forcing is the main driver for this local air–sea exchange and intermittent excursions of cold polar air masses over the open ocean, that is, maritime cold-air outbreak (CAO) events, account for 60%–80% of the wintertime ocean heat loss ( Papritz and Spengler 2017 ). In

Open access
Fayçal Lamraoui, James F. Booth, and Catherine M. Naud

subtropical Azores high-pressure system. It is subject to midlatitude cold-air outbreaks, including those that follow cold frontal passages, which are favorable to the formation of low marine boundary layer clouds. Thus, the ENA site represents a prime location to study marine stratocumulus and shallow cumulus regimes under the influence of midlatitude storms ( Rémillard et al. 2012 ; Rémillard and Tselioudis 2015 ). To achieve our objective of understanding the sensitivity of the simulated cold frontal

Full access
Anthony R. Lupo, Joseph J. Nocera, Lance F. Bosart, Eric G. Hoffman, and David J. Knight

1. Introduction In the past, there have been relatively few studies that have examined the characteristics of South America cold surges [e.g., Marengo et al. (1997a , b) ; selected previous South American cold-air surge studies are listed in Table 1 ] as compared to studies of cold surges in the Northern Hemisphere (e.g., Boyle and Chen 1987 ; Mecikalski and Tilley 1992 ; Reding 1992 ; Konrad 1996 ; Schultz et al. 1997 , 1998 ). Cold surges in South America can occur frequently during

Full access
David M. Schultz, W. Edward Bracken, and Lance F. Bosart

channeling along the Sierra Madre, favored the extraordinary equatorward incursion of the cold air. That case study, and the issues raised therein, suggests that a more comprehensive approach to examining cold- surge structure and evolution is required. As in Reding (1992) and Schultz et al. (1997) , a Central American cold surge (CACS) is defined in this paper as the leading edge of a cold anticyclone originating poleward of Mexico that has penetrated equatorward to at least 20°N. The principal

Full access
David M. Schultz, W. Edward Bracken, Lance F. Bosart, Gregory J. Hakim, Mary A. Bedrick, Michael J. Dickinson, and Kevin R. Tyle

1. Introduction a. Background A dramatic example of the interaction between the Tropics and the midlatitudes is cold fronts from the central United States that penetrate into Mexico and Central America. These surges of cold air are associated with anticyclones that often occur in the wake of cyclogenesis east of the Rocky or Sierra Madre Mountains and can bring strong gusty northerly winds up to 30 m s −1 , air temperature decreases of 15°C in 24 h, persistent low

Full access
Dehai Luo, Yiqing Xiao, Yao Yao, Aiguo Dai, Ian Simmonds, and Christian L. E. Franzke

Siberian temperature anomaly. However, in a long-term perspective, cold surface air temperature (SAT) anomalies are absent over midlatitude Eurasia, although strong positive SAT anomalies appear over the less ice-covered regions around Greenland and over the Barents Sea ( Deser et al. 2000 , their Fig. 7). The numerical experiments of Sato et al. (2014) also indicated that the local response to the heating due to the sea ice loss over the Barents Sea does not produce a midlatitude cold anomaly over

Full access
James S. Boyle

climatological maximum in confluence at 400 mb (quasi-geostrophic frontogenesis) found over EastAsia is seen to be, for the most part, the result of intensified confluence accompanying the surge event. Thisfrontogenesis is necessary for the temperature field to remain in thermal-wind balance with the accelerating jet.There is also marked low-level frontogenesis taking place at lower levels as the cold air sweeps southward. The low-level eddy heat fluxes, which have a large maxima on the East Asian coast

Full access
Yoshiki Fukutomi and Tetsuzo Yasunari

between the meridional surge and the westerly burst on these shorter time scales in the Tropics. From a viewpoint of large-scale tropical–extratropical connection over the Indian Ocean, some important implications of extratropical forcing of tropical atmosphere were presented by also other authors. For example, Yasunari (1981a , b )) suggested that the SH midlatitude westerly disturbance cause cold air penetration into the tropical Indian Ocean region, which can play a role in initiating cloud

Full access