Search Results

You are looking at 1 - 10 of 13,532 items for :

  • Extratropics x
  • All content x
Clear All
Tapio Schneider and Paul A. O’Gorman

1. Introduction The thermal stratification of the troposphere mediates many aspects of the response of climate to perturbations. For example, it determines the strength of the greenhouse effect and influences the energies and scales of the large-scale eddies that effect most of the transport of heat, mass, momentum, and water vapor in Earth’s extratropical troposphere. Understanding the dynamic processes that control it is therefore essential for understanding the response of climate to

Full access
Pallav Ray and Chidong Zhang

and extratropics (e.g., Ferranti et al. 1990 ; Mo and Higgins 1998 ; Jones and Schemm 2000 ). Major features of the extratropical low-frequency variability could be reproduced by specifying a time-dependent tropical forcing that mimics the convective heating associated with the MJO ( Matthews et al. 2004 ). Thus, forecast of the MJO is essential for the skillful prediction in the tropics and extratropics on the intraseasonal time scale. An important step toward achieving this is to understand

Full access
Peter Knippertz and Andreas H. Fink

-level disturbances intruding from the extratropical North Atlantic into the tropics ( Seck 1962 ; Griffiths 1972 ; Borgne 1979 ; Gaye et al. 1994 ; Issar 1995 ; Buckle 1996 ; Leroux 2001 ). Recently, Knippertz and Fink 2008a , hereafter KF08 ) documented a case of an unusual northward penetration of the rain zone into the countries of Ghana, Togo, Benin, and Nigeria in January 2004. Despite their rare occurrence, dry-season wet events can have substantial impacts on the local hydrology and human

Full access
Y. Ming, V. Ramaswamy, and Gang Chen

1. Introduction The Earth’s climate system comprises distinct regimes, depending mainly on latitude and season. When one moves from the tropics into the wintertime extratropics, stationary Rossby waves and baroclinic eddies overtake the time-mean flow as the main mechanism of poleward energy and moisture transport. In light of the fundamental differences between the two climate regimes, we use this paper to examine specifically the impacts of aerosols on the boreal winter extratropical

Full access
Y. Yu and D-Z. Sun

). Among the global factors that have been suggested to be potentially important in influencing ENSO are the subtropical–extratropical cooling or heating. Using a coupled model, Bush and Philander (1998) investigated the impact of extratropical cooling associated with the Last Glacial Maximum on the tropical Pacific SST. They found that the tropical air–sea interaction amplifies the cooling effect from the high latitudes on the tropics. The attributed this amplification to two factors: 1) the

Full access
Peter Knippertz and Andreas H. Fink

, underlining the substantial disturbance of the hydrology brought about by this single event. Naturally, studies on precipitation in tropical West Africa have focused on the rainy season from June to September, while work on rainfall during the boreal cool and transition seasons have concentrated on events in subtropical North Africa. The latter are often related to equatorward-penetrating extratropical disturbances, termed diagonal troughs due to their orientation from southwest to northeast ( Flohn 1975

Full access
Zhaoyi Shen and Yi Ming

studies using coupled general circulation models (GCMs) have shown the impacts of aerosols on both tropical and extratropical circulation. As a result of the interhemispheric asymmetry in the aerosol forcing, the Hadley circulation weakens (strengthens) in the boreal summer (winter) and the intertropical convergence zone shifts southward ( Ming and Ramaswamy 2011 ). Aerosol-induced cooling results in an equatorward shift of the jet stream, opposite to the GHG-induced change ( Fischer-Bruns et al. 2009

Full access
Lizzie S. R. Froude, Lennart Bengtsson, and Kevin I. Hodges

1. Introduction Extratropical cyclones are important constituents of the general circulation of the atmosphere and are important for the day-to-day weather of the extratropics via their presence or absence. They can be both beneficial, in that they bring most of the rainfall required to sustain human activities such as agriculture, and destructive through excessive rainfall leading to floods, and damaging winds. It is therefore important that these storms are predicted as accurately as possible

Full access
Karen L. Smith, Christopher G. Fletcher, and Paul J. Kushner

1. Introduction Predicting the response of low-frequency modes of atmospheric variability such as the North Atlantic Oscillation and the northern annular mode (NAM; Thompson and Wallace 1998 , 2000 ) to extratropical surface anomalies represents a classical challenge in climate science (e.g., Robinson 2000 ; Kushnir et al. 2006 ). These modes are intrinsically difficult to predict because they are internally generated by tropospheric eddy-mean flow interactions that are stochastic in

Full access
Eun-Pa Lim and Ian Simmonds

1. Introduction Extratropical synoptic systems comprise daily weather patterns in the mid- and high latitudes. In particular, cyclones are often accompanied by rainfall and strong winds and can impact safety and the economy ( Hennessy 2004 ). Moreover, they contribute to maintaining the atmospheric budgets of energy, momentum, and moisture by redistributing them across the globe and thus influencing the larger-scale circulation in which they are embedded. With this in mind, it is important to

Full access