Search Results

You are looking at 1 - 10 of 17,471 items for :

  • Refine by Access: All Content x
Clear All
Chao He, Bo Wu, Liwei Zou, and Tianjun Zhou

1. Introduction The atmospheric circulation over subtropical oceans is dominated by basin-scale anticyclones in summer, associated with subsidence, low-level divergence, and anticyclonic wind curl ( Fig. 1 ). The subtropical anticyclones are responsible for the formation of monsoons, subtropical deserts, and Mediterranean-type climate. Given its profound climatic impact, the formation mechanism for the subtropical anticyclone has been thoroughly studied ( Ting 1994 ; Chen et al. 2001

Full access
Piero Cau, John Methven, and Brian Hoskins

1. Introduction The dry regions of the tropical and subtropical troposphere have a significant impact on the water vapor feedback and the atmospheric response to increased anthropogenic gases ( Houghton et al. 2001 ). The relative transparency of a layer of dry air (20% relative humidity) inserted into the average tropical humidity profile was shown by Cau et al. (2005) to lead to an increase in outgoing longwave radiation of about 3 W m −2 (100 hPa) −1 thickness in a clear-sky scenario

Full access
Qiang Fu and Pu Lin

1. Introduction By examining atmospheric temperature trends since 1979 based on satellite-borne microwave sounding unit (MSU) data, Fu et al. (2006) identified the enhanced stratospheric cooling and tropospheric warming in the 15°–45° latitude belts in both hemispheres. The changes in meridional tropospheric temperature gradients in the vicinity of the jets provide evidence that the subtropical jets have been shifting poleward ( Fu et al. 2006 ). However, no interpretation has been presented

Full access
Marcelo E. Seluchi, RenéD. Garreaud, Federico A. Norte, and A. Celeste Saulo

elevation ranges between 1500 and 2500 m ( Fig. 1 ) and then it rises sharply to about 5000 m ASL at subtropical latitudes (25°–35°S). Thus, the subtropical Andes strongly block the zonal flow and separate two distinctive climatic regimes: a relatively cold and dry regime to the west, and a warmer and moister regime to the east ( Seluchi and Marengo 2000 ). At the synoptic scale, the Andes produce a marked disruption in the structure and evolution of the weather systems that cross the continent

Full access
Takamasa Tsubouchi, Toshio Suga, and Kimio Hanawa

1. Introduction Subtropical mode water (STMW), identified as a thermostad or a pycnostad, is formed in winter by intense vertical mixing. Because the evolution of the convection essentially depends on sea surface cooling, STMW is thought to memorize wintertime cooling at the sea surface. Additionally, the temporal variations in volume and temperature of STMW are considered to have an influence on upper ocean stratification and heat content because STMW has a relatively large volume in the

Full access
Wenbo Tang, Manikandan Mathur, George Haller, Douglas C. Hahn, and Frank H. Ruggiero

as DLE ridges, even though they do not induce exponential separation of particles. To distinguish these shear-type LCS from hyperbolic (i.e., attracting or repelling) LCS, we use stability results from Haller (2002) . Shear-type LCS turn out to play an important role in the present flow, as these LCS act as Lagrangian boundaries of a subtropical jet stream. The dataset we analyze here contains high-resolution three-dimensional numerical weather prediction simulations combined with in situ

Full access
Alexandre Couhert, Tapio Schneider, Juilin Li, Duane E. Waliser, and Adrian M. Tompkins

1. Introduction Water vapor plays an essential role in earth’s climate as a mediator of radiative feedbacks in the response of the climate system to perturbations. In particular, the infrared water vapor feedback is strongest in the free troposphere ( Held and Soden 2000 ). Since the infrared radiative forcing associated with changes in atmospheric water vapor concentration scales approximately with relative rather than absolute concentration changes, the subtropical free troposphere has the

Full access
Jack Scheff and Dargan Frierson

1. Introduction One of the most ubiquitous responses of current global climate models (GCMs) to greenhouse warming is the tendency to reduce climatological precipitation in much of the global subtropics and to increase it throughout the high latitudes ( Solomon et al. 2007 ), potentially on time scales of a few decades or less ( Seager et al. 2007 ). Here we compare two prominent, independent characterizations of the twenty-first-century precipitation responses in the World Climate Research

Full access
Keir Colbo and Robert A. Weller

error in the shortwave is simply the annual mean bias in the flux is 5.1 W m −2 and it is dominated by the uncertainty in the incoming shortwave value. c. Sensible heat flux Sensible heat flux ( H ) errors are due to errors in the wind speed ( U 10 ), ocean surface velocity ( U 0 ), air ( T 10 ) and sea surface ( T 0 ) temperatures, and uncertainty in the Stanton number ( S ). For the subtropical sites under discussion, surface ocean velocities are typically small, with means less than 0

Full access
Hsiao-Wei Lai, Christopher A. Davis, and Ben Jong-Dao Jou

(PV) centers and cumulus convection reinforce each other through a positive feedback process. A climatological study by Lee et al. (2006) showed that 11 tropical or subtropical cyclones have formed within the mei-yu front during the previous 30 yr. The incipient low-level disturbances originated over land and the low-level circulations strengthened while moving over the open ocean along the stationary mei-yu front. Increased sea surface temperature (SST), strengthened northeasterlies ( Lee et al

Full access