Search Results

You are looking at 71 - 80 of 17,235 items for :

  • All content x
Clear All
Ulrike Wissmeier and Robert Goler

1. Introduction The city of Darwin lies within the tropics of northern Australia and records an average of 80 days of thunder each year. Although tropical thunderstorms are not usually expected to be severe 1 due to the generally weak vertical wind shear present, the Darwin area records an average of 12 severe storm events during the “build-up” and wet season (October to May) each year ( Chappel 2001 ). During the four wet seasons in 2002/03–2005/06, the probability of detection of severe

Full access
David W. Pierce, Tim P. Barnett, and Mojib Latif

Philander (1997) extended the isopycnal advection idea to a theory in which such anomalies play a key role in generating decadal-scale climate variability. Essentially, advection along isopycnals provides a decadal-scale delay, while amplification of advected thermal anomalies that reach the surface in the Tropics keeps the oscillations self-sustaining in the presence of noise and dissipation. The idea of a tropical–midlatitude connection via wave propagation was addressed by Lysne et al. (1997

Full access
Noel E. Davidson, Kevin J. Tory, Michael J. Reeder, and Wasyl L. Drosdowsky

there existed enhanced ascent and moistening over the monsoon, suggesting that preconditioning for onset had commenced much earlier than that indicated by the zonal wind changes alone. The first aim of this study is to document these structural changes. Various physical mechanisms have the potential to influence the onset of the Australian monsoon and convective outbreaks over the Tropics generally. They include extratropical–tropical interaction ( Lim and Chang 1981 ; D83 ; Keenan and Brody 1988

Full access
Caio A. S. Coelho and Lisa Goddard

1. Introduction The majority of drought-related hazards and the attendant economic losses and mortality risks reside in the tropics ( Dilley et al. 2005 ). Changes in climate variability, including more frequent and damaging extreme events such as drought, is one of many anticipated impacts of climate change. Estimating how climate variability may change in a warmer world, and how that variability intersects with more slowly evolving climate change, is vitally important to climate risk

Full access
JOHN R. BENNETT and JOHN A. YOUNG

, the northward component of velocity. The equation is analyzed as an eigenvalue problem and solvednumerically for the free modes of the Tropics for the case with zero mean flow. These solutions are compared withsolutions that are forced at a boundary situated in mid-latitudes, for cases with and without a mean zonal flow. At "critical latitnde.s," the basic equation has a singularity (where the phase speed of a wave forced at theboundary is equal to the mean flow). The caw for forced motions is

Full access
Tadashi Tsuyuki

NOVEMBER 1996 T S U Y U K I 2545Variational Data Assimilation in the Tropics Using Precipitation Data. Part II: 3D Mode~ TADASHI TSUYUKI *Department of Meteorology, The Florida State University, Tallahassee, Florida(Manuscript received 10 August 1995, in final form 2 November 1995)ABSTRACT A global primitive equation model is used to examine the performance of four

Full access
William A. Heckley, Graeme Kelly, and Michael Tiedtke

coverage of outward-goinglongwave radiation across the global tropics and subtropics four times a day. Fractional coverage of cold cloudis obtained from this, which is then interpreted as rainfall rates. This information is introduced into the ECMWFdata assimilation system as diabatic heating through the nonlinear normal-mode initialization scheme. Substantialimpact on the analyses is found.1. Introduction Analysis systems, as used to provide initial conditions for numerical weather forecasts

Full access
Dargan M. W. Frierson

1. Introduction Our picture of the Tropics is continually changing with the addition of new observations in this relatively data-sparse region. Many of these recent observations have provided compelling empirical tests for the theoretically based aspects of convection schemes, and the choice of parameters therein. For instance, the study of Brown and Bretherton (1997) demonstrates the correlation between boundary layer moist static energy and free tropospheric temperature, as postulated in

Full access
Michelle R. McCrystall, J. Scott Hosking, Ian P. White, and Amanda C. Maycock

tropical SST trends over the same period and concluded that the local geopotential height and surface temperature trends were a consequence of tropical SST trends. They posited a mechanism related to a poleward propagating Rossby wave train emanating from the tropical Pacific (also Trenberth et al. 2014 ). While the reanalysis trends in wave activity flux (WAF) shown by D14 also indicate a poleward propagating wave train from the tropics toward NCG, there were differences in the wave propagation

Restricted access
ARNOLD GRUBER, LEROY HERMAN, and ARTHUR F. KRUEGER

cloud-producingcirculation features. These biases appear to be smallest in the Tropics and, consequently, the winds here can be veryuseful for studies of the average circulation at low latitudes. Some of the important features of this circulation overthe equatorial Pacific are clearly revealed.1. INTRODUCTIONThe purpose of this note is to present and evaluatesome preliminary computations of resultant winds overthe Pacific Ocean as deduced from ATS 1 cloud motionsfor November 1969. ATS 1 is a

Full access