Search Results

You are looking at 101 - 110 of 3,109 items for :

  • Forecasting techniques x
  • Journal of Climate x
  • All content x
Clear All
Nicholas M. J. Hall, Hervé Douville, and Laurent Li

) style experiments with a simple GCM]. For more realistic simulations in more comprehensive models, a practical alternative to imposing a tropical thermal anomaly is to constrain the tropical dynamics directly with data. The causal assumption remains the same: the direction of influence is from the tropical flow to the extratropics, and we trust that the result will be useful enough to justify this causal assumption. Experiments that follow this philosophy often use a nudging technique, laid out in

Full access
Leopold Haimberger

. ECMWF Seminar on Recent Developments in Data Assimilation for Atmosphere and Ocean, Reading, United Kingdom, ECMWF, 65–74 . Dee , D. P. , and A. Da Silva , 1998 : Data assimilation in the presence of forecast bias. Quart. J. Roy. Meteor. Soc. , 124 , 269 – 295 . DeGroot , M. H. , 1986 : Probability and Statistics . Addison Wesley, 723 pp . Ducre-Robetaille , J. , L. Vincent , and D. Boulet , 2003 : Comparison of techniques for detection of discontinuities in temperature

Full access
Mitchell Bushuk and Dimitrios Giannakis

24–48 months, respectively ( Koenigk and Mikolajewicz 2009 ; Holland et al. 2011 ; Blanchard-Wrigglesworth et al. 2011b ; Tietsche et al. 2014 ; Germe et al. 2014 ). This gap between operational and perfect model prediction skill represents the forecast skill improvements potentially achievable via improved model physics and/or initial conditions. Achieving these forecast improvements depends crucially on understanding, as well as accurately initializing and simulating, the physical

Full access
Irene Polo, Albin Ullmann, Pascal Roucou, and Bernard Fontaine

them ( Robertson et al. 2000 ; Ghil and Robertson 2002 ; Cassou et al. 2004b ). Can such changes over the North Atlantic/Mediterranean sector be important in terms of climate impacts, particularly for the subtropical–tropical convection variability over West Africa (WA)? This question requires defining WRs from daily atmospheric data from the May to October (MJJASO) season and projecting them onto rainfall information. The European Centre for Medium-Range Weather Forecasts (ECMWF) Re

Full access
P. A. Mooney, C. Broderick, C. L. Bruyère, F. J. Mulligan, and A. F. Prein

where the diurnal cycle is atypical. This study uses an innovative diagnostic approach that clusters observations to examine the role of physical parameterizations in the simulation of the summertime (JJA) diurnal cycle of precipitation across the contiguous United States, an area characterized by strong regional differences. Clustering was implemented using the k -means algorithm ( Wilks 2011 ) to identify regions that possess a similar diurnal cycle of precipitation. This technique has a long

Full access
N. J. Matthewman, J. G. Esler, A. J. Charlton-Perez, and L. M. Polvani

generally in the 1.5–1.9 range, with the largest values occurring in February in the lower stratosphere. Results will be presented below with reference to this climatology. Nevertheless, the focus in the Waugh (1997) and Waugh and Randel (1999) studies was not the three-dimensional evolution of the polar vortex during SSWs themselves. Here, the elliptical diagnostic approach, which was adapted from techniques developed in the fluid dynamics literature to investigate two-dimensional vortex dynamics

Full access
Christopher W. Landsea, Gabriel A. Vecchi, Lennart Bengtsson, and Thomas R. Knutson

additional TC per year had been identified and included in HURDAT because of new tools and techniques such as Quick Scatterometer (QuikSCAT) satellite imagery ( Atlas et al. 2001 ), the Advanced Microwave Sounding Unit ( Brueske and Velden 2003 ), and the Cyclone Phase Space analyses ( Hart 2003 ). These methods have allowed for the detection of very short-lived systems that might not have been analyzed as having gale force winds previously as well as more accurate differentiation of cyclones that were

Full access
Muthuvel Chelliah and C. F. Ropelewski

> 0.8, generally r > 0.9. This suggests that the reanalysis may be useful for comparisons with numerical model–generated forecast fields and in conjunction with fingerprint techniques to identify climate change. In comparisons of the simple linear trends present in each dataset for the 1980–90 period, each of the reanalyses had spatial patterns similar to MSU Ch2 except that the NCEP reanalysis showed smaller positive trends compared to the MSU, while the ERA reanalysis showed larger positive

Full access
Willem A. Landman and Simon J. Mason

1. Introduction A number of models have been developed for making extended-range forecasts of sea surface temperature anomalies of the equatorial Pacific Ocean over lead times of several seasons (e.g., Barnett 1984 ; Zebiak and Cane 1987 ; Kirtman and Schopf 1998 ; Barnston and Ropelewski 1992 ; Ji et al. 1996 ; Anderson and Davey 1998 ; Stockdale et al. 1998 ; Tangang et al. 1998 ; Burgers 1999 ). The equatorial Pacific Ocean has been targeted by modelers because of its importance to

Full access
K. R. Sperber and T. N. Palmer

Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, Berkshire, United Kingdom(Manuscript received 12 October 1995, in final form 23 February 1996) ABSTRACT The interannual variability of rainfall over the Indian subcontinent, the African Sahel, and the Nordeste regionof Brazil have been evaluated in 32 models for the period 1979-88 as part of the Atmospheric Model Intercomparison Project (AMIP). The interannual variations of Nordeste rainfall are the most

Full access