Abstract The interactions and teleconnections between the tropical midlatitude regions on intraseasonal time scales are an important modulator of extratropical circulation anomalies their associated weather patterns. These arise due to impact tropics extratropics, midlatitudes tropics, two‐way regions. Observational evidence, as well theoretical studies with models complexity ranging from linear barotropic framework intricate Earth system models, suggest involvement a myriad processes...

Dynamical Seasonal Prediction (DSP) is an informally coordinated multi-institution research project to investigate the predictability of seasonal mean atmospheric circulation and rainfall. The basic idea test feasibility extending technology routine numerical weather prediction beyond inherent limit deterministic produce climate predictions using state-of-the-art global models. Atmospheric general models (AGCMs) either forced by predicted sea surface temperature (SST) or as part a coupled...

The primary effect of El Niño–Southern Oscillation (ENSO) sea surface temperature (SST) anomalies is to force distinct midlatitude patterns, and not only modify the probability internal variability patterns [such as Pacific–North American (PNA) pattern Wallace Gutzler]. Both spatial structure distribution external ENSO are from PNA pattern. Ensemble general circulation model (GCM) integrations for 30 winters have been analyzed in America region. These span recent period 1981/82 through...

A two-layer baroclinic model is used to study the planetary-scale motions of a thermally driven atmosphere in presence topography, and doing so extend previous results obtained with barotropic model. Highly truncated spectral equations are obtain multiple wavelike stationary equilibrium states, examine instabilities that produce them, feed on them give rise traveling planetary waves. Although equilibria cannot exist without orography, their energy comes from potential mean flow, not kinetic...

Abstract The extratropical atmosphere is characterized by robust circulations which have time scales longer than that associated with developing baroclinic systems but shorter a season. Such low‐frequency variability governed to large extent nonlinear dynamics and, hence, chaotic. A useful aspect of this circulation it can often be described just few quasi‐stationary regime states, broadly defined as recurrent or persistent large‐scale structures, exert significant impact on the probability...

Abstract In early 2018, Cape Town (population ~3.7 million) was at risk of being one the first major metropolitan areas in world to run out water. This due a severe multi-year drought that led levels supply dams falling an unprecedented low. Here we analyze rainfall data from city catchment areas, including rare centennial records surrounding region, assess severity 2015–2017 drought. We find there has been long-term decline number winter days, but this trend generally masked by fluctuations...

Abstract The circulation regimes in the Pacific–North American region are studied using NCEP–NCAR reanalyses for 18-winter period (1981/82–1998/99; NCEP18) and 54-winter (1948/49–2001/02; NCEP54). sampling properties of estimated very large ensembles (of size 55) winter simulations made NCEP18 with atmospheric general model Center Ocean–Land–Atmosphere Studies, forced by observed SST sea ice. identified a modified version k-means method. From NCEP54 dataset set four clusters was found [i.e.,...

Mean climate and intraseasonal to interannual variability of two versions the Community Climate System Model (CCSM) coupled atmosphere‐ocean general circulation model (CGCM) are analyzed. The first version is standard CCSM, in which cloud effects on large‐scale represented via parameterizations. second includes “super‐parameterization” (SP) convective processes by replacing parameterized with a two‐dimensional (2D) cloud‐process resolving (CRM) at each CGCM grid column. SP‐CCSM improves...

A series of sensitivity experiments are conducted in an attempt to understand and correct deficiencies the simulation seasonal mean Indian monsoon with a global atmospheric general circulation model. The precipitation is less than half that observed. This poor integrations independent choice initial conditions sea surface temperature data used. Experiments performed test changes orography, vegetation, soil wetness, cloudiness. authors find deficiency model may be attributed use enhanced...

Abstract The winter response of the atmosphere to El Nino events in Pacific is studied both from a 14-year integration Center for Ocean–Land–Atmosphere GCM using observed SSTs January 1979 February 1993 and corresponding analyses ECMWF. Emphasis put on shift high-frequency transients that define storm track during warm events. Warm normal ensembles are defined basis GCM’s diabatic heating field tropical Pacific, which falls one two states. During winters 1982/83, 1986/87, 1991/92, averaged...

Abstract Fast and slow Madden–Julian oscillation (MJO) episodes have been identified from 850- 200-hPa zonal wind outgoing longwave radiation (OLR) for 32 winters (16 October–17 March) 1980/81–2011/12. For 26 fast cases the OLR took no more than 10 days to propagate phase 3 (convection over Indian Ocean) 6 western Pacific). 8 propagation at least 20 days. episode composite anomalies of 500-hPa height (Z500) show a developing Rossby wave in mid-Pacific with downstream through MJO phases 2–4....

A calculation is presented of the total energy metallic hydrogen for a family face-centered tetragonal lattices carried out within self-consistent phonon approximation. The proton motion large and proper inclusion dynamics alters structural dependence energy, causing isotropic to become favored. For dynamic lattice terms third higher order in electron-proton interaction greatly reduced from static equivalents.

Abstract It is shown that the dominant structure of seasonal‐mean mid‐latitude circulation (500 hPa height) pattern over Pacific‐North America (PacNA) region forced by tropical sea surface temerature (SST)‐related diabatic heating, distinctly different from internal variability occurs in absence El Niño Southern Oscillation (ENSO) related SST anomalies. The separation these two patterns accomplished utilizing ensemble General Circulation Model (GCM) integrations conjunction with re‐analyses....

A comparative study of the limit predictability in stratosphere and troposphere a coupled general circulation model is carried out using National Center for Environmental Prediction (NCEP) Climate Forecast System Interactive Ensemble (CFSIE). In “identical twin experiments”, we compare forecast errors zonal wind potential temperature various wave groups. The results show smaller intrinsic error growth lower compared with troposphere. sudden stratospheric warming events, measured by...

The purpose of this paper is to study the influence tropical sea surface temperature (SST) on midlatitude circulation regime behavior in Pacific–North American region. Toward end, a cluster analysis has been applied 55-member ensembles winter seasonal simulations Center for Ocean–Land–Atmosphere Studies general model 18 winters. ensemble members each utilize same prescribed, observed weekly varying SST that winter. includes all fluctuations with time scales longer than 10 days except mean...

Analyzed global data from the European Centre for Medium Range Weather Forecasts FGGE year are projected onto Hough functions at each synoptic time and series filtered to retain all westward propagating components on scales less than seasonal. The evolution of mode phase agrees closely with Rossby wave theory whenever amplitudes not small. amplitude is described as irregular vacillation. first three zonal meridional wavenumbers studied. total field can be large 130 m potentially explain a...

Abstract Series of forecast experiments for two seasons investigate the impact specifying realistic initial states land in conjunction with observed ocean and atmosphere while using National Center Atmospheric Research (NCAR) Community Climate System Model, version 3 (CCSM3.0). Since direct soil moisture observations adequate initialization surface do not exist, this study considers proxy data. The authors are able to successfully initialize all components CCSM3.0 produce a good...

Abstract The climate system model of the National Center for Atmospheric Research is used to examine predictability arising from land surface initialization seasonal ensemble forecasts in current, preindustrial, and projected future settings. Predictability defined terms model's ability predict its own interannual variability. this relatively weak compared estimates other models but has much same spatial temporal structure found previous studies. Several factors appear contribute weakness,...

The linear trends for a number of fields obtained from the reanalyses National Centers Environmental Prediction–National Center Atmospheric Research (NCEP–NCAR) are calculated Northern Hemisphere winter months (January–March) 55-yr period 1948–2002. include sea level pressure (SLP); geopotential height at 500 and 50 hPa; temperature zonally averaged height; temperature; zonal, meridional, vertical velocities 1000 to surface air (SAT). trend expressed in terms two alternate expansions: (i)...

Abstract The occurrence of boreal winter Rossby wave breaking (RWB) along with the quantitative role synoptic transient eddy momentum and heat fluxes directly associated RWB are examined during development Euro-Atlantic circulation regimes using ERA-Interim. Results compared to those from seasonal reforecasts made Integrated Forecast System model ECWMF coupled NEMO ocean model. both Scandinavian blocking Atlantic ridge is coincident anticyclonic (AWB); however, do not contribute (and, in...