Enda William O'Brien

Parallel Programming Services

This paper assesses the skill of the Saudi-King Abdulaziz University coupled ocean–atmosphere Global Climate Model, namely Saudi-KAU CGCM, in forecasting the El Niño-Southern Oscillation (ENSO)-related sea surface temperature. The model performance is evaluated based on a reforecast of 38 years from 1982 to 2019, with 20 ensemble members of 12-mont...

This paper presents projected changes in extreme temperature and precipitation events by using Coupled Model Intercomparison Project phase 6 (CMIP6) data for mid-century (2036–2065) and end-century (2070–2099) periods with respect to the reference period (1985–2014). Four indices namely, Annual maximum of maximum temperature (TXx), Extreme heat wav...

We evaluate the performance of a large ensemble of Global Climate Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) over South America for a recent past reference period and examine their projections of twenty-first century precipitation and temperature changes. The future changes are computed for two time slices (2040–20...

The Coupled Model Intercomparison Project Phase 6 (CMIP6) dataset is used to examine projected changes in temperature and precipitation over the United States (U.S.), Central America and the Caribbean. The changes are computed using an ensemble of 31 models for three future time slices (2021–2040, 2041–2060, and 2080–2099) relative to the reference...

This paper bypasses the mathematical technicalities of baroclinic instability and tries to provide a more conceptual, mechanistic explanation for a phenomenon that is fundamentally important to the dynamics of the earth’s atmosphere and oceans. The standard conceptual picture of baroclinic instability is reviewed and stripped down to identify the m...

The El Niño Southern Oscillation (ENSO) phenomenon is considered to be responsible for rainfall predictability in many regions. Some of its regional teleconnections, such as over the Arabian Peninsula in boreal summer (June–August) season, are not well studied. Therefore, in this paper, the relationship between the summer seasonal mean rainfall and...

A new version of the Community Land Model (CLM) was introduced to the Saudi King Abdulaziz University Atmospheric Global Climate Model (Saudi-KAU AGCM) for better land surface component representation, and so to enhance climate simulation. CLM replaced the original land surface model (LSM) in Saudi-KAU AGCM, with the aim of simulating more accurate...

A new coupled global climate model (CGCM) has been developed at the Center of Excellence for Climate Change Research (CECCR), King Abdulaziz University (KAU), known as Saudi-KAU CGCM. The main aim of the model development is to generate seasonal to subseasonal forecasting and long-term climate simulations. The Saudi-KAU CGCM currently includes two...

This study examines the effects of convective parameterization schemes (CPSs) on the simulated June-September (JJAS) precipitation climatology, variability and predictability over southwestern Arabian Peninsula and northeast Africa during 1981-2014 within an atmospheric global climate model framework. The three CPSs used are: the simplified Arakawa...

This chapter illustrates the benefit of using OpenMP parallelism in a more “coarse-grained” way. This requires inserting directives at the highest possible level in source code, and using domain decomposition concepts that are closely analogous to those of MPI, so that multiple copies of thread-local arrays do not lead to excessive memory consumpti...

Performance of a wind-forecasting system for a wind-farm in Ireland is reported. Forecasts were based on ensembles constructed from HARMONIE model runs every 6 hours, along with extra high-resolution HARMONIE runs every 12 hours. Statistical post-processing with Bayes Model Averaging (BMA) removed bias very effectively. The " raw " incremental skil...

Novel computing architectures like Xeon Phi Coprocessors and GPUs promise enhanced performance based on massively increased parallelism. However, they also have relatively limited memory and transferring data to them and back again is very slow. Currently these performance limitations, at least in the case of Xeon Phi, exceed the benefits for appli...

Wind-speed forecasts for a wind-farm in southwest Ireland were made for over one year using the operational HARMONIE mesoscale weather forecast model, and Bayes Model Averaging (BMA) for statistical post-processing to remove systematic local bias. The deterministic forecasts alone generated mean absolute errors of 1.7-2.0 ms-1 out to 24hrs, when in...

Two distinct elements seem to be required to make accurate wind-speed forecasts for wind-farms: the first is deterministic output from a weather forecast model, and the second is some probabilistic or statistical post-processing to account for local biases, or systematic errors in the model. A variety of statistical post-processing schemes are avai...

The set of hourly averaged condensation nuclei (CN) data collected at Mace Head during 1991-1994 was examined for relationships that might exist between CN number concentrations and the more commonly measured meteorological variables, including tides. CN number concentrations at Mace Head can be characterized by typically low ``background'' levels...

Two conceptual paradigms have been used in the past to interpret the observed strength and structure of eddy heat fluxes in the atmosphere. One is the idea of 'adjustment', whereby the eddies respond efficiently to changes in forcing to maintain the mean isentropic slope. The other is a 'diffusive' paradigm, which assumes that eddy fluxes can be pa...

The rate of change of total heat storage in the ocean is determined primarily by the net heat fluxes across the air-sea interface. In the context of a wind- and heat-driven ocean model the long-term mean heat budget was examined in a series of perturbation experiments in which atmospheric forcing parameters (surface winds and surface air temperatur...

Spatial patterns of mid-latitude large-scale ocean-atmosphere interaction on monthly to seasonal time scales have been observed to exhibit a similar structure in both the North Pacific and North Atlantic basins. These patterns have been interpreted as a generic oceanic response to surface wind anomalies, whereby the anomalous winds give rise to cor...

Spatial patterns of mid-latitude large-scale ocean-atmosphere interaction on monthly to seasonal time scales have been observed to exhibit a similar structure in both the North Pacific and North Atlantic basins. These patterns have been interpreted as a generic oceanic response to surface wind anomalies, whereby the anomalous winds give rise to cor...

Observational studies have revealed some coherent extratropical patterns associated with the tropical Madden-Julian (MJ) wave. This study is an attempt to clarify and constrain the interpretation of these patterns by investigating tropical-extratropical interactions on intraseasonal time scale in a global spectral model (GSM). Forcing representativ...

For equal values of the mean vertical shear, eddy fluxes and energies are greater when the shear is concentrated at lower levels (d2U/dz2 < 0) than when the shear is concentrated at higher levels (d2U/dz2 > 0). Eddy fluxes are more sensitive to lower-than to upper-level mean temperature gradients. This relative sensitivity is a function of [ggr] =...

A large class of wave structures in quasigeostrophic flow have instantaneous growth rates significantly larger than normal-mode growth rates. Since energy and potential enstrophy growth rates can be defined as functions of the perturbation structure, this structure can be varied in order to maximize the growth rates. Green's model is used as an ill...

This paper investigates the effect of topography on circulation produced by low-order quasi-geostrophic models that are capable of reproducing many basic features of midlatitude general circulation in the absence of topography. Using a simple two-level spectral model, time-mean stationary waves and low-frequency phenomena were examined for three di...

The ability of low-order, two-layer models to reproduce basic features of the mid-latitude general circulation is investigated. Changes in model behavior with increased spectral resolution are examined in detail. Qualitatively correct time-mean heat and momentum balances are achieved in a beta-plane channel model which includes the first and third...

The ability of low-order, two-layer models to reproduce basic features of the mid-latitude general circulation is investigated. Changes in model behavior with increased spectral resolution are examined in detail. Qualitatively correct time-mean heat and momentum balances are achieved in a β-plane channel model which includes the first and third mer...

ABSTRACTA low-order, two-level model in a beta-plane channel is integrated over long periods of time to study low-frequency mid-latitude variability. The model allows for nonlinear wave-wave and wave-mean flow interactions as well as zonally asymmetric forcing by topography. Time scales for the forcing and damping terms are varied, and, for closer...

Flow patterns are produced which are highly variable and seemingly chaotic, not suggestive of trajectories around multiple equilibria or distinct strong attractors in phase space. Analysis of the model integrations reveals the existence of low-frequency variability in the form of slowly-propagating Rossby waves, wave amplitude modulation and persis...

Minimal criteria are established which a numerical model of the atmosphere must meet in order to qualify as a "General Circulation Model". The ability of a class of low-order, two-layer, beta-plane channel models to meet these criteria is investigated. At least the first and third meridional modes are required in order to achieve qualitatively corr...

The response of midlatitude temperature structure to changes in radiative forcing is examined in an analytical energy-balance model that includes parameterized eddy heat fluxes and linear radiative heating. The characteristics of heat-transporting baroclinic waves are determined within the model, while simultaneously allowing the waves to adjust th...