Ian White

Ian White
Tel Aviv University | TAU · Department of Physics and Astronomy

Doctor of Philosophy

About

43
Publications
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Publications

Publications (43)
Article
An idealised model is used to examine the tropospheric response to sudden stratospheric warmings (SSWs), by imposing transient stratospheric momentum torques tailored to mimic the wave-forcing impulse associated with spontaneously-occurring SSWs. Such an approach enables us to examine both the ∼2-3-week forcing stage of an SSW during which there is...
Article
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An intermediate complexity moist general circulation model is used to investigate the sensitivity of the quasi‐biennial oscillation (QBO) to resolution, diffusion, tropical tropospheric waves, and parameterized gravity waves. Finer horizontal resolution is shown to lead to a shorter period, while finer vertical resolution is shown to lead to a long...
Article
The Arctic is warming at a rate twice the global average and severe winter weather is reported to be increasing across many heavily populated mid-latitude regions, but there is no agreement on whether a physical link exists between the two phenomena. We use observational analysis to show that a lesser-known stratospheric polar vortex (SPV) disrupti...
Preprint
(This manuscript has been submitted to Journal of the Atmospheric Sciences) In order to isolate the immediate tropospheric response to a sudden stratospheric warming (SSW) from the tropospheric precursors that drive the SSW, an idealised model is used to decouple the two processes during the forcing and early-onset stage. Transient stratospheric m...
Article
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A moist General Circulation Model is used to investigate the forcing of the Asian monsoon and the associated upper level anticyclone by land‐sea contrast, net horizontal oceanic heat transport, and topography. The monsoonal pattern is not simply the linear additive sum of the response to each forcing; only when all three forcings are included simul...
Article
The connection between the polar stratospheric vortex and the vertical component of the Eliassen-Palm flux in the lower stratosphere and upper troposphere is examined in model level data from the ERA-5 reanalysis. The particular focus of this work is on the conditions that lead to upward wave propagation between the tropopause and the bottom of the...
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This work has been accepted for publication in JGR-Atmospheres and the corresponding DOI and publication information will be updated when available. -------------------------------------------------------------------------------------------------------------------------------------------- Although sudden stratospheric warmings (SSWs) can improve...
Article
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An intermediate complexity General Circulation Model is used to investigate the transient response of the NH winter stratosphere to modulated ultraviolet (UV) radiation by imposing a step-wise, deliberately exaggerated UV perturbation and analyzing the lagged response. Enhanced UV radiation is accompanied by an immediate warming of the tropical upp...
Preprint
Although sudden stratospheric warmings (SSWs) can improve subseasonal to seasonal forecasts, it is unknown whether the two types of SSW - displacements and splits - have different near-surface effects. To examine the longer-term(i.e., at multi-week leads) tropospheric response to displacements and splits, we utilise an intermediate-complexity model...
Article
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Plain Language Summary Projecting the weather on subseasonal and seasonal time scales is extremely difficult yet essential for certain applications. Forecasting skill on these time scales relies on features in the climate system that persist for longer than 2 weeks, and one such feature is the quasi‐biennial oscillation (QBO). Here, we use Earth sy...
Article
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Using 17 CMIP5/6 models with a spontaneously-generated quasi-biennial oscillation (QBO)-like phenomenon, this study explores and evaluates three dynamical pathways for impacts of the QBO on the troposphere: (i) the Holtan-Tan (HT) effect on the stratospheric polar vortex and the northern annular mode (NAM), (ii) the subtropical zonal wind downward...
Article
Climate models in the Coupled Model Intercomparison Project, Phase 5 (CMIP5) vary significantly in their ability to simulate the phase and amplitude of atmospheric stationary waves in the midlatitude Southern Hemisphere. These models also suffer from a double inter-tropical convergence zone (ITCZ), with excessive precipitation in the tropical easte...
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The response of the early winter Northern Hemisphere stratospheric polar vortex and tropospheric Arctic Oscillation to anomalous autumn snow cover in Eurasia is evaluated in four operational subseasonal forecasting models. Of these four models, the two with finer stratospheric resolution simulate a weakened vortex for hindcasts initialized with mor...
Article
Full-text available
A minor sudden stratospheric warming (SSW) happened in September 2019 in the Southern Hemisphere (SH) with winds at 10 hPa, 60°S reaching their minimum value on 18 September. Using multiple data sets and real‐time predictions from 11 subseasonal to seasonal (S2S) models, the evolution, favorable conditions, and predictability for this SSW event are...
Article
While rapid changes in Arctic climate over recent decades are widely documented, the importance of different driving mechanisms is still debated. A previous study proposed a causal connection between recent tropical Pacific sea surface temperature (SST) trends and circulation changes over northern Canada and Greenland (NCG). Here, using the HadGEM3...
Article
Full-text available
Using 16 CMIP5/6 models with a spontaneously-generated quasi-biennial oscillation (QBO)-like phenomenon, this study investigates the impact of the QBO on the northern winter stratosphere. Eight of the models simulate a QBO with a period similar to that observed (25-31 months), with other models simulating a QBO period of 20-40 months. Regardless of...
Article
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Using the real‐time predictions from 11 models, this study analyzes the prediction of the downward propagation and surface impact of the 2018 and 2019 sudden stratospheric warmings (SSWs). These two SSWs differed both in their morphology types (2018: split; 2019: displacement followed by split) and magnitudes (the former being stronger). With a lar...
Article
An intermediate complexity moist General Circulation Model is used to investigate the forcing of stationary waves in the Northern Hemisphere boreal winter by land-sea contrast, horizontal heat fluxes in the ocean, and topography. The additivity of the response to these building blocks is investigated. In the Pacific sector, the stationary wave patt...
Article
Full-text available
The tropospheric response to mid-winter sudden stratospheric warmings (SSWs) is examined using an idealised model. SSW events are triggered by imposing high-latitude stratospheric heating perturbations of varying magnitude for only a few days, spun-off from a free-running control integration (CTRL). The evolution of the thermally-triggered SSWs are...
Article
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Using multiple data sources, favorable conditions for the 2019 SSW event and its predictive skill from 11 sub-seasonal to seasonal (S2S) forecast models are explored in this study. This mixed-type (displacement to split) SSW event occurred under moderate El Niño, easterly quasi-biennial oscillation (QBO) together with solar minimum, and phases 4–6...
Article
Full-text available
The Arctic stratospheric response to El Niño (EN) and La Niña (LN) is evaluated in a 41 member ensemble of the period 1980 to 2009 in the Goddard Earth Observing System Chemistry-Climate Model. We consider whether the responses to EN and LN are equal in magnitude and opposite in sign, whether the responses to moderate and extreme events are proport...
Preprint
Recently submitted to the Journal of Climate. Abstract: The tropospheric response to midwinter sudden stratospheric warmings (SSWs) is examined using an idealised model. SSW events are triggered by imposing high-latitude stratospheric heating perturbations of varying magnitude for only a few days, spun-off from a free-running control integration (...
Article
Full-text available
While a connection between the El Niño–Southern Oscillation (ENSO) and the Northern Hemisphere wintertime stratospheric polar vortex appears robust in observational studies focusing on the period before 1979 and in many modeling studies, this connection is not evident over the past few decades. In this study, the factors that have led to the disapp...
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The prominence of nonlinearities in the response to El Niño as compared to La Niña, to moderate El Niño events as compared to extreme El Ninño events, and to different flavors of El Niño events, are analyzed using the NASA Goddard Earth Observing System Chemistry-Climate Model. In the Central North Pacific region where the sea level pressure respon...
Preprint
Full-text available
Tropospheric features preceding sudden stratospheric warming events (SSWs) are identified using a large compendium of events obtained from a chemistry-climate model. In agreement with recent observational studies, it is found that approximately one-third of SSWs are preceded by extreme episodes of wave activity in the lower troposphere. The relatio...
Article
The effect of the Quasi-Biennial Oscillation (QBO) on the Northern Hemisphere wintertime stratospheric polar vortex is evaluated in five operational subseasonal forecasting models. Of these five models, the three with the best stratospheric resolution all indicate a weakened vortex during the easterly phase of the QBO relative to its westerly phase...
Article
Full-text available
Breaking planetary waves (BPWs) affect stratospheric dynamics by reshaping the waveguides, causing internal wave reflection and preconditioning sudden stratospheric warmings. This study examines observed changes in BPWs during the northern winter due to enhanced solar forcing and the consequent effect on the seasonal development of the polar vortex...
Article
Full-text available
Breaking planetary waves (BPWs) affect stratospheric dynamics by reshaping the waveguides, causing internal wave reflection, and preconditioning sudden stratospheric warmings. This study examines observed changes in BPWs during the northern winter resulting from enhanced solar forcing and the consequent effect on the seasonal development of the pol...
Article
Diagnostics of wave-mean-flow and wave-wave interactions in isentropic coordinates are analysed regarding the mechanisms that govern the Holton-Tan Effect (HTE), whereby the tropical quasi-biennial oscillation (QBO) modulates the northern-winter stratospheric polar vortex. We find a clear seasonal evolution of a QBO modulation of Rossby waves and l...
Article
Full-text available
Since the 1950s, research stations on the Antarctic Peninsula have recorded some of the largest increases in near-surface air temperature in the Southern Hemisphere. This warming has contributed to the regional retreat of glaciers, disintegration of floating ice shelves and a 'greening' through the expansion in range of various flora. Several inter...
Article
Full-text available
Wave-mean-flow interactions associated with the Holton-Tan effect (HTE), whereby the tropical quasi-biennial oscillation (QBO) modulates the Northern-Hemisphere wintertime stratospheric polar vortex, are studied using the ERA-Interim reanalysis dataset. Significant evidence of the HTE in isentropic coordinates is found, with a weaker and warmer pol...