Atmospheric Response to SST Anomalies. Part II: Background-State Dependence, Teleconnections, and Local Effects in Summer

Thomson, Stephen I.; Vallis, Geoffrey K.

doi:10.1175/jas-d-17-0298.1

Cited by 21 publications

(37 citation statements)

References 34 publications

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“…We focus on the cold season because this is when tropical-to-polar teleconnections are most active (e.g., Lee et al, 2009;Thomson & Vallis, 2018a, 2018b. We focus on the cold season because this is when tropical-to-polar teleconnections are most active (e.g., Lee et al, 2009;Thomson & Vallis, 2018a, 2018b.…”

Section: Physical Mechanismsmentioning

confidence: 99%

“…The year-0 IPO is also associated with subsequent trends in the cold season (October-March) atmospheric circulation. We focus on the cold season because this is when tropical-to-polar teleconnections are most active (e.g., Lee et al, 2009;Thomson & Vallis, 2018a, 2018b. Negative year-0 IPO is linked to subsequent decreasing mean sea level pressure trends in the North Pacific (Figure 2e), reflecting a strengthening of the AL.…”

Section: Physical Mechanismsmentioning

confidence: 99%

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Pacific Ocean Variability Influences the Time of Emergence of a Seasonally Ice‐Free Arctic Ocean

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Deser

2019

Geophysical Research Letters

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The Arctic Ocean is projected to become seasonally ice‐free before midcentury unless greenhouse gas emissions are rapidly reduced, but exactly when this could occur depends considerably on internal climate variability. Here we show that trajectories to an ice‐free Arctic are modulated by concomitant shifts in the Interdecadal Pacific Oscillation (IPO). Trajectories starting in the negative IPO phase become ice‐free 7 years sooner than those starting in the positive IPO phase. Trajectories starting in the negative IPO phase subsequently transition toward the positive IPO phase, on average, with an associated strengthening of the Aleutian Low, increased poleward energy transport, and faster sea‐ice loss. The observed IPO began to transition away from its negative phase in the past few years. If this shift continues, our results suggest increased likelihood of accelerated sea‐ice loss over the coming decades, and an increased risk of an ice‐free Arctic within the next 20–30 years.

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Section: Physical Mechanismsmentioning

confidence: 99%

Section: Physical Mechanismsmentioning

confidence: 99%

Pacific Ocean Variability Influences the Time of Emergence of a Seasonally Ice‐Free Arctic Ocean

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Deser

2019

Geophysical Research Letters

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“…Various models of Earth's atmosphere have been constructed using Isca and are described in more detail elsewhere (e.g., [11,[28][29][30][31]). Here, we give three examples covering the range of possibilities.…”

Section: Earthmentioning

confidence: 99%

Hierarchical Modeling of Solar System Planets with Isca

Thomson

Vallis

2019

Atmosphere

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We describe the use of Isca for the hierarchical modeling of Solar System planets, with particular attention paid to Earth, Mars, and Jupiter. Isca is a modeling framework for the construction and use of models of planetary atmospheres at varying degrees of complexity, from featureless model planets with an atmosphere forced by a thermal relaxation back to a specified temperature, through aquaplanets with no continents (or no ocean) with a simple radiation scheme, to near-comprehensive models with a multi-band radiation scheme, a convection scheme, and configurable continents and topography. By a judicious choice of parameters and parameterization schemes, the model may be configured for fairly arbitrary planets, with stellar radiation input determined by astronomical parameters, taking into account the planet's obliquity and eccentricity. In this paper, we describe the construction and use of models at varying levels of complexity for Earth, Mars and Jupiter using the primitive equations and/or the shallow water equations.Atmosphere 2019, 10, 803 2 of 21 with a nominal troposphere that in some respects is quite Earth-like: its temperature falls from about 320 K at its base to 53 K at its top, possibly containing both water and ammonia/methane clouds.Beyond our Solar System, there are likely billions of planets in our galaxy alone, with over 4000 confirmed planets at the time of writing (NASA Exoplanet Archive [7]). Many of these planets are undoubtedly similar to those mentioned above, but some surely different-tidally-locked "Hot-Jupiters", being but one example class [8,9].Given such a diversity-a diversity far greater than that of the stars around which the planets orbit-the question arises as to how such planets should be modeled. On Earth, we may reasonably seek to model Earth's atmosphere and climate in some detail using very complex models-such as comprehensive General Circulation Models (GCMs) or Earth System Models (ESMs)-in which we seek to put the most realistic representation of physical and chemical (and sometimes biological) processes possible. Such models are extensions of those used for weather forecasting and, similar to weather forecast models, one goal is to be as quantitatively accurate as possible.However, several factors suggest that such an approach is not always ideal for planetary atmospheres:

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“…The ocean is the most important source of long-term memory that interacts with the atmosphere (Frankignoul 1985;Kushnir et al 2002;Kaspi and Schneider 2011;Putrasahan et al 2013;Thomson and Vallis 2018). The atmospheric response to SST anomalies (SSTA) in the tropics is more direct and local, i.e.…”

Section: Introductionmentioning

confidence: 99%

Subseasonal Statistical Forecasts of Eastern U.S. Hot Temperature Events

Vijverberg

Schmeits

Wiel

et al. 2020

Monthly Weather Review

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Extreme summer temperatures can cause severe societal impacts. Early warnings can aid societal preparedness, but reliable forecasts for extreme temperatures at subseasonal-to-seasonal (S2S) timescales are still missing. Earlier work showed that specific sea surface temperature (SST) patterns over the northern Pacific are precursors of high temperature events in the eastern United States, which might provide skillful forecasts at long-leads (~50 days). However, the verification was based on a single skill metric and a probabilistic forecast was missing. Here, we introduce a novel algorithm that objectively extracts robust precursors from SST linked to a binary target variable. When applied to reanalysis (ERA-5) and climate model data (EC-Earth), we identify robust precursors with the clearest links over the North-Pacific. Different precursors are tested as input for a statistical model to forecast high temperature events. Using multiple skill metrics for verification, we show that daily high temperature events have no predictive skill at long leads. By systematically testing the influence of temporal and spatial aggregation, we find that noise in the target timeseries is an important bottleneck for predicting extreme events on S2S timescales. We show that skill can be increased by a combination of (1) aggregating spatially and/or temporally, (2) lowering the threshold of the target events to increase the base-rate, or (3) add additional variables containing predictive information (soil-moisture). Exploiting these skill-enhancing factors, we obtain forecast skill for moderate heatwaves (i.e. 2 or more hot days closely clustered together in time) up to 50 days lead-time.

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Atmospheric Response to SST Anomalies. Part II: Background-State Dependence, Teleconnections, and Local Effects in Summer

Cited by 21 publications

References 34 publications

Pacific Ocean Variability Influences the Time of Emergence of a Seasonally Ice‐Free Arctic Ocean

Pacific Ocean Variability Influences the Time of Emergence of a Seasonally Ice‐Free Arctic Ocean

Hierarchical Modeling of Solar System Planets with Isca

Subseasonal Statistical Forecasts of Eastern U.S. Hot Temperature Events

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