Publications

This study investigated zonal SST gradients on the variability of subtropical high cells in both hemispheres and linked that variability to changes in tropical cyclone landfall frequency. Inter-basin SST gradients foster westward extensions of northern hemispheric subtropical high cells, leading to changes in landfall risk in the northern hemisphere. A localized SST dipole in the South Indian Ocean promotes a northwest expansion of the South Indian Ocean subtropical high, increasing tropical cyclone landfall risk.

Johnson et al. (2025)

This study examined how summertime synoptic circulations via the North American Monsoon impact streamflow in the Upper Colorado River basin through a k-means clustering analysis. An eastward or northward shift in the mid-tropospheric ridge of high pressure promotes increased precipitation, while a southward or northwestward shift leads to decreased precipitation over the basin. As a result, an eastward shift of the ridge favors increased streamflow, whereas a west or northwest shift in the ridge contributes to decreased streamflow. Summertime monsoon rains contribute ~17% of July-August streamflow variability, possibly linked to Pacific climate variability.

Johnson et al. (2024)

This study assessed how SST patterns influence the Western North Pacific subtropical high's westward extension, vital for seasonal predictions of tropical cyclones. Amidst different Pacific SST patterns, inter-basin SST gradients and intra-basin Pacific SST gradients dominate the westward extension. Complex and non-linear relationships between various oceanic regions result in variability on the western side of the North Pacific subtropical high.

Jones et al. (2024)

This study found that the frequency of explosive cyclones is strongly correlated with the North Atlantic Oscillation. It is also linked with an atmospheric wave train emanating from the North Pacific over the past 30 years. The wave train is associated with heightened upper-level divergence and Eady growth rates along the east coast of North America.

Stuivenvolt-Allen et al. (2023)

Seasonal prediction of tropical cyclone landfalls depends on the number and spatial distribution of genesis, but also whether those tropical cyclones are steered toward land or not. This study presented a practical statistical framework for estimating the seasonal count of landfalls as the product of a Poisson model for genesis and a logistic model for landfall probability.

Johnson et al. (2022)

Periods of water surplus and deficit in Northern California follow a pronounced quasi-decadal cycle. This cycle is largely driven by the frequency of atmospheric rivers (ARs), affecting the region’s wet and dry periods. This analysis demonstrated that the quasi-decadal cycle of AR frequency relies on moisture transport associated with the position and intensity of the Aleutian Low, which has a decadal frequency and covaries with tropical Pacific SST anomalies.

Stuivenvolt-Allen et al. (2021)

ENSO is known to exert a strong influence on the tropical Atlantic, yet the opposite pathway also exists: Atlantic forcing exerts an influence on ENSO. This study found that equatorial Atlantic cooling can trigger a weakening of tropical zonal winds in the Indo-Pacific sector and thereby activate the Bjerknes feedback in the tropical Pacific.

Chikamoto et al. (2020)

This study quantified Pacific Decadal Oscillation (PDO) variability through novel climate models. The PDO is primarily forced by regional air-sea interaction in the North Pacific and remote forcing from ENSO. Yet, Atlantic SSTs exert a significant impact on PDO variability through the reorganization of the global Walker circulation, subsequent ENSO development, then finally a teleconnection from the tropical to the North Pacific through Rossby wave propagation (equatorial process). Another pathway exists off the equator from AMO forcing (subtropical process).

Johnson et al. (2020)

Australian precipitation is highly influenced by the remote impact of SST variability, especially from the tropical Pacific. Yet, this study found a significant portion of Australian precipitation variability originates from the Atlantic Ocean through the modulation of the global Walker circulation. Observation and model evidence suggest that there may be a decadal component to Australian precipitation variability from Pacific and Atlantic origins. 

Johnson et al. (2018)

The dryline in the Great Plains has dependencies on soil moisture, a surrogate for evapotranspiration. This study found that when soil moisture was greater, the dryline was situated further west. When there is a strong east-west gradient of soil moisture, the specific humidity gradient of the dryline was greater. 

Johnson et al. (2018)