West Pacific Research Articles

Systemic epigenome-wide association study of elk treponeme-associated hoof disease

Treponeme-associated hoof disease (TAHD) is an emerging disease of elk (Cervus canadensis) in the U.S. Pacific West. Because environmental epigenetics is the primary molecular process that mediates environmental factor impacts on a host organism and disease, the role of epigenetics in TAHD etiology was examined. The current study was designed to examine potential effects of TAHD on systemic epigenetic modifications in infected elk over a range of TAHD lesion severity. Leg tendons that contain predominantly fibroblast connective tissue cells were used to isolate fibroblast cells for epigenetic analysis in unaffected and TAHD-positive male and female Roosevelt and Rocky Mountain elk. Differential DNA methylation regions (DMRs) between the unaffected and TAHD-positive elk were identified for both female and male elk. The presence of TAHD was associated with alteration of the connective tissue cell epigenetics, and DMR associated genes identified. Therefore, the infected elk were found to have a systemic epigenetic alteration that was associated with the disease, despite pathology being generally limited to feet. If the elk germline epigenetics is altered then generational transmission of susceptibility to TAHD may impact subsequent generations through epigenetic inheritance. This first study of epigenetic changes associated with disease in elk suggests that TAHD promotes a systemic effect on the elk epigenetics which could exert health impacts on the elk.

РОЛЬ ИЗМЕНЕНИЙ АТМОСФЕРНОЙ ЦИРКУЛЯЦИИ В УВЕЛИЧЕНИИ ПОВТОРЯЕМОСТИ ЛЕТНИХ ЗАСУХ НА ЕВРОПЕЙСКОЙ ЧАСТИ РОССИИ

According to the Standardized Precipitation Evapotranspiration Index (SPEI), most extensive summer droughts in European Russia south of 55°N in 1950-2021 were observed during the extremely negative phases of the Eastern Atlantic/Western Russia (EAWR) and West Pacific (WP) atmospheric circulation patterns characterized by abnormal high atmospheric pressure and an increased frequency of the number of days with atmospheric blocking over European Russia. It is shown that the frequency of droughts in the study area in the years of the negative phases of both circulation indices and their extremes in the summer months as compared to other years was higher by five droughts per decade in the Volga and Central Chernozem regions and by three droughts per decade in the northwestern Caspian region. A statistically significant correlation was found between the EAWR in summer and the multidecadal variability of sea surface temperature in the North Atlantic. It was revealed that the increase in the drought frequency in the study area in recent decades has been caused by the restructuring of atmospheric circulation in the Euro-Atlantic sector accompanying the transition of the Atlantic Multidecadal Oscillation (AMO) to a positive phase. An increase in the stability of the EAWR and WP atmospheric circulation patterns was observed, as well as a related significant increase in the frequency of extensive droughts in the study area in 2010-2021. They were accompanied by the weakening of zonal atmospheric circulation in the Northern Hemisphere, the combination of the positive AMO phase and the effects of anthropogenic warming on the atmospheric circulation in the

Subseasonal Prediction of Regional Antarctic Sea Ice by a Deep Learning Model

AbstractAntarctic sea ice concentration (SIC) prediction at seasonal scale has been documented, but a gap remains at subseasonal scale (1–8 weeks) due to limited understanding of ice‐related physical mechanisms. To overcome this limitation, we developed a deep learning model named Sea Ice Prediction Network (SIPNet) that can predict SIC without the need to account for complex physical processes. Compared to mainstream dynamical models like European Centre for Medium‐Range Weather Forecasts, National Centers for Environmental Prediction, and Seamless System for Prediction and Earth System Research developed at Geophysical Fluid Dynamics Laboratory, as well as a relatively advanced statistical model like the linear Markov model, SIPNet outperforms them all, effectively filling the gap in subseasonal Antarctic SIC prediction capability. SIPNet results indicate that autumn SIC variability contributes the most to sea ice predictability, whereas spring contributes the least. In addition, the Weddell Sea displays the highest sea ice predictability, while predictability is low in the West Pacific. SIPNet can also capture the signal of ENSO and SAM on sea ice.

Influence of natural and anthropogenic aerosols on cloud base droplet size distributions in clouds over the South China Sea and West Pacific

Abstract. Cumulus clouds are common over maritime regions. They are important regulators of the global radiative energy budget and global hydrologic cycle, as well as a key contributor to the uncertainty in anthropogenic climate change projections due to uncertainty in aerosol–cloud interactions. These interactions are regionally specific owing to their strong influences on aerosol sources and meteorology. Here, our analysis focuses on the statistical properties of marine boundary layer (MBL) aerosol chemistry and the relationships of MBL aerosol to cumulus cloud properties just above cloud base as sampled in 2019 during the NASA Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex). The aerosol and clouds were sampled by instruments on the NASA P-3 aircraft over three distinct maritime regions around the Philippines: the West Pacific, the South China Sea, and the Sulu Sea. Our analysis shows three primary sources influenced the aerosol chemical composition: clean marine (ocean source), industrial (Southeast Asia, Manila, and cargo and tanker ship emissions), and biomass burning (Borneo and Indonesia). The clean marine aerosol chemical composition had low values of all sampled chemical signatures, specifically median values of 2.2 µg m−3 of organics (ORG), 2.3 µg m−3 of SO4, 0.3 µg m−3 of NO3, 1.4 µg m−3 of NH4, 0.04 µg m−3 of Cl, and 0.0074 µg m−3 of refractory black carbon (BC). Chemical signatures of the other two aerosol source regions were industrial, with elevated SO4 having a median value of 6.1 µg m−3, and biomass burning, with elevated median concentrations of ORG 21.2 µg m−3 and BC 0.1351 µg m−3. Based on chemical signatures, the industrial component was primarily from ship emissions, which were sampled within 60 km of ships and within projected ship plumes. Normalized cloud droplet size distributions in clouds sampled near the MBL passes of the P-3 showed that clouds impacted by industrial and biomass burning contained higher concentrations of cloud droplets, by as much as 1.5 orders of magnitude for diameters < 13 µm compared to clean marine clouds, while at size ranges between 13.0–34.5 µm the median concentrations of cloud droplets in all aerosol categories were nearly an order of magnitude less than the clean marine category. In the droplet size bins centered at diameters > 34.5 µm concentrations were equal to, or slightly exceeded, the concentrations of the clean marine clouds. These analyses show that anthropogenic aerosols generated from industrial and biomass burning sources significantly influenced cloud base microphysical structure in the Philippine region enhancing the small droplet concentration and reducing the concentration of mid-sized droplets.

Population genetic structure and mixed stock analysis of the green sea turtle, Chelonia mydas, reveal reproductive isolation in French Polynesia

The green turtle, Chelonia mydas, is a migratory marine species with a circumglobal distribution in tropical and temperate waters. Its natal homing behavior leads to a complex genetic structure with genetically differentiated populations that breed separately and mix within the same foraging grounds. Delineating the boundaries of these populations and their connectivity to feeding grounds is important for the management of this species, classified as endangered on the IUCN red list. Here, we examined the genetic structure and the origin of the green turtle in French Polynesia with 239 samples collected during nesting or hatchling events and 204 samples collected outside of nesting events, across 21 islands. Amplification of the 770pb mtDNA control region fragment, the standard base used to characterize haplotype diversity in this species, revealed 23 haplotypes including three novel ones, belonging to 6 different lineages. Haplotype diversity in the rookeries was 0.615, and nucleotide diversity was 0.019, values similar to those in the North West Pacific and Western Indian Oceans, two regions recognized as genetic diversity hotspots for C. mydas. The genetic structure between the Leeward and Windward Islands of the Society archipelago was found to be significant with pairwise Fst index and φst distance. Island groups (Windward Islands, Leeward Islands, Tuamotu) were genetically different from all other identified Pacific management units, with a weak differentiation between American Samoa and Leeward Islands. A mixed-stock analysis for the French Polynesian mixture revealed an exclusive contribution from the French Polynesian rookeries, with negligible input from the other Pacific populations. This study provides the first assessment of the genetic structure of green turtle populations within French Polynesia and fills an essential data gap regarding the genetic diversity of the species and its connectivity to other feeding grounds in the Pacific Ocean. The French Polynesian populations appear to be important contributors to the overall genetic diversity of the species, isolated from other Pacific populations, thus making them essential within the Pacific region. These results have important implications for the conservation of the species at both local and regional scales.

An Approach to Link Climate Model Tropical Cyclogenesis Bias to Large‐Scale Wind Circulation Modes

AbstractAttributing sources of tropical cyclogenesis (TCG) bias to large‐scale circulation in global circulation models is challenging. Here, we propose the use of empirical orthogonal functions as an approach to understand model bias of TCG. Two leading modes of large‐scale wind circulations in the West Pacific can explain the TCG frequency and location in both climate reanalysis and the MetUM model. In the reanalysis, the two modes distinguish the summer monsoon trough position and the strength of the north Pacific subtropical high. However, in the model, the wind circulations are biased toward the positive phase of simulated modes thus overestimating TCG in the entire Main Development Region. This bias is further related to the north‐eastward shifted monsoon trough and a weakened subtropical high, and overly strong tropics‐subtropics connections. This approach could be deployed more widely to other basins and models to diagnose the causes of TCG bias.

Decadal changes in the relationship between Arctic stratospheric ozone and sea surface temperatures in the North Pacific

Using multi-source observations and ERA-Interim reanalysis data, this study found that the relationship between Arctic stratospheric ozone in March and North Pacific sea surface temperature (SST) in April shows dramatic decadal changes, and it significantly weakens since the 2000s. By enhancing the stratospheric circulations, a decreased Arctic stratospheric ozone favors tropospheric positive Arctic Oscillation (+AO)-like anomaly during PRE eras (1979–1999), with positive geopotential height (GH) anomalies over high-latitude Asia. The stratospheric ozone anomaly also favors the Asian positive GH anomalies via modulating high cloud and its related longwave radiation. According to geostrophic wind relationships, the Asian positive GH anomalies are accompanied by easterly anomalies over midlatitude Asia in late March, which further extend eastward and thereby induce easterly anomalies over the midlatitude North Pacific. The North Pacific easterly anomalies result in negative North Pacific Oscillation (–NPO)-like anomaly via vorticity forcing of zonal wind and the interactions between synoptic-scale eddies and mean flow, forcing significant SST anomalies. However, during POST eras (2000–2019), firstly, the +AO-related positive GH anomalies over high-latitude Asia are relatively weak, accompanied by weak easterly anomalies over midlatitude Asia according to geostrophic wind relations, which induce weak easterly anomalies over the North Pacific. Secondly, a westerly anomaly occurs over the midlatitude North Pacific, which partly offsets the easterly anomalies from Asia, weakening the North Pacific easterly anomalies. The weak easterly anomalies further induce weak –NPO and SST anomalies during the POST eras. Our analysis further indicates that the North Pacific westerly anomalies and weakening of the positive GH anomalies over high-latitude Asia associated with ozone are related to the interference of the westerly phase of quasi-biennial oscillation and the weakened stratospheric ozone anomaly over high-latitude Asia, respectively.

Whole genome sequencing of Canadian Saccharomyces cerevisiae strains isolated from spontaneous wine fermentations reveals a new Pacific West Coast Wine clade.

Vineyards in wine regions around the world are reservoirs of yeast with oenological potential. Saccharomyces cerevisiae ferments grape sugars to ethanol and generates flavor and aroma compounds in wine. Wineries place a high-value on identifying yeast native to their region to develop a region-specific wine program. Commercial wine strains are genetically very similar due to a population bottleneck and in-breeding compared to the diversity of S. cerevisiae from the wild and other industrial processes. We have isolated and microsatellite-typed hundreds of S. cerevisiae strains from spontaneous fermentations of grapes from the Okanagan Valley wine region in British Columbia, Canada. We chose 75 S. cerevisiae strains, based on our microsatellite clustering data, for whole genome sequencing using Illumina paired-end reads. Phylogenetic analysis shows that British Columbian S. cerevisiae strains cluster into 4 clades: Wine/European, Transpacific Oak, Beer 1/Mixed Origin, and a new clade that we have designated as Pacific West Coast Wine. The Pacific West Coast Wine clade has high nucleotide diversity and shares genomic characteristics with wild North American oak strains but also has gene flow from Wine/European and Ecuadorian clades. We analyzed gene copy number variations to find evidence of domestication and found that strains in the Wine/European and Pacific West Coast Wine clades have gene copy number variation reflective of adaptations to the wine-making environment. The "wine circle/Region B", a cluster of 5 genes acquired by horizontal gene transfer into the genome of commercial wine strains is also present in the majority of the British Columbian strains in the Wine/European clade but in a minority of the Pacific West Coast Wine clade strains. Previous studies have shown that S. cerevisiae strains isolated from Mediterranean Oak trees may be the living ancestors of European wine yeast strains. This study is the first to isolate S. cerevisiae strains with genetic similarity to nonvineyard North American Oak strains from spontaneous wine fermentations.

The Impact of Tropical SST Biases on the S2S Precipitation Forecast Skill over the Contiguous United States in the UFS Global Coupled Model

Abstract This work investigates the impact of tropical sea surface temperature (SST) biases on the Subseasonal to Seasonal Prediction project (S2S) precipitation forecast skill over the contiguous United States (CONUS) in the Unified Forecast System (UFS) coupled model Prototype 6. Boreal summer (June–September) and winter (December–March) for 2011–18 were analyzed. The impact of tropical west Pacific (WP) and tropical North Atlantic (TNA) warm SST biases is evaluated using multivariate linear regression analysis. A warm SST bias over the WP influences the CONUS precipitation remotely through a Rossby wave train in both seasons. During boreal winter, a warm SST bias over the TNA partly affects the magnitude of the North Atlantic subtropical high (NASH)’s center, which in the reforecasts is weaker than in reanalysis. The weaker NASH favors an enhanced moisture transport from the Gulf of Mexico, leading to increased precipitation over the Southeast United States. Compared to reanalysis, during boreal summer, the NASH’s center is also weaker and in addition, its position is displaced to the northeast. The displacement further affects the CONUS summer precipitation. The SST biases over the two tropical regions and their impacts become stronger as the forecast lead increases from week 1 to 4. These tropical biases explain up to 10% of the CONUS precipitation biases on the S2S time scale.

Four new Solenogastres (Mollusca, Aplacophora) from the South China Sea and paraphyly of Proneomeniidae Simroth, 1893

Solenogastres and Caudofoveata (Aplacophora) remain some of the least known molluscs, despite ubiquity in the marine environment and importance in understanding molluscan evolution. The use of new morphological techniques and development of DNA barcode libraries have helped make specimen identification easier. However, for solenogasters, using histology for identification and adequate description of species remains necessary in most cases. This, together with the facts that knowledge about solenogaster species distributions is biased and that most species were described from one or very few individuals, explains why many open questions about the actual distribution, intra- and interspecific variability, etc., remain. We performed an integrative taxonomic study of eight specimens of solenogasters from the South China Sea (West Pacific Ocean) thatresulted in the identification of four new species of Proneomeniidae. Species identification and description following the established diagnostic characters were straightforward. However, phylogenetic analysis of molecular data obtained from these specimens and other members of Proneomeniidae indicate that the family is polyphyletic. We recovered representatives of two other families, Epimeniidae (Epimenia) and Strophomeniidae (Anamenia), nested within Proneomeniidae with strong support. Ancestral character state reconstruction indicates that characters commonly used in solenogaster taxonomy, such as the radula and foregut glands, may be more evolutionarily labile in this group than previously known. Therefore our work fills knowledge gaps regarding the diversity and distribution of members of this family but raises important questions about solenogaster taxonomy and systematics that should be further assessed with additional markers and broader taxon sampling. ZooBank: urn:lsid:zoobank.org:pub:BCADACD6-9AD0-442A-AD64-031BA8D88599

Late-stage structural evolution from near-bottom topographic and magnetic Surveys of Suda Seamount (West Pacific)

The late-stage evolution of seamounts is widespread in the West Pacific and may control the distribution of manganese nodules on the lower seamount flanks and adjacent debris aprons. However, due to the paucity of near-bottom observational data, little research exists specifically focused on the late-stage evolution of seamount structures. To fill this knowledge gap, we systematically investigated the tectonic features and evolution of Suda Seamount based on rock samples, satellite gravity data, and high-resolution magnetic and topographic data surveyed by Autonomous Underwater Vehicle (AUV). We found that the central area of the seamount summit exhibits a negative magnetic anomaly related to a group of minor volcanic structures, while the collapse of volcanic structures on the northeast seamount flank is associated with an extensive positive magnetic anomaly. Surprisingly, a late-stage intrusive dyke with significantly high magnetic susceptibility originates from the lower part of a minor group of volcanic structures but cannot be clearly distinguished below the main summit volcanic structure (hereinafter referred to as the main mound complex). These results demonstrate that at least two late-stage periods of intense magmatic activity occurred during the evolution of the seamount, one centered on the main mound complex and one on the margin of the summit platform. By combining fine-scale topographic and satellite gravity data, we deduce that gravitational slip caused by magma intrusion along a fracture was the main cause of the seamount flank collapse. The late-stage processes resulted in a change in the seamount morphology and distributed clastic rock debris widely along the flanks, which contributed to the uneven distribution of manganese nodules along the lower seamount flanks and determined the distribution of subsequently formed nodules.

Genetic diversity among sea snakes of the genus Hydrophis (Elapidae, Reptilia) in the Persian Gulf and Gulf of Oman.

Sea snakes of the genus Hydrophis are important components of animal diversity in Iranian waters of the Persian Gulf and Gulf of Oman. Ten species of Hydrophis have been identified from the these waters and, in this study, genetic structure of seven species was compared with other populations in the eastern Indian Ocean and the West Pacific. We found that six species (H.platurus, H.cyanocinctus, H.spiralis, H.schistosus, H.gracilis, and H.lapemiodes) show high genetic similarity with conspecific populations in the Indian Ocean and Australia. However, H.curtus from southern Iran shows a high level of genetic differentiation from conspecific populations in Sri Lanka and Indonesia (0.6% and 6% genetic distance from Sri Lankan samples for 16S and COI gene fragments, respectively). Variation between Iranian and Southeast Asian populations may reflect new genetic lineages and suggest the need of further morphological evaluations to re-evaluate their taxonomic position.

Influence of Multiple Interactions of Three Typhoons and a Mid-Latitude Cloud Band-Associated Trough in the North West Pacific upon Severe Tropical Storm Linfa

Multiple interactions of three typhoons and a mid-latitude cloud band-associated with a trough (MLCT) were investigated from 1 July to 10 July 2015, using the Korea Communication, Ocean, and Meteorological Satellite (COMS) satellite images and two kinds of meteorological models, such as UM-KMA (U.K.) and WRF-3.6 (U.S.A.), to generate the horizontal structure of wind and relative humidity, streamline, and moisture flux. As severe tropical storm (STS) Linfa moved toward the warmer area with a sea surface temperature (SST) of 31 °C in the northern South China Sea, it obtained not only more moisture by thermal convection of water vapor from the sea surface toward the lower atmosphere but also more momentum by its multiple interactions with both the MLCT and Typhoon (TY) Chan-Hom. Through their mutual interactions, mutual feedback of moisture and momentum fluxes could accelerate the formation of clouds in their systems and an asymmetric structure of their circulations. After Linfa weakened due to the increased friction of the shallower sea bottom close to the Chinese coast and its disconnection from the MLCT, later it became re-intensified with the increased wind speeds by a stronger interaction with more intensified TY Chan-Hom entering the path of the Kuroshio Current of SST 31 °C, which could supply additional moisture through thermal convection of water vapor into its system. Then, further interaction between the rapidly developed TY Nangka following behind and the MLCT enhanced the transfer of moisture and momentum fluxes from Chan-Hom into Linfa. Finally, after STS Linfa made landfall on the Chinese coast, it decayed into a weak low-pressure system before its dissipating, due to the weakening of its cyclonic circulation through the increased friction by the shallower sea bottom and the surrounding lands.

Genetic analyses reveal a non-panmictic genetic structure in the sablefishAnoplopoma fimbriain the northern Pacific

AbstractThe sablefish Anoplopoma fimbria is distributed on the continental shelf of the North Pacific, has a high commercial value for both fisheries and aquaculture, and represents a shared resource between countries in the North Pacific basin. In the present study, we extend the geographic range surveyed in previous studies and reexamine the population’s genetic structure by integrating phylogeographic patterns of mitochondrial DNA and microsatellite DNA markers. Our results contradict the proposal that sablefish constitute a single population throughout their distributional range. We observed a signal of ancient divergence in mtDNA that differentiates the North Pacific West Coast from the rest of the sample sites, and microsatellite markers reveal a contemporary isolation of Mexican sablefish. Our findings show genetic differences between localities that should be explored in more detail to fully understand the interconnectedness that appears to exist between populations.

Evidence of Distinct Genetic Stocks of the Bottlenose Wedgefish (Rhynchobatus australiae) in the Indo-West Pacific

Populations of the bottlenose wedgefish (Rhynchobatus australiae) in the Indo-West Pacific (IWP) have declined by nearly 80% in recent decades. In response, IWP countries are establishing sanctuaries to provide refuge for the fish. However, little is known about the genetic stock structure of the fish in the region. Hence, this study analysed partial sequences (610 base pairs) of the cytochrome oxidase subunit (COI) gene from eight bottlenose wedgefish populations in the IWP to assess the genetic stock structure of the fishery. The sequences revealed that Western Indian Ocean (WIO) populations are genetically distinct from those in the West Pacific (WP) (FCT = 0.24, p = 0.01) and Australia (FCT = 0.88, p = 0.01). Similarly, WP populations were genetically distinct from Australian populations (FCT = 0.42, p = 0.01). This suggests that the IWP contains three genetically distinct stocks of the bottlenose wedgefish: the WIO, WP, and Australia. The indices of genetic diversity and population size showed that the WIO stock has low genetic diversity and population size when compared to the WP and Australia. This shows that efforts to establish elasmobranch sanctuaries in the IWP should take into account the three identified stocks, with priority given to the WIO.
 Keywords: Restricted gene flow, genetic connectivity, elasmobranch sanctuaries, Indo-West Pacific Ocean

First observed dolphin fall in the South China sea: Implications for the biogeography

Cetacean falls provide a large amount of organic matter to the deep ocean, an otherwise oligotrophic environment. These events are now believed to maintain endemic species and offer intermediate habitats for species in other deep-sea ecosystems. Only about 70 modern whale falls have been reported in the world's oceans to date. We discovered the first known dolphin fall in the South China Sea in March 2020, on the middle slope of the Zhongnan seamount. We set up a camera at the site to observe animals visiting the dolphin carcass for 30 consecutive days from March 29 to April 28, 2020 and made four additional HOV dives to the dolphin carcass. In total, we observed 14 visible megafauna species visiting this dolphin fall, including six fish species, five crustacean species, two echinoderm species, and one mollusk species, of which most were scavengers or predators. This was the first record of many of these taxa in the deep South China Sea. Furthermore, two bone-eating worms were found in a piece of the dolphin bone. The worms are identified as new species in the genus Osedax based on DNA analysis. The findings of this work suggest that cetacean falls occur frequently in the South China Sea and help to fill a knowledge gap regarding the biodiversity of cetacean falls in the West Pacific.

Precursory atmospheric circulations with Rossby wave trains leading to Eurasian extreme cold events

AbstractThis work examines precursory atmospheric circulations with various wave trains contributing to extreme cold weather over central Eurasia in boreal winter from 1979 to 2019. By conducting extended empirical orthogonal function (EEOF) on the preceding propagation circulation fields 2 weeks before the onset of extreme cold event (ECE) cases, three types of ECEs with different disturbance origins are classified and analysed. Type 1 denotes the positive phase of EEOF mode 1, shows as negative phase of Arctic Oscillation‐like pattern. The outbreak of this type of ECE is affected by a wave train originating from Baffin Bay, where an anomalous anticylonic system persisted under a background of weakened westerlies over middle‐high latitudes. Type 2 is picked from positive phase of EEOF mode 2, manifests as a developing blocking system that forms over Scandinavia and shifts to the Barents area. It is found that the blocking system is mainly strengthened by the downstream dispersion process of wave packets that are generated at the northern exit area of the North Pacific westerly jet, where exist anomalous cyclonic zonal wind shear and precipitation. Type 3 is selected from the negative phase of EEOF mode 2, which has a similar origin to type 2 but with the North Pacific jet exit more southward. Then, the generated wave packets propagate to Europe along the northerly jet stream over the North Atlantic, which acts as a waveguide and extends the wave train to downstream. In a word, these three types of precursory atmospheric wave train patterns that bring extreme cold anomalies to Eurasia possess diverse disturbing sources and downstream development mechanisms, and the essential role of the westerly jet is further highlighted. The results, which are investigated based on a quasi‐biweekly time scale, may deepen our understanding of the atmospheric genesis of extreme weather and improve extended‐range weather forecast.

California and Hawai‘i Bound: U.S. Settler Colonialism and the Pacific West, 1848–1959

California and Hawai‘i Bound: U.S. Settler Colonialism and the Pacific West, 1848–1959

Enhancing Forecast Skill of Winter Temperature of East Asia Using Teleconnection Patterns Simulated by GloSea5 Seasonal Forecast Model

GloSea5, a seasonal forecast system of the UK Met Office, shows reasonable skill among state-of-the-art operational seasonal forecast systems. However, the average surface temperature (T2m) in winter (December–February) of GloSea5 is particularly low in East Asia. To improve the seasonal forecast skill over East Asia, we focused on the high skill score of global teleconnection patterns simulated by GloSea5. Among the well-predicted teleconnection patterns, we selected those highly correlated with the East Asian T2m: East Atlantic (EA), Polar/Eurasia (PE), East Atlantic/Western Russia (EAWR), and West Pacific (WP) patterns. A multiple linear regression model was constructed using the selected teleconnection indices as predictors. These results are promising. The statistical skill-score evaluation of the constructed linear regression model using the anomaly correlation coefficient (ACC), root mean squared error (RMSE), and mean-squared skill score (MSSS) showed an improvement in the predicted T2m of East Asia, where the values of ACC and MSSS increased by 0.25 and 0.37, respectively, and the RMSE decreased by 0.63 compared to the dynamic forecast model results. These results suggest that a well-designed combined statistical and dynamical approach for seasonal prediction can be beneficial for some regions where the predictability of the dynamic model exhibits a low value.

Dynamics and Impacts of the North Pacific Eddy-Driven Jet Response to Sudden Stratospheric Warmings

Abstract In this study, observations and simulations are used to investigate the mechanisms behind the different surface responses over the North Pacific and North Atlantic basins in response to sudden stratospheric warmings associated with a polar-night jet oscillation event (PJO SSWs). In reanalysis and a free-running preindustrial simulation, on average, a negative North Atlantic Oscillation (NAO) response is seen, corresponding to an equatorward shift of the eddy-driven jet. This is considered as the canonical tropospheric response to PJO SSWs. In contrast, the response over the North Pacific is muted. This basin-asymmetric response is shaped by the North Pacific air–sea interactions spun up by the tropospheric precursor to PJO SSWs, which prevent the Pacific eddy-driven jet from responding to the downward influence from the stratosphere. To isolate the downward influence from the sudden warming itself from any preconditioning of the troposphere that may have occurred prior to the warming, a nudging technique is used by which a reference PJO SSW is artificially imposed in a 195-member ensemble spun off from a control simulation. The nudged ensembles show a more basin-symmetric negative Northern Annular Mode (NAM) response, in which the eddy-driven jet shifts equatorward in both the Pacific and Atlantic sectors. Monitoring the atmospheric and oceanic conditions in the North Pacific before and at the onset of PJO SSWs may be useful for forecasting whether a basin-asymmetric negative NAO or basin-symmetric negative NAM response is more likely to emerge. This can be further used to improve subseasonal-to-seasonal predictions of weather and climate. Significance Statement Stratospheric sudden warming events (SSWs) occur when the eastward winds usually found above the Arctic in the winter spontaneously and rapidly reverse. Following their occurrence, the Northern Hemisphere surface westerlies move southward, sometimes over both the North Atlantic and North Pacific and other times over the North Atlantic only. We therefore wanted to understand this uncertainty in the North Pacific surface westerlies response. We find that the North Pacific surface westerlies response to SSWs can be muted by air–sea interactions over the North Pacific. Our results highlight the importance of monitoring the atmospheric and oceanic conditions in the North Pacific before the occurrence of SSWs to forecast whether the Pacific westerlies are likely to respond to SSWs.