Eastern Pacific Sea Surface Temperature Research Articles

The initial errors occurring over Pacific-Atlantic Oceans and exerting large disturbing effect on ENSO predictability

Using a novel data analysis method for predictability dynamics, the impacts of initial sea surface temperature (SST) errors over Pacific and Atlantic Oceans on the predictability of eastern and central Pacific El Niño (i.e., EP and CP El Niño) are investigated. The results reveal the initial SST errors that cause large disturbing effects on EP and CP El Niño forecasting, respectively. These initial errors are both exhibiting a positive-negative-positive-negative-positive chain structure along the direction from northwest to southeast over the Pacific for EP and CP El Niño, which resemble a combined mode of North Pacific Victoria Mode (VM), eastern tropical Pacific positive SST pattern (ETPPSP), and South Pacific meridional mode (SPMM); simultaneously, they exhibit a positive-negative meridional dipole pattern over South Atlantic, referred to as South Atlantic subtropical dipole mode (SASD); additionally, there exist initial warm SST anomalies in the equatorial Atlantic for EP El Niño and in the north tropical Atlantic for the CP El Niño. The above initial errors lead to the underestimation of both CP and EP El Niño. Further analyses illustrate that the initial warm SST errors in the north tropical Atlantic are positively correlated with the VM-like error pattern, which competed with the effect of the ETPPSP, makes the intensity of CP El Niño underestimated; whereas the SASD-like error pattern is revealed to have a positive relationship with the SPMM-like error mode, which only exists during EP El Niño period and interacts with the ETPPSP for much weak EP El Niño intensity. It is obvious that, for predicting which type of El Niño will occur, attention should also be paid to the initial sea temperature accuracy in the Atlantic Ocean under the interference effect of the Pacific Ocean temperature uncertainties.

A SST-constructed Ocean Heat Content index in crossing ENSO spring persistence barrier

The El Niño-Southern Oscillation (ENSO) spring persistence barrier (SPB) describes the feature in which the predictive skills of ENSO decrease significantly in the boreal spring. This paper investigates an index constructed using sea surface temperature (SST), namely SSTH, which is based on tropical Pacific Ocean Heat Content (OHC) in crossing ENSO SPB. Inspired by the dynamical relationship between the tropical Pacific OHC and eastern Pacific SST anomalies, SSTH is constructed by SST anomalies (i.e., Niño3.4 index) to represent OHC. We show that this index leads ENSO SST anomalies by about 10 months, making it effective in crossing ENSO SPB. Particularly, among the 50 ENSO events from 1950 to 2022, 27 years were identified to be caused by SSTH signals. Compared with warm water volume (WWV) or the west of WWV (WWVw), this index is more stable and effective after the 21st century because the effective region of subsurface OHC changed dramatically afterward. However, SSTH avoids this problem as it is constructed by SST anomalies alone. Finally, as SST data is reliable before 1980, SSTH is utilized to study the interdecadal lead-lag relationship between subsurface OHC and ENSO SST.

A Zonal See‐Saw Variation of Tropical Cyclogenesis Over the Arabian Sea and Bay of Bengal‐South China Sea

AbstractThe variation of tropical cyclone (TC) genesis over the North Indian Ocean (NIO) and South China Sea (SCS) during the post‐monsoon season is explored during 1979–2020. A zonal see‐saw variation of TC genesis is detected between the Arabian Sea (AS) and Bay of Bengal (BOB) –SCS (BOBSCS for brevity). More (less) TCs over the AS tend to concur with fewer (more) TCs over the BOBSCS. Analyses of both the observations and the Coupled Model Intercomparison Project Phase 6 outputs show that tripole sea surface temperature (SST) anomalies in the tropical Indian and Pacific Oceans play a crucial role in the zonal see‐saw variation of TC genesis. Positive western Indian (WI) Ocean and tropical central and eastern Pacific (CEP) Ocean SST anomalies and negative western Pacific (WP) SST anomalies induce anomalous ascending and descending motions and high and low humidity transportation to the middle troposphere over the AS and BOBSCS, respectively. Meantime, anticyclonic vorticity anomalies appear in the BOBSCS region and negative anomalies of vertical wind shear are induced over the NIO and SCS. The combined positive contributions of upward motion, mid‐level humidity increase, and low vertical wind shear favor higher TC genesis over the AS, whereas the joint negative effects of downward motion, mid‐level water vapor decrease, and lower‐level anticyclonic vorticity anomalies result in less TC genesis over the BOBSCS. Numerical experiments show a critical role of the WI SST anomalies in the dipole pattern of vertical motion, which is crucial for the zonal dipole variation of TC genesis.

ENSO skewness hysteresis and associated changes in strong El Niño under a CO2 removal scenario

El Niño-Southern Oscillation (ENSO) sea surface temperature (SST) anomaly skewness encapsulates the nonlinear processes of strong ENSO events and affects future climate projections. Yet, its response to CO2 forcing remains not well understood. Here, we find ENSO skewness hysteresis in a large ensemble CO2 removal simulation. The positive SST skewness in the central-to-eastern tropical Pacific gradually weakens (most pronounced near the dateline) in response to increasing CO2, but weakens even further once CO2 is ramped down. Further analyses reveal that hysteresis of the Intertropical Convergence Zone migration leads to more active and farther eastward-located strong eastern Pacific El Niño events, thus decreasing central Pacific ENSO skewness by reducing the amplitude of the central Pacific positive SST anomalies and increasing the scaling effect of the eastern Pacific skewness denominator, i.e., ENSO intensity, respectively. The reduction of eastern Pacific El Niño maximum intensity, which is constrained by the SST zonal gradient of the projected background El Niño-like warming pattern, also contributes to a reduction of eastern Pacific SST skewness around the CO2 peak phase. This study highlights the divergent responses of different strong El Niño regimes in response to climate change.

Hysteresis of the El Niño-Southern Oscillation to CO2 forcing.

El Niño-Southern Oscillation (ENSO) is the strongest interannual climate variability with far-reaching socioeconomic consequences. Many studies have investigated ENSO-projected changes under future greenhouse warming, but its responses to plausible mitigation behaviors remain unknown. We show that ENSO sea surface temperature (SST) variability and associated global teleconnection patterns exhibit strong hysteretic responses to carbon dioxide (CO2) reduction based on the 28-member ensemble simulations of the CESM1.2 model under an idealized CO2 ramp-up and ramp-down scenario. There is a substantial increase in the ensemble-averaged eastern Pacific SST anomaly variance during the ramp-down period compared to the ramp-up period. Such ENSO hysteresis is mainly attributed to the hysteretic response of the tropical Pacific Intertropical Convergence Zone meridional position to CO2 removal and is further supported by several selected single-member Coupled Model Intercomparison Project Phase 6 (CMIP6) model simulations. The presence of ENSO hysteresis leads to its amplified and prolonged impact in a warming climate, depending on the details of future mitigation pathways.

Modulation of the Central Pacific El Niño on the Relationship Between the Hadley Circulation and Tropical SST

AbstractBased on observational data, the effects of Central Pacific (CP) El Niño events on the relationship between the Hadley circulation (HC) and tropical sea surface temperature (SST) under different meridional structures are investigated. The variability of HC and SST have been decomposed into equatorially symmetric and asymmetric components to detect their relationship. The explained variances of the equatorially asymmetric and symmetric components of the HC's principal modes both decreased in the CP El Niño events. Compared to climatology, the responses of HC to SST under different meridional structures are suppressed during CP El Niño events. It has been discovered that SST variations in the tropical eastern Pacific (EP) are responsible for the different response of HC to tropical SST. The EP SST anomalies exhibit inhomogeneous variations during CP El Niño events, with a greater amplitude in the north EP, resulting in enhanced variation of the equatorially asymmetric SST. The modulation of the CP El Niño on the relationship between the HC and tropical SST provides evidence for its complex climate effects.

Decadal variations of Pacific Walker circulation tied to tropical Atlantic–Pacific trans-basin SST gradients

During the modern satellite-monitoring era since ∼1979, the observed Pacific Walker circulation (PWC) presented a pronounced strengthening and robust westward-shifting, defying the model-projected weakening response to anthropogenic warming. The exact cause for the PWC decadal intensification and the corresponding observation-model disagreement remains indecisive. Using two targeted experiments wherein sea surface temperature (SST) anomalies in the tropical eastern Pacific and North Atlantic are separately restored to follow the observed history, we reveal that the North Atlantic-only SST warming and the tropical eastern Pacific-only SST cooling contribute partly to the PWC decadal adjustment. The North Atlantic SST warming triggers a significant westward displacement of PWC, while the tropical eastern Pacific SST cooling drives mainly the associated shifts of the large-scale atmospheric surface pressure centers. Further, we identify that the tropical Atlantic–eastern Pacific trans-basin SST gradients have dominated the PWC decadal variations over the past century. Our results highlight that a reliable representation of the simulated inter-basin warming contrast between the tropical Atlantic and the tropical eastern Pacific SSTs may be influential in correcting future projections of the PWC strength.

A Novel Mechanism for Extreme El Niño Events: Interactions between Tropical Cyclones in the Western North Pacific and Sea Surface Warming in the Eastern Tropical Pacific

Abstract This study presents a novel mechanism for the generation of extreme El Niño events by analyzing interactions between tropical cyclones (TCs) in the western North Pacific (WNP) in spring [March–May (MAM)] and summer [June–August (JJA)] and sea surface warming in the eastern tropical Pacific. It is suggested that anomalously strong TCs in the WNP in MAM and JJA are essential for the formation of extreme El Niño events. MAM TCs excite considerable westerly wind bursts (WWBs) and facilitate the generation of El Niño events in late spring. The sea surface temperature (SST) in the central-eastern tropical Pacific increases prominently during the following summer, which is due to the warm water carried by downwelling Kelvin waves induced by the anomalous westerlies in the western tropical Pacific associated with the WNP TCs, as well as the lessening cold water upwelling resulting from the deepening thermocline in the eastern tropical Pacific. The developing El Niño in turn contributes to the TC activities over the southeastern quadrant of the WNP in summer, characterized by a stronger intensity, higher frequency, and longer duration. The resulting JJA TC-induced westerlies could further enhance the eastern tropical Pacific warm SST anomalies, and thus an extreme El Niño event tends to appear in the following autumn and winter. These physical processes are verified by several sets of atmosphere–ocean coupled model experiments. Significance Statement Tropical cyclone activity is one of the most destructive phenomena in the world. Extreme El Niño events can also cause devastating climate disasters. Understanding the relationship between these two events can help with disaster forecasting and prevention. This study finds that TC activity in the western North Pacific contributes to the appearance of extreme El Niño events. Abnormally active TC activity in spring can cause strong near-equatorial westerly wind anomalies, eastward transport of warm water from the western tropical Pacific, and a deepening ocean thermocline in the east, resulting in the earlier onset of El Niño events. Influenced by the El Niño event, the TC activity in summer is strengthened, which in turn continues to promote the surface warming of the central-eastern tropical Pacific, eventually resulting in extreme event occurrence.

Geographical Distribution Variations of Humboldt Squid Habitat in the Eastern Pacific Ocean

The Humboldt squid Dosidicus gigas is a pelagic cephalopod species extensively distributed in the Eastern Pacific Ocean. Geographically separated habitat patterns of D. gigas show large spatiotemporal variations due to the distinct different regional environmental conditions. This study explored geographical variation in seasonal habitat of D. gigas off Peru and the Eastern Pacific Equator using maximum entropy (Maxent) model, with fishing occurrence data and environmental variables including sea surface temperature (SST), sea surface salinity, net primary production (NPP), photosynthetically active radiation (PAR), chlorophyll a concentration, eddy kinetic energy, and sea level anomaly. Results indicated that all the environmental variables exhibited conspicuous seasonal and geographical differences off Peru and the Eastern Pacific Equator. On the basis of the percent contribution from the Maxent model, seasonal and spatial extents of habitat were largely explained by SST, NPP, PAR, and eddy kinetic energy in the Eastern Pacific Equator and SST, sea surface salinity, NPP, and PAR off Peru. Suitable ranges of each environmental variable differed between regions and were controlled by the seasonal variability. Furthermore, movement patterns of longitudinal and latitudinal gravity centers of fishing effort of D. gigas were consistent with spatial and temporal distribution of suitable habitats but showed dramatically geographical variations off Peru and the Eastern Pacific Equator. Our findings highlighted Maxent mode’s ability in exploring Humboldt squid habitat hotspots in the Eastern Pacific Ocean and suggested that constructing the habitat model for D. gigas should consider the geographical differences under environmental conditions.

Diversity of Northwest Pacific atmospheric circulation anomalies during post-ENSO summer

In present study, the diversity of summertime Northwest Pacific (NWP) atmospheric circulation anomalies following El Niño-Southern Oscillation is investigated by performing the inter-case empirical orthogonal function (EOF) analysis among 33 El Niño cases and 36 La Niña cases, respectively. Although an anomalous anticyclone is observed over the NWP for all El Niño cases’ composite, the circulation anomalies there vary from one case to another for each case. The EOF1 mode of NWP circulation anomalies explains 39.8% of inter-case variance, and its positive phase features an anomalous anticyclone and cyclone at south and north of 25°N, respectively. Therefore, the positive first principal component (PC1) corresponds to the anomalous NWP anticyclone, while the anticyclone shifts more northeastward and a cyclone appears at its south side for negative PC1. The PC1-related NWP circulation anomalies are largely controlled by the pronounced central and eastern Pacific sea surface temperature cooling, which indicates the diverse El Niño decay rate. Furthermore, four categories are obtained according to the El Niño decay rate by the nonlinear k-means cluster analysis, and the results further confirm that the close relationship between NWP circulation anomalies and El Niño decay rate. The PC1-regressed land rainfall anomalies highly resembles the composite results in the key areas of Asian monsoon region: the central China and South Asia, indicating variable rainfall anomalies in these areas during post-El Niño summer. The conclusion obtained from La Niña cases are generally same to El Niño.

The Relationship between Northeast Pacific Sea Surface Temperatures, Synoptic Evolution, and Surface Air Temperatures over the Pacific Northwest

Abstract The development of sea surface temperature (SST) anomalies over the northeast Pacific and their impacts on lower-tropospheric air temperatures over the Pacific Northwest are examined. Northeast Pacific SST anomalies are influenced by the synoptic-scale flow, with high pressure and weak surface winds associated with developing warm SST anomalies, while large pressure gradients and strong surface winds result in SST declines. SST over the northeast Pacific correlates significantly with surface air temperatures over the Pacific Northwest, with correlations increasing when high-frequency variability is filtered out. The correlations between unfiltered time series of SST and surface air temperature are largest for a zero-day lag and are strongest near the coast, contrasting with weaker correlations over the Columbia basin east of the Cascade Mountains. SST correlations with minimum surface air temperature are largest during the warm season, and maximum temperature correlations are highest in March; both have low correlations during autumn. Model simulations of periods with warm and cold northeast Pacific SST anomalies possess lower-tropospheric air temperature warming or cooling over the coastal zone, with SST influence weakening east of the Cascade crest. Eastern Pacific SST anomalies influence sea level pressure and lower-tropospheric heights, with warm SST anomalies resulting in simulated lowered pressure near the surface and increased heights aloft. The relationship between northeast Pacific SST and surface air temperature over land evince complex feedbacks: SST temperature anomalies can be advected inland from the Pacific, the SST anomalies can influence the synoptic-scale flow that affects the SST anomalies, and the synoptic-scale anomalies that produce the SST anomalies can directly influence temperatures over land. Significance Statement Understanding the connection between northeast Pacific sea surface temperatures and low-level air temperatures over land is valuable for both subseasonal prediction and for examining the fidelity of model physics.

Asymmetries in the ENSO phase space

El Niño Southern Oscillation (ENSO) dynamics are best described by the recharge oscillator model, in which the eastern tropical Pacific sea surface temperatures (T) and subsurface heat content (thermocline depth; h) have an out-of-phase relationship. This defines a 2-dimensional phase space diagram between T and h. In an idealized, stochastically forced damped oscillator, the mean phase space diagram should be a perfectly symmetrical circle with a clockwise propagation over time. However, the observed phase space shows strong asymmetries. In this study we illustrate how the ENSO phase space can be used to discuss the phase-dependency of ENSO dynamics. A normalized spherical coordinate system allows the definition of phase-depending ENSO growth rates and phase transition speeds. Based on these we discuss the implications of the observed asymmetries with regards to the dynamics and predictability of ENSO; with a particular focus on the variations in the growth rate and coupling of ENSO along the oscillation cycle. Using linear and non-linear recharge oscillator models we will show how dynamics and noise are driving ENSO at different phases of the ENSO cycles. The results illustrate that the ENSO cycle with positive phase transitions is present in all phases but has strong variations in its strength. Much of these variations result from presenting the ENSO phase space with estimates of h based on the iso-thermal depth, that is not ideal as it is not out-of-phase with T. Future work should address how h can be estimated better, including aspects such as the vertical temperature gradients and the meridional or zonal range. We further illustrated that a non-linear growth rate of T can explain most of the observed non-linear phase space characteristics.

The Role of Seasonality and the ENSO Mode in Central and East Pacific ENSO Growth and Evolution

Abstract A cyclostationary linear inverse model (CSLIM) is used to investigate the seasonal growth of tropical Pacific Ocean El Niño–Southern Oscillation (ENSO) events with canonical, central Pacific (CP), or eastern Pacific (EP) sea surface temperature (SST) characteristics. Analysis shows that all types of ENSO events experience maximum growth toward final states occurring in November and December. ENSO events with EP characteristics also experience growth into May and June, but CP events do not. A single dominant “ENSO mode,” growing from an equatorial heat content anomaly into a characteristic ENSO-type SST pattern in about 9 months (consistent with the delayed/recharge oscillator model of ENSO), is essential for the predictable development of all ENSO events. Notably, its seasonality is responsible for the late-calendar-year maximum in ENSO amplification. However, this ENSO mode alone does not capture the observed growth and evolution of diverse ENSO events, which additionally involve the seasonal evolution of other nonorthogonal Floquet modes. EP event growth occurs when the ENSO mode is initially “covered up” in combination with other Floquet modes. The ENSO mode’s slow seasonal evolution allows it to emerge while the other modes rapidly evolve and/or decay, leading to strongly amplifying and more predictable EP events. CP events develop when the initial state has a substantial contribution from Floquet modes with meridional mode–like SST structures. Thus, while nearly all ENSO events involve the seasonally varying ENSO-mode dynamics, the diversity and predictability of ENSO events cannot be understood without identifying contributions from the remaining Floquet modes. Significance Statement The purpose of this study is to identify structures that lead to seasonal growth of diverse types of El Niño–Southern Oscillation (ENSO) events. An important contribution from this study is that it uses an observationally constrained, empirically derived seasonal model. We find that processes affecting the evolution of diverse ENSO events are strongly seasonally dependent. ENSO events with eastern equatorial Pacific sea surface temperature (SST) characteristics are closely related to a single “ENSO mode” that resembles theoretical models of ENSO variability. ENSO events that have central equatorial Pacific SST characteristics include contributions from additional “meridional mode” structures that evolve via different physical processes. These findings are an important step in evaluating the seasonal predictability of ENSO diversity.

Distinct impacts of major El Niño events on Arctic temperatures due to differences in eastern tropical Pacific sea surface temperatures.

The El Niño Southern Oscillation (ENSO) is a climate mode in the tropical Pacific. The ENSO teleconnections are known to affect Arctic temperature; however, the robustness of this relationship remains debated. We find that Arctic surface temperatures during three major El Niño events are remarkably well simulated by a state-of-the-art model when nudged to the observed pantropical sea surface temperatures (SSTs). SST perturbation experiments show that the 1982–1983 warm pan-Arctic and the 1997–1998 cold pan-Arctic during winter can be explained by far eastern equatorial Pacific SSTs being higher during 1997–1998 than 1982–1983. Consistently, during the 2017–2018 La Niña, unusually low SSTs in the same region contributed to pan-Arctic warming. These pan-Arctic responses to the SSTs are realized through latent heating anomalies over the western and eastern tropical Pacific. These results highlight the importance of accurately representing SST amplitude and pattern for Arctic climate predictions.

Enhanced impact of early‐summer tropical eastern Pacific sea surface temperature on the July–August precipitation over North China after the late 1970s

AbstractThis study identified an enhanced interannual relationship between early‐summer (June–July) tropical eastern Pacific (TEP) sea surface temperature (SST) and subsequent mid‐summer (July–August) precipitation in North China (NC) since the late 1970s. For 1951–1972, the relationship between early‐summer TEP SST and mid‐summer NC precipitation were statistically insignificant. In contrast, for 1977–2018, they were positively significant. Since the late 1970s, the early‐summer negative TEP SST anomaly was generally followed by a significant anomalous anticyclone over the Korean Peninsula and its environs; that facilitated anomalous southerly winds over NC, conveying more moisture from the North Pacific, leading more precipitation over NC. Further studies show that the enhanced relationship between early‐summer TEP SST and tropical Indian Ocean to WNP SST are suggested to be responsible for significantly anticyclonic anomalies over WNP after the late 1970s.

Dominant Modes of Interannual Variability in Atmospheric Water Vapor Content over East Asia during Winter and Their Associated Mechanisms

Atmospheric water vapor content (WVC) is a critical factor for East Asian winter precipitation. This study investigates the dominant modes of interannual variability in WVC over East Asia during winter and the underlying mechanisms. Based on the empirical orthogonal function (EOF) method, the leading mode (EOF1, R2=28.9%) of the interannual variability in the East Asian winter WVC exhibits a meridional dipole pattern characterized by opposite WVC anomalies over northeastern China and eastern China; the second mode (EOF2, R2=24.3%) of the interannual variability in the East Asian winter WVC exhibits a monopole pattern characterized by consistent WVC anomalies over eastern China. EOF1 is mainly modulated by two anomalous zonal water vapor transport (WVT) branches over northeastern China and eastern China, which are associated with an anomalous atmospheric wave train over Eurasia affected by sea ice cover in the Kara Sea-Barents Sea (SIC-KSBS) area in the preceding October-November (ON). EOF2 is mainly modulated by an anomalous westerly WVT branch over eastern China, which is associated with a circumglobal atmospheric zonal wave train in the Northern Hemisphere. This circumglobal zonal wave train is modulated by concurrent central and eastern tropical Pacific sea surface temperature anomalies. The SIC-KSBS anomalies in ON and the concurrent SST anomalies over tropical Pacific may partially account for the interannual variability of EOF1 and EOF2 in winter WVC, thus may providing a theoretical basis for improving the prediction of winter climate over East Asia.

Regional perspectives in Eurasian snow - Indian monsoon relationship: An observational study

Relationship between Indian summer monsoon rainfall and Eurasian snow in the preceding seasons is studied extensively. However, the spatial structures of this snow-monsoon relation have rarely been investigated. The present study is aimed at diagnosing nature of observed linkage between Eurasian winter snow and spatial distribution of following summer monsoon rainfall over India. Eurasian snow association with spatial distribution of rainfall over India features a tri-polar pattern of significant negative-positive-negative correlations over the northern, east-central and peninsular regions of India respectively. The physical mechanism underlying snow-monsoon connection is envisaged through two pathways. One of the channels is through Eurasian winter snow directly affecting the monsoon by modulating large scale circulation, while the other way is indirectly through Tropical Eastern Pacific (TEP) Sea Surface Temperatures (SSTs). Enhanced Eurasian wintertime snow is associated with warm TEP SSTs from preceding winter through to the following summer, leading to anomalous large scale zonal circulation during summer monsoon season, thereby affecting rainfall over India. The spatial facets of snow-monsoon relationship remain unaltered by Indian Ocean Dipole and North Atlantic Oscillation modes.

Global Impact of ENSO on Dust Activities with Emphasis on the Key Region from the Arabian Peninsula to Central Asia

AbstractThe El Niño‐Southern Oscillation (ENSO) has been found to be closely related to dust aerosol activities in many parts of the world. However, previous studies have rarely explored the ENSO’s impacts in the global context. In this study, the responses of the interannual variability of global atmospheric dust content to the ENSO cycle (including the eastern Pacific and central Pacific types) are examined using the MERRA‐2 atmospheric aerosol reanalysis data. The ENSO‐related tropical eastern Pacific sea surface temperature (SST) anomalies in the antecedent winter (November to January) have the most significant effect on the airborne dust content in a region from the Arabian Peninsula to Central Asia during the following spring and summer (April to July), which is identified as the key region (KR) of the ENSO’s impacts. The positive (negative) tropical eastern Pacific SST anomalies in the preceding winter during the El Niño (La Niña) years correspond to significantly reduced (increased) dust column content in the following spring and summer over the KR, which was confirmed using singular value decomposition. With the above (below)‐normal winter SST anomalies in the tropical eastern Pacific, the Walker Circulation weakens (strengthens), and the divergence (convergence) over the western tropical Pacific and the convergence (divergence) over the southern tropical Indian Ocean in the lower troposphere are strengthened, which facilitate (restrain) the southward diffusion of airborne dust in the KR. Meanwhile, the increased (decreased) precipitation and soil moisture and the corresponding vegetation conditions help limit (promote) the dust emission in the KR during the El Niño (La Niña) years.

What Modulates the Intensity of Synoptic-Scale Variability over the Western North Pacific during Boreal Summer and Fall?

AbstractThe present study investigates the factors that affect the year-to-year change in the intensity of synoptic-scale variability (SSV) over the tropical western North Pacific (TWNP) during boreal summer and fall. It is found that the intensity of the TWNP SSV in summer is associated with the equatorial central-eastern Pacific sea surface temperature (SST) anomalies that modulate the background fields through a Rossby wave response both in the source region and along the propagation path of the synoptic-scale disturbances. In fall, the intensity of the TWNP SSV is related to an SST anomaly pattern with opposite anomalies in the equatorial central Pacific and TWNP that modulates the background fields from the equatorial central Pacific to TWNP. However, the equatorial central Pacific SST anomalies alone fail to change the intensity of the TWNP SSV as the induced background field changes are limited to the equatorial central Pacific. It is shown that tropical western Pacific SST anomalies may induce notable changes in the intensity of the TWNP SSV. The relation of the TWNP SSV to the equatorial eastern Pacific SST is weak due to opposite SST anomalies in different types of years. Both seasonal mean and intraseasonal flows provide sources of barotropic energy for the change in the intensity of the TWNP synoptic-scale disturbances in summer. Seasonal mean flow has a main contribution to the barotropic energy conversion for the change in the intensity of the TWNP synoptic-scale disturbances in fall.

Large‐Scale Reductions in Terrestrial Carbon Uptake Following Central Pacific El Niño

AbstractThe El Niño–Southern Oscillation (ENSO) affects global climate and ecosystems, but a recent shift toward more frequent central Pacific (CP) El Niño events could alter these relationships. Here, we show strong responses of the terrestrial carbon cycle to CP ENSO, exceeding even those to canonical eastern Pacific (EP) ENSO. Annual GPP of both global tropical forests and semiarid ecosystems were reduced by ∼0.3–0.5 Pg C yr−1 K−1 increase in CP sea surface temperatures (SSTs), which also reduced net ecosystem production of key tropical and semiarid regions like the Amazon and Australia, but with smaller (and generally not significant) responses to EP SSTs. Given these large negative responses of ecosystem production to CP SSTs, our results suggest that a recent shift toward CP‐dominated ENSO events could further alter Earth's terrestrial carbon cycle, especially when coupled with possible increases in ENSO amplitude with continued warming.