Impact of late winter sea surface temperature seesaw between equatorial central Pacific and Philippine Sea on early spring vegetation over the low-latitude highlands of China

Interannual variation of the southern limit in the Yellow Sea Bottom Cold Water and its causes

This study used a 4-km resolution regional climate model to examine the sensitivity of surface air temperature on the Pacific coast of Japan to sea surface temperature (SST) south of the Pacific coast of Japan during summer. The authors performed a control simulation (CTL) driven by reanalysis and observational SST datasets. A series of sensitivity experiments using climatological values from the CTL SST datasets over a 31-yr period was conducted. The interannual variation in surface air temperature over the Pacific coast was well simulated in CTL. The interannual variation in SST over the Kuroshio region amplified the interannual variation in surface air temperature over the Pacific coast. It was found that 30% of the total variance of interannual variation in surface air temperature can be controlled by interannual variation in SST. The calculated surface air temperature on the Pacific coast increased by 0.4 K per 1-K SST warming in the Kuroshio region. Note that this sensitivity was considerably greater during nighttime than during daytime. Concurrent with the warming in surface air temperature, downward longwave radiation at the surface was also increased. In summer, the increase in latent heat flux was considerably larger than that in sensible heat flux over the ocean because of SST warming, according to the temperature dependence of the Bowen ratio. This implies that the primary factor for the increase in surface air temperature in summer is increased moisture in the lower troposphere, indicating that the regional warming was caused by an increase in H2O greenhouse gas.

<p>This study investigates the relationship between the preceding late spring Sea Surface Temperature (SST) over the tropical Atlantic and the East Asian Summer Monsoon (EASM) based on the observational data and Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations. The results show that warm (cold) tropical Atlantic SST (TASST) during May tends to be followed by a strong (weak) EASM with positive (negative) precipitation anomalies over the subtropical frontal area. Evidence is also provided that the atmospheric teleconnections propagating in both east and west directions are the key mechanisms linking the EASM with the preceding May TASST. That is, the warm TASST anomaly during late spring can persist through the subsequent summer, which, in turn, induces the Gill-type Rossby wave response in the eastern Pacific, exciting the westward relay of the Atlantic signal, as well as the eastward propagation of the Rossby wave along the jet stream. Furthermore, the westward (eastward) propagating teleconnection signal may induce the anomalous anticyclone in the lower troposphere over the Philippine Sea (anomalous tropospheric anticyclone with barotropic structure over the Okhotsk Sea). The anomalous anticyclonic circulation over the Philippine Sea (Okhotsk Sea) brings warm and humid (cold) air to higher latitudes (lower latitudes). These two different types of air mass merge over the Baiu-Meiyu–Changma region, causing the enhanced subtropical frontal rainfall. To support the observational findings, CMIP5 historical simulations are also utilized. Most state-of-the-art CMIP5 models can simulate this relationship between May TASST and the EASM.</p><p>Reference: Choi, Y., Ahn, J. Possible mechanisms for the coupling between late spring sea surface temperature anomalies over tropical Atlantic and East Asian summer monsoon. Clim Dyn <strong>53, </strong>6995–7009 (2019) doi:10.1007/s00382-019-04970-3</p><p>Acknowledgment: This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2018-01213.</p><p> </p>

Monitoring marine plankton ecosystems: Identification of the most relevant indicators of the state of an ecosystem

Responses of piscivorous seabirds at the Pribilof Islands to ocean climate

Based on the leaf area index (LAI) and normalized difference vegetation index (NDVI) from 1982 to 2020, this study reveals a significant increase in the intensity of interannual variability (IIV) in spring (April–May) vegetation over Northeast Asia since the early 2000s. This change is closely linked to the notable increase in the IIV of April surface air temperatures over Northeast Asia from the former period (1986–2001) to the latter period (2002–2016). Further analysis also highlights a salient impact of the North Atlantic Oscillation (NAO) on the strengthened IIV in vegetation. During the latter period, there is a substantial increase in the IIV of the March NAO compared with the former period. This greater variability allows the positive NAO to significantly influence the net heat fluxes, thereby leading to a positive phase of the North Atlantic tripole (NAT) sea surface temperature (SST) pattern in March. Given the persistence of SSTs, the positive NAT SST pattern lasts to April, subsequently causing positive height anomalies over Northeast Asia through a wave train that originates from the North Atlantic and propagates downstream. This process consequently results in an increase in surface air temperature over Northeast Asia and hence the local vegetation. Thus, the increased IIV of the March NAO is conducive to enhancing the IIV in spring vegetation over Northeast Asia.

We examine the impact that changes in the winter Southern Hemisphere (SH) meridional sea surface temperature (SST) gradient have on the sign and strength of the SH Annular Mode (SAM). This is undertaken by perturbing either tropical or extra‐tropical SSTs in an atmospheric General Circulation Model. Changes in winter tropical SSTs have little direct influence on the SAM but do force a strong wave train in geopotential height across the Southern Ocean. In contrast, changes in winter SSTs in the SH extra‐tropics have a profound effect on the SAM: cooler SSTs strengthen the SAM and vice versa. The mechanism involves modifications to the Ferrel cell. As a positive (negative) SAM enhances (reduces) the extra‐tropical meridional temperature gradient, these experiments demonstrate a positive feedback mechanism. SAM variability remains unchanged, indicating a shift in the mean, rather than a change in the probability distribution of its positive and negative phases.

The relationship between the preceding late spring Sea Surface Temperature (SST) over the tropical Atlantic and the East Asian Summer Monsoon (EASM) is investigated based on the observational data and Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations. The results show that warm (cold) tropical Atlantic SST (TASST) during May tends to be followed by a strong (weak) EASM with positive (negative) precipitation anomalies over the subtropical frontal area. Evidence is also provided that the atmospheric teleconnections propagating in both east and west directions are the key mechanisms linking the EASM with the preceding May TASST. That is, the warm TASST anomaly during late spring can persist through the subsequent summer, which, in turn, induces the Gill-type Rossby wave response in the eastern Pacific, exciting the westward relay of the Atlantic signal, as well as the eastward propagation of the Rossby wave along the jet stream. Furthermore, the westward (eastward) propagating teleconnection signal may induce the anomalous anticyclone in the lower troposphere over the Philippine Sea (anomalous tropospheric anticyclone with barotropic structure over the Okhotsk Sea). The anomalous anticyclonic circulation over the Philippine Sea (Okhotsk Sea) brings warm and humid (cold) air to higher latitudes (lower latitudes). These two different types of air mass merge over the Baiu-Meiyu–Changma region, causing the enhanced subtropical frontal rainfall. To support the observational findings, CMIP5 historical simulations are also utilized. Most state-of-the-art CMIP5 models can simulate this relationship between May TASST and the EASM.

Evidence is sought for El Niño–Southern Oscillation (ENSO) teleconnections in the South Pacific extratropical atmospheric circulation and in seasonal temperatures in the west Antarctic Peninsula (WAP) during austral winter. Emphasis is placed on winter sea surface temperature (SST) changes in the tropical central Pacific to infer the seasonal evolution of ENSO events. SST changes are statistically independent of absolute SSTs and are also rarely the same in warm events. Variations in winter tropical SST changes are also found to be strongly mirrored in South Pacific extratropical circulation adjustments that are consistent with Rossby wave modulation. They include changes in the westerlies in the central Pacific (40°S–55°S) and in Antarctic Peninsula meridional flows. ENSO teleconnections are found to indirectly reach WAP winter temperatures via alterations in the local ice extent that is sensitive to the local, ENSO teleconnected, meridional circulation variations. Winter temperatures are also very closely coupled to the winter ‘baseline’ ice extent. It is shown that above-normal pre-winter ice extent is a necessary condition for cold winters but that wintertime ice extent changes owing to ENSO-related meridional flow variations must also be taken into account. The study results are supported by a regression modelling analysis that captures most cold winters in the study period. From these findings and those of previous ENSO teleconnection studies for the South Pacific, it is surmised that ENSO plays a major role in driving interannual temperature variability in this part of Antarctica in the austral winter. Copyright © 2000 Royal Meteorological Society

Annual, summer, and winter sea surface temperatures (SSTs) in the western Arabian Sea were reconstructed through the last 22 kyr using artificial neural networks (ANNs) based on quantitative analyses of planktic foraminifera. Down‐core SST estimates reveal that annual, summer, and winter SSTs were 2, 1.2, and 2.6°C cooler, respectively, during the last glacial period than in the Holocene. A 2.5°C SST increase during Termination 1A (hereinafter referred as glacial to Holocene transition) in the western Arabian Sea. The study reveals a strong seasonal SST contrast between winter and summer from 18 to 14 calendar kyr owing to the combined effect of weak upwelling and strong cold northeasterly winds. Minor or no seasonal SST changes were noticed within the Holocene period, which is attributed to the intense upwelling during the summer monsoon. This causes a lowering of SST to values similar to those of the winter season in analogy with the present day. A 3°C rise in winter SSTs during the glacial to Holocene transition coincides with a strengthening of the monsoon, suggesting a link between winter SST and monsoon initiation from the beginning of the Holocene. Strikingly, annual, summer, and winter SSTs show a cooling trend from ∼8 ka to the present day, implying tropical cooling in the late Holocene.

Spatial patterns of whiting abundance in Scottish waters and relationships with environmental variables

ENSO and Indian Ocean subtropical dipole variability is recorded in a coral record off southwest Madagascar for the period 1659 to 1995

The study deals with the climatic changes in surface air temperature (SAT) in the western part of the Russian Arctic (60—80° N, 30—90° E). To analyze the changes in SAT that occurred over the period 1940—2023, we use data from the ERA5 reanalysis and the results of the Historical model experiment CMIP6. Future changes in SAT until the end of the 21st century we consider based on the results of SSP experiments of CMIP6 models. An increase in the average SAT of the studied region by 2—4°C is shown from approximately the mid-1970s to 2023. Moreover, this increase in SAT is most noticeable in the White and Kara Seas, as well as in the north and east of the Barents Sea. CMIP6 models based on different greenhouse gas emission scenarios produce markedly different forecasts for the increase in SAT for the region under study until the end of the 21st century. Thus, depending on the scenario, the average increase in SAT in the region under study by the end of the 21st century can range from 2—4°C to 6—10°, with stronger growth of SAT in the north of the region under study. At the same time, with little dependence on the future scenario, CMIP6 models predict that in the next 30 years the average SAT of the western part of the Russian Arctic will increase by approximately 2—3°C, and in the north of the region under study its increase may be more than 3°C, and in south — about 2°C. Thus, the difference in average SAT between the north and south of the region under study will decrease throughout the 21st century under any of the SSP scenarios considered.

<p align="justify">The changes in Eurasian vegetation not only have important effects on regional climate, but also have effects on global temperatures and the carbon cycle<span>. </span>In this study, the interannual linkage between spring vegetation <span>growth</span> over Eurasia and winter sea-ice cover over the Barents Sea (SICBS), as well as the <span>prediction of spring Euraisan vegetation </span>are investigated. The Normalized Difference Vegetation Index (NDVI) derived from the advanced very high resolution radiometer is used as the proxy of vegetation <span>growth</span>. During 1982–2015, the winter SICBS is significantly correlated with the spring NDVI over Eurasia (NDVIEA). The positive (negative) winter SICBS anomalies tend to increase (decrease) the spring NDVIEA. The increased winter SICBS corresponds to higher winter surface air temperature and soil temperature over most parts of Eurasia, and in turn, corresponds to less winter snow cover and less snow water equivalent. The persistent less and thinner snow cover from winter to spring over Eurasia, especially over Western and Central Siberia, tends to induce increased surface air temperature through decreased surface albedo and less snowmelt latent heat. Subsequently, the increased surface air temperature corresponding to increased SICBS contributes to higher vegetation <span>growth</span> over Eurasia in spring and vice versa. <span>Based on this linkage, s</span>easonal predictions of spring NDVI over Eurasia are explored by applying the year-to-year increment approach. The prediction models were developed based on the coupled modes of singular value decomposition analyses between Eurasian NDVI and climate factors. One synchronous predictor, the spring surface air temperature from the NCEP<span>’</span>s Climate Forecast System (SAT-CFS), and three previous-season predictors (winter SICBS, winter sea surface temperature over the equatorial Pacific (SSTP), and winter North Atlantic Oscillation (NAO) were chosen to develop four single-predictor schemes: the SAT-CFS scheme, SICBS scheme, SSTP scheme, and NAO scheme. Meanwhile, a statistical scheme that involves the three previous-season predictors (i.e., SICBS, SSTP, and NAO) and a hybrid scheme that includes all four predictors are also proposed. To evaluate the prediction skills of the schemes, one-year-out cross-validation and independent hindcast results are analyzed, revealing the hybrid scheme as having the best prediction skill in terms of both the spatial pattern and the temporal variability of spring Eurasian NDVI.</p>

This study investigates the relationship between subseasonal variations of the circulation and sea surface temperature (SST) over the South China-East Asian coastal region (EACR) in association with the persistent heavy rainfall (PHR) events over South China during May-August through statistical analysis. Based on the intensity threshold and duration criterion of the daily rainfall, a total of 63 May-June (MJ) and 59 July-August (JA) PHR events are selected over South China from 1979 to 2011. The lower-level circulation anomalies on subseasonal timescale exhibit an anomalous cyclone over South China and an anomalous anticyclone shaped like a tongue over the South China Sea (SCS) during the PHR events for MJ group. The anomalous cyclone over South China in MJ originates from low-value systems in the mid-high latitudes before the rainfall. The anomalous anticyclone over the SCS is due to the westward extension of the western Pacific subtropical high (WPSH) and the southeastward propagation of the anomalous anticyclone from South China before the rainfall. For JA group, the lower-level anomalous circulation pattern is similar to that for MJ over the South China-EACR, but with different features of propagation. The subseasonal anomalous anticyclone is also related to the westward stretch of the WPSH, while the anomalous cyclone is traced back to the weak anomalous cyclone over the Philippine Sea several days before the rainfall events.