Spring Wind Research Articles

Diatom-based inference of variations in the strength of East Asian spring wind speeds since mid-Holocene

Lake Jingpo is located in Ning'an County, Southeast Heilongjiang Province, northeast China and is strongly influenced by the East Asian monsoon system. Diatom analysis of the last 5000cal.yr BP according to the results of AMS 14C dating provides a detailed history of paleoenvironment changes. The relative abundance of diatom species, Asterionella formosa, Aulacoseira, Cyclostephanos, Stephanodiscus and Discostella species can be used as a proxy of spring wind speed, which is supported by the results of seasonal diatom and reviews of literature on the autoecologies of these species. In the sediment, high relative abundance of A. formosa, Aulacoseira species indicates high wind-driven turbulence of the water column. The diatom record of the past 5000years shows that the spring wind speed shifted from weak to strong to weak. In our result, the relative abundance of Aulacoseira species decreased sharply, while that of small-cell Cyclotella sensu lato (including Stephanodiscus, Cyclostephanos and Discostella) increased since 2000cal.yr BP. The broad alternations between these species are probably keyed to mean temperature and wind variations that control lake circulation and stratification. Our results support the hypotheses that abiotic drivers affect the size structure of planktonic communities and that a warmer climate favors small-sized diatom cells. The change in the ratio of A. formosa and Aulacoseira species to Cyclostephanos, Stephanodiscus and Discostella species (AA/SC) basically correspond to change of the spring insolation (May) at 45°N. Abundance of diatoms in Lake Jingpo roughly corresponds to changes in the Mid- to Low-Latitude Circulation Index of the northern hemisphere as indicated by NH4+ concentration from the GISP2 ice-core, the strength of the Asian summer monsoon as recorded from Hani Peat in Northeastern China, and from a stalagmite found in the Dongge cave in southern China. The results are important in demonstrating the sensitivity of diatoms to climate change, and providing proxy evidence for spring wind speed marked by shifts of diatom type.

Mean winds observed by the Kunming MF radar in 2008–2010

We have investigated the variation of mean wind almost continuously monitored by the Kunming (25.6°N, 103.8°E) MF radar over the period from August 2008 to August 2010. The mean circulation in zonal winds presents a obvious annual variation above 90km and semiannual variation below 85km, but has different direction up 90km and down 85km. An eastward flow is prevailing in spring and autumn below 85km and in spring and summer up 90km with amplitudes as large as 24m/s and 21m/s, respectively. But a westward flow dominates in summer and winter below 85km and in autumn and winter up 90km with amplitudes as large as −12m/s and −10m/s, respectively. Meanwhile the eastward wind dominates for all months at 85–90km. The annual variation also appears in meridional wind below 90km, which means a poleward flow occurs from September to April with amplitude maximum of 11m/s, while the equatorward wind dominates almost for two years with maximum of −26m/s above 90km. Comparison of the wind vertical profile along with standard errors with the HWM07 model winds shows that the zonal wind agrees well with model in winter, autumn and summer, but the meridional wind in spring, winter and summer.

Sr‐Nd isotope composition and clay mineral assemblages in eolian dust from the central Philippine Sea over the last 600 kyr: Implications for the transport mechanism of Asian dust

AbstractDust transport to the tropical/subtropical northwestern Pacific over the past 600 kyr was investigated using radiogenic isotopes (87Sr/86Sr and εNd), together with the clay mineral composition, of eolian dust preserved in a sediment core obtained from the Philippine Sea (12°30′N, 134°60′E). These data revealed the influence of two prevailing dust sources, namely, the Asian deserts and nearby volcanic arcs (e.g., the Luzon Arc), with average contributions of around 70% and 30%, respectively, from each. The clay mineral composition of the core resembled dust from the central Asian deserts (CADs; e.g., the Taklimakan Desert) as in the north‐central Pacific, but published aerosol data collected near the study site during winter/spring have the mineralogical signature of dust originating from the East Asian deserts (EADs). These data indicate that the relative contribution of EAD dust increases with the northeasterly surface winds associated with the East Asian Winter Monsoon (EAWM) during winter/spring, but the Prevailing Westerlies and Trade Winds that carry dust from the CADs is the dominant transport agent in the overall dust budget of the study site. The results of this study contradict the prevailing view that direct dust transport by the EAWM winds in spring dominates the annual flux of eolian dust in the northwest Pacific.

What controls equatorial Atlantic winds in boreal spring?

The factors controlling equatorial Atlantic winds in boreal spring are examined using both observations and general circulation model (GCM) simulations from the coupled model intercomparison phase 5. The results show that the prevailing surface easterlies flow against the attendant pressure gradient and must therefore be maintained by other terms in the momentum budget. An important contribution comes from meridional advection of zonal momentum but the dominant contribution is the vertical transport of zonal momentum from the free troposphere to the surface. This implies that surface winds are strongly influenced by conditions in the free troposphere, chiefly pressure gradients and, to a lesser extent, meridional advection. Both factors are linked to the patterns of deep convection. Applying these findings to GCM errors indicates, that, consistent with the results of previous studies, the persistent westerly surface wind bias found in most GCMs is due mostly to precipitation errors, in particular excessive precipitation south of the equator over the ocean and deficient precipitation over equatorial South America. Free tropospheric influences also dominate the interannual variability of surface winds in boreal spring. GCM experiments with prescribed climatological sea-surface temperatures (SSTs) indicate that the free tropospheric influences are mostly associated with internal atmospheric variability. Since the surface wind anomalies in boreal spring are crucial to the development of warm SST events (Atlantic Ninos), the results imply that interannual variability in the region may rely far less on coupled air–sea feedbacks than is the case in the tropical Pacific.

The origin and sources of loess‐like sediment in the Jinsha River Valley, SW China

The grain size of the loess‐like sediment in the Jinsha River Valley is essentially similar to that of typical loess, and it differs from that of the fluvial sediment in the Jinsha River area. We conclude that the loess‐like sediment is of aeolian origin, as is the loess of the Chinese Loess Plateau. The geochemical characteristics of the loess‐like sediment are similar to those of dammed lake and fluvial sediments in the same area, which is significantly different from those of the typical loess in NW China. The geochemical characteristics show that the loess‐like sediment originated from proximal materials. Combined with the grain‐size distribution pattern of the aeolian deposits, we suggest that the loess‐like sediment of the Jinsha River Valley originated from the dammed lake and fluvial sediments that accumulated in the valley. The local mountain‐valley wind circulation (especially the valley wind in winter and spring) provided the transport force for the loess‐like sediment. The presentation of the loess‐like sediment may indicate the appearance of the grassland and forest steppe and the beginning of the dry‐hot valley phenomenon.

Barotropic and baroclinic semidiurnal tidal currents in two contrasting coastal upwelling zones of Chile

ABSTRACTCurrent velocity observations from the continental shelves of Coquimbo (~30°S) and Concepcion (~36°30'S), central Chile, were analyzed to evaluate the role of water column stratification and shelf width on baroclinic semidiurnal tidal currents. Semidiurnal barotropic currents off both zones were typically < 5 cm/s, but depth‐dependent semidiurnal flows could exceed 10 cm s‐1 during stratified conditions. Both zones are recognized as pronounced upwelling centers, with maximum upwelling‐favorable winds in spring and summer, respectively. At the northern zone, stratification was mainly controlled by temperature differences between surface and bottom waters with maximum stratification during summer. The southern zone showed more stratification during winter because of freshwater input from local rivers. Consequently, greater variability in the baroclinic semidiurnal currents was observed during summer at the northern continental shelf and in winter at the south. In both regions, much of the semidiurnal variability was consistent with an internal wave's first baroclinic mode of wavelengths of ~10–13 km. Nevertheless, during the period of maximum energy fluxes off the north, the second baroclinic mode (wavelength ~7 km) was also important and matched periods of low upwelling index (relaxation of upwelling favorable winds). Typical energy fluxes during summer integrated in the water column, related to the semidiurnal internal tides were 0.12 W/m of the northern site and 0.1 W/m off the southern site. Possible sites of internal wave generation off the south were the Biobío submarine canyon and the slope/shelf break, while off the north, the generation site was the slope/shelf break.

영천지역 민가의 공간구성과 변화과정에 관한 연구

This study focuses on the regional characteristics observed in the composition and floor plan of folk houses in the Young-cheon region situated in the Southern East inland of Gyungsangbukdo. According to the typical characteristics of the Korean folk house, Young-cheon region is supposed to be classified as the Young-Nam region. Our study shows that the open inverse 'ㄱ' type composition is the most common among others, which consists the living room, UtChae and one BoosokChae that serves as a living room and a farm shop. The typical floor plan is called 'Young Nam type' 'H<TEX>$\hat{o}$</TEX>tjib' composed of four rooms. Young Nam type of house has a wall in front of the room floor with a door to make the space with the room floor as the internal space. This can be explained by the climatic conditions in the Southern region of Gyungsangbukdo, which has a very cold winter and has a harsh spring wind in Young-cheon. The structural feature to which we should pay attention is the Young Nam type house has a gambrel roof. The evolutions of the house in the 70s are observed in the roof during the Saemaeul Movement from a hut to a modernized roof. In the 80s, the replacement of the heating system, expansion of rooms, modernization of kitchen, replacement of paper windows, modernization of roof, and construction of amenities had taken place to change the space, construction and structure following the modern house features.

Wind Energy Potential in Taiwan

The purpose of this paper is to contribute the database to users of wind power in Taiwan. The study analyzes 12 stations in Taiwan. The data were collected during the period 2001-2010. The Weibull distribution method was used to analyze wind characteristics and wind energy potential in the different site and height as well. The results show that the wind speed at the height 100 m and roughness length 0.1 m in Taiwan between 1.7 m/s and 4.3 m/s, and the power density from 5 W/m2 to 75 W/m2. Taipei is the windy place, while Taichung is the less. The direction of the wind most commonly comes from north-east. The wind energy varies depend on season, strong wind in spring and winter, while weak wind in autumn and summer. The results obtained contribute to a global vision of the wind energy potential and the windy areas in Taiwan.

ZEPHYR: failure of a "spring wind" in lung cancer.

Vandetanib is an oral inhibitor of vascular endothelial growth factor receptor-2 (VEGFR-2), epidermal growth factor receptor (EGFR) and REarranged during Transfection (RET) tyrosine kinases that are involved in tumour growth, progression and angiogenesis (1). Therefore, this drug has the advantage to contemporary block different intracellular signalling pathways, potentially providing greater benefit than blocking each pathway individually and overcoming resistance to anti EGFR therapy due to increased expression of VEGF (2,3). Four randomized phase 2 studies in patients with non-small cell lung cancer (NSCLC) showed that vandetanib prolonged progression-free survival (PFS) as single agent or when added to chemotherapy, supporting the development of the drug in phase 3 trials (4). In the article of Lee et al., the results of the ZEPHYR trial that compared vandetanib with placebo in patients with advanced NSCLC after prior therapy with one or two chemotherapy regimens and with an epidermal growth factor receptor tyrosine kinase inhibitor are presented (5). Currently, there is no approved treatment option for this widely pretreated population of NSCLC patients and effective treatments are urgently needed.

The seasonal variability of an air-sea heat flux in the northern South China Sea

The seasonal variabilities of a latent-heat flux (LHF), a sensible-heat flux (SHF) and net surface heat flux are examined in the northern South China Sea (NSCS), including their spatial characteristics, using the in situ data collected by ship from 2006 to 2007. The spatial distribution of LHF in the NSCS is mostly controlled by wind in summer and autumn owing to the lower vertical gradient of air humidity, but is influenced by both wind and near-surface air humidity vertical gradient in spring and winter. The largest area-averaged LHF is in autumn, with the value of 197.25 W/m(2), followed by that in winter; the third and the forth are in summer and spring, respectively. The net heat flux is positive in spring and summer, so the NSCS absorbs heat; and the solar shortwave radiation plays the most important role in the surface heat budget. In autumn and winter, the net heat flux is negative in most of the observation region, so the NSCS loses heat; and the LHF plays the most important role in the surface heat budget. The net heating is mainly a result of the offsetting between heating due to the shortwave radiation and cooling due to the LHF and the upward (outgoing) long wave radiation, since the role of SHF is negligible. The ratio of the magnitudes of the three terms (shortwave radiation to LHF to long-wave radiation) averaged over the entire year is roughly 3:2:1, and the role of SHF is the smallest.

WRF/FLEXPART를 이용한 한반도 동남지역 계절별 공기괴 이동 패턴 분석

Air pollution inventories are aggregated around south-eastern part of the Korean Peninsular including Busan, Ulsan, and Changwon cities. Because densely populated cities are concentrated in this region, air pollutants emitted from one of these cities tend to be impacted on the air quality of other cities. In order to clarify the seasonal movement pattern of emitted particles, several numerical simulations using WRF/FLEXPART were carried out. Four cases were selected for each season. The Weather Research and Forecasting model (WRF) reproduced atmospheric flow fields with nested grids. The seasonal pattern of air mass of study area was determined by backward and forward trajectories. As a result, the air parcel moves from northwest to southeast due to northwesterly winds in spring and winter. Also air parcel transports from south to north in summer, and moves from west to east. Because the air mass moves differently in each season, these characteristics should be considered when performing air quality analysis.

Seasonality of the Pacific Decadal Oscillation

Abstract The seasonality of the Pacific decadal oscillation (PDO) is examined using North Pacific sea surface temperature (SST) in observations and in a 480-yr simulation with the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) coupled model. The PDO, both in observations and in the CFS, shows similar seasonality, with increasing SST variance during spring and a maximum in late spring and early summer. The vertical structure of the ocean temperature anomaly associated with the PDO in the CFS displays a significant transition from a deep to a shallow structure during late spring, consistent with the seasonal variation of the mean ocean mixed layer depth (MLD). An analysis of atmospheric surface wind and SST anomalies from the CFS simulation indicates that there is a 1-month delay in the PDO-related SST response to the atmospheric wind forcing. The results based on the CFS simulation are generally consistent with observations, including both atmospheric data from the NCEP/Department of Energy (DOE) Global Reanalysis 2 (GR-2) and ocean data from the NCEP Global Ocean Data Assimilation System (GODAS). The 1-month delay together with the seasonal variation of the mean MLD tends to amplify the PDO-related SST response to the atmospheric surface wind in late spring to early summer, and the combination leads to the maximum variability of the PDO, which is a 3-month delay from the peak phase of the surface wind in February and March.

Distinguishing the provenance of fine-grained eolian dust over the Chinese Loess Plateau from a modelling perspective

The provenance of fine-grained eolian dust over East Asia is distinguished using a regional climate model. Five major source regions within China and Mongolia are considered: sandy lands in the northeastern China, deserts in the northern China, the Gobi deserts, the Taklimakan deserts in western China and deserts on the Tibet an Plateau. The contribution of each dust source is evaluated for the downwind eolian sediments in the Chinese Loess Plateau (CLP) and Japan Sea (JS). The results show that the adjoining northern and Gobi deserts dominate the dust depositions over CLP and over eastern China, although Taklimakan deserts are actually the largest emission source. On the marine deposits in JS, Taklimakan deserts exert a more significant role since the particles from Taklimakan tend to be raised into upper atmosphere and delivered for a longer distance. The agent for dust delivery also differs among different sources. Dust from northern deserts is dominantly carried by the local northwesterly winds in spring associated with the East Asian winter monsoon system and restricted in the low-level atmosphere, while the westerly winds in the midto high-level troposphere become of great importance and more likely to be responsible for the transport of Taklimakan dust.

Seasonal variability in the optical properties of Baltic aerosols

A five-year dataset of spectral aerosol optical thickness was used to analyse the seasonal variability of aerosol optical properties (the aerosol optical thickness (AOT) at wavelength λ = 500nm, AOT(500) and the Ångström exponent for the 440–870nm spectral range, α(440, 870)) over the Baltic Sea and dependence of these optical properties on meteorological factors (wind direction, wind speed and relative humidity). The data from the Gotland station of the global radiometric network AERONET (Aerosol Robotic Network, http://aeronet.gsfc.nasa.gov) were taken to be representative of the Baltic Sea conditions. Meteorological observations from Fårosund were also analysed.Analysis of the data from 1999 to 2003 revealed a strong seasonal cycle in AOT(500) and α(440, 870). Two maxima of monthly mean values of AOT(500) over the Baltic were observed. In April, an increase in the monthly mean aerosol optical thickness over Gotland most probably resulted from agricultural waste straw burning, mainly in northern Europe and Russia as well as in the Baltic states, Ukraine and Belarus. During July and August, the aerosol optical thickness was affected by uncontrolled fires (biomass burning). There was a local minimum of AOT(500) in June.Wind direction, a local meteorological parameter strongly related to air mass advection, is the main meteorological factor influencing the variability of aerosol optical properties in each season. The highest mean values of AOT(500) and α(440, 870) occurred with easterly winds in both spring and summer, but with southerly winds in autumn.

Environmental control of the breeding success of rhinoceros auklets at Triangle Island, British Columbia

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 424:285-302 (2011) - DOI: https://doi.org/10.3354/meps08950 Environmental control of the breeding success of rhinoceros auklets at Triangle Island, British Columbia Gary Borstad1,*, William Crawford2, J. Mark Hipfner3, Richard Thomson2, Kim Hyatt4 1ASL Environmental Sciences Inc., Victoria, British Columbia, V8M 1Z5, Canada 2Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, British Columbia, V8L 4B2, Canada 3Environment Canada, RR#1 5421 Robertson Road, Delta, British Columbia, V4K 3N2, Canada 4Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, V8L 4B2, Canada *Email: gborstad@aslenv.com ABSTRACT: There are few studies of the mechanistic links between physical environmental processes and biotic responses in marine ecosystems that have strong predictive power. At Triangle Island, the largest seabird colony along Canada’s Pacific coast, annual breeding success of rhinoceros auklets Cerorhinca monocerata varies dramatically. Previous studies have correlated this variability with ocean temperature, but this relationship occasionally fails, suggesting that it is not causal. We used historical satellite data time series of sea surface temperature, chlorophyll, and winds to study the oceanography of this remote colony. We found that rhinoceros auklets bred more successfully when the spring transition in regional winds and the resulting spring phytoplankton bloom occurred early in April. These factors appear to control the annual recruitment of Pacific sandlance Ammodytes hexapterus, as measured by the percent by biomass of young-of-the-year sandlance in the nestling diet. These linkages imply bottom-up control in this system. Suggesting broader implications of our work, we also found that marine survival of economically and culturally important sockeye salmon Oncorhynchus nerka from nearby Smith Inlet was strongly correlated with the fledgling mass of the rhinoceros auklets, sandlance in the chicks’ diets, and regional chlorophyll in April. The timing of the spring wind transition and phytoplankton bloom appear to be important for other predators in this system. We think that these relationships with wind and chlorophyll derived from satellite data are potentially valuable explanatory tools that will be widely applicable to studies of early marine survival of many marine species. KEY WORDS: Rhinoceros auklet · Ocean chlorophyll · Ocean temperature · Wind · Satellite imagery · Sandlance · Salinity · Sockeye salmon · Triangle Island Full text in pdf format PreviousCite this article as: Borstad G, Crawford W, Hipfner JM, Thomson R, Hyatt K (2011) Environmental control of the breeding success of rhinoceros auklets at Triangle Island, British Columbia. Mar Ecol Prog Ser 424:285-302. https://doi.org/10.3354/meps08950 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 424. Online publication date: March 01, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Distinguishing the provenance of fine-grained eolian dust over the Chinese Loess Plateau from a modelling perspective

The provenance of fine-grained eolian dust over East Asia is distinguished using a regional climate model. Five major source regions within China and Mongolia are considered: sandy lands in the northeastern China, deserts in the northern China, the Gobi deserts, the Taklimakan deserts in western China and deserts on the Tibet an Plateau. The contribution of each dust source is evaluated for the downwind eolian sediments in the Chinese Loess Plateau (CLP) and Japan Sea (JS). The results show that the adjoining northern and Gobi deserts dominate the dust depositions over CLP and over eastern China, although Taklimakan deserts are actually the largest emission source. On the marine deposits in JS, Taklimakan deserts exert a more significant role since the particles from Taklimakan tend to be raised into upper atmosphere and delivered for a longer distance. The agent for dust delivery also differs among different sources. Dust from northern deserts is dominantly carried by the local northwesterly winds in spring associated with the East Asian winter monsoon system and restricted in the low-level atmosphere, while the westerly winds in the mid- to high-level troposphere become of great importance and more likely to be responsible for the transport of Taklimakan dust.

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

Abstract. Zonal and meridional winds have been measured in the upper mesosphere and lower thermosphere at polar latitudes using two ground-based meteor radars. One radar is located at Rothera (68° S, 68° W) in the Antarctic and has been operational since February 2005. The second radar is located at Esrange (68° N, 21° E) in the Arctic and has been operational since October 1999. Both radars have produced relatively continuous measurements. Here we consider measurements made up to the end of 2009. Both radars are of similar design and at conjugate geographical latitudes, making the results directly comparable and thus allowing investigation of the differences in the mean winds of the Antarctic and Arctic regions. The data from each radar have been used to construct climatologies of monthly-mean zonal and meridional winds at heights between 80 and 100 km. Both Antarctic and Arctic data sets reveal seasonally varying zonal and meridional winds in which the broad pattern repeats from year to year. In particular, the zonal winds display a strong shear in summer associated with the upper part of the westward summertime zonal jet. The winds generally reverse to eastward flow at heights of ~90 km. The zonal winds are eastward throughout the rest of the year. The meridional winds are generally equatorward over both sites, although brief episodes of poleward flow are often evident near the equinoxes and during winter. The strongest equatorward flows occur at heights of ~90 km during summer. There are significant differences between the mean winds observed in the Antarctic and Arctic. In particular, the westward winds in summer are stronger and occur earlier in the season in the Antarctic compared with the Arctic. The eastward winds evident above the summertime zonal wind reversal are significantly stronger in the Arctic. The summertime equatorward flow in the Antarctic is slightly weaker, but occurs over a greater depth than is the case in the Arctic. Comparisons of these observations with those of the URAP and HWM-07 empirical models reveal a number of significant differences. In particular, the zonal winds observed in the Antarctic during wintertime are significantly weaker than those of URAP. However, the URAP zonal winds are a good match to the observations of the Arctic. Significant differences are evident between the observations and HWM-07. In particular, the strong wintertime zonal winds of the Arctic in HWM-07 are not evident in the observations and the summertime zonal winds in HWM-07 are systematically stronger than observed. The agreement with meridional winds is generally poor. There is a significant amount of inter-annual variability in the observed zonal and meridional winds. Particularly high variability is observed in the Arctic zonal winds in spring and is probably associated with stratospheric warmings.

Seasonal variation in leaf-litter input and leaf dispersal distances to streams: the effect of converting broadleaf riparian zones to conifer plantations in central Japan

Sugi (Cryptomeria japonica D. Don) is one of the most important evergreen coniferous plantation species in Japan. Much of the riparian forest that was originally dominated by deciduous broadleaf trees has been converted into sugi plantations. The present study investigated the seasonality of leaf-litter input and leaf dispersal to streams to assess the effects of converting riparian forest to sugi plantations. The seasonality of leaf-litter input was assessed at three streams in Nagoya University Forest. At one stream dominated by deciduous broadleaf trees, input was limited to autumn. At two streams in a sugi plantation, input was prolonged from autumn to early spring, and was dominated by sugi needles from winter to early spring. These results suggest that sugi plantations alter the seasonality of leaf-litter input from riparian forests and affect stream ecosystems. Leaf dispersal was assessed by considering the relationship between leaf dispersal distance from three forest layers to the stream and leaf-litter input into two streams. The maximum leaf dispersal distance was 26–28 m for deciduous broadleaf trees from mid-October to November and 10–12 m for sugi needles from December to April. Leaf dispersal distance depended on the tree species. Four species of deciduous broadleaf tree showed greater leaf dispersal than that of sugi. The mean weight of individual sugi needles was higher than that of the broadleaf trees’ leaves, and dispersal depended on strong winds in winter and early spring. Although the leaf dispersal distance from the understory was within 2–4 m, it could be a significant source of leaf-litter input to streams.

Strengthening of Tropical Indian Ocean Teleconnection to the Northwest Pacific since the Mid-1970s: An Atmospheric GCM Study*

Abstract The correlation of northwest (NW) Pacific climate anomalies during summer with El Niño–Southern Oscillation (ENSO) in the preceding winter strengthens in the mid-1970s and remains high. This study investigates the hypothesis that the tropical Indian Ocean (TIO) response to ENSO is key to this interdecadal change, using a 21-member ensemble simulation with the Community Atmosphere Model, version 3 (CAM3) forced by the observed history of sea surface temperature (SST) for 1950–2000. In the model hindcast, the TIO influence on the summer NW Pacific strengthens in the mid-1970s, and the strengthened TIO teleconnection coincides with an intensification of summer SST variability over the TIO. This result is corroborated by the fact the model’s skills in simulating NW Pacific climate anomalies during summer increase after the 1970s shift. During late spring to early summer, El Niño–induced TIO warming decays rapidly for the epoch prior to the 1970s shift but grows and persists through summer for the epoch occurring after it. This difference in the evolution of the TIO warming determines the strength of the TIO teleconnection to the NW Pacific in the subsequent summer. An antisymmetric wind pattern develops in spring across the equator over the TIO, and the associated northeasterly anomalies aid the summer warming over the north Indian Ocean by opposing the prevailing southwest monsoon. In the model, this antisymmetric spring wind pattern is well developed after but absent before the 1970s shift.

Intraseasonal variability of the ocean — atmosphere coupling in the Gulf of Guinea during boreal spring and summer

AbstractStatistical analyses of the satellite TMI sea‐surface temperature (SST) and QuikSCAT surface winds in boreal spring and summer are performed to investigate the intraseasonal variability of air–sea interactions in the Gulf of Guinea. There, empirical orthogonal function decomposition shows the existence of peaks around 15 days, and their lagged cross‐correlation the signature of an expected 5‐day lag wind forcing and 3‐day lag strong negative SST feedback. Lagged linear regressions are performed onto a reference SST index of the cold tongue northern front in the Gulf of Guinea. A cold SST anomaly covering the equatorial and coastal upwelling is forced after about one week by stronger‐than‐usual south‐easterlies linked to the St Helena anticyclone, suggesting that intraseasonal variability in the Gulf of Guinea is connected to large‐scale fluctuations in the South Atlantic. Within about 5°S and 5°N, two retroactions between SST and surface wind appear to dominate near‐surface atmosphere conditions. When the wind leads the SST, stronger monsoonal winds north of 2°N are partly sustained by the developing SST anomaly and bring more humidity and rainfall toward the continent. When the SST leads the wind, a reversal of anomalous winds is observed mainly south of 2°N, closing a negative feedback loop with a biweekly periodicity. Eventually, further investigation with an ocean model emphasizes the contribution of the horizontal advection in shaping these intraseasonal SST signals. The contribution of vertical processes may also be important but was more difficult to estimate. Copyright © 2010 Royal Meteorological Society