英语论文写作常用句式

• 文章标题
• Abstract 
  • 摘要第一句话
• Introduction
  • 重要性及研究进展
  • 描述猜想
  • 引用句型
  • 文章目标
  • 结构简介
• Data and model
  • Data
  • Model
  • Methodology
• Discussion
  • Conjunction
  • 归因
  • 引用图片
  • 描述现象
    • 描写多个现象
    • 存在对比
    • 描写单一现象
    • 重点突出现象
    • 涉及图序 和 表格
• 动力描述
• Figure caption
• 文章结尾
• summary
• 研究意义

绝热与非绝热经常搞混的几个单词： diabatic 非绝热的，传热的 adiabatic 绝热的，不传热的 adiabatically

文章标题

• climate changes in sth/ (over sp) 什么的气候变化
• climate effects of sth 什么的气候效应
• response of sth to sth
• Seasonally-dependent impact of easterly wind bursts on the development of El Niño events
• Role of Atlantic air–sea interaction in modulating the effect of Tibetan Plateau heating on the upstream climate over Afro-Eurasia–Atlantic regions
• Signals of Spring Thermal Contrast Related to the Interannual Variations in the Onset of the South China Sea Summer Monsoon
• Multi-scale temporal-spatial variability of the East Asian summer monsoon frontal system: observation versus its representation in the GFDL HiRAM
• Sources of Subseasonal Prediction Skill for Heatwaves over the Yangtze River Basin Revealed from Three S2S Models

Abstract 

摘要第一句话

• The location change of the westerly jet core at upper troposphere in June and July is investigated by using the NCEP/NCAR reanalysis data.
• In this study, 40-yr ECMWF Re-Analysis (ERA-40) data are used for the description of the seasonal cycle and the interannual variability of the westerly jet in the Tibetan Plateau region.
• This study examines the representation of the multi-scale temporospatial variability of the East Asian summer monsoon stationary front (MSF) in the High-Resolution Atmospheric Model (HiRAM) of the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory. 

• The structure and dynamics of decadal anomalies in the wintertime midlatitude North Pacifc ocean–atmosphere system are examined in this study, using the NCEP/NCAR atmospheric reanalysis, HadISST SST and Simple Ocean Data Assimilation data for 1960–2010.

• It is suggested that the midlatitude ocean–atmosphere interaction can provide a positive feedback mechanism for the development of initial anomaly, in which the oceanic front and the atmospheric transient eddy are the indispensable ingredients.
• Such a positive ocean–atmosphere feedback mechanism is fundamentally responsible for the observed decadal anomalies in the midlatitude North Pacific ocean–atmosphere system.

Introduction

重要性及研究进展

定义：

• The critical line, by definition, is the region where zonal wind is equal to the phase speed of the eddies.
• Early summer climate of East Asia is characterized by a quasi-stationary rainband that extends from southeast China to Japan.
• This rainband brings the major rainy season, called meiyu in China and baiu in Japan, to these densely populated regions
• Indian monsoon depressions are well known for forming over the Bay of Bengal and the Ganges River plain, then migrating west–northwest over northern India

直接阐述重要性：

• the important role of the sth in sth/(doing sth)

•  The study of synoptic-scale monsoon low-pressure systems has its longest history in India, where well over a century of literature exists on the subject of monsoon depressions

• it will be of interest to see how well the variability of the EP flux divergence represents the acceleration produced by eddies.
• It serves as a first step toward establishing the dynamical connection between extremes in a regional energy cycle (i.e., EACS) and extremes in the hydrological cycle of a remote area (i.e., eastern North Pacific AR).

• The multitude of processes relevant to jet stream dynamics makes its study an intriguing and challenging task. - Such regions are of particular interest from a number of perspectives

• The zonal gradient of the time-mean flow is as important as the meridional gradient in providing energy to the growth of the unstable barotropic modes.
• From the points of view of instability and wave propagation, large-scale mountains can affect both the generation and distribution of atmospheric variability indirectly through the forced stationary waves.
• The mechanism that sustains the latitudinal shift of lower-level baroclinicity with the zonal jet is a key process for understanding the positive eddy feedback in the annular modes and needs further study。
• The meiyu-baiu rainband displays large variability on time scales from hours to interannual, making it perhaps the single most important climatic phenomenon of East Asia.
• Abnormally low rainfall in the meiyu-baiu season causes a shortage of water and affects socioeconomic activity. When meiyu-baiu is very active, on the other hand, torrential rain may occur, causing flooding and mudslides.
• The effect of transient eddies (hereafter abbreviated as TE) on the time-mean state is a fundamental problem in theoretical and observational studies of the general circulation of the atmosphere.
• Understanding its controlling factors is becoming increasingly important due to the need to adapt to global climate change.

关于这方面研究情况总述：

• Recently much progress has been made in understanding the variability of the zonal-mean state.
• Much effort has been devoted to the study of the intensity variability of the EAJS and its association with the East Asian winter monsoon in seasonal and long timescales
• The linkage between the baroclinic instability of the zonally asymmetric mean flows and the localization of storm tracks has been one area of extensive studies.
• An extensive literature exists on meiyu-baiu.
• Several processes have been suggested for the persistent displacement of the lower-level baroclinicity in the annular modes.
• Roles of the Tibetan Plateau (TP) in forming and changing the seasonal Asian climate system have been widely explored.
• Since the pioneering work of Nakamura (1992), many studies examined different physical mechanisms that could explain the presence of the MWM.
• Because of the socioeconomic importance of the EASM, its meteorological and climatological significance are highlighted and widely investigated in the literature. However, even its large-scale dynamics, let alone factors controlling its multiscale variability, remains poorly understood.
• Fundamental questions, such as what controls the location and the seasonal evolution of the EASM front, or why maximum rainfall is not colocated with maximum SSTs, remain largely unanswered. Finding answers to these questions is even more pressing in the face of the predicted expansion of subtropical dry zones with climate change, with potentially significant impacts on subtropical precipitation fronts such as the EASM, and enhanced regional sensitivity to greenhouse gases and aerosol radiative forcing (e.g., Hirahara et al. 2012; Hsu et al. 2013). In this paper, we attempt to address some of these questions, and we specifically focus on the mechanisms through which the TP affects the formation and seasonality of the EASM.

转折点或研究该问题的难点：

• Without an understanding of the risks posed by PTCs for Europe in the current climate, it is difficult to deduce the consequence of a future change in PTC frequency or intensity

• The investigation of orographic influence on atmospheric variability is further complicated by the interference between orographic forcing and the internal dynamical processes.
• However, it is (still) not well understood how topographically forced stationary waves interact with background stationary waves with regard to the poleward eddy heat transport.
• little is known about sth
• Little work, however, has been done to understand what controls regional (zonally asymmetric) patterns of temperature variability, despite their societal relevance.

• has not been previously noted

• However, the dynamic mechanism has not been resolved yet.
• The importance of orographic forcing in the time-mean circulation is well known, but it is unclear/(less clear) what role orography plays in the temporal variation of atmospheric circulation.
• Many/Fundamental questions remain unanswered concerning the zonal asymmetries of the annular mode.

• Indeed, fundamental questions still remain with regard to the dynamics of quasi-stationary waves, such as how mountains affect the diabatic heating field (Held et al. 2002) and the convergence of eddy momentum fluxes (Chang 2009)

• A dynamical explanation for this behavior does not exist and is the main investigation of this study.

- The difficulties in revealing the mechanism of the interannual jet variability also lie in the distinct upstream and downstream dynamics of the East Asian jet

• Without a large dataset of WDs, it is impossible to make any assertions about their gross structure or interaction with the large-scale, other than by theoretical or case-study analysis

描述两面性或多样性：

• Since various timescales of transients may be generated through different mechanisms and have different propagation characteristic, the effect of orography on variability will depend on the timescale.
• Different distributions of the lowerlevel critical line result in different regime behaviors on how the eddies shape the lower-level zonal flow baroclinicity.
• Eddies with different critical line distributions respond to the zonal wind anomalies differently
• So whether or not the total amount of low-frequency variance will be increased or decreased by the inclusion of orographic forcing will depend on both the internal dynamics and the orographic forcing mechanisms.

描述猜想

modulation effects of sth on sth  be forced to propagate southeastward along the eastern flank of the TP

• It is reasonable to suppose that continuous forcing from underlying large-scale mountains has a significant influence on the variation of atmospheric circulation

引用句型

• One example of direct influence of mountains on eddy propagation is the study of Hsu and Wallace (1985). They analyzed the vertical structures of low-frequency variability in the vicinity of the TP and noticed that the propagation of these transient eddies is affected by the large-scale mountains.
• A recent study by Zhang et al. (2009) found that the maintenance of the lower-level baroclinicity strongly depends on the critical line distribution of the energycontaining eddies.
• Similar steering of high-frequency transients by orography was also observed by Hsu (1987). - Linear baroclinic theories going back to Charney (1947) and Eady (1949) predict that the growth rate of baroclinic eddies should be proportional to baroclinicity, which is proportional to the meridional temperature gradient divided by static stability, or to the slope of isentropes.
• Many mechanisms have been proposed to explain why linear theory is insufficient to produce the midwinter suppression and its characteristics. They can be classified into two strands, based on whether or not they require zonally asymmetric forcings of the atmosphere.

• A comparison of the properties of the waves in each regime in the model with those in the atmosphere, as documented by observational studies in the literature (Randel and Held 1991; Kim and Lee 2004).

• Simmons et al. (1983) (also/further) showed/suggested/argues/indicated/concluded/demonstrates/noted/reveal/reasoned that the unstable barotropic normal modes associated with the zonally asymmetric time-mean flow resemble some abserved low-frequency patterns.
• Hendon (1986) used a two-layer GCM to study the variability in an atmosphere above an idealized mountain, and concluded that the overall level of globally integrated transient activity is not affected by the presence of midlatitude orography.
• Lorenz and Hartmann (2001, 2003) through composite analysis found that when the jet shifts poleward (equatorward)  the maximum baroclinicity of the lower-level flow, which is the eddy source region, also moves poleward (equatorward) of its time-mean position, indicating that there could exist a baroclinic mechanism that sustains the positive eddy–zonal flow feedback.
• Eddy equilibration studies also showed that, in the lower levels, it is near the critical line that the eddy heat flux is strongest, characterized by strong eddy–zonal flow interactions.
• Multiple studies suggest that the zonal wind persistence is extended because of a positive feedback between the eddy momentum forcing and the zonal wind anomalies

• We noted that previous studies also suggest that eddies with different length and time scales act differently to the SAM persistence, e.g., Simpson et al. [2013] identified a negative feedback of the barotropic planetary-scale eddies for the jet variability and Nie et al. [2013] showed the different roles of synoptic and low-frequency eddies for the baroclinic anomalies associated with SAM.

• Climatologically, the relationship between the atmospheric transient eddy activities and the mean flow were previously identifed with zonal averages over whole Northern Hemisphere.
• Although as suggested in the previous studies, the baroclinic and barotropic processes are often coupled in the SAM variability, the contributions of the two processes can be evidently separated in the FAWA budget.

文章目标

• Mesoscale features of meiyu-baiu, though important for heavy rain, are beyond the scope of the present study.

• We frst investigated the performance of HiRAM in simulating the climatological values and interannual to interdecadal variations in these indices, and then identifed model biases and explored the likely causes of these biases.
• This study is aimed at a better understanding of how the distribution and generation of atmospheric variability is affected by the inclusion of an idealized large-scale mountain.
• In this study, with a simplified multilayer model, we will show that, in addition to the surface friction and the upper-level eddy propagation, the critical line distribution at lower levels can be crucial for maintaining the strong lowerlevel baroclinicity at the jet-core latitudes in the annular modes.
• Another purpose is to use the precipitation data derived from satellite observations over the oceans along with rain gauge observations over the continent to build up a unified picture of the spatial and temporal structures of the mean monsoon rainy seasons. Particular attention is given to the contrast and linkage among various regional monsoon subsystems. The results will provide an observational basis for validating and identifying the weaknesses of the existing atmospheric general circulation models and climate system models simulating the Asian–Pacific summer monsoon

结构简介

- The next section contains an analysis of Northern Hemisphere January-mean observational data that highlights the differences in the zonal jet structure and leading mode of variability over the Atlantic and Pacific sectors.

• The structure of this paper is assigned as below.
• The rest of this paper is organized as follows.

•  The paper begins with a brief discussion of the data and analysis (section 2), followed in section 3 by a short description of the annual mean zonal wind.  The paper ends with the conclusion.

• Section 2 describes/provides/focuses on an overview of ….. based on the reanalysis /explores an adiabatic mechanism for …../investigates the role of sth in sth /uses a linear model to explore the downstream development of convection along the westerly jet

• Section 2 is a description of the numerical experiments carried out/used in the study.
• The sensitivities of the zonal winds’ low-frequency variation to the surface friction are shown in section 3.
• The eddy–zonal flow interactions in the annular mode–like variations in the sensitivity runs are studied in section 4.
• The mechanisms through which surface friction affects the flow’s low-frequency variation are investigated in section 5.
• A summary and discussion of the results are presented/given in section 6
• Section 4 concludes with a comparison between the model and observational results.
• Results from the observational analysis provide motivation for a series of model runs described in section 3.
• Further discussion on the possible linkage between anomalous midlatitude cyclone activity and land surface warming is given in section 5, followed by conclusions in section 6.

Data and model

Data

• Time averaging is then performed to obtain monthly data.
• Other daily mean and monthly mean atmospheric variables are from NCEP
• These eddy statistics are computed/calculated/compiled using twice-daily gridded analysis produced operationally by the U.S. National Meteorological Center (NMC) during an eight-winter period.
• The winter season is taken to be the 120-day period starting from 15 November.
• At the 1000mb level, the wind and temperature data are derived from the geopotential height analysis using the geostrophic and hydrostatic relationships.
• Our study focuses on the season December–March (DJFM; referred to as wintertime) through the years 1957–2002.
• The precipitation composites shown below (in Fig. 10) are based on the global daily precipitation analyses [from the Global Precipitation Climatology Project (GPCP)] provided by the National Aeronautics and Space Administration, which overlap with the rest of our data in the period 1997–2002 and have a spatial resolution of……
• This study is based on the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) ReAnalysis (ERA-40; Uppala et al. 2005), in particular the daily fields (1200 UTC) of the zonal and meridional wind components at 250 hPa (U250 and V250, respectively), geopotential height at 500 hPa (Z500), and potential temperature on the dynamical tropopause defined here as the 2–potential vorticity unit (PVU) surface
• The data are represented on a 1.5° (latitude) × 1.5° (longitude) grid with 37 vertically distributed pressure levels. All climatological quantities shown in this study are averaged over 20 years.
• The model also provides a decent simulation of the storm tracks.

Model

• the model’s daily mean outputs are at a (horizontal) resolution of 0.25° latitude by 0.3125° longitude  with 72 hybrid model levels in the vertical.
• They have a 2.5° × 2.5° horizontal resolution, covering the same time span of the GPCP precipitation data.
• a hybrid vertical coordinate with 30 levels
• The first 500 days of model data are not used in the analysis, allowing time for model spinup.
• To validate the performance of the CAM5.1 model

• systematic model biases

• In this study, the Community Atmosphere Model version 5.1 coupled with a slab ocean model is employed/utilized/used to highlight the important role of the TP in regulating the upper-tropospheric transient wave train.
• The importance of the lower-level baroclinicity restoration by the low-phase-speed eddies in the annular modes is further demonstrated in sensitivity runs, in which surface friction on eddies is increased to selectively damp the low-phase-speed eddies.
• To better illustrate the eddy–zonal flow interactions in the annular modes, a modified b-plane quasigeostrophic (QG) channel model with interactive static stability and a simplified boundary layer parameterization is used in this study, similar to that of Solomon and Stone (2001) and Zhang et al. (2009).
• A forced-dissipative model configuration with a local source for Rossby waves is used in order to quantify waveguidability by diagnosing the latitudinal distribution of waviness in a longitudinal sector far downstream of the forcing.

Methodology

• We verifed that modest variations in the longitudinal boundaries do not modify our main results.
• This particular truncation has been selected so as to provide an adequate representation of all essential features appearing in the spatial patterns of the eddy forcing terms.
• The geopotantial tendency was finally assembled by summation of the solutions for individual harmonic components.

• The equations were solved for the domain extending vertically from 1000mb to 100mb and meridionally from 20N to 90N.

• With this hybrid Eulerian-Lagrangian diagnostic approach, both the barotropic and baroclinic dynamics in sustaining the positive eddy feedback in the SAM can be explicitly diagnosed and quantitatively compared through our proposed linear feedback model.
• The feature tracking allows the cyclonic and anticyclonic activities to be considered seperately.

• To enable the feature points to be identified as extrema for all the chosen fields, a planetary wave background structure is removed at each data time.

• The results presented here indicate that the analysis method is sufficiently accurate and reliable
• Also noticeable is an equatorward shift of synoptic waves and an amplification of stationary waves in the lower troposphere  around 45°N (not shown).
• An increase in vertical shear of the zonal wind due to enhanced jet speed corresponds well with the enhancement of synoptic waves and with their associated diabatic heating
• The day-to-day correlation coefficient between the acceleration by eddies and the EP flux divergence around the subtropical jet at 30°N and 200 hPa level across 20 winters between December and February (totaling 1800 days) was found to be 0.58
• These composites are formed by averaging for all days, during positive or negative polarity, on which the absolute value of a given PC exceeds 1 standard deviation.

EOF

• In calculating the eigenvectors and the associated principal component (PC) time series we have area weighted the data to account for the uneven resolution of the spherical coordinate grid.
• EOF analysis of zonal wind is performed in/is applied to two separate sectors of the Northern Hemisphere: 1058W–308E, referred to as the Atlantic sector, and 1208E–1058W, referred to as the Pacific sector.
•  By performing empirical orthogonal function (EOF) analysis on the winter mean 500-hPa geopotential height over the trough region of the EAT, Wang et al. (2009a) proposed that the first two leading EOFs (Figs. 1a,b) represent the strength and the horizontal tilt of the seasonal mean EAT, respectively, which are manifestations of the amplitude and phase of the stationary planetary waves
•   Through EOF analysis of the normalized winter mean 500-hPa geopotential height over the trough region of the EAT, Wang et al. (2009a) identified that the first EOF (EOF1) explains 47% of the variance and indicates the intensity of the EAT, while the second EOF (EOF2) explains 22% of the variance and presents the tilt of the EAT axis.
• Correlation and empirical orthogonal function (EOF) analyses were used and the boreal winter is from December to the following February.
• We perform empirical orthogonal function (EOF) analyses on the daily anomalous zonal flow from 30°S to 70°S. For the EOF analysis, the data fields are properly weighted by the square root of the cosine of latitude [North et al., 1982] to account for the decrease of area toward the pole.
•  The first two EOFs are shown in Figure 2a. The leading mode represents a latitudinal shift of the midlatitude jet. The principal component time series associated with the leading EOF hereafter is defined as UPC1. The second mode may be described as a strengthening or weakening of the jet intensity. As in Blanco-Fuentes and Zurita-Gotor [2011], we also perform an EOF analysis on 700 hPa temperature meridional gradient to describe the variability of the low-level baroclinicity. The leading EOF mode manifests a meridional displacement of baroclinicity about its mean position (Figure 2b), while the second mode represents a sharpening or broadening of the maximum baroclinicity. The results are similar for other low-level pressure levels (e.g., 850 hPa). The pattern of the leading mode is more significant and robust as we move to the lower frequencies (results not shown), which is consistent with the results in Blanco-Fuentes and Zurita-Gotor.

Discussion

Conjunction

Additionally, meanwhile, however, in association with,  in what follows 在下文中 As we mentioned earlier As evidenced by

•  With regard to the prevalence of P2 over the WP pattern in our results, the following factors may be of some relevance
• From this perspective, we can gain an insight into the formation of this bias.
• Prior to the presentation of solutions of Eqs.(6)-(8) for observed TE forcing, it is helpful to gain some qualitative insight by considering the analytic solutions corresponding to idealized eddy forcings.
• The above results are more clearly illustrated by the longitude-pressure distributions of zonal wind tendencies along 40N latitude, shown in Fig.4.
• The total effects of the heat and vorticity fluxes is presented/displayed in Fig.4c
• Of note, it is impossible to distinguish causes from effects in climatological analysis. 众所周知，在气候学中很难区分因果关系。

归因

• The long-term change in the annual mean UTW is mainly contributed by the variations of atmospheric deep convection.
• These rainfall biases are directly tied to a northwestward bias in the model simulated seasonal mean location of MSF and this location bias is most pronounced in the month of May.
• A pronounced positive bias in the ocean-land sea level pressure contrast over East Asia, largely manifested as the westward expansion of the western North Pacific subtropical high, is hypothesized to be the main cause of the northwestward location bias of MSF in HiRAM.

• This bias in sea level pressure contrast likely results from the missing of realistic air-sea interactions in the HiRAM simulations.

• While their momentum fluxes are not as important for the jet shift, they play an important role by restoring the lower-level baroclinicity at the jet center, creating a positive feedback loop with the fast eddies that extends the persistence of the jet shift.

•  If midlatitude eddies can propagate away from the center of the jet and be absorbed near the flanks of the jet, the resulting Eliassen–Palm (EP) flux convergence will exhibit a local maximum near the jet core and drive a thermally indirect residual circulation, which can act to reinforce the baroclinicity in the latitude of the jet core and extend the persistence of the eddy-driven jet

• Such a unique confguration of decadal anomalies can be maintained by an unstable ocean–atmosphere interaction mechanism in the midlatitudes, which is hypothesized as follows.
• Associated with a warm PDO phase, an initial midlatitude surface westerly anomaly accompanied with intensifed Aleutian low tends to force a negative SST anomaly by increasing upward surface heat fluxes and driving southward Ekman current anomaly. - As an adjustment of the atmospheric boundary layer to the enhanced oceanic front, the low-level atmospheric meridional temperature gradient and thus the low-level atmospheric baroclinicity tend to be strengthened, inducing more active transient eddy activities that increase transient eddy vorticity forcing.
• The vorticity forcing that dominates the total atmospheric forcing tends to produce an equivalent barotropic atmospheric low pressure north of the initial westerly anomaly, intensifying the initial anomalies of the midlatitude surface westerly and Aleutian low.
• It is therefore reasonable to assume that while this model is highly idealized, it does capture the basic mechanisms allowing for each type of jet to be maintained in the atmosphere.
• A similar mechanism, except for a weak jet as the reference state, may also hold true for the subtropical jet.

引用图片

• The filtering procedure follows that described in Blackmon (1976).
• This treatment of heat transports near horizontal boundaries is essentially similar to that used in the theoretical study by Bretherton (1966).
• The distributions of geopotential and wind tendencies along the strom tracks, as given in Fig.3 and Fig.4 here, are also in qualitative agreement with the results reported by Hoskins et al. (1983, Figs.7a and 13).) / sth agree quite well with sth
• The results presented in these studies are similar to the patterns shown in Figs.3c,d here.
• Figure 3 illustrates/displays the distributions of the lagged regression coefficients between the intraseasonal tropical OLR anomalies and the normalized PC2 time series.
• As shown in Fig. 9a, the averaged change of zonal wind within 70–100E is characterized by two features.
• This concept is illustrated in Fig. 1b. Also depicted in this figure is the meridional propagation of baroclinic waves and the mean meridional circulation driven by these waves’ momentum and heat fluxes. However, this picture does not hold up for the zonal-mean flow during the NH winter where there is only one tropospheric jet centered at 30N.
• These are indicated by the dashed line in Fig. 11.
• The qualitative behavior summarized by Fig. 11 is also valid for zonal wavenumbers 4–8 (not shown). - Figures 3a–3c compare the January mean day-to-day variability, which is here defined as the daily departure from its 31 day running average.
  - The actual temporal variability of the subtropical jet can be seen by the black line in Figure 4, which shows the time evolution of the zonal mean zonal wind at 30°N and 200 hPa during winter 1991/1992

描述现象

描写多个现象

• Also shown by the differences in deep convection, a strengthening of the Walker circulation since the early 2000s is also found in the reanalysis, which is most apparent in boreal summer and fall over the tropical Pacific, facilitating the deep convection to dominate.
  - Corresponding to this circulation pattern at the low level, a dipole structure exists in the geopotential height (GPH) at 500 hPa level, featuring a negative anomaly at the low latitude and a positive one at the high latitude, facilitating an eastward movement of MSF.

• During meiyu-baiu, the upper-level subtropical jet core is located to the north of the rainband, while a lowlevel westerly jet is often observed to the south. Thus the westerly jet exhibits a northward tilt with height during active meiyu-baiu periods.
• In the eastern Eurasian continent, low-level southerlies between the heat low on land and subtropical high over the ocean pushes rainfall poleward by moist advection. In the western continent (e.g., North Africa), the opposite happens, and the rainband is pushed equatorward.
• In the upper troposphere, the tendencies associated with eddy transports of vorticity and heat are seen to oppose each other, with the vorticity transports having a more dominationg influence.

• Bearing in mind that the dominant teleconnection patterns in the middle- and upper-tropospheric geopotential height field exhibit meridionally oriented dipole patterns, tripole patterns in the zonal wind field are to be expected on the basis of geostrophy.

• The first case can be traced to 26 December 2004 and involved a near-stationary SMH center and an eastward-moving, upper level shortwave trough that started near Bangladesh and north-east India and had a minor jet streak to its south.
• The second case can also be traced back to 26 December 2004, when a zonally oriented 500-hPa trough north of Mongolia between 45N-50N, 80E-110E began to intensify and propagate south-eastward.

存在对比

• Contrary to the band pass patterns shown in Fig3, the vorticity transports by the low-frequency eddies lead to strongest eastward accelerationss near the eastern end of the oceanic strom tracks.
• Comparison between the corresponding patterns in Fig.3 reveals that tendencies associated with low-frequency eddies are generally stronger than those associated with synoptic scale disturbances. It is hence anticipated that the distributions of …. are dominated by contributions from the low-pass eddies.
• Compared with sth …

描写单一现象

• wet biases are found over the northern and eastern China and northern Japan, and dry biases extend from the southern China to the western North Pacific.  - The subtropical jet exists at the poleward boundary of the Hadley circulation.
• They drive the zonal wind anomalies associated with the annular mode but weaken the baroclinicity of the jet in the process
• The vertical variation at these locations is characterized by a primary maximum at 1000mb and a secondary maximum bear the tropopause, with typical magnitudes of 1-3 m/s/day.
• The TE heat fluxes hence act to diminish the vertical wind shear over the storm tracks.
• The westerly jet exhibits a distinct northward tilt with height, and the meiyu-baiu rainband is collocated with the midtropospheric westerly axis
• Riding on the westerlies, warm air from the eastern flank of the Tibetan Plateau gradually rises on the sloping isentropic surface.
• North of the NPSH axis, southerly/southwesterly winds prevail and blow ‘down SST gradient’.
• The induced temperature changes lead to a weakening of the jet at its equatorward flank and strengthening at its poleward flank, where the temperature change is larger in fall than in spring (Figures 5a–5c).
• The jet is located between the upper branches of the clockwise Hadley cell in the south and the anticlockwise Ferrel cell in the north.
• In these it can be seen that the potential temperature anomalies at the 2-PVU surface coincide with the locations of maximum meridional shear of the zonal wind, indicating that the latter defines corresponding PV anomalies reflected in the QPV2 distribution.
• The regression maps show a signifcant strip of positive rainfall anomalies, which locates in the NH deep tropics and extends from the the Bay of Bengal to central Pacifc (Fig. 6b). This rain band has two centers of rainfall, one over the Bay of Bengal–South China Sea and another over the western tropical Pacifc.
•  The trough line of EAT (the zero isoline of gradients of geopotential height at 500 hPa in latitudinal direction) is to the east of the Japanese Islands and extends from the Sea of Okhotsk to the East China Sea along the Karafuto and Japanese archipelagos.

重点突出现象

• The most notable features in these patterns are the dipole-like structures located over the western oceans. The centers of extremum for these dipoles tend to straddle the axis of the climatological strom tracks.

涉及图序 和 表格

• It is seen from Fig.4a that the strongest eastward and westward accelerations due to TE heat fluxes occur at 1000 and 200mb, respectively. / sth are seen to occur over sp
• The pattern in Fig.5 suggests that TE vorticity fluxes tend to reinforce the eastern portion of quasi-permanent low pressure ceters over Iceland and the Aleutians.
• as visible in Fig.1
•  The CMIP5 models used in this paper and related information are listed in Table 1.

动力描述

• In a traditional framework based on the separation of eddies from a zonally uniform basic flow, the conventional Eliassen–Palm (E–P) flux has been proven to be a powerful tool for diagnosing propagation of Rossby waves and their interactions with a zonal-mean flow on the meridional plane.
• Further decomposition indicates that the moisture flux convergence primarily arises from the wind convergence (Fig. 7c) over the MB region, whereas moisture advection becomes dominant in midlatitude oceanic regions (Fig. 7d), consistent with the results discussed in the previous section.
• The moisture flux convergence (Fig. 7a) plays a more dominant role in water vapor supply
•  The dominant term is …
•  The main contribution to the total dry enthalpy advection (Fig. 11a) arises from the advection of the zonal mean dry enthalpy by stationary eddies
•  Interestingly the advection of the stationary eddy dry enthalpy by the zonal-mean flow only exerts a minor and relatively local influence over the near downstream of the TP.

Figure caption

• The variance contribution is given at the upper‐right corner of each panel.
• The abscissa is longitude and the ordinate is the time lag associated with strong southerly wind events over eastern China.
• the spatial distributions of the lead-lag correlation coefficients between sth and sth
• Seasonal cycle of the precipitation averaged over the area enclosed by the red lines in Fig.a
• The tick marks on the horizontal axis correspond to the middle of each month.
•  The correlation coefficient map of the JJA precipitation derived from PREC/L data with reference to the mean TP surface air temperature.
• Both the surface air temperature and PREC/L datasets were pre-processed by a 5-year running mean.

regression

• Regression of 300-hPa zonal wind onto the leading PC
• Regression of DJF 500-mb geopotential height against the MEJS index
• One day lagged regression of precipitation anomalies onto the 1979-2016 daily time series (annual cycle has been removed) of vertically-integrated, area-averaged EKE (EKE leads) over the TP region (where the elevation is above 3000 m) in (a) early summer and (b) late summer
• Lag correlation between all-India monsoon rainfall (from Jun to Sep) and monthly Nin˜o3 (58S–58N, 1508–908W) sea surface temperature for the period of 1968–2001.

从行列来介绍图片

• Composite anomalies of the (left column) AR occurrence probability (unit: percent) and (right column) precipitation (unit: mm/day) over the West Coast of the U.S. following the peak of EACS events. Dashed contours indicate 90% significance level. Each column shows T85, MERRA, and T341 from top to bottom
• Results from the T85 simulation are presented on the left column, the middle column is for the MERRA reanalysis data, and the right column is for the T341 simulation. From top to bottom are the results from day 0 (peak of EACS events) to day 6, plotted every 2 days.
• Composite of the height tendency (unit: m/day) forced by the interaction of IF eddies (II) after the peak of EACS events on (top row) “day 1,” (middle row) “day 3,” and (bottom row) “day 5”. Results are from (middle column) the MERRA reanalysis, (left column) the T85 simulation, and (right column) the T341 simulation.

表示显著性

• Only the differences exceeding the 90% and higher confidence levels using the t test are plotted.
• The stippled area represents significance at the 90% and higher confidence levels using the t test.
• areas with dots are signifcant at the 95% confdence level.
• vectors plotted on the map indicate that at least one component of the moisture flux exceeds 90% significance level
•  Identification methods support the analysis shown here and yield very similar results, highlighting the robustness of the results presented in this paper.

文章结尾

• How to quantify the contributions of different eddies via barotropic and baroclinic processes to the total eddy feedback will be a future topic to develop the FAWA approach to diagnosing the annular mode dynamics.

• Diagnosing the barotropic and baroclinic eddy feedbacks in the annular modes is suggested helpful in understanding the overestimated persistence of the annular mode in comprehensive climate models [Gerber et al., 2008; Zurita-Gotor et al., 2013], the variations of the annular mode in the context of climate change [Barnes and Hartmann, 2010; Barnes and Polvani, 2013], or the response of midlatitude weather to recent Arctic amplification [Cohen et al., 2014]. It is expected that the FAWA diagnostic approach proposed in this study will shed new insights in the questions above. - These characteristic features of meiyu-baiu have been discussed in previous studies (e.g., Akiyama 1973; Ninomiya and Murakami 1987) and are generally confirmed in the reanalysis.
• The present study shows a remarkable correspondence in the midtroposphere between horizontal warm advection by the westerlies and upward motion along the meiyu-baiu rainband from late May through August. The thermodynamic balance suggests that the former causes the latter and the following hypothesis is proposed.
• Research is underway to investigate meiyu-baiu variability in light of the dynamics presented here. 根据这里的动力学，梅雨变率的研究正在进行中。
• A closer look at the longitudinal structure of the climatological jets in the atmosphere suggests that ….  This possibility requires further investigation. - the possibility should be examined in greater detail in future studies.
• Further work to improve the method is under way with the aim of implementing the surface-fitting algorithms, as already mentioned.
• The main thrust of future work will be to explore and implement methods of statistical analysis of the sets of tracks obtained from the GCM data.
• Nevertheless, the present work provides many insights into the climatological attributes of the plateau vortex activity and lays a foundation for the ongoing research of physically based classification and composite structure analysis as well as numerical modeling studies of genesis and development mechanisms of this highimpact weather system

- However, the precise processes by which the North Atlantic and the tropical Indian Ocean affect the EA major trough in the winter remain elusive and deserve further numerical study.

summary

• Given the limitations of the unstable normal mode approach as described above, however, a more detailed sensitivity analysis of the unstable normal modes seems unwarranted, and thus is not pursued further.
• To this end, it needs to be stressed again that we attach no special meaning to the growth rate and the rank of the unstable normal modes. What should be noted instead is that for the flow under consideration, linear theory predicts two branches of baroclinic wave activity, one along the midlatitude (away from the subtropical jet) branch, and the other along the subtropical branch; the subtropical jet strength and its position determine the relative dominance of these two branches.

研究意义

• It would be useful to develop an analytical theory that can identify a key parameter that accurately formulates the weak versus strong subtropical regime.