Spatiotemporal Evaluation and Future Projection of Diurnal Temperature Range over the Tibetan Plateau in CMIP6 Models

The diurnal temperature range(DTR) serves as a vital indicator reflecting both natural climate variability and anthropogenic climate change. This study investigates the historical and projected multitemporal DTR variations over the Tibetan Plateau. It assesses 23 climate models from phase 6 of the Coupled Model Intercomparison Project(CMIP6) using CN05.1 observational data as validation, evaluating their ability to simulate DTR over the Tibetan Plateau. Then, the evolution of DTR over the Tibetan Plateau under different shared socioeconomic pathway(SSP) scenarios for the near,middle, and long term of future projection are analyzed using 11 selected robustly performing models. Key findings reveal:(1) Among the models examined, BCC-CSM2-MR, EC-Earth3, EC-Earth3-CC, EC-Earth3-Veg, EC-Earth3-Veg-LR,FGOALS-g3, FIO-ESM-2-0, GFDL-ESM4, MPI-ESM1-2-HR, MPI-ESM1-2-LR, and INM-CM5-0 exhibit superior integrated simulation capability for capturing the spatiotemporal variability of DTR over the Tibetan Plateau.(2) Projection indicates a slightly increasing trend in DTR on the Tibetan Plateau in the SSP1-2.6 scenario, and decreasing trends in the SSP2-4.5, SSP3-7.0, and SPP5-8.5 scenarios. In certain areas, such as the southeastern edge of the Tibetan Plateau, western hinterland of the Tibetan Plateau, southern Kunlun, and the Qaidam basins, the changes in DTR are relatively large.(3) Notably, the warming rate of maximum temperature under SSP2-4.5, SSP3-7.0, and SPP5-8.5 is slower compared to that of minimum temperature, and it emerges as the primary contributor to the projected decrease in DTR over the Tibetan Plateau in the future.

Quantifying the Temperature Effects on the Morbidity of Digestive Diseases In an Inland Plateau-Valley City

Extreme air temperature and increased weather oscillations caused by climate change have been threatening global health.Meteorological conditions are external inducers that may trigger the onset of gastrointestinal diseases,in addition to bacterial infection or behavioral factors including smoking,alcohol consumption,and hot food consumption[1,2].

Variation in the surface heat flux on the north and south slopes of Mount Qomolangma

The distinctive conditions present on the north and south slopes of Mount Qomolangma,along with the intricate variations in the underlying surfaces,result in notable variations in the surface energy flux patterns of the two slopes.In this paper,data from TESEBS(Topographical Enhanced Surface Energy Balance System),remote sensing data from eight cloud-free scenarios,and observational data from nine stations are utilized to examine the fluctuations in the surface heat flux on both slopes.The inclusion of MCD43A3 satellite data enhances the surface albedo,contributing to more accurate simulation outcomes.The model results are validated using observational data.The RMSEs of the net radiation,ground heat,sensible heat,and latent heat flux are 40.73,17.09,33.26,and 30.91 W m^(−2),respectively.The net radiation flux is greater on the south slope and exhibits a rapid decline from summer to autumn.Due to the influence of the monsoon,on the north slope,the maximum sensible heat flux occurs in the pre-monsoon period in summer and the maximum latent heat flux occurs during the monsoon.The south slope experiences the highest latent heat flux in summer.The dominant flux on the north slope is sensible heat,while it is latent heat on the south slope.The seasonal variations in the ground heat flux are more pronounced on the south slope than on the north slope.Except in summer,the ground heat flux on the north slope surpasses that on the south slope.

Effects of surface heating on precipitation over the Tibetan Plateau and its eastern margin

The high terrain of the Tibetan Plateau(TP)has a very important impact on the weather and climate of China,East Asia,South Asia,and even the Northern Hemisphere.However,in recent years,the reasons for the decrease in precipitation in the southeastern edge of the plateau have resulted in cutting-edge research regarding the impact of the TP and its surrounding areas on downstream weather and climate.In this study,the spatial and temporal distribution of surface heat flux and precipitation were analyzed from 1998 to 2022,and the possible mechanism of the decrease of precipitation in the eastern edge of the plateau is explored.The main conclusions are as follows:The annual average sensible heat flux in the TP and its east side is positive,with an average of 33.73 W/m^(2).The annual average latent heat flux is positive,with an average of 42.71 W/m^(2).Precipitation has a similar annual average and seasonal distribution,with modest amounts in the northwest and substantial amounts in the southeast.The average annual accumulated precipitation is 670.69 mm.The first mode of the Empirical Orthogonal Function(EOF)shows that sensible heat flux decreases first,then increases,and then finally decreases during 1998–2022.The modes show the opposite trend in middle part of the plateau.The latent heat flux initially decreases,then increases,and finally decreases in the western plateau and near Sichuan Basin.The mode,however,displays the opposite tendency throughout the rest of the region.The precipitation in the north and south sides of the plateau has decreased since 2013,which is consistent with the changing trend of sensible heat flux.In the rest of the region,the change trend is not obvious.The sensible heat of the main body of the plateau and its east side and Sichuan Basin is negatively correlated with precipitation,that is,when sensible heat flux of the main body of the plateau and its east side and Sichuan Basin is more(less),local precipitation is less(more).The latent heat of the main body of the plateau and its east side,Sichuan Basin is positively correlated with precipitation,indicating that when latent heat flux of the main body of the plateau and its east side,Sichuan Basin is more(less),local precipitation is more(less).

The Characteristics and Controlling Factors of Water and Heat Exchanges over the Alpine Wetland in the East of the Qinghai–Tibet Plateau

Alpine wetland is one of the typical underlying surfaces on the Qinghai–Tibet Plateau.It plays a crucial role in runoff regulation.Investigations on the mechanisms of water and heat exchanges are necessary to understand the land surface processes over the alpine wetland.This study explores the characteristics of hydro-meteorological factors with in situ observations and uses the Community Land Model 5 to identify the main factors controlling water and heat exchanges.Latent heat flux and thermal roughness length were found to be greater in the warm season(June–August)than in the cold season(December–February),with a frozen depth of 20–40 cm over the alpine wetland.The transfers of heat fluxes were mainly controlled by longwave radiation and air temperature and affected by root distribution.Air pressure and stomatal conductance were also important to latent heat flux,and soil solid water content was important to sensible heat flux.Soil temperature was dominated by longwave radiation and air temperature,with crucial surface parameters of initial soil liquid water content and total water content.The atmospheric control factors transitioned to precipitation and air temperature for soil moisture,especially at the shallow layer(5 cm).Meanwhile,the more influential surface parameters were root distribution and stomatal conductance in the warm season and initial soil liquid water content and total water content in the cold season.This work contributes to the research on the land surface processes over the alpine wetland and is helpful to wetland protection.

Temporal and Spatial Variation of Summer Extreme High Temperature in Guizhou Province from 1970 to 2020

Based on the daily maximum temperature data of 31 meteorological observation stations and some statistical methods, the temporal and spatial characteristics of summer extreme high temperature in Guizhou province from 1970 to 2020 are analyzed. The results indicate that: 1) The threshold of extreme high temperature (EHT) in summer in Guizhou province had a large spatial difference, with decreasing characteristics from the northeast to the southwest, it was negatively correlated with the altitude. 2) In most parts of Guizhou province, the extreme high temperature days (EHTD) in summer can reach about 4.2 d, the lowest EHTD occurred in the southernmost part. From June to August, the EHTD gradually increased, especially in Central and eastern parts of Guizhou province. However, the extreme high temperature intensity (EHTI) displayed similar distribution characteristics in summer, June, July and August, with larger value in the northeast part and lower value in the southwest part of Guizhou. 3) EHTD had a rising trend in almost stations, except for the PZ station, the increased range and intensity gradually increased from June to August. But the EHTI had a larger spatial difference, especially in June, it declined in most parts of Guizhou, the declined scope and intensity gradually decreased in July, and completely increased in August, this made EHTI show an increasing trend in summer in most parts the Guizhou province. 4) The averaged EHTD increased by 0.62 d/10a (p 0.1), the significant increase also occurred in August, but it increased insignificantly in June and July. The averaged EHTI had insignificant increase in summer and the three months. In general, the EHTD and EHTI increased in most parts of Guizhou province during the period of 1970-2020, this may be related to the changes of them in August.

Improving Simulations of Vegetation Dynamics over the Tibetan Plateau:Role of Atmospheric Forcing Data and Spatial Resolution

The efficacy of vegetation dynamics simulations in offline land surface models(LSMs)largely depends on the quality and spatial resolution of meteorological forcing data.In this study,the Princeton Global Meteorological Forcing Data(PMFD)and the high spatial resolution and upscaled China Meteorological Forcing Data(CMFD)were used to drive the Simplified Simple Biosphere model version 4/Top-down Representation of Interactive Foliage and Flora Including Dynamics(SSiB4/TRIFFID)and investigate how meteorological forcing datasets with different spatial resolutions affect simulations over the Tibetan Plateau(TP),a region with complex topography and sparse observations.By comparing the monthly Leaf Area Index(LAI)and Gross Primary Production(GPP)against observations,we found that SSiB4/TRIFFID driven by upscaled CMFD improved the performance in simulating the spatial distributions of LAI and GPP over the TP,reducing RMSEs by 24.3%and 20.5%,respectively.The multi-year averaged GPP decreased from 364.68 gC m^(-2)yr^(-1)to 241.21 gC m^(-2)yr^(-1)with the percentage bias dropping from 50.2%to-1.7%.When using the high spatial resolution CMFD,the RMSEs of the spatial distributions of LAI and GPP simulations were further reduced by 7.5%and 9.5%,respectively.This study highlights the importance of more realistic and high-resolution forcing data in simulating vegetation growth and carbon exchange between the atmosphere and biosphere over the TP.

Characteristics and future projections of summer extreme precipitation in Sichuan Province, China

Based on the precipitation data observed by stations and data simulated by 23 CMIP5 models,the features and future changes of summer(Jun-JulAug)extreme precipitation events in Sichuan Province of China were analysed.We found that the total precipitation(RSum),extreme precipitation threshold(Threshold90),extreme precipitation(TR90),extreme precipitation percentage(TR90 pct)and extreme precipitation intensity(TR90 str)decreased from the southeast to the northwest in Sichuan Province,reflecting the differences between eastern Sichuan(ESC,basins)and western Sichuan(WSC,mountains).Compared with the observations,most of the CMIP5 models showed that there were wet biases in WSC and an unclear bias pattern in ESC for the RSum,Threshold90,TR90,and TR90 str.However,the extreme precipitation days(ND90)and TR90 pct values simulated by the models were generally overestimated and underestimated,respectively.Compared with the historical period,most models showed obvious increases in the TR90 and TR90 pct in the 21 century,while the characteristics of Rsum,ND90,and TR90 str were inconspicuous.Compared with the mid-21 st century,the extreme precipitation in the late-21 st century exhibited a certain degree of increase.Even during the same period,the results of RCP8.5 were higher than those of RCP4.5,especially for the ND90,TR90,and TR90 pct.

Effects of transport on aerosols over the eastern slope of the Tibetan Plateau:synergistic contribution of Southeast Asia and the Sichuan Basin

The aerosol optical properties and chemical components of PM2.1(particulate matter with a diameter of 2.1μm or less)were investigated at Mount Gongga on the eastern slope of the Tibetan Plateau from April 2012 to December 2014.The annual mean aerosol optical depth(AOD)was 0.35±0.23,and the?ngstr?m exponent was 1.0±0.38.The AOD exhibited higher values in summer and winter,but lower values in spring and autumn.Dividing the observational periods into dry and wet seasons,the authors found that the concentrations of K^+,elemental carbon,secondary inorganic aerosols,and primary and secondary organic carbon in the dry(wet)season were 0.29(0.21),0.88(0.60),7.4(4.5),7.5(5.1),and 3.9(12)μg m?3,respectively.Combined with trajectory analysis,the authors found that higher concentrations of K^+,elemental carbon,and primary organic carbon indicated the effects of biomass burning from Southeast Asia during the dry season.However,the oxidation of volatile organic compounds was the main source of aerosols during the wet season,which originated from the Sichuan Basin.

Synergistic Effect of the Planetary-scale Disturbance, Typhoon and Meso-β-scale Convective Vortex on the Extremely Intense Rainstorm on 20 July 2021 in Zhengzhou

On 20 July 2021,northern Henan Province in China experienced catastrophic flooding as a result of an extremely intense rainstorm,with a record-breaking hourly rainfall of 201.9 mm during 0800–0900 UTC and daily accumulated rainfall in Zhengzhou City exceeding 600 mm(“Zhengzhou 7.20 rainstorm”for short).The multi-scale dynamical and thermodynamical mechanisms for this rainstorm are investigated based on station-observed and ERA-5 reanalysis datasets.The backward trajectory tracking shows that the warm,moist air from the northwestern Pacific was mainly transported toward Henan Province by confluent southeasterlies on the northern side of a strong typhoon In-Fa(2021),with the convergent southerlies associated with a weaker typhoon Cempaka(2021)concurrently transporting moisture northward from South China Sea,supporting the rainstorm.In the upper troposphere,two equatorward-intruding potential vorticity(PV)streamers within the planetary-scale wave train were located over northern Henan Province,forming significant divergent flow aloft to induce stronger ascending motion locally.Moreover,the converged moist air was also blocked by the mountains in western Henan Province and forced to rise so that a deep meso-β-scale convective vortex(MβCV)was induced over the west of Zhengzhou City.The PV budget analyses demonstrate that the MβCV development was attributed to the positive feedback between the rainfall-related diabatic heating and high-PV under the strong upward PV advection during the Zhengzhou 7.20 rainstorm.Importantly,the MβCV was forced by upper-level larger-scale westerlies becoming eastward-sloping,which allowed the mixtures of abundant raindrops and hydrometeors to ascend slantwise and accumulate just over Zhengzhou City,resulting in the record-breaking hourly rainfall locally.

Response of Freezing/Thawing Indexes to the Wetting Trend under Warming Climate Conditions over the Qinghai–Tibetan Plateau during 1961–2010:A Numerical Simulation

Since the 1990s,the Qinghai–Tibetan Plateau(QTP)has experienced a strikingly warming and wetter climate that alters the thermal and hydrological properties of frozen ground.A positive correlation between the warming and thermal degradation in permafrost or seasonally frozen ground(SFG)has long been recognized.Still,a predictive relationship between historical wetting under warming climate conditions and frozen ground has not yet been well demonstrated,despite the expectation that it will become even more important because precipitation over the QTP has been projected to increase continuously in the near future.This study investigates the response of the thermal regime to historical wetting in both permafrost and SFG areas and examines their relationships separately using the Community Land Surface Model version 4.5.Results show that wetting before the 1990s across the QTP mainly cooled the permafrost body in the arid and semiarid zones,with significant correlation coefficients of 0.60 and 0.48,respectively.Precipitation increased continually at the rate of 6.16 mm decade–1 in the arid zone after the 1990s but had a contrasting warming effect on permafrost through a significant shortening of the thawing duration within the active layer.However,diminished rainfall in the humid zone after the 1990s also significantly extended the thawing duration of SFG.The relationship between the ground thawing index and precipitation was significantly negatively correlated(−0.75).The dual effects of wetting on the thermal dynamics of the QTP are becoming critical because of the projected increases in future precipitation.

Changes in Water Use Efficiency Caused by Climate Change,CO_(2) Fertilization,and Land Use Changes on the Tibetan Plateau

Terrestrial ecosystem water use efficiency(WUE)is an important indicator for coupling plant photosynthesis and transpiration,and is also a key factor linking the carbon and water cycles between the land and atmosphere.However,under the combination of climate change and human intervention,the change in WUE is still unclear,especially on the Tibetan Plateau(TP).Therefore,satellite remote sensing data and process-based terrestrial biosphere models(TBMs)are used in this study to investigate the spatiotemporal variations of WUE over the TP from 2001 to 2010.Then,the effects of land use and land cover change(LULCC)and CO_(2) fertilization on WUE from 1981-2010 are assessed using TBMs.Results show that climate change is the leading contributor to the change in WUE on the TP,and temperature is the most important factor.LULCC makes a negative contribution to WUE(-20.63%),which is greater than the positive contribution of CO_(2) fertilization(11.65%).In addition,CO_(2) fertilization can effectively improve ecosystem resilience on the TP.On the northwest plateau,the effects of LULCC and CO_(2) fertilization on WUE are more pronounced during the driest years than the annual average.These findings can help researchers understand the response of WUE to climate change and human activity and the coupling of the carbon and water cycles over the TP.

Dataset of Comparative Observations for Land Surface Processes over the Semi-Arid Alpine Grassland against Alpine Lakes in the Source Region of the Yellow River

Thousands of lakes on the Tibetan Plateau(TP) play a critical role in the regional water cycle, weather, and climate. In recent years, the areas of TP lakes underwent drastic changes and have become a research hotspot. However, the characteristics of the lake-atmosphere interaction over the high-altitude lakes are still unclear, which inhibits model development and the accurate simulation of lake climate effects. The source region of the Yellow River(SRYR) has the largest outflow lake and freshwater lake on the TP and is one of the most densely distributed lakes on the TP. Since 2011,three observation sites have been set up in the Ngoring Lake basin in the SRYR to monitor the lake-atmosphere interaction and the differences among water-heat exchanges over the land and lake surfaces. This study presents an eight-year(2012–19), half-hourly, observation-based dataset related to lake–atmosphere interactions composed of three sites. The three sites represent the lake surface, the lakeside, and the land. The observations contain the basic meteorological elements,surface radiation, eddy covariance system, soil temperature, and moisture(for land). Information related to the sites and instruments, the continuity and completeness of data, and the differences among the observational results at different sites are described in this study. These data have been used in the previous study to reveal a few energy and water exchange characteristics of TP lakes and to validate and improve the lake and land surface model. The dataset is available at National Cryosphere Desert Data Center and Science Data Bank.

Impact of the Urban Heat Island Effect on Ozone Pollution in Chengdu City,China

With the advancement of urbanization,the urban heat island effect and ozone pollution have become hot issues in urban research.The urban heat island effect can impact ozone conversion,but its mechanism of action is unclear.In this study,the effects of the urban heat island effect on ozone concentration in Chengdu City,China,were investigated by comparing the ozone concentration under different heat island levels with ozone data from March 2020 to February 2021 and the temperature and wind field data of ERA5-Land during the same period.The results showed that:1)regarding the distribution characteristics,the ozone concentration in Chengdu presented a‘high in summer and low in winter’distribution.The ozone concentration in summer(189.54µg/m^(3))was nearly twice that in winter(91.99µg/m^(3)),and the ozone diurnal variation presented a‘single peak and single valley’distribution,with a peak at 16:00.2)For the characteristics of the heat island effect,the heat island intensity in Chengdu was obviously higher in spring than in other seasons,and the diurnal variation showed a‘single peak and single valley’distribution,with the peak and trough values appearing at 9:00 and 17:00,respectively.Spatially,the eastern part of Chengdu was a heat island,while the western and northwestern parts were mostly cold island.3)The correlation analysis between heat island intensity and ozone concentration showed a significant positive correlation but with a 7–8 h time lag.Ambient air temperature was not the main factor affecting ozone concentration.The heat island effect impacts the ozone concentration in two ways:changing the local heat budget to promote ozone generation and forming local urban wind,which promotes ozone diffusion or accumulation and forms different areas of low and high ozone values.

Research progress on the water vapor channel within the Yarlung Zsangbo Grand Canyon, China

The Second Tibetan Plateau Scientific Expedition and Research Program tasked a research team with the“Investigation of the water vapor channel of the Yarlung Zsangbo Grand Canyon(INVC)”in the southeastern Tibetan Plateau(TP).This paper summarizes the scientific achievements obtained from the data collected by the INVC observation network and highlights the progress in investigating the development of heavy rainfall events associated with water vapor changes.The rain gauge network of the INVC can represent the impacts of the Yarlung Zsangbo Grand Canyon(YGC)topography on precipitation at the hourly scale.The microphysical characteristics of the precipitation in the YGC are different than those in the lowland area.The GPM-IMERG(Integrated MultisatellitE Retrievals for Global Precipitation Measurement)satellite precipitation data for the YGC region should be calibrated before they are used.The meridional water vapor flux through the YGC is more important than the zonal flux for the precipitation over the southeastern TP.The decreased precipitation around the YGC region is partly due to the decreased meridional water vapor flux passing through the YGC.High-resolution numerical models can benefit precipitation forecasting in this region by using a combination of specific schemes that capture the valley wind and water vapor flux along the valley floor.

Main Detrainment Height of Deep Convection Systems over the Tibetan Plateau and Its Southern Slope

Deep convection systems (DCSs) can rapidly lift water vapor and other pollutants from the lower troposphere to the upper troposphere and lower stratosphere. The main detrainment height determines the level to which the air parcel is lifted. We analyzed the main detrainment height over the Tibetan Plateau and its southern slope based on the CloudSat Cloud Profiling Radar 2B_GEOPROF dataset and the Aura Microwave Limb Sounder Level 2 cloud ice product onboard the Atrain constellation of Earth-observing satellites. It was found that the DCSs over the Tibetan Plateau and its southern slope have a higher main detrainment height (about 10-16 km) than other regions in the same latitude. The mean main detrainment heights are 12.9 and 13.3 km over the Tibetan Plateau and its southern slope, respectively. The cloud ice water path decreases by 16.8% after excluding the influences of DCSs, and the height with the maximum increase in cloud ice water content is located at 178 hPa (about 13 km). The main detrainment height and outflow horizontal range are higher and larger over the central and eastern Tibetan Plateau, the west of the southern slope, and the southeastern edge of the Tibetan Plateau than that over the northwestern Tibetan Plateau. The main detrainment height and outflow horizontal range are lower and broader at nighttime than during daytime.

Contributions of climate change, land use change and CO2 to changes in the gross primary productivity of the Tibetan Plateau

The ecosystems on the Tibetan Plateau(TP) are highly vulnerable to climate change, rising CO2 concentration, and land-use and land-cover change(LULCC), but their contributions to changes in the gross primary productivity(GPP) of the TP are not clearly understood. In this study, the role of these three factors on the interannual variations(IAVs) and trends of the TP’s GPP were investigated using 12 terrestrial biosphere models. The ensemble simulations showed that climate change can explain most of the changes in the GPP, while the direct effect of LULCC and rising CO2(mainly fertilization effect) contributed 10% and-14% to the mean GPP values, 37% and -20% to the IAV, and 52% and -24% to the GPP’s trend, respectively. The LULCC showed higher contributions to the significant positive trend in the annual GPP of the TP. However, the results from different model simulations showed that considerable uncertainties were associated with the effects of LULCC on the GPP of the TP.

Impact of the Asian-Pacific Oscillation on early autumn precipitation over Southeast China:CMIP6 evaluation and projection

本文对32个CMIP6模式对8月亚洲-太平洋涛动(APO)与我国东南初秋(9月)降水及大气环流联系的模拟能力进行了评估,并就SSP2-4.5和SSP5-8.5情景下,未来2021-2040年(近期),2041-2060(中期)和2081-2100(长期)期间二者联系的变化进行了预估.基于模式对APO与我国东南初秋降水之间显著正相关关系的再现能力,选取3个模式作为“最优”模式集合(BMME)研究表明,BMME较好地模拟了与APO相关的我国东南初秋降水和大气环流异常,且在再现APO与我国东南部降水的正相关关系,以及东亚高空急流(EAJ)经向位移与APO和我国东南部初秋降水之间的负相关关系方面均优于单个模式.总体而言,未来不同SSP情景下尽管APO与EAJ之间仍呈负相关关系,但APO与我国东南初秋降水以及EAJ与我国东南降水的关系将呈减弱确实.此外,不同模式预估结果之间存在明显差异,仅对未来APO-EAJ关系的预估表现出较好的一致性。

Investigating the initiation and propagation processes of convection in heavy precipitation over the western Sichuan Basin

Heavy precipitation events occur often over the western Sichuan Basin in summer, near the transition zone between the Sichuan Basin and the steep terrain of the Tibetan Plateau. One such event -- a heavy precipitation process that occurred on 18-20 August 2010, with clear nocturnal peaks -- is chosen as a case to tentatively explore how the convection associated with convectivescale precipitation is initiated and propagated. By utilizing the vertical momentum equation from the viewpoint of separating perturbation pressure into dynamic and thermal parts, it is demonstrated that the vertical momentum is induced by the imbalance of several forces, including the dynamic/buoyant part of the perturbation pressure gradient force and the buoyancy force, with the latter dominating during the nocturnal-peak period. Although a negative value of the dynamic perturbation pressure gradient force partly offsets the positive buoyant forcing inside the strong updraft, the pattern of vertical motion tendency is largely attributable to its buoyancy because of its larger magnitude. Relative to the buoyancy component, the dynamic part of the vertical perturbation pressure gradient is also examined, revealing a smaller order of magnitude. Thus, it is the thermal effect that should be responsible for the initiation and propagation of convection. As for the convective-scale precipitation, it always presents a trailing morphology relative to the strong leading-side updraft. Furthermore, overlapping strong signals of vertical motion and its tendency point towards strong precipitation in the future.

Relationships between the Extratropical ENSO Precursor and Leading Modes of Atmospheric Variability in the Southern Hemisphere

Previous studies suggest that the atmospheric precursor of E1 Nifio-Southern Oscillation （ENSO） in the extratropical Southern Hemisphere （SH） might trigger a quadrapole sea surface temperature anomaly （SSTA） in the South Pacific and subsequently influence the following ENSO. Such a quadrapole SSTA is referred to as the South Pacific quadrapole （SPQ）. The present study investigated the relationships between the atmospheric precursor signal of ENSO and leading modes of atmospheric variability in the extratropical SH [including the SH annular mode （SAM）, the first Pacific-South America （PSA1） mode, and the second Pacific-South America （PSA2） mode]. The results showed that the atmospheric precursor signal in the extratropical SH basically exhibits a barotropic wavenumber-3 structure over the South Pacific and is significantly correlated with the SAM and the PSA2 mode during austral summer. Nevertheless, only the PSA2 mode was found to be a precursor for the following ENSO. It leads the SPQ-like SSTA by around one month, while the SAM and the PSA1 mode do not show any obvious linkage with either ENSO or the SPQ. This suggests that the PSA2 mode may provide a bridge between the preceding circulation anomalies over the extratropical SH and the following ENSO through the SPQ-like SSTA.