Spatio-temporal Variation Characteristics of Extreme Climate Events and Their Teleconnections to Large-scale Ocean-atmospheric Circulation Patterns in Huaihe River Basin,China During 1959–2019

Huaihe River Basin(HRB) is located in China’s north-south climatic transition zone,which is very sensitive to global climate change.Based on the daily maximum temperature,minimum temperature,and precipitation data of 40 meteorological stations and nine monthly large-scale ocean-atmospheric circulation indices data during 1959–2019,we present an assessment of the spatial and temporal variations of extreme temperature and precipitation events in the HRB using nine extreme climate indices,and analyze the teleconnection relationship between extreme climate indices and large-scale ocean-atmospheric circulation indices.The results show that warm extreme indices show a significant(P < 0.05) increasing trend,while cold extreme indices(except for cold spell duration) and diurnal temperature range(DTR) show a significant decreasing trend.Furthermore,all extreme temperature indices show significant mutations during 1959-2019.Spatially,a stronger warming trend occurs in eastern HRB than western HRB,while maximum 5-d precipitation(Rx5day) and rainstorm days(R25) show an increasing trend in the southern,central,and northwestern regions of HRB.Arctic oscillation(AO),Atlantic multidecadal oscillation(AMO),and East Atlantic/Western Russia(EA/WR) have a stronger correlation with extreme climate indices compared to other circulation indices.AO and AMO(EA/WR) exhibit a significant(P < 0.05) negative(positive)correlation with frost days and diurnal temperature range.Extreme warm events are strongly correlated with the variability of AMO and EA/WR in most parts of HRB,while extreme cold events are closely related to the variability of AO and AMO in eastern HRB.In contrast,AMO,AO,and EA/WR show limited impacts on extreme precipitation events in most parts of HRB.

Analysis on characteristics of extreme precipitation indices and atmospheric circulation in Northern Shanxi

This article utilizes daily precipitation data from 28 national meteorological stations in northern Shanxi Province spanning from 1972 to 2020,and the US NCEP/NCAR monthly average reanalysis and ERA5 monthly average reanalysis data.The study employs techniques such as empirical orthogonal function(EOF)decomposition,MannKendall mutation and other methods to investigate the spatiotemporal distribution of extreme precipitation index in northern Shanxi and their correlation with atmospheric circulation.The research results show that:the absolute index,relative index,intensity index and sustained dry period index(CDD)in the continuous index appear from southwest to northeast.The spatial distribution characteristics of the central region decrease,while the continuous wet period(CWD)decreases from the central to the east and west.The three indices Rx1day,Rx5day,and CWD mutated in 1978,1975,and 1983 respectively,and other extreme precipitation indices all appeared in a sudden change from a low-value period to a high-value period occurred around 2010.In the high-value years of the summer extreme precipitation index,there is a significant negative anomaly in the height field in the mid-high latitude regions of Eurasia.Northern Shanxi is controlled by a broad low-pressure trough in the Lake Baikal area.Water vapor transported via the east,west,and south routes converges in the northern Shanxi region and encounters cold air from the north.There is a strong upward motion anomaly at 500 hPa in the troposphere,and the dynamic conditions of upper-level divergence and lower-level convergence lead to more summer extreme precipitation in the northern Shanxi region.Conversely,in the low-value years of the summer extreme precipitation index,northern Shanxi is affected by a strong high-pressure ridge north of Lake Baikal.There is a downward motion anomaly at 500 hPa,and the northern Shanxi region lacks water vapor.The cold and warm air cannot converge,and both the water vapor conditions and dynamic conditions are poor,which is not conducive to the production of extreme precipitation in northern Shanxi.

Unprecedented Heatwave in Western North America during Late June of 2021: Roles of Atmospheric Circulation and Global Warming

An extraordinary and unprecedented heatwave swept across western North America(i.e.,the Pacific Northwest)in late June of 2021,resulting in hundreds of deaths,a massive die-off of sea creatures off the coast,and horrific wildfires.Here,we use observational data to find the atmospheric circulation variabilities of the North Pacific and Arctic-Pacific-Canada patterns that co-occurred with the development and mature phases of the heatwave,as well as the North America pattern,which coincided with the decaying and eastward movement of the heatwave.Climate models from the Coupled Model Intercomparison Project(Phase 6)are not designed to simulate a particular heatwave event like this one.Still,models show that greenhouse gases are the main reason for the long-term increase of average daily maximum temperature in western North America in the past and future.

27.3-day and 13.6-day Atmospheric Tide and Lunar Forcing on Atmospheric Circulation

An analysis of time variations of the earth’s length of day (LOD) versus atmospheric geopotential height fields and lunar phase is presented. A strong correlation is found between LOD and geopotential height from which a close relationship is inferred and found between atmospheric circulation and the lunar cycle around the earth. It is found that there is a 27.3-day and 13.6-day east-west oscillation in the atmospheric circulation following the lunar phase change. The lunar revolution around the earth strongly influences the atmospheric circulation. During each lunar cycle around the earth there is, on average, an alternating change of 6.8-day-decrease, 6.8-day-increase, 6.8-day-decrease and 6.8-day-increase in atmospheric zonal wind, atmospheric angular momentum and LOD. The dominant factor producing such an oscillation in atmospheric circulation is the periodic change of lunar declination during the lunar revolution around the earth. The 27.3- day and 13.6-day atmospheric oscillatory phenomenon is akin

Possible Impacts of Barents Sea Ice on the Eurasian Atmospheric Circulation and the Rainfall of East China in the Beginning of Summer

Possible influences of the Barents Sea ice anomalies on the Eurasian atmospheric circulation and the East China precipitation distribution in the late spring and early summer (May-June) are investigated by analyzing the observational data and the output of an atmospheric general circulation model (AGCM). The study indicates that the sea ice condition of the Barents Sea from May to July may be interrelated with the atmospheric circulation of June. When there is more than average sea ice in the Barents Sea, the local geopotential height of the 500-hPa level will decrease, and the same height in the Lake Baikal and Okhotsk regions will increase and decrease respectively to form a wave-chain structure over North Eurasia. This kind of anomalous height pattern is beneficial to more precipitation in the south part of East China and less in the north.

Atmospheric Circulation and Dynamic Mechanism for Persistent Haze Events in the Beijing–Tianjin–Hebei Region

In this study, regional persistent haze events（RPHEs） in the Beijing–Tianjin–Hebei（BTH） region were identified based on the Objective Identification Technique for Regional Extreme Events for the period 1980–2013. The formation mechanisms of the severe RPHEs were investigated with focus on the atmospheric circulation and dynamic mechanisms. Results indicated that：（1） 49 RPHEs occurred during the past 34 years.（2） The severe RPHEs could be categorized into two types according to the large-scale circulation, i.e. the zonal westerly airflow（ZWA） type and the high-pressure ridge（HPR） type. When the ZWA-type RPHEs occurred, the BTH region was controlled by near zonal westerly airflow in the mid–upper troposphere.Southwesterly winds prevailed in the lower troposphere, and near-surface wind speeds were only 1–2 ms^-1. Warm and humid air originating from the northwestern Pacific was transported into the region, where the relative humidity was 70% to 80%, creating favorable moisture conditions. When the HPR-type RPHEs appeared, northwesterly airflow in the mid–upper troposphere controlled the region. Westerly winds prevailed in the lower troposphere and the moisture conditions were relatively weak.（3） Descending motion in the mid-lower troposphere caused by the above two circulation types provided a crucial dynamic mechanism for the formation of the two types of RPHEs. The descending motion contributed to a reduction in the height of the planetary boundary layer（PBL）, which generated an inversion in the lower troposphere. This inversion trapped the abundant pollution and moisture in the lower PBL, leading to high concentrations of pollutants.

Effects of atmospheric circulation on summertime precipitation variability and glacier mass balance over the Tuyuksu Glacier in Tianshan Mountains, Kazakhstan

The amount and the form of precipitation have significant effects on glacier mass balances in high al- titude mountain areas by controlling the accumulation, the ablation and the energy balance of a glacier through impact on the surface albedo. The liquid precipitation has negative effects on glacier accumulation and may in- crease the ablation of surface ice through the heat input for melting. The timing and the forms of precipitation over glacierized regions depend on the weather processes both locally and regionally. Early studies showed that regional to large-scale atmospheric circulation processes play a key role in affecting the precipitation events over glaciers. This paper analyzed the relationship between the inter-annual variability of the summertime precipitation over the Tuyuksu Glacier and the atmospheric circulation types, which related to various atmospheric circulation types in the Northern Hemisphere. Results indicated that the decrease in the duration of zonal processes and the increase in the meridional northern processes were observed in the last decade. The total summer precipitation associated with these processes also increased along with an increase of summertime solid precipitation. Although the decadal fluctuation of glaciological parameters were found in dependent of the above large-scale atmospheric circulation processes, global warming was a dominant factor leading to the mass loss in the recent decades under the back- ground of the increase in precipitation over the Tuyuksu Glacier.

Changes of Atmospheric Circulation since the Last Interstadial as Indicated by the Lake-status Record in China

The effective precipitation and the frame of atmospheric circulation in the past three key periods, i.e. 30 ka BP, 18 ka BP and 6 ka BP, have been analyzed on the basis of the palaeolake status record produced by the Chinese Lake Status Data Base. The results show that the west-central part of China was characterized by high lake-levels at 30 ka BP, resulting from strengthened southwest monsoons; whereas the high lake stand, occurring in the west-central part of China at 18 ka BP, was caused by the southward shift and the strengthening of westerlies although the high-stand distribution was reduced. Meanwhile, the east-central part of China was under the control of strong winter monsoons at 18 ka BP. The high lake-levels, which occurred in the east-central part of China at 6 ka BP, are related to the enhanced East-Asian summer monsoons; while the lowering of the lake-level in the west-central part of China at 6 ka BP was due to the northward shift and corresponding shrink of the westerlies.A comparison between the lake status and the palaeoclimate models has shown that there do exist discrepancies between the geological evidence and the model simulations. The agreement between them provides a possible mechanical explanation on the geological phenomena, but the discrepancy shows that the model needs to be revised to a great extent.

Interannual Variability of Snow Depth over the Tibetan Plateau and Its Associated Atmospheric Circulation Anomalies

The interannual variability of wintertime snow depth over the Tibetan Plateau(TP) and related atmospheric circulation anomalies were investigated based on observed snow depth measurements and NCEP/NCAR reanalysis data.Empirical orthogonal function(EOF) analysis was applied to identify the spatio-temporal variability of wintertime TP snow depth.Snow depth anomalies were dominated by a monopole pattern over the TP and a dipole structure with opposite anomalies over the southeastern and northwestern TP.The atmospheric circulation conditions responsible for the interannual variability of TP snow depth were examined via regression analyses against the principal component of the most dominant EOF mode.In the upper troposphere,negative zonal wind anomalies over the TP with extensively positive anomalies to the south indicated that the southwestward shift of the westerly jet may favor the development of surface cyclones over the TP.An anomalous cyclone centered over the southeastern TP was associated with the anomalous westerly jet,which is conducive to heavier snowfall and results in positive snow depth anomalies.An anomalous cyclone was observed at 500 hPa over the TP,with an anomalous anticyclone immediately to the north,suggesting that the TP is frequently affected by surface cyclones.Regression analyses revealed that significant negative thickness anomalies exist around the TP from March to May,with a meridional dipole anomaly in March.The persistent negative anomalies due to more winter TP snow are not conducive to earlier reversal of the meridional temperature gradient,leading to a possible delay in the onset of the Asian summer monsoon.

Climate-Induced Variability of Sea Level in Stockholm: Influence of Air Temperature and Atmospheric Circulation

This study is focused on climate-induced variation of sea level in Stockholm during 1873-1995. After the effect of the land uplift, is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months （June and August） that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. While the wind is important in the period January-May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables （zonal winds, vorticity and mean air temperature during the previous two months） and the sea level is established for each month. An independent verification of the model shows that it has considerable skill in simulating the variability.

Autumn Snow Cover Variability over Northern Eurasia and Roles of Atmospheric Circulation

This study analyzes the variability of northern Eurasian snow cover（SC） in autumn and the impacts of atmospheric circulation changes. The region of large SC variability displays a southward shift from September to November, following the seasonal progression of the transition zones of surface air temperature（SAT）. The dominant pattern of SC variability in September and October features a zonal distribution, and that in November displays an obvious west-east contrast. Surface air cooling and snowfall increase are two factors for larger SC. The relative contribution of SAT and snowfall changes to SC, however, varies with the region and depends upon the season. The downward longwave radiation and atmospheric heat advection play important roles in SAT changes. Anomalous convergence of water vapor flux contributes to enhanced snowfall.The changes in downward longwave radiation are associated with those in atmospheric water content and column thickness.Changes in snowfall and the transport of atmospheric moisture determine the atmospheric moisture content in September and October, and the snowfall appears to be a main factor for atmospheric moisture change in November. These results indicate that atmospheric circulation changes play an important role in snow variability over northern Eurasia in autumn. Overall, the coupling between autumn Eurasian snow and atmospheric circulation may not be driven by external forcing.

Boreal Winter Rainfall Anomaly over the Tropical Indo-Pacific and Its Effect on Northern Hemisphere Atmospheric Circulation in CMIP5 Models

Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter.The analysis shows that the main features of the interannual variation of tropical rainfall anomalies,especially over the Central Pacific （CP） （5°S-5°N,175°E-135°W） and Indo-western Pacific （IWP） （20°S-20°N,110°-150°E） are well captured in all the CMIP5/AMIP models.For the IWP and western Indian Ocean （WIO） （10°S-10°N,45°-75°E）,the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation.During El Ni（n）o/La Ni（n）a mature phases in boreal winter,consistent with observations,there are geopotential height anomalies known as the Pacific North American （PNA） pattern and Indo-western Pacific and East Asia （IWPEA） pattern in the upper troposphere,and the northwestern Pacific anticyclone （cyclone） （NWPA） in the lower troposphere in the models.Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP,while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO,as the SST anomaly is same in AMIP experiments.It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.

Monthly Variations of Atmospheric Circulations Associated with Haze Pollution in the Yangtze River Delta and North China

Haze pollution in early winter(December and January) in the Yangtze River Delta(YRD) and in North China(NC)are both severe;however, their monthly variations are significantly different. In this study, the dominant large-scale atmospheric circulations and local meteorological conditions were investigated and compared over the YRD and NC in each month. Results showed that the YRD(NC) is dominated by the so-called Scandinavia(East Atlantic/West Russia)pattern in December, and these circulations weaken in January. The East Asian December and January monsoons over the YRD and NC have negative correlations with the number of haze days. The local descending motion facilitates less removal of haze pollution over the YRD, while the local ascending motion facilitates less removal of haze pollution over NC in January, despite a weaker relationship in December. Additionally, the monthly variations of atmospheric circulations showed that adverse meteorological conditions restrict the vertical(horizontal) dispersion of haze pollution in December(January) over the YRD, while the associated local weather conditions are similar in these two months over NC.

Impacts of Two Types of El Nio on Atmospheric Circulation in the Southern Hemisphere

Based on NCEP/NCAR （National Centers for Environmental Prediction/National Center for Atmo- spheric Research） reanalysis data from 1979 to 2010, the impacts of two types of E1 Nino on atmospheric circulation in the Southern Hemisphere （SH） are analyzed. It is shown thaL when a warming event occurs in the equatorial eastern Pacific （EP E1 Nino）, there is a negative sea level pressure （SLP） anomaly in the east- ern Pacific and a positive one in the western Pacific. Besides, there exists a negative anomaly between 40°S and 60°S and a positive anomaly to the south of 60°S. When a warming event in the central Pacific （CP E1 Nino） occurs, there appears a negative SLP anomaly in the central Pacific and a positive SLP anomaly in the eastern and western Pacific, but the SLP anomalies are not so evident in the SH extratropics. In particular, the Pacific-South America （PSA） pattern induced by the CP E1 Nino is located more northwestward, with a weaker anomaly compared with the EP E1 Nino. This difference is directly related with the different position of heating centers associated with the two types of E1 Nino events. Because the SST anomaly associated with CP E1 Nino is located more westward than that associated with EP El Nino, the related heating center tends to move westward and the response of SH atmospheric circulation to the tropical heating changes accordingly, thus exciting a different position of the PSA pattern. It is also noted that the local meridional cell plays a role in the SH high latitudes during EP E1 Nino. The anomalous ascending motion due to the enhancement of convection over the eastern Pacific leads to an enhancement of the local Hadley cell and the meridional cell in the middle and high latitudes, which in turn induces an anomalous descending motion and the related positive anomaly of geopotential height over the Amundsen-Bellingshausen Sea.

The atmospheric circulation patterns influencing the frequency of spring sand-dust storms in the Tarim Basin

Using NCEP/NCAR reanalysis data and the sand-storm frequency data fi＇om 37 weather stations in the Tarim Basin for the period 1961-2009, the relationship between the frequency of spring sandstorms in the Tafim Basin and the associated atmospheric circu- lation pattems is analyzed in this study. We found significantly negative correlations between sandstorm frequency and the 500-hPa geopotential height over the Paris Basin and midwestem Mongolia, while there were positive correlations over the Ural River region. The rising of the 500-hPa geopotential height in midwestem Mongolia and its falling over the Ural region corre- spond to a weakening of the large-scale wave patterns in the Eurasian region, which directly causes the frequency of the sand-dust storms in the Tarim Basin to decline. Also, the abrupt decline in the spring sandstorm frequency in the Tarim Basin observed in the last half-century is associated with profound changes in the atmospheric circulation in these key regions. At the interannual scale, the strengthened cyclonic atmospheric circulation patterns in the western part of Mongolia and the anticyclonic patterns over the East European plains at 500-hPa geopotential height, are responsible for frequent sandstorm occurrences in the Tarim Basin.

Simple General Atmospheric Circulation and Climate Models with Memory

This article examines some general atmospheric circulation and climate models in the context of the notion of “memory”. Two kinds of memories are defined： statistical memory and deterministic memory. The former is defined through the autocorrelation characteristic of the process if it is random （chaotic）, while for the latter, a special memory function is introduced. Three of the numerous existing models are selected as examples. For each of the models, asymptotic （at t →∞） expressions are derived. In this way, the transients are filtered out and that which remains concerns the final behaviour of the models.

Numerical simulation of influence of the anomalies of theCentral-eastern Equatorial Pacific SST and Arctic seaice cover in summer on the atmospheric circulation

A series of numerical experiments have been conducted with a perpetual July, nine-level general circulation spectral model to determine the effect of variation of the Arctic sea ice cover extent and the joint effect of anomalies of both the Arctic sea ice cover and the Central-eastern Equatorial Pacific sea surface temperature on the summer general circulation. Results show that the two factors,anomalously large extent of the Arctic sea ice cover and anomalously warm sea surface temperature over the Central-eastern Equatorial Pacific Ocean, play substantially the equal role in the effect on the summer general circulation, and either of them can notably induce the atmospheric anomalies. The main dynamical processes determining the effect of the Arctic sea ice and the equatorial SST anomalies are associated with two leading teleconnection patterns, i. e. the Asia North/American and Eurasian patterns observed in atmosphere. The results presented in this paper again prove that the general circulation is fundamentally motivated by the non-uniform heating between the equator and the pole on the rotating earth.

Drought variability and its connection with large-scale atmospheric circulations in Haihe River Basin

Drought is one of the most widespread and devastating extreme climate events when water availability is significantly below normal levels for a long period.In recent years,the Haihe River Basin has been threatened by intensified droughts.Therefore,characterization of droughts in the basin is of great importance for sustainable water resources management.In this study,two multi-scalar drought indices,the standardized precipitation evapotranspiration index(SPEI)with potential evapotranspiration calculated by the PenmaneMonteith equation and the standardized precipitation index(SPI),were used to evaluate the spatiotemporal variations of drought characteristics from 1961 to 2017 in the Haihe River Basin.In addition,the large-scale atmospheric circulation patterns were used to further explore the potential links between drought trends and climatic anomalies.An increasing tendency in drought duration was detected over the Haihe River Basin with frequent drought events occurring in the period from 1997 to 2003.The results derived from both SPEI and SPI demonstrated that summer droughts were significantly intensified.The analysis of large-scale atmospheric circulation patterns indicated that the intensified summer droughts could be attributed to the positive geopotential height anomalies in Asian mid-high latitudes and the insufficient water vapor fluxes transported from the south.©2021 Hohai University.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Inferring of Organochlorine Pesticide Transmission under Atmospheric Circulation Impact

[ Objective] The study aims to infer the transmission of organochlorine pesticides under the influence of atmospheric circulation. [ Meth- od] A transmission profile of organochlorine pesticides was established in the region from the western margin of the Sichuan Basin to the western Si- chuan plateau, from which atmospheric particulate matter, atmospheric dry and wet deposition samples as well as corresponding soil samples were collected and analyzed. [ Result~ The study showed that HCHs content was the highest on the elevation boundaries of the study area, and,8-HCH content was the highest in the study area, indicating that there were no new HCHs input to the study area. In respect of HCHs content in the soil and atmospheric precipitation, it was significantly higher in low-lying areas than that of high-altitude areas. Besides, sources of organechlorine pesti- cides in high-altitude areas were mostly derived from atmospheric particulate matter and atmospheric dry deposition. A variety of factors affected the long-distance transmission of organochlorine pesticides, and the form of the atmospheric transport of organochlorine pesticides could be determined accurately based on the content of organochlorine pesticides in different media of each sample point. In different months, the sources of organechlo- rine pesticides in the atmospheric transmission varied with atmospheric circulation direction, so it could not be simply thought that organochlorine pesticides were transmitted from low-lying areas to high-altitude areas. Meanwhile, there was a transformation between the source and sink of or- ganochlorine pesticides in plateau areas because of atmospheric circulation changed. [ Condusionl The research could provide scientific references for the control of persistent organic pollutant diffusion and establishment of environmental protection measures. ds

Relation among Summer Rainfall in South Shandong and High Pressure in South Asia and Atmospheric Circulation

[Objective] The aim was to study the relation among summer rainfall in south Shandong and high pressure in South Asia and atmospheric circulation.[Method] Taking the precipitation in south Shandong along the Yellow River and Huaihe River,using the NCEP/NCAR data and summer rainfall data in south Shandong in summer from 1961 to 2005,the characteristics of high pressure in South Asia and atmospheric circulation in drought year and flood year in summer in south Shandong Province were expounded.The mechanism of 100 hPa pressure in South Asian influencing precipitation in south Shandong Province was discussed.The interaction of different equipment,different altitude and different system of atmosphere circulation in low and high layer was expounded.[Results] The first mode of EOF decomposition of precipitation in summer in south Shandong Province explained above 63% variances and reflected universal form of precipitation.The difference of central position of the central position of height field of high pressure in South Asia in drought and flood year was small.But the wind field center was inconsistent.As the area of SAH was smaller and its eastern ridge line stretched to the Western Pacific between the middle of south Shandong and Changjiang Estuary,flood summer occurred when there was an unusual cyclone lied in the east of 90° E and south of Lake Baikal.The area of SAH was larger and its eastern ridge line stretching to the Western Pacific over Changjiang Estuary,drought summer occurred,when there was an unusual anticyclone lied in the east of 90° E and south of Lake Baikal.SAH and summer rainfall also had close relationship with Tele-connection Patterns over the Eurasia continent and EAP Tele-connection.When the height anomaly was in '+-+' form in the north of the Caspian Sea,around Lake Baikal and Kamchatka,and when the height anomaly in East Asia-West Pacific area was in '-+' form from low altitude to high altitude,there was much precipitation in summer;and conversely,it was drought in summer in south Shandong.[Conclusion] It provided the oretical basis for summer rainfall in south Shandong.