Precipitation Changes in Wet and Dry Seasons over the 20th Century Simulated by Two Versions of the FGOALS Model

Seasonal precipitation changes over the globe during the 20th century simulated by two versions of the Flexible Global Ocean-Atmosphere-Land System （FGOALS） model are assessed. The two model versions differ in terms of their AGCM component, but the remaining parts of the system are almost identical. Both models reasonably reproduce the mean-state features of the timings of the wet and dry seasons and related precipitation amounts, with pattern correlation coefficients of 0.65-0.84 with observations. Globally averaged seasonal precipitation changes are analyzed. The results show that wet sea- sons get wetter and the annual range （precipitation difference between wet and dry seasons） increases during the 20th century in the two models, with positive trends covering most parts of the globe, which is consistent with observations. However, both models show a moistening dry season, which is opposite to observations. Analysis of the globally averaged moisture budget in the historical climate simulations of the two models shows little change in the horizontal moisture advection in both the wet and dry seasons. The globally averaged seasonal precipitation changes are mainly dominated by the changes in evaporation and vertical moisture advection. Evaporation and vertical moisture advection combine to make wet seasons wetter and enhance the annual range. In the dry season, the opposite change of evaporation and vertical moisture advection leads to an insignificant change in precipitation. Vertical moisture advection is the most important term that determines the changes in precipitation, wherein the thermodynamic component is dominant and the dynamic component tends to offset the effect of the thermodynamic component.

Decadal Changes in Dry and Wet Heatwaves in Eastern China:Spatial Patterns and Risk Assessment

Under global warming,understanding the long-term variation in different types of heatwaves is vital for China’s preparedness against escalating heat stress.This study investigates dry and wet heatwave shifts in eastern China over recent decades.Spatial trend analysis displays pronounced warming in inland midlatitudes and the Yangtze River Valley,with increased humidity in coastal regions.EOF results indicate intensifying dry heatwaves in northern China,while the Yangtze River Valley sees more frequent dry heatwaves.On the other hand,Indochina and regions north of 25°N also experience intensified wet heatwaves,corresponding to regional humidity increases.Composite analysis is conducted based on different situations:strong,frequent dry or wet heatwaves.Strong dry heatwaves are influenced by anticyclonic circulations over northern China,accompanied by warming SST anomalies around the coastal midlatitudes of the western North Pacific(WNP).Frequent dry heatwaves are related to strong subsidence along with a strengthened subtropical high over the WNP.Strong and frequent wet heatwaves show an intensified Okhotsk high at higher latitudes in the lower troposphere,and a negative circumglobal teleconnection wave train pattern in the upper troposphere.Decaying El Niño SST patterns are observed in two kinds of wet heatwave and frequent dry heatwave years.Risk analysis indicates that El Niño events heighten the likelihood of these heatwaves in regions most at risk.As global warming continues,adapting and implementing mitigation strategies toward extreme heatwaves becomes crucial,especially for the aforementioned regions under significant heat stress.

Hydraulic and volume change behaviors of compacted highly expansive soil under cyclic wetting and drying

The wide engineered application of compacted expansive soils necessitates understanding their behavior under field conditions.The results of this study demonstrate how seasonal climatic variation and stress and boundary conditions individually or collectively influence the hydraulic and volume change behavior of compacted highly expansive soils.The cyclic wetting and drying(CWD)process was applied for two boundary conditions,i.e.constant stress(CS)and constant volume(CV),and for a wide range of axial stress states.The adopted CWD process affected the hydraulic and volume change behaviors of expansive soils,with the first cycle of wetting and drying being the most effective.The CWD process under CS conditions resulted in shrinkage accumulation and reduction in saturated hydraulic conductivity(k sat).On the other hand,CWD under CV conditions caused a reduction of swell pressure while has almost no impact on k sat.An elastic response to CWD was achieved after the third cycle for saturated hydraulic conductivity(k sat),the third to fourth cycle for the volume change potential under the CV conditions,and the fourth to fifth cycle for the volume change potential under the CS conditions.Finally,both swell pressure(s s)and saturated hydraulic conductivity(k sat)are not fundamental parameters of the expansive soil but rather depend on stress,boundary and wetting conditions.

THE WET-DRY CHANGES IN RECENT 40YEARS IN TAKLIMAKAN AREA

Using the precipitation data in recent 40 years of 48 meteorological stations in Taklimakan area and neighboring areas, this paper analyzes the stage and periodicity of the wet-dry changes in a year and four seasons. The paper also compares the correlativity of precipitation between Taklimakan area and around Mountains, and obtained some statisticconclusions as follows. (1) The precipitation changes of a year and four seasons in Taklimakan area have different wet-dryperiods and change periodicities. (2) Summer precipitation has well directive sense to annual precipitation in Taklimakanarea with a correlation coefficient 0. 901, and the negative correlation between precipitation and temperature in summer isvery remarkable. (3) There is definite correlation between annual precipitation in Taklimakan area and position of polarvortex. When longitude of polar vortex is partial west in February and its latitude is partial north in September of the lastyear, annual precipitation is above its mean in the area. In addition, it is beneficial to obtain more summer precipitation inthe area when position of polar vortex is partial west in February.

Characteristics of Temperature Change in China over the Last 2000 years and Spatial Patterns of Dryness/Wetness during Cold and Warm Periods

This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3℃ and 0.7℃, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56°± 0.42℃（100 yr）^（-1）; however, temperatures recorded in the 20 th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern： dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20 th century warming can primarily be attributed to a mega El Nino–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.

Multiscale characteristics of the wetting deformation of Malan loess in the Yan’an area,China

Loess is prone to collapse upon wetting due to its open metastable structure,which poses a considerable threat to the environment,construction processes and human life.In this study,double oedometer tests and scanning electron microscopy and mercury intrusion porosimetry analyses were conducted on loess from Yan’an to study the macroscopic and microscopic characteristics of loess wetting deformation and the underlying mechanism.The wetting collapse of loess under loading depends on the changes in different microstructure levels and elements.This collapse chain reaction is manifested by the dissipation,scattering and recombination of the cementation,deformation and reorganization of the particles,blocking of the pore channels,decrease in the dominant size and volume of unstable macropores(>14μm)and abundant mesopores(2.5-14μm),increase in the volume of small pores(0.05–2.5μm),and volume contraction at the macroscale.This process is dependent on the initial water content,stress level and wetting degree.These findings can facilitate collapsible loess hazard prevention and geological engineering construction.

Analysis on the daily courses of water potential of nine woody species from Cerrado vegetation during wet season

The water potential (Ψ) daily courses of 9 woody species from Cerrado vegetation in different weather conditions during wet season were observed and analyzed. The adjusting strategies of 9 species could be divided into 3 groups according to Cluster Analysis and based on the data observed on the January 18, March 20 and April 6. The Ψ values of the first group, which included 2 species, were maintained at the higher level consistently. The Ψ values of the second group, which included 5 species, were intermediate level. The Ψ values of the third group, which included 2 species, were kept in the lower level. The Ψ values of all species always kept pace with the weather condition, especially water condition. During the clear day only one Ψ value peak for all species occurred at midday (12∶30–13∶30). When the overcast or raining occurred for a short period, the fluctuation of Ψ values would appear after about 15–30 min responding to the change of weather condition. Even in the same group under the same external circumstance, there was a clear variation of the leaf Ψ values among different species, which showed that the strategy diversity for plant to balance water relation. From January to April, the Ψ values of 9 species reduced in response to the drought condition. The species with the lower values of water saturation deficiency at turgid loss point (W sdtlp) the osmotic potential at saturation (πsat), the osmotic potential at turgid lose point (πtip) or lower predawn water potential (Ψpd) usually had the lower Ψ values at midday. The mechanism of water balance controlled by many systems has been assumed.

Investigation on microstructure evolution of clayey soils: A review focusing on wetting/drying process

Variability in moisture content is a common condition in natural soils.It influences soil properties significantly.A comprehensive understanding of the evolution of soil microstructure in wetting/drying process is of great significance for interpretation of soil macro hydro-mechanical behavior.In this review paper,methods that are commonly used to study soil microstructure are summarized.Among them are scanning electron microscope(SEM),environmental SEM(ESEM),mercury intrusion porosimetry(MIP)and computed tomography(CT)technology.Moreover,progress in research on the soil microstructure evolution during drying,wetting and wetting/drying cycles is summarized based on reviews of a large body of research papers published in the past several decades.Soils compacted on the wet side of op-timum water content generally have a matrix-type structure with a monomodal pore size distribution(PSD),whereas soils compacted on the dry side of optimum water content display an aggregate structure that exhibits bimodal PSD.During drying,decrease in soil volume is mainly caused by the shrinkage of inter-aggregate pores.During wetting,both the intra-and inter-aggregate pores increase gradually in number and sizes.Changes in the characteristics of the soil pore structure significantly depend on stress state as the soil is subjected to wetting.During wetting/drying cycles,soil structural change is not completely reversible,and the generated cumulative swelling/shrinkage deformation mainly derives from macro-pores.Furthermore,based on this analysis and identified research needs,some important areas of research focus are proposed for future work.These areas include innovative methods of sample preparation,new observation techniques,fast quantitative analysis of soil structure,integration of microstructural parameters into macro-mechanical models,and soil microstructure evolution charac-teristics under multi-field coupled conditions.

Study on potential evapotranspiration and wet-dry condition in the seasonal frozen soil region of northern Tibetan Plateau

This study was based on the CEOP/CAMP-Tibet observed data at AWS （Automatic Weather Station） of MS3478 in the seasonal frozen soil region of northern Tibetan Plateau from March 2007 to February 2008. The variation characteristics of PE （potential evapotransph＇ation） were analyzed based on the Penman-Monteith method recommended by FAO （the Food and Agriculture Organization of the United Na- lions）. The contributions of dynamic, thermal and water factors to PE were discussed, and the wet-dry condition of the plateau region was further studied. The results indicated that daily PE was between 0.52 mm and 6.46 mm for the whole year. Monthly PE was over 107 mm from May to September, but decreased to less than 41 mm from November to February. Annual PE was 1,037.8mm. In the summer, thermal PE was significantly more than dynamic PE, but conversely in the winter. Annual variation of thermal PE was of sine wave pattern. In addition, drought and semi-drought climate lasted for a long time while semi-humid climate was short. The effect of water and dynamic factors on PE varied considerably with the seasons. Annual variation of thermal PE was of sine wave pattern.

Seasonal characteristics of Carex lasiocarpa biomass and nutrient accumulation in the typical wetland of Sanjiang Plain, China

Seasonal dynamics of above- and belowground biomass and nutrient characteristics （nitrogen, carbon, and phosphorus） of Carex lasiocarpa were investigated in the typical wetland of Sanjiang Plain, China from May 2007 to September 2008. The results show that the changes of aboveground biomass during the growing season are best described by the twice function curve model, whereas the changes of belowground biomass follow the exponential increase curve model. Both the organic carbon contents in the above- and belowground plant parts show significant positive linear correlations with the growing time, and the coefficients R2 are 0.983 and 0.746, respectively. The carbon accu-mulations of the above- and belowground plant parts during the growing season show the same dynamics as those of the biomass. However, the nitrogen contents and accumulation in C. lasiocarpa aboveground and belowground parts show exponential increase during the growing season. The dynamics of C. lasiocarpa phosphorus contents follows the twice function curve model, whereas the accumulation of phosphorus shows the linear increase. The ratios of C/N in different parts of C. lasiocarpa fit the negative linear relations with total nitrogen content in the growing season. Moreover, the ratios of C/P in C. lasiocarpa plant also fit the negative linear relations with total phosphorus content. The results show that nitrogen is the primary limiting nutrient for C. lasiocarpa growth as compared with carbon and phosphorus.

Water relations balance parameters of 30 woody species from Cerrado vegetation in the wet and dry season

The water relations balance parameters of plant tissue have been determined under field condition.They are the osmotic potentials at saturation (nsat), the osmotic potentials at the turgid loss point (ntlp), modulusof elasticity and the water saturation deficiency at turgid loss point (Wsdtlp) of 30 adult woody species fromCerrado vegetetion (neotropical savanna) in the wet and dry seasons of Brazil. And the changing patterns of Sevalues of each species have been compared and analyzed in different methods. The mean values of nsat, ntlp, and Wsdtlp of 30 species in the wet season were -2.11 MPa, -2.50 MPa, 19.66 MPa and 10.27 % respectively.Responding to water stress in the dry season, the values of nsat of 24 species, the ntlp and the of 17 speciesthe Wsdtpl of 6 species significantly went down or up comparing with those in the wet season (P < 0.05)- Only 3species had not changed their water parameters significantly any more. The mean values of nsat, ntlp, andWsdtlp of 30 species were adjusted to be -2.28 MPa, -2.84 MPa, 18.58 MPa and 8.19 % respectively. The species that have lower values on the mt have higher vaIues on e. Contrary, the specles that have higher valueson the nsat have lower values on . The special strategies of 30 Cerrado species have been divided. into 3 typesin Cluster Analysis Method. Every type has the distinct water balance mechanism and the parameter-adjustingpattern.

Temporal Microbial Response to Wetting-Drying Cycles in Soils within and Outside the Influence of a Shrub in the Sahel

Piliostigma reticulatum is a native woody shrub found in cropped fields in the Sahel and has been shown to increase crop productivity and soil quality. Frequently occurring drying and rewetting cycles (DRW) may alter the soil quality beneath these shrubs. We investigated the effect of DRW cycles on microbial community in soil beneath and outside the P. reticulatum canopy and the roles of this shrub in the adaptation of the microbial community to abiotic stress. Soils were incubated in a climate controlled chamber for 45 days, after exposure to 10 consecutive days of DRW cycles at 75% of water holding capacity (WHC). Basal respiration, β-glucosidase activity, microbial biomass carbon (MBC), and available nitrogen (;) were measured at 2, 30, and 45 days after soil exposed to the DRW cycles. MBC increased significantly two days after the DRW cycles and was greater for soil beneath the shrub canopy compared with soil outside the shrub canopy. PCA analysis based on basal respiration, microbial biomass carbon, available nitrogen, and β-Glucosidase activity resulted in a tight clustering in the beneath shrub soil samples. Soils incubated for more than 30 days after DRW cycles had higher available nitrogen content than soils incubated for less than 30 days. Soil from beneath the shrub canopy significantly improved soil resilience based on β-glucosidase activity. Soil from beneath the shrub canopy also had higher nutrient levels and greater microbial activity even when subjected to DRW cycles, potentially improving the ability of crops to withstand in-season drought when they are adjacent to shrubs. The work should bring our scientific community into a more comprehensive assessment of potential effects of a crop-shrub intercropping that may allow for increased crop yields in semi-arid ecosystems under drought conditions.

Development of High Yielding Aromatic Rice Variety BRRI dhan70 for Wet Season of Bangladesh

BRRI dhan70 is a new aromatic, high yielding and extra-long slender grain containing transplanted Aman rice variety which is an improvement over existing premium quality rice BRRI dhan37. BRRI dhan70 has pleasingly passed in the proposed variety trial conducted in the farmers’ field. As a result National Seed Board (NSB) approved this variety for commercial cultivation in the wet season (T. Aman) of Bangladesh in 2015. The important feature of BRRI dhan70 is the straw colored extra-long slender, higher elongation ability and aroma of the cooked rice. The growth duration of BRRI dhan70 is 130 days which is 10-15 days earlier growth duration than BRRI dhan37. Thousand grain weight of the variety is 20 gm and it has colored grain tip and pointed awn. The rice has 21.7% amylose content with 9.5% protein content. The special character of the variety is lodging tolerance. It has long, erect deep green flag leaf. BRRI dhan70 can produce 4.8-5.0 t/ha yield with proper management which is approximately 1.0-1.35 t/ha higher yield than BRRI dhan37. The exportable aromatic rice BRRI dhan70 is an excellent variety for cultivating in the wet (T. Aman) season and farmers can be benefited by the cultivation of BRRI dhan70.

Wet and Dry Season Effects on Select Soil Nutrient Contents of Upland Farms in North Bank Region of the Gambia

The study was conducted in three villages of North Bank Region of the Gambia in 2013 and 2014. We examined wet and dry season effects on select soil nutrient contents of upland farms in North Bank Region of the Gambia. The objective was to evaluate changes in soil nutrient contents in both wet and dry seasons. Soil samples were collected from three RCBD upland fields with three replications at a depth of 0 - 15 cm and analyzed for pH, Soil Organic Carbon (SOC), and soil moisture content. The gravimetric method of moisture estimation was used. The results showed that soil moisture content, soil TN, and soil pH are significantly different (P < 0.05) during the two seasons. There was no significant difference in SOC between the two seasons in the study area. The study concluded that soil nutrients were more readily available during the wet season than during the dry season probably because there is more soil moisture available in the wet season that facilitates soil nutrient release. The study concludes that soil moisture has to be available in order for some select soil nutrients to be released for plant uptake.

Transformation and mechanisms of climate wet/dry change on the northern Tibetan Plateau under global warming:A perspective from paleoclimatology

The northern Tibetan Plateau is a climatically sensitive zone influenced by monsoon and westerly winds.In summer,water vapor transport can reach Qinghai Lake and the eastern section of the Qilian Mountains;in winter,westerly winds mainly control the climate.This article compares the wet/dry changes in the region during the mid-Holocene(MH)warm period,the medieval climate anomaly(MCA),the current warm period(CWP),and the future warm period from the perspective of paleoclimate.We found that the MH warm period was mainly affected by the orbit-controlled East Asian summer monsoon,and the region showed warm and humid climate characteristics.The MCA was mainly controlled by solar radiation,and there was a warm and dry phenomenon.The CWP and the future warm period are mainly controlled by the rise in temperature caused by the increase in greenhouse gases,and the climate is becoming more arid.The wet/dry patterns in the CWP and the future warm period in the next century on the northern Tibetan Plateau are similar to those in the MCA.Continued warming will lead to the expansion of the westerly belt and a gradually humid climate.The future wet/dry changes will be more similar to the MH warm period.

Dry/Wet Changes and Their Standing Characteristics in China During the Past 531 Years

Time series of the dryness-wetness（DW） index of 531 yr（AD 1470-2000） at 42 stations in regions A（most of North China and the east of Northwest China） and B（the Yangtze-Huaihe River valley） in China are applied to investigating the historical DW characteristics over various periods of the series with a relatively stationary average value using Bernaola-Galvan（BG） algorithm.The results indicate that region A/B underwent three drought-intensive periods（DIP;1471-1560,1571-1640,and 1920-2000/1501-1540,1631-1690,and 1911-1960） in the last 531 years.In the DIP of the last 130 years,the frequency of DW transition has increased in region A,but not obviously changed in region B in comparison with the other two historical DIPs.The dry period started in about 1920 in region A with severe drought events occurring from the late 1970s to the early 1980s.It lasted for about 50-70 yr in this century,and then a DW shift took place.The wet period in region B might maintain for the coming several decades.The variations of DW in region A are positively correlated with changes in temperature,but in region B,the correlation with temperature is weaker.It is found that the number of DW indices of various categories within a running window is an exponential function of the running window length.The dryness scale factor（DSF） is defined as the reciprocal of the characteristic value of the exponential distribution,and it has a band-like fluctuation distribution that is good for the detection of extreme drought（flood） clustering events.The results show that frequencies of the severe large-scale drought events that concurrently occurred in regions A and B were high in the late 12th century,the early 13th century,the early 17th century,and the late 20th century.This provides evidence for the existence of the time-clustering phenomena of droughts（floods）.

Long-Term Changes in Summer Extreme Wet Bulb Globe Temperature over China

The wet bulb globe temperature(WBGT)has important implication for human health.Previous studies widely use the monthly data but rarely investigate the extreme WBGT because of data limitation.In this study,we use 6-h station data to analyze the changes in the WBGT and three categories(intensity,absolute threshold,and frequency indices)of extreme WBGT indices in summers of 1961-2017.It is found that the spatial distributions of long-term trends in summer mean WBGT are consistent with those in the mean temperature.The trend value of WBGT is smaller than the mean temperature,because of the decrease of relative humidity.For the extreme indices,the intensity and frequency of WBGT and fixed threshold indices have changed.The increase of intensity indices and warm WBGT days and nights,and decrease of cold WBGT days and nights have been observed in most China,especially over northwestern China.The number of days with daily maximum WBGT exceeding 31.4℃(WXge31)and minimum WBGT exceeding 27.9℃(WNge27)over southeastern China have increased since 1961.The spread of probability distributions of WXge31,WNge27,and warm WBGT days and nights is becoming wider,reflecting increased variability of extreme indices.In addition,urbanization effects on the WBGT are investigated.The impacts of urbanization on most of extreme WBGT indices are not detected,except for absolute thresholds indices.This may be due to the decrease of relative humidity in urban stations,which are almost two times larger than that in rural stations.However,we also note that the homogenization issue of humidity data may affect the conclusions.

Environmental factors controlling soil warming and wetting during 2000-2020 in permafrost and non-permafrost regions across the Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau(QTP)has experienced rapid environmental changes,including climate warming and wetting,since the 1980s.These environmental changes significantly impact the shallow soil hydrothermal conditions,which have key roles in land-atmosphere feedback and ecosystem functions.However,the spatial variations and responses of soil hydrothermal conditions to environmental changes over the QTP with permafrost(PF)and seasonal frost(SF)remain unclear.In this study,we investigated the spatial variations in soil temperature(ST)and soil moisture(SM)changes over the QTP from 2000 to 2020 using 99 in-situ sites with observations at 4 depths(i.e.10,40,100 and 200 cm).The main environmental controlling factors were further identified using a calibrated statistical model.Results showed that significant(p<0.05)soil warming occurred at multiple soil layers during 2000-2020 with a wide variation(i.e.0.033-0.039℃ per year on average),whereas the warming rates at PF sites were two times greater than those at SF sites.In addition,the soil wetting rate was high over the SF region,whereas the soil wetting rate was low over the PF region.Aside from air temperature,changes in thawing degree days and solar radiation(Srad)contributed most to soil warming in the PF region,whereas changes in rainfall,Srad and evaporation(EVA)have been identified as the key factors in the SF region.As for soil wetting,changes in snowfall,freezing degree days and vegetation have noticeable nonlinear effects over the PF region,whereas changes in EVA,Srad and rainfall highlighted distinct linear and nonlinear effects in the SF region.These findings enhance our understanding of the hydrothermal impacts of future environmental changes over the QTP.

Research for length change of four seasons over China in recent 47 years

Using daily temperature data from 599 Chinese weather stations during 1961-2007, the length change trends of four seasons dur- ing the past 47 years were analyzed. Results show that throughout the region, four seasons＇ lengths are： spring becomes shorter （-0.8 d/10yrs）, summer becomes longer （3.2 d/10yrs）, autumn （-0.5 d/10yrs） and winter （-1.6 d/10yrs） becomes shorter. This trend is different in spatial distribution, namely it is very obvious in northern than southern China, and also remarkable in eastern than western China. Summer change is most obvious, but autumn has little change comparatively. This trend is highly obvious in North, East, Central and South China. In the Southwest starting in the 21st century, summer becomes longer and winter shortens. The trend in the Plateau region since the 1980s is that spring becomes longer and winter shortens. The average annual temperature increased during the past 47 years, and the change of the average annual temperature precedes seasons＇ length. Thus, the average annual temperature has a certain influence on the length change of seasons.

Changes in the Beginning Date and Duration of the Four Seasons in Zhejiang Province

Based on data of daily average temperature from 62 national ground observation stations in Zhejiang Province during 1971-2015,the changing trends and spatial distribution of beginning date and duration of the four seasons in Zhejiang Province were analyzed by using the least square method,and significance test was conducted by using correlation coefficient. The results show that according to the changing characteristics of the four seasons in Zhejiang Province,autumn and winter began later,while spring and summer started earlier than before; the duration of summer lengthened,while the duration of winter shortened,and there were great changes in summer and winter but small changes in spring and autumn. Seen from the spatial distribution of beginning date and duration of the four seasons,the correlation in middle and northern Zhejiang was better than that in southern Zhejiang.