Characteristics of Dry and Wet Climate in Shandong Province Based on Standardized Precipitation Index

Based on the monthly precipitation data of 116 meteorological stations in Shandong Province during 1970-2021,standardized precipitation index(SPI)was calculated,and the methods of linear fitting,mutation test and Morlet wavelet analysis were used to analyze the change trend and temporal and spatial distribution characteristics of SPI index in the past 52 years.The results show that there were more normal years in Shandong Province,and the frequency reached 38.46%.There was severe drought in the 1980s and more wet years after 2003.SPI index showed an upward trend in spring,summer and winter but a weak arid trend in autumn.In addition,intense dry weather was more frequent in summer.Spatially,the climate was normal or humid in most areas of Shandong Province.The regions with more wet years were located in the central and northeast Shandong and the peninsula,while the climate was normal in the southwest and north of Shandong.The areas with more dry years were mainly located in the northwest of Shandong Province.There was mainly local and global drought in Shandong Province,and the arid area showed a decreasing trend.In the past 52 years,Shandong Province experienced quasi-4 times of alternation between dry and wet climate.The long period of 21 a was the first main period,and the climate would be still wet in Shandong Province in the future.In terms of mutation,the climate in Shandong Province became humid after 2003,and 2003 was the mutation point.After the abrupt change,the climate changed from gradually drying to wetting.

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.

Analysis on the Evolution of Dry and Wet Degree in Benxi Area in Recent 57 Years

[Objective] The research aimed to analyze the evolution situation of dry and wet degree in Benxi area in recent 57 years.[Method] By using the annual,quarterly and monthly temperature and precipitation data in Benxi area during 1953-2009,the interdecadal variations of temperature,precipitation,dry and wet index were analyzed.[Result] The annual average temperature in Benxi area displayed the obvious increase trend,and the linear trend rate was 0.29 ℃/10 a.But the precipitation showed the obvious decrease trend,and the linear trend rate was-29.01 mm/10 a.The dry and wet index showed the decrease trend,and the linear trend rate was-33.61 mm/10 a,which closely related to the rise of temperature and the decrease of precipitation after the 1980s.[Conclusion] It showed the warming-drying development trend in Benxi area.

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.

Statistical Prediction of Wet and Dry Periods in theComahue Region (Argentina)

General features of rainy season with excess or deficits are analyzed using standardized precipitation index (SPI) in Limay and Neuquen River basins. Results indicate that most of dry and wet periods persist less than three months in both basins. Furthermore, an increase of rainfall variability over time is observed in the Limay river basin but it is not detected in the Neuquen river basin. There is a tendency for wet (dry) periods to take place in El Ni?o (La Ni?a) years in both basins. Rainfall in both basins, have an important annual cycle with its maximum in winter. In addition, possible causes of extreme rainy seasons over the Limay River Basin are detailed. The main result is that the behavior of low level precipitation systems displacing over the Pacific Ocean in April influences the general hydric situation during the whole rainy season. In order to establish the existence of previous circulation patterns associated with interannual SPI variability, the composite fields of wet and dry years are compared. The result is that rainfall is related to El Ni?o- Southern Oscillation (ENSO) phenomenon and circulation over the Pacific Ocean. The prediction scheme, using multiple linear regressions, showed that 46% of the SPI variance can be explained by this model. The scheme was validated by using a cross-validation method, and significant correlations are detected between observed and forecast SPI. A polynomial model is used and it little improved the linear one, explaining the 49% of the SPI variance. The analysis shows that circulation indicators are useful to predict winter rainfall behavior.

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.

Latitudinal patterns of climatic variables and influence of local topography on climatic variables in the dry valleys of southwestern China

Climate is a key factor to determine the pattern of ecosystems;however,the latitudinal patterns of climatic variables in the arid and semiarid areas remain largely unclear when compared to humid areas.The topography of the dry valleys of southwestern China plays an important role in the formation of climate.However,its impact on the climate remains qualitative.In this study,eight climatic variables from 12 meteorological stations were analyzed to explore their latitudinal patterns in the wet and dry seasons from 1961 to 2019.We also quantified the effects of local topography(RH10)on the climatic variables.The results were as follows:sunshine duration,total solar radiation,average temperature,and evaporation decreased significantly,and wind speed increased significantly with increasing latitude in the annual,wet,and dry seasons(P<0.001).Relative humidity and precipitation decreased significantly with increasing latitude in the wet season(P<0.001),and no obvious change pattern was observed in the dry season.Aridity index significantly decreased(toward dryness)with increasing latitude in the wet season and increased in the dry season(P<0.001).Wind speed had a significantly positive relationship with topography(RH10)(P<0.01),whereas precipitation and aridity index were negatively associated with topography in the wet season and positively associated with topography in the dry season.Dryness was positively associated with RH10 in the wet season,and negatively in the dry season.The results of our research could provide new perspectives for understanding the relationship between topography and drought in the dry valleys of southwestern China.

Responses of vegetation yield to precipitation and reference evapotranspiration in a desert steppe in Inner Mongolia,China

Drought,which restricts the sustainable development of agriculture,ecological health,and social economy,is affected by a variety of factors.It is widely accepted that a single variable cannot fully reflect the characteristics of drought events.Studying precipitation,reference evapotranspiration(ET_(0)),and vegetation yield can derive information to help conserve water resources in grassland ecosystems in arid and semi-arid regions.In this study,the interactions of precipitation,ET_(0),and vegetation yield in Darhan Muminggan Joint Banner(DMJB),a desert steppe in Inner Mongolia Autonomous Region,China were explored using two-dimensional(2D)and three-dimensional(3D)joint distribution models.Three types of Copula functions were applied to quantitatively analyze the joint distribution probability of different combinations of precipitation,ET_(0),and vegetation yield.For the precipitation–ET_(0)dry–wet type,the 2D joint distribution probability with precipitation≤245.69 mm/a or ET_(0)≥959.20 mm/a in DMJB was approximately 0.60,while the joint distribution probability with precipitation≤245.69 mm/a and ET_(0)≥959.20 mm/a was approximately 0.20.Correspondingly,the joint return period that at least one of the two events(precipitation was dry or ET_(0)was wet)occurred was 2 a,and the co-occurrence return period that both events(precipitation was dry and ET_(0)was wet)occurred was 5 a.Under this condition,the interval between dry and wet events would be short,the water supply and demand were unbalanced,and the water demand of vegetation would not be met.In addition,when precipitation remained stable and ET_(0)increased,the 3D joint distribution probability that vegetation yield would decrease due to water shortage in the precipitation–ET_(0)dry–wet years could reach up to 0.60–0.70.In future work,irrigation activities and water allocation criteria need to be implemented to increase vegetation yield and the safety of water resources in the desert steppe of Inner Mongolia.

Numerical Simulation of Pollutant Transport and Accumulation Areas in the Hangzhou Bay

Based on the COHERENS model (a coupled hydrodynamic ecological model for regional and shelf seas), a numerical hydrodynamic model of the Hangzhou Bay, influenced by tide, regional winds and freshwater from the Yangtze River and the Qiantangjiang River was established. The Lagrangian particle tracking was simulated to provide tracer trajectories. For convenience, the modeling area was divided into 8 subdomains and the modeling focused on March (dry season) and July (wet season). Numerical simulation and analysis indicate that the tracer trajectories originated in different subdomains are quite different. Most particles released in the mouth of the bay move outside the bay quickly and reach the farthest place at 122.5°E; while particles released in the inner part of the bay mostly remain in the same subdomain, with only minor migrations in two opposite directions along the shore. The tracer experiments also indicate that the northwest region of the bay is an area where pollutant can easily accumulate in both wet and dry seasons, and that the southeast region of the bay is another area for pollutant to accumulate in dry season because it is the main path for the contaminant.

Relationship between Nitrogen Atmospheric Deposition, Discharge and Concentration, and Monthly Change of Those in a River

The hypothesis that the product of discharge and concentration of nitrogen (N) in river water is equal to the atmospheric deposition was verified in the mountainous basin of the Tedori River in Japan. To verify this relationship, long-term data?are required to eliminate the effect of short-term variation of the N components. The basin has very high mountains, including Mount Hakusan (2702 maltitude), which is covered with deep snow in winter. Therefore, limited data were used for the estimation of the deposition of the entire basin by assuming a linear relationship of altitude. As a result, it was found that the estimated N concentration coincided well with observed concentrations at six sites—the Shiramine and Kuwajima (upper stream), Nakajima (lower stream) and Dainichi dam, Tedori dam and Senami sites (middle stream). The seasonal variation of N concentrations was low in the snowmelt period and high in autumn through to winter. This was not due to the larger discharge in snowmelt season as it was also found that N deposition was high in winter and low in spring, which indicated a clear relationship between N concentration and monthly atmospheric deposition including N storage in snow pack.

Interdecadal Variability of East Asian Summer Monsoon Precipitation over 220 Years (1777-1997)

In this study, long-term （1777–1997） precipitation data for Seoul, Korea, wetness indices from eastern China, and modern observations are used to identify the interdecadal variability in East Asian summer monsoon precipitation over the last 220 years. In the East Asian monsoon region, two long-term timescales of dry–wet transitions for the interdecadal variability and quasi-40-and quasi-60-year timescales are dominant in the 220-year precipitation data of Seoul, as well as in the wetness indices over China. The wet and dry spells between Seoul （southern China） and northern China are out-of-phase （out-of-phase） at the quasi-60-year timescale, and in-phase （out-of-phase by approximately 90 ？ before 1900 and in-phase after 1900） at the quasi-40-year timescale. In particular, during the last century, the dominant long-term timescales over East Asia tend to decrease from the quasi-60-year to the quasi-40-year with increasing time. The dominant quasi-40-year and quasi-60-year timescales of the Seoul precipitation in Korea are strongly correlated with these timescales of the northern Pacific Ocean.

Dissolved Organic Matter Features of Three Adjacent Eastern Mediterranean Urbanized Watersheds

Landscape urbanization broadly affects ecosystems in coastal watersheds, but, until now, the influence of nonpoint source urban inputs on dissolved organic matter (DOM) amount, composition, and source is poorly understood. To understand how DOM composition varied with urbanization, fluorescence excitation-emission matrices (EEMs) were determined for urban and non-urban waters from upstream to downstream sites along three adjacent coastal watersheds that flow into the Mediterranean Sea. Two humic DOM fluorescent components (humic-like and fulvic-like peaks) and two proteinic components (tyrosine-like and tryptophane-like peaks) were identified by EEM fluorescence. The results indicated that urbanization had an important influence on DOM concentration and composition, with urban waters having a high degree of DOM variation due to different land uses surrounding each body of water. Urban waters show a higher DOM fluorescence index (FI), the highest fluorescence intensity of protein-like manifested also by BIX values, and a lower value of the humification index (HIX) than non-urban waters which were dominated by allochthonous inputs. In addition, the EEM was compared in dry and wet season where higher DOM amounts and FI appeared in summer due to autochthonous production coming from algae growth compared to allochthonous input from rainfall dominated in wet season. The concentration of DOC increased from upstream to downstream for the three rivers, especially Beirut River. The increase in DOC values was observed in both dry and wet seasons by 39 and 19 times respectively compared to upstream (0.93 - 0.91 mgC/L).

CMIP5模式对我国西南地区干湿季降水的模拟和预估

利用降水观测资料,评估了参加国际耦合模式比较计划第五阶段（CMIP5）的34个全球模式对1986～2005年我国西南地区干湿季降水的模拟能力.结果表明,34个CMIP5模式中分别有30和25个模式模拟的干季和湿季降水偏多.34个模式对我国西南地区干湿季降水的模拟能力差异较大,大约半数模式的模拟值与观测值的空间相关系数通过了99％的信度检验,且标准差之比小于2.利用两个技巧评分标准,分别挑选出了对干湿季降水模拟最优的9个模式.最优模式集合平均结果要优于34个模式的集合平均,更要优于大多数单个模式.进一步利用最优的9个模式的集合平均对RCP4.5和RCP8.5两种典型浓度路径下我国西南地区干湿季降水的变化进行了预估.相对于1986～2005年气候平均态,在21世纪初期（2016～2035年）,我国西南地区干季降水变化表现为川西高原降水增多,而四川盆地及攀西地区、重庆、贵州和云南的大部分地区降水减少;湿季降水变化表现为川西高原、贵州和广西大部分地区降水增多,而四川盆地及攀西地区和云南降水减少.在21世纪中期（2046～2065年）和末期（2080～2099年）,西南地区干湿季降水普遍增多.在RCP8.5情景下,降水的变化幅度要强于RCP4.5情景.

基于GPS技术的高原与平原地区可降水量的研究

为了更深入地分析高原及平原地区多变的降水气候,利用2004年中国地壳运动观测网络GPS数据及高原和平原地区的大气压等资料,整体地分析了两类地区上空可降水量的变化及其差异。结果表明,高原地区和平原地区的可降水量有明显的地区性及季节性变化。

东北帽儿山地区生长季大气氮湿沉降动态变化

利用雨量器收集降雨样品的方法,研究了帽儿山地区大气氮湿沉降的浓度、沉降量及其动态变化规律。研究结果表明:2011年随降雨输入到该地区的大气氮沉降量为19.16 kg·hm-2,其中,NH+4-N、NO-3-N和溶解有机氮(DON)输入量分别占湿沉降量的52%、26%和22%,NH+4-N/NO-3-N沉降量接近2.0。降雨中NH+4-N对当地大气氮湿沉降输入量的贡献率最大,其平均浓度为1.59 mg·L-1。氮湿沉降浓度存在明显的季节差异,以5和9月氮浓度最高,7月最低。该区NH+4-N、NO-3-N和总氮(TN)湿沉降输入量与降雨量均存在极显著正相关,决定系数分别为0.65、0.63和0.76,而DON输入量与降雨量相关性交差(P>0.05),其决定系数为0.24。

甘肃河西走廊地区气候暖湿转型后的最新事实

应用1981-2011年甘肃省河西走廊地区19台站逐日降水资料,研究了该区域年和四季降水量、雨日、降水强度的气候变化特征.结果表明:整个河西走廊秋季及酒泉市东部到张掖市冬季降水呈显著增加;夏季雨日显著减少,秋季雨日显著增加;秋季降水强度普遍增强.与1990年代相比,2000年代秋季、春季和冬季降水量占年降水量的比重分别提高了9.4%、3.9%和1.8%,仍有暖湿化倾向,其中,秋季暖湿化显著,而夏季降水比重却减少了15.3%,有暖干化趋势.2000年代降水量、雨日和降水强度极端气候事件明显增加:从季节看,秋季发生频率最高,约占同季全部极端事件的80%左右,其次是夏季和冬季,各占60%,春季和年各占50%;从要素看,雨日发生频率最高,占全部极端事件的近70%,降水量次之,占60%,雨强占50%.与1990年代相比,2000年代500 hPa、200 hPa和700 hPa高度场、相对湿度及比湿有明显的年代际变化,对秋季降水有利而对夏季降水不利.

地形对青藏高原丰枯水年雨季降水量空间分布的影响

采用高分辨率的3″数字高程模型及青藏高原东部102个常规气象观测站5～9月份的降水量资料,根据降水随高度分布将站点分为三类,再采用多元逐步回归的方法,建立了青藏高原40年(1961-2000年)逐年雨季降水量与经度、纬度、海拔、坡度、坡向、开放度等6个地理、地形因子关系模型,并以此为基础,分析了三类区域在丰枯水年里的因子系数的变化规律。结果表明,此法建立的关于高原降水量与诸因子之间方程的相关性显著,相对误差20%,平均相对误差4.4%,估算模型的相关系数均通过0.05的显著性检验;海拔低于1 400 m的第一类区域,主要受地形高度和开放度等局地地形的影响,来改变旱涝年的降水分布特征,海拔高度大于3 600 m的第三类区域,主要受开放度和坡度的影响,其他区域主要受地形的海拔、经度和开放度等局地地形的影响;高原季风是影响第三类区域水汽分布的主要因素,在季风加强时,开放度和经度的影响也随着加强,而坡度和海拔的影响减弱,从而使得水汽的局地性分布特征增强,东西分布差异加大,相应地局地降水分布特征加强,东西差异加大。地理地形因子影响大气的水汽输送和大气的垂直运动,从而导致其对空间降水分配的差异。

黄土区生态建设对流域不同水体转化影响

生态建设治理能够显著改变流域下垫面条件,研究黄土区生态建设治理对流域不同水体转化特征对深刻了解该区域生态建设恢复具有重要意义。该研究运用稳定同位素技术,通过野外采集生态建设治理对比流域不同水体水样样品,分析不同水体氢氧同位素特征,揭示不同季节生态建设治理对流域不同水体转化影响。结果显示:生态建设治理流域韭园沟降水同位素较生态建设未治理流域裴家峁降水同位素贫化。降水同位素变幅大于河水和井水同位素变幅,河水蒸发分馏作用强烈而井水较为稳定。河水、井水和水库水的补给来源主要是降水。生态建设流域雨季同位素值偏低而旱季同位素值偏高,分别与降水量和温度呈正比和反比关系。沿着主沟道流程,韭园沟流域和裴家峁流域河水同位素值呈逐渐富集趋势。旱季,韭园沟流域和裴家峁流域都表现为降水和井水补给河水,补给比例分别为24.66%、75.34%和83.81%、16.19%。雨季,韭园沟流域和裴家峁流域都表现为降水和河水补给井水,补给比例分别为14.75%、85.25%和48.06%、51.94%。表明生态建设显著改变了流域生态水文过程,旱季和雨季不同水体间的相互转化过程以及转化比例发生改变。该研究可为黄土高原生态建设对流域生态水文过程影响研究和生态环境建设保护提供科学依据。

我国西南地区干湿季降水的主模态分析

利用我国西南地区26个台站降水资料，通过经验正交函数（EOF）分解的方法，分析了1980~2009年该地区干季（10～4月）和湿季（5～9月）降水的主模态。我国西南地区干季降水的时空变化存在两种主模态，它们分别可以解释总方差的22．4％和15．6％。第1主模态为全区一致型，具有准两年周期振荡的年际变化特征；第2主模态为东南一西北反向型，从20世纪90年代中期至21世纪初呈现2～3年的变化周期。我国西南地区湿季降水的时空变化存在三种主模态，它们分别可以解释总方差的17．1％，13．8％和11．1％。第1主模态为全区一致型，20世纪90年代初期具有较强的2～4年周期；第2主模态为经向偶极子型分布，并具有显著的4年周期；第3主模态为纬向偶极子型分布，具有2～4年的年际变化信号。进一步利用NCEP／NCAR再分析资料以及美国国家海洋和大气管理局（NOAA）的海表面温度（SST）资料，通过合成分析和回归分析的方法探讨了与干湿季降水各主模态对应的大尺度大气环流和海温状况。我国西南地区干季降水第1主模态与北极涛动（AO）有明显的正相关关系，对应的大气环流和海温状况表现为高纬北冰洋与中纬度地区上空高度场的反向异常分布，北大西洋和北太平洋海温低纬与中高纬的偶极子型异常分布；第2主模态与中高纬欧亚大陆上空高度场经向偶极子型异常分布有关，中纬度北太平洋的海温异常与该模态具有紧密的联系。我国西南地区湿季降水第1主模态与北大西洋涛动（NAO）显著负相关，对应的大气环流和海温状况表现为北大西洋上，高纬度与中纬度地区上空高度场的偶极子型异常分布，海温从低纬到中高纬的三极子型异常分布；第2主模态受欧亚大陆上空高度场经向三极子型异常分布影响，并与北太平洋海温异常的一致型分布有关；第3主模态可能与E1 Nifio Modoki有关，同时受到南亚高压的影响，赤道太平洋海温的纬向三极子型异常分布对该模态具有一定的潜在预报意义。

青藏高原东南侧干湿季气候特征与成因

利用台站降水、蒸发资料和NCEP再分析资料，通过季节水汽输送、大气可降水量分布、水汽辐合辐散诊断对西南水汽通道上青藏高原东南侧干、湿季气候特征及成因进行了分析。结果显示，四季青藏高原东南侧均存在西南水汽输送，即使冬、春季也有较强盛的水汽输送，但其上空四季均维持有水汽辐散场，不利于降水发生和维持，尤其冬、春季强度更强、范围更广。同时，受低纬高原地形影响，这一地区大气气柱短，导致青藏高原东南侧大气可降水量比周边地区明显偏少，且存在明显的季节变化，冬、春季大气可降水量仅为夏季的1/3~1/2。可见，青藏高原东南侧季节性干旱受冬、春季大气可降水量的减少和其上空更强更广的水汽辐散场共同影响所致。