近40年内蒙古候降水变化趋势

基于1964—2003年内蒙古44个站日降水量数据,进行了前20年(1964—1983年)、后20年(1984—2003年)候降水变化的聚类分析,得到了最佳聚类数和各聚类的台站组成及其空间分布情况,对前20年和后20年候降水中值的变化情况、候最大降水量出现时间、各聚类的整体特征等进行了分析,并进行了候(5 d)和11 d降水中值极图的对比。结果表明:内蒙古不同地区的候降水变化格局存在经向地带性,但站点海拔的差异使这种地带性有所模糊;前、后两个20年候降水的变化格局较为复杂,大多数站点在一些候降水有显著变化,既有降水显著增加的候,也有降水显著减少的候;候最大降水出现的时间和量值有一定变化。

基于前期海温异常的宁夏5～9月候降水量客观预测方法及检验评估

利用宁夏1981-2014年降水资料,通过相关分析,发现与宁夏降水关系较好的主要是赤道太平洋、印度洋、北大西洋及西太平洋海温,其关键的影响时段为5月各候、6月第3候、8月1-3候、9月4-6候。利用多元回归方法,建立基于前期海温异常的候降水量客观预测模型。总体看来,模型对宁夏引黄灌区和南部山区拟合效果好于中部干旱带,对5月、8月、9月拟合效果最好。模型对各区域候降水量≥10 mm的准强降水过程预测,总体评分高于＂异常相似释用预测方法＂;南部山区预测效果最好,引黄灌区预测能力较弱;从各月看,6月和9月的预测准确率相对较高,5月预测准确率最低。模型对引黄灌区候降水量≥5 mm的过程预测,6月效果最好。利用模型预测的2014年5-9月各站准强降水过程,ZS评分高于实时发布的业务产品。

阿图什地区候气温、候降水的气候分析

利用阿图什1960年-1990年共31年的气温、降水资料,从不同的角度阐述和分析了本地候气温、候降水的气候统计特征.

广东候降雨量的相关性和降水区划

用３种方法计算了广东候降水相关性，发现用候降水量距平计算的相关系数能较科学划分广东区域降水区划；西江流域与东江流域及沿海地区各有较好的降水正相关，同时降水可能性大，易致洪涝；北江降水相关性差，应多设测点．同时指出，气候平均降水的相关概率不宜用于预报．

秦岭-淮河地区降水空间聚类分析

秦岭-淮河地区受复杂地形与多变季风气候影响,降水在年际和年内波动较大,空间分布呈明显区域性。通过分析不同时间尺度降水量,年降水量丰平枯状态和相邻年份年降水量变化的增平减趋势,对秦岭-淮河地区进行降水空间聚类。结果表明:根据候降水量指标可将秦岭-淮河地区分为江淮、黄淮、秦岭以南、秦岭以北4个区,据年降水量丰平枯状态联系数指标可将该地区分为江淮、黄淮、秦岭-淮河交界附近、秦岭以北高原和秦岭以南西段4个区,据相邻年份年降水量变化增平减趋势联系数指标可将该地区分为江淮、黄淮、秦岭3个区;融合3个降水指标的区域划分结果,可将秦岭-淮河地区划分为6个区:江淮、黄淮、秦岭以南、秦岭以北西段和高原区、关中区、秦岭-淮河交界过渡区。基于线性矩法的分区一致性检验表明分区内无奇异站点。

S2S模式对四川汛期候尺度降水预测技巧评估和误差订正

针对四川汛期候降水距平百分率(PAP),采用距平相关系数(ACC)、时间相关系数(TCC)、符号一致率(SCR)和趋势异常综合评分(PS)4种预测评分方法对S2S计划中10个模式的预测技巧进行检验评估,并在误差分析的基础上提出“正负概率异常订正”方案对各模式候降水距平百分率预测结果进行订正。结果表明,随着预测时效延长,多数模式的预测技巧快速降低,模式间预测技巧的差距缩小。至第10天左右,各模式进入低技巧时段,预测技巧随时效变化的幅度减小,各模式仅对降水趋势异常有一定预测能力,其中BoM模式明显高于其他模式。除BoM模式外的其他模式对降水年际变化幅度都存在低估,降水距平百分率异常偏差为-33%—-18%,不随预测时效发生太大变化,但空间分布不均。经过误差订正各模式的距平相关系数和符号一致率有所提高,趋势异常综合评分有效提高,并且对次季节尺度的订正效果优于天气尺度。订正后,各模式在次季节尺度的平均趋势异常综合评分均高于76.8, 66.7%的模式评分为79.2—80.2,超过业务评分标准(72.0)近8分。订正效果在4 a独立样本检验中也得到验证。

短中期降水温度天气过程区域分布的研究

运用旋转主分量方法对分布于全国621个站点的候降水量和2214个站的逐日最高最低气温进行分析,得到4个季节的降水气温主特征模态及其相对应的时间变率。分析结果表明,该方法所分解得到的特征模态较好地反映了全国不同区域降水温度演变的差别,依据各模态的相关系数将全国划分为不同的降水温度天气区。最后,获得表征全国不同天气特点的252个代表站,这些站的资料可作为提高要素客观预报、扩展服务领域的基本资料。

Isolated deep convections over the Tibetan Plateau in the rainy season during 2001–2020

The Tibetan Plateau(TP)is a prevalent region for convection systems due to its unique thermodynamic forcing.This study investigated isolated deep convections(IDCs),which have a smaller spatial and temporal size than mesoscale convective systems(MCSs),over the TP in the rainy season(June-September)during 2001–2020.The authors used satellite precipitation and brightness temperature observations from the Global Precipitation Measurement mission.Results show that IDCs mainly concentrate over the southern TP.The IDC number per rainy season decreases from around 140 over the southern TP to around 10 over the northern TP,with an average 54.2.The initiation time of IDCs exhibits an obvious diurnal cycle,with the peak at 1400–1500 LST and the valley at 0900–1000 LST.Most IDCs last less than five hours and more than half appear for only one hour.IDCs generally have a cold cloud area of 7422.9 km^(2),containing a precipitation area of approximately 65%.The larger the IDC,the larger the fraction of intense precipitation it contains.IDCs contribute approximately 20%–30%to total precipitation and approximately 30%–40%to extreme precipitation over the TP,with a larger percentage in July and August than in June and September.In terms of spatial distribution,IDCs contribute more to both total precipitation and extreme precipitation over the TP compared to the surrounding plain regions.IDCs over the TP account for a larger fraction than MCSs,indicating the important role of IDCs over the region.

Future changes in precipitation and water availability over the Tibetan Plateau projected by CMIP6 models constrained by climate sensitivity

Precipitation projections over the Tibetan Plateau(TP)show diversity among existing studies,partly due to model uncertainty.How to develop a reliable projection remains inconclusive.Here,based on the IPCC AR6–assessed likely range of equilibrium climate sensitivity(ECS)and the climatological precipitation performance,the authors constrain the CMIP6(phase 6 of the Coupled Model Intercomparison Project)model projection of summer precipitation and water availability over the TP.The best estimates of precipitation changes are 0.24,0.25,and 0.45 mm d^(−1)(5.9%,6.1%,and 11.2%)under the Shared Socioeconomic Pathway(SSP)scenarios of SSP1–2.6,SSP2–4.5,and SSP5–8.5 from 2050–2099 relative to 1965–2014,respectively.The corresponding constrained projections of water availability measured by precipitation minus evaporation(P–E)are 0.10,0.09,and 0.22 mm d^(−1)(5.7%,4.9%,and 13.2%),respectively.The increase of precipitation and P–E projected by the high-ECS models,whose ECS values are higher than the upper limit of the likely range,are about 1.7 times larger than those estimated by constrained projections.Spatially,there is a larger increase in precipitation and P–E over the eastern TP,while the western part shows a relatively weak difference in precipitation and a drier trend in P–E.The wetter TP projected by the high-ECS models resulted from both an approximately 1.2–1.4 times stronger hydrological sensitivity and additional warming of 0.6℃–1.2℃ under all three scenarios during 2050–2099.This study emphasizes that selecting climate models with climate sensitivity within the likely range is crucial to reducing the uncertainty in the projection of TP precipitation and water availability changes.

Climate state of the Three Gorges Region in the Yangtze River basin in 2022–2023

Based on daily observation data of the Three Gorges Region(TGR)of the Yangtze River basin and global reanalysis data,the climate characteristics,climate events,and meteorological disasters of the TGR in 2022 and 2023 were analyzed.For the TGR,the average annual temperature for 2022 and 2023 was 0.8℃ and 0.4℃ higher than normal,respectively,making them the two warmest years in the past decade.In 2022,the TGR experienced its warmest summer on record.The average air temperature was 2.4℃ higher than the average,and there were 24.8 days of above-average high temperature days during summer.Rainfall in the TGR varied significantly between 2022 and 2023.Annual rainfall was 18.4%below normal and drier than normal in most parts of the region.In contrast,the precipitation in 2023 was considerably higher than the long-term average,and above normal for almost the entire year.The average wind speed exhibited minimal variation between the two years.However,the number of foggy days and relative humidity increased in 2023 compared to 2022.In 2022–2023,the TGR mainly experienced meteorological disasters such as extreme high temperatures,regional heavy rain and flooding,overcast rain,and inverted spring chill.Analysis indicates that the abnormal western Pacific subtropical high and the abnormal persistence of the eastward-shifted South Asian high were the two important drivers of the durative enhancement of record-breaking high temperature in the summer of 2022.

哈尔滨市汛期特征与年变化

利用哈尔滨市１９５１ ～１９９８ 年候降水量资料，用候降水量突变划分汛期，并对哈尔滨市汛期特征进行分析。哈尔滨市汛期可划分为：提前型、落后型；偏长型，偏短型；连续型、分段型。平均入汛期为６ 月２１ ～２６ 日，最早入汛期为５ 月２１ ～２５ 日，最晚入汛期为７ 月２１ ～２６ 日；平均出汛期为８ 月２６～３１ 日，最早出汛期为７ 月６ ～１０ 日，最晚出汛期为１０ 月１１ ～１５ 日。平均汛期长度为６０ｄ ，最长汛期为１００ｄ ，最短汛期为２０ｄ 。

Climatic Factors for Limiting Northward Distribution of Eight Temperate Tree Species in Eastern North America

Eight temperate deciduous tree species, Acer rubrum L., A. saccharinum L., A. saccharum Marsh., Belluta alleghaniensis Britton., Fraxinus nigra Marsh., Quercus rubra L., Titia americana L., and Ulmus americana L. in eastern North America, were selected to explore relationship between the northward distribution of temperate tree species and climatic factors. For each species, more than 30 sites at their north limits of distribution were obtained from their distribution maps, and 11 climatic indices at the north limits were computed. The standardized standard deviation (SD) method, which compares the magnitude of variance of climatic indices, was used to detect which climatic parameter was the most important for explaining northward distribution of these species. We presume that the climatic parameter that has the smallest variance at the north limit would be assigned as the dominant climatic factor for limiting the distribution of this species. The results derived from the standardized SD method indicated that the SD value of warmth index (WI) and/or annual biotemperature (ABT) were the smallest among the 11 climatic indices. Since both WI and ABT represent growing season temperature, it suggested that growing season temperature was the most important climatic factor for explaining the northward distribution of these temperate tree species. The relationships between several climatic indices, WI, coldness index (CI), annual precipitation (AP), annual range of temperature (ART) and humid/arid index were also analyzed. As a result, at the north limits of all these species, both WI and CI decreased with an increase of AP, and CI increased with an increase of ART. Besides growing season temperature, precipitation and climatic continentality also have influence on the northward distribution of the temperate trees in eastern North America.

Temporal-Spatial Variances of Holocene Precipitation at the Marginal Area of the East Asian Monsoon Influences from Pollen Evidence

The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.

Precipitation as a control of vegetation phenology for temperate steppes in China

Using the NDVI ratio method, the authors extracted phenological parameters from NOAA-AVHRR NDVI time-series data （1982-2008）. The start of the growing season （SOS） and the date of maximum NDVI （Peak-t） correlated significantly with the mean annual precipitation along regional gradients of the steppes. Along the south transect （located at a lower latitude with a higher annual mean temperature） there was a positive correlation between the end of the growing season （EOS） and the mean annual precipitation along precipitation gradients （R2 = 0.709, p 〈 0.0001）. However, along the north transect （located at higher latitude with lower annual mean temperature）, the EOS was slightly negatively related with the mean annual precipitation （R2 = 0.179, p 〈 0.1）. There was positive correlation between the length of the growing season and the annual precipitation along two transects （R2 = 0.876, p 〈 0.0001 for the south transect; R2 = 0.290, p 〈 0.01 for the north transect）. Thus, for the Inner Mongolian steppe, it is precipitation rather than temperature that determines the date of the SOS.

Climate Change over China in the 21st Century as Simulated by BCC_CSM1.1-RegCM4.0

Driven by the global model,Beijing Climate Center Climate System Model version 1.1(BCC_CSM1.1),climate change over China in the 21st century is simulated by a regional climate model(RegCM4.0)under the new emission scenarios of the Representative Concentration Pathways—RCP4.5 and RCP8.5.This is based on a period of transient simulations from 1950 to2099,with a grid spacing of 50 km.The present paper focuses on the annual mean temperature and precipitation in China over this period,with emphasis on their future changes.Validation of model performance reveals marked improvement of the RegCM4.0 model in reproducing present day temperature and precipitation relative to the driving BCC_CSM1.1 model.Significant warming is simulated by both BCC_CSM1.1 and RegCM4.0,however,spatial distribution and magnitude differ between the simulations.The high emission scenario RCP8.5 results in greater warming compared to RCP4.5.The two models project different precipitation changes,characterized by a general increase in the BCC_CSM1.1,and broader areas with decrease in the RegCM4.0 simulations.

INTERANNUAL AND INTERDECADAL VARIATIONS OF LARGE-SCALE MOISTURE SINKS OVER GUANGDONG

The interannual and interdecadal variations of moisture sinks over Guangdong are discussed with the NCEP/NCAR reanalysis data and observed precipitation data from 1958 to 2004. The results indicate that climatically, the amount of precipitation is larger than that of evaporation in spring and summer. Precipitation and evaporation almost balance each other in autumn and the amount of evaporation is larger than that of precipitation in winter. The interannual signal dominates the variations of moisture sinks in all seasons in Guangdong with a period of three-year oscillation in autumn and winter. Remarkable interdecadal signal characterized by a period of three-decade oscillation can be identified for winter and spring from seasonally averaged moisture sink data and from annually moisture data, with variance percentage larger than 40%. This result indicates that Guangdong is at a transitional stage from positive anomalies to negative anomalies. The moisture sink anomalies in winter and following spring over Guangdong are usually in-phase. Besides, there exist periodic oscillations with periods of 10 to 15 years in summer and autumn. The positive (negative) anomalies of moisture sinks over Guangdong are due to the intensified (weakened) moisture from the tropical areas being transported to the Southern China, accompanied by an intensified (weakened) moisture convergence.

Revolts Frequency during 1644-1911 in North China Plain and Its Relationship with Climate

Based on the records of social revolts in the Actual Annals of Qing Dynasty （a collection of official records）, the revolts frequency （amount of counties where revolts happened every year） in North China Plain during the Qing Dynasty （1544 1911） is reconstructed. By comparing revolts frequency with temperature and precipitation series, the interaction between climate and social responses is analyzed. It can be concluded that revolts broke out more frequently in colder periods and less frequently in warmer periods, There were much more revolts in drought decades than in wet decades, and the three fatal peasant uprisings in the Qing Dynasty were all ignited by severe droughts. The impacts of changes in temperature and precipitation on revolts should be estimated at different time scales. The correspondence emerged at neither decadal nor yearly scale until the turn between 18th and 19th centuries, the critical period when per capita cropland area decreased to a vulnerable level. Food crisis increased the vulnerability of local society, and changes in temperature and precipitation became an important trigger for revolts.

When and how will the Millennium Silk Road witness 1.5 °C and 2 °C warmer worlds?

Western China and central Asia are positioned centrally along the Millennium Silk Road,which is regarded as a core region bridging the East and the West.Understanding the potential changes in climate over this core region is important to the successful implementation of the so-called＇Belt and Road Initiative＇（a $1 trillion regional investment in infrastructure）.In this study,both mean and extreme climate changes are projected using the ensemble mean of CMIP5 models.The results show a warming of ～1.5,2.9,3.6,and 6.0 ℃ under RCP2.6,4.5,6.0,and 8.5,respectively,by the end of the twenty-first century,with respect to the 1986-2005 baseline period.Meanwhile,the annual mean precipitation amount increases consistently across all RCPs,with an increase by ～14% with respect to 1986-2005 under RCP8.5.The warming over the Millennium Silk Road region reaches 1.5 ℃ before 2020 under all the emission scenarios.The 2020s （2030s） see a 2 ℃ warming under the RCP8.5 （RCP4.5） scenario.Global warming that is 0.5 ℃ lower （i.e.a warming of 1.5 ℃） could result in the avoidance of otherwise significant impacts in the Silk Road core region-specifically,a further warming of 0.73 ℃ （with an interquartile range of 0.49%-0.94 ℃） and an increase in the number of extreme heat days by 4.2,at a cost of a reduced increase of 2.72% （0.47%-3.82%） in annual precipitation.The change in consecutive dry days is region-dependent

Change in Extreme Climate Events over China Based on CMIP5

The changes in a selection of extreme climate indices(maximum of daily maximum temperature(TXx),minimum of daily minimum temperature(TNn),annual total precipitation when the daily precipitation exceeds the 95th percentile of wet-day precipitation(very wet days,R95p),and the maximum number of consecutive days with less than 1 mm of precipitation(consecutive dry days,CDD))were projected using multi-model results from phase 5 of the Coupled Model Intercomparison Project in the early,middle,and latter parts of the 21st century under different Representative Concentration Pathway(RCP)emissions scenarios.The results suggest that TXx and TNn will increase in the future and,moreover,the increases of TNn under all RCPs are larger than those of TXx.R95p is projected to increase and CDD to decrease significantly.The changes in TXx,TNn,R95p,and CDD in eight sub-regions of China are different in the three periods of the 21st century,and the ranges of change for the four indices under the higher emissions scenario are projected to be larger than those under the lower emissions scenario.The multi-model simulations show remarkable consistency in their projection of the extreme temperature indices,but poor consistency with respect to the extreme precipitation indices.More substantial inconsistency is found in those regions where high and low temperatures are likely to happen for TXx and TNn,respectively.For extreme precipitation events(R95p),greater uncertainty appears in most of the southern regions,while for drought events(CDD)it appears in the basins of Xinjiang.The uncertainty in the future changes of the extreme climate indices increases with the increasing severity of the emissions scenario.

Impacts of Climatic Factors on Runoff Coefficients in Source Regions of the Huanghe River

Runoff coefficients of the source regions of the Huanghe River in 1956-2000 were analyzed in this paper. In the 1990s runoff of Tangnaihai Hydrologic Station of the Huanghe River experienced a serious decrease, which had attracted considerable attention. Climate changes have important impact on the water resources availability. From the view of water cycling, runoff coefficients are important indexes of water resources in a particular catchment. Kalinin baseflow separation technique was improved based on the characteristics of precipitation and streamflow. After the separation of runoff coefficient （R/P）, baseflow coefficient （Br/P） and direct runoff coefficient （Dr/P） were estimated. Statistic analyses were applied to assessing the impact of precipitation and temperature on runoff coefficients （including Dr/P, Br/P and R/P）. The results show that in the source regions of the Huanghe River, mean annual baseflow coefficient was higher than mean annual direct runoff coefficient. Annual runoff coefficients were in direct proportion to annual precipitation and in inverse proportion to annual mean temperature. The decrease of runoff coefficients in the 1990s was closely related to the decrease in precipitation and increase in temperature in the same period. Over different sub-basins of the source regions of the Huanghe River, runoff coefficients responded differently to precipitation and temperature. In the area above Jimai Hydrologic Station where annual mean temperature is -3.9℃, temperature is the main factor influencing the runoff coefficients. Runoff coefficients were in inverse relation to temperature, and precipitation had nearly no impact on runoff coefficients. In subbasin between Jimai and Maqu Hydrologic Station Dr/P was mainly affected by precipitation while R/P and Br/P were both significantly influenced by precipitation and temperature. In the area between Maqu and Tangnaihai hydrologic stations all the three runoff coefficients increased with the rising of annual precipitation, while direct runoff coefficient was inversely proportional to temperature. In the source regions of the Huanghe River with the increase of average annual temperature, the impacts of temperature on runoff coefficients become insignificant.