1961~2020年中国区域不同等级降水的变化趋势及其可能成因

已有的研究表明,增暖背景下全球降水的格局发生了变化,弱降水总体呈减小趋势,而强降水在一些区域呈明显的增加趋势。但在区域尺度上不同等级强度降水的变化还缺乏系统的研究。本文基于中国838个气象站点的降水资料,研究了1961~2020年来中国弱降水、中等强度降水和极端降水长期变化趋势及其年代际分量与年代际海温振荡型的关联性。结果表明:中国不同等级降水变化的空间分布差异较大。弱降水仅在西北西部和青藏高原地区以增加为主,在华南和西南地区以显著减少为主;中等强度降水在西南地区东部以显著减少为主,在其余地区以增长为主;强降水在大部分地区呈现增长趋势,仅在京津冀和重庆部分地区呈现减少趋势。中国大部分地区的弱降水量(日数)对总降水的贡献率以减少为主,中等强度降水日数、强降水量(日数)的贡献率以显著增长为主,各区域强降水贡献率与中等强度降水和弱降水贡献率呈相反的年代际变化。其中,弱降水日数和中等强度降水日数的变化主导了总降水日数的变化,中等强度降水量和强降水量的变化主导了总降水量的变化。进一步研究发现,在年代际尺度上,中国大部分地区的不同等级降水与太平洋年代际振荡(PDO)的相关系数随等级增大而趋于负值,与大西洋多年代际振荡(AMO)的相关系数则随等级增大而趋于正值。各区域不同等级降水与PDO/AMO相关关系的年代际突变主要发生在1980年代至1990年代。

Will the Globe Encounter the Warmest Winter after the Hottest Summer in 2023?

In the boreal summer and autumn of 2023,the globe experienced an extremely hot period across both oceans and continents.The consecutive record-breaking mean surface temperature has caused many to speculate upon how the global temperature will evolve in the coming 2023/24 boreal winter.In this report,as shown in the multi-model ensemble mean(MME)prediction released by the Institute of Atmospheric Physics at the Chinese Academy of Sciences,a medium-to-strong eastern Pacific El Niño event will reach its mature phase in the following 2−3 months,which tends to excite an anomalous anticyclone over the western North Pacific and the Pacific-North American teleconnection,thus serving to modulate the winter climate in East Asia and North America.Despite some uncertainty due to unpredictable internal atmospheric variability,the global mean surface temperature(GMST)in the 2023/24 winter will likely be the warmest in recorded history as a consequence of both the El Niño event and the long-term global warming trend.Specifically,the middle and low latitudes of Eurasia are expected to experience an anomalously warm winter,and the surface air temperature anomaly in China will likely exceed 2.4 standard deviations above climatology and subsequently be recorded as the warmest winter since 1991.Moreover,the necessary early warnings are still reliable in the timely updated mediumterm numerical weather forecasts and sub-seasonal-to-seasonal prediction.

Can Eurasia Experience a Cold Winter under a Third-Year La Nina in 2022/23?

The Northern Hemisphere(NH)often experiences frequent cold air outbreaks and heavy snowfalls during La Nina winters.In 2022,a third-year La Nina event has exceeded both the oceanic and atmospheric thresholds since spring and is predicted to reach its mature phase in December 2022.Under such a significant global climate signal,whether the Eurasian Continent will experience a tough cold winter should not be assumed,despite the direct influence of mid-to high-latitude,large-scale atmospheric circulations upon frequent Eurasian cold extremes,whose teleconnection physically operates by favoring Arctic air invasions into Eurasia as a consequence of the reduction of the meridional background temperature gradient in the NH.In the 2022/23 winter,as indicated by the seasonal predictions from various climate models and statistical approaches developed at the Institute of Atmospheric Physics,abnormal warming will very likely cover most parts of Europe under the control of the North Atlantic Oscillation and the anomalous anticyclone near the Ural Mountains,despite the cooling effects of La Nina.At the same time,the possibility of frequent cold conditions in mid-latitude Asia is also recognized for this upcoming winter,in accordance with the tendency for cold air invasions to be triggered by the synergistic effect of a warm Arctic and a cold tropical Pacific on the hemispheric scale.However,how the future climate will evolve in the 2022/23 winter is still subject to some uncertainty,mostly in terms of unpredictable internal atmospheric variability.Consequently,the status of the mid-to high-latitude atmospheric circulation should be timely updated by medium-term numerical weather forecasts and sub-seasonal-to-seasonal prediction for the necessary date information and early warnings.

关于我国北方干旱化及其转折性变化

过去半个世纪,中国经历了北方的"西湿东干"和东部的"南涝北旱"的降水分布格局。近十几年来,这种降水长期变化的分布格局是维持还是发生了变化?针对这个问题,本文基于年降水观测数据、自矫正的帕尔默干旱指数sc PDSI、地表湿润指数SWI及GRACE(Gravity Recovery and Climate Experiment)卫星数据反演的陆地水储量(TWS)对中国区域干旱化问题进行了再分析。结果表明,近16年(2001~2016年),中国东部地区(100°E以东)"南涝北旱"的格局正在发生显著的变化,长江上中游及江淮流域已转为显著的干旱化趋势,而华北地区的降水已转为增加趋势,东部"南旱北涝"的格局基本形成;北方过去的"西湿东干"也转变为"西干东湿"的空间分布特征。显然,中国区域的降水格局在2001年后发生了明显的年代尺度转折性变化,两种常用干旱指数sc PDSI和SWI的分析也证明了这一点。但GRACE的陆地水储量(TWS)的分析却显示,最近16年来,中国东部"南涝北旱"的格局仍未发生变化,北方大部分地区仍然处于干旱化的时段,且有加剧的趋势,其原因有待于进一步研究。

地面气候资料均一性研究进展

气象台站观测的地面气候资料是气候变化研究的重要基础,气候资料的均一性检验和订正对于提高气候资料的质量和均一性状况具有实用意义和价值。通过回顾近年来国内外地面气候资料均一性研究进展、研究技术及发展趋势,总结了目前国内广泛应用的两种较为成熟的均一化方法(RHtest和MASH)及其对气温、风速资料均一性研究取得的一些成果,分析我国地面气候资料均一性研究的发展历程及现状,指出我国地面气候资料均一性研究存在的问题,未来需要在加强对台站元数据信息收集整理基础上,深入开展气候资料均一化技术和方法的基础研究,评估不同方法的优缺点,重建近百年中国地区均一化的气候序列。

Modeling of surface flux in Tongyu using the Simple Biosphere Model 2 (SiB2)

The modeling ability of a stand-alone version of the Simple Biosphere Model 2（SiB2） was tested mainly through diagnosing the simulated latent heat（LE）,sensible heat（H）,CO2 flux,and air temperature at the Tongyu field observation station（44°25＇N,122°52＇E,184 m elevation） of Coordinated Enhanced Observing Period（CEOP）,where the land cover is cropland and grassland.In the whole year of 2003,the canopy height and the leaf area index was variable.During non-growth period,the surface would become bare,while during the growth period,the canopy height could reach 2.0 m high over cropland and 0.8 m high over grassland,respectively,and max leaf area index could reach 4.2 and 2.4,respectively.The model was initialized with measurement and driven by half-hourly atmospheric observations.The simulation values for 2003 were compared against measurements.Results show that the model is of a good ability of simulating the hourly latent heat（LE）,sensible heat（H）,CO2 flux and temperature during the growth period.Moreover,the daily LE,H and CO2 flux simulated by SiB2 could reflect their yearly change reasonably.However,the model may overestimate the H generally.

CoLM模式在中国温带混交林和亚热带人工针叶林的水热通量模拟性能评估

利用中国陆地生态系统通量观测研究网络(ChinaFLUX)在长白山温带混交林观测站点和千烟洲亚热带人工针叶林观测站点的强化观测资料,考察了一个较为完善的陆面过程模式(Common LandModel,CoLM)在这两种不同植被类型下垫面的模拟性能,特别是其对潜热通量的模拟。模拟结果与强化观测资料的对比表明,CoLM能较好地模拟出实验站点地表能量平衡的基本特征以及潜热通量的日变化和季节变化。其中长白山站和千烟洲站潜热通量日平均的观测值与模拟值的相关系数分别为0.804和0.692,均通过了0.001的显著性水平检验。总体而言,CoLM在长白山站的模拟效果更好一些,模式对不同植被覆盖类型的土壤—植被—大气间水热传输过程的处理可能是造成差别的原因。

CMIP6检测归因模式比较计划(DAMIP)概况与评述

气候变化的检测归因是历次IPCC评估报告的重要组成部分。检测归因的目标是检测并量化由外强迫引起的变化,识别人为和自然强迫对气候变化的相对贡献。有助于全面评估气候系统是如何受人类活动影响的,所得结论对未来气候变化预估的信度而言至关重要。检测归因模式比较计划(DAMIP)是第六次国际耦合模式比较计划(CMIP6)的一个子计划,共包含3个级别、多达14组不同强迫驱动下的试验。文中概述其科学背景、试验设计、参与模式情况,并评述该计划的意义、期待的产出以及中国的机遇和贡献,以期使读者迅速了解相关要点和进展,为利用这些模式模拟试验数据开展检测归因研究提供必要的参考。

亚洲中部干旱气候研究综述与机理分析

综述了亚洲中部干旱气候若干研究进展,并对亚洲中纬度干旱区形成机理进行了深入分析。依据大尺度气候分类法将全球陆地划分为季风、地中海及西风带气候区,分别对应于年内季节循环中多雨—高温的同位相、反位相及不相关等类型水—热配置特征。亚洲中部干旱区南北部分属地中海和西风带气候区,其不同水—热位相配置又对应于不同的水汽通量及其散度等特征。研究揭示了欧亚大陆中部干旱区形成于降水不足且季节性水—热配置不当,起因于大气环流平均槽脊季节变化引起的大气动力—热力配置,其根源是海陆热力差异及大地形对大气环流强迫的结果。本文还讨论了季风区与非季风区之间平均气流水汽散度的季节性互动,以及行星尺度上不同气候区之间平均气流与瞬变涡动水汽散度之间的配置等问题。

一个多参数优化系统在简单模型中的应用

针对数值模式的物理参数,发展了一个多参数优化系统,可以根据观测数据对模式的多个参数进行同时调整。该系统具有设计简单、无需伴随模式和便于移植等特点。在孪生试验中,针对盒子模型的3个参数,经过约10次迭代,多参数优化系统可以收敛到预先给定的参数真值。通过对比同时优化和分别单独优化3个参数增量,发现分别单独优化参数增量存在一定的局限性。将多参数优化系统应用到简单模型的尝试和检验,结果表明:优化算法的收敛速度和模型的积分次数处于可接受的范围内,因此具有同时调整多个复杂模式物理参数的潜力。

An Overview of the Semi-arid Climate and Environment Research Observatory over the Loess Plateau

Arid and semi-arid areas comprise about 30% of the earth＇s surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a special semi-arid land surface and part of a dust aerosol source. To improve understanding and capture the direct evidence of the impact of human activity on the semi-arid climate over the Loess Plateau, the Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL） was established in 2005. SACOL consists of a large set of instruments and focuses on： （1） monitoring of long term tendencies in semiarid climate changes; （2） monitoring of the aerosol effect on the water cycle; （3） studies of interaction between land surface and the atmosphere; （4） improving the land surface and climate models; and （5） validation of space-borne observations. This paper presents a description of SACOL objectives, measurements, and sampling strategies. Preliminary observation results are also reviewed in this paper.

An Index Measuring the Interannual Variation of the East Asian Summer Monsoon-The EAP Index

Based on the EAP (East Asia/Pacific) teleconnection in the summer circulation anomalies over the Northern Hemisphere, an index measuring the strength of the East Asian summer monsoon, i.e., the so-called EAP index, is defined in this paper. From the analyses of observed data, it is clearly shown that the EAP index defined in this study can well describe the interannual variability of summer rainfall and surface air temperature in East Asia, especially in the Yangtze River valley and the Huaihe River valley, Korea, and Japan. Moreover, this index can also reflect the interannual variability of the East Asian summer monsoon system including the monsoon horizontal circulation and the vertical-meridional circulation cell over East Asia. From the composite analyses of climate and monsoon circulation anomalies for high EAP index and for low EAP index, respectively, it is well demonstrated that the EAP index proposed in this study can well measure the strength of the East Asian summer monsoon.

Numerical Study of Impacts of Soil Moisture on the Diurnal and Seasonal Cycles of Sensible/Latent Heat Fluxes over Semi-arid Region

The semi-arid regions, as climatic and ecosystem transitional zones, are the most vulnerable to global environmental change. Earlier researches indicate that the semi-arid regions are characterized by strong landatmosphere coupling in which soil moisture is the crucial variable in land surface processes. In this paper, we investigate the sensitivity of the sensible/latent heat fluxes to soil moisture during the growing season based on the enhanced observations at Tongyu in the Jilin province of China, a reference site of international Coordinated Energy and Water Cycle Observations Project （CEOP） in the semi-arid regions, by using a sophisticated land surface model （NCAR_CLM3.0）. Comparisons between the observed and simulated sensible/latent heat fluxes indicate that the soil moisture has obvious effects on the sensible/latent heat fluxes in terms of diurnal cycle and seasonal evolution. Better representation of the soil moisture could improve the model performance to a large degree. Therefore, for the purpose of simulating the land-atmosphere interaction and predicting the climate and water resource changes in semi-arid regions, it is necessary to enhance the description of the soil moisture distribution both in the way of observation and its treatment in land surface models.

A new classification of large-scale climate regimes around the Tibetan Plateau based on seasonal circulation patterns

This study aims to develop a large-scale climate classification for investigating the characteristics of the climate regimes around the Tibetan Plateau based on seasonal precipitation, moisture transport and moisture divergence using in situ observations and ERA40 reanalysis data. The results indicate that the climate can be attributed to four regimes around the Plateau. They situate in East Asia, South Asia, Central Asia and the semi-arid zone in northern Central Asia throughout the dryland of northwestern China, in addition to the K?oppen climate classification. There are different collocations of seasonal temperature and precipitation: 1) in phase for the East and South Asia monsoon regimes, 2) anti-phase for theCentral Asia regime, 3) out-of-phase for the westerly regime. The seasonal precipitation concentrations are coupled with moisture divergence, i.e., moisture convergence coincides with the Asian monsoon zone and divergence appears over the Mediterranean-like arid climate region and westerly controlled area in the warm season, while it reverses course in the cold season. In addition, moisture divergence is associated with meridional moisture transport. The northward/southward moisture transport corresponds to moisture convergence/divergence, indicating that the wet and dry seasons are, to a great extent, dominated by meridional moisture transport in these regions. The climate mean southward transport results in the dry-cold season of the Asian monsoon zone and the dry-warm season, leading to desertification or land degradation in Central Asia and the westerly regime zone. The mean-wind moisture transport (MMT) is the major contributor to total moisture transport, while persistent northward transient eddy moisture transport (TEMT) plays a key role in dry season precipitation, especially in the Asian monsoon zone. The persistent TEMT divergence is an additional mechanism of the out-of-phase collocation in the westerly regime zone. In addition, the climatemean MMTand TEMTare associated with the atmospheric stationary wave and storm track, which results from the uplift of orography and landsea thermal contrast. Therefore, the paleoclimate changes in mid-latitude arid-semi-arid regions are linked to the different phases of uplift of mountains and plate motion tied to the evolution of the Mediterranean.

Warm–dry collocation of recent drought in southwestern China tied to moisture transport and climate warming

This study aims to investigate the recent drought in southwestern China and its association with environmental changes in moisture transport （MT） and atmospheric circulation. Climatic Research Unit grid data, in situ observations in China, and ERA-interim reanalysis are used to study the characteristics of the drought and the associated mechanism. Recent precipitation trends show a pattern of ＂Northern wetting and Southern drying＂, similar to the anti-phase of the climate pattern prevailing during 1980--2000 in China's Mainland; southwestern China incurred a severe drought during 2009-20l 3. Wavelet analysis reveals that the drought coincides with a warm-dry phase of temperature and precipitation on a period of about 20 years and beyond 100 years, where contributions account for 43% and 57% of the deficiency of the precipitation, averaged for 2003-2012, respectively. A further investigation reveals that the drought results chiefly from the decline of the southwestern monsoon MT toward southwestern China, in addition to mid-latitude circulation changes, which leads to more blockings near the Ural Mountains and the Sea of Okhotsk in the rainy season and negative anomalies around Lake Baikal and northeast China in the dry season. These anomalies are likely to be correlated with global sea surface temperature changes and need to be studied further.

The Role of Land-sea Distribution and Orography in the Asian Monsoon. Part II： Orography

The role of various mountains in the Asian monsoon system is investigated by AGCM simulations with different mountains. The comparison of the simulation with Asian mountains （MAsia run） with the simulation without mountains （NM run） reveals that the presence of the Asian mountains results in a stronger South Asian summer monsoon （SASM）, characterized by enhanced lower-tropospheric westerly winds, uppertropospheric easterly winds, and stronger water vapor convergence. In East Asia, the southerly winds and water vapor convergence are significantly strengthened in association with the intensified zonal pressure gradient between the East Asian continent and the Pacific Ocean. Both the dynamical and thermodynamic forcing of the Tibetan Plateau play important role in strengthening the Asian summer monsoon. In winter, the presence of Asian mountains significantly strengthens the continental high, which leads to a stronger Asian winter monsoon. The presence of African-Arabian mountains helps to intensify the exchange of mass between the Southern Hemisphere and Northern Hemisphere by strengthening the cross equatorial flows in the lower and upper troposphere over East Africa. Asian mountains also play a crucial role in the seasonal evolution of Asian monsoons. In comparison with the NM run, the earlier onset and later withdrawal of lower-tropospheric westerly winds can be found over South Asia in the MAsia run, indicating a longer SASM period. The African-Arabian mountains also moderately contribute to the seasonal variation of the South Asian monsoon. In East Asia, the clear southto-north march of the southerly winds and subtropical rainfall starts to occur in early summer when the effects of Asian mountains are considered.

Simulation and Evaluation of Terrestrial Ecosystem NPP with M-SDGVM over Continental China

Using the regional terrestrial Net Primary Production （NPP） from different observations and models over China, we validated the NPP simulations and explored the relationship between NPP and climate variation at interannual and decadal scales in the Modified Sheffield Dynamic Global Vegetation Model （M-SDGVM） during 1981–2000. M-SDGVM shows agreement with the NPP data from 743 sites under the Global Primary Production Data Initiative （GPPDI）. The spatial and the zonal averaged NPP of M-SDGVM agree well with different historic datasets and are closest to the IGBP NPP. Compared to the 1980s, NPP in the 1990s increases in most of China with a high degree of spatial heterogeneity. The multi-year mean NPP of forest types is reasonably modeled （above 500 g C m-2 yr-1 ） while that of C 3 path of photosynthesis （C 3 ） grasslands is underestimated. The NPP of 7 M-SDGVM main plant functional types （PFTs） increases and the increment of the broad-leaved deciduous forest is the most obvious （5.05 g C m-2 yr-1 ）. During the studied period, the annual NPP of M-SDGVM over China increases, with significant fluctuations, at an average rate of 0.0164 Gt C yr-1 . Regulated by annual temperature and precipitation, the interannual variation of the total NPP shows more significant correlation with temperature （relativity and probability are R= 0.61, P = 0.00403） than precipitation （R = 0.40, P = 0.08352）. CO 2 fertilization may play a key role in the increase of terrestrial ecosystem NPP over continental China, and CO 2 stimulation increases with CO 2 concentrations, and also with the climate variability of the 1980s and 1990s.

Direct Climatic Effect of Aerosols and Interdecadal Variations over East Asia Investigated by a Regional Coupled Climate-Chemistry/Aerosol Model

The direct climatic effect of aerosols for the 1980-2000 period over East Asia was numerically investigated by a regional scale coupled climate-chemistry/ aerosol model, which includes major anthropogenic aerosols （sulfate, black carbon, and organic carbon） and natural aerosols （soil dust and sea salt）. Anthropogenic emissions used in model simulation are from a global emission inventory prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report （IPCC AR5）, whereas natural aerosols are calculated online in the model. The simulated 20-year average direct solar radiative effect due to aerosols at the surface was estimated to be in a range of-9- -33 W m-2 over most areas of China, with maxima over the Gobi desert of West China, and-12 W m-2 to -24 W m-2 over the Sichuan Basin, the middle and lower reaches of the Yellow River and the Yangtze River. Aerosols caused surface cooling in most areas of East Asia, with maxima of-0.8℃ to -1.6℃ over the deserts of West China, the Sichuan Basin, portions of central China, and the middle reaches of the Yangtze River. Aerosols induced a precipitation decrease over almost the entire East China, with maxima of-90 mm/year to -150 mm/year over the Sichuan Basin, the middle reaches of the Yangtze River and the lower reaches of the Yellow River. Interdecadal variation of the climate response to the aerosol direct radiative effect is evident, indicating larger decrease in surface air temperature and stronger per- turbation to precipitation in the 1990s than that in the 1980s, which could be due to the interdecadal variation of anthropogenic emissions.

Spatial and Quantitative Comparison of Satellite-Derived Land Cover Products over China

Because land cover plays an important role in global climate change studies, assessing the agreement among different land cover products is critical. Significant discrepancies have been reported among satellite-derived land cover products, especially at the regional scale. Dif- ferent classification schemes are a key obstacle to the comparison of products and are considered the main fac- tor behind the disagreement among the different products. Using a feature-based overlap metric, we investigated the degree of spatial agreement and quantified the overall and class-specific agreement among the Moderate Resolution Imaging Spectoradiometer （MODIS）, Global Land Cover 2000 （GLC2000）, and the National Land Cover/Use Data- sets （NLCD） products, and the author assessed the prod- ucts by ground reference data at the regional scale over China. The areas with a low degree of agreement mostly occurred in heterogeneous terrain and transition zones, while the areas with a high degree of agreement occurred in major plains and areas with homogeneous vegetation. The overall agreement of the MODIS and GLC2000 products was 50.8% and 52.9%, and the overall accuracy was 50.3% and 41.9%, respectively. Class-specific agree- ment or accuracy varied significantly. The high-agreement classes are water, grassland, cropland, snow and ice, and bare areas, whereas classes with low agreement are shru- bland and wetland in both MODIS and GLC2000. These characteristics of spatial patterns and quantitative agree- ment could be partly explained by the complex landscapes, mixed vegetation, low separability of spectro-temporal- texture signals, and coarse pixels. The differences of class definition among different the classification schemes also affects the agreement. Each product had its advantages and limitations, but neither the overall accuracy nor the class-specific accuracy could meet the requirements of climate modeling.

Progress in Research on Homogenization of Climate Data

The observation data from ground surface meteorological stations is an important basis on which climate change research is carried out, while the homogenization of the data is necessary for improving the quality and homogeneity of the time series. This paper reviews recent advances in the techniques of identifying and adjusting inhomogeneity in climate series. We briefly introduce the results of applying two commonly accepted and well-developed methods (RHtest and MASH) to surface climate observations such as temperature and wind speed in China. We then summarize current progress and problems in this field, and propose ideas for future studies in China. Along with collecting more detailed metadata, more research on homogenization technology should be done in the future. On the basis of comparing and evaluating advantages and disadvantages of different homogenization methods, the homogenized climate data series of the last hundred years should be rebuilt.