砂颗粒矿物成分对MICP过程的影响及机理

微生物诱导碳酸钙沉淀(MICP)是一种绿色环保的新型土体加固技术,具有广泛的应用前景。为了研究砂颗粒矿物成分对MICP过程的影响,分别选用石英砂和钙质砂为代表性研究对象,利用环氧树脂胶结固化后打磨制成样片,再在配置好的菌液和胶结液中对样片表面进行MICP处理,结合X射线衍射(XRD)、扫描电镜(SEM)以及超声震荡试验定量分析了碳酸钙产量、矿物晶型、晶貌及界面胶结特性。结果表明:(1)钙质砂颗粒比石英砂颗粒更利于微生物诱导生成碳酸钙,平均单位面积碳酸钙生成量前者约为后者的5倍;(2)两种砂颗粒表面生成的碳酸钙主要为球霰石和方解石,钙质砂界面能更低,诱导生成更多的方解石;(3)石英砂表面生成的碳酸钙主要为较大的球形颗粒,而钙质砂表面的碳酸钙形貌主要为板片状;(4)微生物在钙质砂颗粒上诱导生成的碳酸钙呈现更高的界面胶结强度,经超声波震荡后,石英砂颗粒上碳酸钙的质量损失率约为钙质砂的10倍。在此基础上,运用微生物学、晶体化学、结晶矿物学等其他相关学科的理论,系统分析了石英砂和钙质砂对MICP过程及效果的影响机理,取得了新的认识,对优化MICP技术在岩土工程中的应用有重要意义。

MICP增强改性煤矸石在水稳材料中应用的试验研究

为解决煤矸石集料强度低、吸水率高、易崩解等问题,采用微生物诱导碳酸盐沉积(MICP)技术对煤矸石进行了增强改性。通过表观密度、吸水率、压碎值和超声波质量损失率的测试,同时结合SEM,EDS和XRD微观表征,研究了微生物矿化时间、菌液浓度和煤矸石粒径对MICP增强改性煤矸石性能的影响,并揭示了MICP增改性煤矸石的机理。将MICP增强改性煤矸石应用于水稳材料,通过无侧限抗压强度、间接抗拉强度和抗压回弹模量的测试,对比了MICP增强改性煤矸石水稳材料与普通煤矸石水稳材料的性能。结果表明:采用MICP增强改性技术可以提升煤矸石的物理力学性能,并且煤矸石的粒径越大增强改性效果越明显;在菌液OD600值(溶液在600 nm波长处的吸光值)为0.8、矿化改性7 d的条件下,MICP增强改性煤矸石比普通煤矸石的表观密度增加了14.66%,吸水率降低了40.94%,压碎值降低了7.93%;经MICP增强改性后的煤矸石表面包裹的生物CaCO_(3)方解石使得煤矸石的表观密度增加,吸水率和压碎值降低,强度提高,从而提升了煤矸石的性能;水泥稳定MICP增强改性煤矸石混合料最佳含水量比普通煤矸石水稳材料降低了17.3%,最大干密度增加了7.9%;MICP增强改性煤矸石水稳材料各龄期的无侧限抗压强度、间接抗拉强度和抗压回弹模量比普通煤矸石水稳材料均显著提升,表现出更高的强度、更好的抗裂性能和抗变形能力。

外掺剂联合MICP固化风积沙试验研究

微生物诱导碳酸钙沉淀技术(MICP)结合纤维加筋或外加剂已成为岩土体改良的新型方式,在土地荒漠化治理等场景具有广阔的应用前景。以取自毛乌素沙漠的风积沙为研究对象,在MICP联合纤维加筋的基础上,分别引入料姜石和氧化钙,使得两种无机化合物对微生物过程及加固效果产生影响,在最优养护条件下进行风积沙的固化试验,通过无侧限抗压强度试验、三轴试验、扫描电镜试验等,从宏观、微观角度系统分析外掺剂参与固化后试样的力学特性、破坏形态及作用机理。结果表明,MICP纤维加筋试样的强度随料姜石掺量的增加呈现增大趋势,并在掺量为4%时达到峰值,较未掺入料姜石试样的强度提高了37.3%;MICP纤维加筋试样的强度随氧化钙掺量的增加呈现先减小后增大的趋势,并在掺量达到1%时强度下降了74.6%;氧化钙对细菌具有明显的抑制作用,当氧化钙掺量达到0.8%时,大部分细菌已失去活性,OD_(600)值降至最低,为0.107;料姜石对MICP纤维加筋固化效果的作用机理主要表现在料姜石可有效地黏结砂土颗粒和填充孔隙,从而提高试样的整体稳定性。研究成果可为风积沙固化实践和实际工程应用提供参考依据。

基于MICP法的巴氏生孢八叠球菌固化镉污染土的试验研究

以重金属污染土的治理为背景,通过毒性浸出、无侧限抗压强度、土柱淋滤试验并结合镉形态分析等其他微观测试方法,探讨了Ca^(2+)的添加、Cd^(2+)浓度、养护时间等因素对驯化巴氏生孢八叠球菌固化镉污染土特性的影响.结果表明:Ca^(2+)对固化土中Cd^(2+)浸出特性影响显著,不添加Ca^(2+)时,当尿素浓度为0.5 mol·L^(-1),固化土的Cd^(2+)浸出质量浓度(0.42~5.64 mg·L^(-1))最低;添加Ca^(2+)后,Cd^(2+)浸出浓度略有增大,胶结液中尿素和Ca^(2+)浓度均为0.5 mol·L^(-1)时,Cd^(2+)的固化效果较好.延长养护时间,固化后土体的抗压强度增加,Cd^(2+)浸出浓度降低且固化效果提高;增大Cd^(2+)浓度,固化后土体的抗压强度降低,Cd^(2+)浸出浓度提高;添加Ca^(2+)有助于增强镉污染土的固化效果,在养护时间为28 d时,当Cd^(2+)浓度为100 mg·kg^(-1)时,添加Ca^(2+)的试样强度达到312 kPa,相较于未添加Ca^(2+)试样强度(234 kPa)提升了33.3%;当Cd^(2+)浓度增大至1600 mg·kg^(-1)时,添加Ca^(2+)的试样强度达到269 kPa,相较于未添加Ca^(2+)试样强度提升了57.3%,试样的浸出浓度降低了15.4%;经淋滤后,添加Ca^(2+)的试样滤出液中Cd^(2+)浓度始终低于未添加Ca^(2+)试样.固化后土中弱酸可提取态镉向可还原态镉和残渣态镉转变,添加Ca^(2+)进一步降低弱酸可提取态镉所占比例,减小了Cd^(2+)的迁移能力.

Coupled multiphysical model for investigation of influence factors in the application of microbially induced calcite precipitation

The study presents a comprehensive coupled thermo-bio-chemo-hydraulic(T-BCH)modeling framework for stabilizing soils using microbially induced calcite precipitation(MICP).The numerical model considers relevant multiphysics involved in MICP,such as bacterial ureolytic activities,biochemical reactions,multiphase and multicomponent transport,and alteration of the porosity and permeability.The model incorporates multiphysical coupling effects through well-established constitutive relations that connect parameters and variables from different physical fields.It was implemented in the open-source finite element code OpenGeoSys(OGS),and a semi-staggered solution strategy was designed to solve the couplings,allowing for flexible model settings.Therefore,the developed model can be easily adapted to simulate MICP applications in different scenarios.The numerical model was employed to analyze the effect of various factors,including temperature,injection strategies,and application scales.Besides,a TBCH modeling study was conducted on the laboratory-scale domain to analyze the effects of temperature on urease activity and precipitated calcium carbonate.To understand the scale dependency of MICP treatment,a large-scale heterogeneous domain was subjected to variable biochemical injection strategies.The simulations conducted at the field-scale guided the selection of an injection strategy to achieve the desired type and amount of precipitation.Additionally,the study emphasized the potential of numerical models as reliable tools for optimizing future developments in field-scale MICP treatment.The present study demonstrates the potential of this numerical framework for designing and optimizing the MICP applications in laboratory-,prototype-,and field-scale scenarios.

MICP加固土质排水沟边坡稳定性分析

【目的】探究应用微生物诱导CaCO3沉淀(MICP)固结土壤技术对于土质排水沟边坡稳定性的影响机制。基于土工直剪试验和数值模拟法研究不同工况下MICP加固的土坡稳定性,为MICP生物护坡措施应用于土坡加固提供理论依据。【方法】选用OD600=0.97的巴氏芽孢杆菌和1 mol/L的固结液(CO(NH_(2))_(2)∶CaCl_(2)=1∶1),固菌比为5∶3,添加15%固结液质量的脲酶抑制剂。布置4个试验土箱,设置对照组CK和固结组C1、C2、C3,对照组喷洒清水,设计入渗10 cm土层,固结组按先固结液后菌液顺序喷洒设计入渗5、10、15 cm土层。对固结后的风干土、饱和土、落干土进行直剪试验,利用直剪结果分析不同工况土坡稳定性。【结果】MICP处理的土体抗剪强度均有所提升;饱和处理后CK、C1、C2、C3的内摩擦角降幅为46.67%,39.73%,28.98%和27.85%,黏聚力降幅76.37%,62.83%,39.09%和51.62%,CK土坡处于欠稳定,C1、C2、C3土坡满足安全要求,黏聚力是影响边坡稳定的主要因素。【结论】MICP可以提高土质排水沟边坡的稳定性,其最佳固结深度是10 cm。

MICP加固花岗岩残积土的渗透特性

MICP技术可以显著降低固化土壤的渗透系数,然而目前没有关于MICP固化土壤渗透系数的理论计算方法。基于理论推导和试验验证的方法,研究MICP加固花岗岩残积土的渗透特性,提出MICP加固花岗岩残积土的碳酸钙生成量和渗透系数理论表达式。假设MICP的反应速率线性衰减,通过酶促反应动力学方程得到MICP加固土体的CaCO3生成量,估算CaCO3晶体的粒径和个数,从而获得加固后试样的孔隙比、迂曲度和颗粒比表面积,代入修正的Kozeny-Carman方程,得到加固后土体的渗透系数理论表达式。与试验数据对比分析结果表明:CaCO3的产量早期增加快,后期增加变缓并逐渐趋于稳定;MICP加固土体的渗透系数其具有早期降低快,后期趋于平稳的特征。胶结液浓度为0.50、0.75、1.00、1.25 kmol/m3的试样渗透系数最终分别降低了35%、40%、45%和55%。提出的CaCO3含量表达式和渗透系数表达式与试验结果拟合良好,可为微生物加固的设计计算提供参考。

MICP固化松散砒砂岩抗水蚀机理研究

[目的]探究MICP固化松散砒砂岩效果,为减少砒砂岩区水土流失提供解决方案与理论依据。[方法]从宏观尺度(贯入强度、降雨侵蚀等)探究菌液浓度和固化频次对MICP固化砒砂岩对力学性能及其抗水蚀性能的影响,并在微观尺度(X射线衍射、扫描电子显微镜、傅里叶红外光谱、热分析)解释了砒砂岩固化土的抗水蚀机理。[结果]相同固化次数下菌液浓度(OD_(600))为0.8时固化效果最好,其强度相较其他浓度可提升20%~50%;在最佳菌液浓度0.8时,固化频次为5次时砒砂岩即可获得很好的强度以及抗水蚀性,总雨蚀损失量可降至固化前的10%。菌液浓度0.8时碳酸钙含量生成最多,且多为菱形块状的方解石相,分布更加密集,随着固化次数的增加,胶结及填充效果更好。[结论]细菌及其胞外聚合物(EPS)在MICP中作为成核位点,参与碳酸钙的定位以及生长,并提高了碳酸钙的稳定性;EPS与碳酸钙以及砒砂岩中的矿物形成分子间氢键,增强了碳酸钙的胶结性能,且进一步提高了砒砂岩的强度以及抗水蚀性。

冻融循环作用下MICP固化铅污染土的强度与浸出特性研究

微生物诱导碳酸钙沉淀(MICP)技术可用于重金属污染土固化稳定修复。本文通过开展无侧限抗压强度、离子浸出及微观试验,主要研究MICP固化铅污染土在冻融循环作用下的强度与化学稳定性,并揭示其微观作用机理。结果表明:随着铅离子浓度的增加,土体的无侧限抗压强度先增大后减小,铅离子浸出浓度增大;随冻融循环次数的增加,土体的强度逐渐降低并趋于稳定,铅离子浸出浓度增大。冻融循环作用后,固化土的主要矿物成分未发生变化;土中的小孔隙数量增加,大孔隙数量基本保持不变。冻融循环作用损伤固化土的碳酸钙胶结与铅离子沉淀结构,致使土体性能劣化。

基于高密度电阻率成像技术的MICP浆液入渗过程监测研究

微生物诱导碳酸钙沉淀(MICP)技术是一种生态环保、前景广阔的土体改性方法,其改性效果与浆液的入渗特征密切相关。为此,提出将高密度电阻率成像(ERT)技术用于MICP浆液入渗过程监测。文章通过开展模型试验,对石英砂试样进行混合一步注浆法MICP处理,同时对试样持续进行ERT监测及电导率分析,获取了试样的三维电阻率变化特征,处理完成后测定了试样中碳酸钙含量的空间分布。结果表明:(1)MICP反应过程中,砂土与注浆液电导率随尿素分解而逐渐升高;(2)注浆液的迁移分布对砂土内部低电阻区的分布规律起主导作用,而碳酸钙沉淀的影响较小;(3)在MICP处理过程中,碳酸钙沉淀的生成与注浆液的迁移渗透相互作用,共同影响改性效果;(4)ERT技术可有效监测MICP处理区电阻率的时空演化特征,准确反映注浆液渗透迁移情况,进而评价改性效果。研究结果表明,采用ERT技术监测MICP改性土体过程具有可行性,为评价和优化微生物矿化改性效果提供了新的技术思路和方向。

MICP技术在地下水封油库渗控注浆中的应用潜力

地下水封油库在建设及运营过程中洞室涌水量大小是影响洞库水封安全和运营成本的重要因素。目前地下水封油库工程建设中采用传统的注浆方式难以将围岩渗透性降低到设计要求,因此洞室涌水量得不到很好的控制。微生物诱导碳酸钙沉淀(MICP)技术具有注浆黏度低、环境适应性强、生成矿化物质稳定等显著优点,引起了学术界与工程界广泛的兴趣和研究。本文首先分析了地下水封油库涌水量控制中存在的相关问题,然后阐述了MICP技术对裂隙渗流控制的机理、影响因素以及对裂隙渗透性的影响效果,最后探讨了MICP技术在地下水封油库中应用的关键问题。通过分析表明,MICP作为地下水封油库渗流控制的一种辅助注浆方式,可以较为准确地控制围岩渗透性变化,达到对洞室涌水量有效控制的目的。

MICP技术应用于岩体裂隙灌浆的现场试验研究

利用微生物诱导产生碳酸钙沉淀(MICP)技术对岩体裂隙进行灌浆,具有浆液黏度低、可灌性好、绿色环保等优点。结合现场试验开展微生物菌种的提取、活化培养和扩大培养等工作,对微生物菌液培养的最适条件进行探讨,并制备能用于现场灌浆的微生物浆液,结合现场岩体裂隙分布特征进行微生物浆液的岩体裂隙灌浆现场试验。结果表明:利用当地菌种制备形成的微生物浆液初始粘度为2 mPa·s~3 mPa·s,具有良好的可灌性;以重复多次灌注和每次定量灌注为主要特征的微生物灌浆施工工艺能适用于岩体0.2 mm以下微小裂隙灌浆,且扩散距离可达到0.4 m以上,灌后岩体透水率可达到0.1 Lu量级,防渗效果显著,为开度小于0.2 mm的岩体裂隙防渗加固处理提供了一种新的技术手段。

椰壳纤维-MICP复合改良膨胀土膨胀特性研究

采用椰壳纤维联合微生物诱导碳酸钙沉积(MICP)技术对南水北调中线工程南阳段的膨胀土进行试验改良,对素土、纤维土、MICP土以及椰壳纤维-MICP复合改良土开展无荷膨胀率试验和有荷膨胀率试验,研究改良前后膨胀土无荷膨胀率、有荷膨胀率随纤维掺量的变化规律,并对比分析单一改良方式和复合改良方式下纤维掺量对膨胀土膨胀特性的影响,最后通过电镜扫描试验,观察土样微观结构,揭示纤维-MICP复合改良膨胀土特性的内在机理。结果表明:单掺椰壳纤维和MICP技术改良均可抑制膨胀土的膨胀性能,而椰壳纤维-MICP复合改良土的改良效果最明显,且随着纤维掺量的增加,纤维土和复合改良土的无荷膨胀率和有荷膨胀率呈现出先减后增的趋势,纤维最佳掺量为0.5%,电镜扫描试验显示椰壳纤维可发挥桥联的作用以增强MICP膨胀土的改良效果。

天然海水环境下离子浓度对MICP反应的影响

微生物岩土技术通过生物矿化过程改善基础材料的力学性质,使其更适用于建筑或解决多学科领域的环境问题。微生物矿化过程中产生的碳酸钙是改善基础材料力学性质的主要成分,但其生成量及形态等受多种因素的影响。通过离子计、pH计、SEM、EDS和XRD等手段探究天然海水和去离子水环境在矿化过程中氯化钙和尿素浓度、比例及菌液和胶结液(氯化钙、尿素)体积比等因素对沉淀物质形貌及晶体组成的影响。结果表明:钙离子和尿素浓度及比例低时,碳酸钙的产率较高,但当初始钙离子、尿素浓度超过1.0 mol/L时,离子浓度增大对细菌产脲酶有抑制作用,浓度越高对脲酶的抑制作用越明显,沉淀物产率也随之减小,海水环境总体沉淀量与沉淀效率均高于去离子水环境。菌胶结液体积比去离子水中为1∶4、海水中不高于1∶10时,碳酸钙生成量较高,去离子水环境晶型以方解石为主,海水环境晶型以球霰石为主且沉淀中含有镁盐。

Quantitatively characterizing sandy soil structure altered by MICP using multi-level thresholding segmentation algorithm

The influences of biological,chemical,and flow processes on soil structure through microbially induced carbonate precipitation(MICP)are not yet fully understood.In this study,we use a multi-level thresholding segmentation algorithm,genetic algorithm(GA)enhanced Kapur entropy(KE)(GAE-KE),to accomplish quantitative characterization of sandy soil structure altered by MICP cementation.A sandy soil sample was treated using MICP method and scanned by the synchrotron radiation(SR)micro-CT with a resolution of 6.5 mm.After validation,tri-level thresholding segmentation using GAE-KE successfully separated the precipitated calcium carbonate crystals from sand particles and pores.The spatial distributions of porosity,pore structure parameters,and flow characteristics were calculated for quantitative characterization.The results offer pore-scale insights into the MICP treatment effect,and the quantitative understanding confirms the feasibility of the GAE-KE multi-level thresholding segmentation algorithm.

Effect of drying-wetting cycles on pore characteristics and mechanical properties of enzyme-induced carbonate precipitation-reinforced sea sand

Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical applications.However,the durability and microscopic characteristics of EICP-treated specimens against the impact of drying-wetting(D-W)cycles is under-explored yet.This study investigates the evolution of mechanical behavior and pore charac-teristics of EICP-treated sea sand subjected to D-W cycles.The uniaxial compressive strength(UCS)tests,synchrotron radiation micro-computed tomography(micro-CT),and three-dimensional(3D)recon-struction of CT images were performed to study the multiscale evolution characteristics of EICP-reinforced sea sand under the effect of D-W cycles.The potential correlations between microstructure characteristics and macro-mechanical property deterioration were investigated using gray relational analysis(GRA).Results showed that the UCS of EICP-treated specimens decreases by 63.7% after 15 D-W cycles.The proportion of mesopores gradually decreases whereas the proportion of macropores in-creases due to the exfoliated calcium carbonate with increasing number of D-W cycles.The micro-structure in EICP-reinforced sea sand was gradually disintegrated,resulting in increasing pore size and development of pore shape from ellipsoidal to columnar and branched.The gray relational degree suggested that the weight loss rate and UCS deterioration were attributed to the development of branched pores with a size of 100-1000 m m under the action of D-W cycles.Overall,the results in this study provide a useful guidancee for the long-term stability and evolution characteristics of EICP-reinforced sea sand under D-W weathering conditions.

Spatio-Temporal Characteristics of Heavy Precipitation Forecasts from ECMWF in Eastern China

This study examines the spatio-temporal characteristics of heavy precipitation forecasts in eastern China from the European Centre for Medium-Range Weather Forecasts(ECMWF) using the time-domain version of the Method for Object-based Diagnostic Evaluation(MODE-TD). A total of 23 heavy rainfall cases occurring between 2018 and 2021 are selected for analysis. Using Typhoon “Rumbia” as a case study, the paper illustrates how the MODE-TD method assesses the overall simulation capability of models for the life history of precipitation systems. The results of multiple tests with different parameter configurations reveal that the model underestimates the number of objects’ forecasted precipitation tracks, particularly at smaller radii. Additionally, the analysis based on centroid offset and area ratio tests for different classified precipitation objects indicates that the model performs better in predicting large-area, fast-moving, and longlifespan precipitation objects. Conversely, it tends to have less accurate predictions for small-area, slow-moving, and shortlifespan precipitation objects. In terms of temporal characteristics, the model overestimates the forecasted movement speed for precipitation objects with small-area, slow movement, or both long and short lifespans while underestimating it for precipitation with fast movement. In terms of temporal characteristics, the model tends to overestimate the forecasted movement speed for precipitation objects with small-area, slow movement, or both long and short lifespans while underestimating it for precipitation with fast movement. Overall, the model provides more accurate predictions for the duration and dissipation of precipitation objects with large-area or long-lifespan(such as typhoon precipitation) while having large prediction errors for precipitation objects with small-area or short-lifespan. Furthermore, the model’s simulation results regarding the generation of precipitation objects show that it performs relatively well in simulating the generation of large-area and fast-moving precipitation objects. However, there are significant differences in the forecasted generation of small-area and slow-moving precipitation objects after 9 hours.

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.

Assessment of Wet Season Precipitation in the Central United States by the Regional Climate Simulation of the WRFG Member in NARCCAP and Its Relationship with Large-Scale Circulation Biases

Assessment of past-climate simulations of regional climate models(RCMs)is important for understanding the reliability of RCMs when used to project future regional climate.Here,we assess the performance and discuss possible causes of biases in a WRF-based RCM with a grid spacing of 50 km,named WRFG,from the North American Regional Climate Change Assessment Program(NARCCAP)in simulating wet season precipitation over the Central United States for a period when observational data are available.The RCM reproduces key features of the precipitation distribution characteristics during late spring to early summer,although it tends to underestimate the magnitude of precipitation.This dry bias is partially due to the model’s lack of skill in simulating nocturnal precipitation related to the lack of eastward propagating convective systems in the simulation.Inaccuracy in reproducing large-scale circulation and environmental conditions is another contributing factor.The too weak simulated pressure gradient between the Rocky Mountains and the Gulf of Mexico results in weaker southerly winds in between,leading to a reduction of warm moist air transport from the Gulf to the Central Great Plains.The simulated low-level horizontal convergence fields are less favorable for upward motion than in the NARR and hence,for the development of moist convection as well.Therefore,a careful examination of an RCM’s deficiencies and the identification of the source of errors are important when using the RCM to project precipitation changes in future climate scenarios.

Impacts of Future Changes in Heavy Precipitation and Extreme Drought on the Economy over South China and Indochina

Heavy precipitation and extreme drought have caused severe economic losses over South China and Indochina(INCSC)in recent decades.Given the areas with large gross domestic product(GDP)in the INCSC region are distributed along the coastline and greatly affected by global warming,understanding the possible economic impacts induced by future changes in the maximum consecutive 5-day precipitation(RX5day)and the maximum consecutive dry days(CDD)is critical for adaptation planning in this region.Based on the latest data released by phase 6 of the Coupled Model Intercomparison Project(CMIP6),future projections of precipitation extremes with bias correction and their impacts on GDP over the INCSC region under the fossil-fueled development Shared Socioeconomic Pathway(SSP5-8.5)are investigated.Results indicate that RX5day will intensify robustly throughout the INCSC region,while CDD will lengthen in most regions under global warming.The changes in climate consistently dominate the effect on GDP over the INCSC region,rather than the change of GDP.If only considering the effect of climate change on GDP,the changes in precipitation extremes bring a larger impact on the economy in the future to the provinces of Hunan,Jiangxi,Fujian,Guangdong,and Hainan in South China,as well as the Malay Peninsula and southern Cambodia in Indochina.Thus,timely regional adaptation strategies are urgent for these regions.Moreover,from the sub-regional average viewpoint,over two thirds of CMIP6 models agree that maintaining a lower global warming level will reduce the economic impacts from heavy precipitation over the INCSC region.