In the present study, the performance of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models in simulating the seasonal cycle of the South China Sea (SCS) monsoon is evaluated by comparing the model outputs with observations, the NCEP–NCAR reanalysis, and the National Oceanic and Atmospheric Administration (NOAA) Outgoing Longwave Radiation (OLR)-Climate Data Record (CDR). The results indicate that there exist differences in the performance of models for various SCS monsoon indices. The models with the best performance for simulating the zonal circulation index (ZCI) and meridional circulation index (MCI) are TaiESM1 and CMCC-CM2-SR5 respectively, while ACCESS-CM2 and GISS-E2-1-G exhibit better performance for simulating the convection index (CI) than other CMIP6 models selected in this study. Additionally, the multimodel ensemble mean (MME) can replicate the seasonal cycles of the SCS monsoon well, yet both convection and circulation present a considerable bias in May, during the SCS summer monsoon onset period. The biases associated with the three physical processes, namely the sea–land thermal contrast, the northward-propagating intraseasonal oscillation (ISO), and the convection of Bay of Bengal, contribute significantly to the large bias of ZCI. However, only the biases related to the convection of Bay of Bengal and the sea–land thermal contrast have a significant impact on the large biases of MCI in May. The large biases of CI are mainly attributed to the bias of the convection of Bay of Bengal, while the northward-propagating ISO plays a supplementary role.

Previous studies have proposed several well-recognised mechanisms for the northward-propagating boreal summer intraseasonal oscillations (BSISOs), while their relative roles tend to be qualitatively analysed. In the present study, based on the planetary boundary layer (PBL) moisture mode theory and the associated moisture budget equation, we quantitatively calculated the contribution of each mechanism, including PBL moisture advection, vertical easterly wind shear, vorticity advection, and external sea surface temperature (SST) forcing, to the northward propagation of BSISO by using the Japanese 55-year reanalysis (JRA-55). The results show that the dominant mechanisms are the vertical easterly wind shear effect (51.75%-56.1% of the positive contribution) and the SST forcing (18.89%-23.6%) over the Indian Ocean, the vertical easterly wind shear effect (40.72%-51.87%) and the vorticity advection effect (24.65%-31.4%) over the South China Sea, and the vorticity advection effect (56.37%-65.67%) and the air-sea interaction (19.92%-22.2%) over the western North Pacific, which favour the PBL moisture asymmetry, and then the northward-propagating BSISOs. Moisture advection is a supplementary mechanism, while the contributions of vertical moisture advection and nonlinear effects can be ignored in all three regions. These results help us to further understand the northward propagation mechanism of ISO in the Asia-Pacific monsoon region, provide a clear reference for diagnosing persistent extreme weather associated with ISO, and provide quantitative criteria for evaluating tropical ISO propagation in numerical models.

The absence of robust quantitative evaluation methods has led to insufficient knowledge of models capability on the rapid intensification (RI) prediction of tropical cyclones (TCs). In this study, we propose a method and define some indicators aiming to evaluate model capability on predicting RI in a more accurate manner. An assessment of model predictive capability on RI of TCs based on 10 years of operational forecasts has been conducted using different RI criteria. The Tropical Regional Atmosphere Model for the South China Sea of China Meteorological Administration (CMA-TRAMS) and the European Centre for Medium -Range Weather Forecasts (ECMWF) high resolution (HRES) operational forecasts were used. Analysis results revealed that the criterion of 6 -hour sea level pressure (SLP) change is more appropriate to be used in RI operational forecast. The maximum lead time (MLT) of CMA-TRAMS and HRES was 72 and 78 h, and the maximum deviation of RI occurrence time of CMA-TRAMS and HRES was 48 h delay and 24 h ahead, respectively. Overall results suggest that the model predictive capability of RI is currently limited, and both models have inadequate capability in providing sufficient heat and energy to support RI in the long run. A tendency of CMA-TRAMS to have a lag in RI occurrence time was also demonstrated due to an air-sea interaction lag resulting from the fixed skin sea surface temperature used. Results of the present study provide insights and could be the basis for future efforts on improving parametrization schemes for properly describing RI process of TCs.

In the present study, we focused on the heat waves (HW) associated with the quasi-biweekly (QBW, 10–20-day period) variability (QBW-HW) over Southern China (SC, 102º–120ºE, 21º–30ºN) in the Flexible Global Ocean–Atmosphere–Land System Model, GridPoint version 3 (FGOALS-g3), and the HW-associated structures and surface air temperature budget investigated by using model outputs from historical experiment of Coupled Model Intercomparison Project Phase 6 (CMIP6). We found that the anomalous circulations related to the QBW-HW events over SC are closely linked to the southeastward propagation of the wave train from mid-high latitudes and the northwestward-propagating disturbances from the tropics. The results also showed that adiabatic and diabatic heating play a key role in the QBW-HW over SC. These results are in good agreement with observations from previous studies. In addition, QBW-HWs are dry in the FGOALS-g3 model, while observed humid HWs occur over SC. The difference is mainly due to the new boundary layer scheme incorporated in the FGOALS-g3 model, which overestimates the entrainment process at the top of the boundary layer during the QBW-HW over SC, resulting in more and drier air into the boundary layer, and thus less moisture. It implies that the entrainment equation at the top of the boundary layer in the FGOALS-g3 model does need to be improved to be suitable for humid HW processes, although the boundary layer scheme can improve the model precipitation and radiative forcing.

This study investigates the physical mechanisms for the persistent heavy rainfall (PHR) events over South China (SC) associated with the 10–30-day intraseasonal oscillation (ISO) before the South China Sea Summer Monsoon (SCSSM) onset (SCSSM-I) and after the SCSSM onset (SCSSM-II) in the first rainy season (April–June). About 25.0

The impact of sea surface temperature(SST)on winter haze in Guangdong province(WHDGD)was analyzed on the interannual scale.It was pointed out that the northern Indian Ocean and the northwest Pacific SST play a leading role in the variation of WHDGD.Cold(warm)SST anomalies over the northern Indian Ocean and the Northwest Pacific stimulate the eastward propagation of cold(warm)Kelvin waves through the Gill forced response,causing Ekman convergence(divergence)in the western Pacific,inducing abnormal cyclonic(anticyclonic)circulation.It excites the positive(negative)Western Pacific teleconnection pattern(WP),which results in the temperature and the precipitation decrease(increase)in Guangdong and forms the meteorological variables conditions that are conducive(not conducive)to the formation of haze.ENSO has an asymmetric influence on WHDGD.In El Ni?o(La Ni?a)winters,there are strong(weak)coordinated variations between the northern Indian Ocean,the northwest Pacific,and the eastern Pacific,which stimulate the negative(positive)phase of WP teleconnection.In El Ni?o winters,the enhanced moisture is attributed to the joint effects of the horizontal advection from the surrounding ocean,vertical advection from the moisture convergence,and the increased atmospheric apparent moisture sink(Q2)from soil evaporation.The weakening of the atmospheric apparent heat source(Q1)in the upper layer is not conducive to the formation of inversion stratification.In contrast,in La Ni?a winters,the reduced moisture is attributed to the reduced upward water vapor transport and Q2 loss.Due to the Q1 increase in the upper layer,the temperature inversion forms and suppresses the diffusion of haze.

In this study, persistent rainfall (PR) over South China (SC) is divided into two types. One type occurs multiple times in succession [defined as multiple PR (MPR)]; another type represents isolated PR (IPR), for which no new PR occurs for 10 days after the previous PR. The spatiotemporal structures of the 10-30-day intraseasonal oscillations (ISOs) associated with the two types of PR are compared and analyzed. The results reveal that the low-level moisture and air temperature perturbations always have a leading phase relative to the anomalous precipitation. In addition, the positive low-level moisture tendency appears in the MPR ending phase, whereas that in the IPR is close to zero. This difference results in convective development after the MPR ending phase, though not after the IPR. The moisture budget shows that the difference in moisture tendency between MPR and IPR is mainly due to meridional advection, including advections by the mean meridional flow across the perturbation moisture gradient and by the perturbation meridional flow across the mean moisture gradient. For the former, the difference is attributed to the perturbation moisture gradients, while the mean moisture gradients are responsible for the difference of the latter. Furthermore, an essential cause of the difference is the influence of higher-latitude disturbances that affect the IPR more significantly than the MPR. Two associated mechanisms are proposed. One is the perturbation stacking effect, and the other is the effect of angular momentum conservation. By contrast, the low-level temperature anomalies are not the key factor causing the difference between MPR and IPR.

In this study, the flood season in South China (SC) was divided into three stages: two first rainy seasons (FRSs) around the South China Sea summer monsoon onset and one second rainy season when Typhoon prevails, denoted as FRS1, FRS2, and SRS, respectively, and then we diagnosed the moist static energy (MSE) budget associated with the 10–30‐day persistent heavy rainfall (PHR) over SC during these periods. The results indicate that there are great differences in the recharge of PHR‐related MSE in different stages of the flood season in SC: The FRS1 MSE associated with PHR moves southeastward from midlatitude; the large MSE is maintained in SC during the FRS2; during the SRS, the MSE perturbation propagates from the tropical western North Pacific to SC. From the perspective of the local MSE budget in SC, meridional and zonal advection play a key role in the maximum MSE change in the FRS1; the FRS2 and SRS MSE tendency is mainly determined by zonal advection and meridional advection, respectively. In contrast, the 10–30‐day propagating perturbation of MSE changes during both the FRS1 and FRS2 are mainly affected by the zonal advection, while the meridional circulation is dominant in the SRS. The cumulative contribution of external forcing (including radiation and surface heat fluxes) during the SRS to the propagation of PHR‐related MSE perturbation can reach more than 30%, and the closer to the land, the stronger the external forcing. During the FRS (including FRS1 and FRS2), however, the external forcing contributes little, even negatively.

针对登陆华南台风降水及模式预报存在的突出问题,就当前关于登陆台风降水分布的不对称性及台风登陆后期持续性暴雨发生机理的研究状况进行回顾和分析,提出了需要深入研究的相关科学问题及模式预报技术改进的应对措施,为促进登陆华南台风暴雨预报工作和效果的不断改进提供参考.分析指出环境风场垂直切变、低层气团边界(如冷池边界)、干冷空气侵入、中尺度对流系统以及地形等是造成登陆华南台风降水不对称分布的重要影响因素.台风登陆后期华南发生的持续性暴雨往往与季风活动增强相关,活跃的西南季风为强降水中尺度对流系统(MCSs)发展提供有利条件,MCSs通过潜热加热反馈于大尺度环流,可使台风涡旋环流和西南季风得以维持并致使MCSs反复发生发展、暴雨持续.开展相关科学问题的深入研究,有针对性地考察评估目前模式的预报性能并提出有效改进方案,是进一步提高模式预报效果的重要途径.

利用1961-2017年中国地面观测站日降水资料、全球大气多要素和海表温度月资料,分析华南区域持续性强降水过程的气候特征,诊断并比较与华南前汛期、后汛期区域持续性强降水年际变化相关的大气环流和海表温度异常特征.结果表明,3-12月华南都可能出现持续性强降水过程,其中汛期4-9月的占了 94.4％.伴随着区域持续性强降水的年际变化,华南本地垂直上升运动显著异常是前汛期和后汛期的共同点,但前汛期、后汛期在华南及周边环流异常、水汽输送来源以及海温异常分布等方面都存在一定差异.在前汛期华南区域持续性强降水偏重年,赤道西太平洋区域海温偏低,由于大气罗斯贝波响应使西太平洋副热带高压偏强,热带西太平洋向华南区域水汽输送加强,从而有利于区域持续性强降水偏重.后汛期华南区域持续性强降水偏重年的海温异常分布是赤道中东太平洋区域正异常、东印度洋至西太平洋暖池区负异常,海温异常通过西北太平洋副热带高压、南海热带季风强度、水汽输送和垂直环流等多方面,导致后汛期区域持续性强降水偏重.

利用2018年1月1日至12月31日逐小时欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代全球大气再分析产品——ERA5和中国气象局多源降水分析系统(CMA multi-source precipitation analysis system,CMPAS)中逐小时降水产品(CMPAS-hourly),采用基于大气水物质收支平衡方程的水物质评估方法对广东2018年空中云水资源及空中水汽、水凝物时空分布进行评估.对广东省整体而言,2018年水汽降水效率为5.1％,水凝物降水效率为89.6％,水汽和水凝物都为净输出.从空间分布来看,水汽总量自西南向东北逐渐减少,水凝物总量高值区在粤西云雾山、天露山及粤东莲花山的南坡,云水资源总量从北部山区向沿海地区逐渐减小,水凝物降水效率从沿海地区向北部山区逐渐减小.从时间变化来看,水汽总量在夏季最大,水凝物总量在8月下半月和9月上半月最大,云水资源总量非汛期高于汛期;水汽和云水资源的变化月内尺度大于天气尺度,水凝物的变化天气尺度大于月内尺度.

基于1979-2020年逐日的NOAA向外长波辐射资料、NCEP/NCAR再分析风场资料,以及全球CMAP再分析降水资料,探讨了气候态亚洲热带夏季风涌的传播过程及与我国夏季相应的降水联系.分析结果表明,主汛期亚洲热带气候态夏季风季节内振荡(CISO)活动是亚洲夏季风活动的主要特征,随时间北传的亚洲热带夏季风CISO称为亚洲热带夏季风涌,主要有南亚夏季风涌和南海夏季风涌.亚洲热带夏季风涌的传播可分为四个阶段.在亚洲热带夏季风涌的发展阶段,印度洋区域低频气旋与对流活跃,孟加拉湾和南海热带区域被低频东风控制,我国大部分地区无降水发生,降水中心位于两广地区.当进入亚洲热带夏季风涌活跃阶段,孟加拉湾和南海热带地区低频气旋和对流活跃,东亚低频"PJ"波列显著,我国降水中心北移到长江以南的附近区域.亚洲热带夏季风涌减弱阶段,孟加拉湾与南海低频气旋消亡,对流减弱,低频西风加强,日本南部附近为低频反气旋控制,我国长江中下游低频南风活跃,降水中心也北移到长江中下游地区,而华南地区已基本无降水,此阶段的大气低频环流场与亚洲热带夏季风涌发展阶段基本相反.进入亚洲热带夏季风涌间歇阶段时,孟加拉湾和南海热带地区低频反气旋活跃,对流不显著,日本南部附近的低频反气旋北移减弱,我国东部基本在低频南风的控制下,降水中心也逐步北移到华北-朝鲜半岛一带,此时的大气低频环流场与亚洲季风涌活跃阶段基本相反.

In the present study, the structures and mechanisms of the heatwaves (HWs) associated with the quasi-biweekly (QBW; 10-20-day period) variability (QBW-HW) over southern China (SC; 106 degrees-120 degrees E, 21 degrees-30 degrees N) are investigated by using observation data from surface stations in China and the related gridded dataset (CN05.1), and the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis. We found that the strongest anticyclonic anomaly and subsidence appear over SC during the developing phase of QBW-HW, and then induced excess solar radiation at surface and significant diabatic heating lead to a positive surface air temperature change, thus favoring occurrence of QBW-HW over SC. In addition, we found a wet near-surface atmosphere in the QBW-HW events over SC, and further confirmed that near-surface moisture should play an important role in the occurrence of QBW-HW, via absorptions of longwave and shortwave radiation. This result is quite different from previous studies since they did not pay attention to the near-surface moisture. On the other hand, warmer SAT favors more water vapor evaporated from the moist soil when considering the Clausius-Clapeyron relationship. Then, the positive feedback processes promote the occurrence of QBW-HW over SC. In contrast, during the developing and warm phases of QBW-HW over SC, except for the near-surface level, the troposphere is in a dry condition, even at 850 and 700 hPa. In the QBW-HW events over SC, the factor responsible for the wet near-surface atmosphere is the enhanced surface evaporation, which is attributed to strengthened surface wind speed and background moist soil. Significance StatementUnder the background of global warming, heatwaves over Southern China are experiencing an increasing trend. In this study, we want to understand the structures and mechanisms of the heatwaves related to 10-20-day (quasi-biweekly) variability. We that found some structures of heatwaves (e.g., anticyclonic anomalies along with subsidence) are consistent with previous studies. In addition, we also show that the moist soil and increased induced near-surface moisture play a key role in the occurrence of heatwaves over Southern China, via enhanced absorptions of longwave and shortwave radiation. This study is helpful for understanding the processes and prediction of heatwaves over Southern China. Future work should examine the findings by some numerical experiments with a climate model.

In the present study, the moist static energy (MSE) budget associated with a persistent rainfall event that occurred over South China in late August 2018 (PR1808) was analyzed using ERA-Interim reanalysis data. The results revealed that the PR1808 event was closely related to a 12–30-day intraseasonal oscillation (ISO), with a significant westward-propagating mode. The recharge of MSE occurred before ISO deep convection, and the MSE was discharged during and after the peak precipitation. This result indicates that the recharge-discharge cycle of MSE played an important role in regulating the high-frequency ISO (HF-ISO) process during the PR1808 event. However, the mid-level MSE tendency, rather than the low-level tendency, controlled the column-integrated MSE change in this case, and there was no low-level MSE tendency ahead of HF-ISO convection, which is different from previous studies, implying that shallow convection was not a key factor in this case. The recharge of MSE related to the mid-level MSE change mode was mainly attributed to zonal advection, while the forcing related to radiative heating (longwave and shortwave radiation) and heat fluxes (latent and sensible heat fluxes) contributed little to the change in MSE. Furthermore, for the zonal advection of MSE, the main contribution originated from the advection by the low-frequency zonal flow across the low-frequency MSE gradient, and interactions between high- (low-) frequency zonal flow and low- (high-) frequency MSE. In addition, the disturbances from higher latitudes enhanced the persistent rainfall in this case over South China through the southward shift of baroclinic vorticity.

利用重建的华南区域黑碳气溶胶(Black Carbon,BC)浓度资料,分析其与南海夏季风在年际尺度上的关系.结果 表明,华南区域BC浓度与南海夏季风的关系在2000年前后有明显的突变,由显著负相关变为显著正相关,即由高BC浓度弱季风变为高BC浓度强季风.通过合成对比分析,发现1988-1999年(第一时间段)的华南BC主要气候效应是间接辐射强迫作用:华南BC使云粒子半径减小,抑制华南区域春季降水,增加了云的生命期,从而使到达地面的短波辐射减少,表面和低层大气降温.负温度异常激发了异常反气旋,在南海区域即有东风异常.到夏季,东风异常减弱了季风强度,同时抑制了南海地区的降水.2000-2010年(第二时间段)的华南BC主要气候效应是直接辐射强迫作用:春季高BC浓度通过直接气候效应,增暖大气,加强降水,但是雨日减少,从而使到达地面的短波辐射增多,表面和低层大气增温.正温度异常激发了异常气旋,在南海区域即有西风异常一直维持到夏季,增大了季风强度,同时增强了南海地区的降水.

Regional persistent heat event is extensively studied and its intensity is normally investigated from the view of regional average. Climatic characteristics of persistent heat event in 4 regions in the eastern China are analyzed on the basis of distinguishing historical persistent heat event in the South China, the Yangtze River, the Huanghuai and the North China, using the daily maximum temperature data of 2407 stations in China during 1961-2019. The definition index of regional persistent heat event is established, in which the proximity of high temperature stations, the spatial range, the temporal consistency, the regional climate characteristics and the universality of methods are synthesized. Average times of regional persistent heat event in the South China, the Yangtze River, the Huanghuai and the North China are 3.3, 2.8, 2.2 and 0.8 per year respectively, with an average duration of 5.1 d, 6.4 d, 5.0 d and 3.9 d for per event, and the average annual cumulative days in climatology are 16.8 d, 17.8 d, 11.0 d, 3.1 d. Both the duration and the average annual cumulative days of persistent heat event are the longest in the Yangtze River, indicating that the persistent heat event in the Yangtze River is the most serious in climatology among these regions. The average annual cumulative days of persistent heat event in the North China are the least, and it usually ends at the end of July or before. There is a significant linear growing trend in the persistent heat event index in the South China, the North China, and the Yangtze River. There are only 4 non-summer persistent heat events in the Huanghuai in recent 20 years. The difference in strength of the persistent heat event index between the Yangtze River and the South China has significant inter-decadal trends. The index in the Yangtze River is obviously stronger than that in the South China during the first period of 1961-1978, while the index in the South China is slightly stronger than that in the Yangtze River during the second period of 1979-2019. The difference of persistent heat event between these two regions changes by nearly 10 d over these years.

We propose an initialisation scheme for weak tropical cyclones (TCs) in the South China Sea (SCS) by combining composite and analysis vortices to improve forecasts of weak TCs in the region. The composite vortex is obtained from good samples of analyses of TCs in the SCS, and the analysis vortex is obtained from either European Centre for Medium‐Range Weather Forecasts (ECMWF) analysis data or an operational assimilation system. The new scheme has been applied to 57 cases of weak TCs, and the effect on the forecasting of four tropical storms has been studied in detail. It can be concluded that the proposed scheme can reduce track errors and intensity errors of weak TCs, compared with the control experiment. The possible reasons for these results are investigated in a case study for Linfa. Results of batch experiments show that the new method significantly improves TC track forecasting of tropical storms, severe tropical storms and typhoons, and demonstrates significant advantages in forecasting intensity of tropical storms, compared with the control experiment. It also performs better in predicting intensity of TCs in the SCS compared with ECMWF Atmospheric Model high resolution.

利用1961-2017年共57年中国地面观测站日降水资料,采用滑动平均、百分位和点面相关分析等方法,根据延伸期预报特点以及监测预报和研究需求,着眼于体现强降水过程的区域性、持续性和致灾性,并兼顾区域气候特征和普适性,建立区域持续性强降水过程定义指标.根据该指标查找判断我国东部四个关键区域(华南、长江、黄淮、华北)的历史降水过程,1961—2017年期间共有557次区域持续性强降水过程,平均每年约10次,其中华南、长江、黄淮、华北分别有267、155、78、49次,平均每年各有4.7次、2.7次、1.4次和0.9次,呈由南向北递减的分布.统计评估结果表明,该指标能客观地判断出持续影响同一区域的相对稳定类型的大尺度持续性强降水过程,适用于延伸期业务服务和研究.

In the present study, the northward-propagating intraseasonal oscillations (ISOs) over the South China Sea (SCS) during the summer monsoon season are divided into two types. One is the northward propagation of ISOs confined in the SCS (defined as P1-ISO), another for ISOs moving from the SCS to Southern China (SC) defined as P2-ISO. The spatial and temporal structures of the two types of ISOs are compared based on the analysis of the NCEP–NCAR reanalysis datasets. It is found that a significant difference appears in the heat flux anomalies over SC that is attributed to the cloud-radiation effect. A mechanism associated with the changes in the convective instability is proposed to understand the cause of the northward propagation of the ISO from the SCS to SC. For the P1-ISO, a more precipitation over SC leads to a less surface solar radiation and then a cold land surface temperature (LST), which induces an increase of static stability via surface longwave radiation and sensible heat flux. Whereas the total contribution to the convective instability changes does create an unfavorable for ISOs propagating northward, the moisture convergence, mainly controlled by the baroclinic vorticity advection effect, may contribute to an increase of convective instability that favors the ISOs moving northward. For the P2-ISO, a less precipitation over SC results in a more shortwave radiation reaching the ground that induces a warm LST, and thus leading to a warm low-level air temperature and destabilizing the atmosphere ahead of the convection. Moreover, the moisture convergence, dominated by the warm low-level air temperature, also contributes to the increase of convective instability. Thus the convective instability increment should favor the ISOs moving northward. It is worth noting that the baroclinic vorticity advection and moisture advection are not essential for ISOs propagating from the SCS to SC.

Land–sea thermal contrast is one of the key factors modulating the onset and strength of summer monsoons. This study investigates the precursory thermal-contrast signal of the onset of the South China Sea summer monsoon (SCSSM) and reveals that the land–sea thermal contrastDT(ToceanminusTlandat the surface) in March tracks the date of the monsoon onset very well. In an energy-balance framework, the monthly anomalies in this thermal contrast are decomposed into different components associated with the anomalies of various radiative and nonradiative dynamical processes over the South China Sea in early spring. It is found that the interannual variations ofDT, and thus the onset date of monsoon, are mainly tied to the anomalies in surface heat fluxes, ocean–land heat storage rate, and oceanic dynamical processes. The variation of ocean–land heat storage rate and ocean dynamics is the largest positive contributor to the change inDT. Specifically, an early SCSSM onset tends to be associated with an amplified “cold-land, warm-ocean” pattern that can be further attributed to increased soil moisture content in March, which enhances land surface cooling and weakens oceanic heat storage rate that benefits ocean surface warming. Furthermore, the variations ofDTand soil moisture content in March are positively related with the late-February precipitation over the Indochina Peninsula, which could therefore be regarded as a precursory signal for both the land–sea thermal contrast in March and the onset of the SCSSM.