硫酸型酸雨参与碳酸盐岩溶蚀的研究进展

碳酸盐岩的H2CO3溶蚀产生岩溶碳汇,占整个岩石风化碳汇的 94%。西南岩溶区硫酸型酸雨严重,硫酸型酸雨广泛参与碳酸盐岩的溶蚀。H2SO4参与的碳酸盐岩风化是一个大气CO2净释放过程,具有减汇作用巨大。另一方面,岩溶区石灰土壤和地下水具有较高的pH值及盐基饱和度,对H+有巨大的缓冲作用,大气酸沉降在碳酸盐岩地区可能并不会造成地下水的HCO3-和pH降低;相反,较高浓度的SO42-所产生的盐效应和SO2-4与各种阳离子形成的离子对会增大方解石、白云石溶解度,可增强H2CO3对碳酸盐的溶蚀,这可能会使岩溶作用产生更大的碳汇效应。因此,硫酸型酸雨参与碳酸盐岩风化的减汇效应不仅可能被高估,硫酸型酸雨还可能增强碳酸盐岩的H2CO3溶蚀,具有增加岩溶碳汇效应的作用。应结合石灰土壤对大气酸沉降的缓冲容量和阈值及大气酸沉降的H+与土壤中盐基离子的交换量,并综合考虑盐效应、离子对作用、同离子效应,客观评价硫酸型酸雨流经石灰土壤层后对碳酸盐岩溶蚀吸收大气/土壤CO2的影响      

边界层过程对"98·7"长江流域暴雨预报影响的数值试验研究

通过ETA模式对"98@7"长江流域暴雨过程的数值试验研究,讨论了行星边界层过程对暴雨数值预报的影响,结果表明边界层过程在这次暴雨预报中有重要作用.具体结论为:(1)降水大范围落区是受大尺度流场所决定的,但边界层过程对暴雨预报具有重要的作用;(2)不考虑边界层过程会影响对天气系统的正确预报,包括影响大气低层的运动场、水汽及大气不稳定度,从而影响暴雨的预报;(3)从时间层次上看,由于地表通量有着显著的日变化,边界层过程的作用不仅与暴雨本身发生发展及消亡的阶段有关,也与各阶段的时间(白天或夜间)有联系;(4)在空间范围内,边界层过程对大气的影响是通过大气流场重新分布来影响降水的环境条件,故地表通量分布和低层流场的相互配置作用十分重要.长江南北的情况有所不同,长江流域南侧区是地表通量的大值区,也是长江流域雨区水汽和不稳定能量的源区,它对长江流域的暴雨可能有着更为重要的作用.     

Comparative Analysis of the Generalized Omega Equation and Generalized Vertical Motion Equation

Research on vertical motion in mesoscale systems is an extraordinarily challenging effort. Allowing for fewer assumptions, a new form of generalized vertical motion equation and a generalized Omega equation are derived in the Cartesian coordinate system(nonhydrostatic equilibrium) and the isobaric coordinate system(hydrostatic equilibrium),respectively. The terms on the right-hand side of the equations, which comprise the Q vector, are composed of three factors:dynamic, thermodynamic, and mass. ...     

Variability of Raindrop Size Distribution during a Regional Freezing Rain Event in the Jianghan Plain of Central China

The characteristics of the raindrop size distribution(DSD) during regional freezing rain(FR) events that occur throughout the phase change(from liquid to solid) are poorly understood due to limited observations. We investigate the evolution of microphysical parameters and the key formation mechanisms of regional FR using the DSDs from five disdrometer sites in January 2018 in the Jianghan Plain(JHP) of Central China. FR is identified via the size and velocity distribution measured from a disdrom...     

Analysis of Precipitation Anomaly and a Failed Prediction During the Dragon-boat Rain Period in 2023

This study investigates the possible causes for the precipitation of Guangdong during dragon-boat rain period(DBRP) in 2022 that is remarkably more than the climate state and reviews the successes and failures of the prediction in2022. Features of atmospheric circulation and sea surface temperature(SST) are analyzed based on several observational datasets for nearly 60 years from meteorological stations and the NCEP/NCAR Global Reanalysis Data. Results show that fluctuation of the 200-h Pa weste...     

A MODELING STUDY OF PARAMETERIZATION SCHEMES FOR DEPOSITIONAL GROWTH OF ICE CRYSTAL: FOUR RAINFALL CASES OVER TROPICS AND MIDLATITUDES

Depositional growth of ice crystal is one of the major processes for development of precipitation systems and can be represented by depositional growth of cloud ice from cloud water (PIDW) and depositional growth of snow from cloud ice (PSFI) in cloud-resolving model. Four parameterization schemes are analyzed in the cloud-resolving model simulations of four rainfall cases over the tropics and midlatitudes. The comparison of time and model domain mean data shows that Shen’s scheme produces the closest rainfall simulation to the observation. Compared to Zeng’s scheme, Shen’s scheme improves the mean rain-rate simulation significantly through the dramatic decrease in depositional growth of cloud ice from cloud water. Compared to other schemes, Shen’s scheme produces the better rainfall simulation via the reduction in the mean rain rate associated with the enhanced gain of cloud water and ice.     

Evaluating the Ability of CRCM5 to Simulate Mixed Precipitation

Precipitation episodes in the form of freezing rain and ice pellets represent natural hazards affecting eastern Canada during the cold season. These types of precipitation mainly occur in the St. Lawrence River valley and the Atlantic provinces of Canada. This study aims to evaluate the ability of the fifth-generation Canadian Regional Climate Model (CRCM5), using a 0.11° horizontal grid mesh, to hindcast mixed precipitation when driven by reanalyses produced by the European Centre for Medium-range Weather Forecasts (ERA-Interim) for a 35-year period. In general, the CRCM5 simulation slightly overestimates the occurrence of freezing rain, but the geographical distribution is well reproduced. The duration of freezing rain events and accompanying surface winds in the Montréal region are reproduced by CRCM5. A case study is performed for an especially catastrophic freezing-rain event in January 1998; the model succeeds in simulating the intensity and duration of the episode, as well as the propitious meteorological environment. Overall, the model is also able to reproduce the climatology and a specific event of freezing rain and ice pellets.     

太行山地形影响下的极端短时强降水分析

2015年8月2日午夜和2011年8月9日前半夜,在两种不同天气系统背景下太行山东麓都出现了小时雨量超过50 mm的极端短时强降水天气,两次过程都是雷暴先在太行山区触发加强,经过下山2 h先后在丘陵站平山和山前平原站石家庄市区产生极端短时强降水。利用常规探测资料、地面加密观测资料、石家庄SA多普勒天气雷达资料,对不同天气系统背景下太行山特殊地形影响的极端短时强降水成因进行分析。结果表明:偏东气流被南北向的太行山地形强迫抬升,且与下山雷暴出流形成中尺度辐合线触发新的雷暴,雷达回波呈现后向传播特征和列车效应造成局地极端短时强降水。太行山地形通过增强辐合上升运动、增大垂直风切变使雷暴下山加强。不同天气系统强迫下,太行山特殊地形对雷暴发展作用不同。在偏西气流引导下,暖区极端短时强降水由阵风锋触发,具有突发性、降水时间短、伴随风力大的特点,下山雷暴出流加快且与山前偏东风的辐合加强,陆续在丘陵区和山前平原触发对流与下山雷暴合并加强造成极端短时强降水;而在东北气流引导下,回流冷锋和阵风锋共同触发的极端短时强降水具有持续时间较长、降雨总量较大、伴随风力较小的特点,太行山东坡对东北冷湿回流有阻挡积聚作用,东北偏北来的雷暴出流边界西端在迎风坡上强迫抬升使雷暴触发并加强,东北气流遇山后发生气旋性偏转使雷暴出流转向东南下山,与平原的偏东风辐合加强,造成丘陵区和山前平原的总降雨时间更长、降雨总量更大。     

一种浙江省冻雨落区的推算方法

2008年初浙江省出现全省性的大范围强冻雨天气,在输电线路上形成很厚的覆冰,致使浙江电网遭受巨大的损失。然而,浙江省却仅有三分之一的气象站观测到冻雨,持续时间也很短。本文利用全球再分析资料ERA-Interim结合浙江电网覆冰灾情资料,分析了2008和2013年的两次强冻雨过程。研究表明浙江省强冻雨发生时具备冷暖冷的层结结构,且中间暖层气温0℃,但相比湖南省,浙江省的暖层中心气温稍低,下层冷层厚度略厚,暖层中的液态水进人到下层冷层后易被冻结,落到低海拔地面为冰粒,或者低海拔地面层气温高于0℃,冻雨落到地面为降雨,所以冻雨期间浙江省绝大多数气象站(海拔在200 m以下)观测不到雨凇,观测到的多是冰粒或降雨;而在海拔较高的山区,冷层厚度变薄,液态水被冻结的概率大大降低,而且山区地面气温多低于0℃,有利于冻雨落在山区地面形成雨凇,因此浙江省冻雨多出现在浙中海拔400 m以上和浙南海拔600 m以上的山区。根据浙江省冻雨的特点,采用全球再分析资料进行冻雨落区推算,结果与浙江电网实际的覆冰灾情吻合得较好。本研究利用输电线路覆冰厚度确定冻雨强弱和分布,采用再分析资料推算冻雨落区,为地形起伏度较大的省份开展冻雨研究,进行冻雨监测和预报提供一条新的思路。     

地表水酸化的研究进展及其湖泊酸化的环境信息研究

通过对发达资本主义国家在其工业化进程中产生的地表水酸化、资源与环境的破坏以及相关研究进展等的简介 ,审视我国大气污染、酸雨的发展趋势 ,预估部分酸雨区存在地表水酸化的潜在危险性。据此以云南高原湖泊洱海和阳宗海为例 ,从湖水矿化度、SO2 -4 离子浓度的动态变化和沉积记录的磁化率变化等分析研究 ,评述湖泊酸化的早期表现和判别标志。