A numerical experiment was performed using the Weather Research and Forecasting（WRF） model to analyze the generation and propagation of inertia-gravity waves during an orographic rainstorm that occurred in the Sichu...A numerical experiment was performed using the Weather Research and Forecasting（WRF） model to analyze the generation and propagation of inertia-gravity waves during an orographic rainstorm that occurred in the Sichuan area on 17 August 2014. To examine the spatial and temporal structures of the inertia-gravity waves and identify the wave types, three wavenumber-frequency spectral analysis methods（Fourier analysis, cross-spectral analysis, and wavelet cross-spectrum analysis）were applied. During the storm, inertia-gravity waves appeared at heights of 10-14 km, with periods of 80-100 min and wavelengths of 40-50 km. These waves were generated over a mountain and propagated eastward at an average speed of 15-20 m s^（-1）. Meanwhile, comparison between the reconstructed inertia-gravity waves and accumulated precipitation showed there was a mutual promotion process between them. The Richardson number and Scorer parameter were used to demonstrate that the eastward-moving inertia-gravity waves were trapped in an effective atmospheric ducting zone with favorable reflector and critical level conditions, which were the primary causes of the long lives of the waves. Finally, numerical experiments to test the sensitivity to terrain and diabatic heating were conducted, and the results suggested a cooperative effect of terrain and diabatic heating contributed to the propagation and enhancement of the waves.展开更多
In 2022,the Pakistan witnessed the hottest spring and wettest summer in history.And devastating floods inundated a large portion of Pakistan and caused enormous damages.However,the primary water source and its contrib...In 2022,the Pakistan witnessed the hottest spring and wettest summer in history.And devastating floods inundated a large portion of Pakistan and caused enormous damages.However,the primary water source and its contributions to these unprecedented floods remain unclear.Based on the reservoir inflow measurements,Multi-Source Weighted-Ensemble Precipitation(MSWEP),the fifth generation ECMWF atmospheric reanalysis(ERA5)products,this study quantified the contributions of monsoon precipitation,antecedent snow-melts,and orographic precipitation enhancement to floods in Pakistan.We found that the Indus experienced at least four inflow up-rushes,which was mainly supplied by precipitation and snowmelt;In upper Indus,abnormally high temperature continued to influence the whole summer and lead to large amounts of snowmelts which not only was a key water supply to the flood but also provided favorable soil moisture conditions for the latter precipitation.Before July,the snowmelt has higher contributions than the precipitation to the streamflow of Indus River,with contribution value of more than 60%.Moreover,the snowmelt could still supply 20%-40%water to the lower Indus in July and August;The leading driver of 2022 mega-floods over the southern Pakistan in July and August was dominated by the precipitation,where terrain disturbance induced precipitation account to approximately 33%over the southern Pakistan.The results help to understand the mechanisms of flood formation,and to better predict future flood risks over complex terrain regions.展开更多
为有效开发六盘山地区空中云水资源,提高人工增雨的科学性,需掌握该区域大气水汽的时空分布特征及其原因。利用1989—2018年六盘山地区国家基本站降水观测资料和同期欧洲中期天气预报中心(European Centre for Medium-Range Weather For...为有效开发六盘山地区空中云水资源,提高人工增雨的科学性,需掌握该区域大气水汽的时空分布特征及其原因。利用1989—2018年六盘山地区国家基本站降水观测资料和同期欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代大气再分析资料(ERA5),分析该区域大气可降水量、比湿、相对湿度、水汽通量等大气水汽要素的时空变化,并从水汽输送、地形作用、浮力频率的影响等方面分析六盘山不同地区水汽条件及降水差异的原因。结果表明:一年中绝大多数时间六盘山山顶及东坡大气水汽条件均优于西坡,大值区主要集中在六盘山系主峰附近,并具有明显的季节变化特征。六盘山东坡,受地形抬升作用引起500 hPa辐散、700 hPa辐合的动力场,在夏季最明显,冬季最弱;浮力频率冬季最高,夏季最低;东坡更高的浮力频率及更陡峭的地形,使重力波效应更为明显,具备更有利的垂直上升扩散条件及更大的降水潜力。展开更多
Aerosol particles can serve as cloud condensation nuclei(CCN)to influence orographic clouds.Autoconversion,which describes the initial formation of raindrops from the collision of cloud droplets,is an important proces...Aerosol particles can serve as cloud condensation nuclei(CCN)to influence orographic clouds.Autoconversion,which describes the initial formation of raindrops from the collision of cloud droplets,is an important process for aerosol-cloud-precipitation systems.In this study,seven autoconversion schemes are used to investigate the impact of CCN on orographic warm-phase clouds.As the initial cloud droplet concentration is increased from 100 cm^(-3)to 1000 cm^(-3)(to represent an increase in CCN),the cloud water increases and then the rainwater is suppressed due to a decrease in the autoconversion rate,leading to a spatial shift in surface precipitation.Intercomparison of the results from the autoconversion schemes show that the sensitivity of cloud water,rainwater,and surface precipitation to a change in the concentration of CCN is different from scheme to scheme.In particular,the decrease in orographic precipitation due to increasing CCN is found to range from-87%to-10%depending on the autoconversion scheme.Moreover,the surface precipitation distribution also changes significantly by scheme or CCN concentration,and the increase in the spillover(ratio of precipitation on the leeward side to total precipitation)induced by increased CCN ranges from 10%to 55%under different autoconversion schemes.The simulations suggest that autoconversion parameterization schemes should not be ignored in the interaction of aerosol and orographic cloud.展开更多
本文分别从观测试验分析研究、地形降水物理机制以及地形降水模拟与可预报性研究等方面回顾了近年来对地形降水观测、数值模拟和预报方法方面取得的进展。概括了近些年来开展的若干地形降水观测试验、数值模式的若干线性地形降水方案,...本文分别从观测试验分析研究、地形降水物理机制以及地形降水模拟与可预报性研究等方面回顾了近年来对地形降水观测、数值模拟和预报方法方面取得的进展。概括了近些年来开展的若干地形降水观测试验、数值模式的若干线性地形降水方案,以及模式中次网格地形参数化效应对地形降水预报的影响。回顾了包括地形维度与几何分布、水汽分布及水汽凝结效应、大气稳定性等对地形降水的影响机制,并基于线性地形降水方案,综合考虑了次网格地形阻塞效应和大气降水概率因子,利用GRAPES(Global/Regional Assimilation and Prediction System)模式检验了新简化线性地形降水参数化方案的应用情况。指出对地形降水机理研究和预报技术的改进,需进一步开展多种地形观测试验和多源资料机理分析,研究不同尺度天气系统在多尺度复杂地形下的相互作用,改进数值模式动力、物理精度以及资料同化理论技术,以期提高对地形降水的认识水平和数值模拟能力。展开更多
基金supported by Study on Key Techniques of convective gale monitoring and forecasting in spring in Southern China (GYHY201406002)the National Natural Science Foundation of China (41705027,41775140,41175060,91437215,and 41575047)+1 种基金the research project of Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province (SZKT2016002)Open projects of Plateau Atmosphere and Environment Key Laboratory of Sichuan Province (PAEKL-2015-K2)
文摘A numerical experiment was performed using the Weather Research and Forecasting（WRF） model to analyze the generation and propagation of inertia-gravity waves during an orographic rainstorm that occurred in the Sichuan area on 17 August 2014. To examine the spatial and temporal structures of the inertia-gravity waves and identify the wave types, three wavenumber-frequency spectral analysis methods（Fourier analysis, cross-spectral analysis, and wavelet cross-spectrum analysis）were applied. During the storm, inertia-gravity waves appeared at heights of 10-14 km, with periods of 80-100 min and wavelengths of 40-50 km. These waves were generated over a mountain and propagated eastward at an average speed of 15-20 m s^（-1）. Meanwhile, comparison between the reconstructed inertia-gravity waves and accumulated precipitation showed there was a mutual promotion process between them. The Richardson number and Scorer parameter were used to demonstrate that the eastward-moving inertia-gravity waves were trapped in an effective atmospheric ducting zone with favorable reflector and critical level conditions, which were the primary causes of the long lives of the waves. Finally, numerical experiments to test the sensitivity to terrain and diabatic heating were conducted, and the results suggested a cooperative effect of terrain and diabatic heating contributed to the propagation and enhancement of the waves.
基金the Second Tibet Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0903-02 and 2019QZKK0906)the National Science Foundation of China(42371085).
文摘In 2022,the Pakistan witnessed the hottest spring and wettest summer in history.And devastating floods inundated a large portion of Pakistan and caused enormous damages.However,the primary water source and its contributions to these unprecedented floods remain unclear.Based on the reservoir inflow measurements,Multi-Source Weighted-Ensemble Precipitation(MSWEP),the fifth generation ECMWF atmospheric reanalysis(ERA5)products,this study quantified the contributions of monsoon precipitation,antecedent snow-melts,and orographic precipitation enhancement to floods in Pakistan.We found that the Indus experienced at least four inflow up-rushes,which was mainly supplied by precipitation and snowmelt;In upper Indus,abnormally high temperature continued to influence the whole summer and lead to large amounts of snowmelts which not only was a key water supply to the flood but also provided favorable soil moisture conditions for the latter precipitation.Before July,the snowmelt has higher contributions than the precipitation to the streamflow of Indus River,with contribution value of more than 60%.Moreover,the snowmelt could still supply 20%-40%water to the lower Indus in July and August;The leading driver of 2022 mega-floods over the southern Pakistan in July and August was dominated by the precipitation,where terrain disturbance induced precipitation account to approximately 33%over the southern Pakistan.The results help to understand the mechanisms of flood formation,and to better predict future flood risks over complex terrain regions.
文摘为有效开发六盘山地区空中云水资源,提高人工增雨的科学性,需掌握该区域大气水汽的时空分布特征及其原因。利用1989—2018年六盘山地区国家基本站降水观测资料和同期欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代大气再分析资料(ERA5),分析该区域大气可降水量、比湿、相对湿度、水汽通量等大气水汽要素的时空变化,并从水汽输送、地形作用、浮力频率的影响等方面分析六盘山不同地区水汽条件及降水差异的原因。结果表明:一年中绝大多数时间六盘山山顶及东坡大气水汽条件均优于西坡,大值区主要集中在六盘山系主峰附近,并具有明显的季节变化特征。六盘山东坡,受地形抬升作用引起500 hPa辐散、700 hPa辐合的动力场,在夏季最明显,冬季最弱;浮力频率冬季最高,夏季最低;东坡更高的浮力频率及更陡峭的地形,使重力波效应更为明显,具备更有利的垂直上升扩散条件及更大的降水潜力。
基金sponsored by the National Key Basic Research and Development Program of China (Grant No. 2018YFC1505702)the National Natural Science Foundation of China (Grant No. 41705120, 41590873, 41975138)+1 种基金Weather Modification Ability Construction Project of Northwest China (Grant No. ZQC-R18211)a Guangdong Province Science and Technology Project (Grant No. 2017B020244002)
文摘Aerosol particles can serve as cloud condensation nuclei(CCN)to influence orographic clouds.Autoconversion,which describes the initial formation of raindrops from the collision of cloud droplets,is an important process for aerosol-cloud-precipitation systems.In this study,seven autoconversion schemes are used to investigate the impact of CCN on orographic warm-phase clouds.As the initial cloud droplet concentration is increased from 100 cm^(-3)to 1000 cm^(-3)(to represent an increase in CCN),the cloud water increases and then the rainwater is suppressed due to a decrease in the autoconversion rate,leading to a spatial shift in surface precipitation.Intercomparison of the results from the autoconversion schemes show that the sensitivity of cloud water,rainwater,and surface precipitation to a change in the concentration of CCN is different from scheme to scheme.In particular,the decrease in orographic precipitation due to increasing CCN is found to range from-87%to-10%depending on the autoconversion scheme.Moreover,the surface precipitation distribution also changes significantly by scheme or CCN concentration,and the increase in the spillover(ratio of precipitation on the leeward side to total precipitation)induced by increased CCN ranges from 10%to 55%under different autoconversion schemes.The simulations suggest that autoconversion parameterization schemes should not be ignored in the interaction of aerosol and orographic cloud.
文摘本文分别从观测试验分析研究、地形降水物理机制以及地形降水模拟与可预报性研究等方面回顾了近年来对地形降水观测、数值模拟和预报方法方面取得的进展。概括了近些年来开展的若干地形降水观测试验、数值模式的若干线性地形降水方案,以及模式中次网格地形参数化效应对地形降水预报的影响。回顾了包括地形维度与几何分布、水汽分布及水汽凝结效应、大气稳定性等对地形降水的影响机制,并基于线性地形降水方案,综合考虑了次网格地形阻塞效应和大气降水概率因子,利用GRAPES(Global/Regional Assimilation and Prediction System)模式检验了新简化线性地形降水参数化方案的应用情况。指出对地形降水机理研究和预报技术的改进,需进一步开展多种地形观测试验和多源资料机理分析,研究不同尺度天气系统在多尺度复杂地形下的相互作用,改进数值模式动力、物理精度以及资料同化理论技术,以期提高对地形降水的认识水平和数值模拟能力。
