Simulation of summer precipitation diurnal cycles over the Tibetan Plateau at the gray-zone grid spacing for cumulus parameterization

Climate Dynamics - The Tibetan Plateau (TP) is often referred to as the “water tower of Asia” or the “Third Pole”. It remains a challenge for most global and regional models...     

A new DRP-4DVar-based coupled data assimilation system for decadal predictions using a fast online localization technique

Climate Dynamics - A new coupled data assimilation (CDA) system based on dimension-reduced projection four-dimensional variational data assimilation (DRP-4DVar) for decadal predictions is developed...     

2017年8月13日东洞庭湖水龙卷特征

利用常规观测资料、自动气象站资料及湖南省岳阳多普勒天气雷达资料对2017年8月13日东洞庭湖水龙卷（简称扁山水龙卷）进行分析。结果表明：高空辐散、中低空低压切变、边界层气旋式辐合与特殊环境共同形成强烈辐合上升流场,3个相继北上的γ中尺度低涡中第2个低涡在上升流场和前后低涡共同作用下,在扁山水域迅速加强形成水龙卷,扁山湖心自动气象站风向风速、气压、能见度等变化较为显著,但仅伴随0.2 mm阵性降水。雷达产品显示：扁山水域强辐合带北部强降水质心低、强风切变低、切变上空水平径向风速小,但整条辐合带无风暴跟踪信息、中气旋和龙卷式涡旋特征;风廓线显示扁山水龙卷形成时边界层0.6 km中气旋与0.3 km近地面辐合流场上下叠加。通过与安徽升金湖水龙卷以及洞庭湖区历史上多次龙卷进行比较,认为低空强烈气旋式辐合流场对水龙卷生消有重要作用,高空大范围辐散与中低空、边界层、地面辐合垂直叠加产生的强烈抬升抽吸作用则是扁山水龙卷的主要成因。     

亚欧500hPa旬平均形势预报的改进及检验

利用数值预报产品，对原亚欧５００ｈＰａ旬平均形势预报方程作了改进。除对空间和时间尺度上作了改进外，在预报因子的选择上，由亚欧地区的单点相关，扩张至整个北半球的相关；并根据长波天气系统的气候地理分布和遥相关分析等方法，选择关键区作为候选因子，组建了新的形势预报方程。经检验比较，新的形势预报方程高度距平正确和长波系统位置正确率分别提高了０．１５－０．２０和０．１０。     

Microwave Simulations of Precipitation Distribution with Two Radiative Transfer Models

Two microwave radiative transfer models of precipitating cloud are used to simulate the microwave upwelling radiances emerging from precipitating clouds. Comparison of the simulation results shows that significant difference of microwave upwelling radiances exists between these two radiative transfer models. Analysis of these differences in different cloud and precipitation conditions shows that it is complicated but has certain trend for different microwave frequencies. The results may be useful to quantitative rainfall rate retrieval of real precipitating clouds.     

The impact of high altitude aircraft on the ozone layer in the stratosphere

The paper discusses the potential effects on the ozone layer of gases released by the engines of proposed high altitude supersonic aircraft. The major problem arises from the emissions of nitrogen oxides which have the potential to destroy significant quantities of ozone in the stratosphere. The magnitude of the perturbation is highly dependent on the cruise altitude of the aircraft. Furthermore, the depletion of ozone is substantially reduced when heterogeneous conversion of nitrogen oxides into nitric acid on sulfate aerosol particles is taken into account in the calculation. The sensitivity of the aerosol load on stratospheric ozone is investigated. First, the model indicates that the aerosol load induced by the SO₂ released by aircraft is increased by about 10–20% above the background aerosols at mid-high latitude of the Northern Hemisphere at 15 km for the NASA emission scenario A (the NASA emission scenarios are explained in Tables I to III). This increase in aerosol has small effects on stratospheric ozone. Second, when the aerosol load is increased following a volcanic eruption similar to the eruption of El Chichon (Mexico, April 1982), the ozone column in spring increases by as much as 9% in response to the injection of NO _x from the aircraft with the NASA emission scenario A. Finally, the modeled suggests that significant ozone depletion could result from the formation of additional polar stratospheric clouds produced by the injection of H₂O and HNO₃ by the aircraft engines.     

FY-3E: The First Operational Meteorological Satellite Mission in an Early Morning Orbit

Fengyun-3 E(FY-3E),the world’s first early-morning-orbit meteorological satellite for civil use,was launched successfully at the Jiuquan Satellite Launch Center on 5 July 2021.The FY-3E satellite will fill the vacancy of the global early-morning-orbit satellite observation,working together with the FY-3C and FY-3D satellites to achieve the data coverage of early morning,morning,and afternoon orbits.The combination of these three satellites will provide global data coverage for numerical weather prediction(NWP)at 6-hour intervals,effectively improving the accuracy and time efficiency of global NWP,which is of great significance to perfect the global earth observing system.In this article,the background and meteorological requirements for the early-morning-orbit satellite are reviewed,and the specifications of the FY-3E satellite,as well as the characteristics of the onboard instrumentation for earth observations,are also introduced.In addition,the ground segment and the retrieved geophysical products are also presented.It is believed that the NWP communities will significantly benefit from an optimal temporal distribution of observations provided by the early morning,mid-morning,and afternoon satellite missions.Further benefits are expected in numerous applications such as the monitoring of severe weather/climate events,the development of improved sampling designs of the diurnal cycle for accurate climate data records,more efficient monitoring of air quality by thermal infrared remote sensing,and the quasicontinuous monitoring of the sun for space weather and climate.     

Quantifying the Spatial Characteristics of the Moisture Transport Affecting Precipitation Seasonality and Recycling Variability in Central Asia

Moisture contribution and transport pathways for Central Asia(CA)are quantitatively examined using the Lagrangian water cycle model based on reanalysis and observational data to explain the precipitation seasonality and the moisture transport variation during 1979-2015.Westerly-related(northwesterly and westerly)transport explains 42%of CA precipitation and dominates in southwest CA,where precipitation is greatest in the cold season.Southeast CA,including part of Northwest China,experiences its maximum precipitation in the warm season and is solely dominated by southerly transport,which explains about 48%of CA precipitation.The remaining 10%of CA precipitation is explained by northerly transport,which steadily impacts north CA and causes a maximum in precipitation in the warm season.Most CA areas are exposed to seasonally varying moisture transport,except for southeast and north CA,which are impacted by southerly and northerly transport year-round.In general,the midlatitude westerlies-driven transport and the Indian monsoon-driven southerly-related transport explain most of the spatial differences in precipitation seasonality over CA.Moreover,the contribution ratio of local evaporation in CA to precipitation exhibits significant interdecadal variability and a meridionally oriented tripole of moisture transport anomalies.Since the early 2000s,CA has experienced a decade of anomalously low local moisture contribution,which seems jointly determined by the weakened moisture contribution from midlatitudes(the Atlantic,Europe,and CA itself)and the enhanced contribution from high latitudes(West Siberia and the Arctic)and tropical areas(South Asia and the Indian Ocean).     

加热场的三维结构对亚洲夏季风环流的影响

本文利用原始方程线性波模式考察了加热场的三维结构对夏季定常行星波特性的影响;比较了不同加热方式对亚洲夏季风坏流的形成及维持所起的作用。指出与低纬深厚积云对流相联的凝结加热对亚洲夏季风环流所起的重要作用和大气定常行星波响应对加热场的垂直结构的敏感性。