初夏孟加拉湾低压与云南雨季开始期

通过对46年(1961—2006年)的初夏(4月21日~5月31日)孟加拉湾低压的研究,发现影响云南雨季开始期的初夏孟加拉湾低压系统源地大致位于9°~12°N,88°~91°E之间,较强的低压系统从源地移出后分别沿着两条路径影响云南,这两条路径对应着不同强弱的南亚高压环流。初夏孟加拉湾低压出现频率与云南雨季开始早晚有明显的负相关关系。前期3月中南半岛附近海域的对流强(弱),则有(不)利于初夏孟加拉湾地区产生低压系统。初夏孟加拉湾低压与前期南印度洋海温呈负相关,当南印度洋海温下降(上升)时,有(不)利于孟加拉湾地区对流加强、低压系统生成。     

Understanding the dynamical-microphysical-electrical processes associated with severe thunderstorms over the Beijing metropolitan region

The Dynamical-microphysical-electrical Processes in Severe Thunderstorms and Lightning Hazards(STORM973)project conducted coordinated comprehensive field observations of thunderstorms in the Beijing metropolitan region(BMR)during the warm season from 2014 to 2018.The aim of the project was to understand how dynamical,microphysical and electrical processes interact in severe thunderstorms in the BMR,and how to assimilate lightning data in numerical weather prediction models to improve severe thunderstorm forecasts.The platforms used in the field campaign included the Beijing Lightning Network(BLNET,consisting of 16 stations),2 X-band dual linear polarimetric Doppler radars,and 4 laser raindrop spectrometers.The collaboration also made use of the China Meteorological Administration’s mesoscale meteorological observation network in the Beijing-Tianjin-Hebei region.Although diverse thunderstorm types were documented,it was found that squall lines and multicell storms were the two major categories of severe thunderstorms with frequent lightning activity and extreme rainfall or unexpected local short-duration heavy rainfall resulting in inundations in the central urban area,influenced by the terrain and environmental conditions.The flash density maximums were found in eastern Changping District,central and eastern Shunyi District,and the central urban area of Beijing,suggesting that the urban heat island effect has a crucial role in the intensification of thunderstorms over Beijing.In addition,the flash rate associated with super thunderstorms can reach hundreds of flashes per minute in the central city regions.The super(5%of the total),strong(35%),and weak(60%)thunderstorms contributed about 37%,56%,and 7%to the total flashes in the BMR,respectively.Owing to the close connection between lightning activity and the thermodynamic and microphysical characteristics of the thunderstorms,the lightning flash rate can be used as an indicator of severe weather events,such as hail and short-duration heavy rainfall.Lightning data can also be assimilated into numerical weather prediction models to help improve the forecasting of severe convection and precipitation at the cloud-resolved scale,through adjusting or correcting the thermodynamic and microphysical parameters of the model.     

探讨雷电监测定位数据在人工影响天气中的应用

由于地理位置的原因,一些台站收不到雷达资料,在进行人工影响天气作业时对天气系统的判断存在一定盲目性,与天气雷达比较,雷电定位系统具有覆盖范围大、维持费用低及可连续长时间运行的优点。如果能有效地利用雷电监测数据对人工影响天气作业进行指导,将提高人工影响天气的作业效果。     

河南夏季高温日数的时空分布特征及500 hPa环流型

对河南省40个代表站1961-2005年夏季≥35℃高温日数进行经验正交函数(EOF)展开分析,结果显示,前3个典型场基本能反映河南夏季高温日数分布的主要特征,前3个模态的累积方差贡献率达85%.据此,得出河南夏季≥35℃高温日数的时空分布类型为全省一致型、西北至东南差异型和西南至东北差异型.第一模态对应的时间系数序列的变化幅度最大,第二模态对应的时间系数序列的变化幅度比前一个时间序列要小.第一模态的时间系数演变显示,河南夏季高温日数平均呈减少趋势,且存在2～4 a、8～14 a的周期变化,目前河南夏季高温日数正处于偏多状态中.应用逐日20时500 hPa ECMWF北半球格点资料,对1991-2005年河南典型的大面积持续高温下的环流形势进行普查、分类,分别求各种类型下的环流平均场,从而得到河南省高温的两种环流型,即贝加尔湖高压型和副热带高压型.     

洛阳市城市环境气象监测预报服务研究

利用洛阳市环境监测资料和气象资料,分析了洛阳市污染物浓度的日变化、季节变化、年际变化规律,并分析了污染物浓度与气象因子的关系.在此基础上,通过回归分析预报方法、污染潜势预报方法、CAPPS模式预报方法对洛阳市3种主要污染物的浓度和级别进行了24 h和48 h预测,并建立了气象局与环保部门共享的气象和污染数据库平台,为双方今后的合作奠定了基础.     

边界层特征量在河南省沙尘天气短期预报中的应用

介绍了利用边界层特征量——摩擦速度和梯度Richardson数制作河南省沙尘天气短期预报的方法.结果表明,该动力学方法更能够从本质上反映沙尘天气产生的机制,定性预报准确率为62.5%.     

HRCLDAS-V1.0和ERA5海面风场对比评估分析

基于2020年中国近海31个浮标的逐小时数据,使用统计分析方法对中国气象局高分辨率陆面数据同化系统(HRCLDAS-V1.0)和欧洲中期天气预报中心第5代全球大气再分析数据(ERA5)海面风场进行了系统的检验,检验结果表明：两者在我国近海均具有较高的可信度,风速平均绝对误差(MAE)分别为1.16 m/s和1.09 m/s,风向MAE分别为23°和22°。随着风力增大两者的风速准确度均有所降低,当风力等级≥10级时,前者准确度优于后者;对于风向而言,随着风力增大,两者准确度均升高。此外,选取2020年典型的两次冷空气过程和2008号台风“巴威”过程,检验两者在不同天气过程影响下的准确度,两类融合产品均能较好地再现冷空气过程引起的风向变化,而对不同强度的冷空气过程下的风速反映存在差异;对于台风引起的大风,在风速较低时两者风速均具有不错的表现,但HRCLDAS-V1.0对峰值强度的表现优于ERA5。     

Polar stratospheric clouds from satellite observational data

The spectral aerosol-extinction coefficients (SAECs) obtained from SAGE III measurements are used to study the physical and integral microphysical characteristics of polar stratospheric clouds (PSCs). Different criteria for PSC identification from SAEC measurements are considered and analyzed based on model and field measurements. An intercomparison of them is performed, and the agreement and difference of the results obtained with the use of different criteria are shown. A new criterion is proposed for PSC identification, which is based on the estimate of how close the measured vector of the spectral attenuation coefficient is to a model distribution of the PSC ensemble. On the basis of different criteria, cases of PSCs are isolated from all SAGE III observations (over 30000). All selection criteria lead to a qualitatively and quantitatively similar space-time distribution of the regions of PSC localization. The PSCs observed in the region accessible to SAGE III measurements are localized in the latitudinal zones 65°–80° in the Northern Hemisphere and 45°–60° in the Southern Hemisphere during the winter-spring period. In the Northern Hemisphere, PSCs are observed within the longitudinal zone 120° W–100° E with the maximum frequency of PSC observation in the vicinity of the Greenwich meridian. In the Southern Hemisphere, the region of PSC observation is almost the same in longitude but with a certain shift in the maximum frequency of PSC observation to the west. This maximum is observed in the vicinity of 40°W, and the region of usual PSC observation is the neighborhood of 60° of the maximum’s longitude. The physical parameters of PSCs are estimated: the mean heights of the lower and upper boundaries of PSCs are 19.5 and 21.9 km, respectively, and the mean cloud temperature is 191.8 K. The integral microphysical parameters of PSCs are estimated: the total surface of NAT particles S _NAT = 0.41 μm²/cm³; the total volume of NAT particles V _NAT = 1.1 μm³/cm³; and, for all aerosol and cloud particles together, S is 2.9 ± 1.5 at a standard deviation of 2.7 μm²/cm³ and V is 2.8 ± 1.5 at a standard deviation of 4.2 μm³/cm³. A high frequency of PSC occurrence and high values of S and V in PSCs both for all particles and for NAT particles have been noted in January–February 2005 as compared to the rest of the period of SAGE III measurements for 2002–2005.     

Negative correlations of variations in near-water wind and surface wind waves

The relationship between the intensity of surface wind waves and near-water wind is analyzed. The data of measuring wind waves and near-water wind under natural conditions in the Black Sea (July 2004) and Norwegian Sea (June 2003, 16th cruise of the R/V Akademik Sergei Vavilov) are used. A phenomenon of negative correlations has been found between the intensity of wind waves and near-water wind in regions of substantial restructuring of wind waves in the field of inhomogeneous flows: wind-wave amplification during wind decay and vice versa. Examples of such observations are presented, a theoretical model is constructed for the observed phenomenon, and a good agreement is obtained between theory and experiment.     

Variations in the concentration of mesospheric ozone during the total solar eclipse of March 29, 2006, from microwave radiometric data

We present the results of microwave observations of the ozone content variability in the upper stratosphere and lower mesosphere during a total solar eclipse of March 29, 2006 at the Kislovodsk high-altitude scientific station. An increase in the concentration of mesospheric ozone was recorded during the eclipse. At a height of 60 km, the ozone concentration increased by 40%, which is close to the value of diurnal ozone variations.