A STUDY ON TYPHOON MOVEMENT PART Ⅰ:THE EFFECT OF DIABATIC HEATING AND HORIZONTAL TEMPERATURE DISTRIBUTION

A basic equation governing the movement of a typhoon has been derived based on the system of primitive equations of motion in the atmosphere. The role of several forcing factors which cause the deviation of the typhoon from the steering current have been discussed based on the governing equation. What is presented in Part Ⅰ is a theoretical analysis on the effects of diabatic heating and the horizontal temperature distribution. It is shown that the accelerations of a typhoon caused by diabatic heating and temperature advection coincide with the direction of the volume-averaged "diabatic steering velocity" QV and the "steering velocity of temperature advection" A_TV (V is the air velocity,Q the diabatic heating rate and A_T the temperature advection ), respectively. The precipitation (or condensation heating) on the right (left) side of a typhoon will accelerate (decelerate) the typhoon. The precipitation in the front (rear ) of the typhoon will turn it to the left (right) of its ordainal path. A typhoon will speed up (slow down) when it moves towards a region of cold (warm) air.     

PROBLEMS EXISTING IN THE VERTICAL DISCRETIZATION OF THE HYDROSTATIC EQUATION AND IMPROVEMENT TESTS

Through analysis and numerical computation of ECMWF's discrete scheme of hydrostatic equation(Baede et al.1979),it has been found that in the case of equal △σ there exist systematic errors in the scheme.The error E_Φ caused by taking the arithmetic mean of the geopotential heights of two adjacent half σ-levels as the geopotential height of the corresponding integer σ-level,increases with height and has an unacceptable maximum in the vicinity of the top of the atmosphere;however,the errors caused by the temperature treatment are generally small.On the other hand,if an uneven △σ-scheme in which the levels in the upper and lower atmosphere are denser than those in the middle atmosphere,is adopted,then E_Φ can be much reduced.However,if the resolution of the original equal Art-scheme doubles,then E_Φ can only be found to be much reduced in the troposphere and that in the vicinity of the atmospheric top is still unacceptable.Two numerical schemes for improvement have been presented. Of them one is the same as the ECMWF's scheme,but with equal △lnσ,and the other is to integrate the equation by the use of Tschebyscheff polynomials T_n and to adopt the zeros of T_N as the atmospheric levels where N is the total number of levels.The results show that with both schemes the computational errors can be much reduced,especially the latter,due to the fact that the errors of three statistical types are generally less than the root mean square error of the geopotential heights reported in TEMP.     

A STUDY ON DEFORMATIONS OF RAY AND ITS RELEVANT FACTORS*

In this paper,the effects of first and second meridional derivative(i.e.h_s^u,d²f/dy²,u″)of the Coriolis parameter,Westerly profile and topography structure on ray routes are qualitatively analysed by use of a simplified mathematical model.The analysis indicates that the second derivatives of the above relevant factors play an important role in the formation of great circle route.A profile of west wind similar to the real atmosphere may result in a "sine wave pattern" of ray.The effects of west wind shear,β factor and the slope of topography on the scale of radius of great circle,critical latitude of rays ard the amplitude of wave train of teleconnection are also discussed.Additionally,the characters of critical velocity profile for meridionally trapped wave are mentioned.     

2021年2月黄河中下游两次暴雪的相态转换特征及成因

利用常规高空资料、地面加密自动站、双偏振多普勒天气雷达、微波辐射计与ERA5再分析数据等多源资料,分析了2021年2月下旬黄河中下游两次暴雪过程的相态演变及形成机理。结果表明:两次过程的大尺度影响系统基本一致,只是影响系统的强度和位置不同导致两次过程存在些许差异。两次过程均存在相态转换,过程Ⅰ中存在相态逆转(由雨转雪再转雨),而过程Ⅱ中只存在雨转雪的转换。在太行山以西的山区,当地面2 m气温低于0.5 ℃时,降水相态以雪为主,在0.5~1 ℃之间时,多为雪或雨夹雪并存;在平原地区,当2 m气温为1~2 ℃时,降水相态为雨或雨夹雪,在0~1 ℃之间时,则为雪与雨夹雪并存,低于0 ℃时,降水相态为雪。在降雨阶段,双偏振雷达产品相关系数(CC)值约在0.98以下,差分反射率(Z_DR)在0.6 dB以上,差分传播相移率(K_DP)值约在0.2 (°)·km^-1以上;在降雪阶段,CC值在0.98~0.99之间,Z_DR值在0.2~0.8 dB之间,K_DP 值约在0.2 (°)·km^-1以下;但在降水相态由雨转雨夹雪时,Z_DR、CC与K_DP 值没有明显变化。     

Taylor定理余项中θ的渐近性和拓广

给出带有m-1项断裂项n+m阶Taylor定理余项中θ的渐近估计,其估计式为 .利用该估计式将Taylor定理推广为 ,其中余项 .最后举例说明该推广在近似计算中的优越性。     

利用雷达作台风0～3h雨量等级预报

通过对1989～1992年台风影响浙江期间,杭州数字化雷达回波及对应的地面58个气象站和156个水文站自记1h雨量资料,进行了统计分析,得到在浙江仅有台风单一系统引起降水时,杭州数字化雷达回波强度Z与雨强I.根据Z=A·I^b关系得出A、b系数在不同探测范围的值,以得到Z与I关系,并结合雷达回波的移动情况,制作了浙江省台风0～3h雨量等级预报。     

铜川春季气候特征分析

利用铜川３站１９６４—２０１０年春季气温、降水、风、日照等观测资料,采用统计方法分析
铜川春季气候变化规律,结果表明：铜川春季平均气温为１１.６℃,平均气温年际变化呈现增暖趋
势,气候倾向率为０.３７４℃/１０ａ,北部增暖显著,南部次之,中部最小;北部出现≤－２.０℃和
≤－４.０℃的概率较大,中部次之,南部最小;≤－２.０℃出现频率为３.４％～１２.４％,≤－４.０℃出现频率为１.１％～５.９％;平均降水量为１１５.９ｍｍ,由北向南递减,降水随年际变化呈减少趋
势,下降最显著的是４月;日照百分率３、５月最小,４月最大,平均总辐射量自北向南递减;地
形原因导致风分布不均匀,平均风速北部最大,南部次之,中部最小,呈现４月明显偏大,３、５
月基本接近的月际变化规律;一日内风速通常夜间较小,午后较大,春季大风一般伴有寒潮,降
温天气;全市大风分布差异很大,北部宜君占５３.４％,４月最多,占４２.８％。

     

二阶奇异动力系统的非平凡周期解

应用Leray-Schauder非线性二择一原理研究二阶动力系统x+k²x=f(t,x)+e(t)非平凡周期解的存在性,其中0<k<π/T,f∈C((R/TZ)×R^N\{0},R^N)在原点具有排斥的奇性.不需要任何的强制性条件,既可以处理强奇性,也可以处理弱奇性.     

Relationship between Net Radiation and Broadband Solar Radiation in the Tibetan Plateau

The characteristics of net radiation (R_n)(0.3--10 μm) in Lhasa and Haibei in the Tibetan Plateau were analyzed based on long-term in-situ measurements of surface radiation data. The monthly average of daily R_n reached a minimum during the winter period followed by an increase until May and then a decline until January. This variation is consistent with solar activity. The annual mean daily total R_n values were 0.92 MJ m^-2 d^-1 and 0.66 MJ m^-2d^-1 in Lhasa and Haibei, respectively. A relationship between R_n and broadband solar radiation (R_s) was demonstrated by a good linear correlation at the two sites. R_n can be an accurate estimate from R_s. The estimated R_n values were similar to the observed values, and the relative deviations between the estimates and measurements of R_n were 2.8% and 3.8% in Lhasa and Haibei, respectively. The application of the R_n estimating model to other locations showed that it could provide acceptable estimated R_n values from the R_s data. Furthermore, we analyzed the influence of clouds on R_n by different clear index (K_s), defined as the ratio of R_s to the extraterrestrial solar irradiance on a horizontal surface. The results indicate that more accurate results are associated with increased cloudy conditions. The influence of the albedo was also considered, but its inclusion in the model resulted in only a slight improvement. Because surface albedo is not usually measured, an expression based solely on global solar radiation could be of more extensive use.     

A Quality Assurance Procedure and Evaluation of Rainfall Estimates for C-Band Polarimetric Radar

A mobile C-band dual polarimetric weather radar J type (PCDJ), which adopts simultaneous transmission and simultaneous reception (STSR) of horizontally and vertically polarized signals, was first developed in China in 2008. It was deployed in the radar observation plan in the South China Heavy Rainfall Experiment (SCHeREX) in the summer of 2008 and 2009, as well as in Tropical Western Pacific Ocean Observation Experiments and Research on the Predictability of High Impact Weather Events from 2008 to 2010 in China (TWPOR). Using the observation data collected in these experiments, the radar systematic error and its sources were analyzed in depth. Meanwhile an algorithm that can smooth differential propagation phase (Ф_DP) for estimating the high-resolution specific differential phase (K_DP) was developed. After attenuation correction of reflectivity in horizontal polarization (Z_H) and differential reflectivity (Z_DR) of PCDJ radar by means of K_DP, the data quality was improved significantly. Using quality-controlled radar data, quantitative rainfall estimation was performed, and the resutls were compared with rain-gauge measurements. A synthetic Z_H/K_DP-based method was analyzed. The results suggest that the synthetic method has the advantage over the traditional Z_H-based method when the rain rate is >5 mm h^-1. The more intensive the rain rates, the higher accuracy of the estimation.     

暴雨发生前AIRS卫星资料适用性检验研究

利用AIRS卫星产品中的气温和水汽资料,计算出K指数(I_K)和沙氏指数(I_S)这两种大气不稳定指数。对暴雨发生前6 h左右这两种大气不稳定指数进行统计分析。统计结果表明:在暴雨发生前6 h左右,80%左右的暴雨发生在I_K >27.5℃或I_S <3℃的情况下。由于I_K的分布与暴雨发生的频率基本呈现出较为明显的递增变化,因此I_K与I_S相比能更好地反映暴雨天气的发生。为了更好地描述暴雨发生前的大气不稳定特征,将AIRS计算的I_K和I_S做了适当的结合,得到KS指数(I_KS)并将其运用到一次暴雨个例进行验证,从验证效果来看:暴雨发生的区域在6 h前基本都处在了I_KS较高的情况下,I_KS对暴雨具有一定的指示意义。通过对暴雨区域像元中AIRS反演的气温和水汽误差分析中可以得出:AIRS计算的I_K和I_S误差主要由AIRS在有效云量较高时850hPa高度上反演的气温以及700hPa和850hPa高度上反演的水汽的误差导致的。     

利用LAP-3000型风廓线雷达资料对深圳地区湍流耗散率特征的研究

利用2010年1-2月深圳LAP3000型风廓线雷达资料, 对湍流耗散率进行了估算, 针对典型晴天条件下的湍流耗散率ε、折射率结构常数C₂ⁿ、水平风速和风切变, 分析了其时空变化特征。得出如下结论: (1) 深圳地区低空大气ε的量级在10^-7~10^-1 m^-2·s^-3之间, 与理论模拟值基本一致; (2) 时间分布特征为, 2 km以下ε有很明显的日变化特征, 夜晚和上午ε较大, 下午及傍晚减少;(3) 空间分布特征表现为, ε随高度大致呈递减分布;ε量级达10^-2.5 m²·s^-3所在高度可作为深圳地区2010年1月14-15日边界层顶高度的判断依据。     

东亚地区二氧化碳体积分数变化特征

利用2004年以来东亚地区10个本底观测站大气φ(CO₂)观测资料,分析了各站大气φ(CO₂)的变化特征及其各站之间的差异,讨论了下垫面特征、源汇作用等对φ(CO₂)变化的影响.结果表明:10个本底站大气月均φ(CO₂)有明显的季节变化,高值多出现在冬春等寒冷季节,而低值则多出现在6—9月,属于北半球的夏季;大气φ(CO₂)日变化趋势较为一致,15时(当地时间)前后达到全天最低,随后φ(CO₂)升高,并在日落后继续积累,至清晨7时(当地时间)前后达到全天最高,之后φ(CO₂)随着太阳辐射的增强而逐渐降低,且平均φ(CO₂)水平与下垫面植被量成反比,φ(CO₂)日变化的幅度与下垫面植被量成反比.作为全球基准站之一的瓦里关山站,2004—2008年φ(CO₂)年均值逐年增加,年增长率为2.28×10^-6/a.     

一类非线性Volterra积分不等式

本文简要讨论Gronwall不等式的研究进展,并给出关于如下的一类非线性Volterra积分不等式的一个结果：w(u(t))≤g(t))+∑_i=1ⁿ∫_αi(t0)^α_i(t)f_i(t,s)∏_j=1^mH_ij(u(s))G_ij(max_s-h≤ξ≤s u (ξ))ds.     

非地转湿Q矢量的改进及其应用

在完全考虑非绝热加热项作用的前提下,从原始方程出发,推导出改进后的非地转湿Q矢量(Q^q),以及用其散度作强迫项的ω方程,将其应用于一次梅雨锋暴雨诊断分析,结果表明:改进后的非地转湿Q矢量对同时刻地面降水的反映能力较岳彩军改进的湿Q矢量(Q^M)、原非地转湿Q矢量(Q^*)、非地转Q矢量(Q#)有显著的提高;在整个梅雨锋暴雨过程中,500hPa高度上的Q^q矢量散度辐合场的辐合强度及其辐合中心位置对同时刻的降水强度及雨区位置有非常好的指示作用;Q^q矢量的垂直分布揭示了次级环流的方向和强弱,暴雨位于次级环流的上升支附近。     

福建三明市春季PM2.5中有机碳、元素碳和水溶性离子特征分析

2014年3月13日至4月20日在福建三明市利用PM_2.5中流量采样器采集大气中PM_2.5膜样品,测定了PM_2.5的质量浓度,并用热/光碳分析仪和离子色谱分析了其组分变化特征.结果表明,三明市观测期间PM_2.5的平均质量浓度为73.61±0.73 μg/m³,有机碳(OC)和元素碳(EC)的平均质量浓度分别为7.26±1.00和5.63±0.27 μg/m³,水溶性离子中SO₄^2-、NH₄⁺、NO₃^-和Na⁺的质量浓度分别为18.08±12.19、4.18±3.56、2.77±1.16和2.73±0.23 μg/m³,总和占总水溶性离子的87.76%.结合后向轨迹分析了福建三明市的污染物来源特征.该地区OC/EC的平均比值小于2,SOC(二次有机碳)生成量很少,主要以一次有机污染物为主,OC、EC与K⁺的相关性分析表明OC、EC与K⁺的来源相近,可以判断OC、EC绝大部分来源是生物质燃烧产生的污染物.在水溶性离子分析中,观测期间NO₃^-/SO₄^2-为0.159±0.02,表明三明市主要以固定源为主,机动车辆等移动源贡献较少.     

用常规探空资料估算Cn2和ε垂直变化初探

用南京、射阳的常规探空资料建立了估算折射率结构常数C_n²和湍能耗散率ε垂直变化理论模式。结果表明:用该理论模式计算的ε值与用天气脉冲多普勒雷达探测的速度谱宽σ_r²再估算得到的ε值有较好的一致性。     

锋生切变型强对流概念模型在浙江中西部“3·21”过程中的应用探究

利用ECMWF 0.25°×0.25°再分析资料,对照浙中西的强对流概念模型,对2019年3月21日发生在浙江中西部地区(简称"浙中西")的一次雷暴大风为主的强对流过程(简称"3·21"过程)进行诊断分析、经验总结。结果表明:该过程符合浙中西锋生切变型的强对流概念模型,出现该过程的环境条件是700 hPa西南急流脉动、850 hPa偏北和偏南两支气流强烈发展、地面低压倒槽和低层湿舌增强;探空曲线表现为上干下湿,对流层中层有明显的干侵入,大风指数I_w、对流有效位能 (Convective Available Potential Energy, CAPE)和500 hPa以下垂直风切变异常偏强形成动力强迫;对比不同强对流天气有不同的预报着眼点,设定阈值或可提高预报警报效率,如雷暴大风天气大风指数I_w > 18.5 m·s^-1、CAPE> 1 700 J·kg^-1、500 hPa的相对湿度小于46 %,冰雹天气则0 ℃层、-20 ℃层高度低于4.6 km和7.6 km且850 hPa与500 hPa气层温差高于26 ℃等,深刻理解该类强对流概念模型,是做好此类致灾性强对流潜势预报的关键点。     

基于融合资料的天津短时强降水环境物理量可信度及特征分析

针对2009—2017年6～9月天津地区140次短时强降水天气过程,将NCEP FNL(1°×1°)全球分析资料与地面气象观测数据融合,计算天津地区短时强降水的融合物理量参数,通过偏差和偏差区间占有率等分析融合物理量的可信度,并在大量样本统计基础上给出不同月份的短时强降水环境参量特征和指标。结果表明：(1)基于NCEP FNL分析资料与地面气象观测数据的融合物理量在短时强降水潜势判断中具有较高的可信度,融合CAPE、LI、LCL平均绝对误差分别为260.7J.kg_^-1、0.9℃、14hPa,与融合前的NCEP FNL物理量相比绝对误差分别降低了58.1%、48.0%、49.0%。(2)不同月份短时强降水发生所必需的水汽、热力和能量等环境条件差异显著,TPW、K、LI、CAPE、LCL和Z₀均呈现明显的月变化特征。(3)若以75%短时强降水发生的环境条件作为预报指标,7～8月TPW、K、CAPE、Z₀、LCL物理量阈值极为相近,短时强降水多发生在TPW>45kg.m_^-2、K>32℃、CAPE>835J.kg_^-1、LCL>882 hPa、Z₀>4300m条件下,6月物理量指标要求明显降低,如TPW>34kg.m_^-2、K>30℃、CAPE>353J.kg_^-1、LCL>880 hPa、Z₀>3900m,9月预报指标要求则最低。     

QINGHAI-XIZANG SURFACE LONG-WAVE RADIATION PARAMETERIZATION WITH ITS CLIMATIC CALCULATION*

In the context of August 1982- July 1983 radiation balance data of the Qinghai-Xizang Plateau, detailed study is made of the relation between the active-surface temperature and surface temperature, proposing two parameterization schemes on surface long-wave radiation(SLWR)of the form U=kδσ(T₀+273)⁴ and U=δσ[(T₀+273)⁴+△T)]⁴, where k and △T are indicated by parameterization equations, separately, others being in conventional notation. Retrieved verification shows the two formulae to be of the same fitting accuracy with the mean relative error of 3.6% and suitable for computing instantaneous and mean flux density, alongside analyzed daily and annual variations of k and △T. Eventually. SLWR in the target area is investigated and its climatic characteristics examined.