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1.
热带大气和海洋的半地转适应和发展运动 总被引：5，自引：2，他引：3
半地转适应和半地转发展是热带大气和海洋运动的两种基本形态,它们在时间上是可分的,反映了不同的物理过程。当初始扰动作用于大气或海洋时,首先将激发出重力惯性波,当重力惯性波频散后,建立起半地转的平衡状态,此后运动进入到以Rossby波（长波或短波）、Kelvin波和混合波中的Rossby短波为主导的发展状态。文中研究的纬圈半地转适应和发展运动,是Gill长波近似模式的理论基础。同时研究了经圈半地转适应和发展运动,实际上这相当于短波近似模式,它可以应用到研究海洋经圈边界附近的一类问题。 相似文献
2.
低纬大气滤波模式研究 总被引：2，自引：0，他引：2
本文从描写低纬大气运动的方程组出发,采用半地转模式和准地转模式对低纬快速波动进行了滤除,这些模式仅含低频的Rossby波。分析指出:低纬半地转模式可以滤去高频波动,但得到的是波数k→0的Rossby波;而低纬准地转模式不但可以滤去高频波动,而且得到的是不受歪曲的Rossby波。 在滤波的基础上,本文分析了由Rossby波引起的低频振荡周期。 相似文献
3.
热带大气半地转适应理论的尺度分析和物理机制 总被引：1，自引：1，他引：1
对热带大气行星尺度运动所做的尺度分析和物理分析表明:热带大气 的行星尺度运动在y方向容易实现气压梯度力与Coriolis力的平衡，它称为纬圈的 半地转运动。半地转平衡的建立过程，也就是半地转适应过程相对是很短暂的，它不需 要考虑f=β0y随y的变化，因而主要依靠惯性重力波为频散；而半地转平 衡建立后的演变过程相对是很缓慢的，它主要受Kelvin波和Rossby波控制。 相似文献
4.
基本流场切变对赤道长Rossby波的影响 总被引：9，自引：2，他引：9
文中应用赤道β平面近似 ,建立一个简单的斜压大气半地转模式 ,在热力学方程中引入表征基本位温场 (θ)经向分布特征的无量纲参数 σ,对线性化的扰动方程进行了频率分析 ,研究基本位温场经向非均匀分布以及基本气流垂直切变对赤道纬向超长尺度 Rossby波动的影响 ,并指出仅考虑基本气流垂直切变或者基本位温场变化的作用是不合适的。定性分析结果表明 :基本位温场经向温差必然有基本气流垂直切变与其相匹配 ,而基本气流垂直切变将导致赤道长 Rossby波动不稳定并影响其纬向传播速度 相似文献
5.
热带地转适应运动的动力学基础 总被引：3，自引：1，他引：2
文中讨论了热带斜压大气地转适应过程中的若干动力学约束关系 ,在不考虑行星位势涡度梯度的前提下给出了三维重力惯性波的频散方程、位势涡度时间不变式。在这基础上指出由于 Taylor- Proudman定理成立 ,运动将趋于水平化。同时指出 ,在热带纬圈半地转平衡更易出现。地转适应后的运动 ,一般是水平无辐散的 ,虽然垂直运动趋于零 ,但物理场随高度仍然有变化 ,即是层结的。 相似文献
6.
利用斜压两层模式研究了赤道平面近似下的低纬热带大气适应过程。指出低纬斜压大气适应过程主要受重力惯性内波控制。通过重力惯性内波对初始非地转能量的频散，使纬向运动达到地转平衡，而经向维持非地转运动，正压模式下称为半地转平衡，斜压模式下称为半热成风平衡。通过对垂直运动方程的求解，可知，垂直运动只与重力惯性内波相联系，其产生与初始斜压位涡度无关，而只与初始时刻的垂直运动和垂直运动倾向有关，半地转适应使运动趋向水平运动。讨论了半热成风平衡的建立及其物理机制，指出由于重力惯性内波激发出垂直运动，与垂直运动相联系的水平辐合辐散调整流场和温度场之间的关系，使温压场最终达到半热成风平衡。通过对适应过程终态的分析，指出平均温度场和切变流场之间的适应方向决定于初始非半地转扰动的尺度与斜压Ｒｏｓｓｂｙ变形半径有关的特征尺度的比值，当比值大于１时，切变流场向平均温度场适应；当比值小于１时，平均温度场向切变流场适应 相似文献
7.
纬向气流对地形Rossby波的影响 总被引：2，自引：0，他引：2
本文在半地转近似下,采用相平面方法讨论了纬向基本气流对线性和非线性地形Rossby波的稳定性及解的性质的影响。结果指出:线性和非线性稳定性判据形式一样,纬向气流及其切变对稳定性有明显影响;在非线性近似下,可形成孤立波槽和孤立波脊。 相似文献
8.
文章采用准地转带耗散因子的大气和海洋的动量、热力学方程,建立了一个简单的描写大尺度运动的准地转海气耦台浅水模式,分别在中高纬和低纬地区讨论了海气的耦合效应,分析了耦合低频模(海洋模)的振荡周期随耦合频率和经向波数的变化转征,并由此而说明低频振荡与海气相互作用有关。然后从海洋和大气的频散曲线中揭示出耦合强度对Rossby波传播的影响,还从缓变波列的观点,讨论了两种模之间的转换机制。 结果表明:Newton冷却Rayleigh摩擦对海洋Rossby波起稳定作用。随着耦合频率的增加,耦合低频模的周期也相应增加;经向波数越大,这种增加就越迅速。当耦合频率趋近于临界值时,海洋Rossby波趋于静止。当海气耦合强度增加到一定程度时,海洋Rossby波的传播方向变成与原来相反。通过海气相互作用,海洋Rossby波的一部分将转换成大气Rossby波,本文求解了其能量转换系数。 相似文献
9.
切变基流对赤道大气波动稳定性的作用 总被引：3，自引：2，他引：3
在赤道β平面近似条件下，使用纬向切变基流下线性化Boussinesq方程组，分析了在纬向切变基流下几种赤道大气波动的稳定性特征。研究结果表明，基本气流的水平切变对赤道大气波动起到不稳定的作用，但是对赤道大气Kelvin波的频率、稳定性以及传播的相速度并不起作用。基本气流的水平切变使得相对于基本气流向东传播的重力惯性内波相速度减慢，而使得相对于基本气流向西传播的重力惯性内波的相速度加快，却造成相对于基本气流向西传播的Rossby波相速度减慢。基本气流的水平切变对于对赤道混合Rossby-重力惯性内波的影响主要取决于纬向波数k值的范围大小。当纬向波数k值较小时，基流的水平切变使得相对于基本气流向西传播的混合Rossby-重力惯性内波相速度加快；而当纬向波数k值较大时，则使得相对于基本气流向西传播的混合Rossby-重力惯性内波相速度减慢。在半地转近似下，风速水平切变的存在，会使得波长较大（纬向波数k→0）的赤道Rossby波相对于基本气流向西传播的相速度减慢；而风速垂直切变的存在，必然会引起这种波长较大（k→0）的Rossby波出现不稳定增长，同样也会造成赤道Rossby波相对于基本气流向西传播的相速度减慢。最后通过扰动发展能量方程，说明了基本气流的水平切变和垂直切变可以为扰动的发展提供能量来源。 相似文献
10.
从球坐标(Spherical coordinate)非地转、正压水平无辐散大气运动微扰方程出发,推导出球面Rossby波方程,证明球面Rossby波的物理机制仍然是绝对涡度守恒与卢效应,但基本气流以涡度形式参与了卢效应。因球面Rossby波偏微分方程不存在经向-纬向传播的"双向简谐波(传统Rossby波)"解,则将它做经向-纬向求导分离,从而得到关于球面经向风扰动的二阶偏微分方程及与之相应的仅作纬向传播的简谐波解,但待解的二阶偏微分方程不归于数理方程中的任何特殊函数,即证明不存在以连带Legendre函数为通解的Haurwitz波。采用传统Rossby波两个通解,当作球面Rossby波两类特解,做诊断分析表明,传统Rossby波正确反映球面Rossby波的(β-平面近似)"线性部分",但球面Rossby波及其纬向波速和群速都带有地球曲率性,并且存在奇点,其中,球面谐波扰动Rossby波仍然保持槽与脊纬向对称性,但"正弦扰动"与"余弦扰动"Rossby波有一定差别,而球面指数扰动Rossby波槽与脊不具备纬向对称性,后者可以解释东、西风带槽与脊一般为纬向非对称,还可以解释台风的纬向非对称结构。 相似文献
11.
Using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) and ERA-Interim data, spatial distributions of air-sea temperature difference(ASTD) in the South China Sea(SCS) for the past 35 years are compared,and variations of spatial and temporal distributions of ASTD in this region are addressed using empirical orthogonal function decomposition and wavelet analysis methods. The results indicate that both ICOADS and ERA-Interim data can reflect actual distribution characteristics of ASTD in the SCS, but values of ASTD from the ERA-Interim data are smaller than those of the ICOADS data in the same region. In addition, the ASTD characteristics from the ERA-Interim data are not obvious inshore. A seesaw-type, north-south distribution of ASTD is dominant in the SCS; i.e., a positive peak in the south is associated with a negative peak in the north in November, and a negative peak in the south is accompanied by a positive peak in the north during April and May. Interannual ASTD variations in summer or autumn are decreasing. There is a seesaw-type distribution of ASTD between Beibu Bay and most of the SCS in summer, and the center of large values is in the Nansha Islands area in autumn. The ASTD in the SCS has a strong quasi-3a oscillation period in all seasons, and a quasi-11 a period in winter and spring. The ASTD is positively correlated with the Nio3.4 index in summer and autumn but negatively correlated in spring and winter. 相似文献
12.
The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics. 相似文献
13.
Various features of the atmospheric environment affect the number of migratory insects, besides their initial population. However, little is known about the impact of atmospheric low-frequency oscillation(10 to 90 days) on insect migration. A case study was conducted to ascertain the influence of low-frequency atmospheric oscillation on the immigration of brown planthopper, Nilaparvata lugens(Stl), in Hunan and Jiangxi provinces. The results showed the following:(1) The number of immigrating N. lugens from April to June of 2007 through 2016 mainly exhibited a periodic oscillation of 10 to 20 days.(2) The 10-20 d low-frequency number of immigrating N. lugens was significantly correlated with a low-frequency wind field and a geopotential height field at 850 h Pa.(3) During the peak phase of immigration, southwest or south winds served as a driving force and carried N. lugens populations northward, and when in the back of the trough and the front of the ridge, the downward airflow created a favorable condition for N. lugens to land in the study area. In conclusion, the northward migration of N. lugens was influenced by a low-frequency atmospheric circulation based on the analysis of dynamics. This study was the first research connecting atmospheric low-frequency oscillation to insect migration. 相似文献
14.
The atmospheric and oceanic conditions before the onset of EP El Ni?o and CP El Ni?o in nearly 30 years are compared and analyzed by using 850 hPa wind, 20℃ isotherm depth, sea surface temperature and the Wheeler and Hendon index. The results are as follows: In the western equatorial Pacific, the occurrence of the anomalously strong westerly winds of the EP El Ni?o is earlier than that of the CP El Ni?o. Its intensity is far stronger than that of the CP El Ni?o. Two months before the El Ni?o, the anomaly westerly winds of the EP El Ni?o have extended to the eastern Pacific region, while the westerly wind anomaly of the CP El Ni?o can only extend to the west of the dateline three months before the El Ni?o and later stay there. Unlike the EP El Ni?o, the CP El Ni?o is always associated with easterly wind anomaly in the eastern equatorial Pacific before its onset. The thermocline depth anomaly of the EP El Ni?o can significantly move eastward and deepen. In addition, we also find that the evolution of thermocline is ahead of the development of the sea surface temperature for the EP El Ni?o. The strong MJO activity of the EP El Ni?o in the western and central Pacific is earlier than that of the CP El Ni?o. Measured by the standard deviation of the zonal wind square, the intensity of MJO activity of the EP El Ni?o is significantly greater than that of the CP El Ni?o before the onset of El Ni?o. 相似文献
15.
Fei LIU Chen XING Jinbao LI Bin WANG Jing CHAI Chaochao GAO Gang HUANG Jian LIU Deliang CHEN 《大气科学进展》2020,37(7):663-670
正The Taal Volcano in Luzon is one of the most active and dangerous volcanoes of the Philippines. A recent eruption occurred on 12 January 2020(Fig. 1a), and this volcano is still active with the occurrence of volcanic earthquakes. The eruption has become a deep concern worldwide, not only for its damage on local society, but also for potential hazardous consequences on the Earth's climate and environment. 相似文献
16.
Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms. 相似文献
17.
Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d. 相似文献
18.
Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region. 相似文献
19.
Yuepeng PAN Mengna GU Yuexin HE Dianming WU Chunyan LIU Linlin SONG Shili TIAN Xuemei Lü Yang SUN Tao SONG Wendell W. WALTERS Xuejun LIU Nicholas A. MARTIN Qianqian ZHANG Yunting FANG Valerio FERRACCI Yuesi WANG 《大气科学进展》2020,37(9):933-938
正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on 相似文献
20.
