沙漠陆面过程与沙漠小气候研究进展

陆面过程是影响大气环流和气候变化的基本物理、生化过程之一。沙漠陆面过程及相应的小气候效应已经成为当前沙漠气象研究的热门问题。近年来,在沙漠陆面过程野外观测、陆面过程特征及参数化、陆面过程模拟、小气候及陆面过程对小气候影响等方面已取得重大进展。本文对于沙漠小气候、沙漠陆面过程及沙漠陆面过程参数化进行了简要概述,重点总结了国内外在沙漠地区气候考察、沙漠边界层高度、沙漠热力环流、绿洲效应、塔克拉玛干沙漠气候特征、沙漠陆面过程野外观测试验及结果、沙漠陆面过程对气候的影响、沙漠陆面过程参数化方案方面的成果,回顾了近年来利用地面观测设备和数值模式等对气候效应和陆面过程直接观测和数值模拟所获得的观测事实和模拟试验,并讨论了其陆面过程参数化对模拟的影响,在总结前人研究成果的基础上对未来的研究方向进行了讨论。     

西北干旱区荒漠戈壁陆面过程的数值模拟

首先利用“中国西北干旱区陆 气相互作用试验”2 0 0 0年 5～ 6月在甘肃敦煌进行的陆 气相互作用野外试验的观测资料 ,确定了西北干旱区荒漠戈壁的陆面过程参数 ,并用这些参数改进了已有的陆面过程模式。然后用该陆面过程模式对敦煌陆 气相互作用野外试验荒漠戈壁上的大气感热通量、潜热通量、摩擦速度以及净辐射、地表和土壤温度、土壤水份等重要陆面变量进行了模拟 ,结果表明 ,模拟值与观测值非常接近 ,这说明改进后的模式对干旱区陆面过程有较强的模拟能力     

陆面模式CLSM的设计及性能检验Ⅰ.模式设计

在现有陆面模式的基础上,详细考虑了地气系统中的积雪、土壤水热传输、植被及湍流边界层中的各种物理过程,发展了一个既能反映积雪变化、干旱/半干旱区地气交换过程,同时又能描述不同陆面状况物理过程的陆面模式(Comprehensive Land Surface Model,简称CLSM),改善了陆面模式对全球范围内不同下垫面条件下的陆面过程及地-气交换过程的模拟能力.     

基于不同陆面参数化方案的高温天气数值模拟

基于3种不同的陆面过程方案(SLAB、NOAH和RUC方案)利用WRF模式对2009年7月发生在江苏沿江及苏南地区包括沪宁高速公路在内的一次高温天气过程进行了对比模拟和分析.结果表明:①WRF模式中耦合陆面参数化方案后的试验结果更接近实况,且模拟的高温天气过程对不同陆面方案的选择较为敏感;②SLAB、NOAH、RUC ...     

陆面过程模式研究简评

主要总结了陆面过程模式的发展状况, 对一些国际间合作进行的计划、试验成果以及我国在这方面的研究情况加以介绍和评述, 最后给出陆面模拟研究中存在的难点、问题及可能的解决途径.     

一个改进的陆面过程模式及其模拟试验研究第一部分:陆面过程模式及其“独立(off-line)”模拟试验和模式性能分析

文中在综合比较过去各类陆面过程模式优缺点的基础上,主要参考ＢＡＴＳ模式,发展了一个陆面过程模式（ＬＰＭ－ＺＤ）。它具有以下几个特征：１．采用物理方程和经验解析公式相结合的方法进行土壤温度和土壤水汽的求解。在上层土壤,土壤分层较细并采用温度传导和水汽扩散方程求解,而在下层土壤,土壤分层较粗并利用经验方法处理。２．考虑了降水分布的次网格特征及其对陆面水文产生的重要影响。３．较全面地考虑了雪盖对陆面过程的各种影响：对陆面水文的影响、对土壤热传导的影响以及雪盖的高反照率对辐射收支的影响。利用３组单点观测试验资料对陆面过程模式ＬＰＭ－ＺＤ进行了“独立（ｏｆ－ｌｉｎｅ）”模拟试验。模拟结果表明陆面过程模式ＬＰＭ－ＺＤ具有较好的模拟性能,能够比较准确地模拟不同气候区的多种下垫面类型的陆面过程变化特点,模拟结果与观测基本一致。进而又利用一组观测资料和模式ＬＰＭ－ＺＤ进行了一系列敏感性模拟试验,试验结果表明模式ＬＰＭ－ＺＤ对一些参数的确定非常敏感,如初始土壤水汽、植被的物理特性参数以及降水次网格分布因子等,因此提高确定这些参数的准确性是改进陆面模式的重要内容之一。     

边界层和陆面过程对中国暴雨影响研究的进展

总结了近年来我国学者关于边界层和陆面过程对中国暴雨影响的研究成果。此类研究主要应用中尺度数值模式,有的对边界层过程和陆面过程做敏感性试验,有的则对模式中边界层和陆面过程参数化作改进。结果表明：边界层和陆面过程对我国暴雨有明显影响。主要表现在影响暴雨的强度以及使暴雨中心位置有一定的变动,但决定暴雨发生发展的主要因子是大中尺度动力过程。对边界层和陆面过程的改进能有效改善数值模式对暴雨的模拟。     

黄土高原陆面水分的凝结现象及收支特征试验研究

中国黄土高原是全球独特的地理区域,其陆面水分过程比较特殊。利用黄土高原陆面过程试验研究(LOPEX)的陇中黄土高原定西陆面过程综合观测站的资料,分析了陆面水分凝结现象及其出现频率与局地微气象条件的关系,研究了露水(霜)量及其出现频率的季节分布特征以及受降水和天气阴、晴的影响规律。同时,对比分析了降水、露水、雾水和土壤吸附水对陆面水分的贡献率,讨论了涡动相关法、蒸渗计和蒸发皿观测的陆面蒸发量的差别及其与陆面水分来源的年平衡关系,给出了半干旱区陆面水分平衡的日循环特征。发现露水对风速、大气湿度、近地层温度梯度的依赖很强,一般在风速为1.5 m/s、相对湿度大于80%和逆温强度为0.25℃的情况下露水(霜)量最大;刚降水后的晴天露水量比较大;实际蒸散量与蒸发力的差距十分明显,陆面水分平衡特征表现为一个"呼吸"过程。     

大气环流模式中陆面过程的参数化及其敏感性研究

本文就大气环流模式中引入陆面过程的各种参数化方法及大气环流和降水对各种陆面过程的敏感性研究进行了综述.首先指出大气环流模式中引入陆面过程的必要性;然后介绍了大气环流模式中陆面过程参数化的历史和现状,以及大气对陆面过程的敏感性;最后是对今后研究的展望.     

不同边界层和陆面过程参数化方案对比分析

利用WRF模式选用不同的边界层参数化方案 (YSU、MRF) 结合三种陆面过程方案 (RUC、SLAB、Noah) , 模拟了2011年5月1~3日的四川东部暴雨过程, 对不同参数化方案结合不同陆面过程结果进行对比试验基础上发现, 模式对24h降水落区及强度有较强预报能力, 但对单站小时降水分布的预报能力还需改进;不同边界层方案与陆面过程的对比试验说明降水对于边界层物理过程有一定敏感性, 各试验的差异主要体现在对暴雨中心雨强以及降水峰值强度和峰值出现时段的预报上;WRF模式基本上能够模拟出边界层要素日变化特征。      

Analysis on Precipitation Efficiency of the “21.7” Henan Extremely Heavy Rainfall Event

A record-breaking heavy rainfall event that occurred in Zhengzhou, Henan province during 19–21 July 2021 is simulated using the Weather Research and Forecasting Model, and the large-scale precipitation efficiency(LSPE) and cloud-microphysical precipitation efficiency(CMPE) of the rainfall are analyzed based on the model results. Then, the key physical factors that influenced LSPE and CMPE, and the possible mechanisms for the extreme rainfall over Zhengzhou are explored. Results show that water v...     

新疆博乐垦区人工防雹效果的统计评估

为了客观地评估博乐垦区多年开展人工防雹的作业效果，利用兵团博乐农五师垦区1976--2003年中，后15年开展防雹工作和前13年未开展防雹工作期间的年雹灾面积资料，运用简单序列检验法、不成对秩和检验法以及t-检验法等统计学的方法进行了人工防雹作业效果统计评估分析。结果为：人工防雹作业使平均年雹灾面积减少841．53hm^2，雹灾面积相对减少率为26．56％，统计显著性水平达到α=0．05。因此，博乐垦区人工防雹作业效果显著。     

Air temperature anomalies of summer 2010 measured at the high-altitude meteorological mast in Obninsk

Presented are the results of measurements of air temperature, wind direction, and relative humidity of the air at the high-altitude meteorological mast in the town of Obninsk. The measurements were carried out in the period of hot weather in July?CAugust 2010 near the Earth??s surface, as well as at the heights of 121 and 301 m. The wind roses and maximum daily temperatures are compared with the similar climatic characteristics obtained for the period of 1970?C2009. It is shown that the period from July 15 to August 18, 2010 was abnormal both in the air temperature characteristics and in the distribution of wind direction at all mentioned heights.     

Simultaneous observations of SAO and QBO in winds, temperature and ozone in the tropical middle atmosphere over Thumba (8.5��N, 77��E)

Owing to the importance of middle atmosphere, recently, a Middle Atmospheric Dynamics (MIDAS) program was carried out during the period 2002?C2007 at Thumba (8.5°N, 77°E). The measurements under this program, involving regular radiosonde/rocket flights as well as atmospheric radars, provided long period observations of winds and temperature in the middle atmospheric region from which waves and oscillations as well as their forcing mechanisms particularly in the low-latitude middle atmosphere could be analyzed. However, a detailed analysis of the forcing mechanisms remains incomplete due to the lack of important measurements like ozone which is a significant contributor to atmospheric dynamics. Presently, profiles of ozone are available from TIMED/SABER (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broad Emission Radiometry) satellite globally from about 15 to 100?km, over multiple years since 2002. In this regard, a comprehensive study has been carried out on ozone and its variability at Quasi Biennial Oscillation (QBO) and Semiannual Oscillation (SAO) scales using TIMED/SABER ozone observations during the MIDAS campaign period. Before using the TIMED/SABER ozone measurements, an inter-comparison has been carried out with in situ measurements of ozone obtained under the Southern Hemisphere Additional Ozonesondes (SHADOZ) campaign for the year 2007 at few stations. The inter-comparison showed very good agreement between SABER and ozonesonde derived ozone profiles. After validating the SABER observations, ozone profiles are used extensively to study the QBO and SAO along with temperature and winds in the 20?C100?km height region. It is known that the SAO in mesosphere and stratosphere are in opposite phases, but the present study for the first time reports the aspect of opposite phases in the mesosphere itself. Thus, the present work attempts to study the long-period oscillations in stratosphere and mesosphere in ozone, temperature and winds simultaneously for the first time over this latitude. These observations provided a unique opportunity to explore long-period oscillations in chemistry, dynamics and thermal structure of the middle atmosphere simultaneously.     

Interdecadal variability of the relationship between the East Asian winter monsoon and ENSO

Summary The authors examine relationships between the East Asian winter monsoon and the ENSO, particularly on the interdecadal timescales. Based on the analyses of SLP data from 1899 to 1997, the East-Asian winter monsoon index (WMI) is defined as the zonal difference of SLP between ∼120° E and ∼160° E. It is found that 18 out of 28 strong winter monsoon years are either before the development of an El Ni?o or during the decaying La Ni?a event, 12 out of 28 weak winter monsoon are before the development of a La Ni?a or during the decaying El Ni?o event. There is a significant positive correlation coefficient value of about 0.49 between the normalized 11-yr running mean of WMI and ENSO index, however, the WMI-ENSO relationship is not consistently highly correlated. The temporal evolution of correlation between WMI and ENSO indices in both 11-yr and 21-yr moving window shows that the WMI-ENSO relationship clearly undergo low-frequency oscillation. Obviously, both observational and IPSL air-sea coupled modeling WMI index has a near-decadal peak with PDO timescales and internal peaks with ENSO timescales by applying the Multitaper method. Moreover, the cross wavelet and wavelet coherence analysis of WMI/ENSO indicate that there is a larger significant sections with an in phase behavior between WMI and ENSO at period of 20–30 yrs, suggesting that the interdecadal variation of the WMI-ENSO relationship might exist.     

The triggering effect of near-equatorial cyclones on El Niño

The relationship between tropical cyclones developing in the Northwest Pacific and El Ni?o is analysed and the triggering mechanism of the near-equatorial cyclones on El Ni?o is proposed. It is pointed out that the near-equalorial tropical cyclones developing equatorward of 10oN can intensify equatorial westerlies and produce Kelvin waves, which propagate to the South American Coasts in about 2-3 months, inducing SST to rise there. The near-equatoral cyclones play an essential role in El Ni?o. The beginning period of El Ni?o ranges from January to May. The number of near-equatorial cyclones developing in this period determines whether El Ni?o can be generated or not. The persistence period is from June to September. El Ni?o can not continue developing unless there are adequate near-equatorial cyclones. If there are not, the developed El Ni?o will be broken down. The period from October to December is called the developing period. During this period El Ni?o may approach its culmination only when adequate near-eqatorial cyclones have been developed east of 140oE, especially east of 160oE.     

球面正压粘性大气的运动特征

通过对球面正压粘性大气非线性扰动的研究表明:由于波动之间的弱非线性相互作用，球面小扰动的波包演变是由一种较为简单的方程形式控制，当此粘性力消失时，该方程为非线性Schr?dinger方程。研究结果还表明:非线性Schr?dinger孤立波的形成，有两个因子非常重要，一是运动的球面性，另一个则是基本风场的经向切变。前者反映了球面运动的特殊性。本文还从另一个角度证明了粘性力的作用对波动起着加强能量的耗散作用，不利于这种几率波（Schr?dinger 孤立波）的形成。     

Validation of a method to estimate direct normal irradiance of UVA and PAR bands from global horizontal measurements for cloudless sky conditions in Valencia, Spain, by a measurement campaign

A method is proposed to provide measurement of direct normal solar irradiance of bands with wavelength ranges (315?C400?nm, 400?C700?nm) from measurements of global horizontal band irradiance for cloudless sky conditions in Valencia. Global and normal direct irradiance data for every air mass were obtained by applying the SMART2 model to the atmosphere of Valencia. The direct normal to global irradiance ratio was parameterized versus the relative optical air mass. A measurement campaign of global horizontal and diffuse irradiance of UVA and PAR bands was carried out in Valencia, after which, the inferred direct normal irradiance was compared with those provided by the method. The result of the comparison shows that the method is acceptably accurate. The proposed model tends to underestimate the direct normal irradiance of the UVA band by 6%, although for values below 25?W/m² the model overestimates the direct irradiance by 6%, while for values above 25?W/m² the model underestimates it by 10%. The other two error estimators used ranging from 11% to 15% are similar in the defined interval measurements in relation to the whole UVA band. Regarding the PAR band, the model overestimates the direct normal irradiance of the PAR band by only 2.2%. With this, the results of the PAR band are more conclusive, as it has been found that for direct normal irradiance values higher than 280?W/m² the MBE error is almost zero and the other two estimator errors are small, about 5%.     

Wind statistics for coastal stations in Cyprus

Summary ?A statistical analysis of wind speed and direction data for five selected meteorological stations at the Cyprus coast, is carried out in this study. Daily, monthly and annual variations of wind speed are established. The Weibull distribution statistics of the sites are also determined. In addition, an attempt is made to find the sea-breeze circulation effects in the same wind data. The wind statistics obtained are expected to serve as a validation test for wind energy applications, mainly along the southeastern coastline. Received April 5, 2001; revised February 13, 2002; accepted March 3, 2002     

Long-Term Variability of the Wind Field over the Indian Ocean Based on ERA-Interim Reanalysis

A detailed study of long-term variability of winds using 30 years of data from the European Centre for Medium-range Weather Forecasts global reanalysis (ERA-Interim) over the Indian Ocean has been carried out by partitioning the Indian Ocean into six zones based on local wind extrema. The trend of mean annual wind speed averaged over each zone shows a significant increase in the equatorial region, the Southern Ocean, and the southern part of the trade winds. This indicates that the Southern Ocean winds and the southeast trade winds are becoming stronger. However, the trend for the Bay of Bengal is negative, which might be caused by a weakening of the monsoon winds and northeast trade winds. Maximum interannual variability occurs in the Arabian Sea due to monsoon activity; a minimum is observed in the subtropical region because of the divergence of winds. Wind speed variations in all zones are weakly correlated with the Dipole Mode Index (DMI). However, the equatorial Indian Ocean, the southern part of the trade winds, and subtropical zones show a relatively strong positive correlation with the Southern Oscillation Index (SOI), indicating that the SOI has a zonal influence on wind speed in the Indian Ocean. Monsoon winds have a decreasing trend in the northern Indian Ocean, indicating monsoon weakening, and an increasing trend in the equatorial region because of enhancement of the westerlies. The negative trend observed during the non-monsoon period could be a result of weakening of the northeast trade winds over the past few decades. The mean flux of kinetic energy of wind (FKEW) reaches a minimum of about 100?W?m^?2 in the equatorial region and a maximum of about 1500?W?m^?2 in the Southern Ocean. The seasonal variability of FKEW is large, about 1600?W?m^?2, along the coast of Somalia in the northern Indian Ocean. The maximum monthly variability of the FKEW field averaged over each zone occurs during boreal summer. During the onset and withdrawal of monsoon, FKEW is as low as 50?W?m^?2. The Southern Ocean has a large variation of about 1280?W?m^?2 because of strong westerlies throughout the year.