The evolution of the nocturnal temperature inversion

Under conditions of strong stability, it is observed that the temperature differential across the stable boundary layer rises faster than the theoretically predicted square root time response. Perturbations in the temperature field are observed to propagate vertically at a rate of approximately 0.03 m s^-1.     

Radiative destabilization of the nocturnal stable atmospheric boundary layer over the desert

Radiative destabilization of the nocturnal stable atmospheric boundary layer (NSABL) over homogeneous desert terrain is predicted by an analytical model based on a modified diffusion equation. The model applies late at night under calm, dry conditions when long-wave radiative transfer dominates the NSABL evolution. A three-layer structure for the NSABL is proposed: a shear sub-layer closest to the surface, a radiative sub-layer which contains the inversion top, and a coupling sub-layer which matches the NSABL with the residual layer aloft. A sub-sub-layer called the nocturnal internal boundary layer (NIBL) is nested within the radiative sub-layer and comprises the temperature maximum. The model can explain: (1) maximum cooling in the NIBL, (2) deepening of the NIBL, (3) radiative destabilization of the NSABL, and (4) possible surface warming before sunrise. An example from the Mohave Desert, USA is presented, and the observed temperature profile compares favorably with the model solution.     

The mesometeorological temperature field in a mediterrannean-alpine region

Summary The structure of the surface-air temperature field in meso-alpha and meso-beta scale is studied for the purpose of regionalisation and for the optimum interpolation meso-analysis in Slovenia. The possibilities of subregionalisation, of the split into the horizontal and the vertical part of autocorrelation function and of separation according to the general weather type have been tested. It was found that the influence of weather type could not be introduced without the simultaneous introduction of first-guess fields for each weather type. The relative importance of first-guess field versus the importance of the type of autocorrelation function is estimated by several tests of the optimum interpolation meso analysis.With 6 Figures     

贵州喀斯特石漠化植被群落调查及其成因探讨

对贵州黔西南州、六盘水市部分喀斯特石漠化地区不同季节的植被群落进行了调查,结果显示,植被群落的季节变化随地区气候、地质、土壤、石漠化程度以及人为干扰程度的不同而不同;黔西南州石漠化区植被盖度较六盘水市相应石漠化程度的样地盖度低（特别以草木、灌木为最）。     

中国黑戈壁地区气候变化特征

利用1959-2011年黑戈壁地区12个气象站的年平均气温、年降水量、年平均地面风速、年大风日数和年沙尘暴日数,采用气候趋势法分析了黑戈壁地区气候变化基本特征,并与荒漠化地区气候变化数据相比较。结果表明：黑戈壁地区年平均气温增温速率为0.34 ℃/10 a,高于0.25 ℃/10 a的荒漠化地区;年降水量增长率为1.33 mm/10 a,略小于荒漠化地区1.66 mm/10 a的年降水量增长率;年地面风速减小率为-0.10 m·s^-1/10 a,不如荒漠化地区-0.14 m·s^-1/10 a的值;年大风日数减少率为-1.83d/10a,远不如荒漠化地区-3.44 d/10 a的值;年沙尘暴日数减少率为-1.83 d/10 a,比荒漠化地区-1.77 d/10 a的减少率略明显。Mann-Kendall方法检验表明,除年降水量外,其他气候因子只有一个突变点。不同气候因子的空间分布是不同的。     

Prediction of Monthly Mean Surface Air Temperature in a Region of China

In conventional time series analysis, a process is often modeled as three additive components： linear trend, seasonal effect, and random noise. In this paper, we perform an analysis of surface air temperature in a region of China using a decomposition method in time series analysis. Applications to the National Centers for Environmental Prediction/the National Center for Atmospheric Research （NCEP/NCAR） Collaborative Reanalysis data in this region of China are discussed. The main finding was that the surface air temperature trend estimated for January 1948 to February 2006 was not statistically significant at 0.5904℃ （100 yr）^-1. Forecasting aspects are also considered.     

Seasonal relationship between temperature,precipitation and snow cover in a mountainous region

Summary An analysis of correlation coefficients for climatological data covering the period 1901–1994 or 1931–1994 for six locations in Switzerland has been made in order to highlight the relationships between temperature, precipitation (rain and snow) and snow in summer and in winter. The results show that colder summers tend to be associated with more precipitation, mainly in terms of the frequency of occurrence of precipitation, but also in terms of its abundancy. In winter, sites located at lower altitudes behave differently from those at higher elevations. At lower altitudes, warmer winters tend to be rainier and to have less snow (only a small part of winter precipitation falls in the form of snow). Above 1000–1500 m, correlations between temperature on the one hand, and precipitation or snow on the other, tend to be weaker than at lower elevations; warmer winters are associated with less snow but also with less precipitation in general, while the relationship between precipitation and snow is stronger.These results confirm that during cold periods of the past, such as Löbben Phase (1400 BC — 1230 BC) cold summers were probably linked to frequent and abundant precipitation. These conditions led to increased mortality as well as to population migrations. In terms of potential future global warming, if the current temperature/precipitation relationships remain unchanged, then warmer summers will likely be linked to a decrease in precipitation. Higher winter temperatures can be expected to lead to a general decrease of snow and to a decrease in precipitation, but only at higher elevations; warmer winters would conversely be associated with an increase in precipitation at lower altitudes.With 4 Figures     

Wave and turbulence structure in a disturbed nocturnal inversion

Acoustic sounder and tower data obtained at the Boulder Atmospheric Observatory (BAO) are used to examine several features of the wave and turbulence structure associated with a disturbed nocturnal inversion. General features, including mean fields and Richardson number, for the case selected for this study are presented. Spectral analysis of the tower data reveals a separation of energy into wavelike and turbulent fluctuations. Analysis of the heat flux, however, shows upward counter-gradient fluxes in the vicinity of a low-level jet and near the top of the inversion. Cospectral analysis shows that the major contribution to the upward heat flux occurs at frequencies that would normally be considered characteristic of waves. In some cases, the upward flux is associated with a phase shift between vertical velocity w and fluctuating temperature θ different from the quadrature relation that would be expected of internal waves. Time series analysis reveals that these unexpected positive fluxes occur in relatively short bursts. Analysis of time series of θ and w in other cases, as well as inspection of acoustic sounder records, shows that sometimes such upward fluxes can result from a combination of wave motion and horizontal temperature advection. In this case the advection is associated with a shallow cold front.     

造成东北区夏季(5—9月)持续低温的长期天气过程的分析

一、引言 5—9月持续低温对我国东北地区粮豆总产量影响很大,研究夏季(5—9月)持续低温的长期灾害性天然预报,对农业生产是有很大意义的。 夏季(5—9月)持续低温的长期天气预报方法国内外虽都有所讨论,但还不如降水预报方面内容丰富,因此对我们来讲是一个较新的课题。本文企图从造成东北地区夏季持续低温的长期天气过程入手,研究稳定性超长波的活动规律,提出一种初步的季节长期预报方法。     

Vertical profiles of the structure parameter of temperature in the stable,nocturnal boundary layer

Vertical profiles of the structure parameter of temperature C _infT ^sup2 in the stable, nocturnal boundary layer (NBL) have been obtained with the analytic models described by Nieuwstadt (1984, 1985) and Sorbjan (1986) and the numerical model of Duynkerke and Driedonks (1987). These theoretical profiles are compared with observed profiles from the meteorological mast at Cabauw, The Netherlands. From the observations, it is found that C _infT ^sup2 is large in the surface layer and small at the top of the NBL. Observations during nights with moderate geostrophic winds or during the first few hours of nights with a high geostrophic wind show a continuous decrease of C _infT ^sup2 from the surface layer to the top of the NBL. Observations made later on nights with a high geostrophic wind show the development of a maximum of C _infT ^sup2 at about three quarters of the NBL. From the comparison with the models, we conclude that the observed profiles are most satisfactorily described by the model of Duynkerke and Driedonks.     

虎林市日最高、最低气温的不对称变化研究

虎林市地处黑龙江省东部，完达山山脉下，所在地区有原始森林、自然湿地和天然草场，其经济结构是以农业为主，兼顾有牧业和林业。但由于在20世纪50年代、70年代和80年代末到90年代初的3次大规模开荒，使森林、草原和湿地的面积锐减，也对当地的气候与生态环境产生了明显的影响。气候变暖的趋势十分明显，为了探讨气温趋势变化的规律，着眼于研究日最高、最低气温的不对称变化状况及其特点。     

On the evolution of the height and temperature difference across the nocturnal stable boundary layer

Evidence is furnished which indicates that in some cases the height of the stable boundary layer (SBL) and the magnitude of the temperature difference across the SBL may be more appropriately described by an error function erf(t/) rather than the generally accepted square root time dependence. The time constant was observed to have values of one to three hours. The discovery has been found to be site dependent, however, as data from other sites follow the usual square root time evolution.     

阿勒泰地区气温日较差的气候变化特征

利用线性趋势法对1961-2008年阿勒泰地区7个气象站点气温日较差进行趋势研究,并根据各因子趋势值,应用相关统计法分析了影响气温日较差呈减小趋势的因子。结果表明：阿勒泰地区四季日较差呈现显著减小趋势,其中冬季最显著,秋季变化最弱。各季节最低气温上升趋势最明显,而最高气温上升趋势较弱。阿勒泰地区与月平均气温日较差相关性最强的因子是日照时数,呈正相关;其次分别为总云量、降水量和水汽压,都呈负相关。年气温日较差与降水量和水汽压相关性最大。     

巴丹吉林沙漠北缘拐子湖近地层湍流能谱特征分析

利用2013年6月巴丹吉林沙漠拐子湖地区流沙下垫面的陆气通量观测资料,计算并分析了该研究区不同大气稳定层结条件下的湍流速度各分量谱和温度谱及湍流的局地各向同性特征。结果表明:该研究区风速各分量的湍流强度随平均风速的增加而逐渐减小,当平均风速2 m/s时,风速各分量的湍流强度逐渐稳定且基本限定在0.5以内。在不同大气稳定度下,湍流速度和温度能谱曲线在惯性副区内逐渐有合并趋势且遵循Kolmogorov提出的-2/3定律,速度各分量谱在高频段均满足各向同性且符合低频限制理论。随着稳定度的增加,风速分量的能谱曲线逐渐降低且向高频端移动,风速分量和温度能谱对应的谱峰长度则逐渐减小。该研究区水平湍流尺度范围为9.0~600 m,垂直湍流谱峰波长为10.79~75 m。该结果介于草地和森林下垫面之间,与塔克拉玛干沙漠腹地的试验结果较为接近。     

The temperature of the sea-surface in the region of the Aegean and its relation to air temperature

Summary In this study the annual course of the air and sea-surface temperature in the Aegean sea is examined and a possibly existing relation between these two meteorological parameters is sought.To do this the monthly values of both elements for the period 1971–1975 were cross-correlated. It was found that in general the observed delay of the maximum and minimum values of the temperature of the sea was of the order of one month.With 1 Figure     

Mesoscale data assimilation and prediction of low stratus in the Alpine region

Summary A number of problems related to mesoscale numerical prediction of low stratus in the Alpine region are formulated, and addressed in a series of experiments for two wintertime cases. These problems include modelling aspects and issues of data assimilation which are relevant particularly in relation to the observation nudging technique. A focus is on the influence of orography.A comparison of operational optimum interpolation, and nudging of routine rawinsonde and surface-level data reveals that nudging often yields better analyses and forecasts of low stratus, and notably of the sharp vertical temperature and humidity gradients. However, the humidity advection scheme of the model and, near steep terrain, particularly the horizontal diffusion along the model's -levels are identified to contribute to spurious vertical smoothing which can result in erroneous cloud dissipation. On occasions, forecasts succeeding a nudging period are more sensitive to this process due to the sharper initial vertical gradients.Specific problems of representiveness arise when low-level rawinsonde information is spread laterally along the sloping -levels from low to high terrain. A new concept for -layer models is introduced by speading the observational information along isentropic surfaces, and this tends to improve the low stratus prediction over steep and even moderate orography. A partly successful attempt to take advantage of the steep Alpine orography is made by applying this concept to surface-level humidity data from a high-resolution network of Alpine surface stations which are distributed relatively uniformly in the vertical.With 19 Figures