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西双版纳热带季节雨林树冠上生态边界层大气稳定度时间变化特征初探 总被引：3，自引：0，他引：3
为探讨热带季节雨林林冠上方大气稳定状态,为通量计算提供依据,利用2003-2004年热带季节雨林林冠上方的涡度相关法观测资料,对西双版纳热带季节雨林树冠上生态边界层内大气的稳定度频率分布进行了分析研究。计算了稳定度参数（z/L）,并对大气稳定度类型进行了划分,分析了大气稳定状态的时间变化。结果表明：在热带季节雨林林冠上方的大气稳定度频率分布存在明显的日变化。昼间不稳定状态占优势,晚上以稳定状态为主;在早晨和下午稳定状态和不稳定状态频率分布易发生变化,导致中性的大气稳定状态更容易出现;而各大气稳定状态的频率分布年和季节变化相对较小,大气不稳定状态出现频率以雾凉季最高、干热季最低;稳定状态出现频率以干热季最高、雨季最低;中性状态出现频率以雨季最高、雾凉季最低。 相似文献
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华东区域夏季行星边界层大气稳定度的气候特征及其与气溶胶的联系 总被引：2，自引：1，他引：1
利用1979-2008年夏季（6—8月）逐日NCEP／NACR再分析资料、MODIS卫星的气溶胶资料等,研究了华东区域夏季行星边界层大气稳定度的气候特征与年际变化,分析了大气稳定度和相应的加热场与气溶胶光学厚度（aerosol optical depth,AOD）的联系。结果表明：华东区域夏季行星边界层大气稳定度在空间上分布不均匀,时间上具有明显的年际变化。边界层中的非绝热加热率、大气稳定度及气溶胶光学厚度三者之间可能存在密切联系。利用经验正交函数分析了华东区域总体理查森数Rib的距平场,得到了边界层稳定度分布的3个主要模态,这3个模态所代表的边界层大气稳定度异常与夏季风环流异常密切相关,特别是P-J型遥相关波列和西太平洋副热带高压在中国东部大气边界层稳定度变化中可能起着非常重要的作用。 相似文献
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利用1990～2002年呼和浩特市区空气污染物TSP、SO2、NOx浓度的实际监测数据，分析了呼和浩特市大气污染物浓度变化的时空分布特征、大气污染与天气条件的关系。呼和浩特市市区主要以煤烟型污染为主，冬、春季比夏、秋季污染严重，采暖期比非采暖期污染严重，市区中心污染最严重。污染物的排放量及大气的稳定度状态是城市大气污染的主要影响因子，天气变化是城市大气污染物浓度变化的主导因素，局地环流是决定城市污染物分布的关键因素。因此，不同季节排污量的变化、天气条件是制作呼和浩特市大气污染预报的主要依据。 相似文献
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根据2007—2013年宁波市每日8次地面观测气象资料,运用罗氏法和统计分析法计算大气混合层高度,分析其在霾日和非霾日的不同日变化特征。结果表明宁波市霾日与非霾日混合层高度均呈白天高,夜晚低的日变化特征,夏季两者差值的日变化波动最明显,波峰时间比其他季节晚3 h。混合层高度日变化趋势与风速、气温、能见度趋于一致,霾等级越重,混合层高度越低。霾日与非霾日的气温差值除冬季呈正变温外,其他季节呈负变温,冬季14时差值最小,夜间加大,春夏季凌晨差值最小,14时最大,秋季波动不明显;风速差值除冬季夜间为正值外,其余季节为负值,秋冬季差值最小、夏季最大。大气处于不稳定状态时,混合层高度随着稳定度增加而逐渐处于稳定状态时,随着稳定度增加而降低,中性大气是宁波易致霾的大气层结。霾日与非霾日大气稳定度表现不一致,中午霾日中性大气占多数,非霾日则是不稳定大气;夜间霾日稳定—弱稳定大气和中性大气所占比例相当,非霾日稳定—弱稳定大气占多数。另外,PM_(2.5)浓度在霾日和非霾日均为白天低、夜间高的日变化特征,但霾日波动大,波峰时间晚于非霾日2 h,峰值浓度也高于非霾日2.7倍;早晨或下午到上半夜是霾日的PM_(2.5)浓度两个上升时段,上午为下降时段;非霾日的两个浓度缓升(降)时段分别出现凌晨和下午(上午和前半夜)。研究成果有助于预报员了解大气混合层高度及其对霾的可能影响,从而提高霾预报预警能力。 相似文献
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大气稳定度可标明大气湍流的强弱，在研究大气扩散时，大气的稳定度是很重要的，因为污染物在大气中扩散、稀释的速率、距离和范围受到大气稳定度的直接影响。当大气处于稳定状态，污染物在大气中扩散速率小，范围窄，最大浓度落地距离较远。当大气处于不稳定状态时，则出现截然相反的情况。因此．有必要仔细分析研究大气稳定度的变化规律。 相似文献
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兰州市低空风时空变化特征及其与空气污染的关系 总被引：7，自引：9，他引：7
对1988年至1992年兰州市环境监测站自动监测系统监测到的近地面逐时风和空气污染浓度资料以及对应时段的兰州市低空风资料乃至城，郊近40年的地面风资料做了深入的分析，并将城区与郊区对照点（榆中站）进行对比研究，揭示了风向频率变化特征和风速日变化，年变化，年际变化以及风随高度的变化规律。同时分析了对应时段空气污染的分布状况及其与风速的相关关系，为研究兰州市边界层大气动力稳定度的时空变化规律和开展空气污染预报提供了一定的依据。 相似文献
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关于热带气旋尺度变化机制的初步分析 总被引：4，自引：1，他引：4
应用小参数方法和缓变波包理论分析了热带气旋尺度变化的主要原因。分析指出：热带气旋尺度变化主要决定于其内部要 通常的热带气旋内惯性性重力波由中心外传播的情况下，当层结稳定度和惯性稳定度参数随着离中心的距离增加而增加时，热带气旋尺度增加，它可以称为热带气旋“膨胀”；而当层结稳定度和惯性稳定度参数随着离中心的距离增加而减小时，热带气旋尺度减小，它可以称为热带气旋“收缩”。 相似文献
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成都近十年大气稳定度综合研究 总被引：3，自引：0，他引：3
新颁国际标准ＧＢ／Ｔ－１３２０１－９１中规定的稳定度分类法，统计成都近十年的大气稳定度频率，研究了其分布特点和变化规律，并探讨了变化原因。对新标准中的日夜分界及δ取值法提出了相应的建议和简化意见。 相似文献
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MATHEMATICAL MODELING OF VARIATIONS ON STABLE ISOTOPIC RATIOS IN FALLING RAINDROPS 总被引：13，自引：0，他引：13
The variations of stable isotopic contents in falling raindrops are not only influenced by thehumidity conditions, but also by the stable isotopic contents in atmospheric vapor to a certainextent. If there is a difference between the isotopic contents in the vapor of the surrounding air andat the surface of the raindrops, the move of the isotopic contents from high to low values will beproduced. Usually. influenced by the evaporation process, the stable isotopic ratios in raindropsare constantly increased in the unsaturated atmosphere. The less the atmospheric humidity, themore obvious the increased range. As the enrichment rate of stable isotopes in raindrops is equal tothe outward isotopic move rate. the "pseudo-equilibrium state" appears. The influence ofevaporation on stable isotopic contents disappears in the saturated atmosphere, so that themagnitude of isotopic ratio in raindrops is dependent on the isotopic exchange between theraindrops and the surrounding atmosphere. 相似文献
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The variations of stable isotopic contents in falling raindrops are not only influenced by the humidity conditions, but also by the stable isotopic contents in atmospheric vapor to a certain extent. If there is a difference between the isotopic contents in the vapor of the surrounding air and at the surface of the raindrops, the move of the isotopic contents from high to low values will be produced. Usually. influenced by the evaporation process, the stable isotopic ratios in raindrops are constantly increased in the unsaturated atmosphere. The less the atmospheric humidity, the more obvious the increased range. As the enrichment rate of stable isotopes in raindrops is equal to the outward isotopic move rate. the "pseudo-equilibrium state" appears. The influence of evaporation on stable isotopic contents disappears in the saturated atmosphere, so that the magnitude of isotopic ratio in raindrops is dependent on the isotopic exchange between the raindrops and the surrounding atmosphere. 相似文献
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微波辐射计与探空仪测值对比分析 总被引：1，自引：0，他引：1
利用武汉站高时空分辨力探空资料(3h,30m)与同址的MP-3000A型地基微波辐射计资料,分析了微波辐射计探测偏差的日变化及时间序列变化特征。结果表明,微波辐射计对大气要素的探测具有较高的探测准确度,但仍然存在一定的探测偏差。温度的探测偏差大值区出现在午后,相对湿度及水汽密度的探测偏差大值区则在凌晨;温度及相对湿度探测误差的时间序列表现为起伏较大,而水汽密度则相对平稳,降水,特别是强降水,会对微波辐射计的探测准确度产生较明显的影响。 相似文献
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This study analyzes the relationships of stable isotopes in precipitation with temperature, air pressure and humidity at different altitudes, and the potential influencing mechanisms of control factors on the stable isotopes in precipitation in Southwest China. There appear marked negative correlations of the δ18O in precipitation with precipitation amount, vapor pressure and atmospheric precipitable water (PW)at the Mengzi, Simao and Tengchong stations on the synoptic timescale; the marked negative correlations between the δ18O in precipitation and the diurnal mean temperature at 400 hPa, 500 hPa, 700 hPa and 850hPa are different from the temperature effect in middle-high-latitude inland areas. In addition, the notable positive correlation between the δ18O in precipitation and the dew-point deficit △Td at different altitudes is found at the three stations. Precipitation is not the only factor generating an amount effect. Probably,the amount effect is related to the variations of atmospheric circulation and vapor origins. On the annual timescale, the annual precipitation amount weighted-mean δ18O displays negative correlations not only with annual precipitation but also with annual mean temperature at 500 hPa. It can be deduced that, in the years with an abnormally strong summer monsoon, more warm and wet air from low-latitude oceans is transported northward along the vapor channel located in Southwest China and generates abnormally strong rainfall on the way. Meanwhile, the abnormally strong condensation process will release more condensed latent heat in the atmosphere, and this will lead to a rise of atmospheric temperature during rainfall but a decline of δ18O in the precipitation. On the other hand, in the years with an abnormally weak summer monsoon, the precipitation and the atmospheric temperature during rainfalls decrease abnormally but the δ18O in precipitation increases. 相似文献
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Two series of tetroon flights across a long reasonably two-dimensional ridge with crest elevation of about 100 m were performed during the summers of 1977 and 1978. All of the tetroons were ballasted to float at an equilibrium level of 100 m above the ground. The first series was released in the daytime. Large instabilities were observed during windy neutral atmospheric conditions as well as on days with strong thermal convection. Under more stable conditions the air flow was observed to reflect the structure of the terrain more closely. The second series of tetroons was released on clear nights when stable atmospheric conditions prevailed. The natural wavelengths for these flights were approximately the same as the total base width of the ridge (~1.5 km). Some implications for pollutant dispersion calculations in areas of complex terrain are discussed. 相似文献
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基于小波分析的地面大气电场观测数据处理技术研究 总被引：1，自引：1，他引：0
使用南京信息工程大学实验场的AMEO340电场仪一年观测试验资料,将大气电场仪采样序列数据经快速傅里叶变换,得到序列的功率谱,对晴天和伴有闪电天气的地面大气电场数据进行小波函数为sym5的7层分解,某种程度上降低了地面大气电场数据波形的重叠度。通过对伴有闪电天气的地面大气电场数据进行小波7层分解,地面大气电场信号的低频部分不仅突出显示出地面大气电场值的主要变化趋势,而且能清晰地分辨出闪电过程中较强的正负地闪次数,为利用地面大气电场强度值的变化特征进行闪电预警提供了更有效的信息。 相似文献
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本文采用二阶闭合的湍流边界层模式,进行一系列数值试验以模拟边界层中连续线源的扩散状况。试验表明:无论在稳定的或不稳定的边界层中,高源的扩散能力都低于低源;在稳定层中,粗糙地表上的大气扩散能力高于光滑表面;在相同风速和地表净辐射情况下,粗糙表面上的大气扩散能力反而低于光滑表面;对流边界层中存在反梯度输送,因而K理论的应用受到限制。试验还表明,修正的Kazanski-Monin参数可能比Monin-Obukhov长度更能反映大气的扩散能力。 相似文献
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Modified refractivity (M) profile is an important parameter to describe the atmospheric refraction environment, as well as a key factor in uniquely evaluating electromagnetic propagation effects. In order to improve the model-derived M profile in stable (especially very stable) conditions, three nonlinear similarity functions, namely BH91, CB05, SHEBA07, are introduced in this paper to improve the original Babin_V25 model, and the performances of these modified models are verified based on the hydrometeorological observations from tower platforms, which are finally compared with the original Babin_V25 model and Local_HYQ92 model. Results show that introducing nonlinear similarity functions can significantly improve the model-derived M profile; especially, the newly developed SHEBA07 functions manage to reduce the predicted root mean square (rms) differences of M and M slope (for both 0–5 m and 5–40 m) by 64.5%, 16.6%, and 60.4%, respectively in stable conditions. Unfortunately, this improved method reacts little on the evaporation duct height; in contrast, Local_HYQ92 model is capable of reducing the predicted rms differences of M, M slope (for both 0–5 m and 5–40 m), and evaporation duct height by 76.7%, 40.2%, 83.7%, and 58.0% respectively. Finally, a new recommendation is made to apply Local_HYQ92 and Babin_SHEBA07 in very stable conditions considering that M slope is more important than evaporation duct height and absolute M value in uniquely determining electromagnetic propagation effects. 相似文献
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The stable-hydrogen kinetic isotope effects (KIEs) for a series of n-alkanes in reaction with chlorine atoms in the gas phase were studied in a 25-L PTFE reaction chamber at 298 K. The time
dependence of both the stable hydrogen isotope ratios and the concentrations was determined using a gas chromatography pyrolysis
isotope ratio mass spectrometry (GC-P-IRMS) system. The following KIE values, in per mil (‰), were obtained: 39.6 ± 2.7 (n-butane), 28.2 ± 0.9 (n-pentane), 24.6 ± 1.0 (n-hexane), 24.0 ± 1.2 (n-heptane), 17.9 ± 3.3 (n-octane), 15.1 ± 0.7 (n-nonane), and 14.9 ± 1.8 (n-decane). The errors given are the ±1σ standard errors. These measured values were used to derive structure–reactivity relationship
(SRRs), which allow for the calculation of the KIEs for the reaction of n-alkanes with Cl atoms. The results of the calculations agree with the measurements within few per mil or better. The site
specific stable hydrogen isotope fractionation effects for methyl groups are approximately a factor of 3 larger than those
for methylene group, a finding which is qualitatively similar to site-specific stable hydrogen isotope effects reported in
literature for reactions of alkanes with the OH radical. Because n-alkanes with close to natural isotope ratios (i.e. neither artificially labeled, nor enriched or depleted) were used, the
KIE data are directly applicable to atmospheric studies. Based on these KIE values, the impact of Cl-atom reactions of the
stable hydrogen isotope ratio on alkanes are estimated for different levels of Cl-atom concentrations. On average in the troposphere,
the impact of Cl-atom reactions of the stable hydrogen isotope ratio of n-alkanes will be small. However, in regions of the troposphere with high concentrations of Cl atoms, such as the tropospheric
ozone depletion episodes during polar sunrise, the impact of Cl-atom reactions is substantial.
An erratum to this article is available at . 相似文献