Stratiform Cloud—Inversion Characterization During the Arctic Melt Season

Data collected during July and August from the Arctic Ocean Experiment 2001 illustrated a common occurrence of specific-humidity (q) inversions, where moisture increases with height, coinciding with temperature inversions in the central Arctic boundary layer and lower troposphere. Low-level stratiform clouds and their relationship to temperature inversions are examined using radiosonde data and data from a suite of remote sensing instrumentation. Two low-level cloud regimes are identified: the canonical case of stratiform clouds, where the cloud tops are capped by the temperature inversion base (CCI—Clouds Capped by Inversion) and clouds where the cloud tops were found well inside the inversion (CII—Clouds Inside Inversion). The latter case was found to occur more than twice as frequently than the former. The characteristic of the temperature inversion is shown to have an influence on the cloud regime that was supported. Statistical analyses of the cloud regimes using remote sensing instruments suggest that CCI cases tend to be dominated by single-phase liquid cloud droplets; radiative cooling at the cloud top limits the vertical extent of such clouds to the inversion base height. The CII cases, on the other hand, display characteristics that can be divided into two situations—(1) clouds that only slightly penetrate the temperature inversion and exhibit a microphysical signal similar to CCI cases, or (2) clouds that extend higher into the inversion and show evidence of a mixed-phase cloud structure. An important interplay between the mixed-phase structure and an increased potential for turbulent mixing across the inversion base appears to support the lifetime of CII cases existing within the inversion layer.     

Impacts of Cumulus Convective Parameterization Schemes on Summer Monsoon Precipitation Simulation over China

By using the Betts-Miller-Janjic, Grell-Devenyi, and Kain-Fritsch cumulus convective parameterization schemes in theWeather Research and Forecasting (WRF) model, long time simulations from 2000 to 2009 are conducted to investigate the impacts of different cumulus convective parameterization schemes on summer monsoon precipitation simulation over China. The results show that all the schemes have the capability to reasonably reproduce the spatial and temporal distributions of summer monsoon precipitation and the corresponding background circulation. The observed north-south shift of monsoon rain belt is also well simulated by the three schemes. Detailed comparison indicates that the Grell-Devenyi scheme gives a better performance than the others. Deficiency in simulated water vapor transport is one possible reason for the precipitation simulation bias.     

山西省层状云飞机云物理观测试验结果分析

利用山西省2008年-2010年64架次云结构的粒子测量系统（DMT）探测资料,配合地面观测和卫星资料统计分析了层状云系的宏微观特征。发现：降水性层状云低云含水量垂直方向上平均为0．03g,m^3,中云含水量垂直方向上平均为0．05g／m30对比分析降水云和非降水云系的微物理特征量,两者存在显著的差异,降水性层状云云粒子有效半径要达到10μm-14μm。对云系不同温度层的微物理特征和云中水分按不同粒子尺度的分配特征进行了对比分析,结果表明：降水性层状云在垂直方向上的微物理结构特征非常明显,也是分层的。高层主要是冰相粒子,主要是冰雪晶,随高度降低冰雪晶的尺度增大,在四个典型温度层的观测中,LWC、云粒子及降水的浓度、尺度相较有很大不同。云中水分按不同粒子尺度的分配可以看出,直径20μm、30μm的粒子含水量较高,对云中液态水含量的贡献较大,降水粒子主要由20μm、30μm的粒子转化。     

滞后平均法（LAF）在热带气旋路径集合预报中的应用

本文用-正压模式，采用滞后平均法(LAF)对2000年热带气旋进行路径集合预报试验，并与基于热带气旋初始结构扰动的集合预报方法进行了比较分析，结果表明LAF方法对热带气旋路径预报具有较好的改进作用。但LAF的集合预报效果受模式本身误差的影响，在完美模式的假设下，LAF集合预报相对于控制试验的技巧水平20～40％。     

Aircraft Observations of Sea-Surface Turbulent Fluxes Near the California Coast

Aircraft turbulence data from the Autonomous Ocean Sampling Network project were analyzed and compared to the Coupled Ocean–Atmosphere Response Experiment (COARE) bulk parametrization of turbulent fluxes in an ocean area near the coast of California characterized by complex atmospheric flow. Turbulent fluxes measured at about 35 m above the sea surface using the eddy-correlation method were lower than bulk estimates under unstable and stable atmospheric stratification for all but light winds. Neutral turbulent transfer coefficients were used in this comparison because they remove the effects of mean atmospheric conditions and atmospheric stability. Spectral analysis suggested that kilometre-scale longitudinal rolls affect significantly turbulence measurements even near the sea surface, depending on sampling direction. Cross-wind sampling tended to capture all the available turbulent energy. Vertical soundings showed low boundary-layer depths and high flux divergence near the sea surface in the case of sensible heat flux but minimal flux divergence for the momentum flux. Cross-wind sampling and flux divergence were found to explain most of the observed discrepancies between the measured and bulk flux estimates. At low wind speeds the drag coefficient determined with eddy correlation and an inertial dissipation method after corrections were applied still showed high values compared to bulk estimates. This discrepancy correlated with the dominance of sea swell, which was a usually observed condition under low wind speeds. Under stable atmospheric conditions measured sensible heat fluxes, which usually have low values over the ocean, were possibly affected by measurement errors and deviated significantly from bulk estimates.     

贵州春季冰雹天气过程个例分析

利用天气形势及各种物理量值、卫星云图和多普勒雷达资料,分析了2009年4月11日傍晚到夜间发生在贵州省中部、西部地区的冰雹天气过程成因,结果发现:高原东移低涡是这次过程的主要影响系统;高层冷平流、低层暖平流,增强了气层的不稳定性;0℃层高度(600 hPa)和-20℃层高度(400 hPa)有利于冰雹生长.强对流天气发...     

Trace Metal Solid State Speciation in Aerosols of the Northern Levantine Basin,East Mediterranean

An established three stage sequential leach scheme was applied to a series of selected high volume aerosol samples (n = 35) collected from the Turkish Eastern Mediterranean coastline (Erdemli). Samples were selected according to their air mass back trajectory history to reflect the contrasting mixtures of aerosol material present in the Eastern Mediterranean marine aerosol. Two populations were adopted, those samples which were classed as “anthropogenic” and those which were “Saharan” dominated aerosol populations. Applying the three stage leach it was possible to define the proportion for each of the considered metals (Al, Fe, Cu, Pb, Cd, Zn and Mn) present in the (a) “exchangeable” (b) “carbonate / oxide” and (c) “refractory” phases, representing novel solid state aerosol speciation data for this marine system. Clear trends were established, conforming with data from previous studies with mainly crustal derived metals (Al and Fe) being present in the refractory phases (Al > 88%; Fe > 84%) and those influenced by anthropogenic sources being dominating in the exchangeable phase, although for these metals the variability was comparatively high (12–64%; 19–85%; 40–100% for Zn, Pb and Cd, respectively). For the majority, greater exchangeable fractions were present the lower the crustal source contribution to the aerosol population, whereas the “refractory” fraction exhibited contrasting behaviour. This was illustrated by the novel application of the mixing diagram, presenting each of the three speciation stages against the corresponding percent anthropogenic contribution to each collected sample. Zn, Pb and Cd all illustrated progressive decrease in the percent exchangeable with increasing crustal contribution to the aerosol population. The percent exchangeable was discussed in terms of its use to represent the upper limit of the bioavailable fraction of metal associated with the aerosol, post deposition. The mixing diagram approach enabled the prediction of the residual fractions for Cd, Pb and Zn (41 ± 4%; 62 ± 4% and 82 ± 5%, respectively,) in Saharan end-member material.     

笛卡儿坐标系的双多普勒天气雷达三维风场反演技术

文中研究了笛卡尔坐标系下双多普勒天气雷达三维风场反演技术 ,提出了包括雷达原始资料的预处理 ,空间插值以及可靠性检验的新方法 ,提高了反演结果的可信度和精确度。使用模拟的双多普勒雷达体扫资料进行了反演试验 ,结果表明 :本文的方法能够比较真实地反映风场的三维结构 ,可以用于真实风场的反演。     

正、斜压流场演变及相互转换所伴随的偶极型阻塞生命史

将阻塞过程中的大气运动流场分解为正,斜压流场,研究了它们在乌拉尔山偶极型阻塞个例中的演变特征。揭示了正、斜压流场的演变及相互转换所源发的阻塞生命史的全过程。     

双差分激光雷达——一组可以提高臭氧测量精度的波长

模拟了气溶胶影响三波长双差分 (2 6 6 - 2 89- 30 8nm)方法和双波长差分 (2 6 6 - 2 89nm和 2 6 6 - 30 8nm)方法测量对流层臭氧的误差 ,并在合肥测量了对流层 2～ 3.6km高度的臭氧分布。结果表明 ,三波长双差分方法比常规的双波长差分方法能更有效地克服气溶胶的影响 ,三波长差分测量的结果比常规的双波长差分的结果更精确。同时还揭示了气溶胶影响双波长差分方法测量臭氧的规律。模拟结论与测量结果是一致的