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正1降雪天气的观测和记录降雪时,如果是雪随降随化,那么按照普通降水进行处理,则立即将自动站雨量传感器的承水器进行加盖,并将人工观测降水量的雨量筒和储水瓶取下以便进行承接降雪。由于加盖之前承水器有滞留的降雪,会使自动站有小时降水量出现,在此时间段内自动站降水量应按照缺测处理,并用人工观测的降水量发报,而加盖的时间和操作记录应该详加备注。如果地面的三支温度表被降雪覆盖,那么在降雪停止以后应小心的将温度表从雪中取出来,使温 相似文献
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自 2 0 0 1年 6月 1日起 ,一级辐射站推广使用了“ＦＳＣ - 1型辐射数据采集处理仪” ,仪器运行情况良好 ,但如果要处理特殊情况 ,必须避开数据采集更新时刻。例如 :强降水时要保护辐射表 ,先点击计算机屏幕上的“传感器加盖”框 ,框内显示“∨” ,再把 5只辐射表加盖 ,屏幕显示 5个值为零。当雨小时辐射表去盖开始正常采集 ,再点击计算机屏幕上的“传感器加盖”框 ,框内“∨”消失 ,一分钟后 5只辐射表 (总表、散表、直表、反表、净表 )显示正常值。若在数据采集更新时刻的前 3秒钟内进行上述操作 ,会因时间不够而造成数据丢失或记录不正常… 相似文献
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大棚蔬菜最低气温预报及冻害防御技术 总被引：2，自引：0，他引：2
在大棚蔬菜低温冻害防御中,通过搭建拱棚加盖不同层塑料内膜的大棚温度调控模式应用广泛。通过对不同层塑料内膜覆盖的大棚小气候环境温度观测,分析了棚内外日最低气温的相关关系,建立了棚内小气候环境日最低气温的一元线性回归预测模型,应用气象台天气预报中的日最低气温预报开展了大棚小气候环境的日最低气温预报,根据预报结果和蔬菜冻害指标,确定大棚增温防冻需要加盖塑料内膜的层数,提出大棚蔬菜内膜覆盖方式的冻害防御对策,为设施农业提供安全生产保障依据。 相似文献
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本文利用一个10层中尺度湿模式，对长江流域的一次梅雨暴雨进行数值模拟。结果如下:1. 梅雨暴雨系统中有θse暖盖存在，并在降水过程中维持加强。它与美国中西部强风暴暴雨系统中的干暖盖不同，是湿暖盖。2．降水多发生在暖盖北侧或东北侧、θse水平梯度大的地区，该地区还处于850—700百帕层的位势不稳定中心和强上升区重叠处附近。3．暖盖的作用除了可抑制其下层（边界层）位势不稳定能量的随时释放外，还起到增强其上层（对流层中低层）位势不稳定度的作用，因而暖盖在暴雨过程中提供了有利于深厚积云对流发生发展的热力环境条件。4．从对热成风涡度方程的讨论可知，暴雨多出现在暖盖上层的位势不稳定中心区和强上升区附近，是由于该处的位势不稳定度及其水平分布不均匀性和上升速度及其水平分布不均匀性的互相耦合，造成热成风不平衡，引起抽气式垂直环流的发生发展，并引起重力惯性波的不稳定之故，所以暖盖还对大气不平衡状态的发展起促进作用。 5．由暖盖的个别变化方程可知，暖盖生成的决定性因子是地转热成风（Vg/p）对水汽的平流和热成风不平衡（v’/ p）引起的θse平流。因此雨区南侧低空偏南湿急流的存在对雨区暖盖的增强极为有利。 相似文献
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冬季欧亚大陆雪盖与江苏梅雨量关系的初探 总被引：2，自引：0，他引：2
本文着重讨论了冬季欧亚大陆雪盖与江苏梅雨量的年际变化关系。分析发现：冬季欧亚大陆雪盖与江苏梅雨量之间呈显著的负相关，而与沿江地区夏季降水量之间的关系不密切。异常的雪盖对江苏丰、枯梅雨有很好的指示意义。 相似文献
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湖南强风暴暖盖环境场研究 总被引：3，自引：1，他引：3
本文通过对湘中、湘北地区42次强风暴资料的分析,建立了一个强风暴环境场的天气学模式,着重讨论了暖盖(即对流层中下层的逆温层)的形成和维持机理. 暖盖是由于绕过青藏高原两侧的两支西风波动相互作用而产生的.它的存在有利于低空急流在其东部边缘的低空加强,而低空急流引起的垂直环流反过来又有利于暖盖的维持,当暖盖下降到低空急流轴附近时因受扰动而破坏,引起强风暴的发生. 相似文献
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Stratocumulus-capped mixed layers derived from a three-dimensional model 总被引：22，自引：7，他引：22
James W. Deardorff 《Boundary-Layer Meteorology》1980,18(4):495-527
Results of a three-dimensional numerical model are analysed in a study of turbulence and entrainment within mixed layers containing stratocumulus with or without parameterized cloud-top radiative cooling. The model eliminates most of the assumptions invoked in theories of cloud-capped mixed layers, but suffers disadvantages which include poor resolution and large truncation errors in and above the capping inversion.For relatively thick mixed layers with relatively thick capping inversions, the cloud-top radiative cooling is found to be lodged mostly within the capping inversion when the cooling is confined locally to the upper 50 m or less of the cloud. It does not then contribute substantially towards increased buoyancy flux and turbulence within the well mixed layer just below.The optimal means of correlating the entrainment rate, or mixed-layer growth rate, for mixed layers of variable amounts of stratocumulus is found to be through functional dependence upon an overall jump Richardson number, utilizing as scaling velocity the standard deviation of vertical velocity existing at the top of the mixed layer (near the center of the capping inversion). This velocity is found to be a fraction of the generalized convective velocity for the mixed layer as a whole which is greater for cloud-capped mixed layers than for clear mixed layers. 相似文献
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A marine stratocumulus model has been developed which has four major sub-models: (1) a one-dimensional version of the CSU cumulus model, (2) a partially-diagnostic higher-order turbulence model, (3) an atmospheric radiation model for both short-wave and long-wave radiation, and (4) a partial condensation scheme and cloud fractional parameterization. A set of numerical experiments have been performed to study the interactions among the turbulence, the long-wave radiation, the short-wave radiation, and the sub-grid condensation processes. The results indicate that surface sensible eddy heat flux and not radiative cooling is the major control on the rate of cloud-top entrainment. Cloud-top radiation cooling occurs principally within the upper part of the mixed layer. However, for the stratocumulus with numerous towers penetrated into the capping inversion, most of the long-wave radiation occurs within the capping inversion. It is found that cloud-top radiation cooling is balanced by turbulence transport of sensible heat from cloud-base levels. 相似文献
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Parameterization for the depth of the entrainment zone above the convectively mixed layer 总被引：1，自引：0，他引：1
It has been noted that when the convective Richardson number Ri* is used to characterize the depth of the entrainment zone, various parameterization schemes can be obtained. This situation is often attributed to the invalidity of parcel theory. However, evidence shows that the convective Richardson number Ri^* might be an improper characteristic scaling parameter for the entrainment process. An attempt to use an innovative parameter to parameterize the entrainment-zone thickness has been made in this paper.Based on the examination of the data of water-tank experiments and atmospheric measurements, it is found that the total lapse rate of potential temperature across the entrainment zone is proportional to that of the capping inversion layer. Inserting this relationship into the so-called parcel theory, it thus gives a new parameterization scheme for the depth of the entrainment zone. This scheme includes the lapse rate of the capping inversion layer that plays an important role in the entrainment process. Its physical representation is reasonable. The new scheme gives a better ordering of the data measured in both watertank and atmosphere as compared with the traditional method using Ri^*. These indicate that the parcel theory can describe the entrainment process suitably and that the new parameter is better than Ri^*. 相似文献
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Three aircraft-based studies of boundary-layer fronts (BLFs) werecarried out during the experiment KABEG in April 1997near the sea-ice edge over the Davis Strait. The zone of strongestcross-front horizontal gradients showed a typical length scaleof 20 km, while the along-front scale was observed to beseveral hundreds of kilometres.The observed BLFs were stronger than the few previously reportedcases. Horizontal gradients of potential temperature and specifichumidity ranged up to 3 K or 0.25 g kg-1over 20 km, respectively.Low-level winds were around 15 m s-1 parallel to the ice edge.The capping inversion sloped from between250 and 400 m over sea ice to between 400 and 700 m over ocean.For two BLF cases turbulent fluxes and energy budgets are calculated.Turbulent energy fluxes show a factor 2 to 3 contrast acrossthe ice edge and range from 15 to 50 W m-2 over sea iceand from 50 to 100 W m-1 over open ocean.The mean boundary-layer energy budgets are dominated bycold, dry horizontal advection, which is exceededby vertical heat flux convergence.The momentum budgets are dominated by pressure gradient force,Coriolis force and momentum flux divergence. 相似文献
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Boundary-layer measurements made from the Swedish icebreaker Oden during the Arctic Ocean Experiment 2001 (AOE-2001) are analysed. They refer mainly to ice drift in the central Arctic during
the period 2–21 August 2001. On board Oden a remote sensing array with a wind profiler, cloud radar and a scanning microwave radiometer, and a regular weather station
operated continuously; soundings were also released during research stations. Turbulence and profile measurements on an 18-m
mast were deployed on the ice, along with two sodar systems, a microbarograph array and a tethered sounding system. Surface
flux and meteorological stations were also deployed on nearby ice floes. There is a clear diurnal cycle in radiation and also
in wind speed, cloud base and visibility. It is absent in temperature and humidity, probably due to the very strong control
by melting/ freezing ice and snow. In the advection of warm air, latent heat of melting maintains the surface temperature
at 0 °C, while with a negative energy balance the latent heat of freezing of the salty ocean water acts to maintain the surface
temperature > −2 °C. The constant presence of water at the surface maintains a relative humidity close to 100%, and this is
also often facilitated by an increasing specific humidity through the capping inversion, making entrainment a moisture source.
This ensures cloudy conditions, with low cloud and fog prevailing most of the time. Intrusions of warm and moist air from
beyond the ice edge are frequent, but the local Arctic boundary layer remains at a relatively constant temperature, and is
shallow and well mixed with strong capping inversions. Power spectra of surface-layer wind speed sometimes show large variance
at low frequency. A scanning radiometer provides a monitoring of the vertical thermal structure with a spatial and temporal
resolution not seen before in the Arctic. There are often two inversions, an elevated main inversion and a weak surface inversion,
and occasionally additional inversions occur. Enhanced entrainment across the main inversion appears to occur during frontal
passages. Variance of the scanning radiometer temperatures occurs in large pulses rather than varying smoothly, and the height
to the maximum variance appears to be a reasonable proxy for the boundary-layer depth. 相似文献
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Instability of resonant trapped gravity waves is proposed as the mechanism responsible for the creation of turbulent patches in the inversion capping a well developed convective layer. The plume circulation of the convective layer results in a periodic forcing at the base of the inversion layer; trapped gravity waves in resonance with such forcing are considered. Good agreement with experimental results is obtained.Now at the Istituto di Fisica della Università di Urbino Via S. Chiara 61100 Urbino (Ps.) Italy. 相似文献
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The Influence of Thermal Effects on the Wind Speed Profile of the Coastal Marine Boundary Layer 总被引：1，自引：3，他引：1
Bernhard Lange Søren Larsen Jørgen Højstrup Rebecca Barthelmie 《Boundary-Layer Meteorology》2004,112(3):587-617
The wind speed profile in a coastal marine environment is investigated with observations from the measurement program Rødsand, where meteorological data are collected with a 50 m high mast in the Danish Baltic Sea, about 11 km from the coast. When compared with the standard Monin—Obukhov theory the measured wind speed increase between 10 m and 50 m height is found to be systematically larger than predicted for stable and near-neutral conditions. The data indicate that the deviation is smaller for short (10–20 km) distances to the coast than for larger (>30 km) distances. The theory of the planetary boundary layer with an inversion lid offers a qualitative explanation for these findings. When warm air is advected over colder water, a capping inversion typically develops. The air below is constantly cooled by the water and gradually develops into a well-mixed layer with near-neutral stratification. Typical examples as well as scatter plots of the data are consistent with this explanation. The deviation of measured and predicted wind speed profiles is shown to be correlated with the estimated height and strength of the inversion layer. 相似文献
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In this work, we study the characteristics of a stably stratifiedatmospheric boundary layer using large-eddy simulation (LES).In order to simulate the stable planetary boundary layer, wedeveloped a modified version of the two-part subgrid-scalemodel of Sullivan et al. This improved version of themodel is used to simulate a highly cooled yet fairly windy stableboundary layer with a surface heat flux of(W)o = -0.05 m K s-1and a geostrophic wind speed of Ug = 15 m s-1.Flow visualization and evaluation of the turbulencestatistics from this case reveal the development ofa continuously turbulent boundary layer with small-scalestructures. The stability of the boundary layercoupled with the presence of a strong capping inversionresults in the development of a dominant gravity wave atthe top of the stable boundary layer that appears to be relatedto the most unstable wave predicted by the Taylor–Goldsteinequation. As a result of the decay of turbulence aloft,a strong-low level jet forms above the boundary layer.The time dependent behaviour of the jet is compared with Blackadar'sinertial oscillation analysis. 相似文献
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Summertime Mixing Heights At Vienna, Austria, Estimated from Vertical Soundings and by a Numerical Model 总被引：1，自引：1，他引：0
Martin Piringer 《Boundary-Layer Meteorology》1998,89(1):25-45
Mixing heights calculated by the Danish OML meteorological pre-processor are compared to those diagnosed from radio- and tether-sonde vertical potential temperature profiles. All methods give reliable estimates of noon mixing heights deduced from radiosoundings, especially when the boundary layer is fully convective. Differences are larger during convective conditions without a well-defined capping inversion in the radiosonde potential temperature profile or when OML calculates a mechanical mixing height. The OML model is also able to calculate the daily course of the mixing height as expected. The tethersonde-derived mixing heights are especially valuable during the morning rise of the elevated inversion. Modifications to all three methods to improve mixing-height predictions are discussed. 相似文献