Gustiness of the Novorossiysk bora

The development of the Novorossiysk bora on February 5–6, 2010 is simulated with high spatial and temporal resolution using the regional model of atmospheric circulation. Considered are typical features of the wind speed and air temperature fields. Singled out are two regimes defining the type of the air flowing around the mountain ridge and the temporal variability (gustiness) of the surface wind speed.     

A numerical study of the effects of synoptic baroclinicity on stable boundary-layer evolution

The effects of synoptic baroclinicity on the evolution of the stable boundary layer are studied by using a numerical model in which the eddy exchange coefficients are determined from the turbulent kinetic energy and a local turbulent length scale. For model verification, several barotropic simulations are compared with those of higher-order closure models. The model predicts the existence of a value of geostrophic wind shear at which the nocturnal jet reaches its maximum intensity. The mechanism by which ageostrophic flow is generated and the role it plays in the development of the jet are explored. As baroclinicity increases, the directional shear in the wind near the level of the jet increases, thereby allowing the nocturnal inversion to grow to levels well above that of the jet.Journal Paper No. J-11109 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project 2521.     

Numerical Simulation of the Novaya Zemlya Bora

The development of the bora in case of strong southeastern wind in the area of Novaya Zemlya in the winter-spring of 2016 is simulated using the WRF-ARW numerical atmosphere circulation model with high spatial resolution. The features of wind speed and air temperature fields are considered which define the formation of the intensive near-surface flow, the bora, over the lee western slope of the mountain range. It is demonstrated that the bora development leads to the air temperature rise over the eastern part of the Barents Sea, to the increased surface heat fluxes, and to the formation of the cloudless zone over the sea westward of Novaya Zemlya. It was found that the main reason for the bora development is the high stability of the atmospheric boundary layer over the Kara Sea. It is shown that in case of western wind the Novaya Zemlya archipelago does not exert considerable influence on the air exchange in the Kara Sea area.     

Effects of air masses and synoptic weather on aerosol formation in the continental boundary layer

Nucleation of near nm sized aerosol particles and subsequent growth to ∼100 nm in 1–2 days has in recent years been frequently observed in the continental boundary layer at several European locations. In 1998–99, this was the focus of the BIOFOR experiment in Hyytiälä in the boreal Finnish forest. Nucleation occurred in arctic and to some extent in polar air masses, with a preference for maritime air in transition to continental air masses, and never in sub‐tropical air. The air masses originated north of the BIOFOR experiment by paths from the southwest to northeast sector. The nucleation was also associated with cold air advection behind cold fronts, never warm air advection. This may relate to low pre‐existing aerosol concentration, low cloudiness and large diurnal amplitudes in the continental boundary layer associated with cold air advection and clear skies. Arctic and polar air together with cold air advection did not always lead to nucleation. The most important limiting meteorological factors were cold front passages and high cloudiness, probably through reduced photochemistry and wet scavenging of precursor gases and new aerosol particles. The preference for nucleation to occur in arctic air masses, which seldom form in the summer, suggests a meteorological explanation for the annual cycle of nucleation, which has a minimum in summer. The connection to cold‐air outbreaks suggests that the maximum in nucleation events during spring and autumn may be explained by the larger latitudinal temperature gradients and higher cyclone activity at that time of the year. Nucleation was observed on the same days over large parts (1000‐km distance) of the same air mass. This suggests that the aerosol nucleation spans from the microphysical scale to the synoptic scale, perhaps connected through boundary layer and mesoscale processes.     

丹东附近海域海雾产生的条件及天气学预报方法

使用常规气象观测资料和NOAA-17,EOS/ODIS卫星遥感影像资料,应用个例分析与合成分析相结合的方法,分析了2001～2005年37个海雾个例,揭示了丹东附近海域海雾的变化规律和海雾形成期间的大气、海洋背景条件,研制出了天气学预报方法并对其预报能力进行了检验。     

副热带天气尺度系统短期演变的泛准地转机理

在 Rossbs数λ《1的情况下,如果在大范围降水区域中潜热增温率大于温度平流,或者因热力对流引起的动量铅直传递大于动量平流,都能使运动偏离准地转状态。散度场和垂直速度场都比准地转情况下强。但除少数极端情况外,涡度场仍是准地转的。基于这一点,关于西风带天气系统准地转演变的一些基本原理也适用于一般副热带场合。本文论证了上述观点,提出泛准地转演变的概念。并给出一种能够清晰、简洁地表述泛准地转演变中各种扰源制约场变化的一般规律近似解析解。特别讨论了水汽潜热和涡度的对流铅直传递在其中的地位。     

Dynamical aspects of ozone mini-hole formation

Summary A case study and statistical evaluations provide evidence that so-called ozone mini-hole events over Europe, where a rapid drop of total ozone is followed by complete recovery after a few days, are due to the northeascward motion of patches of air with low total ozone content. These patches appear to originate in subtropical latitudes. They correlate well with minima of potential vorticity near the tropopause. Contour dynamics is invoked to explain some basic features of the deformation and northward motion of the mini-holes as well as the related large-scale flow structures.     

Frontogenesis, evolution and the time scale of front formation

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A synoptic parameterization of the drag coefficient

Abstract

The problem areas affecting the evaluation of hail suppression experiments are reviewed. These include the hail sensors and networks, trop damage data, statistical analysis, the hail‐suppression hypothesis, and the technology of cloud seeding. General directions of needed research are proposed.     

Meteorological aspects of an abnormal cooling event over Iran in April 2009

During the period from 12 to 15 April, 2009 nearly the entire Iran, apart from the southern border, experienced an advective cooling event. While winter freezing concerns are typical, the nature of this freezing event was unusual with respect to its date of occurrence and accompanying synoptic meteorological situation. To analyze the freezing event, the relevant meteorological data at multiple levels of the atmosphere were examined from the NCEP/NCAR reanalysis dataset. The results showed that a polar vortex was responsible for the freezing event over the country extending southward extraordinarily in such a way that its ridge influenced most parts of Iran. This was recognized as an abnormal extension of a polar vortex in the recent years. The sea-level pressure fields indicated that a ridge of large-scale anticyclone centered over Black Sea extended southward and prevailed over most parts of Iran. This resulted in the formation of a severe cold air advection from high latitudes (Polar region) over Iran. During the study period, moisture pumping was observed from the Arabian Sea and Persian Gulf. The winds at 1000 hPa level blew with a magnitude of 10 m s^?1 toward south in the region of convergence (between ?2 × 10^?6 s^?1 and ?12 × 10^?6 s^?1). The vertical profiles of temperature and humidity also indicated that the ICE structural icing occurred at multiple levels of the atmosphere, i.e, from 800 hPa through 400 hPa levels. In addition to the carburetor (or induction), icing occurred between 900 and 700 hPa levels in the selected radiosonde stations during the study period. In addition, the HYSPLIT backward trajectory model outputs were in quite good agreement with the observed synoptic features.     

Characteristics of sea breeze front development with various synoptic conditions and its impact on lower troposphere ozone formation

To examine the correlation between the sizes of sea breeze fronts and pollutants under the influence of synoptic fields, a numerical simulation was conducted in the southeast coastal area of the Korean Peninsula, where relatively high concentrations of pollutants occur because of the presence of various kinds of industrial developments. Sea breeze and sea breeze front days during the period 2005-09 were identified using wind profiler data and, according to the results, the number of days were 72 and 53, respectively. When synoptic forcing was weak, sea breeze fronts moved fast both in horizontal fields and in terms of wind velocity, while in the case of strong synoptic forcing, sea breeze fronts remained at the coast or moved slowly due to strong opposing flows. In this case, the sea breeze front development function and horizontal potential temperature difference were larger than with weak synoptic forcing. The ozone concentration that moves together with sea breeze fronts was also formed along the frontal surfaces. Ozone advection and diffusion in the case of strong synoptic forcing was suppressed at the frontal surface and the concentration gradient was large. The vertical distribution of ozone was very low due to the Thermal Internal Boundary Layer (TIBL) being low.     

The synoptic meaning of helicity

Summary Helicity, a scalar quantity resulting from the inner product of velocity and vorticity, has until now mostly been used in the field of mesoscale meteorology and boundary layer meteorology. Goals of this paper are the derivation of the flux form of the helicity equation in general form without neglection of friction and Coriolis force and the examination of helicity patterns of larger scales. The general helicity equation is approximated for the synoptic and frontal scale by use of the scale analysis. High helicity values are bounded to fronts, such that helicity determines their positions. Finally the helicity patterns at different heights and helicity sources and sinks are discussed for a case study of a cyclogenesis over the Atlantic.With 6 Figures     

Dynamical aspects of katabatic wind evolution in the Antarctic coastal zone

The spatial evolution of katabatic winds along idealized slopes representative of Antarctic terrain is examined using a hydrostatic, two-dimensional primitive equation model with high resolution. A downslope momentum-forces analysis is made of simulations in which katabatic flow reaches steady state, with emphasis on physical mechanisms in the coastal zone. The importance of the reversal of the pressure gradient force in the coastal zone, causing the sudden decay of katabatic winds, is discussed.     

本刊编委简介

气象经济与气象经济学在经济社会中的作用越来越大,并越来越受到重视.通过分析气象与经济社会的关系,阐述气象经济学的涵义及其特性,并对其现状和问题进行分析,提出了构建气象经济学的支撑体系,展望了气象经济学的发展趋势.     

天气预报现代化的途径

当前华主席、党中央为我们指明了科学技术现代化的目标,要求我们能尽快地实现科学技术现代化。大气科学的中心任务是提高天气予报的准确度,天气予报的进展是整个大气科学发展的基础。因此怎样使我国的天气予报科学实现现代化,是我们气象工作者应该考虑的重要问题。本文想从近代天气予报科学的进展情况讨论一下这个问题。     

气象经济与气象经济学发展研究

气象经济与气象经济学在经济社会中的作用越来越大,并越来越受到重视.通过分析气象与经济社会的关系,阐述气象经济学的涵义及其特性,并对其现状和问题进行分析,提出了构建气象经济学的支撑体系,展望了气象经济学的发展趋势.