Frontal Line Research Articles

The Role of Low-Level Convergence and Latent Heating in a Simulation of Observed Squall Line Formation

Abstract The effects of mesoscale forcing and diabatic heating on the development of convective systems have been investigated using a simplified numerical model to simulate the squall line and the convective system preceding it that occurred over Texas and Oklahoma on 10– 11 April 1979. A simulation run without including latent but showed both systems to be initiated and maintained by convergence produced by larger-scale forcing. The first cloud system formed downwind of the convergence zone that was produced by the confluence of airstreams along a dryline. A cloud front approaching from the west then merged with this dryline, destroying its horizontal gradients through diffusive effects and replacing it with a frontal convergence line that was alinged with the low-level flow. This new configuration was then favorable for the formation of the squall line that developed in the simulation. When latent heat was included the continuous cloud in the first convective system broke down into isolated cells which...

The 11.9‐GHz rain attenuation and site diversity effect on the earth‐space paths of low elevation angles

In order to study rain attenuation characteristics and site diversity effects on earth‐space paths of elevation angles lower than 10°, sky noise measurements by radiometers at 11.9 GHz and 1‐min rain rate observation were conducted with several site diversity configurations in the western part of Japan. Measured statistics such as the cumulative distributions of 11.9‐GHz single‐site rain attenuation and related joint probabilities at diversity sites are presented. It is shown that extensively spread rain regions associated with typhoons or frontal lines have considerable effect on both rain attenuation and site diversity distributions. As a guide to prediction of site diversity effects for low elevation angle conditions, joint probability of rain attenuation as a function of site spacing from 17 to about 200 km is derived from the measurement results. Also shown is the site diversity effect dependence on elevation angle.

The Role of an Apparent Mesoscale Frontogenetic Circulation in Squall Line Initiation

The present investigation is concerned with the nature and apparent origin of a mesoscale clear zone and associated frontal line convection (a line of cumulus congestus clouds along an intensifying cold front) which appeared just prior to the explosive development of a line of severe thunderstorms at the cold front. It is pointed out that the clear zone formed immediately behind the cold front in southeastern Kansas and northeastern Oklahoma during the afternoon of April 16, 1982. Sequential displays of GOES-East satellite imagery are considered. The mechanism which seems to explain best the observations is a thermally direct frontogenetic circulation resulting from the combined effects of the synoptic-scale wind deformation field and mesoscale differential sensible heating.

Whole Body Computerized Tomography: Practical Image Analysis

This brief text is an excellent primer on body computed tomography (CT), primarily for the nonradiologist with an interest in body CT. The first section is a brief, comprehensible treatise on the basic mechanics of CT. Next is an anatomic outline with normal CT images of the chest and abdomen accompanied on each page by a frontal line drawing of the major vessels and viscera, which is a very useful reference guide for the level of the CT section. Matching anatomic drawings of each CT image are well labeled. However, the accompanying key to the anatomy uses Latin terminology, which may be slightly confusing for American readers. Several sections then follow on technical details. Computed tomographic techniques are somewhat dogmatically presented, leaving little room for variation or innovation. The remainder of the book is devoted to specific anatomic areas with several well-demonstrated examples of important pathological processes for each area.

Detecting Temperature Fine Structure and Mesoscale Frontal Regimes along Line P in the Northeastern Pacific Ocean

Temperature observations obtained at 13 line P stations by Canadian weatherships for the period 1969–1977 show evidence for two quasi-permanent mesoscale frontal regimes west of Vancouver Island, British Columbia. Findings are based on vertically smoothed digitized STD profiles and normalized variances for temperature fine structure having vertical scales of a few tens of metres. A major frontal boundary crosses line P in the vicinity of 128°40′W longitude to depths of 700 m and in the vicinity of 130°40′W longitude between depths of 700 and 1300 m. Over certain depth ranges, location of the front varies seasonally, with a tendency for the front to be further offshore in winter than in summer. There is also some suggestion of a secondary, poorly defined frontal boundary in the region of 136–139°W longitude.Key words: ocean fronts, line P, northeast Pacific, temperature fine structure

Synoptic weather conditions inducing long‐distance immigration of planthoppers, Sogatella furcifera Horvath and Nilaparvata lugens Stal

Abstract Adults and nymphs of Sogatella furcifera and Nilaparvata lugens are serious pests of growing rice in Japan. They appear in June and July but their origin was unknown. Inflow of warm and humid air from the south was shown to favour the appearance of planthoppers. The air inflow was associated with the passage of depressions along the frontal zone, called Bai‐u in the Far East. Immigrations were categorized as mass or minor according to the density of immigrants surveyed by various traps. The mass immigrations were induced by the passage of depressions which emerged in the central part of the Chinese continent between 25 °N and 35 °N and proceeded eastwards between the observation point and about 600 km north. Warm and humid south west winds blew, on average, for 19.3 h at an average wind speed of 32.9 km/h. When the route digressed a little north or south, minor immigrations, with only S.furcifera in half the cases, occurred. Minor immigration types were categorized into a long‐lasting type which appeared in the final stage of the rainy season, a mass immigration typemodified by the location of a typhoon in the south, and a minor type near the frontal line occurring without the passage of recognizable depressions. The greatest aerial densities of immigrants were estimated as three to seven per 103m3 in S.furcifera and one to two per 103 m3 in N.Iugens. Female immigrants were mostly unmated. All the depressions that appeared in June and July 1967–72 were analysed and twenty‐nine (76.3%) out of thirty‐eight originating in the central part of the Chinese continent, caused immigrations. Yearly fluctuations of planthopper infestations in Japan were shown to depend on the yearly fluctuations of the route of depressions associated with the migration of the planthoppers.

THE MECHANICS OF INSTABILITY-LINE FORMATION

Abstract It is proposed that under certain conditions of wind flow that temperature changes due to horizontal advection and vertical motion produce a trend towards the formation within a few hours of a line or narrow band of vertical thermal instability associated with a marked increase in low-level convergence along the same line or narrow band. An assumed distribution of winds, chosen to represent typical conditions observed preceding by a few hours the formation of an instability line, is studied and a model presented. The model agrees well with synoptic observation and studies. The atmospheric mechanism derived is of the mesoscale and is directly applicable to instability line formation in the “High Plains” and most pre-cold frontal instability lines in other areas can be explained by it.

空電源の位置觀測と気象現象との關係について

We made some improvement in the point of bearing accuracy of the cathoderay direction-finders.We equipped them at three observation stations several hundred kilometres apart in the Japan Islands, and made simultaneous direction observation. With the internal consistency of the bearing taken on atmospherics, the errors in direction-finding are found to be less than ±1 degree in almost all cases. So within the radius of 3000km, we can locate atmospherics with the sufficient accuracy to correlate with the results of the synoptic weather analysis. The results newly obtained in the summer and the autumn in 1951 are as follows:1. Over the tropical and subtropical region of the Pacific, especially in summer and autumn, a large number of atmospherics are produced by disturbances due to easterly waves, and their percentage is comparable to that of atmospherics produced by heat-thunderstorms in Southeast Asia, for instance, Philippine Islands, Indo-China, etc..2. When the long frontal line is produced over the Pacific by the outbreak of the polar continental air, its lower-latitude part often becomes stationary. In such a condition atmospherics are usually observed to be associated with this stationary front rather than with the other part of the front.3. Over the lower-latitude region of the Pacific, a young cyclone often produces atmospherics, occasionally accompanying violent lightning discharges in its center area and its warm front area.4. As for typhoons, atmospherics are observed in certain sectors of almost all typhoons in their both stages of immaturity and maturity. When they enter the stage of decay or dissipation by the effect of landing, no more atmospheri_??_s are observed in their active area.

A Synoptic Study of Instability Lines

An attempt is made to select a type series of constant-pressure charts associated with the life cycle of the pre-cold frontal instability line, especially over the southeastern States during the spring season. Emphasis is placed upon advective temperature changes that result in the development and maintenance of warm and cold tongues and the resultant elongated transitional zone in the fore part of the associated trough. The instability line develops along the axis of a warm tongue at 850 mb after cold air advection at 700 mb has reached the fore part of the associated trough and is advancing at a more rapid rate than the warm tongue.

大阪灣の津浪に就て(IV)

In this paper we have calculated the time duration in which a tunami wave travels through the whole course of the Kii Channel. We assumed that the initial position of the wave front of tunami is on the straight line connccting Siomisaki and Murotomisaki, and that it advances northwards holding straightness of its frontal line with the velocity √gh as the wave length of tunami is very large, where g is the gravity acceleration and h the mean deapth of the vertical section of the channel containing a frontal line. Then dividing the total course into 20 wave fronts as is shown in Fig. 1, and summing up the time elements which is given by where dx is the distance betwecn two adjacent frontal lines and H the mean of their h, we get the travel time as is shown in Fig. 2.On the other hand, we calculated numerically the travel time by means of the equations where f is the wave amplitude, V the velocity, S and b the sectional area and breadth of the channel respectively (Cf. our previons papers). In our case the initial condition is V=√gh0 and the period is 20 or 40 miniutes. The results are shown also in Fig. 2.As we see from Fig. 2, the travel time passing through the Kii Channel is just 60 minutes and the same for our three cases. We have seen in the previous papers that tunami requires 60 minutes to travel through the whole course of the Osaka Bay so that it takes just two hours from the entrance of the Kii Channel to the City of Osaka. This fact gives time enough to make a watcher at, say, Siomisaki to warn the city against the tunami.

A NEW (ORBITAL) METHOD FOR EXTIRPATION OF THE HYPOPHYSIS IN THE PIGEON

Pituitary gland extirpation has been performed by many investigators (Biedl, Aschner). In the course of an investigation on the effect of the pituitary gland upon body temperature in the pigeon we were often compelled to ablate the gland. The cranial method (dishing, Kreidl) was first tried in vain, then the palatine method (Caselli, Gaglio) proved also fruitless. We were thus driven to devise a new method by which the operation was carried out through the orbital cavity. The eye-ball on one side was enucleated and the intervening bone removed to give access to the mid-brain cavity to permit extirpation of the hypophysis. A skin incision was made about 2 cm. in length along the frontal line just over one eye, and the bone bordering the orbital cavity was exposed. The soft tissues surrounding the eye-ball were first cut away and the latter itself taken out after necessary ligatures.