scholarly journals Low-level inversion of the L component of pseudorabies virus is not dependent on sequence homology.

1991 ◽  
Vol 65 (12) ◽  
pp. 7016-7019 ◽  
Author(s):  
G F Rall ◽  
S Kupershmidt ◽  
X Q Lu ◽  
T C Mettenleiter ◽  
T Ben-Porat
Keyword(s):  
Sequence Homology ◽  
Pseudorabies Virus ◽  
Low Level ◽  
Level Inversion

The Breakdown of a Low-level Inversion Studied by Means of Detailed Soundings with a Modified Radiosonde

1952 ◽  
Vol 33 (9) ◽  
pp. 373-379 ◽  
Author(s):  
Frank Gifford
Keyword(s):  
Minimum Temperature ◽  
Low Level ◽  
Short Series ◽  
Pilot Balloon ◽  
Level Inversion

A short series of unusually detailed temperature, humidity, and wind soundings to a height of about 750 mb., made at Silver Hill, Md. on the night of October 30th and 31st, 1950, and consisting of eight flights of specially modified radiosondes and 26 double-theodolite pilot balloon runs, is presented. The nocturnal breakdown of the ground inversion with steep wind gradients, a phenomenon first remarked by Durst in 1933, is here observed apparently to be associated with the sudden lowering of an upper (turbulence or subsidence) inversion. Alternative explanations for this are advanced, and implications for minimum temperature and stratus forecasting noted. The accuracy of the observations is discussed.

Effects of Inversion Height and Surface Heat Flux on Downslope Windstorms

2011 ◽  
Vol 139 (12) ◽  
pp. 3750-3764 ◽  
Author(s):  
Craig M. Smith ◽  
Eric D. Skyllingstad
Keyword(s):  
Vertical Displacement ◽  
Falkland Islands ◽  
Similar Response ◽  
Surface Cooling ◽  
Low Level ◽  
Jet Length ◽  
Downslope Winds ◽  
Downslope Wind ◽  
Downslope Windstorms ◽  
Level Inversion

Abstract Simulations are presented focusing on the role of temperature inversions in controlling the formation and strength of downslope wind storms. Three mechanisms are examined depending on the relative height of the inversion with respect to the mountain and the stability of vertically propagating mountain waves. For low-level inversions, flows are generated that closely resemble a reduced gravity shallow water hydraulic response with a large vertical displacement of the inversion on the lee side of the mountain. For higher-level inversion cases, simulated flows more closely followed a stratified hydraulic behavior with the inversion acting as a rigid reflective lid. In the third mechanism, downslope winds were forced by a self-induced critical layer located below the inversion height. The presence of the inversion in this case had little effect on the resulting downslope winds. Observations made on the Falkland Islands show that downslope windstorms may preferentially occur in early morning even without synoptic-scale changes in atmospheric structure. Most windstorms on the Falkland Islands generally have a short jet length; rare, longer jet length storms typically occur in conjunction with a strong low-level inversion. Idealized numerical experiments tend to produce a similar response depending on the presence of strong low-level inversion and surface cooling. Results suggest that surface heating can have significant control on the flow response by reducing the low-level inversion strength, or by changing the stratification and wind velocity below the inversion, thereby preventing a strong downslope windstorm.

scholarly journals An account of fog over Chennai

MAUSAM ◽  
2021 ◽  
Vol 58 (4) ◽  
pp. 501-512
Author(s):  
R. SURESH ◽  
M. V. JANAKIRAMAYYA ◽  
E. R. SUKUMAR
Keyword(s):  
High Concentration ◽  
Industrial Growth ◽  
Low Level ◽  
The Past ◽  
Surface Inversion ◽  
Weather Observations ◽  
Annual Frequency ◽  
Nocturnal Inversion ◽  
Good Number ◽  
Level Inversion

Climatologically (based on 1951-1980) the annual fog frequency of Chennai airport is 4.3 days. But, the operational aviation meteorological forecasters often experienced more number of foggy days during the past decade. Hence the fog frequency has been critically analysed based on current weather observations made by aerodrome meteorological office, Chennai during 1981-2002 (barring 1984 for which data is not readily available). It has been found that the annual frequency based on the present study has shot up to 21.5 days. The most favourable period for fog over Chennai airport has been identified as January followed by February and March. The formation of fog has been mostly observed during 0000-0200 UTC although in good number of cases it was during 2200-2400 UTC. The most common duration of fog is 60-120 minutes albeit duration as high as 540-570 minutes are also probable. The low level (surface) nocturnal inversion frequency has alarmingly increased during 1990s and the inversion is almost a day-to-day phenomenon during 2000s. Rapid urbanisation, vehicular traffic and industrial growth could be the cause for the increased  atmospheric pollution which has  increased the nocturnal stability conditions as well the fog frequency. Visibility as low as zero had been recorded on a number of cases and their causes  have been analysed. Neutral or absolutely unstable stratification at 1200 UTC coupled with high relative humidity and high concentration of pollution cause the fog to form from 2200 UTC onwards and the nocturnal surface inversion / isotherm at 0000 UTC maintains the fog. Though the low level inversion maintains the fog once it is formed already, inversion alone is not a sufficient condition for the formation of fog.

scholarly journals A simple thermodynamical model to estimate the rate of depletion of nocturnal low level inversion layer

MAUSAM ◽  
2021 ◽  
Vol 51 (1) ◽  
pp. 39-46
Author(s):  
R. SURESH
Keyword(s):  
Inversion Layer ◽  
Global Radiation ◽  
Vertical Mixing ◽  
Dispersion Models ◽  
Vertical Temperature Profile ◽  
Low Level ◽  
Inversion Strength ◽  
The Stability ◽  
Level Inversion ◽  
Thermodynamical Model

The low level inversion, be it that of ground based or elevated, plays a significant role in the dispersion of polluted particles and in aviation meteorology. The rate of rise of the ground based inversion top and the base of elevated inversion causes the decrease of inversion strength and thereby permits vertical mixing of pollutants as the stability of the atmosphere is reduced. A simple thermodynamical model using the global radiation and vertical temperature profile has been proposed to estimate the rate of rise of (i) the ground based inversion top and (ii) the base of the elevated inversion. The depth of inversion thus estimated can be used in the pollution/fog dispersion models. The model is simple and operationally practicable. The limitations of the model are also discussed.

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