The nocturnal migration of the Australian plague locust, Chortoicetes terminifera (Walker) (Orthoptera: Acrididae): quantitative radar observations of a series of northward flights

1983 ◽  
Vol 73 (4) ◽  
pp. 567-585 ◽  
Author(s):  
V. A. Drake ◽  
R. A. Farrow
Keyword(s):  
Extreme Values ◽  
Light Trap ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Radar Observations ◽  
The North ◽  
South Wales ◽  
Radar Echo ◽  
And Migration ◽  
Trap Catches

AbstractNight migrations of insects above the surface boundary layer were studied by direct observations with an entomological radar, and by direct aerial sampling with a kite-borne net, in an area in New South Wales inhabited by large fledging populations of Chortoicetes terminifera (Wlk.). The aerial catches and radar echo-modulation observations suggested that the majority of migrants detected by the radar were locusts, and this conclusion was supported indirectly by light-trap catches and by observations of take–off at dusk. Night flights of locusts began at dusk with a mass take-off and continued on a diminishing scale until about midnight. Displacements were all approximately downwind and to the north, under the influence of a southerly airflow which prevailed throughout the six-day study period. A quantitative radar observation procedure was used to estimate locust aerial densities and migration rates, and to observe the variations of these quantities with height and time; typical and extreme values for all the principal migration quantities are presented. The flight paths of the locusts were estimated from radar observations of target tracks, and probable source areas at distances of up to 200 km to the south were identified; a major overflight which probably originated 150 km away was detected on one occasion. Northward movements of C. terminifera during anticyclonic conditions may help to explain how populations are redistributed in the periods between the long-range southward invasion movements for which this species is well-known.

Brexit, Labour Rights and Migration: Why Wisbech Matters to Brussels

2016 ◽  
Vol 17 (S1) ◽  
pp. 13-20 ◽  
Author(s):  
Simon Deakin
Keyword(s):  
Working Class ◽  
Economic Insecurity ◽  
Weak Correlation ◽  
Labour Rights ◽  
North East ◽  
The North ◽  
South Wales ◽  
And Migration ◽  
The Eu

In the aftermath of the Brexit referendum of 23 June 2016, the question of migration has been at the forefront of attempts to understand what happened, and in particular why working class communities in many of the regions of England, and in parts of Wales, voted predominantly for the Leave side. Polling data show a weak correlation between areas of the country that voted for Leave and high levels of inward migration from the rest of the EU. The link between immigration and Brexit is very clear in East Anglian agricultural towns like Boston and Wisbech, but otherwise is weak. South Wales and the North East of England, which also saw clear majorities for Leave, are not areas of high EU migration. Instead, they are regions that have experienced successive waves of deindustrialisation since the 1980s. The overriding issue raised by the Brexit vote, in my view, is not migration as such (although that is part of the story), but a wider phenomenon of deepening economic insecurity, and the dangerous political dynamic it has created.

Analysis and interpretation of long term light trap data for Helicoverpa punctigera (Lepidoptera; Noctuidae) in Australia: population changes and forecasting pest pressure

1996 ◽  
Vol 86 (5) ◽  
pp. 547-557 ◽  
Author(s):  
D. Maelzer ◽  
M.P. Zalucki ◽  
R. Laughlin
Keyword(s):  
Light Trap ◽  
South Australia ◽  
Positive Influence ◽  
Weather Data ◽  
Early Season ◽  
South Wales ◽  
Spring Generation ◽  
Negative Effect ◽  
The One ◽  
Trap Catches

AbstractUsing regression analysis the early season dynamics of Helicoverpa punctigera (Wallengren) were determined from long series of light trap catches (10–19 years) from three sites in Australia (Narrabri and Trangie in New South Wales, and Turretfield in South Australia). The size of the second spring generation (G2, the one causing major pest problems in summer cropping regions) was strongly related to the size of the first spring generation (G1). In most cases, rainfall in early winter had a positive influence on the size of G2, whereas rainfall in spring had a negative effect. Regressions were found to account for 49 to 93% of the annual variation in G2, depending on site. The use of light trap catches and weather data to forecast pest levels from a few months to a few weeks in advance is discussed, along with the improved understanding of early season H. punctigera dynamics.

The analysis and standardisation of light-trap catches of Heliothis armiger (Hübner) and H. punctiger Wallengren (Lepidoptera: Noctuidae)

1981 ◽  
Vol 71 (2) ◽  
pp. 207-225 ◽  
Author(s):  
R. Morton ◽  
L. D. Tuart ◽  
K. G. Wardhaugh
Keyword(s):  
Wind Speed ◽  
Light Trap ◽  
Adult Emergence ◽  
Wind Speeds ◽  
South Wales ◽  
Large Numbers ◽  
Successive Generations ◽  
Hourly Distribution ◽  
A Site ◽  
Trap Catches

AbstractHourly and nightly catches of Heliothis armiger (Hb.) and H. punctiger Wllgr. at a site adjacent to 2000 ha of commercial cotton in the Namoi Valley of New South Wales, were analysed in relation to various environmental factors and showed that wind speed, temperature, night-length and (H. armiger only) moonlight exerted a significant influence on trap-catch. For H. punctiger and H. armiger respectively, these factors accounted for 80 and 60% of the deviance in hourly catches but only 70 and 40% of the variation in nightly catches. Wind speeds of more than 1·7 m/s suppressed the catch of both species but had a greater effect on H. punctiger than H. armiger. Whereas with both species, the optimum temperature for trapping was about 27°C, temperature had a greater influence on the catch of H. punctiger than of H. armiger. Bright moonlight was estimated to reduce the catch of H. armiger by 49%, but no significant effect was detected for H. punctiger. The analysis revealed a number of occasions for both species in which the hourly distribution of catch and/or the change in catch between successive nights was aberrant. With H. armiger, these inconsistencies appeared to be associated with changes in population due to adult emergence, whereas for H. punctiger the most likely cause seemed to be changes due to movement. The combined effects of wind speed, temperature, night-length and moonlight were used to adjust the nightly catches of each species according to the environmental conditions prevailing on a ‘ standard’ night. This was defined as a typical summer's night with temperatures decreasing from 28·8°C at dusk to 20·6°C at dawn and ideal catching conditions, i.e. no moon and wind speed never exceeding 1·7 m/s. As such, the adjusted catches could be taken as indices of moth abundance. These showed that H. armiger had three discrete periods of abundance, characterised by the presence of large numbers of young moths and spaced at intervals suggesting successive generations. A similar pattern was lacking in H. punctiger, which was abundant only during the first half of the season. Except during periods of emergence (H.armiger), or once when spraying occured during daylight, the aerial application of insecticides to the cotton adjecent to the light-trap resulted in marked reductions in the populations of both species.

scholarly journals High-resolution observations of the North Pacific transition layer from a Lagrangian float

2021 ◽  
Author(s):  
Alexis K. Kaminski ◽  
Eric A. D’Asaro ◽  
Andrey Y. Shcherbina ◽  
Ramsey R. Harcourt
Keyword(s):  
Mixed Layer ◽  
Transition Layer ◽  
Vertical Motion ◽  
Heat Fluxes ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Diverse Range ◽  
The North ◽  
Temperature Jumps ◽  
Temperature Inversions

AbstractAcrucial region of the ocean surface boundary layer (OSBL) is the strongly-sheared and -stratified transition layer (TL) separating the mixed layer from the upper pycnocline, where a diverse range of waves and instabilities are possible. Previous work suggests that these different waves and instabilities will lead to different OSBL behaviours. Therefore, understanding which physical processes occur is key for modelling the TL. Here we present observations of the TL from a Lagrangian float deployed for 73 days near Ocean Weather Station Papa (50°N, 145°W) during Fall 2018. The float followed the vertical motion of the TL, continuously measuring profiles across it using an ADCP, temperature chain and salinity sensors. The temperature chain made depth/time images of TL structures with a resolution of 6cm and 3 seconds. These showed the frequent occurrence of very sharp interfaces, dominated by temperature jumps of O(1)°C over 6cm or less. Temperature inversions were typically small (≲ 10cm), frequent, and strongly-stratified; very few large overturns were observed. The corresponding velocity profiles varied over larger length scales than the temperature profiles. These structures are consistent with scouring behaviour rather than Kelvin-Helmholtz-type overturning. Their net effect, estimated via a Thorpe-scale analysis, suggests that these frequent small temperature inversions can account for the observed mixed layer deepening and entrainment flux. Corresponding estimates of dissipation, diffusivity, and heat fluxes also agree with previous TL studies, suggesting that the TL dynamics is dominated by these nearly continuous 10cm-scale mixing structures, rather than by less frequent larger overturns.

Method of using kites to carry tow nets in the upper air for sampling migrating insects and its application to radar entomology

1984 ◽  
Vol 74 (1) ◽  
pp. 87-95 ◽  
Author(s):  
R. A. Farrow ◽  
J. E. Dowse
Keyword(s):  
Migration Rate ◽  
Large Diameter ◽  
Free Fall ◽  
Lower Atmosphere ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Quantitative Measurements ◽  
Sequential Samples ◽  
Sampling Height ◽  
And Migration

AbstractInsects migrating above the surface boundary layer were efficiently and economically sampled over long periods using a large diameter tow net suspended beneath a kite. In a series of trials in Australia, sequential samples were obtained by day and night at predetermined altitudes, in the range 50–500 m. The net was raised and lowered independently of the kite, so that when conditions were calm in the lower atmosphere the kite could remain aloft in the geostrophic airflow. Potential contamination of insects flying below the sampling height was minimised during net ascent, by reducing the airflow through the net. A radio-operated net-closing and releasing mechanism prevented contamination during the free fall of the net. The catch was converted to absolute values of aerial density and migration rate or flux. Aerial sampling was originally developed to identify upper air migrants under observation by the CSIRO entomological radar and to provide quantitative measurements of those species too small to be individually detected by radar. The technique was subsequently operated independently of radar to quantify microinsect migrations, but not those of macroinsects because of their relatively low catch rate.

scholarly journals Destratification and Restratification of the Spring Surface Boundary Layer in a Subtropical Front

2021 ◽  
Author(s):  
Eric Kunze ◽  
John B. Mickett ◽  
James B. Girton
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Surface Fluxes ◽  
Minor Role ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Subtropical Front ◽  
The North ◽  
A Minor ◽  
The North Pacific

AbstractDestratification and restratification of a ~50-m thick surface boundary layer in the North Pacific Subtropical Front are examined during 24-31 March 2017 in the wake of a storm using a ~ 5-km array of 23 chi-augmented EM profiling floats (u, v, T, S, χT), as well as towyo and ADCP ship surveys, shipboard air-sea surface fluxes and parameterized shortwave penetrative radiation. During the first four days, nocturnal destabilizing buoyancy-fluxes mixed the surface layer over almost its full depth every night followed by restratification to N ~ 2 × 10–3 rad s–1 during daylight. Starting on 28 March, nocturnal destabilizing buoyancy-fluxes weakened because weakening winds reduced the latent heat-flux. Shallow mixing and stratified transition layers formed above ~20-m depth. The remnant layer in the lower part of the surface layer was insulated from destabilizing surface forcing. Penetrative radiation, turbulent buoyancy-fluxes and horizontal buoyancy advection all contribute to restratification of this remnant layer, closing the budget to within measurement uncertainties. Buoyancy advective restratification (slumping) plays a minor role. Before 28 March, measured advective restratification ∫(uzbx + vzby)dt is confined to daytime, is often destratifying and is much stronger than predictions of geostrophic adjustment, mixed-layer eddy instability and Ekman buoyancy-flux predictions because of storm-forced inertial shear. Starting on 28 March, the subinertial envelope of measured buoyancy advective restratification in the remnant layer resembles MLE parameterization predictions.

Insect migration across Bass Strait during spring: a radar study

1981 ◽  
Vol 71 (3) ◽  
pp. 449-466 ◽  
Author(s):  
V. A. Drake ◽  
K. F. Helm ◽  
J. L. Readshaw ◽  
D. G. Reid
Keyword(s):  
Large Scale ◽  
Insect Flight ◽  
New South ◽  
Light Trap ◽  
South Australia ◽  
South Wales ◽  
Insect Migration ◽  
Western Victoria ◽  
Trap Catches ◽  
North Western

AbstractAn entomological radar was used to observe insect flight activity at a coastal locality in north-western Tasmania during the spring of 1973. Insects were regularly observed to take off at dusk, and local movements from nearby islands were detected on several occasions. Large-scale southward movements of insects across Bass Strait were also observed and were found to be associated with the warm anticyclonic airflows which occur ahead of a cold front. Light-trap catches indicated that the insects were noctuid moths, with Persectania ewingii (Westw.), Heliothis punctiger Wllgr. and Agrotis munda Wlk. dominant. The movements appear to have originated mainly in Victoria and south-eastern South Australia, but it is tentatively suggested that the ultimate source of the moths was in the region stretching westwards from north-western Victoria and south-western New South Wales towards the shores of the Spencer Gulf, South Australia.

scholarly journals Windfield related light-trap catches of Nephotettix spp. (N. virescens Distant and N. nigropictus stål), vectors of rice tungro virus in West Bengal

MAUSAM ◽  
2021 ◽  
Vol 48 (1) ◽  
pp. 83-88
Author(s):  
SUJATA MUKHOPADHYAY ◽  
S. MUKHOPADHYAY
Keyword(s):  
Trajectory Analysis ◽  
West Bengal ◽  
Light Trap ◽  
Trapping Site ◽  
North East ◽  
The North ◽  
Trap Catches ◽  
High Catch ◽  
Very High ◽  
Overcast Sky

ABSTRACT. Regular peak catches of rice green leafhoppers, Nephoteltix virescens (Distant) and N. nigropictus (Stal) are usually obtained in a light-trap 60 ± 14 days after the peak monsoon rains in August in West Bengal. In 1986, in addition to this peak catch, very high catches were obtained on two different dates, 17 September and 10 November. The high catch on 17 September was probably due to the increase of the effective trap radius caused by the overcast sky and by the presence of a resident population. The high catch on 10 November was due to the transport of the insects by cyclonic winds and deposition in a zone of light and variable winds (at a convergence) real the trapping site. Trajectory analysis indicates that these insects may have been brought from the north-east, upto about 280 km away from the trapping site.      

scholarly journals North Pacific Upper-Ocean Cold Temperature Biases in CMIP6 Simulations and the Role of Regional Vertical Mixing

2020 ◽  
Vol 33 (17) ◽  
pp. 7523-7538 ◽  
Author(s):  
Yuchao Zhu ◽  
Rong-Hua Zhang ◽  
Jichang Sun
Keyword(s):  
North Pacific ◽  
Vertical Mixing ◽  
Cold Temperature ◽  
Cold Bias ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
The North ◽  
Vertical Diffusivity ◽  
The North Pacific

AbstractSubstantial model biases are still prominent even in the latest CMIP6 simulations; attributing their causes is defined as one of the three main scientific questions addressed in CMIP6. In this paper, cold temperature biases in the North Pacific subtropics are investigated using simulations from the newly released CMIP6 models, together with other related modeling products. In addition, ocean-only sensitivity experiments are performed to characterize the biases, with a focus on the role of oceanic vertical mixing schemes. Based on the Argo-derived diffusivity, idealized vertical diffusivity fields are designed to mimic the seasonality of vertical mixing in this region, and are employed in ocean-only simulations to test the sensitivity of this cold bias to oceanic vertical mixing. It is demonstrated that the cold temperature biases can be reduced when the mixing strength is enhanced within and beneath the surface boundary layer. Additionally, the temperature simulations are rather sensitive to the parameterization of static instability, and the cold biases can be reduced when the vertical diffusivity for convection is increased. These indicate that the cold temperature biases in the North Pacific can be largely attributed to biases in oceanic vertical mixing within ocean-only simulations, which likely contribute to the even larger biases seen in coupled simulations. This study therefore highlights the need for improved oceanic vertical mixing in order to reduce these persistent cold temperature biases seen across several CMIP models.

Prediction of Atmospheric Turbulence Characteristics for Surface Boundary Layer using Empirical Spectral Methods

2020 ◽  
Author(s):  
Yagya Dutta Dwivedi ◽  
Vasishta Bhargava Nukala ◽  
Satya Prasad Maddula ◽  
Kiran Nair
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Surface Roughness ◽  
Wind Speed ◽  
Atmospheric Turbulence ◽  
Surface Boundary ◽  
Low Frequencies ◽  
Surface Boundary Layer ◽  
Power Spectral ◽  
Mean Wind Speed

Abstract Atmospheric turbulence is an unsteady phenomenon found in nature and plays significance role in predicting natural events and life prediction of structures. In this work, turbulence in surface boundary layer has been studied through empirical methods. Computer simulation of Von Karman, Kaimal methods were evaluated for different surface roughness and for low (1%), medium (10%) and high (50%) turbulence intensities. Instantaneous values of one minute time series for longitudinal turbulent wind at mean wind speed of 12 m/s using both spectra showed strong correlation in validation trends. Influence of integral length scales on turbulence kinetic energy production at different heights is illustrated. Time series for mean wind speed of 12 m/s with surface roughness value of 0.05 m have shown that variance for longitudinal, lateral and vertical velocity components were different and found to be anisotropic. Wind speed power spectral density from Davenport and Simiu profiles have also been calculated at surface roughness of 0.05 m and compared with k−1 and k−3 slopes for Kolmogorov k−5/3 law in inertial sub-range and k−7 in viscous dissipation range. At high frequencies, logarithmic slope of Kolmogorov −5/3rd law agreed well with Davenport, Harris, Simiu and Solari spectra than at low frequencies.

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