Flights after sunset by the Australian plagye locust, Chortoicetes terminifera (Walk.) and their significance in dispersal and migration

1971 ◽  
Vol 19 (2) ◽  
pp. 159 ◽  
Author(s):  
DP Clark
Keyword(s):  
Major Part ◽  
Surface Wind ◽  
Distribution Area ◽  
Pressure Gradients ◽  
Random Orientation ◽  
Wind Speeds ◽  
Air Temperatures ◽  
Mass Displacement ◽  
And Migration ◽  
Low Wind Speeds

Adult C. terminifera take off shortly after sunset, climb steeply into the air, and fly out of sight. This steep take-off differs from that of locusts that take flight during the day. One important factor which induces take-off appears to be decreasing light intensity. Take-off has been recorded at air temperatures as low as 17*5"C, relative humidities that ranged from 9 to 70%, and surface wind speeds (at 2 m) which varied from 1 .7 to 21 -2 ft/sec. Initially the locusts take off into wind. At low surface wind speeds individuals subsequently fly out of sight, dispersing in various directions, but at winds in excess of 6 ftlsec the locusts orient and fly downwind. Hundreds of individuals were seen flying away from concentrations of sexually immature adults on successive evenings in 1969. It appears that flight occurs on practically every evening when temperatures are suitable. Significant numbers of C. terminifera appear at lights during the night only during disturbed weather caused by the approach and passage of depressions. In view of the random orientation of flying locusts with respect to wind at low wind speeds, it is suggested that under dry anticyclonic conditions with slight pressure gradients flights after sunset would lead to widespread dispersal, i.e. scattering of individuals over large areas. The downwind orientation at higher wind speeds, which would result in greater displacement, is associated with the approach and passage of depressions (low pressure systems) and the development of storms. In addition to this the increased turbulence of the winds accelerating ahead of the depression (mainly northerlies) and the convergent air flow from the opposite quarter behind the depression would lead to concentration of the locusts in flight. The hypothesis outlined above would explain the striking changes in distribution and densities that frequently occur among populations of adult C. terminifera. Dispersal under dry anticyclonic conditions, and concentration and mass displacement during periods of disturbed weather during which rain-storms may produce conditions favourable for breeding, play an important part in the survival of C. terminifera. In the major part of its distribution area the probability of effective rain in any particular locality is low.

scholarly journals CYGNSS Ocean Surface Wind Validation in the Tropics

2020 ◽  
Author(s):  
Shakeel Asharaf ◽  
Duane E. Waliser ◽  
Derek J. Posselt ◽  
Christopher S. Ruf ◽  
Chidong Zhang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Satellite System ◽  
Cold Pool ◽  
Tropical Ocean ◽  
Near Surface ◽  
Wind Speeds ◽  
Low Wind Speeds ◽  
Global Navigation Satellite

AbstractSurface wind plays a crucial role in many local/regional weather and climate processes, especially through the exchanges of energy, mass and momentum across the Earth’s surface. However, there is a lack of consistent observations with continuous coverage over the global tropical ocean. To fill this gap, the NASA Cyclone Global Navigation Satellite System (CYGNSS) mission was launched in December 2016, consisting of a constellation of eight small spacecrafts that remotely sense near surface wind speed over the tropical and sub-tropical oceans with relatively high sampling rates both temporally and spatially. This current study uses data obtained from the Tropical Moored Buoy Arrays to quantitatively characterize and validate the CYGNSS derived winds over the tropical Indian, Pacific, and Atlantic Oceans. The validation results show that the uncertainty in CYGNSS wind speed, as compared with these tropical buoy data, is less than 2 m s-1 root mean squared difference, meeting the NASA science mission Level-1 uncertainty requirement for wind speeds below 20 m s-1. The quality of the CYGNSS wind is further assessed under different precipitation conditions, and in convective cold-pool events, identified using buoy rain and temperature data. Results show that CYGNSS winds compare fairly well with buoy observations in the presence of rain, though at low wind speeds the presence of rain appears to cause a slight positive wind speed bias in the CYGNSS data. The comparison indicates the potential utility of the CYGNSS surface wind product, which in turn may help to unravel the complexities of air-sea interaction in regions that are relatively under-sampled by other observing platforms.

scholarly journals IDENTIFIKASI ARSITEKTUR TROPIS PADA BANGUNAN LAMA DI JALAN SITI KHADIJAH KOTA BENGKULU

2020 ◽  
Vol 5 (2) ◽  
pp. 89-96
Author(s):  
Fitrianty Wardhani ◽  
Dwi Oktavallyan
Keyword(s):  
Heavy Rain ◽  
Tropical Climate ◽  
Local Climate ◽  
Wind Speeds ◽  
Architectural Elements ◽  
Air Temperatures ◽  
Qualitative Descriptive ◽  
Tropical Architecture ◽  
Low Wind Speeds ◽  
The Tropics

Title: Identify tropical architecture in the old building at Jalan Siti Khadijah Bengkulu City Tropical architecture tries to deal with the tropical climate problems characterized by heavy rain, blazing sun, high air temperatures, high humidity (for humid tropics), and low wind speeds. The realization of a sustainable tropical city requires building environmentally responsive designs. The efforts could be made, such as selecting materials and models on buildings' external and internal appearance that suit to tropical city. Old buildings used to be built to adapt to the local climate. One of them is the old buildings on Khadijah street, which the existence is almost gone now. This study aims to identify the tropics element in old buildings that have adapted to the tropical climate. The method used in this research is a qualitative descriptive method in case studies through observation and identification of the application of tropical architectural elements in the external appearance (building and roof orientation) and the internal appearance in the building (space, floor, wall, and opening patterns). The aim of this research is to fulfill the arguments for the community about the significance of maintaining the old buildings. This finding is needed to provide a logical reason for the community and government to conserve the old buildings in Bengkulu City.

scholarly journals A Comparative Assessment of Surface Wind Speed and Sea Surface Temperature over the Indian Ocean by TMI, MSMR, and ERA-40

2007 ◽  
Vol 24 (6) ◽  
pp. 1131-1142 ◽  
Author(s):  
Anant Parekh ◽  
Rashmi Sharma ◽  
Abhijit Sarkar
Keyword(s):  
Wind Speed ◽  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Microwave Radiometer ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Sea Surface ◽  
Wind Speeds ◽  
Low Wind Speeds

A 2-yr (June 1999–June 2001) observation of ocean surface wind speed (SWS) and sea surface temperature (SST) derived from microwave radiometer measurements made by a multifrequency scanning microwave radiometer (MSMR) and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) is compared with direct measurements by Indian Ocean buoys. Also, for the first time SWS and SST values of the same period obtained from 40-yr ECMWF Re-Analysis (ERA-40) have been evaluated with these buoy observations. The SWS and SST are shown to have standard deviations of 1.77 m s−1 and 0.60 K for TMI, 2.30 m s−1 and 2.0 K for MSMR, and 2.59 m s−1 and 0.68 K for ERA-40, respectively. Despite the fact that MSMR has a lower-frequency channel, larger values of bias and standard deviation (STD) are found compared to those of TMI. The performance of SST retrieval during the daytime is found to be better than that at nighttime. The analysis carried out for different seasons has raised an important question as to why one spaceborne instrument (TMI) yields retrievals with similar biases during both pre- and postmonsoon periods and the other (MSMR) yields drastically different results. The large bias at low wind speeds is believed to be due to the poorer sensitivity of microwave emissivity variations at low wind speeds. The extreme SWS case study (cyclonic condition) showed that satellite-retrieved SWS captured the trend and absolute magnitudes as reflected by in situ observations, while the model (ERA-40) failed to do so. This result has direct implications on the real-time application of satellite winds in monitoring extreme weather events.

scholarly journals Inconsistencies in the “New” Windchill Chart at Low Wind Speeds

2006 ◽  
Vol 45 (5) ◽  
pp. 787-790 ◽  
Author(s):  
Avraham Shitzer ◽  
Richard de Dear
Keyword(s):  
Wind Speed ◽  
Convective Heat Exchange ◽  
The United States ◽  
Exchange Coefficient ◽  
Heat Exchange Coefficient ◽  
Wind Speeds ◽  
Speed Condition ◽  
Air Temperatures ◽  
Low Wind Speeds ◽  
Calm Wind

Abstract An apparent error was detected in the calculation of windchill equivalent temperatures (WCETs) in the “new” chart and corresponding equation that were adopted in 2001 by the weather services in the United States and Canada. The problem is caused by significant discontinuities in WCETs at the assumed “calm” wind speed condition of 1.34 m s−1. As a result, published WCETs are not equal to, as they should be by definition, but are lower than air temperatures at the assumed calm wind speed condition. This inconsistency further propagates to higher wind speeds beyond the assumed calm condition. In this paper, a straightforward correction is proposed to circumvent these inconsistencies of the new windchill. The proposed correction makes this transition gradual rather than abrupt by applying it to the expression used for estimating the effects of wind on the convective heat exchange coefficient between humans and their cold and windy environment.

An Introduction to the Near–Real–Time QuikSCAT Data

2005 ◽  
Vol 20 (4) ◽  
pp. 476-493 ◽  
Author(s):  
Ross N. Hoffman ◽  
S. Mark Leidner
Keyword(s):  
Data Quality ◽  
Objective Function ◽  
Surface Wind ◽  
Heavy Rain ◽  
Ocean Surface ◽  
Wind Speeds ◽  
The North ◽  
Ocean Surface Winds ◽  
Low Wind Speeds ◽  
Meteorological Features

Abstract The NASA Quick Scatterometer (QuikSCAT) satellite carries the SeaWinds instrument, the first satellite-borne scanning radar scatterometer. QuikSCAT, which was launched on 19 June 1999, is designed to provide accurate ocean surface winds in all conditions except for moderate to heavy rain (i.e., except for vertically integrated rain rate >2.0 km mm h−1, the value used to tune the SeaWinds rain flag). QuikSCAT data are invaluable in providing high-quality, high-resolution winds to detect and locate precisely significant meteorological features and to produce accurate ocean surface wind analyses. QuikSCAT has an 1800-km-wide swath. A representative swath of data in the North Atlantic at 2200 UTC 28 September 2000, which contains several interesting features, reveals some of the capabilities of QuikSCAT. Careful quality control is vital for flagging data that are affected by rain and for flagging errors during ambiguity removal. In addition, an understanding of the instrument and algorithm characteristics provides insights into the factors controlling data quality for QuikSCAT. For example data quality is reduced for low wind speeds, and for locations either close to nadir or to the swath edges. The special data characteristics of the QuikSCAT scatterometer are revealed by examining the likelihood or objective function. The objective function is equal to the sum of squared scaled differences between observed and simulated normalized reflected radar power. The authors present typical examples and discuss the associated data quality concerns for different parts of the swath, for different wind speeds, and for rain versus no rain.

scholarly journals Factors Affecting Surface Wind Speeds in Gravity Waves and Wake Lows

2009 ◽  
Vol 24 (6) ◽  
pp. 1664-1679 ◽  
Author(s):  
Timothy A. Coleman ◽  
Kevin R. Knupp
Keyword(s):  
Gravity Waves ◽  
High Surface ◽  
Surface Wind ◽  
Wind Damage ◽  
Pressure Gradients ◽  
Surface Winds ◽  
Factors Affecting ◽  
Wind Speeds ◽  
Multiple Case ◽  
Speed Of Propagation

Abstract Ducted gravity waves and wake lows have been associated with numerous documented cases of “severe” winds (>25 m s−1) and wind damage. These winds are associated with the pressure perturbations and transient mesoscale pressure gradients occurring in many gravity waves and wake lows. However, not all wake lows and gravity waves produce significant winds nor wind damage. In this paper, the factors that affect the surface winds produced by ducted gravity waves and wake lows are reviewed and examined. It is shown theoretically that the factors most conducive to high surface winds include a large-amplitude pressure disturbance, a slow intrinsic speed of propagation, and an ambient wind with the same sign as the pressure perturbation (i.e., a headwind for a pressure trough). Multiple case studies are presented, contrasting gravity waves and wake lows with varying amplitudes, intrinsic speeds, and background winds. In some cases high winds occurred, while in others they did not. In each case, the factor(s) responsible for significant winds, or the lack thereof, are discussed. It is hoped that operational forecasters will be able to, in some cases, compute these factors in real time, to ascertain in more detail the threat of damaging wind from an approaching ducted gravity wave or wake low.

On Trade Wind Cumulus Cold Pools

2012 ◽  
Vol 69 (1) ◽  
pp. 258-280 ◽  
Author(s):  
Paquita Zuidema ◽  
Zhujun Li ◽  
Reginald J. Hill ◽  
Ludovic Bariteau ◽  
Bob Rilling ◽  
...  
Keyword(s):  
Latent Heat ◽  
Surface Wind ◽  
Radar Data ◽  
Heat Fluxes ◽  
Trade Wind ◽  
Cold Pool ◽  
Wind Speeds ◽  
Cold Pools ◽  
Air Temperatures ◽  
Surface Buoyancy

Abstract Shallow precipitating cumuli within the easterly trades were investigated using shipboard measurements, scanning radar data, and visible satellite imagery from 2 weeks in January 2005 of the Rain in Cumulus over the Ocean (RICO) experiment. Shipboard rainfall rates of up to 2 mm h−1 were recorded almost daily, if only for 10–30 min typically, almost always from clouds within mesoscale arcs. The precipitating cumuli, capable of reaching above 4 km, cooled surface air by 1–2 K, in all cases lowered surface specific humidities by up to 1.5 g kg−1, reduced surface equivalent potential temperatures by up to 6 K, and were often associated with short-lived increases in wind speed. Upper-level downdrafts were inferred to explain double-lobed moisture and temperature sounding profiles, as well as multiple inversions in wind profiler data. In two cases investigated further, the precipitating convection propagated faster westward than the mean surface wind by about 2–3 m s−1, consistent with a density current of depth ~200 m. In their cold pool recovery zones, the surface air temperatures equilibrated with time to the sea surface temperatures, but the surface air specific humidities stayed relatively constant after initial quick recoveries. This suggested that entrainment of drier air from above fully compensated the moistening from surface latent heat fluxes. Recovery zone surface wind speeds and latent heat fluxes were not higher than environmental values. Nonprecipitating clouds developed after the surface buoyancy had recovered (barring encroachment of other convection). The mesoscale arcs favored atmospheres with higher water vapor paths. These observations differed from those of stratocumulus and deep tropical cumulus cold pools.

scholarly journals Canard optimization for enhancing the performance of small horizontal axis wind turbine at low wind speeds

2020 ◽  
Vol 37 ◽  
pp. 63-71
Author(s):  
Yui-Chuin Shiah ◽  
Chia Hsiang Chang ◽  
Yu-Jen Chen ◽  
Ankam Vinod Kumar Reddy
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Peak Performance ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Optimum Parameters ◽  
Low Wind Speeds

ABSTRACT Generally, the environmental wind speeds in urban areas are relatively low due to clustered buildings. At low wind speeds, an aerodynamic stall occurs near the blade roots of a horizontal axis wind turbine (HAWT), leading to decay of the power coefficient. The research targets to design canards with optimal parameters for a small-scale HAWT system operated at variable rotational speeds. The design was to enhance the performance by delaying the aerodynamic stall near blade roots of the HAWT to be operated at low wind speeds. For the optimal design of canards, flow fields of the sample blades with and without canards were both simulated and compared with the experimental data. With the verification of our simulations, Taguchi analyses were performed to seek the optimum parameters of canards. This study revealed that the peak performance of the optimized canard system operated at 540 rpm might be improved by ∼35%.

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