Modulation of local wind-waves at Kalpakkam from remote forcing effects of Southern Ocean swells

Publisher Summary This chapter discusses the effects of local wind systems on insect migration at night. Many insect species undertake migratory flights at night. Such flights are usually dominated by the wind because the insects climb to heights where the wind speed exceeds their own flying speed through the air. Consequently, the distance moved is essentially the product of wind speed and duration of flight. The results throw light on the occurrence of clouds of flying adults and on the clumped distribution of populations of migrants on the ground. Much of the evidence comes from field studies of a few pest species, but it is likely that many other species are similarly affected. Several types of wind system are considered: low-level jet streams, coastal winds, rainstorm outflows, down-slope and down-valley winds, and a variety of local winds caused by barrier effects of mountains. Furthermore, field studies need to put emphasis on atmospheric behavior through supplementary observations of winds and temperatures in the lowest kilometer of the atmosphere. This chapter discusses coastal winds, bores and solitary waves, rainstorm outflows, and mountain winds: drainage winds and barrier winds in reference to the nocturnal insects.

Nocturnal Insect Migration: Effects of Local Winds

Thermodynamical observations by a helicopter have been conducted to study the internal structure of the sea breeze blowing inland from Tosa Bay during three periods (September 1993, November 1994 and 1995). Inland-intrusion distances of the midday sea breeze observed at each flight leg were in the 10–25-km range, depending on the intensity of the ambient flow associated with the gradient wind, atmospheric stratification, and the geographical features of the observed area. The sea breeze observed over the sea had well-defined features, in particular a turbulent wake behind the head of the sea-breeze front and a closed sea-breeze circulation cell containing the subsidence of the return flow. In addition, a moist layer distributed around 15–20 km offshore forms because the land breeze moves in this region. Moreover, a calm condition exists from the coast to about 10 km offshore. Both phenomena are found before the onset of the sea breeze in the early morning. Such remarkable characteristics of the s...

Helicopter Observations of the Sea Breeze over a Coastal Area

In this paper, COSMO numerical weather prediction model is used to simulate land-sea breeze circulation in the north coast of Oman and to analyze the variability of the PBL depth. Typical summer day 1st August 2009 and winter day 1st January 2009 were simulated and verified by surface observations. The COSMO model was initialized using the German global model which runs as 40 km resolution and 40 vertical layers. The simulations show differences in the onset, strength, and inland penetration of the sea breeze. The high sea-land thermal contrast in the summer season induces earlier onset and progression of the sea breeze with larger horizontal and vertical extents. The summer and winter inland penetration is simulated around 150 and 65 km, respectively. The PBL depth was defined from the verticals profiles of the turbulence kinetic energy (TKE). The simulated PBL height varied at 1,600 m in summer and 700 m in the winter case. These results are in general in good agreement with the simulations of the National Centers for Environmental Prediction Global Data Assimilation System (NCEP-GDAS) model. The dispersive ability of the atmosphere was tested through the vertical mixing coefficient (VMC) generated by NCEP-GDAS simulations. The VMC during the summer simulated case is approximately four times larger than the respective one during the winter case. Consequently, during the advection of winter sea breeze, a shallow dome less than 100 m is shaped and forms an obstacle to the air-pollutant dispersion.

Assessment of the impact of the meteorological meso-scale circulation on air quality in arid subtropical region.

Sea breeze characteristics around Kalpakkam tropical coastal site are studied using an Advanced Regional Prediction System (ARPS) mesoscale model, which is non-hydrostatic, compressible atmospheric prediction model following the terrain coordinate system. Various options such as surface physics, atmospheric radiation physics, Coriolis force, microphysics, cumulus parameterization and 1.5 level TKE closure scheme for diffusion are included in the model.

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Numerical simulation of sea breeze characteristics observed at tropical coastal site, Kalpakkam

Meteorological observation by a helicopter was carried out to investigate the structure of sea breezes over the coastal area of Tosa Bay in Shikoku island, Japan. Several groups of wave trains were found over the sea during a flight made on 25 November 1992. Not only the terrain barrier but the remaining cold air pools formed in valleys hindered further advance of the sea breeze inland, so that the presence of such wave trains may appear to be due to the effect of the secondary flow which supplies moister and cooler air from behind the sea breeze front.

F. Kobayashi

Papers

Wave trains over the sea due to sea breezes