introduction occurrence of heavy and rainstorm events is among the characteristics of arid and semi-arid regions all over the world and particularly in iran which is causing large floods and debris town. how ever, they can be used to supply and store water by controlling and exploiting the run off water floods. indexes of atmospheric instability are very useful scientific instruments to underst...

Asymmetric structure of tropical cyclones simulated by the Geophysical Fluid Dynamics Laboratory highresolution triply nested movable-mesh hurricane model was analyzed. Emphasis was placed on the quasi-steady component of the asymmetric structure in the region of the eyewall. It was found that the asymmetry was primarily caused by the relative wind, that is, the flow entering and leaving the st...

Hurricane and tropical storm statistics verify the modulation of eastern Pacific tropical systems by the Madden– Julian oscillation (MJO) as hypothesized by Maloney and Hartmann. Over twice as many named tropical systems (hurricanes and tropical storms) accompany equatorial 850-mb westerly anomalies than accompany equatorial easterly anomalies, and the systems that do exist are stronger. Hurric...

1. introduction heavy snow hazards, although have less frequency in comparison with extreme weather events such as freezing, but are major hazards in midlatitudes (smith, 2009, 196). heavy snow damages manmade structures, crops, casualties, even between urban and rural ways of blocking.(briant. 69, 2005. ohara et al, 2009, 1611). various definitions have been offered for heavy snow, those are c...

A high-resolution upper-ocean survey of a cyclonic jet meander and an adjacent cyclonic eddy in the California Current region near 388N, 1268W was conducted as part of the summer of 1993 Eastern Boundary Currents program. Temperature and salinity were measured from a SeaSoar vehicle, and velocity was measured by shipboard acoustic Doppler current profiler (ADCP). SeaSoar data show a density fro...

Research into dynamic bushfire behaviour conducted over the last few years has shown that bushfires burning on lee-facing slopes can exhibit atypical forms of propagation under extreme weather conditions. For instance, recent numerical simulations have indicated that pyrogenic vorticity (the curl of the velocity field) is a key driver of rapid lateral fire spread as a consequence, this type of ...

The effect of a background rotation on the decay of homogeneous turbulence produced by a grid is experimentally investigated. Experiments have been performed in a channel mounted in the large-scale ’Coriolis’ rotating platform, and measurements have been carried out in the planes normal and parallel to the rotation axis using particle image velocimetry. After a short period of about 0.4 tank ro...

the development of the dynamical core of a potential-vorticity-based atmospheric general circulation model is explored. there are some advantages of using potential vorticity (pv) as a prognostic variable in that the resulting model can give more accurate simulation of the evolution of pv, as arguably the most fundamental dynamical quantity. further, there is possibility of explicit representat...

ENSO (El Niño–Southern Oscillation) has a large influence on tropical cyclone activity. The authors examine how different environmental factors contribute to this influence, using a genesis potential index developed by Emanuel and Nolan. Four factors contribute to the genesis potential index: low-level vorticity (850 hPa), relative humidity at 600 hPa, the magnitude of vertical wind shear from ...