Impact of typhoon on the north-west Pacific sea surface temperature: a case study of Typhoon Kaemi (2006)

Natural Hazards - Tropical cyclones, also known as typhoons, in the north-west Pacific are important air–sea interaction process that transports massive amounts of heat and moisture. Due to...     

Breaking of a tidal internal wave on a steep shelf as inferred from temperature measurements

The structure, evolution, and breaking of a tidal internal wave on a steep shelf are discussed on the basis of the data of temperature measurements. The bottom slope at the measurement site is close to the critical slope for a tidal wave. The tidal wave and other waves are inclined coastward. The tidal-wave amplitude increases monotonically with increasing horizon depth. The tidal wave is nonlinear in amplitude and turns over on the outer shelf. On the inner shelf, the internal wave is close in shape to rectangular and generates harmonics of its own. The harmonics make the tidal wave steeper and form solitary rises similar to bilateral bores. All these features ensure a more rapid sink for the internal-tide energy.     

Water erosion in the Southern Ural steppes

Ecological-hydrological analysis of erosion processes on the key watersheds of Southern Ural steppe was used to determine the surface runoff as a function of the physico-geographic and anthropogenic conditions, i.e., snow storage and soil moisture reserves before winter, whose contribution reaches 68–81%. The rate of humus losses in chernozems and dark chestnut soils was calculated for different periods in accordance with erosion stress and the extent of the economic development of the territory. Agroecological types of arable lands with different surface runoff characteristics, rates of natural soil formation, and erosionrelated soil losses are identified. Measures aimed to reduce humus losses in soils are proposed. Relationships between the rates of soil formation and erosion losses are proposed to be used as ecological-hydrological criterion (index) of soil stability.     

DETECTION OF LATERAL VARIATIONS IN GEOLOGICAL STRUCTURES USING ELECTRICAL RESISTIVITY GRADIENT PROFILING1

Hydrogeological problems which involve the determination of lateral variations in structures or physical properties may be solved with electrical resistivity gradient profiling if there are significant variations in electrical resistivity, spatially or temporally. The method is explained, evaluated for sensitivity, compared with other methods, and applied to the location of volcanic dike zones that are impounding an anomalous water body near Schofield, Oahu, Hawaii. From the electrical soundings and other independent data, the lateral positions of the boundaries have been refined and their nature estimated.     

Observations of the upper frequency cutoffs of the auroral kilometric radiation

Intense auroral kilometric radiation (AKR) is being frequently observed with POLRAD from the Auroral Probe (Interball-2). Observations of the abrupt upper frequency cutoffs (UFCs) in the spectra of AKR are reported. The UFCs can be observed at a frequency range from 300 to 700 kHz, corresponding to AKR generation altitudes from approximately 4800 to 2100 km, and are distributed in magnetic local time (MLT) hours similarly to the AKR events, with a maximum at 1 h MLT. The observed frequency extent of the UFCs is 12 kHz, and is often determined by the instrumental resolution (4 kHz). It is suggested that the UFC may be associated with an abrupt switching on of the generation mechanism, when the electron density becomes sufficiently low inside a plasma depletion at an altitude where the ratio of f_pe/f_ce crosses some threshold value. The steepness of the UFCs can imply a non-linear process of generation. The estimated distance of the e-folding field aligned wave amplification is between 3 and 8 km. The UFCs are sometimes, though very seldom (10%), accompanied by narrow band (less than 4 kHz) ridges of radiation observed at the cutoff frequency. They are smoothly drifting in frequncy for several minutes. The power density of radiation in the ridge can be up to 2 orders of magnitude stronger than in the accompanying wide band emission of AKR. The ridge at UFC can imply either energy concentration at the source bottom, or focusing, if specific conditions for the escape of the radiation are assumed.