Broadband convex impedance ground planes for multi-system GNSS reference station antennas

Common choke ring ground planes are known to contribute to undesirable antenna pattern narrowing in the elevation plane which is associated with difficulties of tracking low elevation satellites. Also known is the comparatively narrow frequency bandwidth of the choke grooves structure. As an alternative, using a convex impedance ground plane has been suggested for full-spectrum GNSS applications. With such ground planes a pin structure is utilized instead of choke grooves to allow a frequency bandwidth increase. A semi-spherical shape of the ground plane is shown to provide increased antenna gain for low elevation angles. Theoretical performance estimates along with experimental test data have been provided.     

Numerical modeling of the influence of cool skin on the heat balance and thermal regime of a water body

The influence that cool skin has on the energy exchange between the atmosphere and the ocean is investigated in this work. For this purpose, a series of numerical experiments with the use of the one-dimensional LAKE model of a water body were performed. Three types of cold-skin parameterization were used in this model. The data of in situ measurements in the coastal zone of the Black Sea, in the Arctic Ocean, and over Lake Sparkling served as the boundary and initial conditions. It has been established from the results of experiments that the LAKE model with the incorporated parameterization of the cool skin successfully reproduces cold-skin characteristics, namely, the difference between the temperature of the cool skin surface and the water temperature below the skin. The results of numerical experiments are within the variability of the results of in situ measurements. It has been shown that the presence of a cool skin reduces the heat losses of a body of water. The numerical experiments showed that the presence of a cool skin can change the thermal regime of a water body and its stratification by changing the heat balance at the surface. This result can be important for the modeling of many processes inside a body of water and at its surface, for example, gas and heat exchange.     

Investigation of the impact of dynamic factors on Cb cloud development in Saudi Arabia

Changes are analyzed of a Cb cloud characteristics due to its merging with feeder clouds, on the data on a long-living Cb cloud in Saudi Arabia on July 4, 2008. Continuous radar and satellite observations of the cloud are carried out during 6 h. The Cb cloud development is also numerically simulated using a nonstationary 1½ model. It is found that the processes of Cb cloud merging with feeder clouds developing in its vicinities affect significantly the Cb cloud development. This impact demonstrates itself in longer duration of the Cb cloud life span, increasing top height, reflectivity, precipitation duration and intensity. Modification of the feeder clouds can accelerate their development, which eventually can affect notably the Cb cloud.     

Estimation of the results of the cumulonimbus cloud modification aiming at hailstorm mitigation in Alberta (Canada) on the radar and numerical modeling data

In this paper, physical effects caused by a crystallizing reagent in the deep stable cloud, which was developing on July 7, 2006 in Alberta, Canada, are analysed. The ultimate goal of that experiment was reducing economical losses caused by hail. The radar data analysis and numerical modeling showed that use of the reagent allowed significant reducing the hail particles size.     

Numerical modeling of methane emissions from lakes in the permafrost zone

A brief review of published observations of methane fluxes to the atmosphere from bogs and lakes in the permafrost zone is presented. Approaches to modeling the emission of methane from bogs are considered, and their advantages and shortcomings, in particular, from the point of view of their coupling to climate models, are outlined. A one-dimensional model developed by the authors for methane generation, transport, and sink in the ground-water body system and coupled to a hydrothermodynamic model of a water body is described. The approaches used in analogous models for bogs as well as new parametrizations describing lake-specific processes are applied. A parametrization of methane generation in vicinity the lower boundary of the thawed ground zone underneath a water body (talik) is suggested. The results of calibrating this model against available observations of methane emission from the thermokarst Shuchi Lake in northeastern Siberia are discussed.     

The Kanin–Timan–Pechora province of Late Devonian intraplate magmatism (position and size)

Investigation of the distribution of basalts, dolerites, and tuffs in the Kanin–Timan–Pechora large igneous province was completed by generalization of data of geological surveys and analysis of the data of deep drilling. The province appears like a nonisometric ellipse and extends northwestward for a distance of nearly 850 km at the width of 250–500 km. Its area is nearly 285 000 km². The area of the volcanic rocks is about 85 500 km². The volume of eruptive material alone could be equal to 1000–1200 km³. The age of formation of the traps corresponds to the late period of activity of the process and was less than 7 mln. y. The formation of the province was result of the action of short-lived and low intensity plumes. But it was one of the episodes of the Late Devonian superplume event in the East European platform. The province is separated by an amagmatic area from neighboring magmatic provinces of the same age. The distance between borders of the provinces is 200–400 km.     

Numerical simulation of the structure and evolution of a polar mesocyclone over the Kara Sea. Part 1. Model validation and estimation of instability mechanisms

Numerical experiments based on the WRF model were conducted to analyze the structure and evolution of the polar mesoscale cyclone developed over the Kara Sea on September 29-30, 2008. It was found that baroclinic instability in the lower troposphere and convective instability (including that due to the wind-induced surface heat exchange) did not play a significant role. Significant contribution was made by the downward advection of potential vorticity from the upper troposphere and by the conditional instability of second kind. It is demonstrated that if water phase transitions are not taken into account, the mesocyclone intensity is reduced by 7-20% and the time of its development increases by 4 hours. The advection of potential vorticity was not the only process causing the intensification of the lower potential vorticity anomaly associated with cyclonic circulation.     

An Overview of Parameterezations of Heat Transfer over Moss-Covered Surfaces in the Earth System Models

Izvestiya, Atmospheric and Oceanic Physics - Moss cover plays an important role in shaping the thermodynamic and biogeochemical functioning of ecosystems at high latitudes, where it is the dominant...     

Bulk Models of Sheared Boundary Layer Convection

Izvestiya, Atmospheric and Oceanic Physics - This paper discusses approaches to constructing bulk convective boundary layer (CBL) models based on the concept of complete mixing. Large-eddy...     

Study of the development of an extremely high cumulonimbus cloud (Andhra Pradesh, India, September 28, 2004)

Development of a cumulonimbus cloud with its top above 18 km in central India is analyzed. The process is observed with a radar. A 1.5 D numerical model is used to simulate the cloud development. The cloud produced very low radar echo, which implies that large cloud particles were absent. Both observations and simulation show that an extremely intense growth of the cloud was associated with its merge with feeder cells. The seeding of feeder cells caused a change in the direction of the cloud movement.