Search results for "snow"

2017

Abstract. During free fall in clouds, ice hydrometeors such as snowflakes and ice particles grow effectively by riming, i.e., the accretion of supercooled droplets. Volatile atmospheric trace constituents dissolved in the supercooled droplets may remain in ice during freezing or may be released back to the gas phase. This process is quantified by retention coefficients. Once in the ice phase the trace constituents may be vertically redistributed by scavenging and subsequent precipitation or by evaporation of these ice hydrometeors at high altitudes. Retention coefficients of the most dominant carboxylic acids and aldehydes found in cloud water were investigated in the Mainz vertical wind tu…

Definition of "banner clouds" based on time lapse movies

2007

Abstract. Banner clouds appear on the leeward side of a mountain and resemble a banner or a flag. This article provides a comprehensive definition of "banner clouds". It is based primarily on an extensive collection of time lapse movies, but previous attempts at an explanation of this phenomenon are also taken into account. The following ingredients are considered essential: the cloud must be attached to the mountain but not appear on the windward side; the cloud must originate from condensation of water vapour contained in the air (rather than consist of blowing snow); the cloud must be persistent; and the cloud must not be of convective nature. The definition is illustrated and discussed …

Interannual variability of circulation under spring ice in a boreal lake

2014

A small range (, 1uC) of under-ice water temperature is shown to result in remarkably different circulation regimes under spring ice in a deep, oligotrophic boreal lake. With the water column at , 4uC, melting of snow led to deepening vertical convection before ice break and a final depth of convection inversely correlated with earlier deep-water temperature. We attribute that to the nonlinear dependence of water density on temperature, albeit further affected by stochastic weather factors. In four of nine study years, convection led to complete under-ice overturn of the lake, indicating that this may not be uncommon in similar lakes with steep topography. River inflow and more intensive wa…

COVID-19 and Changes in Social Habits. Restaurant Terraces, a Booming Space in Cities. The Case of Madrid

2021

The COVID-19 pandemic and the fear experienced by some of the population, along with the lack of mobility due to the restrictions imposed, has modified the social behaviour of Spaniards. This has had a significant effect on the hospitality sector, viewed as being an economic and social driver in Spain. From the analysis of data collected in two of our own non-probabilistic surveys (N ~ 8400 and N ~ 2000), we show how, during the first six months of the pandemic, Spaniards notably reduced their consumption in bars and restaurants, also preferring outdoor spaces to spaces inside. The restaurant sector has needed to adapt to this situation and, with the support of the authorities (regional and…

Near Real-Time Modelling of Regional Scale Soil Erosion Using AVHRR and METEOSAT Data: A Tool for Monitoring the Impact of Sediment Yield on the Biod…

2005

List of Contributors. Preface. 1. Spatial Modelling of the Terrestrial Environment: The Coupling of Remote Sensing with Spatial Models (Richard E.J. Kelly, Nicholas A. Drake and Stuart L. Barr). PART I: HYDROLOGICAL APPLICATIONS. Editorial: Spatial Modelling in Hydrology (Richard E.J. Kelly). 2. Modelling Ice Sheet Dynamics with the Aid of Satellite Derived Topography (Jonathan L. Bamber). 3. Using Remote Sensing and Spatial Models to Monitor Snow Depth and Snow Water Equivalent (Richard E. J. Kelly, Alfred T. C. Chang, James L. Foster and Dorothy K. Hall). 4. Using Coupled Land Surface and Microwave Emission Models to Address Issues in Satellite--Based Estimates of Soil Moisture (Eleanor J…

Acidobacteria dominate the active bacterial communities of Arctic tundra with widely divergent winter-time snow accumulation and soil temperatures.

2012

The timing and extent of snow cover is a major controller of soil temperature and hence winter-time microbial activity and plant diversity in Arctic tundra ecosystems. To understand how snow dynamics shape the bacterial communities, we analyzed the bacterial community composition of windswept and snow-accumulating shrub-dominated tundra heaths of northern Finland using DNA- and RNA-based 16S rRNA gene community fingerprinting (terminal restriction fragment polymorphism) and clone library analysis. Members of the Acidobacteria and Proteobacteria dominated the bacterial communities of both windswept and snow-accumulating habitats with the most abundant phylotypes corresponding to subdivision …

The ABCflux database: Arctic-Boreal CO<sub>2</sub> flux observations and ancillary information aggregated to monthly time…

2021

Abstract. Past efforts to synthesize and quantify the magnitude and change in carbon dioxide (CO2) fluxes in terrestrial ecosystems across the rapidly warming Arctic-Boreal Zone (ABZ) have provided valuable information, but were limited in their geographical and temporal coverage. Furthermore, these efforts have been based on data aggregated over varying time periods, often with only minimal site ancillary data, thus limiting their potential to be used in large-scale carbon budget assessments. To bridge these gaps, we developed a standardized monthly database of Arctic-Boreal CO2 fluxes (ABCflux) that aggregates in-situ measurements of terrestrial net ecosystem CO2 exchange and its derived …

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

2003

Abstract Juvenile continental crust of the Arabian–Nubian Shield (ANS) formed within a Neoproterozoic supercontinent cycle. Subsequent late Neoproterozoic deposition overlapped a series of dramatic climatic events that are unparalleled in subsequent Phanerozoic time, as proposed by the “Snowball Earth” hypothesis. In particular, extreme negative δ 13 C excursions coincident with glacial diamictite and cap carbonate sequences imply that profound carbon flux changes accompanied widespread glacial transitions (Snowball Events). Such a succession appears to be partially preserved in metasediments of the diamictite-bearing Tambien Group of northern Ethiopia (Negash syncline). Here, a pronounced …

Night, day, sunrise, sunset: do fish under snow and ice recognize the difference?

2008

1. Although boreal lakes are ice-covered for several months annually, little is known about the behaviour of fish under ice. To consider the reasons for diel vertical migrations (DVM) it is important to compare periods under ice as opposed to under open water. Echosounding provides a tool for non-intrusive continuous monitoring of fish, even in winter. 2. Changes in the vertical distribution of fish through six 48-h periods were monitored using a stationary, mounted echosounder that beamed vertically either from the bottom up or from the surface down from February to April, 2003. The up-beaming and down-beaming transducers were run alternately for 24 h each over the 48-h period. Standard ec…

Effects of hard frost and freeze-thaw cycles on decomposer communities and N mineralisation in boreal forest soil

2003

Abstract Decomposition and mineralisation rates generally increase with increasing moisture and temperature. The expected global climate change may enhance precipitation and raise the temperatures at boreal latitudes, but absence of snow together with occasional low temperatures may cause disturbances in soil processes and faunal communities. To test the effects of disturbances such as hard frosts and freeze-thaw cycles on decomposer populations and N mineralisation, we performed two experiments. In the field experiment, carried out in a pine forest, we induced low soil temperatures by preventing snow covering the ground. In the laboratory test we established three “winter” temperature regi…