Thin Snow Cover Research Articles

Monitoring over‐winter soil water dynamics in a freezing and snow‐covered environment using a thermally insulated tensiometer

AbstractWater potential below a frozen soil layer was continuously monitored over an entire winter period (using thermally insulated tensiometers sheltered in a heated chamber) along with other soil, snow and atmospheric variables. In early winter, the freezing front advanced under a thin snow cover, inducing upward soil water flow in the underlying unfrozen soil. The freezing front started to retreat when the snow cover became thick enough to insulate the soil, resulting in the reversal of the flow direction in the unfrozen zone. These data provide a clear illustration of soil water dynamics, which have rarely been monitored with a tensiometer. Copyright © 2005 John Wiley & Sons, Ltd.

Climate change and winter damage to fruit trees in eastern Canada

Climatic conditions during the cold season represent a serious constraint to fruit production in eastern Canada. Meteorological models predict that temperatures of winter months will increase by 2 to 6°C by 2050. The possible impact of climate change on fruit trees in eastern Canada was assessed using agroclimatic indices expressing the risks associated with known causes of damage during fall, winter, and spring. Indices were calculated for 15 agricultural regions in eastern Canada for recent (1961–1990) and future periods (2010–2039 and 2040–2069) using temperature and precipitation data predicted by the Canadian Global General Circulation Model (CGCMI). Averaged across all agricultural regions, the first fall frost in 2040–2069 would be delayed by 16 d while the last spring frost (≤-2°C) would be advanced by 15 d. By 2040 to 2069, the risks of damage to fruit trees by early winter frosts in eastern Canada are likely to decrease because the shorter photoperiod at the time of the first fall frost would result in a longer hardening period. Milder winter temperatures will also reduce the cold stress as the accumulation of cold degree-days (<-15°C) would be reduced and the annual minimum temperature would be increased in all regions of eastern Canada. More frequent winter thaw events, however, would result in a loss of hardiness and in a thinner snow cover that would increase the plant vulnerability to subsequent extreme sub-freezing temperatures. The risk of damage to flower buds by a late frost would increase in southern Ontario, remain almost unchanged in the Maritimes and Ottawa Valley-southern Québec regions, and decrease in the Continental North. The projected climate change should allow for the introduction of new varieties and species where fruit trees are currently grown and for an extension further north of the commercial production in eastern Canada. Key words: Overwintering, fruit production, climatic indices, winter injury, spring frost

The influence of environmental factors on the supranivean activity of flies (Diptera) in Central Poland

More than half of the insects collected on snow in Central Poland were flies (Diptera). Altogether 83 species of Diptera from 27 families were identified, of which 9 families were recorded for the first time. Two thirds of the Diptera belonged to the Mycetophilidae and Trichoceridae, which were also very species-rich. Other families with many species were the Heleomyzidae, Sphaeroceridae and Phoridae. The peak activity was in the first part of December. Flies were most active on snow when the humidity ranged from 80 to 100%, temperatures between -1 to 5°C and the snow was from 20 to 40 cm deep. The occurrence of Trichoceridae was strictly associated with high humidities, in contrast to Drosophilidae and Heleomyzidae, which were most active at lower humidities. The activity of the flies of the most frequently recorded families was displaced towards either lower (Heleomyzidae and Limoniidae) or higher tem- peratures (Trichoceridae, Mycetophilidae). In contrast to other families, the supranivean activity of Phoridae was strictly associated with thin snow cover.

Adaptation of the Integrated Nitrogen Model for Catchments (INCA) to seasonally snow-covered catchments

Abstract. Testing of the Integrated Nitrogen model for Catchments (INCA) in a wide range of ecosystem types across Europe has shown that the model underestimates N transformation processes to a large extent in northern catchments of Finland and Norway in winter and spring. It is found, and generally assumed, that microbial activity in soils proceeds at low rates at northern latitudes during winter, even at sub-zero temperatures. The INCA model was modified to improve the simulation of N transformation rates in northern catchments, characterised by cold climates and extensive snow accumulation and insulation in winter, by introducing an empirical function to simulate soil temperatures below the seasonal snow pack, and a degree-day model to calculate the depth of the snow pack. The proposed snow-correction factor improved the simulation of soil temperatures at Finnish and Norwegian field sites in winter, although soil temperature was still underestimated during periods with a thin snow cover. Finally, a comparison between the modified INCA version (v.1.7) and the former version (v.1.6) was made at the Simojoki river basin in northern Finland and at Dalelva Brook in northern Norway. The new modules did not imply any significant changes in simulated NO3- concentration levels in the streams but improved the timing of simulated higher concentrations. The inclusion of a modified temperature response function and an empirical snow-correction factor improved the flexibility and applicability of the model for climate effect studies. Keywords: inorganic N leaching, degree-day snow model, snow pack, catchment scale model

Ground thermal profiles from mount kenya, east africa

This paper presents and compares ground thermal regimes at 4200 and 4800 m a.s.l. on Mount Kenya's southern aspect. Temperatures were recorded using Tinytalk™ data loggers, installed at the ground surface and at depths of 1 cm, 5 cm, 10 cm and 50 cm. Temperatures were logged at 2‐hour intervals over a period of 12 months (August 1998 to July 1999). The study is designed to demonstrate near‐surface freeze conditions, which would have implications for contemporary periglacial landform production. Although ground freeze at 4200 m a.s.l. occurs during most nights (c. 70% at 1 cm depth), freeze penetration is restricted to the top 2 to 3 cm, such that no freeze was recorded at 5 cm depth. At 4800 m a.s.l., the diurnal frost frequency at the surface is 365 days (100%), whilst that at 10 cm depth is 165 days (45%). The paper demonstrates that a greater longevity of contemporary thin snow cover at 4800 m a.s.l. permits progressive sub‐surface cooling with depth. However, the near‐surface ground temperature profiles suggest that conditions are not conducive to permafrost development at the sites.

Medieval climate warming and aridity as indicated by multiproxy evidence from the Kola Peninsula, Russia

Data obtained from the low-elevation Khibiny Mountains (ca. 67–68°N; 33–34°E) on the Kola Peninsula, northwest Russia, indicate a period of exceptionally warm and dry conditions commenced at ca. AD 600 and was most pronounced between ca. AD 1000 and 1200. Warmer summer temperatures during this period (coeval with the ‘Medieval Warm Period’ observed in other parts of Europe) are evident in a 100–140 m upward shift in the pine ( Pinus sylvestris L.) limit in the Khibiny Mountains. On average, the cellulose of pine trees that grew between ca. AD 1000 and 1300 is enriched by δ 13C values of around 1‰ compared to the modern trees from the region, further suggesting warmer summer climate than at present. The Medieval Warm Period was also accompanied by a steady decline in avalanche activity and the resulting formation of soils on the current avalanche cones in the Khibiny Mountains, suggesting lower winter precipitation and thinner snow cover. Lower precipitation is also evident by currently submerged tree stumps dating to the medieval period that indicate lower lake levels on the Kola Peninsula. In the middle of the peninsula at about AD 1000, the level of small closed-basin lakes was ∼1 m lower than the modern time at some sites. Drier conditions may be attributable to decreased cyclonic activity. The medieval warm and dry episode was followed at ca. AD 1300 by the development of a colder climate with increased precipitation resulting in a decline in the alpine pine limits, increased avalanche activity, and higher lake levels. That phase corresponds to the modern aeolian episode reconstructed in subarctic Finland. Our results indicate that the Medieval Warm Period on the Kola Peninsula experienced notably warm and dry conditions. Hence, this period of warming extends to northwestern Russia as well as other parts of Europe.

Estimating the distribution of snow water equivalent and snow extent beneath cloud cover in the Salt–Verde River basin, Arizona

AbstractThe temporal and spatial continuity of spatially distributed estimates of snow‐covered area (SCA) are limited by the availability of cloud‐free satellite imagery; this also affects spatial estimates of snow water equivalent (SWE), as SCA can be used to define the extent of snow telemetry (SNOTEL) point SWE interpolation. In order to extend the continuity of these estimates in time and space to areas beneath the cloud cover, gridded temperature data were used to define the spatial domain of SWE interpolation in the Salt–Verde watershed of Arizona. Gridded positive accumulated degree‐days (ADD) and binary SCA (derived from the Advanced Very High Resolution Radiometer (AVHRR)) were used to define a threshold ADD to define the area of snow cover. The optimized threshold ADD increased during snow accumulation periods, reaching a peak at maximum snow extent. The threshold then decreased dramatically during the first time period after peak snow extent owing to the low amount of energy required to melt the thin snow cover at lower elevations. The area having snow cover at this later time was then used to define the area for which SWE interpolation was done. The area simulated to have snow was compared with observed SCA from AVHRR to assess the simulated snow map accuracy. During periods without precipitation, the average commission and omission errors of the optimal technique were 7% and 11% respectively, with a map accuracy of 82%. Average map accuracy decreased to 75% during storm periods, with commission and omission errors equal to 11% and 12% respectively. The analysis shows that temperature data can be used to help estimate the snow extent beneath clouds and therefore improve the spatial and temporal continuity of SCA and SWE products. Copyright © 2004 John Wiley & Sons, Ltd.

Influence of snow cover on wolf Canis lupus predation patterns in Bieszczady Mountains, Poland

Sex, age, bone marrow fat (BMF) content, degree of carcass utilisation and terrain features were analysed for 118 ungulates killed by wolves Canis lupus in the Bieszczady Mountains, Poland, during the winters of 1992–1995 to assess the influence of snow depth on the wolves' predation patterns. In Bieszczady, the snow conditions during the study period were milder than average, with an average total annual snow depth of 1,372 cm and an average snow cover lasting for 94 days. Red deer Cervus elaphus were the primary wolf prey (81%), whereas wild boar Sus scrofa and roe deer Capreolus capreolus were killed less often (9% and 10%, respectively). The majority of prey (74%) was killed in creeks and ravines. The carcass exploitation by wolves was high; of the recovered prey, 55% was more than 60% consumed. The average condition of red deer, as based on BMF, was high (83.4%). BMF varied most among red deer stags and calves, and varied with annual snow depth (N = 29, P < 0.0 1; N = 28, P = 0.09) and monthly mean snow depth (τ = ‐0.37, P < 0.005; τ = ‐0.25, P = 0.06). Wolves killed adult red deer in creeks and ravines with the same frequency regardless of snow depth, whereas calves were killed less often in these places than should be expected from their overall proportion in the sample (N = 95, χ2 = 24.34, P < 0.001). During periods with thinner snow cover, consumption of red deer carcasses was slightly higher than during periods in which the snow cover was deep (τ = ‐0.42, P < 0.045).

Physical control of chlorophyll a, POC, and TPN distributions in the pack ice of the Ross Sea, Antarctica

The pack ice ecosystem of the Ross Sea was investigated along a 1470‐km north‐south transect during the spring 1998 oceanographic program Research on Ocean‐Atmosphere Variability and Ecosystem Response in the Ross Sea (ROAVERRS). Snow and sea ice thickness along the transect varied latitudinally, with thinner snow and ice at the northern ice edge and thin new ice in the vicinity of the Ross Sea polynya. Relative to springtime observations in other sea ice regions, algal chlorophyll a (Chl a) concentrations were low. In contrast, particulate organic carbon (POC), total particulate nitrogen (TPN), and POC:Chl a were all high, indicating either that the ice contained substantial amounts of detritus or nonphotosynthetic organisms, or that the algae had a high POC:Chl a ratio. The abundance of Chl a, POC, and TPN in the sea ice was related to ice age and thickness, as well as to snow depth: older ice had thinner snow cover and contained higher algal biomass while new ice in the polynya had lower biomass. Older pack ice was dominated by diatoms (particularly Fragilariopsis cylindrus) and had vertical distributions of Chl a, POC, and TPN that were related to salinity, with higher biomass at the ice‐water interface. Fluorescence‐based measurements of photosynthetic competence (Fv/Fm) were higher at ice‐water interfaces, and photosynthesis‐irradiance characteristics measured for bottom ice algae were comparable to those measured in pack ice communities of other regions. Nutrient concentrations in extracted sea ice brines showed depletion of silicate and nitrate, depletion or regeneration of phosphate and nitrite, and production of ammonium when normalized to seawater salinity; however, concentrations of dissolved inorganic nitrogen, phosphorous, and silica were typically above levels likely to limit algal growth. In areas where pack ice and snow cover were thickest, light levels could be limiting to algal photosynthesis. Enrichment of δ13C‐POC in the sea ice was correlated with the accumulation of POC, suggesting that carbon sources for photosynthesis might shift in response to decreasing CO2 supply. Comparisons between new ice and underlying waters showed similar algal species dominance (Phaeocystis antarctica) implying incorporation of phytoplankton, with substantially higher POC and TPN concentrations in the ice.

Palaeotemperature reconstructions of the European permafrost zone during marine oxygen isotope Stage 3 compared with climate model results

AbstractA palaeotemperature reconstruction based on periglacial phenomena in Europe north of approximately 51 °N, is compared with high‐resolution regional climate model simulations of the marine oxygen isotope Stage 3 (Stage 3) palaeoclimate. The experiments represent Stage 3 warm (interstadial), Stage 3 cold (stadial) and Last Glacial Maximum climatic conditions. The palaeotemperature reconstruction deviates considerably for the Stage 3 cold climate experiments, with mismatches up to 11 °C for the mean annual air temperature and up to 15 °C for the winter temperature. However, in this reconstruction various factors linking climate and permafrost have not been taken into account. In particular a relatively thin snow cover and high climatic variability of the glacial climate could have influenced temperature limits for ice‐wedge growth. Based on modelling the 0 °C mean annual ground temperature proves to be an appropriate upper temperature limit. Using this limit, mismatches with the Stage 3 cold climate experiments have been reduced but still remain. We therefore assume that the Stage 3 ice wedges were generated during short (decadal time‐scale) intervals of extreme cold climate, below the mean temperatures indicated by the Stage 3 cold climate model simulations. Copyright © 2003 John Wiley & Sons, Ltd.

Low Winter Soil Temperature Affects Summertime Nutrient Uptake Capacity and Growth Rate of Mountain Birch Seedlings in the Subarctic, Swedisn Lapland

Effects of different winter soil temperature on summertime growth rate of individual seedlings of mountain birch (Betula pubescens ssp. czerepanovii) were evaluated in an outdoor pot experiment in subarctic Sweden. The hypothesis tested was that low winter soil temperature could decrease growing-season nutrient uptake capacity and growth rate by injury of the root system; further, the root damage should stimulate growth of replacement roots, which should be reflected by increased summertime biomass allocation to roots. Mountain birch seedlings were exposed to two soil temperatures during wintertime by manipulation of snow depth that accumulated on top of the pots. Minimum soil temperature (hourly recordings) during winter was –1.7°C in the “protected” treatment (deep snow cover) and – 10.5°C in the “exposed” treatment (thin snow cover). The treatments simulated the soil temperature conditions of a local mountain birch forest and heath site, respectively. During June and July, the relative growth rate (RG) and nitrogen accumulation rate (RN) in the exposed treatment were lower compared to the protected treatment. In addition, the seedlings of the exposed treatment allocated a greater proportion of biomass to roots compared to the protected treatment. Thus, leaf growth was reduced in the exposed compared to the protected treatment. We concluded that lower winter temperature in soils can result in stronger root injury that stimulates the growth of replacement roots and reduces nutrient uptake capacity and growth rate during summer. In concert with other possible factors causing root disruption during winter, e.g., frequent freeze-thaw cycles, the mechanism identified here might be important for survival of tree seedlings in subarctic and alpine areas, especially near treelines. The implications are discussed specifically for mountain birch seedling growth and survival in treeless subarctic heath sites and above treelines in northern Europe.

Low Winter Soil Temperature Affects Summertime Nutrient Uptake Capacity and Growth Rate of Mountain Birch Seedlings in the Subarctic, Swedish Lapland

Effects of different winter soil temperature on summertime growth rate of individual seedlings of mountain birch (Betula pubescens ssp. czerepanovii) were evaluated in an outdoor pot experiment in subarctic Sweden. The hypothesis tested was that low winter soil temperature could decrease growing-season nutrient uptake capacity and growth rate by injury of the root system; further, the root damage should stimulate growth of replacement roots, which should be reflected by increased summertime biomass allocation to roots. Mountain birch seedlings were exposed to two soil temperatures during wintertime by manipulation of snow depth that accumulated on top of the pots. Minimum soil temperature (hourly recordings) during winter was –1.7°C in the “protected” treatment (deep snow cover) and – 10.5°C in the “exposed” treatment (thin snow cover). The treatments simulated the soil temperature conditions of a local mountain birch forest and heath site, respectively. During June and July, the relative growth rate (RG) and nitrogen accumulation rate (RN) in the exposed treatment were lower compared to the protected treatment. In addition, the seedlings of the exposed treatment allocated a greater proportion of biomass to roots compared to the protected treatment. Thus, leaf growth was reduced in the exposed compared to the protected treatment. We concluded that lower winter temperature in soils can result in stronger root injury that stimulates the growth of replacement roots and reduces nutrient uptake capacity and growth rate during summer. In concert with other possible factors causing root disruption during winter, e.g., frequent freeze-thaw cycles, the mechanism identified here might be important for survival of tree seedlings in subarctic and alpine areas, especially near treelines. The implications are discussed specifically for mountain birch seedling growth and survival in treeless subarctic heath sites and above treelines in northern Europe.

A new snow cover fraction parametrization for the ECHAM4 GCM

Snow cover fraction (SCF) has a significant influence on the surface albedo and thus on the radiation balance and surface climate. Long-term three dimensional simulations with general circulation models (GCMs) show that the SCF greatly affects the climate in the Northern Hemisphere. By means of both ground observations and remotely sensed data, several deficiencies in the SCF simulated by the current ECHAM4 GCM were identified: over mountainous areas a substantial overestimation in the SCF was found whereas flat areas showed a distinctly underestimated SCF. This work proposes a new parametrization of the SCF for use in GCMs. Evaluations illustrate that it is beneficial to distinguish between the following three terrains: (1) flat, non-forested areas, (2) mountainous regions and (3) forests. The modified SCF parametrization for flat, non-forested areas was derived by using global datasets of ground-based snow depth and remote sensing observations of snow cover data. A 3-dimensional ECHAM4 simulation showed that this modification raises the SCF by up to approximately 20%, mainly in areas with a relatively thin snow cover. The comparison between remotely sensed and simulated mean monthly surface albedo revealed a significant overestimation of the surface albedo in snow-covered mountainous areas. An extension of the current SCF parametrization in ECHAM4 to take into account mountain effects, based on the French climate model Arpege, yielded a close agreement with satellite-derived surface albedo. The adoption of the submodel for snow albedo, as used in the Canadian Land Surface Scheme (CLASS), combined with a newly developed simple snow interception model, demonstrated the ability to capture the main physical processes of snow-covered canopies, including the albedo. The validation of the new parametrization with Boreal Ecosystem-Atmosphere Study (BOREAS) field data showed that the modification is appropriate to capture the main features of the albedo over snow-covered forests during and after heavy snowfall events. Furthermore, the proposed modification has a beneficial impact on the delayed snow melt in spring, a well-known problem in many current GCMs: The simulated surface albedo over the boreal forests decreases by approximately 0.1 during winter and spring, which is in better agreement with ground-based observations. This induces a significant rise in the surface temperature over extended parts of Eurasia and North America in late spring, which subsequently yields a faster snowmelt and an accelerated retreat of the snow line.

Physical properties and isotopic characteristics of landfast sea ice around the North Water (NOW) Polynya region

An ice core sampling program was conducted during the North Water (NOW) Polynya Project 1998 Experiment in northern Baffin Bay during April‐May 1998. The physical properties of snow and sea ice as well as the microstructure and stable isotopic composition of first‐year landfast sea ice near the polynya were investigated. The thickness of sea ice at the sampling sites ranged between 147 and 194 cm with thinner snow cover during the period between mid‐April and late May. The ice was characterized as typical first‐year landfast sea ice, being composed of a thin granular ice layer at the top and an underlying columnar ice layer towards the bottom of the ice. The samples obtained at a site closer to the ice edge of the polynya contained a thin granular ice layer originating from frazil ice near the ice bottom. Formation of frazil ice was considered to be caused by turbulent processes induced by winds, waves and currents forced from the polynya and also mixing with water masses produced at the polynya.

Numerical simulations of the influence of the seasonal snow cover on the occurrence of permafrost at high latitudes

It has repeatedly been reported that snow cover is a dominating factor in determining the presence or absence of permafrost in the discontinuous and sporadic permafrost regions. The temperature at the snow-soil interface by the end of winter, known as the bottom temperature of winter snow (BTS) method, has been used to detect the existence of permafrost in European alpine regions when the maximum snow depth is about 1.0 m or greater. A critical snow thickness of about 50 cm or greater can prevent the development of permafrost in eastern Hudson Bay, Canada. The objective of this study is to investigate the impact of snow cover on the presence or absence of permafrost in cold regions through numerical simulations. A one-dimensional heat transfer model with phase change and a snow cover regime is used to simulate energy exchange between deep soils and the atmosphere. The model has been validated against the in situ data in the Arctic. The simulation results indicate that both snow depth and the onset date of snow cover establishment are important parameters in relation to the presence or absence of permafrost. Early establishment of snow cover can make permafrost disappear, even with a relatively thin snow cover. Permafrost may survive when snow cover starts after the middle of December even with a snow thickness >1.0 m. This effect of snow cover on the ground thermal regime can be explained with reference to the pattern of seasonal temperature variation. Early establishment of snow cover enhances the insulating impact over the entire cold season, thus warming and eventually thawing the permafrost. The insulating effect is substantially reduced when snow cover starts relatively late and snowmelt in the spring creates a huge heat sink, resulting in a favorable combination for permafrost existence.

Temporal evolution of Arctic sea-ice temperature

AbstractVertical profiles of temperature from the air through the snow and ice and into the upper ocean were measured over an annual cycle, from October 1997 to October 1998, as part of a study of the Surface Heat Budget of the Arctic Ocean (SHEBA). These observations were made at nine locations, including young ice, ponded ice, undeformed ice, a hummock, a consolidated ridge and a new blocky ridge. All of the sites had similar environmental forcing, with air temperatures at the different sites typically within 1°C. In general, the seasonal evolution of ice temperature followed a pattern of (1) a cold front propagating down through the ice in the fall, (2) cold ice temperatures and ice growth in late fall, winter and early spring, and (3) warming to the freezing point in the summer. Within this general pattern, there was considerable spatial variability in the temperature profiles, particularly during winter. For example, snow/ice interface temperatures varied by as much as 30°C between sites. The coldest ice temperatures were observed in a consolidated ridge with a thin snow cover, while the warmest were in ponded ice. The warm pond temperatures were a result of two factors: the initial cooling in the fall was retarded by freezing of pond water, and the depressed surface of the pond was quickly covered by a deep layer of snow (0.6 m). In an 8 m thick unconsolidated ridge, the cold front did not penetrate to the ice bottom during winter, and a portion of the interior remained below freezing during the summer. The spatial variability in snow depth and ice conditions can result in situations where there is significant horizontal transport of heat.

Seed production of a masting dwarf shrub, Vaccinium myrtillus, in relation to previous reproduction and weather

In an analysis of a 50-year time series of seed production in bilberry (Vaccinium myrtillus L.) from Aust-Agder, southern Norway, both previous reproduction and weather contributed to explain annual berry production. There was a relatively regular fluctuation in bilberry production, with intervals between peaks of 2-5 years. The bilberry-production index was negatively correlated with the average bilberry production index of the preceding 3 years. Regularity in the bilberry production was commonly interrupted by unfavourable weather conditions. Depressed bilberry reproduction was associated with high temperatures during flower-bud formation in autumn, high temperatures in winters with thin snow cover, low temperatures during flowering in spring, and low or high amounts of precipitation during berry ripening in summer. It was concluded that, in Fennoscandia, climatic conditions may be responsible for the temporal and spatial synchrony in seed production in bilberry.Key words: bilberry, climate, mast, reproduction, synchrony, weather.

Seed production of a masting dwarf shrub, <i>Vaccinium myrtillus</i>, in relation to previous reproduction and weather

In an analysis of a 50-year time series of seed production in bilberry (Vaccinium myrtillus L.) from Aust-Agder, southern Norway, both previous reproduction and weather contributed to explain annual berry production. There was a relatively regular fluctuation in bilberry production, with intervals between peaks of 2-5 years. The bilberry-production index was negatively correlated with the average bilberry production index of the preceding 3 years. Regularity in the bilberry production was commonly interrupted by unfavourable weather conditions. Depressed bilberry reproduction was associated with high temperatures during flower-bud formation in autumn, high temperatures in winters with thin snow cover, low temperatures during flowering in spring, and low or high amounts of precipitation during berry ripening in summer. It was concluded that, in Fennoscandia, climatic conditions may be responsible for the temporal and spatial synchrony in seed production in bilberry.Key words: bilberry, climate, mast, repro...

Golf Green Soil and Crown‐Level Temperatures under Winter Protective Covers

AbstractWinter protective covers are currently used in northern climates to mitigate winter damages on golf greens. Despite the critical importance of soil temperature on winter survival of golf greens, little information exists on the effects of commercially available protective covers on soil temperatures regimes during winter. This 3‐yr (1993–1996) field study was conducted to determine the influence of different winter protective covers on golf green soil temperature under two northern climate conditions (thick or thin snow cover). Six winter protection treatments were tested: permeable covers; impermeable covers; curled wood shavings mat, straw mulch, and 5 cm air space (each under an impermeable cover); and a control treatment without any protection. Daily climatological data and soil temperatures under protective covers were recorded at two experimental sites (Quebec City and St‐Lambert, Montreal, Canada). Throughout the winter seasons, soil temperatures under protective covers and control plots remained around 0°C under a thick and stable snow cover (average of 42 cm during experiment). Under .thin snow cover (average of 6 cm during experiment), minimum crown temperatures were markedly influenced by winter covers and reached a minimum over all years of −20.6, −19.5, −18.2, −11.1, −6.6,and −1.0°C for control, impermeable, permeable, curled wood mat, air space, and straw treatments, respectively. The insulating material covers (curled wood mat, air space, and straw) reduced soil temperature variation ranges, minimized the impact of freezing air temperature and thin snow cover, and consequently enhanced winter survival of golf greens under thin snow cover. Thus, depending on local conditions, and particularly on snow cover, the characteristics of specific protective covers can influence golf green soil temperatures and turfgrass survival during the overwintering period.

The influence of cloud cover on the radiation budget, physical properties, and microwave scattering coefficient (σ°) of first-year and multiyear sea ice

Over sea ice, the shift from predominantly clear conditions in winter to persistent stratus cloud cover in late spring and early summer coincides with a dramatic increase in the net radiation balance at the sea ice surface. Transformation of the boundary layer climate and the geophysical properties of the snow covered sea ice result from this cloud-induced rise in surface energy balance. In this paper, in situ data from the Seasonal Sea Ice Monitoring the Modeling Site (SIMMS'93) experiment are used to examine the extent to which changes in surface radiation, sea ice physical and electrical properties, and microwave scattering are a function of clear versus cloudy conditions over first-year and multiyear sea ice types. The authors use the surface observations to drive a simple forward scattering model used to diagnose the potential mechanisms responsible for the observed changes in microwave scattering by the Earth Resources Satellite-1 (ERS-1). Their results indicate that under cloudy conditions the surface temperature increases because of the surplus in the longwave net radiative energy. This causes an increase in the surface temperature and formation of a temperature wave down through the snow volume into the ice surface. This increases the dielectric constant of the snow basal layer and ice surface over first-year sea ice because of the thin snow cover (relative to the thicker multiyear ice snow cover) and because of the temperature effect on brine volume. The observed increase in scattering is limited to very smooth first-year sea ice types. Models used to diagnose the principal scattering mechanisms suggest that the cloud cover effects the scattering either by creating a dielectrically rough basal layer in the snow volume near the ice surface or by increasing the scattering contribution from snow grains within the basal layer volume. Under either scenario the increase in scattering is small (/spl sim/5 dB) and is only detectable if the target presents a scattering magnitude less than about -20 dB.