Calibration procedure for a daily flow model of small watersheds with snowmelt runoff in the Green River coal region of Colorado /

Mode of access: Internet.

Spring snowmelt and midwinter thaw and refreeze north of 60°N based on Seawinds QuikScat 2000-2009

The scatterometer SeaWinds on QuikSCAT provided regular measurements at Ku-band from 1999 to 2009. Although it was designed for ocean applications, it has been frequently used for the assessment of seasonal snowmelt patterns aside from other terrestrial applications such as ice cap monitoring, phenology and urban mapping. This paper discusses general data characteristics of SeaWinds and reviews relevant change detection algorithms. Depending on the complexity of the method, parameters such as long-term noise and multiple event analyses were incorporated. Temporal averaging is a commonly accepted preprocessing step with consideration of diurnal, multi-day or seasonal averages.

Climate variability over the last 35,000 years recorded in marine and terrestrial archives in the Australian region : an OZ-INTIMATE compilation

The Australian region spans some 60° of latitude and 50° of longitude and displays considerable regional climate variability both today and during the Late Quaternary. A synthesis of marine and terrestrial climate records, combining findings from the Southern Ocean, temperate, tropical and arid zones, identifies a complex response of climate proxies to a background of changing boundary conditions over the last 35,000 years. Climate drivers include the seasonal timing of insolation, greenhouse gas content of the atmosphere, sea level rise and ocean and atmospheric circulation changes. Our compilation finds few climatic events that could be used to construct a climate event stratigraphy for the entire region, limiting the usefulness of this approach. Instead we have taken a spatial approach, looking to discern the patterns of change across the continent. The data identify the clearest and most synchronous climatic response at the time of the Last Glacial Maximum (LGM) (21 ± 3 ka), with unambiguous cooling recorded in the ocean, and evidence of glaciation in the highlands of tropical New Guinea, southeast Australia and Tasmania. Many terrestrial records suggest drier conditions, but with the timing of inferred snowmelt, and changes to the rainfall/runoff relationships, driving higher river discharge at the LGM. In contrast, the deglaciation is a time of considerable south-east to north-west variation across the region. Warming was underway in all regions by 17 ka. Post-glacial sea level rise and its associated regional impacts have played an important role in determining the magnitude and timing of climate response in the north-west of the continent in contrast to the southern latitudes. No evidence for cooling during the Younger Dryas chronozone is evident in the region, but the Antarctic cold reversal clearly occurs south of Australia. The Holocene period is a time of considerable climate variability associated with an intense monsoon in the tropics early in the Holocene, giving way to a weakened monsoon and an increasingly El Niño-dominated ENSO to the present. The influence of ENSO is evident throughout the southeast of Australia, but not the southwest. This climate history provides a template from which to assess the regionality of climate events across Australia and make comparisons beyond our region. The data identify the clearest and most synchronous climatic response at the time of the Last Glacial Maximum (LGM) (21 ± 3 ka), with unambiguous cooling recorded in the ocean, and evidence of glaciation in the highlands of tropical New Guinea, southeast Australia and Tasmania. Many terrestrial records suggest drier conditions, but with the timing of inferred snowmelt, and changes to the rainfall/runoff relationships, driving higher river discharge at the LGM. In contrast, the deglaciation is a time of considerable south-east to north-west variation across the region. Warming was underway in all regions by 17 ka. Post-glacial sea level rise and its associated regional impacts have played an important role in determining the magnitude and timing of climate response in the north-west of the continent in contrast to the southern latitudes. No evidence for cooling during the Younger Dryas chronozone is evident in the region, but the Antarctic cold reversal clearly occurs south of Australia. The Holocene period is a time of considerable climate variability associated with an intense monsoon in the tropics early in the Holocene, giving way to a weakened monsoon and an increasingly El Niño-dominated ENSO to the present. The influence of ENSO is evident throughout the southeast of Australia, but not the southwest. This climate history provides a template from which to assess the regionality of climate events across Australia and make comparisons beyond our region.

Lumen sulamisesta ja sulamiskauden vesitaseesta Lammin Pääjärvellä 1970-72

English summary: On snowmelt and water balance during snowmelt period in Pääjärvi representative basin in 1970-72

Overwintering ecology of northern field layer plants : snow and photosynthesis in Vaccinium vitis-idaea L.

Winter is a significant period for the seasonality of northern plants, but is often overlooked when studying the interactions of plants and their environment. This study focuses on the effects of overwintering conditions, including warm winter periods, snow, and snowmelt on boreal and sub-Arctic field layer plants. Wintertime photosynthesis and related physiological factors of evergreen dwarf shrubs, particularly of Vaccinium vitis-idaea, are emphasised. The work combines experiments both in the field and in growth chambers with measurements in natural field conditions. Evergreen dwarf shrubs are predominantly covered by snow in the winter. The protective snow cover provides favourable conditions for photosynthesis, especially during the spring before snowmelt. The results of this study indicate that photosynthesis occurs under the snow in V. vitis-idaea. The light response of photosynthesis determined in field conditions during the period of snow cover shows that positive net CO2 exchange is possible under the snow in the prevailing light and temperature. Photosynthetic capacity increases readily during warm periods in winter and the plants are thus able to replenish carbohydrate reserves lost through respiration. Exposure to low temperatures in combination with high light following early snowmelt can set back photosynthesis as sustained photoprotective measures are activated and photodamage begins to build up. Freezing may further decrease the photosynthetic capacity. The small-scale distribution of many field layer plants, including V. vitis-idaea and other dwarf shrubs, correlates with the snow distribution in a forest. The results of this study indicate that there are species-specific differences in the snow depth affinity of the field and ground layer species. Events and processes taking place in winter can have a profound effect on the overall performance of plants and on the interactions between plants and their environment. Understanding the processes involved in the overwintering of plants is increasingly important as the wintertime climate in the north is predicted to change in the future.

Monitoring of seasonal snow cover in Bhutan using remote sensing technique

All major rivers in Bhutan depend on snowmelt for discharge. Therefore, changes in snow cover due to climate change can influence distribution and availability of water. However, information about distribution of seasonal snow cover in Bhutan is not available. The MODIS snow product was used to study snow cover status and trends in Bhutan. Average snow cover area (SCA) of Bhutan estimated for the period 2002 to 2010 was 9030 sq. km, about 25.5% of the total land area. SCA trend of Bhutan for the period 2002-2010 was found to decrease (-3.27 +/- 1.28%). The average SCA for winter was 14,485 sq. km (37.7%), for spring 7411 sq. km (19.3%), for summer 4326 sq. km (11.2%), and for autumn 7788 sq. km (20.2%), mostly distributed in the elevation range 2500-6000 m amsl. Interannual and seasonal SCA trend both showed a decline, although it was not statistically significant for all sub-basins. Pho Chu sub-basin with 19.5% of the total average SCA had the highest average SCA. The rate of increase of SCA for every 100 m elevation was the highest (2.5%) in the Pa Chu sub-basin. The coefficient of variance of 1.27 indicates high variability of SCA in winter.

Missing (in-situ) snow cover data hampers climate change and runoff studies in the Greater Himalayas

The Himalayas are presently holding the largest ice masses outside the polar regions and thus (temporarily) store important freshwater resources. In contrast to the contemplation of glaciers, the role of runoff from snow cover has received comparably little attention in the past, although (i) its contribution is thought to be at least equally or even more important than that of ice melt in many Himalayan catchments and (ii) climate change is expected to have widespread and significant consequences on snowmelt runoff. Here, we show that change assessment of snowmelt runoff and its timing is not as straightforward as often postulated, mainly as larger partial pressure of H2O, CO2, CH4, and other greenhouse gases might increase net long-wave input for snowmelt quite significantly in a future atmosphere. In addition, changes in the short-wave energy balance such as the pollution of the snow cover through black carbon or the sensible or latent heat contribution to snowmelt are likely to alter future snowmelt and runoff characteristics as well. For the assessment of snow cover extent and depletion, but also for its monitoring over the extremely large areas of the Himalayas, remote sensing has been used in the past and is likely to become even more important in the future. However, for the calibration and validation of remotely-sensed data, and even-more so in light of possible changes in snow-cover energy balance, we strongly call for more in-situ measurements across the Himalayas, in particular for daily data on new snow and snow cover water equivalent, or the respective energy balance components. Moreover, data should be made accessible to the scientific community, so that the latter can more accurately estimate climate change impacts on Himalayan snow cover and possible consequences thereof on runoff. (C) 2013 Elsevier B.V. All rights reserved.

Of plants and pikas: evidence for a climate-mediated decline in forage and cache quality

Background: Animals that hoard food to mediate seasonal deficits in resource availability might be particularly vulnerable to climate-mediated reductions in the quality and accessibility of food during the caching season. Central-place foragers might be additionally impacted by climatic constraints on their already restricted foraging range. Aims: We sought evidence for these patterns in a study of the American pika (Ochotona princeps), a territorial, central-place forager sensitive to climate. Methods: Pika food caches and available forage were re-sampled using historical methods at two long-term study sites, to quantify changes over two decades. Taxa that changed in availability or use were analysed for primary and secondary metabolites. Results: Both sites trended towards warmer summers, and snowmelt trended earlier at the lower latitude site. Graminoid cover increased at each site, and caching trends appeared to reflect available forage rather than primary metabolites. Pikas at the lower latitude site preferred species higher in secondary metabolites, known to provide higher-nutrient winter forage. However, caching of lower-nutrient graminoids increased in proportion with graminoid availability at that site. Conclusions: If our results represent trends in climate, cache quality and available forage, we predict that pikas at the lower latitude site will soon face nutritional deficiencies.

Modeling the effect of snow on seasonal runoff within the Truckee River drainage basin

EXTRACT (SEE PDF FOR FULL ABSTRACT): We estimate monthly runoff for a 2-dimensional solution domain containing those areas tributary to Pyramid Lake, Nevada (the Truckee River drainage basin) at a 1-kilometer grid cell spacing. ... To calculate the effect of snow on the hydrologic system, we perform two experiments. In the first we assume that all precipitation falls as rain; in the second we assume that some precipitation falls as snow, thus available water is a combination of rain and snowmelt. We find that considering the effect of snow results in a more accurate representation of mean monthly flow rates, in particular the peak flow during the melt season in the Sierra Nevada. These preliminary results indicate that a relatively simple snow model can improve the representation of Truckee River basin hydrology, significantly reducing errors in modeled seasonal runoff.

The top ten California floods of the 20th century

The purpose of this paper is to summarize the biggest northern California floods of the 20th century. Flooding in California can occur from different causes. At least three types of floods occur: 1. Winter general floods, which cover a large area. 2. Spring and early summer snowmelt floods unique to the higher-elevation central and southern Sierra Nevada, which occur about once in 10 years on the average. 3. Local floods from strong thunderstorms, with intense rain over a relatively small area. These originate in moist tropical or subtropical air and include the flash floods of the desert and other areas of southern California when remnants of eastern Pacific hurricanes get carried into the state.

青藏高原东部植物生态特征在季节性雪厚度梯度上的变化

本文以青藏高原东部的高山草甸为研究对象，设置早融、中间及晚融三个融雪部位，采用实验室测量、野外测量、野外样方调查相结合的 方法，从个体、种群和群落的水平上比较研究了高山雪场植物在同一雪场样地中不同融雪梯度上的特征变异及适应，结果表明： 从早融到晚融的梯度上，随着融雪时间的逐渐推迟，表土日温差降低，冻融交替的强度减弱，土壤水份逐渐增加，总N、总P、总K 以及 可溶性的N、P 和pH 变化不明显，土壤有机质及可溶性的K 和Ca 逐渐降低。冻融交替强度上的差异以及土壤水分差异被认为是融雪梯度上 影响植物生长的主要原因。 从早融到晚融的梯度上，伴随着生态因子的改变，几种常见植物的个体特征也发生相应的变化。首先，物候期推迟。植物开始生长的时间 一般要推迟将近二十天，但同一种植物在不同的融雪部位上的衰老期趋于一致，这预示着在晚融部位同一植物的生长期要缩短。其次，个体生 长特性发生改变。黑褐穗苔草（Carex atrofusca subsp. minor (Boott) T.Koyama）和西北黄芪（Astragalus fenzelianus Pet.-Stib.）的个体生长（株高、单株叶数、单叶面积和地上生物量）表现为逐渐增加的趋势；斑唇马先蒿（Pedicularis longiflora Rudolph var. tubiformis (Klotz.) Tsoong）和川西小黄菊（Pyrethrum tatsienense (Bur. et Franch.) Ling ex Shih.）则表现为逐渐降低的趋势；长叶火绒草（Leontopodium longifolium Ling）在融雪梯度上的变化趋势不明显。再次，从繁殖特性来看，大卫马先蒿（Pedicularis davidii var. pentodon Tsoong）的单株花数、单花种子数、种子千粒重及种子萌发率随融雪的推迟呈现为逐渐增加的趋势；圆穗蓼（Polygonum macrophyllum D.Don）的种子（小坚果）千粒重和萌发率也表现为逐渐增加，其余繁殖特征变化不明显。 在种群层次上，几个常见物种的分布格局随着融雪的推迟都发生一定的变化，基本上表现为从早融的集群分布到中间或晚融部位的随机分布。物种间的联结性也发生较大的变化，由早融部位的总体上的正关联逐步过度到晚融部位上的总体上的负关联。特定种对间的联结性也发生较大的变化。恶劣环境条件（如剧烈的冻融交替）的影响以及对恶劣条件适应被认为是分布格局及种间联结性发生变化的主要原因。 在群落层次上，物种多样性的变化表现为单峰曲线的格局，即在中间部位多样性最高。早融部位强烈的冻融交替和晚融部位缩短的生长季是早融及晚融部位物种多样性不高的重要原因。几乎所有的只出现在一个融雪部位（雪深级别）上的物种都发生在中间融雪部位。这说明，中等的雪深更有利于许多高山植物的存活，而过浅过深的积雪都不利于植物的生存。另外，相距较近的融雪梯度之间的物种相似性较大，而相距较远的梯度之间物种的替代率较高，物种的相似性较小。在群落的生物量方面，地上生物量随融雪的推迟而升高，地下生物量随融雪的推迟而下降，地上与地下生物量之总和随着融雪的推迟而下降，地下生物量与地上生物量之比随着融雪的推迟而下降。早融部位的地上生物量主要集中于地上0-10cm 的范围内，表明在早融部位植物地上部分有变矮的趋势；早融部位的地下生物量在土壤各深度分布相对较均一，而晚融部位地下生物量则主要集中于地下0-10cm 的范围内。生物量的变化趋势主要与雪场中各部位的土壤水分含量及地表日温度差异有关，是植物适应特定环境的结果。 To detect the plants’ responses to snow-cover gradients in an alpine meadow of eastern Tibetan plateau, laboratory method and field sample plot method were employed, and three gradeients （early-, medium and late-melting）were established in a natural snowbed. The measurements were carried out for two years and was done on three levels——individual, population and community. The results are shown as follows : From early- to late-melting gradients, daily ground temperature difference between day and night decreased, amplitude of freeze-thaw alternation weakened, soil organic matter contents and soluble K and Ca decreased, while soil water content increased. Total N, total P, total K，pH soluble N and soluble P kept constant from early- to late-melting portions. Among these factors, the changes of intense freeze-thaw alternation and soil water contents were considered as main factors affecting plants’ growth. From early- to late-melting portions, all phenological phases postponed, e.g. phase of plant emergence postponed almost twenty days. However, the same species’ individuals at different portions withered in step, which implied that the individuals at late-melting portion possessed shorter growing season length. Along the same gradient, both Carex atrofusca subsp. minor (Boott) T. Koyama and Astragalus fenzelianus Pet.-Stib. increased their individual growth, whereas Pedicularis longiflora Rudolph var. tubiformis (Klotz.) Tsoong and Pyrethrum tatsienense (Bur. et Franch.) Ling ex Shih. decreased their individual growth. Unlike the four plants mentioned above, Leontopodium longifolium L. did not show any evident change. As to reproductive charateristics, the flowers per individual, the number of seeds per flower, the thousand seed weight and the seed germination rate of Pedicularis davidii var. pentodon showed an increasing trend; and Polygonum macrophyllum D.Don also increased its thousand seed weight and seed germination rate along the same gradient. However, the other reproductive charateristics of Polygonum macrophyllum D.Don did not change significantly. At population level, the distribution pattern of several selected species changed from cluster pattern to random pattern as the snowmelt postponed. Overall association among the species changed from positive to negative along the same gradient. Further, interspecific association also changed evidently. Adverse circumstances such as intense freeze-thaw alternation were considered as primary factors resulting in changes of population distribution pattern and interspecific association. At the level of community, species diversity showed a pattern of a unimodal trend, i.e. the highest diversity occurred at medium snow depth，perhaps because of intense freeze-thaw alternation at early-melting portions and the shortest growing season at late-melting portions. Almost all species that only appeared at one snowmelt portion occurred at medium portion, indicating that medium snow depth was more suitable for many species’ survival. Species replacement from one snowmelt portion to its neighboring portion seldom took place. However, while distance between two portions became farther, species replacement between the two portions occurred more frequently. As for biomass, aboveground biomass increased from early- to late-melting portions, whereas belowground biomass, total biomass and the ratio of belowground to aboveground all decreased along the same snow gradient. A majority of aboveground biomass distributed in a height range of 0-10 cm, suggesting that height of plants inhabiting early-melting portion be shorter compared with other portions. In addition, belowground biomass at early-melting portion was evenly distributed at different soil depth in comparison with aboveground biomass, whereas belowground biomass at late-melting portion concentrated 0-10cm soil layer below ground. The changing trend of biomass was also related to two factors. One was soil water content, and the other topsoil temperature difference between day and night.

Sublimation of snow from confierous forests in a climate model

Essery, R L H, Pomeroy, J W, Parvianen, J & Storck, P, Sublimation of snow from confierous forests in a climate model. Journal of Climate 16, pp 1855-1864 (2003).

Boundary layer growth and advection of heat over snow and soil patches: Modelling and parametrization

Essery, RLH, RJ Granger and JW Pomeroy, 2006. Boundary layer growth and advection of heat over snow and soil patches: Modelling and parametrization. Hydrological Processes, 20, 953 - 967.

Design and Evaluation of a Retrofittable Electric Snow Melting System for Pavements

Gemstone Team SnowMelt

Long-term hydroclimatic change and interannual variability in water sources, Apex River (Iqaluit), Baffin Island, Nunavut

The eastern Canadian Arctic is home to Canada’s largest Indigenous population, which depends on local freshwater sources for drinking water. However, small watersheds have rarely been analyzed for long-term hydrologic response to changing climate. This study aims to address this issue by examining the Apex River, a small watershed with a long hydroclimatic record, near Iqaluit, Nunavut. Particular emphasis was placed on the long-term changes in climate and river discharge, and the seasonal variability of water sources between two snapshots in time, 1983 and 2013. Long-term hydrological data were obtained from gauge station 10UH002, operated by Environment and Climate Change Canada, and long-term meteorological data were acquired from Environment Canada–operated stations near Iqaluit Airport. Breakpoint analysis suggested that long-term mean annual surface air temperatures have increased since 1994. In contrast, no long-term total precipitation or annual discharge changes were observed. However, river flow initiation and cessation analyses of the Apex River flow season indicates that flow extended into the autumn since the 2000s. The 2013 flow season lasted 44 days longer than the 1983 flow season. Systematic river sampling was undertaken throughout the 2013 thaw season to determine contributing proportions of event (snowmelt or rainfall) and pre-event (baseflow) water to river runoff. Results from the stable isotope hydrograph separation for 2013 were compared to findings for 1983. Snow was the main source of water to the river during the snowmelt period in 1983 and 2013, however baseflow was still an important contributor. Although there was high similarity of water sources early in the season in 1983 and 2013, the two years differed during the autumn. In 2013 there was a high rainfall runoff response that was not present in 1983, suggesting high release of late-season sub-surface water storage and an increased sensitivity to late-season rainfall events in 2013. This research provides insights into the hydrologic response of the Apex River to long-term climatic change, and highlights the need for high-quality precipitation and discharge data for effective long-term hydrological assessment.