Annual Snowfall Research Articles

Using spatial interpolation to determine impacts of annual snowfall on traffic crashes for limited access freeway segments

Snowfall affects traffic safety by impacting vehicle performance, driver behavior, and the transportation infrastructure. Depending on intensity snowfall can reduce visibility, pavement friction performance, vehicle stability and maneuverability. Based on this premise, the objective of this study was to use spatial interpolation to analyze the effects of annual snowfall on crash occurrence at non-interchange freeway segment locations in Michigan. Using the geostatistical method of Ordinary Kriging, site specific historical snowfall values were estimated based on data obtained from a series of weather stations during the primary winter months (December, January, and February) for the years of 2004 through 2014 along Michigan’s entire limited access freeway network. These weather data were spatially matched with historical crash data and roadway inventory data for each freeway segment. A Negative Binomial regression model was developed to quantify the effects of snowfall on crashes. Explanatory variables included annual average daily traffic, segment length, horizontal curvature, and snowfall. The results indicated that annual snowfall has a statistically significant positive effect on winter crashes for all types of crashes analyzed. With respect to vehicle type, crashes involving a truck or bus experienced the strongest relationship with annual snowfall. Considering crash severity, property damage crashes possessed a stronger relationship with snowfall as opposed to injury crashes.

Annual discharge trends for Canadian rivers

ABSTRACTThis investigation into trends in annual discharge of Canadian rivers focuses on long-term hydrometric stations having record lengths of at least 75 years. Eliminating stations with significant non-stationarities in mean annual discharge, and stations having evidence of a large diversion or a withdrawal, resulted in a final streamflow dataset of 113 Water Survey of Canada, WSC, hydrometric stations. In order to assist with the identification of potential factors contributing to a trend, at least one representative long-term climate station was selected for each long-term hydrometric station. A comprehensive trend assessment was completed on both annual discharge and precipitation (rainfall, snowfall, and total). Of the 113 long-term hydrometric stations, significant trend was identified at 21 sites: four associated with anthropogenic activities in the watershed, eight consistent with climate change (i.e. changes in annual rainfall, or annual snowfall or annual precipitation) and the remaining nine consistent with some combination of climate and anthropogenic activities. With respect to the climate stations, about 50% had a significant trend in total precipitation without a corresponding significant trend in annual discharge. The ratio of discharge stations with significant trend to climate stations with significant trend varied with ecoregion, from 0% to 40%. Factors contributing to this discrepancy include a possible compensating trend in evapotranspiration and a watershed that is relatively insensitive to small changes in precipitation.

The Importance of Snow Sublimation on a Himalayan Glacier

Snow sublimation is a loss of water from the snowpack to the atmosphere. So far, snow sublimation has remained unquantified in the Himalaya, prohibiting a full understanding of the water balance and glacier mass balance. Hence, we measured surface latent heat fluxes with an eddy covariance system on Yala Glacier (5350 m a.s.l) in the Nepalese Himalaya to quantify the role snow sublimation plays in the water and glacier mass budget. Observations reveal that cumulative sublimation is 32 mm for a 32-day period from October to November 2016, which is high compared to observations in other regions in the world. Multiple turbulent flux parameterizations were subsequently tested against this observed sublimation. The bulk-aerodynamic method offered the best performance, and we subsequently used this method to estimate cumulative sublimation and evaporation at the location of the eddy covariance system for the 2016-2017 winter season, which is 125 and 9 mm respectively. This is equivalent to 21% of the annual snowfall. In addition, the spatial variation of total daily sublimation over Yala Glacier was simulated with the bulk-aerodynamic method for a humid and non-humid day. Required spatial fields of meteorological variables were obtained from high-resolution WRF simulations of the region in combination with field observations. The cumulative daily sublimation at the location of the eddy covariance system equals the simulated sublimation averaged over the entire glacier. Therefore, this location appears to be representative for Yala Glacier sublimation. The spatial distribution of sublimation is primarily controlled by wind speed. Close to the ridge of Yala Glacier cumulative daily sublimation is a factor 1.7 higher than at the location of the eddy covariance system, whereas it is a factor 0.8 lower at the snout of the glacier. This illustrates that the fraction of snowfall returned to the atmosphere may be much higher than 21% at wind-exposed locations. This is a considerable loss of water and illustrates the importance and need to account for sublimation in future hydrological and mass balance studies in the Himalaya.

How Hydrologic Processes Differ Spatially in a Large Basin: Multisite and Multiobjective Modeling in the Tarim River Basin

AbstractWater resources are essential to ecosystems and social economies worldwide, especially in the deserts and oases of the Tarim River Basin, whose water originates largely from alpine mountains characterized by complicated hydrological processes and scarce hydrometeorological observations. This paper presents multisite and multiobjective modeling of hydrological processes in the whole Tarim River Basin, covering 32 catchments in total. The study uses the Soil and Water Assessment Tool, extended by incorporating a degree‐day glacier melt module to enable modeling of glacier melt in the alpine mountains. The multiobjective calibration approach of ε‐Nondominated Sorting Genetic Algorithm‐II was implemented with the two objective functions of the Nash‐Sutcliffe value of daily streamflow and the bias of simulated glacier melt contribution to streamflow. Based on the combined use of the Morris sensitivity technique and hierarchy cluster, the 32 catchments in the study area are divided into six groups according to their dominating hydrological processes, for example, glacier melt, snowmelt, groundwater, and routing. The multiobjective calibration was satisfactory, with 22 of the 32 catchments showing Nash‐Sutcliffe values of daily streamflow larger than 0.6 and the bias of simulated glacier melt contribution to streamflow values smaller than 0.05. Model performance was highly dependent on meteorological data availability, in that low data availability led to poor model performance, while factors such as catchment area and mean annual snowfall had little influence on model performance. The results indicate that multisite and multiobjective calibration enables consistent and comprehensive examination of the spatially different hydrological processes in a large basin and provides information for further assessment of the impact of climate change on water availability.

Controls of Chloride Loading and Impairment at the River Network Scale in New England.

Chloride contamination of rivers due to nonpoint sources is increasing throughout developed temperate regions due to road salt application in winter. We developed a river-network model of chloride loading to watersheds to estimate road salt application rates and investigated the meteorological factors that control riverine impairment by chloride at concentrations above thresholds protective of aquatic organisms. Chloride loading from road salt was simulated in the Merrimack River watershed in New Hampshire, which has gradients in development density. After calibration to a regional network of stream chloride data, the model captured the distribution of regional discharge and chloride observations with efficiencies of 93 and 75%, respectively. The estimate of road salt application is within uncertainties of inventoried estimates of road salt loading and is 122 to 214% greater than recommended targets. Model predictions of chloride showed seasonal variation in chloride concentrations despite a large groundwater storage pool. Interannual variation of mean summer chloride concentration near the outlet varied up to 18%, and the total river length exceeding impairment thresholds varied 12%. Annual snowfall, which drives road salt loading, correlated with chloride impairment only in headwater streams, whereas concentration variability at the outlet was driven primarily by dilution from clean runoff-draining undeveloped forested areas of the watershed. The role of summer meteorology complicates the protection of freshwater systems from chloride contamination.

Climate Trends Impact on the Snowfall Regime in Mediterranean Mountain Areas: Future Scenario Assessment in Sierra Nevada (Spain)

Snow constitutes a key component of the water cycle, which is directly affected by changes in climate. Mountainous regions, especially those located in semiarid environments, are highly vulnerable to shifts from snowfall to rainfall. This study evaluates the influence of future climate scenarios on the snowfall regime in the Sierra Nevada Mountains, an Alpine/Mediterranean climate region in southern Spain. Precipitation and temperature projections from two future climate scenarios representative concentration pathway (RCP) 4.5 and RCP 8.5, Fifth Assessment Report of the Intergovernmental Panel for Climate Change (AR5 IPCC)) were used to estimate the projected evolution of the snowfall regime on both annual and decadal scales during the period of 2006–2100. Specific snowfall descriptors of torrentiality are also analyzed. A general decrease of the annual snowfall was estimated, with a significant trend that ranged from 0.21 to 0.55 (mm·year−1)·year−1. These changes are dependent on the scenario and region in the study area. However, the major impact of future climate scenarios on the snowfall regime relates to an increased torrentiality of snowfall occurrence, with a decreased trend of the annual number of snowfall days (RCP 4.5: −0.068 (days·year−1)·year−1 and RCP 8.5: −0.111 (days·year−1)·year−1) and an increased trend in the annual mean snowfall intensity (RCP 4.5: 0.006 (mm·days−1)·year−1 and RCP8.5: 0.01 (mm·days−1)·year−1)) under both scenarios. This enhanced torrentiality is heterogeneously distributed, with the most semiarid region, which is currently the one least influenced by snow, being the region most affected within the study area.

Quantitative evaluation of glacier change and its response to climate change in the Chinese Tien Shan

Glacier melt water is an important water resource in arid regions of central Asia during the dry seasons, and it is very susceptible to climate disturbances. In this paper, based on the glacier datasets of the first and second Chinese Glacier Inventories, the glacier change in the Chinese Tien Shan from 1960s to 2010 was quantify by assessing the Annual Percentages of Area Changes (APAC), Annual Percentages of Volume Changes (APVC), and Equilibrium Line Altitude (ELA). The results indicated that the mean glacier area and mean glacier volume decreased by 0.7% ± 0.6% per year and 0.83% ± 0.73% per year in the Chinese Tien Shan during the period of 1960–2010, respectively. The mean ELA increased by 24.87 ± 126.84 m during the study period. In addition, we also found that the glacier retreat in the Bogda Mountains was the fastest, mainly due to the sensitivity of small glaciers to climate change, with an APAC of −0.86% ± 0.49% per year and APVC of −1.04% ± 0.55% per year, and the mean ELA increased by 44.35 ± 55.07 m. Moreover, increases in both air temperature (in terms of Thawing Degree-Day (TDD) and Freezing Degree-Day (FDD)) and precipitation were found over the study area during the past five decades. However, such increases in precipitation did not result in any significant changes in the ratio of annual snowfall to total precipitation (S/P) across the Chinese Tien Shan Mountains. Hence, the glacier shrinkage mainly resulted from the significant increase in TDD and FDD in the study region.

CloudSat snowfall estimates over Antarctica and the Southern Ocean: An assessment of independent retrieval methodologies and multi-year snowfall analysis

CloudSat spaceborne radar snowfall retrievals using two different methodologies – the 2C-SNOW-PROFILE (2C-SNOW) CloudSat product and the combined Kulie and Bennartz (2009) technique with the Hiley et al. (2011) reflectivity (Z) to snowfall rate (S) conversion (KBH) - are compared over Antarctica and surrounding Southern Ocean environments. KBH algorithm sensitivity tests are performed to demonstrate how retrievals are affected by algorithm assumptions (e.g., vertical reflectivity continuity test, the choice of near surface bin used to make surface snowfall rate retrievals, and temperature filters). These algorithm components are found to be detrimental to snowfall detection over this region by significantly reducing the snowfall population compared to 2C-SNOW, especially over ocean regions prone to ERA-interim indicated convective snow. After accounting for key algorithm differences, 2C-SNOW mean annual snowfall rates are systematically higher than KBH due to the Z-S relationship adopted. Spatial annual mean snowfall accumulation differences between the two datasets are minimized over interior Antarctica, but large differences are observed over the ocean. 2C-SNOW Z-S relationships for all snowfall events (Z = 10.9 S1.3), over ocean and sea ice (Z = 8.2 S1.3), escarpments and Antarctic coastal areas - below 2000 m a.s.l. (Z = 6.7 S1.4), and Antarctic plateau - above 2000 m a.s.l. (Z = 5.5 S1.6) are also derived. A multi-year 2C-SNOW mean annual snowfall analysis is also provided, and comparisons with ERA-Interim snowfall datasets show similar spatial patterns, but magnitude differences over oceans are observed. A monthly 2C-SNOW and acoustic depth gauge analysis is provided to demonstrate qualitative trends in snowfall accumulation between the respective datasets.

Seasonal variability of shallow cumuliform snowfall: A CloudSat perspective

Cumuliform snowfall seasonal variability is studied using a multi‐year CloudSat snowfall rate and cloud classification retrieval dataset. Microwave radiometer sea ice concentration datasets are also utilized to illustrate the intimate link between oceanic cumuliform snowfall production and decreased sea ice coverage. Three metrics are calculated to illustrate seasonal cumuliform snowfall signatures: (a) cumuliform snowfall frequency of occurrence, (b) mean cumuliform snowfall rate, and (c) fraction of snowfall attributed to cumuliform snowfall events. Distinct seasonal cumuliform snowfall cycles are observed over the Northern Hemispheric oceans. Cumuliform snowfall frequency of occurrence (mean snowfall rate) peaks in months SON (DJF) at most latitudes. Maximum mean cumuliform snowfall rates exceed 300 mm/year in various North Atlantic Ocean locations, with DJF exhibiting the largest areal extent of higher snowfall rates. Cumuliform snow occurrence fraction frequently exceeds 0.5, but regional seasonal sensitivity is observed where transient sea ice coverage exists. Annual snowfall rate fraction attributed to cumuliform snow does not vary appreciably during SON, DJF and MAM north of ∼70°N, but seasonal zonal variability is evident south of this latitudinal threshold. Land cumuliform snowfall features do not universally display strong seasonal signals. Southern Hemisphere seasonal results indicate a strong mean cumuliform snowfall rate maximum (minimum) in JJA (DJF) accompanied by a seasonal latitudinal shift in the snowfall rate peak. Maximum regional snowfall rates exceed 300 mm/year over a broader area compared to the Northern Hemisphere. Cumuliform snowfall production is again strongly linked to seasonal sea ice coverage. Southern Hemispheric cumuliform snowfall occurrence and snowfall rate fraction seasonality is not as obvious as in the Northern Hemisphere, but some latitudinal zones experience ∼5–20% seasonal variability in these quantities. Typical cumuliform snowfall fractions range from 0.4 to 0.6 in the prominent cumuliform snowfall belt covering most of the Southern Ocean. Some subtle seasonal cumuliform snowfall signatures are observed over Antarctica.

Increases in wintertime PM2.5 sodium and chloride linked to snowfall and road salt application

The application of salts and salty brines to roads is common practice during the winter in many urban environments. Road salts can become aerosolized, thereby injecting sodium and chloride particulate matter (PM) into the atmosphere. Here, data from the United States Environmental Protection Agency Chemical Speciation Monitoring Network were used to assess temporal trends of sodium and chloride PM2.5 (PM < 2.5 μm) at 25 locations across the United States to investigate the ubiquity of road salt aerosols. Sodium and chloride PM2.5 concentrations were an average of three times higher in the winter, as compared to the summer, for locations with greater than 25 cm of average annual snowfall. Winter urban chloride PM2.5 concentrations attributed to road salt can even sometimes rival those of coastal sea spray aerosol-influenced sites. In most snow-influenced cities, chloride and sodium PM2.5 concentrations were positively correlated with snowfall; however, this relationship is complicated by differences in state and local winter maintenance practices. This study highlights the ubiquity of road salt aerosols in the United States and their potential impact on wintertime urban air quality, particularly due to the potential for multiphase reactions to liberate chlorine from the particle-phase. Since road salt application is a common practice in wintertime urban environments across the world, it is imperative that road salt application emissions, currently not included in inventories, and its impacts be investigated through measurements and modeling.

Long-term variability and trends in annual snowfall/total precipitation ratio in Finland and the role of atmospheric circulation patterns

This study evaluated variabilities and trends in annual snowfall to total precipitation (S/P) ratio at Sodankylä, Kajaani and Kaisaniemi weather stations in northern, central and southern Finland during 1909–2008. Annual S/P ratio was estimated using daily precipitation and temperature records as input to a calibrated and validated temperature-index snowmelt model developed to simulate snowpack accumulation and melt processes in Finland. Factors controlling variations in annual S/P ratio and their relationships with large-scale atmospheric circulation patterns (ACPs) were also studied. The results show that there were significant declines in annual S/P ratio during 1909–2008, which were principally attributable to century-long decreasing trends in annual snowfall (S) in Finland. These reductions in annual S were predominantly controlled by both annual rainfall (R) and snowfall-day temperature (ST) in the south, annual ST in the centre, and annual R in the north. However, dividing the 100-year study period into an early (1909–1958) and late (1959–2008) periods revealed non-linear trend behaviours in annual S and consequently annual S/P ratio during 1909–2008. The Arctic Oscillation, East Atlantic, East Atlantic/West Russia and Scandinavia patterns were the most influential ACPs for annual S variability.

A Comprehensive Database of Flood Events in the Contiguous United States from 2002 to 2013

Abstract Notwithstanding the rich record of hydrometric observations compiled by the U.S. Geological Survey (USGS) across the contiguous United States (CONUS), flood event catalogs are sparse and incomplete. Available databases or inventories are mostly survey- or report-based, impact oriented, or limited to flash floods. These data do not represent the full range of flood events occurring in CONUS in terms of geographical locations, severity, triggering weather, or basin morphometry. This study describes a comprehensive dataset consisting of more than half a million flood events extracted from 6,301 USGS flow records and radar-rainfall fields from 2002 to 2013, using the characteristic point method. The database features event duration; first- (mass center) and second- (spreading) order moments of both precipitation and flow, flow peak and percentile, event runoff coefficient, base flow, and information on the basin geomorphology. It can support flood modeling, geomorphological and geophysical impact studies, and instantaneous unit hydrograph and risk analyses, among other investigations. Preliminary data analysis conducted in this study shows that the spatial pattern of flood events affected by snowmelt correlates well with the mean annual snowfall accumulation pattern across CONUS, the basin morphometry affects the number of flood events and peak flows, and the concentration time and spreadness of the flood events can be related to the precipitation first- and second-order moments.

Climate change in the Tianshan and northern Kunlun Mountains based on GCM simulation ensemble with Bayesian model averaging

Climate change in mountainous regions has significant impacts on hydrological and ecological systems. This research studied the future temperature, precipitation and snowfall in the 21st century for the Tianshan and northern Kunlun Mountains (TKM) based on the general circulation model (GCM) simulation ensemble from the coupled model intercomparison project phase 5 (CMIP5) under the representative concentration pathway (RCP) lower emission scenario RCP4.5 and higher emission scenario RCP8.5 using the Bayesian model averaging (BMA) technique. Results show that (1) BMA significantly outperformed the simple ensemble analysis and BMA mean matches all the three observed climate variables; (2) at the end of the 21st century (2070–2099) under RCP8.5, compared to the control period (1976–2005), annual mean temperature and mean annual precipitation will rise considerably by 4.8°C and 5.2%, respectively, while mean annual snowfall will dramatically decrease by 26.5%; (3) precipitation will increase in the northern Tianshan region while decrease in the Amu Darya Basin. Snowfall will significantly decrease in the western TKM. Mean annual snowfall fraction will also decrease from 0.56 of 1976–2005 to 0.42 of 2070–2099 under RCP8.5; and (4) snowfall shows a high sensitivity to temperature in autumn and spring while a low sensitivity in winter, with the highest sensitivity values occurring at the edge areas of TKM. The projections mean that flood risk will increase and solid water storage will decrease.

Twenty-Seven Years of Manual Fresh Snowfall Density Measurements on Whistler Mountain, British Columbia

ABSTRACTSnow density is important information for a wide range of activities including avalanche control, marketing, building-code development, weather forecasting, and water supply forecasting. Extended recent high-quality datasets from the mountainous regions of the Pacific Northwest coastal area are rare. This paper presents a study of an unusually long and continuous (January 1990 to April 2016) manually collected dataset of fresh snowfall measurements for Whistler Mountain, British Columbia, Canada. The dataset consists of snowboard core measurements that were collected by Whistler–Blackcomb ski patrol staff twice daily for avalanche control and resort-marketing purposes. These records were collated, transcribed, quality controlled, and made computer accessible in this study. A discussion of the characteristics of the data collection site and an assessment of data reliability are presented. Two examples of the many purposes to which this high-quality dataset might be put were studied. Climatic teleconnections to winter (December–February) mean snow density were examined, which revealed a positive relationship to the quadratic form of the Pacific Decadal Oscillation pattern (i.e., PDO2). In addition, an analysis of daily snow density relationships to air mass types was performed, which suggested that higher (lower) densities are associated with maritime inflow (arctic outflow) conditions. Both of these relationships appear to be mediated by the positive correlation between snow density and air temperature.Based on the full dataset (N = 1275 individual snow density measurements) for all months with measured snowfall, annual snowfall season (November to May) mean snow densities ranged from 77 kg m−3 to 109 kg m−3 with an overall mean of 91 kg m−3, giving an overall snow-depth to water-depth ratio of 11:1.

Towards a rain-dominated Arctic

Arctic precipitation is projected to increase and this study shows that rainfall will become the dominant phase of precipitation, with a decrease in snowfall across all seasons. Climate models project a strong increase in Arctic precipitation over the coming century1, which has been attributed primarily to enhanced surface evaporation associated with sea-ice retreat2. Since the Arctic is still quite cold, especially in winter, it is often (implicitly) assumed that the additional precipitation will fall mostly as snow3. However, little is known about future changes in the distributions of rainfall and snowfall in the Arctic. Here we use 37 state-of-the-art climate models in standardized twenty-first-century (2006–2100) simulations4 to show a decrease in average annual Arctic snowfall (70°–90° N), despite the strong precipitation increase. Rain is projected to become the dominant form of precipitation in the Arctic region (2091–2100), as atmospheric warming causes a greater fraction of snowfall to melt before it reaches the surface, in particular over the North Atlantic and the Barents Sea. The reduction in Arctic snowfall is most pronounced during summer and autumn when temperatures are close to the melting point, but also winter rainfall is found to intensify considerably. Projected (seasonal) trends in rainfall and snowfall will heavily impact Arctic hydrology (for example, river discharge, permafrost melt)5,6,7, climatology (for example, snow, sea-ice albedo and melt)8,9 and ecology (for example, water and food availability)5,10.

The influence of true polar wander on glacial inception in North America

The impact that long-term changes in Earth's rotation axis relative to the surface geography, or true polar wander (TPW), and continental drift have had in driving cooling of high-latitude North America since the Eocene is explored. Recent reanalyses of paleomagnetic pole positions suggest a secular drift in Earth's rotation axis of ∼8° over the last 40 Myr, in a direction that has brought North America to increasingly higher latitudes. Using modern temperature data in tandem with a simple model, a reduction in the annual sum of positive degree days (PDDs) driven by this polar and plate motion over the last 20 Myr is quantified. At sites in Baffin Island, the TPW- and continental drift-driven decrease in insolation forcing over the last 20 Myr rivals changes in insolation forcing caused by variations in Earth's obliquity and precession. Using conservative PDD scaling factors and an annual snowfall equal to modern station observations, the snowiest location in Baffin Island 20 Myr ago had a mass balance deficit of ∼0.75–2 m yr−1 (water equivalent thickness) relative to its projected mass balance at 2.7 Ma. This mass balance deficit would have continued to increase as one goes back in time until ∼40 Myr ago based on adopted paleopole locations. TPW and continental drift that moved Arctic North America poleward would have strongly promoted glacial inception in Baffin Island at ∼3 Ma, a location where the proto-Laurentide Ice Sheet is thought to have originated.

長野県における年降雪量・年最深積雪・冬季降水量の経年変化

長野県における年降雪量・年最深積雪・冬季降水量の経年変化

Precipitation phase separation schemes in the Naqu River basin, eastern Tibetan plateau

Precipitation phase has a profound influence on the hydrological processes in the Naqu River basin, eastern Tibetan plateau. However, there are only six meteorological stations with precipitation phase (rainfall/snowfall/sleet) before 1979 within and around the basin. In order to separate snowfall from precipitation, a new separation scheme with S-shaped curve of snowfall proportion as an exponential function of daily mean temperature was developed. The determinations of critical temperatures in the single/two temperature threshold (STT/TTT2) methods were explored accordingly, and the temperature corresponding to the 50 % snowfall proportion (SP50 temperature) is an efficiently critical temperature for the STT, and two critical temperatures in TTT2 can be determined based on the exponential function and SP50 temperature. Then, different separation schemes were evaluated in separating snowfall from precipitation in the Naqu River basin. The results show that the S-shaped curve methods outperform other separation schemes. Although the STT and TTT2 slightly underestimate and overestimate the snowfall when the temperature is higher and colder than SP50 temperature respectively, the monthly and annual separation snowfalls are generally consistent with the observed snowfalls. On the whole, S-shaped curve methods, STT, and TTT2 perform well in separating snowfall from precipitation with the Pearson correlation coefficient of annual separation snowfall above 0.8 and provide possible approaches to separate the snowfall from precipitation for hydrological modelling.

A Shallow Cumuliform Snowfall Census Using Spaceborne Radar

AbstractThe first observationally based near-global shallow cumuliform snowfall census is undertaken using multiyear CloudSat Cloud Profiling Radar observations. CloudSat snowfall observations and snowfall rate estimates from the CloudSat 2C-Snow Water Content and Snowfall Rate (2C-SNOW-PROFILE) product are partitioned between shallow cumuliform and nimbostratus cloud structures by utilizing coincident cloud category classifications from the CloudSat 2B-Cloud Scenario Classification (2B-CLDCLASS) product. Shallow cumuliform (nimbostratus) snowfall events comprise about 36% (59%) of snowfall events in the CloudSat snowfall dataset. The remaining 5% of snowfall events are distributed between other categories. Distinct oceanic versus continental trends exist between the two major snowfall categories, as shallow cumuliform snow-producing clouds occur predominantly over the oceans. Regional differences are also noted in the partitioned dataset, with over-ocean regions near Greenland, the far North Atlantic Ocean, the Barents Sea, the western Pacific Ocean, the southern Bering Sea, and the Southern Hemispheric pan-oceanic region containing distinct shallow snowfall occurrence maxima exceeding 60%. Certain Northern Hemispheric continental regions also experience frequent shallow cumuliform snowfall events (e.g., inland Russia), as well as some mountainous regions. CloudSat-generated snowfall rates are also partitioned between the two major snowfall categories to illustrate the importance of shallow snow-producing cloud structures to the average annual snowfall. While shallow cumuliform snowfall produces over 50% of the annual estimated surface snowfall flux regionally, about 18% (82%) of global snowfall is attributed to shallow (nimbostratus) snowfall. This foundational spaceborne snowfall study will be utilized for follow-on evaluative studies with independent model, reanalysis, and ground-based observational datasets to characterize respective dataset biases and to better quantify CloudSat snowfall detection and quantitative snowfall estimate uncertainties.

Sub-regional snow cover distribution across the southern Appalachian Mountains

Snowfall in the Southern Appalachian Mountain region of the eastern US is characterized by much spatiotemporal variability. Annual snowfall totals vary by up to 75 cm, and variations in snowfall intensity can lead to large differences in the local snowfall distribution. Research has shown that the synoptic pattern associated with the snowfall strongly influences the regional-scale distribution of snow cover. However, topographic variability results in locally complex snow cover patterns that are not well understood or documented. In this study, we characterize the snow covered area (SCA) and fractional snow cover associated with different synoptic patterns in 14 individual sub-regions. We analyze 63 snow events using Moderate-resolution Imaging Spectroradiometer standard snow cover products to ascertain both qualitative and quantitative differences in snow cover across sub-regions. Among sub-regions, there is significant variation in the snow cover pattern from individual synoptic classes. Furthermore, the percent SCA follows the regional snowfall climatology, and sub-regions with the highest elevations and northerly latitudes exhibit the greatest variability. Results of the sub-regional analysis provide valuable guidance to forecasters by contributing a deeper understanding of local snow cover patterns and their relationship to synoptic-scale circulation features.