Amount Of Snowfall Research Articles

영동지역 대설 사례의 대기 하층 안정도 분석

Extreme heavy snowfall episodes have been investigated in case of accumulated snowfall amount larger than 50 cm during the past ten years, in order to understand the association of low-level stability with heavy snowfall in the Yeongdong region. In general, the selected 4 events have similar synoptic setting such as the Siberian High extended to East Sea along with the Low passing by the southern Korean Peninsula, eventually inducing easterly in the Yeongdong region. Specifically moist-adiabatically neutral layer has been observed during the heavy snowfall period, which was easily identified using vertical profiles of equivalent potential temperature observed at Sokcho, whereas convective unstable layer has been formed over the East sea due to relatively warm sea surface temperature (SST) about and lower temperature around 1~2 km above the surface, obtained from RDAPS. Difference of equivalent potential temperature between 850 hPa and surface as well as difference between air and sea temperatures altogether gradually increased before the snowfall period. Instability-induced moisture supply to the atmosphere from the East sea, being cooled and saturated by the upper cold surge, would make low-level ice cloud, and eventually move inland by the easterly flow. Heavy snowfall will be enhanced in association with low-level convergence by surface friction and upslope wind against Taebaek mountains. This study emphasizes the importance of low level stability in the Yeongdong region using the radiosonde sounding and RDAPS data, which should quantitatively be examined through numerical model as well as heat and moisture supply from the ocean.

Factors controlling diurnal variation in the isotopic composition of atmospheric water vapour observed in the taiga, eastern Siberia

Deciduous forest covers vast areas of permafrost under severe dry climate in eastern Siberia. Understanding the water cycle in this forest ecosystem is quite important for climate projection. In this study, diurnal variations in isotopic compositions of atmospheric water vapour were observed in eastern Siberia with isotope analyses of precipitation, sap water of larch trees, soil water, and water in surface organic layer during the late summer periods of 2006, 2007, and 2008. In these years, the soil moisture content was considerably high due to unusually large amounts of summer rainfall and winter snowfall. The observed sap water δ18O ranged from −17.9‰ to −13.3‰, which was close to that of summer precipitation and soil water in the shallow layer, and represents that of transpired water vapour. On sunny days, as the air temperature and mixing ratio rose from predawn to morning, the atmospheric water vapour δ18O increased by 1‰ to 5‰ and then decreased by about 2‰ from morning to afternoon with the mixing ratio. On cloudy days, by contrast, the afternoon decrease in δ18O and the mixing ratio was not observed. These results show that water vapour that transpired from plants, with higher δ18O than the atmospheric water vapour, contributes to the increase in δ18O in the morning, whereas water vapour in the free atmosphere, with lower δ18O, contributes to the decrease in the afternoon on sunny days. The observed results reveal the significance of transpired water vapour, with relatively high δ18O, in the water cycle on a short diurnal time scale and confirm the importance of the recycling of precipitation through transpiration in continental forest environments such as the eastern Siberian taiga. Copyright © 2012 John Wiley & Sons, Ltd.

Effects of seasonal cycle fluctuations in an A1B scenario over the Euro-Mediterranean region

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 52:135-157 (2012) - DOI: https://doi.org/10.3354/cr01037 Contribution to the CR Special: 'The regional climate model RegCM4' Effects of seasonal cycle fluctuations in an A1B scenario over the Euro-Mediterranean region Alessandro Dell’Aquila, Sandro Calmanti*, Paolo Ruti, Maria Vittoria Struglia, Giovanna Pisacane, Adriana Carillo, Gianmaria Sannino Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Energy & Environment Modeling Unit Climate & Impact Modeling Laboratory (UTMEA-CLIM), CR Casaccia, Via Anguillarese 30, 100123 Santa Maria di Galeria, Rome, Italy *Email: sandro.calmanti@enea.it ABSTRACT: We analysed the downscaling of an A1B scenario simulation for the Euro-Mediterranean area performed with a regional earth system model by focusing on long-term variations in the seasonal cycle of key impact indicators (surface temperature, hydrological cycle). The output of the regional model was compared with the driving global simulation (ECHAM5/MPI-OM) and with available observations. Our objective was to highlight the potential additional information end-users may access by using a high-resolution regional coupled system in place of the corresponding coarser global driver. In the regional downscaling, the large sea surface temperature (SST) bias simulated by the global driver is partially reduced, and SST spatial patterns are in better agreement with those observed in the reference climatology, thereby supporting the tenet that coupling the atmosphere with a high-resolution interactive ocean over small areas characterized by complex orography may improve specific aspects of regional climate modelling. A more accurate description of orography produces in the regional model a narrower identification of the effects of a warmer climate on intense precipitation events and on other key environmental indicators, such as the extension of snow cover and the aridity index. An example of the effect of climate variability on river discharge is also presented for a medium/small catchment basin in northern Italy, the Po River, which responds both to variations in rainfall rates and to the amount of snowfall over the Alps. In contrast with the gross underestimation of the global driver, regional simulation produces a reasonable estimate of the observed average discharge (1500 m3 s−1) and of its seasonal variability, which provides a reliable baseline for societal impact studies. KEY WORDS: Mediterranean · Regional climate · Scenario · Sea surface temperature · Hydrological cycle Full text in pdf format PreviousNextCite this article as: Dell’Aquila A, Calmanti S, Ruti P, Struglia MV, Pisacane G, Carillo A, Sannino G (2012) Effects of seasonal cycle fluctuations in an A1B scenario over the Euro-Mediterranean region. Clim Res 52:135-157. https://doi.org/10.3354/cr01037 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 52. Online publication date: March 22, 2012 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2012 Inter-Research.

Fungal communities at the edge: Ecological lessons from high alpine fungi

Abstract One of the least studied ecosystems on Earth is the plant-free zone found between the alpine tundra zone and the zone of permanent ice and snow. This unique ecosystem-type occurs in all of the major mountain ranges on Earth and is especially widespread in the Andes and Himalayas. Here we describe recent molecular-phylogenetic studies of the fungi that inhabit these apparently barren soils. Sites that receive significant amounts of snowfall (in the Himalayas, Rocky and Andes ranges) are dominated by unique clades of zoosporic fungi (especially the Spizellomycetales), which likely use the saturated soil conditions during snow melt to complete their life cycles and then remain dormant for most of the year during periods of extreme cold and dryness. In more extreme sites that have very sporadic and shallow snow packs, such as the upper slopes of Llullaillaco Volcano (el. 6 741 m above sea level) on the Chilean-Argentinian border, fungal communities show very little diversity and are dominated by clades of yeasts related to the Antarctic endolithic yeasts in the Filobasidiales group. The other major group found on Llullaillaco form a clade most closely affiliated with the Dothideomycetes. Overall, our phylogenetic approach and spatially explicit sampling scheme allow us to formulate new hypotheses about the ecological functioning of fungi that inhabit critically endangered high elevation ecosystems.

Spatial snowfall distribution in mountainous areas estimated with a snow model and satellite remote sensing

We describe an approach for reconstructing snowfall that combines satellite observations of the snow disappearance date (SDD) with a snow model for two mountainous areas in Japan having distinct snow climatology. This approach allows assessment of the distribution of snow and topographical effects on snowfall within a catchment. We also evaluated how the reconstructed snowfall affects the catchment snow hydrology. Validation at observation sites demonstrated that a combination of the snow model and snowfall reconstructions successfully estimated the seasonal changes of snow water equivalent (SWE). In Japan, the dependence of snowfall on elevation is stronger in mountainous areas along the coast on the Sea of Japan side of Japan’s central mountain spine (where snowfall triples with every 1000 m increase in elevation; Csf = 0.002 m−1) compared with inland locations of the same region (where snowfall doubles with every 1000 m increase; Csf = 0.001 m−1). Moreover, the reconstructed snowfall improved the estimation of maximum catchment SWE. Maximum total SWE, estimated with reconstructed snowfall, was 3.8 × 108 m3 in Kurobe catchment (along the coast on the Sea of Japan side of Japan’s central mountain spine), while that, estimated by convectional method with the spatially-constant Csf = 0.001 m−1, was 2.0 × 108 m3. As a result, estimations of the snow disappearance date and of the catchment snowmelt were also improved. These results suggest that it is useful to estimate the spatial snow distribution, especially where steep topography causes large gradients of snowfall amount with respect to elevation.

Long-term variability of occurrence of precipitation forms in winter in Kraków, Poland

The paper discusses long-term change in snowfall, rainfall and mixed precipitation viewed in conjunction with air temperature and North Atlantic Oscillation (NAO) in winter (December–February). In the study of contemporary climate change and its effect on the hydrological cycle it is useful to focus on winter precipitation forms. A 146-year secular observation series from Krakow, spanning the period 1863–2008, was used to extract data on the number of days with precipitation and on precipitation amount broken down by form. Statistically significant trends were found in total and mixed precipitation, but not in snowfall and rainfall. The climate warming effect has contributed to a material decrease in the snowfall to total winter precipitation ratio during the second half of the 20th c. The highest impact of air temperature was found in the wintertime variation in number of days with snowfall while the NAO had a significant influence on the frequency and amount of both rainfall and snowfall.

High-Resolution Simulations of Wintertime Precipitation in the Colorado Headwaters Region: Sensitivity to Physics Parameterizations

Abstract An investigation was conducted on the effects of various physics parameterizations on wintertime precipitation predictions using a high-resolution regional climate model. The objective was to evaluate the sensitivity of cold-season mountainous snowfall to cloud microphysics schemes, planetary boundary layer (PBL) schemes, land surface schemes, and radiative transfer schemes at a 4-km grid spacing applicable to the next generation of regional climate models. The results indicated that orographically enhanced precipitation was highly sensitive to cloud microphysics parameterizations. Of the tested 7 parameterizations, 2 schemes clearly outperformed the others that overpredicted the snowfall amount by as much as ~30%–60% on the basis of snow telemetry observations. Significant differences among these schemes were apparent in domain averages, spatial distributions of hydrometeors, latent heating profiles, and cloud fields. In comparison, model results showed relatively weak dependency on the land surface, PBL, and radiation schemes, roughly in the order of decreasing level of sensitivity.

Air and Ground Temperature Variations Observed along Elevation and Continentality Gradients in Southern Norway

ABSTRACTThe coupling between air and ground temperatures in the mountains of southern Norway was examined using 12 shallow boreholes drilled in August 2008. Three borehole arrays (at Juvvass, Jetta and Tron), each with boreholes at different elevations, were established along a continentality gradient. At the least continental site (Juvvass), the transect includes boreholes with shallow seasonal frost to continuous permafrost, while at Jetta and Tron, the arrays covered the transition from relatively deep seasonal frost to marginal permafrost. On the north slope of Tron, however, ground surface temperatures indicate more widespread permafrost conditions, apparently due to the negative thermal anomaly associated with an openwork block field. The surface offsets (mean ground surface temperature (MGST) minus mean air temperature (MAT)) ranged from < 1 °C for unvegetated wind‐scoured sites to up to 4.5 °C for sites with a thick, prolonged snow cover. Active‐layer thicknesses at the borehole sites close to the lower limit of mountain permafrost were up to 10 m in bedrock, even under a low thermal diffusivity sediment cover. The mean ground temperature at 10‐m depth differed significantly from the MGST, mainly due to the 3D thermal effects of the varying snow cover. Our air temperature measurements do not support the inference that the observed decrease in the lower elevational limit of mountain permafrost with continentality is mainly due to lower MAT. Rather, the pattern fits with an eastwards decrease in the lower limit of block fields and snowfall amounts. Copyright © 2011 John Wiley & Sons, Ltd.

기후변화 시나리오를 이용한 미래의 강설량 예측

Due to emissions of greenhouse gases caused by increased use of fossil fuels, the climate change has been detected and this phenomenon would affect even larger 2011년 7월 23일 접수 Received on July 23, 2011 / 2011년 8월 31일 수정 Revised on August 31, 2011 / 2011년 9월 14일 심사완료 Accepted on September 14, 2011 * 본 연구는 2010년도 정부(교육과학기술부)의 재원으로 한국연구재단(No. 2010-0029194)의 지원을 받아 수행되었음. 1 건국대학교 사회환경시스템공학과 Dept. of Civil and Env. System Eng, Konkuk University ※ 연락저자 E-mail : kimsj@konkuk.ac.kr 기후변화 시나리오를 이용한 미래의 강설량 예측 / 조형경.김샛별.정샛혁.신형진.김성준 189 changes in temperature and precipitation of South Korea. Especially, the increase of temperature by climate change can affect the amount and pattern of snowfall. Accordingly, we tried to predict future snowfall and the snowfall pattern changes by using the downscaled GCM (general circulation model) scenarios. Causes of snow varies greatly, but the information provided by GCM are maximum / minimum temperature, rainfall, solar radiation. In this study, the possibility of snow was focused on correlation between minimum temperatures and future precipitation. First, we collected the newest fresh snow depth offered by KMA (Korea meteorological administration), then we estimate the temperature of snow falling conditions. These estimated temperature conditions were distributed spatially and regionally by IDW (Inverse Distance Weight) interpolation. Finally, the distributed temperature conditions (or boundaries) were applied to GCM, and the future snowfall was predicted. The results showed a wide range of variation for each scenario. Our models predict that snowfall will decrease in the study region. This may be caused by global warming. Temperature rise caused by global warming highlights the effectiveness of these mechanisms that concerned with the temporal and spatial changes in snow, and would affect the spring water resources.

Two new floods, climate change, and ethics

Two new floods, climate change, and ethics

Modeling Snow–Canopy Processes on an Idealized Mountain

Abstract Snow interception in a coniferous forest canopy is an important hydrological feature, producing complex mass and energy exchanges with the surrounding atmosphere and the snowpack below. Subcanopy snowpack accumulation and ablation depends on the effects of canopy architecture on meteorological conditions and on interception storage by stems, branches, and needles. Mountain forests are primarily composed of evergreen conifer species that retain their needles throughout the year and hence intercept snow efficiently during winter. Canopy-intercepted snow can melt, fall to the ground, and/or sublimate into the air masses above and within the canopy. To improve the understanding of snow–canopy interception processes and the associated influences on the snowpack below, a series of model experiments using a detailed, physically based snow–canopy and snowpack evolution model [Alpine Multiscale Numerical Distributed Simulation Engine (AMUNDSEN)] driven with observed meteorological forcing was conducted. A cone-shaped idealized mountain covered with a geometrically regular pattern of coniferous forest stands and clearings was constructed. The model was applied for three winter seasons with different snowfall intensities and distributions. Results show the effects of snow–canopy processes and interactions on the pattern of ground snow cover, its duration, and the amount of meltwater release, in addition to showing under what conditions the protective effect of a forest canopy overbalances the reduced accumulation of snow on the ground. The simulations show considerable amounts of canopy-intercepted snowfall can sublimate, leading to reduced snow accumulation beneath the forest canopy. In addition, the canopy produces a shadowing effect beneath the trees that leads to reduced radiative energy reaching the ground, reduced below-canopy snowmelt rates, and increased snow-cover duration relative to nonforested areas. During snow-rich winters, the shadowing effect of the canopy dominates and snow lasts longer inside the forest than in the open, but during winters with little snow, snow sublimation losses dominate and snow lasts longer in the open areas than inside the forest. Because of the strong solar radiation influence on snowmelt rates, the details of these relationships vary for northern and southern radiation exposures and time of year. In early and high winter, the radiation protection effect of shadowing by the canopy is small. If little snow is available, an intermittent melt out of the snow cover inside the forest can occur. In late winter and spring, the shadowing effect becomes more efficient and snowmelt is delayed relative to nonforested areas.

High-Resolution Coupled Climate Runoff Simulations of Seasonal Snowfall over Colorado: A Process Study of Current and Warmer Climate

Abstract Climate change is expected to accelerate the hydrologic cycle, increase the fraction of precipitation that is rain, and enhance snowpack melting. The enhanced hydrological cycle is also expected to increase snowfall amounts due to increased moisture availability. These processes are examined in this paper in the Colorado Headwaters region through the use of a coupled high-resolution climate–runoff model. Four high-resolution simulations of annual snowfall over Colorado are conducted. The simulations are verified using Snowpack Telemetry (SNOTEL) data. Results are then presented regarding the grid spacing needed for appropriate simulation of snowfall. Finally, climate sensitivity is explored using a pseudo–global warming approach. The results show that the proper spatial and temporal depiction of snowfall adequate for water resource and climate change purposes can be achieved with the appropriate choice of model grid spacing and parameterizations. The pseudo–global warming simulations indicate enhanced snowfall on the order of 10%–25% over the Colorado Headwaters region, with the enhancement being less in the core headwaters region due to the topographic reduction of precipitation upstream of the region (rain-shadow effect). The main climate change impacts are in the enhanced melting at the lower-elevation bound of the snowpack and the increased snowfall at higher elevations. The changes in peak snow mass are generally near zero due to these two compensating effects, and simulated wintertime total runoff is above current levels. The 1 April snow water equivalent (SWE) is reduced by 25% in the warmer climate, and the date of maximum SWE occurs 2–17 days prior to current climate results, consistent with previous studies.

An exceptionally heavy snowfall in Northeast china: large-scale circulation anomalies and hindcast of the NCAR WRF model

In Northeast China (NEC), snowfalls usually occur during winter and early spring, from mid-October to late March, and strong snowfalls rarely occur in middle spring. During 12–13 April 2010, an exceptionally strong snowfall occurred in NEC, with 26.8 mm of accumulated water-equivalent snow over Harbin, the capital of the most eastern province in NEC. In this study, the major features of the snowfall and associated large-scale circulation and the predictability of the snowfall are analyzed using both observations and models. The Siberia High intensified and shifted southeastward from 10 days before the snowfall, resulting in intensifying the low-pressure system over NEC and strengthening the East Asian Trough during 12–13 April. Therefore, large convergence of water vapor and strong rising motion appeared over eastern NEC, resulting in heavy snowfall. Hindcast experiments were carried out using the NCAR Weather Research and Forecasting (WRF) model in a two-way nesting approach, forced by NCEP Global Forecast System data sets. Many observed features including the large-scale and regional circulation anomalies and snowfall amount can be reproduced reasonably well, suggesting the feasibility of the WRF model in forecasting extreme weather events over NEC. A quantitative analysis also shows that the nested NEC domain simulation is even better than mother domain simulation in simulating the snowfall amount and spatial distribution, and that both simulations are more skillful than the NCEP Global Forecast System output. The forecast result from the nested forecast system is very promising for an operational purpose.

An Overview of the Second Generation Adjusted Daily Precipitation Dataset for Trend Analysis in Canada

A second generation adjusted precipitation daily dataset has been prepared for trend analysis in Canada. Daily rainfall and snowfall amounts have been adjusted for 464 stations for known measurement issues such as wind undercatch, evaporation and wetting losses for each type of rain-gauge, snow water equivalent from ruler measurements, trace observations and accumulated amounts from several days. Observations from nearby stations were sometimes combined to create time series that are longer; hence, making them more useful for trend studies. In this new version, daily adjustments are an improvement over the previous version because they are derived from an extended dataset and enhanced metadata knowledge. Datasets were updated to cover recent years, including 2009. The impact of the adjustments on rainfall and snowfall total amounts and trends was examined in detail. As a result of adjustments, total rainfall amounts have increased by 5 to 10% in southern Canada and by more than 20% in the Canadian Arctic, compared to the original observations, while the effect of the adjustments on snowfall were larger and more variable throughout the country. The slope of the rain trend lines decreased as a result of the larger correction applied to the older rain-gauges while the slope of the snow trend lines increased, mainly along the west coast and in the Arctic. Finally, annual and seasonal rainfall and snowfall trends based on the adjusted series were computed for 1950–2009 and 1900–2009. Overall, rainfall has increased across the country while a mix of non-significant increasing and decreasing trends was found during the summer in the Canadian Prairies. Snowfall has increased mainly in the north while a significant decrease was observed in the southwestern part of the country for 1950–2009.

Assessment of Snow Cover Vulnerability over the Qinghai-Tibetan Plateau

By using daily air temperature and precipitation data, and the weather phenomena data of daily snowfall from 98 meteorological stations over the Qinghai-Tibetan Plateau (QTP), this paper performs an “at-risk” evaluation on snowfall and accumulated snow over the QTP under current climate situation and future climate warming condition. When rainfall, snowfall, or accumulated snow weather phenomena occur, critical values are determined based on daily air temperature and precipitation for current climate conditions. Air temperature of 0°C is defined as the critical value of temperature for rainfall or snowfall, while 0°C air temperature and 4.0 mm (autumn) or 3.0 mm (spring) snowfall amounts are defined as the critical values for accumulated snowfall. Analyses based on the above critical values disclose that under current climate condition, stations with “at-risk” accumulated snow account for 33% and 36% of all stations, and the “at-risk” snowfall stations reach 78% and 81% in autumn and spring, respectively. Spatially, most stations with “at-risk” accumulated snow are located on the southern and eastern edge of the QTP, and stations with “at-risk” snowfall are also apparent at the northern edge. If the air temperature increases by 2.5°C in 2050, only the snowfall at a few “at-risk” snowfall stations will transform into rainfall, while most “at-risk” accumulated snow stations will face the problem that snowfall is hardly accumulated. Additionally, most stations will become “at-risk” accumulated snow stations, indicating that both the snow depth and the snow cover duration will decline in most areas of the QTP, including a delay of the start date and an advancing of the end date of snow cover. CitationMa, L., D. Qin, L. Bian, et al., 2011: Assessment of snow cover vulnerability over the Qinghai-Tibetan Plateau. Adv. Clim. Change Res.,2(2), doi: 10.3724/SP.J.1248.2011.00093.

Orographic influence of east Greenland on a polar low over the Denmark Strait

AbstractWe present a numerical study of a polar low which hit western Iceland in January 2007, with heavy snowfall and mean wind speeds exceeding 20 m s−1 in several locations. The operational models at the time captured the polar low formation rather well, but there was a large spread in their predictions of the subsequent evolution and track of the polar low. The objective of this study is to investigate possible orographic forcing from Greenland as a trigger for the polar low development. In addition to an analysis of surface observations and satellite imagery, sensitivity studies using HIRLAM were carried out with various degradations of Greenland's orography, as well as with modifications to the sea‐surface temperature (SST), surface roughness and the data assimilation scheme. Despite the presence of an upper‐level trough and weak static stability in all the simulations, the polar low development was found to be very sensitive to the presence of the high mountains of eastern Greenland. Whereas the control run captured well the main features of the polar low, simulations with parts of east Greenland's orography removed gave a southward‐displaced polar low which moved rapidly eastward, resulting in substantially underestimated near‐surface winds and snowfall amounts. Setting the orographic heights over all of Greenland to zero led to the complete disappearance of the polar low. On the other hand, artificially increasing the SST by 4 K in the Denmark Strait, reducing the orographic roughness or replacing the four‐dimensional variational assimilation scheme (4D‐Var) by 3D‐Var had only a small effect on the polar low. We suggest that hitherto unreported interactions between the high mountains of east Greenland and polar low development over the Denmark Strait may be more important for polar low formation than katabatic flow from valleys in east Greenland that was highlighted in earlier studies. Copyright © 2011 Royal Meteorological Society

An East Coast winter storm precipitation climatology

Using a previously compiled climatology of East Coast winter storms (ECWS), an ECWS precipitation climatology was developed for the eastern United States from 1951–1952 to 2005–2006, using an automated procedure. Non-ECWS precipitation that may have occurred during ECWS events was excluded through the development of a decision process based on knowledge of the characteristics of extratropical storms and aided by ECWS case study analyses. The main components used by this decision process were the location of precipitation and pressure gradients, and the presence of additional cyclones, not meeting the ECWS criteria. A sensitivity analysis of the ECWS precipitation climatology was conducted, which considered the change in the climatology if non-ECWS precipitation was not excluded by the decision process. The highest average percentages of snowfall from ECWS occur in the Middle Atlantic and southern New England regions. These heavily populated metropolitan areas typically receive 45% of snowfall from ECWS. The highest average percentages of annual precipitation from ECWS are generally 20–25% and are located along the East Coast from Virginia northward to Maine. For the metropolitan centres of the Northeast, and for northern New England, El Nino years seem to indicate above average precipitation and snowfall amounts from ECWS, as well as an above average overall percentage of precipitation and snowfall from ECWS. Copyright © 2010 Royal Meteorological Society

Identifying extreme event climate thresholds for greater Manchester, UK: examining the past to prepare for the future

AbstractExtreme weather events can have severe consequences for the local environment and population. Projected future changes in climate (e.g. UKCP09) indicate that North West England is likely to experience an increasing frequency and intensity of meteorological extremes, leading to flooding, heat waves and storms. Consequently, it is important that the region enhances its preparedness for such events. This paper explores the possibility of developing quantifiable climate risk indices for the case study area of Greater Manchester, using a combination of archival research and statistical analysis of past climate data. For extremes which are the function of a single meteorological variable (e.g. heat waves, pluvial flooding and heavy snowfall) the thresholds proved to be reliable and skillful. Days with maximum daily temperature greater than or equal to 29.2 °C, daily snowfall amount greater than or equal to 6 cm or maximum gust speed greater than or equal to 60 knots are found to be indicative of weather‐related impacts which have in the past affected human health/well‐being, have caused damage to the urban infrastructure or have severely disrupted services. Extreme events which are the result of a more complex interaction between variables (e.g. drought, freezing conditions) were less well captured by applying the thresholds associated with a single variable in isolation. Such critical threshold indices can be used in conjunction with future projections of climate change to establish weather‐related risk for the future. This risk‐based approach can subsequently be integrated to climate change adaptation strategies and development planning to ensure future preparedness. Copyright © 2011 Royal Meteorological Society

Observational and supportive modelling analyses of winter precipitation change in China over the last half century

AbstractOverall increasing trends in annual precipitation and widespread warming over China have been documented. During the winter months in southeast China, where snow is commonplace but rarely accumulates, the climatological 0 °C surface isotherm generally defines the southern boundary of the snowfield. Therefore, a warming climate will: (a) modify the southern boundary of the snowfield; and (b) potentially alter the snow‐rain ratio. Using recently released daily precipitation from the Asian Precipitation‐Highly Resolved Observational Data Integration Towards Evaluation (APHRODITE) and temperature observations from the ERA‐40/Interim Reanalyses, this study investigated historical winter precipitation changes in China. Since snowfall observations were largely unavailable for southeast China, snowfall amounts were estimated using a rain‐snow threshold temperature (RST) method which was subsequently verified by in situ and satellite observations of snow depth, snow cover, and snow water equivalent (SWE). The composite analysis reveals a decrease in snowfall totals which are accompanied by an increase in rainfall; this change corresponds with the northward retreat of the 0 °C surface isotherm and the snow‐rain ratio. Atmospheric circulation analysis indicated lower tropospheric warming with increased moisture over southeast China, consistent with previous studies. Moreover, we observed an increase in the convergence of water vapour flux which sustains the increase in precipitation; this is accompanied by the suppression of snowfall due to the lower tropospheric warming. An additional analysis employed to further substantiate the RST method was undertaken by modelling the snow‐rain ratio with the Weather Research and Forecasting (WRF) Model. The results were in agreement with those estimated from the observations. Copyright © 2011 Royal Meteorological Society

A trajectory study on the heavy snowfall phenomenon in Yeongdong Region of Korea

It is well known that when the Siberian High expands to the western part of the East Sea (Japan Sea), the distribution of snowfall amount is mainly controlled by the topography. Therefore, the maximum area of the precipitation is typically located over the slopes and near the summit of the Taebaek Mountains (called Type A). However, sometimes there were snowfall maxima near the Yeongdong coastal area of Korea rather than the neighboring mountains (called Type B) for some events. Two heavy snowfall events of 20–21 January 2008 of Type A (named by Event A) and of 13 January 2008 of Type B (named by Event B) were selected to understand the differences in the locations of snowfall maxima in the Yeongdong region of Korea. To do so, we investigated the differences between the two events in the movement of the air parcels leading to the understanding of the heavy snowfall mechanism using 3-dimensional trajectory analyses which applied the Weather Research and Forecasting (WRF) high resolution output as 3-dimensional meteorological fields. In this study, an upward motion under the influence of the northeasterly wind was observed along the slope of the mountains during Event A. In contrast, there was a strong downward motion along the slope of the mountains under the influence of the northwesterly wind while the parcels were reaching Gangneung (GN, hereafter) during the snowfall period of Event B. Furthermore, during Event B, the convergence of the parcels different in potential temperature and mixing ratio, yielded a favorable condition for forming a coastal front (discontinuity zone) around the Yeongdong coastal area. This lead to heavy snowfall over GN in the coastal plain region rather than in Daegwallyeong (DG, hereafter) near the summit of the Taebaek Mountains, which differs from the snowfall distribution of Event A.