Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ers ff 1,2 C (TBZD), mean air temperature ◦ ects via snowmelt (Barnett et al., ff , and C. Kou 4472 4471 1,2 , X. Liu 5 , H. Xie 3,4 , X. C. Li 1,2 This discussion paper is/has beenSciences under (HESS). review Please for refer the to journal the Hydrology corresponding and final Earth paper System in HESS if available. Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, Key Laboratory for Satellite Mapping Technology and Applications of StateNational Administration Climate of Center, China MeteorologicalCollaborative Administration, Innovation Beijing Center 100081, on China Forecast and Evaluation of Meteorological Disasters, Department of Geological Sciences, University of Texas at San Antonio, Texas 78249, USA Abstract Daily snow observation dataten from annual 672 mean stations, snow particularly coverstudy. days the We (SCD), first 352 during examine stations spatiotemporal 1952–2010 with variations indate and over China, trends (SCOD), are of used and SCD, in snow snow cover this ships onset cover with number end of date days (SCED). with temperature We below then 0 investigate SCD relation- (MAT), and Arctic Oscillation (AO)season index, of the each latter snow two year.tire being The country results constrained include indicate to 1955, that the1965, 1957, the 1999, snow 2002, 1964, heavy-snow and years and 2009. for 2010,sons The the reduced and for en- TBZD light-snow the and years increased overallnot MAT include delay are necessary 1953, the of for main one SCOD rea- station andSCED. to This advance experience explains both of why significantly only SCED delayed 15while since % SCOD 75 of and 1952, % the early although of stations show it thewith significant is stations the shortening show overall of shortening SCD, noreported. of significant the Our change snow analyses in period indicate theare in that SCD very the the trends. complex Northern SCD This and distribution Hemisphere di TBZD, are pattern previously MAT, not and or controlled trends AO), by inindex but any China has single a the climate maximum combination variable impact ofChangbai on examined Mountains, the multiple (i.e. and SCD North variables. shortening Xinjiang, It trendsmaximum while in impact is the on Shandong combined found the Peninsula, TBZD SCD and thatand shortening MAT have the Sanjiang trends the in Plain. AO the Loess Plateau, Xiaoxingganling, 1 Introduction Snow has a profound impactis on very the surficial sensitive and totivity, atmospheric low climatic thermal thermal conditions, and and conductivity, environmental and changes, hydrological because e of its high reflec- Variability in snow cover phenologyChina in from 1952 to 2010 C. Q. Ke Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/12/4471/2015/ 12, 4471–4506, 2015 doi:10.5194/hessd-12-4471-2015 © Author(s) 2015. CC Attribution 3.0 License. 1 Nanjing University, Nanjing, 210023,2 China Surveying, Mapping and Geoinformation3 of China, Nanjing University, Nanjing,4 210023 China Faculty of Geography and RemoteTechnology, Nanjing, Sensing, 210044, Nanjing China University5 of Information Science and Received: 12 February 2015 – Accepted: 16Correspondence April to: 2015 C. – Q. Published: Ke 30 ([email protected]) AprilPublished 2015 by Copernicus Publications on behalf of the European Geosciences Union. 5 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erences ff erences in the SCD (Wang and Li, ff 4473 4474 Southern Oscillation (ENSO), North Atlantic Os- / erences. As an index of the dominant pattern of non-seasonal sea-level ff China is the main large snow cover distribution area in the middle latitudes and the The SCD is sensitive to local winter temperature and precipitation, latitude (Hantel Snow cover day (SCD) is an important index that represents the environmental fea- altitudinal gradient andEssentially, terrain the roughness SCD (Lehning variationtion et is or mainly al., attributed climatic 2011; to forcing2014), Ke large-scale (Beniston, such and atmospheric as 1997; Liu, circula- monsoons, Ma 2014). El and Niño Qin, 2012; Birsan and Dumitrescu, Northern Hemisphere, with large spatiotemporal di et al., 2000; Wang et al., 2009a; Serquet et al., 2011; Morán-Tejeda et al., 2013), and advanced. Satellite snow datathe indicated Northern that the Hemisphere average has1972/73 snow decreased and season at 2007/08, duration with a1980s, over a especially rate in major of western change 5.3 Europe,in in days central western and the per United East States trend decade Asia, (Choi of between and et mountainous snow al., regions 2010). duration in the late 2012). Analysis of 40 meteorological stationshad from a 1971 to significant 2010 decreasing indicatedwith trend that the in the SCD the largest westernet decline and al., south-eastern observed 2012). Tibetan Data in Plateau, at analysis Nielamu, most also stations reaching indicated in that 9.2 theof the Hetao days meteorological SCD region station per had and data a its decade intrend, linear vicinity Xinjiang (Tang decreasing occurring (Xi showed trend et that mainly al., the in 2009).meteorological SCD 1960–1980 However, data had analysis (Wang from a et slight 80 increasing al., stationsresults in 2009b). showed Heilongjiang that Li Province, the et NortheastSCOD snow al. China. (by cover (2009) Their 1.9 duration analysed days shortened, perdelay because decade) and of advance and took both advancing place SCED the mainly (by delayed in 1.6 the days lower per altitude decade). plains. The cillation (NAO), and Arcticship Oscillation between (AO). the Xu SCD etgreat and al. spatial monsoon di (2010) index investigated in the the relation- Tibetan Plateau and indicated their in space and time2005), and especially contributes in to thelinear climate Northern trends change Hemisphere. of Bulygina over SCD et shortthe observed al. duration time at of (2009) scales snow 820 investigated (Zhang, cover the stationsin decreased from the in 1966 the mountainous northern to regions regionsFar 2007, of of East. and southern European Peng indicated Russia Siberia, that et and whileand al. it snow (2013) increased cover in analysed end(1980–2006) Yakutia trends date from and over in the (SCED) 636 the in meteorologicalfound stations snow relation that in the cover to the SCED onset Northern remained temperature stable date Hemisphere. over over They (SCOD) North the America, past whereas over 27 Eurasia years it has pressure variations, the AO shows aNorthern large Hemisphere impact on (Thompson the and winter weather Wallace, patterns 1998; of Thompson the et al., 2000; Gong tures of climate (Yeto and the Ellison, radiation 2003; and Scherrer heat et balance al., of 2004), the Earth–atmosphere and system. is The directly SCD related varies and uncertainties in space2013). and Spatiotemporal time variations than ofor ever blizzards, snow before particularly, cover (Shi excessive are et snowfallNorton, over al., also 1992; a Liang 2011; manifested short et Ji as time al., and 2008; snowstorms duration Kang, Gao, (Bolsenga 2009; and Wang et al., 2013; Llasat et al., 2014). 1989; Groisman et al.,has 1994). decreased The significantly over extent the ofson past snow and decades cover because Dewey, 1990; in ofdecrease global Brown the warming in and Northern (Robin- Robinson, Hemisphere the 2011).sponse spring, Snow to and cover larger the showed albedodepth the decrease feedback in largest (Déry rate central and increased Canadasnowpack Brown, showed for in 2007). the the higher In Rocky greatest latitudesever, Mountains North decrease in in in (Dyer America, the situ re- and snow U.S. dataa Mote, declined shorter showed 2006), (Pederson et snowmelt and a al., season significantindicated 2013). over that increase How- Eurasia the in (Bulygina snow et snowdepth cover over (Qin al., accumulation northwest et 2009). in China al., Meteorological exhibited winterMa 2006), data a and but but weak the Qin, upward spatiotemporal 2012). trendcontinuing variations Simulation in were global experiments large warming, using (Ke the climate et models snow al., variation indicated 2009; that, in with China would show more di 5 5 20 10 15 25 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C (TBZD), the mean air temperature ◦ erent, varying between 59 years (1951/1952– 4476 4475 ff erent regions of China; we then examine the sensitivity of SCD ff We define a snow year as the period from 1 September of the previous year to 31 Since station relocation and changes in the ambient environment could cause incon- The focus of this study is the variability in the snow cover phenology of China. May 2010 as themean spring SCDs season greater of than snowobservation period year 1.0 for 2010. (day) each Finally, are station 672 is selected stations di for with this annual study (Fig. 1), although the August of the currentare treated year. For as the instance,and autumn September, February season October, 2010 of and as snow November the year 2009 winter 2010, season December 2009 of and snow January year 2010, and March, April, and for logic, consistency, and uniformity)errors on (Ren the et observational datasets al.,Moberg, in 2005). order 1997) The to at standard reduce the normalture 95 homogeneity % series test confidence data (Alexandersson level in and isperformed order applied after to to all inhomogeneities the identify are daily alltion. eliminated, SCD possible using and breakpoints. nearest tempera- neighbour Time interpola- series gap filling is 2009/2010) and 30 yearsvation (1980/1981–2009/2010). records between Overall, 50 588 and stationsstations 59 between years, have 30 47 obser- and stations 39 between years.than 40 Most 50 and of years 49 the years, are stations and located with 37 in observation records remote of or less high elevation areas. sistencies in the recorded data, we implement strict quality controls (such as inspection conditions, the discontinuous nature of snowfallin is the obvious Tibetan in Plateau, western with China,in patchy especially these snow station cover records. (Ke and Atthe the Li, observation same 1998), history time, and in is many relatively western thinare short, China, SCDs although station located two density in of is western the low,thin and three China. major If SCDs snow all regions are stations notwould with be taken short a into time problem. series account,study, including are Therefore, the those eliminated, a spatial thin and time SCDs. representativeness series of of the at dataset least 30 years is included in this fined as a dayof when the the observation snow field cover isany in covered day by the with snow, at area and least fulfils theof half two minimum less of snow requirements: the than depth observation at 1 is fieldhigh least cm, 1 covered half in the by cm. snow For snow eastern but depth China, withwith is snow relatively where depth denoted long the histories as observational (as 0, long data i.e. as for a 59 thin most years). SCD. Because stations Station of are topography density complete, and is climate to the number of day with temperature below 0 2.1 Data We use daily snow31 cover August and 2010, provided temperature byMeteorological data the Administration in National (CMA). China Meteorological According from Informationteorological to Centre 1 Observations the of (China September Specifications China Meteorological for 1951 Administration, Surface to 2003), Me- an SCD is de- SCOD, and SCED in di (MAT), and the Arctic Oscillationand (AO) SCED). index during the snow season (between SCOD 2 Data and methods A longer time seriestemporal of daily analyses. observations We of first snow characterize cover is the used spatial for patterns these spatial of and change in the SCD, et al., 2001; Wu andwinter extreme Wang, cold 2002; days Jeong in andAO the (Chen Ho, et northern 2005). al., The part 2013). inter-annualAn of Certainly, variation the eastern increase of AO China in plays is the anin closely important SCD the linked role before Tibetan to in 1990 Plateau, the the and andindex SCD snow (You a et variation. duration al., decrease has 2011), after positive andthe correlations a 1990 Tibetan significant with have Plateau correlation the been on between winter inter-decadal the reported AO AO timescale and was snowfall also over reported by Lü et al. (2008). 5 5 20 15 25 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4478 4477 ective tool to extract the trends of time series, ff N from http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ ◦ Areas with SCDs of 10–60 are called unstable snow areas with annual periodicity, All 672 stations are used to analyse the spatiotemporal distribution of SCD in China, The daily AO index constructed by projecting the daily (00Z) 1000 mb height anoma- A digital elevation model (DEM) according to the Shuttle Radar Topographic Mission The spatial distribution of tendency in the SCD, SCOD, and SCED, and their cal- ,daily_ao_index/ao.shtml is used insponds this to paper. low A (high)pressure positive pressure anomalies (negative) across anomalies AO the throughout index subtropicalaverage the corre- and the mid-latitudes polar daily (Peings region et AOof and al., indexes each 2013). high during We station (low) the asseasons the snow from AO season 1952 index to (between of 2010, SCOD the for and each year. of A SCED) the time 352(SRTM, serieshttp://srtm.csi.cgiar.org ) stations, of of is the AO then National constructed. indexes(NASA) Aeronautics of with and the Space a snow Administration resolution ofbase 90 map. m and the administration map of China2.2 are used as the Methods We apply the non-parametricSCOD, Mann–Kendall and (MK) SCED. The test MK toand test analyse is is widely the an applied e trends tois of the characterized SCD, analysis as of being climatestandardized more sequences MK objective, (Marty, statistic 2008). since value The indicates ittive MK an is value test upward demonstrates a or a increasing non-parametric downward trend,95 test. or % while decreasing A are a taken trend. positive nega- as Confidence thresholds levelsof to of SCD, classify SCOD, 90 the and and significance SCED. of positive and negative trends culated results, aremethod. spatially The interpolated UCK by model applying is capable the of universal simultaneously cokriging treating multiple (UCK) variables and Plateau, Northeast Plain, Northof China the Plain, Qinling-Huaihe Shandong line Peninsula, (along andAreas the with areas SCDs Qinling in of Mountains 1–10 north and aremountainous called Huaihe unstable areas River snow to areas are without the excluded), annualJaran east). periodicity including Desert, (the the the Tarim peripheral Basin, parts Qaidam of Basin, Sichuan Badain Basin, the northeast part of the Yungui including the peripheral parts of the three major stable snow regions, and the Loess their cross-covariance, and has been(Kuhlman successfully and applied Igúzquiza, to 2010; spatial Biggs data and Atkinson, interpolation 2011). 3 Results 3.1 Spatiotemporal variations of SCD 3.1.1 Spatial distribution of SCD The analysis of observationsstable snow from regions 672 with stationsXinjiang, more and indicates than the that Tibetan 60 there Plateau,(Fig. annual with are 2a). mean Northeast three In SCDs: China major the Northeast beingeast the Daxingganling, China, China, largest there Xiaoxingganling, North of are and thelong more Changbai three snow than Mountains season. 90 The annual ofthe mean longest North- Daxinganling SCDs, annual corresponding Mountains) mean to in SCDs,tively a Inner 169 long relatively Mongolia. days, is In in at North theannual Arxan Xinjiang, Tianshan mean Station the and (in SCDs SCDs Altun are in Mountains,Har rela- the followed Mountains, by Himalayas, Anemaqen Nyainqentanglha, the Mountains, Tanggulaare Junggar Mountains, and relatively Basin. Bayan long, The Qilian although Mountainsthough most of the of Tibetan the these Plateau areas Tibetan hasmean have a Plateau SCD less high is elevation, than not a 60 as cold annual large climate, as SCDs. and that many Al- of glaciers, the its other two stable snow regions. while only 352 stationschanges with of more SCOD, than SCED, and ten SCD annual relationships mean with SCDs TBZD, MAT, and arelies the used AO to poleward index. study of the 20 5 5 25 20 10 15 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | one SD (1 SD), we ± ected considerably by the ff erences from one year to an- ff cients of variation (CV) in the SCD (Fig. 2b). 4480 4479 ffi 2 SD account for 29 % of all stations in 1955 and 1957, and are erent, i.e. more snow in the spring and autumn combined than in the ff + N). Because of the latitude or local climate and terrain, there is no snow in the ◦ The temporal variation of SCD shows very large di The spatial distribution pattern of SCDs based on longer time series climate data in The three major stable snow regions, Northeast China, North Xinjiang, and the east- other. We definea heavy-snow given or year, light-snowof if years the 70 based % stations on of have the the an SCD stations SCD larger anomaly: have (smaller) a for than positive the (negative) mean anomaly and 30 % regard the year asare a 1955, heavy-snow 1957, (light-snow) 1964,than year. and the The 2010 mean heavy-snow (Table yearsconsidered 1). in as Moreover, China the extremely stationswide heavy-snow with snowstorm years. SCDs except In larger impact for 1957, on North there agriculture, Xinjiang wasin natural (Fig. an a ecology, 4a). almost and tremendoussnow This nation- social-economic year disaster 1957 in systems, (Hao event China. andrope At had et resulted (including the a al., Spain) same great time, (Llasat 2002). blizzards et The occurred al., in year 2014). North 2010 Globally, America an and was unusual Eu- also cold a weather heavy- pat- large fluctuations because there istainly little little precipitation snowfall during and theTarim cold large seasons, Basin CVs and of is cer- SCD. anhas In extremely a particular, very arid the large Taklimakan region, range DesertRiver of with Plain in SCD also only the fluctuations. has Additionally, occasional the largeclimate snowfall. middle SCD with and Therefore, fluctuations short lower because it winter Yangtze ofthe and warm-temperate CV little or snowfall. (Wang sub-tropic Generally, et theprecipitation al., smaller (Yang et 2009a). the al., SCD, This 2015). the is larger consistent with3.1.2 other climate variables, Temporal such variations as of SCD Seasonal variation of(Hantel SCD et is al., primarily 2000;is Liu controlled primarily et concentrated by al., in“single-peak” temperature 2012). the distribution. and In winter In precipitation (Fig. North theSCD 3). is Xinjiang Tibetan slightly In and Plateau, di these however, Northeastwinter. the regions, China, seasonal the snow variation SCD of exhibits a Plateau, and the middle and lowermean Yangtze River annual Plain. SCD Areas with of occasional less snowin than and 1.0 the (day) belt are distributed along northof Kunming, of 25 the the Sichuan Nanling Basin Mountains, and and Fuzhou (approximate latitude and Liu, 2014). The higherthere the are. latitude, the Therefore, lower thereXinjiang, the temperature are and and relatively fewer the more more SCDssouth-western SCDs SCDs China, to the in the elevation Northeast southand is China higher (Fig. the than SCDs and 2a). eastern are North Inprecipitation areas greater the also at than Tibetan the plays in same Plateau,In a eastern latitude, located the critical China in north-eastern (Tang role et coastal in al., areas determining 2012). of the The China, amount SCD which of (Hantel are et a al., 2000). Nevertheless, the SCD inern arid and or south-western semi-arid Tibetan areas, Plateau, such and central as and South western Xinjiang, Inner the Mongolia north- have Taklimakan Desert, Turpan Basin, thesouthern Yangtze parts River of Valley Yunnan, Guangxi, in Guangdong the and Sichuan Fujian, Basin, and on the this the study Hainan is Island. similar to previouset studies al., (Li 2009a; and Wang Mi, and 1983; Li, Li,elevation, 2012). 1990; and The Liu is snow et distribution generally al., is 2012; consistent closely Wang with linked the to latitude climate and zones (Lehning et al., 2011; Ke ern Tibetan Plateau, have smaller coe ocean, there is much(inland) precipitation. climate, In the North precipitationSCDs Xinjiang, is in less which the than has north in a ofet Northeast Northeast typical al., China, 2009b). China continental Moreover, and than the there in local(Lehning North are topography et has Xinjiang more al., a (Dong 2011). relatively et The largetion, al., Tarim impact thus 2004; Basin on snowfall Wang is the there located SCD isby inland, extremely high rare with mountains, (Li, relatively and 1993). little therefore Theing precipita- situated Sichuan in in Basin fewer the SCDs is (Li precipitation surrounded and shadow Mi, in 1983; winter, Li, result- 1990). 5 5 20 25 10 15 15 10 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er from ects the ff ff erences in the ff erence in the spa- ff airs of China, the 2008 snow disas- ff 4481 4482 biggestsnowstorms-us). = erent regions of China, there are great di ff erences in the temporal variations of SCD even in the three major ff erent atmospheric circulation backgrounds, vapour sources, and to- ff 1SD, it is found that 1957, 1973, and 2010 are heavy-snow years in Northeast ± ected by the Indian monsoon from the south, westerlies from the west, and the ff erence in the SCDs within the Tibetan Plateau, and even a di There are big di Heavy-snow years in the Tibetan Plateau include 1983 and 1990, whereas light- Because of di Light-snow years include 1953, 1965, 1999, 2002, and 2009 (Table 1). If there is ff China (Helongjiang, Jilin and2002, eastern Inner and Mongolia), 2008 whilein are 1959, 1963, North light-snow 1967, Xinjiang years 1998, includesnow there 1959, years (Table include 1960, 2, 1974, 1977, Fig.the 1995, 1980, 4a–c). and regions 1988, Heavy-snow 2008 prone 1994, (Table years todevelopment 2, and of Fig. catastrophe, 2010, animal 4c). husbandry where and North (Hao frequent light- et Xinjiang heavy al., is 2002). snowfall one greatly of snow years a include 1965, 1969, andis 2010 a (Table 2). The climateEast in the Asian Tibetan monsoon Plateau fromdi the east (Yaotiotemporal et distribution al., of 2012). snow Therefore,the disasters conclusions there (Wang drawn is et by a Dong al.,covering et regional only 2013). al. a Our (2001), short results as period they di (1967–1996). only used3.1.3 data from 26 stations, SCD trends Changing trends of annualin SCDs Table are 3. examined, Among as the shown 352ative stations, in trend, there Fig. and are 5, 35 54 andlevel), stations stations while summarized (15 75 %) (10 % %) with of with a stationsdownward significant show a trend neg- no in significant significant the positive trends. ShandongNorth The trend SCD Peninsula, China (both and exhibits Plain, a at insignificant the significant the downwardNorth Loess trends 90 Xinjiang, % Plateau, in Northeast the the Xiaoxingganling, Qinghai,Some the and station Changbai the records Mountains, south-western indicate a Tibetan decreasing Plateau rate (Fig. of 5a). 1.3–7.2 days per decade, for ex- stable snow regions. Ifyears, we using redefine the the much(negative) anomaly SCD higher and anomaly standard 40 % for that ofmean stations heavy-snow 80 % should or have of an light-snow stations SCD larger should (smaller) have than the a positive SCD even in one year.duration For in example, in the 2008, Yangtze River therejiang Basin, were (Fig. North more 4c), China, SCDs especially and and innot the longer observed. the snow Tianshan However, Yangtze four Mountains River episodes in Basin, of Xin- peratures, where severe and and large freezing persistent snowfall weather snow, is extreme occurred lowtrophe normally in tem- in early this 2008, region leading where to there(Gao, a were 2009). large-scale no As catas- mitigation reported measures by forter the this killed Ministry type 107 of of people a Civil and disaster A of caused economic losses damage of broke US$ records 15.45the from billion. the contrary, Both past in the five SCDs the decades andthe (Wang same scale et Tibetan year al., 2008). (2008), Plateau, On there andapparent was negative Pan-Bohai anomaly no Bay (Fig. snow region. 4c). disaster Moreover, in Northeast North China Xinjiang, had an pographic conditions in di too little snowfall insnowfall a in specific the year, cold a seasonexample, drought is East a is China slow possible. displayed process Drought an andand resulting apparent can had from sometimes negative very cause SCD little little disasters. anomalywhere For snowfall, in snowfall leading 2002 is to the (Fig. an primary 4b), extreme form winter of winter drought precipitation in (Fang Northeast et China, al., 2014). tern caused by highparts pressure of (the the AO)peratures, Northern brought leading cold, Hemisphere moist to, experiencedport air heavy among disruption, from snowfall other and the and power things, north. Europe, record-low failures ahttp://en.wikipedia.org/wiki/February_9-10,_2010_North_American_blizzard Many http://en.wikipedia.org/wiki/Winter_of_2009-10_in_ tem- ). number ofThe blizzards deaths, across the widespread Texas andton, Oklahoma trans- panhandles 1992; in Changnon 1957 (Bolsenga and andalso Changnon, Nor- recorded as 2006) the and biggest snowstorms across(http://www.crh.noaa.gov/mkx/?n of the the east United States coast from in 1888 to 2010 the were present 5 5 10 15 20 25 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4484 4483 1SD), we consider a given year as a delayed (early) SCOD ± The SCDs in the Bayan Har Mountains, the Anemaqen Mountains, the Inner Mon- same standard for defining theearly SCOD SCED anomaly, year. we It judge is awhich obvious given that was year 1957 also as was the a a reasonand delayed typical or 2004 for year the whose were SCED very great was early. SCDsChina delayed, For except (Table 1, for example, the in Fig. Tibetan 1997, 4e). Plateau,eral, the western The the SCED Tianshan, SCEDs early and was SCED in western early was 1997 Liaoning.Fig. dominant for In and 4f). almost gen- more all evident of than the delayed SCED (Table 1, 3.3.2 SCED trends For the SCED, there are90 % 138 stations level), (39 while %) with 60 % a of significant advancing stations trend show (at no the significant trends (Table 3). Major snow 3.3 Spatiotemporal variations of SCED 3.3.1 SCED variations The pattern of SCEDfall is normally similar show to late thatsnowmelt. of snowmelt, Like SCOD while the (Fig. places SCOD, 7b), with temporal i.e. variations late places of snowfall with SCED normally are early show large snow- early (Table 1). Using the in Northeast China, theYellow River, central North and Gansu, easterntrends and Tibetan dominate North Plateau, the Xinjiang the major (Fig.in upper snow 5b). reach Northeast areas These of China of significantly the China.in is delayed In the consistent particular, with Pan-Bohai theearlier a Bay delaying SCOD. region previous of However, this SCOD study trend and is (Lishan the only Mountains. significant et For Tianshan in example, al., the the Mountains SCOD Liaoxi 2009).a at exhibits corridor delaying Pingliang The and a rate station the in SCOD of Tian- trend Gansu 5.2station Province days towards shows in per Hebei decade Province from 1952 showsto to an 2010 2010, (Fig. advancing but 6e–f). rate the of SCOD 5.2 at days Weichang per decade from 1952 3.2.1 SCOD variations The SCOD issnowfall closely begins related in to Septemberthe both on Daxingganling, the latitude and Tibetan and inThe Plateau, elevation middle SCOD in also (Fig. or early varies late 7a). from oranomaly October one For middle in on year example, October to terms the another on of Altaistations (Table 1). heavy-snow Mountains with Using or of positive the light-snow (negative) Xinjiang. definition(smaller) years, SCOD of than as SCD anomaly the introduced and mean before 30year. % (i.e. stations Only 70 % with two SCOD years,on larger a 1996 large and scale(Fig. 2006, (Table 5d), 1), can while especially not be in any 2006, considered single in year as can East be delayed3.2.2 China considered SCOD and as the years an SCOD Tibetan early trends SCOD Plateau year. There are 136 stationstions (39 (7 %) %) with with a a significantthe trend significant stations of trend show early of SCOD no (both delayed significant at SCOD, trends the and 90 (Table % 3). 23 level), The while sta- delaying 54 % of of SCOD is significant golia Plateau, and Daxingganling,ample, exhibit a for significant the upward Shiquincreased trend station 26 (Fig. days on 5a). from the For 1960itive ex- eastern to trends 2010 in border (Fig. the of 6d). SCDand the The change Li coexistence Tibetan (2012). was of also Plateau, negative reported the and by pos- SCD Bulygina et3.2 al. (2009) and Spatiotemporal Wang variations of SCOD ample, the SCD decreasedNortheast by China, 40 30 days days from from15 1955 days 1954 from to to 1958 2010 2010 to at at 2010 the the at Hongliuhe Kuandian the station Gangcha station in station in Xinjiang, on and the Tibetan Plateau (Fig. 6a–c). 5 5 20 25 15 10 15 20 25 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 39 %) show significant delaying ∼ C (TBZD) plays an important role in ◦ 4485 4486 cient between SCD and MAT during the snow season ffi 39 %) show significant advancing SCED, all at the 90 % ∼ erent time periods used in the two studies, 1972–2007 in Choi et al. (2010) as For the SCOD, there are 287 stations with negative correlations with TBZD, account- ff ing for 82 % of 352(Table 3). stations, This whereas means only that 63 for stations smallerthere (18 TBZD, %) are the show SCOD 318 positive is correlations stations morewhereas delayed. with For only the positive 34 SCED, correlations, stations accounting (10for %) smaller for have TBZD, 90 negative the % correlations SCED of (Table is 3). 352 earlier. This stations, means that 4.2 Relationship with MAT We calculate the correlation coe the SCD. There arebetween TBZD 330 and stations SCD, with (94 %tions 193 (Table 3, of of Fig. them 5d). all (55 For %) example, stations)SCD there having and is showing significantly a TBZD positive positive significantly at correla- positive correlations Chengshantou correlationsmaller between station the (Fig. TBZD, the 8a). shorter Therefore, the generally SCD. speaking, the River (Huajiangling station asof an stations) example, exist Fig. in North 8c),example, Xinjiang, while Fig. the negative Changbaishan 8d), correlations Mountain and (Tonghua (53 the station % coasts as of an Liaoning and the Shandong Peninsula (Fig. 5f). 4.3 Relationship with AO Although the AO index showedet a al., strong 2000), positive its trend impact in on(47 the % the past SCD of decades in (Thompson China stations) isupper spatially are reach distinctive. Positive found of correlations in the central Yangtze River, China, and i.e. the the upper eastern and Tibetan middle Plateau, reaches the of the Yellow SCOD, and 138 stations ( SCOD and advancing SCED.icantly This negative explains SCD why trend, onlySCD while 15 trends. % 75 % The of of latter stationsin stations is show the show inconsistent a Northern no with signif- Hemisphere significantdi the reported change overall by in shortening Choi the of etcompared the al. with (2010). snow 1952–2010 One period inbetween reason this could the study. be Below, spatiotemporal the wechanging variations discuss AO. of the snow possible connections cover and the4.1 warming climate Relationship and with TBZD The number of days with temperature below 0 for each of the 352(91 stations %), (Table 3). but There are only 320tions 32 stations (49 with %) stations negative show correlations (9 %) significantlyat negative have Baicheng correlations. positive station For significantly correlations. example,tions negatively Among the are correlated them, SCD dominant, (Fig. and and 171 8b). MAT exista sta- The close in negative relationship almost correla- with all the snowglobal MAT, clearly areas warming indicating (Fig. during that the 5e). the snow higher That season, the is, MAT the the because shorter of SCD the has SCD. confidence level. It is not necessary for one station to show both significant delaying areas in China allPlateau show (Fig. early 5c). SCED, significantshowing The for a tendency Northeast significant of trend. Chinaadvanced For delayed and example, at SCED the the a Tibetan SCED is at rateMaerkang limited, Jixi station of with station in 4.4 in only Sichuan Northeast days1954 two Province to China per delayed stations 2010 at decade (Fig. a 6g–h). from rate 1952 of to 4.2 days 2010, per while decade4 the from SCED at Discussion In the context of global warming, 136 stations ( 5 5 25 20 20 10 15 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects ff ers from the overall shortening of ff ect of Eurasian snow cover on regional and ff 4488 4487 This work is financially supported by the Program for National Nature Sci- erent time periods used in the two studies, 1972–2007 in the work of Choi ff Long-duration, consistent records of snow are rare in China because of many chal- Northeast China, North Xinjiang, and the Tibetan Plateau are the three major snow It is found that significantly delayed SCOD occurs in Northeast China, the central mogeneity test for linear trends, Int. J. Climatol., 17,global 25–34, climate 1997. variations, J. Atmos. Sci., 46, 661–685, 1989. links to changes in large-scale climatic forcings, Clim. Change, 36, 281–300, 1997. Barnett, T. P., Dumenil, L., and Latif, M.:Beniston, The M: e Variations of snow depth and duration in the Swiss Alps over the last 50 years: Alexandersson, H. and Moberg, A.: Homogenization of Swedish temperature data Part 1: Ho- Fund for the Doctoral Programis of Higher also Education of partially Chinaand supported (No. 20120091110017). Industrialization. by This We work Collaborative would InnovationBeijing for like Center providing to of valuable climate thank Novel datasets. the Software National Technology Climate Center of ChinaReferences (NCC) in ence Foundation of China (No. 41371391), and the Program for the Specialized Research analyse the spatiotemporal distributionspheric and circulation features causes of snow variabilityalso cover require in phenology. deeper the Atmo- investigation. snow cover phenology,Acknowledgements. and these e lenges associated with taking accurate andwestern representative measurements, China. especially The in density oflocality. stations Therefore, and more the choice accurate of and metric reliable also observation vary data with time are and needed to further are mostly controlled by1950s, the local reduced latitude TBZD and andSCOD increased elevation. MAT and are Owing early the SCED, to main although reasonssignificantly global it for is delayed overall warming not delayed SCOD since necessary and forshow early one significantly SCED. station negative This to SCD trends, experience explains while both trends. why 75% only of stations 15 % show no of significant stations SCD inter-annual variability of SCD1957, is large. 1964, The and heavy-snow 2010,2009. years in while Only China the 15 include % light-snowstations 1955, of years show stations are no show 1953, significant a 1965, SCD significantly 1999, trends. negative 2002, SCD This and trend, di while 75 % of regions, with Northeast Chinanorth-eastern being China, the the largest. SCDs are InPlateau, concentrated however, North snowfall in is Xinjiang the more and winter frequent season. in in On central the the and spring Tibetan and fall. In China, the overall 5 Conclusions This study examines theChina. snow Specifically, cover the change 352 based stationsto on with study 672 more the stations than changingTBZD, in ten trends MAT, and 1952–2010 annual of AO mean in SCD, index SCDs SCOD, duringrized and are snow below. used SCED, seasons. and Some SCD important relationships results are with summa- the snow period inbe the the Northern di Hemisphere previously reported. One reason could and eastern Tibetan Plateau,North the Xinjiang; upper significantly reach of earlyPlateau. the Both SCED Yellow the occurs River, North SCOD in Gansu, and Northeast and SCED China are and closely the related Tibetan to the TBZD and MAT, and et al. (2010) comparedSCD with distribution pattern 1952–2010 and inby trends this any in study. China single Our are climate analysesof very variable multiple indicate complex examined variables. and that However, (i.e. it are the SCD TBZD, seems not MAT, that shortening controlled or the trends AO), AO in but indexXinjiang; has the the a the combination Shandong combination most of Peninsula, impact smalleron Changbai on TBZD the Mountains, SCD the and shortening increasing and trends MAT North onPlain. has the the Loess largest Plateau, Xiaoxingganling, impact and the Sanjiang 5 5 25 20 15 10 10 15 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4490 4489 and spring from 1961China, to Sci. 2010 Agricul. Sin., and 47, its 1754–1763, possible 2014. impacts on2196, wheat 2009. in wheat planting area of Geophys. Res. Lett., 28, 2073–2076, 2001. balance and the rise of continental spring temperatures, Science,Austria, 263, Int. 198–200, J. 1994. Climatol., 20, 615–640, 2000. of vulnerability of animal husbandry in China, J. Nat.with Disaster, Arctic 11, oscillation, 42–48, Geophys. 2002. Res. Lett., 32, L14704, doi:10.1029/2005GL023024,Dynam., 2005. 41, 589–600, 2013. plateau, Acta Geogr. Sin., 53, 209–215, 1998. China, Clim. Res., 59, 15–26, 2014. China, Theor. Appl. Climatol., 98, 251–258, 2009. boundary conditions, J. Hydrol., 384, 14–25, 2010. by andoi:10.1029/2011GL048927, altitudinal 2011. gradient and terrainProvince in roughness, 1951–2006, J. Glaciol. Geophys. Geocrol., 31, Res. 1011–1018, 2009. 1632, Lett.,, doi:10.1029/2003GL017441 2003. 38, L19504, ulating an extreme hydrological event810, in 2011. the Severn Uplands, UK, Hydrol. Process., 2,atmospheric 795– circulation, Int. J. Climatol., 34, 134–144, 2014. Great Lakes, Nat. Hazards, 5, 221–232, 1992. change over 1922–2010 including229, an doi:10.5194/tc-5-219-2011 , assessment 2011. of uncertainty, The Cryosphere, 5,ern 219– Eurasia in9326/4/4/045026, 2009. the last few decades, Environ.in Res. the United Lett., States, Nat. 4, Hazards, 37, 045026, 373–389, 2006. doi:10.1088/1748- China and their1712–1724, relationship 2013. with the Arctic Oscillation andChina Meteorological ENSO, Press, Adv. Beijing, 1–62, Atmos. 2003. Sci., 30, Climate, 23, 5305–5310, 2010. and implicationsdoi:10.1029/2007GL031474, 2007. for the snow-albedodays feedback, in Northern Geophys. Xinjiang in recent Res. 40 years, Plateau Lett.,Xizang Meteorol., Plateau 23, livestock 936–940, 34, farm, 2004. Plateau Meteorol., L22504, 20, 402–406, 2001. America, Geophys. Res. Lett., 33, L16503, doi:10.1029/2006GL027258, 2006. Fang, S., Qi, Y., Han, G., Zhou, G., and Cammarano, D.: Meteorological drought trend in winter Gao, H.: China’s snow disaster in 2008, who is theGong, principal player?, D. Int. Y., J. Wang, Climatol., S. 29, 2191– W., and Zhu,Groisman, J. P. H.: Y., Karl, East T. Asian R., winter and monsoon Knight, andHantel, R. Arctic M., W.: oscillation, Observed Ehrendorfer, impact M., of and snow Haslinger, cover A.:Hao, on L., Climate Wang, the J., sensitivity heat- Man, of S., and snow Yang, C.: Spatio-temporal cover change duration ofJeong, snow in disaster J. and H. analysis and Ho, C. H.: Changes in occurrenceJi, of Z. cold surges and over Kang, East S.: Asia Projection in of association snow coverKe, changes C. over China Q. under and RCP Li, scenarios, Clim. P. J.:Ke, Spatial C. Q. and and Liu, temporal X.: characteristics MODIS-observed spatial of and temporal snow variationKe, cover in C. snow over cover Q., in the Yu, Xinjiang, T., Tibetan Yu, K., Tang, G.Kuhlman, D., and K. King, L. L.: and Snowfall trends Igúzquiza, and E. variabilityLehning, P.: in Universal Qinghai, M., cokriging of Grünewald, hydraulic heads T., accounting and for Schirmer,Li, D., Liu, M.: Y., Yu, H., Mountain and Li, snowLi, Y.: Spatial–temporal J. distribution variation and of Wang, governed the J.: snow A cover modified in zonal Heilongjiang index and its physical sense, Geophys. Res. Lett., 30, Biggs, E. M. and Atkinson, P. M.: A comparison of gauge and radarBirsan, precipitation M. data V. for and sim- Dumitrescu, A.:Bolsenga, Snow S. J. variability and Norton, in D. C.: Romania Maximum snowfall in at long-term connection stationsBrown, in to the R. U. large-scale S./Canadian D. and Robinson, D. A.: Northern HemisphereBulygina, spring O. N., snow Razuvaev, cover V. N., variability and and Korshunova, N. N.: Changes in snowChangnon, cover S. over A. North- and Changnon, D.: A spatial andChen, temporal analysis S., of Chen, damaging W., snowstorms and Wei, K.: Recent trends inChina Meteorological winter Administration: temperature Specifications extremes for in Surface eastern Meteorological Observations, Choi, G., Robinson, D. A., and Kang,Déry, S.: S. Changing Northern J. Hemisphere and snow seasons, Brown, J. R. D.:Dong, A., Recent Guo, H., Northern Wang, L., Hemisphere and Liang, snowDong, T.: W., A cover Wei, CEOF Z., extent analysis and on Fan, trends J.: variation Climatic about characterDyer, yearly analysis J. snow of L. snow and disasters Mote, in T. east L.: Qinghai- Spatial variability and trends in observed snow depth over North 5 5 10 20 15 25 30 30 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4492 4491 impacts on vegetation in China, Glob. Change Biol., 16,ogy 3004–3013, and 2010. its potential feedbackdecades, to temperature Environ. in Res. the Lett., Northern 8, Hemisphere 014008, over doi:10.1088/1748-9326/8/1/014008, the 2013. last three in western China, J. Climate, 19, 1820–1833, 2006. changes of China’s mainland2005. over the past half century, Acta Meteorol.sphere Sin., snow 63, cover, 942–956, Geophys. Res. Lett., 17, 1557–1560, 1990. the role ofdoi:10.1029/2004GL020255, 2004. local- and large-scale climatedence of variability, the Geophys. snowfall/precipitation-day ratio indoi:10.1029/2011GL046976, Res. Switzerland, 2011. Geophys. Lett., Res. Lett., 31, 38, L07703, L13215, as simulated by adoi:10.1088/1748-9326/6/4/045401, 2011. high resolution regional climate model, Environ.40 years, Res. Acta. Lett., Geogr. Sin., 6, 67, 045401, 951–959, 2012. tential height and temperature fields, Geophys. Res. Lett., 25,circulation, 1297–1300, part 1998. II: Trends, J. Climate, 13, 1018–1036, 2000. depth of snow2012. cover in China during recent 50tion years, and interannual J. variation, Glaciol. J. Glaciol. Geocrol., Geocrol., 34, 31, 301–310, 247–256, 2009a. based on moderate-resolution-imaging spectroradiometer084695,,10.1117/1.JRS.8.084695 doi: data, 2014. J. Appl. Remote Sens., 8, Sin., 48, 433–437, 1990. 515, 1993. application of MODISNorthern data Xinjiang, to China, Remote snow Sens. cover Environ., 112, monitoring 1514–1526, in 2008. 2012. a pastoral area: a case study2010 in in Catalonia (Spain):Hazards a Earth paradigmatic Syst. wet-snow Sci., event 14, with 427–441, a, doi:10.5194/nhess-14-427-2014 high 2014. societalautumn/winter impact, Nat. snow depth,doi:10.1029/2007JD009567 2008. over the Tibetan Plateau,in J. China during Geophys. 1957–2009, Sci. Res., Cold Arid 113, Reg., 4, D14117, doi:10.1029/2008GL033998, 384–393, 2008. 2012. and precipitation on snowpackRes. variability Lett., in 40, Switzerland 2131–2136, 2013. as a function ofof altitude, the Geophys. recent1811–1816, snowpack 2013. decline in the Rocky Mountains,Siberian U. snow and S., Arctic Oscillation Geophys. over2013. the Res. 20th century, Lett., Geophys. Res. 40, Lett., 40, 183–188, Peng, S., Piao, S., Ciais, P., Fang,Peng, J., S., Piao, and S., Wang, Ciais, P., Friedlingstein, X.: P., Zhou, Change L., in and Wang, winter T.: Change snow in depth snowQin, phenol- and D., Liu, its S., and Li, P.: Snow cover distribution,Ren, G. variability, and Y., Guo, response J., Xu, to M. climate Z., change Chu, Z. Y., Zhang, L., Zou, X. K., Li,Robinson, Q. D. X., A. and Liu, and X. Dewey, N.: K. Climate F.: RecentScherrer, secular variations S. in C., the extent Appenzeller, of C., Northern and Hemi- Laternser,Serquet, M.: G., Marty, Trends C., Dulex, in J. P., and Swiss Rebetez, M.: Alpine Seasonal trends snow and temperature days: depen- Shi, Y., Gao, X., Wu, J., and Giorgi, F.: Changes in snow cover overTang, X., China Yan, in X., the Ni, 21st M., century and Lu, Y.: ChangesThompson, D. of W. J. the and snow Wallace, J. cover M.: days The on Arctic Tibet oscillation signature PlateauThompson, in in the D. last wintertime W. geopo- J., Wallace, J. M.,Wang, and C. Hegerl, and G. Li, D.: C.: Spatial–temporal Annular variations modes of in the the snowWang, extratropical C., cover Wang, days Z., and and Cui, the Y.: Snow maximum cover of China during the last 40 years: spatial distribu- Li, L. Y. and Ke, C. Q.: Analysis of spatiotemporal snowLi, cover P. J.: variations A in preliminary study Northeast of China snow massLi, variations over P. J.: past Dynamic 30 characteristic years of in snow China, cover Acta in Geogr. westernLi, China, P. J. Acta and Meteorol. Mi, Sin., D.:Liang, Distribution 48, T. of 505– G., snow cover Huang, in China, X. J. D., Glaciol. Wu, Geocrol., 5, C. 9–18, X., 1983. Liu,Liu, X. Y., Ren, Y., G., Li, and W. Yu, L., H.: Guo, ClimatologyLlasat, Z. of M. snow C., G., Turco, in M., and Quintana-Seguí, China, Ren, P., Sci. and J. Llasat-Botija, Geogr. M.: Z.: Sin., The 32, An snow 1176–1185, storm ofLü, 8 March J. M., Ju, J. H., Kim,Ma, L. S. and Qin, J., D.: Temporal-spatial Ren, characteristics of J. observed keyMarty, parameters Z., of C.: snow and cover Regime Zhu, shift Y. of X.:Morán-Tejeda, E., snow Arctic López-Moreno, days J. Oscillation I., in and and Beniston, Switzerland, the M.: Geophys. The changing Res. rolesPederson, Lett., of G. temperature T., 35, Betancourt, J. L12501, L., and Gregory, J. M.: Regional patterns and proximalPeings, Y., causes Brun, B., Mauvais, V., and Douville, H.: How stationary is the relationship between 5 5 10 15 20 25 30 20 30 10 15 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1SD N − 2SD − 1 4 15 85 35 5 erent glacier status with atmo- ff to climatic change in an inland river ff 1SD N P 1SD 2SD − 2SD − 4494 4493 40 8 2 2 18 60 3956 9 18 1 5 9 1 17 9 61 44 56 14 2 3 16 44 1SD N P 1SD 2SD − 2SD − 3 34 70 10 5 3 20 35 15 8 250 5 31 1 1 1 33 0 23 24 75 30 3 14 65 78 1 75 21 2 4 1 23 5 70 66 17 22 1 0 5 34 Percentage (%) of stations with anomalies (P for positive and N for negative) of snow one or two SDs (1 SD or 2 SD), with the bold number denoting extremely heavy-snow SCD30 6 0 SCOD SCED 25 8 0 ± spheric circulations in Tibetan Plateau2012. and surroundings, Nature Clim. Change, 2, 663–667, Geophys. Res. Lett., 30, 1252, doi:10.1029/2003GL016873, 2003. in snow depth andRes., number 46, of 171–183, snow 2011. days in the easternRev. and Geophys., 43, central 1–23, Tibetan 2005. Plateau, Clim. basin, Northwestern China, over the,doi:10.5194/hess-14-1979-2010 past 2010. 50 years, Hydrol. Earth Syst. Sci., 14, 1979–1987, Y., Wang, Y. M., Chen,heavy L. snowstorm J., and freezing and disasters100, Gao, in 2008. H.: January Characteristics 2008 of in the China, Meteorol. extreme Mon., low-temperature, 34,snow 95– cover in Northern Xinjiang, Adv. Clim. Change Res.,warning 5, 39–43, of 2009b. snow-caused disastersEarth in Syst. Sci., pastoral 13, areas 1411–1425, on doi:10.5194/nhess-13-1411-2013 , the 2013. TibetanGeophys. Plateau, Res. Nat. Lett., Hazards 29, 1897, doi:10.1029/2002GL015373 , 2002. in Hetao and its vicinity, J. Glaciol. Geocrol., 31, 446–456,Tibetan 2009. Plateau, Plateau Meterol., 29, 1093–1101, 2010. China during 1961–2010, Theor. Appl. Climatol., 120, 773–783, 2015. B., Pu, J., Lu, A., Xiang, Y., Kattel, D. B., and Joswiak, D.: Di Year P1952 1SD1953 33 2SD 5 0 12 31 67 67 39 21 2 12 33 57 17 2 11 16 43 19541955 59 80 29 48 111958 29 1959 45 0 27 151960 61961 37 41962 34 12 81963 40 7 1 2 01964 24 10 41 77 5 1 4 3 0 36 391966 14 81967 27 1 1 11 01968 32 7 23 15 551969 59 7 4 1 461970 45 28 19 1 73 10 17 63 44 211971 1 1 55 11 47 141972 52 25 0 27 66 0 8 60 101973 56 12 3 24 3 1 43 171974 49 24 9 76 9 2 1 0 4 131975 34 19 12 33 11 21976 40 9 23 8 1 64 13 2 4 2 2 1 35 91977 57 73 0 19 21 11 45 5 0 12 68 46 10 1 2 1 41 17 20 3 39 20 13 11 3 54 55 37 0 7 1 3 10 3 51 56 45 9 5 45 1 28 10 7 16 53 1 37 13 48 3 0 57 60 0 10 44 38 26 1 23 0 22 3 1 76 57 25 38 14 14 1 51 3 22 29 60 9 10 3 0 67 66 37 5 4 9 3 6 3 18 12 52 60 55 10 3 2 65 14 1 14 26 30 3 43 4 1 1 58 13 1 54 7 55 17 19 1 24 0 6 61 69 29 26 0 5 9 1 63 44 12 5 17 17 2 11 49 55 8 1 33 4 20 63 68 1 13 0 11 1 43 40 1 28 64 21 63 22 0 18 62 54 16 0 10 1 1 40 0 45 8 5 71 63 21 3 3 16 4 48 45 44 1 4 1 54 9 24 4 0 74 42 12 11 42 76 27 1 7 1 31 1 14 71 29 1 6 56 55 67 3 5 1 14 9 1 32 9 36 3 3 1 8 46 9 55 2 17 3 56 46 12 58 24 45 19561957 48 85 11 64 0 29 0 41965 52 70 20 2 0 8 30 62 23 1 2 12 38 Ye, H. and Ellison, M.: ChangesYou, in Q., transitional Kang, snowfall S., season Ren, G., length Fraedrich, in K., northern Pepin, N., Eurasia, Yan, Y.,Zhang, and T.: Ma, Influence L.: of Observed the changes seasonal snow cover on the ground thermal regime: an overview, Wang, Q., Zhang, C., Liu, J., andWang, Liu, W., W.: The Liang, changing T., tendency Huang, on X., the Feng, depth Q., and Xie, days H.,Wu, of B. Liu, Y. and Wang, X., J.: Winter Chen, Arctic M., oscillation, Siberian and highXi, and Wang, East Y., Li, X.: Asian winter D., Early monsoon, and Wang, W.: Study ofXu, the temporal-spatial L., characteristics Li, of D., snow and covers days Hu, Z.:Yang, H., Yang, Relationship D., Hu, between Q., and the Lv, H.: snow Spatial variability cover of the day trends and in climatic monsoon variables across index in Yao, T., Thompson, L., Yang, W., Yu, W., Gao, Y., Guo, X., Yang, X., Duan, K., Zhao, H., Xu, Table 1. cover day (SCD),percentage snow (%) cover of stations onset withmean date anomalies of (SCOD), SCD, SCOD, and andor snow SCED light-snow years larger cover for (smaller) the end thanChina. SCD, the and date extremely (SCED), delayed or and early (for SCOD or SCED) years, for Wang, L., Gao, G., Zhang, Q., Sun, J. M., Wang, Z. Y., Zhao, Y., Zhao, S. S., Chen, X. Y., Chen, Wang, J., Li, H., and Hao, X.: Responses of snowmelt runo 5 25 30 10 15 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1SD N 1SD N − − 2SD 2SD − 4247 4 5 87 0 97 0 0 0 5 19 49 2 86 − 9 50 82 12 35 70 40 0 3 1176 2 10 3161 60 2 0 7 0 11 24 2 39 95 2481 38 3 38 1SD N P 1SD 2SD 1SD N P 1SD 2SD − − 2SD 2SD − 00 0 0 11 45 033 3 225 00 19 15 00 0 5 95 00 29 5 029 0 5 40 2 0 43 6 19 0 55 248 510 17 78 5 90 5 10 5 6 44 0 3 2 16 95 0 2 11 0 0 10 14 60 0 0 57 0 5 49 56 − 0 4 28 56 10 10 2 5 14 28 44 59 15 0 1 10 41 4496 4495 6224 05 0 5 0 0 5 0 19 10 5 38 76 77 20 11 0 24 2 2 13 0 0 23 80 95 0 71 10024 26 0 58 75 0 0 20 1995 10 5 5100 0 10 57 7695 62 22 25 0 0 26 0 48 0100 7 10 27 14 55 0 0 78 74 72 30 4 59 23 1257 21 1 472 7 1 32 7 4173 5 51 23 13 9 43 2 32 0 6 7 0 4 16 12 27 49 29 30 4 68 0 3 25 71 1SD N P 1SD 2SD 1SD N P 1SD 2SD − − 2SD 2SD − 494338 13 21 12 95 96 94 058 0 14 2 99 89 20 0 0 44 0 30 0 80 773 12 42 0 4 8 0 23 3543 50 13 87 80 0 10 38 0 0 5 10 62 34 2 10 20 0 66 − 1 32 77 1 355 76 31 83 0 9 25 41 10 1 1 21 59 73 19 1 1 7 27 The same as Table 1, but only for the SCD and only for the three major stable snow Continued. Northeast China98 20 54 North Xinjiang Tibetan Plateau 92 17 50 90 4 55 SCD SCOD26 735 3 2 0 2 SCED 1 22 18 74 65 4623 16 5 3 0 2 12 54 18 4 2 24 417 1 233 3 0 49 11 1 2 0 0 17 8 67 43 51 12 2 1 25 57 30 7 1 20022008 4 6 0 0 0 0 Year P1957 1SD 2SD 1977 74 5 26 51998 5 0 02010 26 0 1959 1 0 0 19601963 421965 13 11967 68 01969 20 1 151973 23 0 0 24 0 23 0 131980 0 31983 621988 63 1 1 26 58 1990 71 3 39 01994 16 14 32 01995 95 19 8 24 32 1 23 3 77 0 0 0 3 75 26 0 1 13 0 0 0 0 0 13 38 30 1 38 37 0 5 29 24 4 0 61 0 33 5 0 68 76 0 0 10 13 25 0 0 5 24 3 4 0 19 0 0 0 0 76 67 1974 53 0 17 18 3 47 5 0 0 Year P1978 1SD1979 58 2SD 41 211980 91981 39 81982 42 111983 39 12 1 1 01984 48 11 21985 27 19 0 1 0 68 101986 2 6 0 251987 49 2 11988 66 14 7 5 3 01989 56 22 42 12 2 11990 48 16 45 15 4 59 0 56 191991 13 61 15 1 43 0 58 191992 33 43 28 4 10 0 61 481993 52 4 2 9 3 2 0 52 25 211994 59 14 1 13 0 73 45 91995 59 18 0 2 1 4 4 3 0 69 141996 34 18 32 2 0 2 33 51 101997 2 2 31 1 11 1 2 2 1 33 12 8 34 16 6 3 1 5 0 44 39 18 1 0 52 10 55 0 23 6 16 17 1 7 3 70 1 53 44 6 4 57 28 29 10 50 67 11 1 4 1 78 57 52 5 1 9 48 60 1 7 19 25 82 44 1 75 41 55 24 2 28 55 13 58 41 45 17 2 23 1 3 1 31 65 66 19 5 0 24 27 9 2 1 46 25 582007 5 6 15 0 0 69 8 23 62008 28 0 67 29 2 6 1 0 2 48 8 46 52009 0 61 2 3 9 61 1 21 6 17 4 8 1 0 77 62 3 1 30 3 14 47 1 71 26 5 1 2 3 4 2 43 25 16 22 50 5 0 10 3 16 56 40 3 1 18 4 49 0 25 15 45 73 13 42 11 1 1 35 55 52 26 23 1 19 73 48 14 8 42 12 1 54 3 3 41 17 48 8 72 1 11 8 54 2 39 7 68 2 52 1 69 17 24 0 5 27 1 38 2 10 29 5 4 3 57 6 8 18 51 1 21 0 27 17 48 20 52 5 8 59 52 32 31 28 42 3 9 1 1 9 4 28 23 72 58 19981999 332000 72001 632002 67 16 2 282003 42004 58 3 72005 28 02006 61 4 0 20 17 5 1 1 67 52010 39 0 75 37 12 8 40 33 60 3 38 18 4 11 15 42 2 1 35 1 39 5 0 47 19 1 15 1 9 2 61 0 22 32 0 11 40 62 20 37 1 42 6 12 17 65 7 52 0 1 53 9 35 25 4 3 4 1 68 0 22 15 6 2 63 58 18 19 48 65 Table 2. regions: Northeast China, North Xinjiang and the Tibetan Plateau. Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | a 95% 90% I a C TBZD ◦ for insignificant. a 4498 4497 95% 90% I a SCD SCOD SCED Mean Air TemperatureArctic Oscillation MAT AO Snow Cover DaySnow Cover Onset DateSnow Cover End DateDays with Temperature Below 0 SCOD SCD SCED 95% 90% I N 38N 54 0N 127 129 0 13N 171 33 23 22 149 82 64 69 106 93 92 138 194 0 169 2 32 Number of stations with SCD, SCOD, and SCED trends, number of stations with Abbreviations. Trend PTBZD 18 P 35MAT 156 193 P 136AO 0 93 137 0 P 136 2 35 2 124 87 30 1 77 63 2 85 115 43 203 Note: Positive (P) or Negative (N) trends or relations, I Table 4. relationships of SCD, SCOD, andlationship between SCED, SCD respectively, with and TBZD, MAT,AO. and number All number of of of them stations stations have with with two relationship re- significance between levels, the SCD 90 and and 95%. Table 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . (b) cients of variation (CV) ffi , and their coe (a) 4499 4500 Locations of weather stations and major basins, mountains and plains mentioned in Annual mean snow cover days (SCDs) Figure 2. Figure 1. the paper, overlying the digital elevation model for China. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . (f) , snow cover onset date (SCOD) in (c) , and 1997 (e) , 2008 (b) 4501 4502 , 2002 (a) SCD anomalies in 1957 Seasonal variation of SCDs; the number in the centre denotes annual mean SCDs, , and snow cover end date (SCED) in 1957 (d) Figure 4. 2006 Figure 3. the blue colour inred the colour circle for the autumn. SCDs for winter season, the yellow colour for spring, and the Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | N, N, 0 0 and 32 59 ◦ ◦ (g) e, f, g, h , and Arctic (e) and Weichang (e) E, 280.8 m) and Shiqu (32 0 , Hongliuhe (41 from the 352 stations of 56 (a) ◦ (c) (c) axis in the figures Y E, 1412.0 m) N, 130 0 0 40 18 ◦ ◦ E, 260.1 m) 0 E, 3301.5 m) , and SCED 0 47 ◦ N, 106 (b) 08 0 ◦ , mean air temperature (MAT) 33 ◦ N, 124 (d) . (The unit on the 0 4503 4504 N, 100 , SCOD (h) 43 0 ◦ (a) 20 ◦ C (TBZD) ◦ , and SCED in Jixi (45 (f) E, 2664.4 m) 0 54 ◦ . , Gangcha (37 , SCOD in Pingliang (35 (f) (b) (d) E, 842.8 m) N, 102 0 0 45 54 ◦ ◦ SCD variations in Kuandian (40 Trends of annual mean SCDs N, 117 E, 1573.8 m) E, 4533.0 m) 0 0 0 56 40 06 ◦ ◦ ◦ Oscillation (AO) index Figure 6. 94 Figure 5. more than ten annualand mean SCDs day with with Mann–Kendall temperature test, below and 0 relationships among the SCD 98 (41 Maerkang (31 denotes the Julian day using 1 September as reference.) Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , N, 0 (a) 23 ◦ E, 47.7 m) 0 41 ◦ . (d) N, 122 0 24 ◦ E, 402.9 m) 0 based on the stations with an average 54 , and AO index for Huajialing (35 ◦ (b) (b) N, 125 0 4505 4506 41 ◦ and SCED (a) E, 1229.2 m) 0 54 ◦ N, 81 0 , and Tonghua (41 47 ◦ (c) SCD relationships with TBZD for Chengshantou (37 Spatial distribution of SCOD E, 2450.6 m) 0 00 ◦ Figure 8. MAT for Baicheng (41 105 Figure 7. of more than ten SCDs.