observed degree day factors and their spatial variation on glaciers in western china the degree day factor ddf is an important parameter for the degree day model which is a widely used method for ice and snowmelt computation spatial variations of the ddf greatly affect the accuracy of snow and ice melt modelling this study analyzes the spatial variability of ddfs obtained from observed glaciers in different regions of western china the results clearly show that the ddf for a single glacier is subject to significant small scale variations and the factor for maritime glaciers is higher than that for subcontinental and extremely continental glaciers in western china the factors increase gradually from northwest to southeast in general the regional patterns of ddfs are detectable on the glaciers due to the unique climatic environment and heat budget of the tibetan plateau and surrounding regions low ddfs can be expected for cold dry areas whereas high ddfs can be expected for warm wet areas in western china depending on spatial variation of the characteristics of ddfs and the meteorological data we can provide gridded degree day models for non monitored glaciers to reconstruct gridded historical glacier mass balance series in western china

can the mass balance of a glacier be estimated from its equilibrium line altitude the possibility of replacing or supplementing direct measurements of mass balance by estimates calculated from equilibrium line altitude ela measurements is investigated by statistical analyses of data from 31 glaciers a linear relationship between mass balance and ela in terms of two parameters the effective balance gradient and the balanced budget ela is tested it is concluded that existing mass balance series can be usefully extrapolated by using ela data for additional years however accurate mass balance cannot be calculated for glaciers where no such measurements have been made because of the difficulties in prescribing the two model parameters with sufficient accuracy for example the effective balance gradient is of the order of 5 mm water m so that errors of only a few decametres in the estimation of the balanced budget ela can have a great effect upon calculations of mass balance

arctic sea ice variability in the context of recent atmospheric circulation trends abstract forty years 1958 97 of reanalysis products and corresponding sea ice concentration data are used to document arctic sea ice variability and its association with surface air temperature sat and sea level pressure slp throughout the northern hemisphere extratropics the dominant mode of winter january march sea ice variability exhibits out of phase fluctuations between the western and eastern north atlantic together with a weaker dipole in the north pacific the time series of this mode has a high winter to winter autocorrelation 0 69 and is dominated by decadal scale variations and a longer term trend of diminishing ice cover east of greenland and increasing ice cover west of greenland associated with the dominant pattern of winter sea ice variability are large scale changes in sat and slp that closely resemble the north atlantic oscillation the associated sat and surface sensible and latent heat flux anomalies are largest over the portions of the marginal sea ice zone in which the tr

late twentieth century northern hemisphere sea ice record from u s national ice center ice charts 1 arctic sea ice plays a key role in the climate system by acting as the interface between a warm ocean and a cold atmosphere establishing the true pattern of recent behavior of the sea ice in this region is critical to simulating the role of sea ice in future climate recently released operational ice charts from the u s national ice center provide insight into the late twentieth century behavior of northern hemisphere sea ice providing more reliable ice concentrations during summer and freeze up than those available from the passive microwave record the major winter and summer modes of ice concentration variability observed from empirical orthogonal function analysis covering the period 1972 1994 are shown to indicate respectively the 1 year lagged response of the sea ice to the north atlantic oscillation and the winter preconditioning of summer sea ice coverage in the eastern arctic by the north atlantic oscillation feedback to the atmosphere is suggested in each case by zero lag cyclone frequency relationships to these two sea ice modes of variability

equatorial undercurrents associated with indian ocean dipole events during contrasting summer monsoons 1 positive indian ocean dipole iod events generally tend to be accompanied by intensified summer monsoon flows and above normal precipitation over the sub continent although strong monsoons have not always coincided with positive iod events numerical simulation experiments and supplementary data diagnostics are performed to understand the iod sub surface dynamics in relation to the monsoon strength the model experiments when forced by iod winds during strong monsoon periods generated a strong subsurface zonal pressure gradient along the equator and an eastward equatorial undercurrent euc leading to supply of cold subsurface waters to the upwelling regions in the eastern equatorial indian ocean however the simulations when forced with iod winds during weak monsoon periods were unable to set up the subsurface pressure gradients and the euc thus resulting in weak sst cooling in the east these results raise the possibility that iod monsoon interactions during strong monsoon years might favor intensification of the iod

challenges and recommendations in mapping of glacier parameters from space results of the 2008 global land ice measurements from space glims workshop boulder colorado usa on 16 18 june 2008 the us national snow and ice data center held a glims workshop in boulder co usa focusing on formulating procedures and best practices for operational glacier mapping using satellite imagery despite the progress made in recent years there still remain many cases where automatic delineation of glacier boundaries in satellite imagery is difficult error prone or time consuming this workshop identified six themes for consideration by focus groups 1 mapping clean ice and lakes 2 mapping ice divides 3 mapping debris covered glaciers 4 assessing changes in glacier area and elevation through comparisons with older data 5 digital elevation model dem generation from satellite stereo pairs and 6 accuracy and error analysis talks presented examples and work in progress for each of these topics and focus groups worked on compiling a summary of available algorithms and procedures to address and avoid identified hurdles special emphasis was given to establishing standard protocols for glacier delineation and analysis creating illustrated tutorials and providing source code for available methods this paper summarizes the major results of the 2008 glims workshop with an emphasis on definitions methods and recommendations for satellite data processing while the list of proposed methods and recommendations is not comprehensive and is still a work in progress our goal here is to provide a starting point for the glims regional centers as well as for the wider glaciological community in terms of documentation on possible pitfalls along with potential solutions

distinct quasi biweekly features of the subtropical east asian monsoon during early and late summers using global precipitation climatology project daily rainfall and era interim reanalysis data we investigate the distinct characteristic of quasi biweekly variation qbv 12 20 days over east asia ea during early june 10 july 20 and late july 21 august 31 summer the qbv maximum variance is found over the core region of ea 30 40 n 110 130 e which includes eastern china lower reaches of the yellow huaihe and yangtze rivers and the korean peninsula at both its peak wet and dry phases qbv over the core region has a baroclinic structure but with different spatial distributions different lower level prevalent wind anomalies and different upper level major circulation anomalies in the two subseasons meanwhile the two subseasons have different propagating tracks prior to reaching the peak phase and different precursors associated with the local genesis of qbv furthermore during the transition from the peak dry to peak wet phase of qbv the major monsoon circulations have different behaviors that tropical monsoon trough extends eastward in early summer but retreats westward in late summer and the south asia high sah and western north pacific wnp subtropical high move toward away from each other in early late summer the abrupt change of mean state in mid to late july which includes the northward migration of westerly jet sah and wnp and the weakening and broken of westerly jet is considered the root cause of the change in behavior of qbv finally we indicate that the tropical monsoon trough and midlatitude westerly jet are possible sources of qbv over subtropical ea in both subseasons and provide useful guidance for 2 3 week predictions over ea

contrasting patterns of early twenty first century glacier mass change in the himalayas glaciers are among the best terrestrial climate indicators an important water resource in mountains1 2 and a major contributor to global sea level rise3 4 in the hindu kush karakoram himalaya region hkkh a paucity of appropriate glacier data has prevented a comprehensive assessment of current regional mass balance5 however there are indirect evidences of a complex pattern of glacial responses5 8 in reaction to heterogeneous climate change signals9 here we provide the first coherent data set of detailed glacier thickness changes over the hkkh during 2003 2009 by combining satellite laser altimetry and a global elevation model in the eastern central and south western parts of the hkkh glacier wastage is widespread with regional thinning rates up to 0 66 0 09 m a 1 in the jammu kashmir region conversely in the karakoram glaciers are close to balance with only a slight thinning of 0 07 0 04 m a 1 regionally averaged thinning rates under debris mantled ice are similar to those of clean ice despite insulation by debris covers the 2003 2008 specific mass balance for our hkkh study region is 0 21 0 05 m a 1 water equivalent we significantly less negative than the global average of 0 7 m a 1 we for glaciers and ice caps4 10 this difference is mainly an effect of the balanced glacier mass budget in the karakoram the corresponding hkkh sea level contribution is 0 035 0 009 mm a 1 amounting to 1 of the present day sea level rise11 our 2003 2008 mass budget of 12 8 3 5 gt a 1 is more negative than recent satellite gravimetry based estimates of 5 6 gt a 1 over 2003 2010 ref 12 for the mountain catchments of the indus and ganges basins13 the glacier imbalance contributes 3 5 and 2 0 respectively to the annual average river discharge13 and up to 10 for the upper indus basin14

subsurface equatorial zonal current in the eastern indian ocean 1 variations of subsurface zonal current in the eastern equatorial indian ocean are investigated by examining 6 year data december 2000 november 2006 from acoustic doppler current profiler adcp mooring at 0 s 90 e the analysis indicates the presence of an eastward equatorial subsurface current between 90 and 170 m depths during both boreal winter and summer during boreal winter the generation of eastward pressure gradient which drives an eastward flow in the thermocline is caused primarily by upwelling equatorial kelvin waves excited by prevailing easterly winds on the other hand the downwelling rossby waves generated by the reflection of the spring downwelling kelvin waves in the eastern boundary as well as the upwelling equatorial kelvin waves triggered by easterlies create an oceanic state that favors the generation of the eastward pressure gradient during boreal summer the subsurface current reveals a distinct seasonal asymmetry the maximum eastward speed of 63 cm s 1 is observed in april and secondary maximum of 49 cm s 1 is seen in october the zonal transport per unit width within depth of the subsurface current exhibits similar variations reaching maximum eastward transport of 35 m2 s 1 in april and secondary maximum of 29 m2 s 1 in october moreover the subsurface current during boreal summer undergoes significant interannual variations it was absent in 2003 but it was anomalously strong during 2006

equilibrium line altitudes of the last glacial maximum for the himalaya and tibet an assessment and evaluation of results abstract contemporary equilibrium line altitudes elas for glaciers in the high mountains of the himalaya and tibet have considerable variation because the region is influenced by two major climatic systems the mid latitude westerlies and the south asian summer monsoon and glaciers are subject to strong topographic controls reconstructions of past elas based on the former extent of glaciers are numerous but were estimated using a variety of methods some of which are not appropriate for high altitude glaciers which are strongly influenced by topography and have extensive supraglacial debris cover furthermore few of the reconstructions have adequate chronological control because of the difficulty of dating glacial landforms in high altitude regions where organic matter for radiocarbon dating is sparse or absent cosmogenic radionuclide surface exposure and optically stimulated luminescence dating are providing data to define the timing of glaciation and these together with objective analysis of glacier dynamics may allow better estimates of ela changes in the future however there are currently only two regions the hunza valley and the khumbu himal which are sufficiently well dated to allow reconstructions of last glacial maximum glacier extent and hence elas these two regions cannot provide an adequate assessment of ela changes for the himalayan tibetan region

perspectives on the production of a glacier inventory from multispectral satellite data in arctic canada cumberland peninsula baffin island the consequences of global warming on land ice masses are difficult to assess in detail as two dimensional glacier inventory data are still missing for many remote regions of the world as the largest future temperature increase is expected to occur at high latitudes the glaciers and ice caps in the arctic will be particularly susceptible to the expected warming this study demonstrates the possibilities of space borne glacier inventorying at a remote site on cumberland peninsula a part of baffin island in arctic canada thereby providing glacier inventory data for this region our approach combines landsat etm and terra aster satellite data an aster derived digital elevation model dem and geographic information system based processing we used thresholded ratio images from etm bands 3 and 5 and aster bands 3 and 4 for glacier mapping manual delineation of little ice age trimlines and moraines has been applied to calculate area changes for 225 glaciers yielding an average area loss of 11 a size distribution has been obtained for 770 glaciers that is very different from that for alpine glaciers numerous three dimensional glacier parameters were derived from the aster dem for a subset of 340 glaciers the amount of working time required for the processing has been tracked and resulted in 5 min per glacier or 7 years for all estimated 160 000 glaciers worldwide

spatially variable response of himalayan glaciers to climate change affected by debris cover the present state and future evolution of himalayan glaciers has been controversial an analysis of remotely sensed frontal changes and surface velocities from glaciers in the greater himalaya between 2000 and 2008 shows large regional variability in the responses of himalayan glaciers to climate change

observed interannual variability of zonal currents in the equatorial indian ocean thermocline and their relation to indian ocean dipole interannual variability of zonal currents in the eastern equatorial indian ocean thermocline is significantly correlated with sea surface temperature sst in the eastern pole of the indian ocean dipole iod this relationship is more significant than for zonal currents and the dipole mode index the latter of which measures zonal sst anomaly gradient the variability of zonal currents in the thermocline is consistent with the variations of eastward pressure gradient force in the thermocline and the equatorward geostrophic thermocline flows associated with the shallow meridional overturning circulations in the eastern tropical indian ocean our analysis suggests a positive feedback between zonal currents in the thermocline and sst in the eastern pole of iod the combination of equatorial wind and off equatorial wind stress curls associated with sst anomalies in the eastern pole of the iod drives interannual variability in equatorial zonal thermocline flows and its covariability with the shallow meridional overturning cells

impacts of the iod associated temperature and salinity anomalies on the intermittent equatorial undercurrent anomalies the study of equatorial undercurrent euc has attracted a broad attention in recent years due to its strong response and feedback to the indian ocean dipole in this paper we first produce a high quality simulation of three dimensional temperature salinity and zonal current simulation from 1982 to 2014 using a high resolution ocean general circulation model on this basis with two sensitivity experiments we investigate the role of temperature and salinity anomalies in driving and enhancing the euc during the positive iod events by examining the variation of the euc seasonal cycle and diagnosing the zonal momentum budget along the equatorial indian ocean our results show that during january march the euc can appear along the entire equatorial indian ocean in all years but during august november the euc can appear and reach the eastern indian ocean only during the positive iod events the zonal momentum budget analysis indicates that the pressure gradient force contributes most to the variation of the eastward acceleration of zonal currents in the subsurface during the positive iod events strong negative subsurface temperature anomalies exist in the eastern indian ocean with negative surface salinity anomalies in the central and eastern indian ocean resulting in a large pressure gradient force to drive euc during the august november further the results of two sensitivity experiments indicate that the temperature anomalies significantly impact the pressure gradient force playing a leading role in driving the euc while the surface salinity anomalies can secondarily help to intensify the eastward euc through increasing the zonal density gradient in the eastern indian ocean and impacting the vertical momentum advection in the subsurface

sea surface salinity variability during the indian ocean dipole and enso events in the tropical indian ocean an ocean reanalysis that covers the period from 1871 2008 is used to analyze interannual variability of sea surface salinity sss in the tropical indian ocean the reanalysis sss and the sss anomaly patterns during indian ocean dipole iod and el nino southern oscillation enso events are compared with patterns from argo sss data the mean seasonal sss variation is large in the northern bay of bengal compared to variations in the arabian sea and equatorial indian ocean during a positive iod event positive sss anomalies are found along the sumatra coast due to the combination of wind driven upwelling of subsurface high salinity waters enhanced evaporation and anomalous surface circulation the opposite is true to a lesser extent during negative iod events a dipole mode index for salinity dmis based on sss data and a new index based on the average of salinity in a region off the coast of sumatra is introduced to monitor sss variability during iod and enso events the impact of concomitant el nino events on a positive iod event is large with freshening a negative sss anomaly in the equatorial indian ocean and salting positive sss anomaly off the southern sumatra coast the impact of intense freshening reaches into the southwestern tropical indian ocean the impact of concomitant la nina with negative iod is also large with an intense freshening in the southeastern arabian sea and salting off the northern sumatra coast

the pattern and variability of winter kuroshio intrusion northeast of taiwan the variations of the kuroshio path and velocity northeast of taiwan are analyzed based on along track satellite altimeter data as well as high resolution model experiments observations reveal that in winter the kuroshio intrusion into the east china sea ecs at this location is manifested by a secondary maximum current core smcc shoreward of the kuroshio s main path the smcc varies significantly on interannual time scale and its variability is strikingly out of phase with that of the kuroshio entering the ecs meaning that the stronger the kuroshio the weaker the smcc and vice versa model experiments corroborate the observational results and more importantly indicate that the kuroshio intrusion here follows two primary routes a large anticyclonic loop that separates from the kuroshio at the northern end of taiwan and moves forward to form the smcc and a straight northward path onto the shelf when the kuroshio turns sharply eastward along the continental slope of the ecs the intrusion is controlled by both local forcing and remote effect with its pattern and variability depending mostly on the local heat flux and the inertia of the kuroshio current

detection of dual effects of degradation of perennial snow and ice covers on the hydrologic regime of a himalayan river basin by stream water availability modeling summary in river basins where melt water from snow and ice constitutes a dominant component of stream discharge during summer degradation or reduction of perennial snow and ice covered areas sca p has a profound effect on stream water availability in those basins degradation of sca p that includes glaciers is a globally widespread phenomenon observed in the recently past decades its cause has been attributed to global warming and its consequence is expected to dramatically alter the flow regimes of the rivers draining the terrains the predicted change in flow regime is an initial increase in summer flows in the early decades of 21st century followed by sharp decline of the same during the later parts of the century estimation of sca p within the upper indus basin uib straddling the western ranges of the greater himalayas karakoram mountains and the eastern mountain ranges of the hindu kush shows that from 1992 to 2010 there has been about 2 15 reduction in sca p a spatially distributed basin scale stream water availability model is presented to calculate monthly river discharges at critical hydrologic junctions within uib model calculations for the years 1992 2000 and 2008 show that due to the degradation of the sca p within the basin there has been significant decrease in summer discharges at various hydrologic junctions the percentage decline in flows varies from 10 to 22 depending on the locations of the junctions within the basin the space dependence of these variations reflects differential degradation of sca p in various parts of the basin furthermore the time of peak discharge at all of the hydrological junctions has shifted from middle late summer to late spring early summer as another outcome of sca p reduction such temporal shifting of nival regimes to early part of warmer season has also been predicted by global warming models however the case study presented here for a major himalayan river basin demonstrates that such shifting of peak discharge in the time domain can also take place simply due to retreat of the equilibrium line thus the effects of a warming climate have possibly been already set within uib instead of experiencing an increased pulse of summer flows for the next few decades summer flows within this basin are expected to decline changes in the timing of peak flows can have adverse effects on multipurpose water resources management without appropriate adaptation and mitigation measures monthly average stream flow data with 35 year period of record from a key gauging station support the findings of the model results similarly digital maps of sca p at different time periods within a key catchment of uib containing one of the major glaciers show retreat of glacial lobes and significant decrease in total sca p taking place during the past decades

mass balance of himalayan glaciers using aar and ela methods the accumulation area ratio aar for himalayan glaciers representing zero mass balance is substantially lower than for north america and europe regression analysis suggests 0 44 for the aar representing zero mass balance in the western himalaya a good correlation was observed when this method was applied to individual glaciers such as gara and gor garang in himachal pradesh india the correlation coefficients r using 6 and 7 years of data respectively were 0 88 and 0 96 for gara and gor garang glaciers respectively however when data from six western himalayan glaciers were correlated the correlation was 0 74 the aar was also estimated by using landsat images which can be useful in obtaining a trend in mass balance for a large number of himalayan glaciers for which very little information exists a higher correlation was observed between equilibrium line altitude ela and mass balance the field data from gara and gor garang glaciers shows a high correlation coefficient i e 0 92 and 0 94 respectively the ela values obtained from the landsat satellite images combined with topographic maps suggest positive mass balance for the year 1986 87 and negative for 1987 88

spatial patterns and variation of suspended sediment yield in the upper indus river basin northern pakistan summary much of the flow of the indus originates in the mountainous regions of the karakoram and himalayas resulting in a high sediment yield that creates a number of operational and maintenance problems for downstream water use in pakistan analysis of the available hydro climatological data indicates that the upper indus basin can be subdivided into three characteristic regions based on whether runoff production is controlled by temperature region 1 upper glacierized sub basins precipitation caused by the monsoon and western disturbances region 3 lower sub basins or a combination of the two region 2 middle reach sub basins the runoff and sediment transport regimes for the shyok gilgit hunza and indus rivers in region 1 show the role of snow and ice melt in generating high runoff and 80 85 of the annual sediment load is transported in july and august the astore river at doyian in region 2 shows an early rise of the sediment yield starting in may due to the interaction of rainfall and snowmelt at lower elevations and a comparatively lower sediment yield in august indicating a lesser influence of glacier melt region 3 experiences two types of rainfall summer monsoons and the western disturbances in late winter and early spring consequently the gorband river at karora in region 3 exhibits two separate sediment yield peaks of equal height in april and july the runoff and sediment transport regime along the main stem of the indus river is dominated by the melt of snow and ice in its headwaters and consequently is similar to the regimes of the region 1 sub basins contrary to the conventional model the specific sediment yield increases markedly with drainage area along the indus river from 355 t km 2 yr 1 at kharmong to 1197 t km 2 yr 1 at besham qila likely because of the large number of small and relatively steep catchments discharging straight into the indus river analysis of the magnitude frequency characteristics of sediment transport for the tributaries shows that the effective discharge in the basin ranges from 1 5 2 0 to 5 5 6 0 times the average discharge and decreases downstream the main indus river however shows a consistent effective discharge of 2 5 3 0 times the average discharge

early twenty first century glacier mass losses in the indus basin constrained by density assumptions abstract glaciers in the upper indus supply more than half of the river water are experiencing significant melting with a debated fate the recent melting rate is still contained by considerable uncertainties hindering to estimate precise glacier mass change here we present geodetic mass balance results for the whole indus basin using srtm and alos 30 m elevation data improved glacier inventory optimized glacier surface density and validation through in situ differential gps and icesat data our glacier inventory and derived by improving rgi6 0 boundaries and separated into debris cover and debris free parts the derived surface elevation changes were converted into annual mass balances using separated density assumptions four criteria for debris covered ice 900 60 kg m 3 debris free ice below 20 and 25 slopes 850 60 kg m 3 and above 20 and 25 slopes 600 60 kg m 3 respectively the resulting mass balance biased between 0 20 and 0 09 m water equivalent w e a 1 using an average 850 60 kg m 3 density assumption throughout the indus basin in the western himalaya and hindu kush the glacier mass losses are less affected by the average density assumption compared to the karakoram the western hunza and central shigar karakoram glaciers show negligible mass losses of 0 02 0 12 and 0 01 0 13 m w e a 1 in contrast to the relatively more negative mass balance 0 26 0 21 m w e a 1 in the eastern shyok karakoram all the sub basins exhibit negative mass balances with the most negative values ranging from 0 34 0 31 to 0 44 0 27 m w e a 1 in the ravi chenab and jhelum sub basins of the himalaya the whole indus basin contributes approximately 0 014 0 016 mm a 1 to the global mean sea level equivalent

can the snowline be used as an indicator of the equilibrium line and mass balance for glaciers in the outer tropics because the glacier snowline is easy to identify on optical satellite images and because in certain conditions it can be used as an indicator of the equilibrium line it may be a relevant parameter for the study of the relationships between climate and glaciers although several studies have shown that the snowline altitude sla at the end of the hydrological year is a good indicator of the equilibrium line altitude ela for mid latitude glaciers such a relationship remains conjectural for tropical glaciers indeed unlike in mid latitudes tropical climate conditions result in a distinct seasonality of accumulation ablation processes we examine this relationship using direct field ela and mass balance measurements made on glaciar zongo bolivia 168 s and glaciar artesonraju peru 98 s and the sla retrieved from satellite images acquired in the past two decades we show that on glaciers in the outer tropics 1 ablation is reduced during the dry season in austral winter may august the sla does not change much and satellite images acquired between may and august could be used to compute the sla and 2 the highest sla detected on a number of satellite images acquired during the dry season provides a good estimate of the annual ela however as snowfall events can occur during the dry season the sla detected on satellite images tends to underestimate the ela thus we recommend validating the sla computed from satellite images with field data collected on a benchmark glacier before measuring the sla on other glaciers in the same mountain range for which no field data are available this study is a major step towards extending the measurement of glacier parameters ela and mass balance at the scale of a whole mountain range in the outer tropics to better document the relationships between climate and glaciers

volume transports of the wyrtki jets and their relationship to the indian ocean dipole the equatorial indian ocean is characterized by strong eastward flows in the upper 80 100 m during boreal spring and fall referred to as the wyrtki jets these jets are driven by westerly winds during the transition seasons between the southwest and northeast monsoons and represent a major conduit for mass and heat transfer between the eastern and western sides of the basin since their discovery over 40 years ago there have been very few estimates from direct observations of the volume transports associated with these currents in this paper we describe seasonal to interannual time scale variations in volume transports based on 5 years of unique measurements from an array of acoustic doppler current profilers in the central equatorial indian ocean the array was centered at 0 80 5 e and spanned latitudes between 2 5 n and 4 s from august 2008 to december 2013 analysis of these data indicates that the spring jet peaks in may at 14 9 2 9 sv and the fall jet peaks in november at 19 7 2 4 sv around which there are year to year transport variations of 5 10 sv the relationship of the interannual transport variations to zonal wind stress forcing sea surface temperature sea surface height and surface current variations associated with the indian ocean dipole iod are further highlighted we also illustrate the role of wind forced equatorial waves in affecting transport variations of the fall wyrtki jet during the peak season of the iod

quasi biweekly impact of the atmospheric heat source over the tibetan plateau on summer rainfall in eastern china we investigated the intraseasonal relationship between the atmospheric heat source over tibetan plateau tp and summer rainfall in eastern china a quasi biweekly oscillation qbwo is the common dominant periodicity over both the tp and eastern china crucially the tp heat source qbwo leads rainfall qbwo over its downstream region by 2 8 days the qbwo over the tp shows a significant eastward propagation phase composite further identified the specific propagation pathway tp qbwo first propagates eastward to central china southward to southern china and then northeastward to the lower reaches of the yangtze river with a zigzag propagating pathway mechanistically the eastward propagation of the upper level divergence caused by the movement of the 200 hpa jet core and south asian high contributes to the eastward propagation of the rainfall qbwo simultaneously the eastward westward shift in the western north pacific subtropical high causes deepening flattening of the monsoon trough and the occurrence of an anomalous cyclone anticyclone over the western north pacific an anomalous anticyclonic cyclonic circulation around the tp appears with the wet to dry dry to wet phase transition of the tp qbwo together they play a crucial part in the southward northeastward movement of the qbwo further dynamic analysis indicates that the horizontal moisture advection acts on the whole eastward propagating process of the qbwo whereas the horizontal vorticity advection is only significant when qbwo is over the tp this study shows that the fluctuations in tp heat source are important indicators in extended forecasts of summer rainfall in eastern china

separating snow clean and debris covered ice in the upper indus basin hindukush karakoram himalayas using landsat images between 1998 and 2002 summary the hindukush karakoram himalayan mountains contain some of the largest glaciers of the world and supply melt water from perennial snow and glaciers to the upper indus basin uib upstream of tarbela dam which constitutes greater than 80 of the annual flows and caters to the needs of millions of people in the indus basin it is therefore important to study the response of perennial snow and glaciers in the uib under changing climatic conditions using improved hydrological modeling glacier mass balance and observations of glacier responses however the available glacier inventories and datasets only provide total perennial snow and glacier cover areas despite the fact that snow clean ice and debris covered ice have different melt rates and densities this distinction is vital for improved hydrological modeling and mass balance studies this study therefore presents a separated perennial snow and glacier inventory perennial snow cover on steep slopes perennial snow covered ice clean and debris covered ice based on a semi automated method that combines landsat images and surface slope information in a supervised maximum likelihood classification to map distinct glacier zones followed by manual post processing the accuracy of the presented inventory falls well within the accuracy limits of available snow and glacier inventory products for the entire uib estimates of perennial and or seasonal snow on steep slopes snow covered ice clean and debris covered ice zones are 7238 724 5226 522 4695 469 and 2126 212 km2 respectively thus total snow and glacier cover is 19 285 1928 km2 out of which 12 075 1207 km2 is glacier cover excluding steep slope snow cover equilibrium line altitude ela estimates based on the snow line elevation sle in various watersheds range between 4800 and 5500 m while the accumulation area ratio aar ranges between 7 and 80 0 c isotherms during peak ablation months july and august range between 5500 and 6200 m in various watersheds these outputs can be used as input to hydrological models to estimate spatially variable degree day factors for hydrological modeling to separate glacier and snow melt contributions in river flows and to study glacier mass balance and glacier responses to changing climate

mechanisms of an extraordinary east asian summer monsoon event in july 2011 previous studies have demonstrated that the strong east asian summer monsoon results mainly from the westward intensification of the north pacific subtropical high npsh or equivalently the enhancement of the western north pacific subtropical high however during early july in 2011 a strong southerly or southeasterly moist flow gave rise to a large amount of precipitation over southwestern japan and korea and anomalous dry conditions over central china because of the extraordinary intensification of the npsh to the north the formation of the anomalous high that occurred to the east of central japan during early july is very rare and its physical mechanisms are investigated in this study the regressed circulation anomalies and wave activity flux vectors for july 2011 and data from the previous 32 years show that two teleconnection patterns due to rossby wave trains are the most important mechanisms rossby wave propagation from the eastern north atlantic and western europe to east asia following the north eurasian jet and east asian jet in the upper level and northward propagation of rossby waves forced by diabatic heating over the western north pacific wnp region in the lower level this simultaneous forcing of a significant negative phase of the summertime north atlantic oscillation in the higher latitudes and enhanced diabatic heating over the subtropical wnp is found to be the cause of the abnormal development of the anomalous high to the east of central japan resulting in extremely wet conditions in korea and southern japan and dry conditions in southern china

rising river flows throughout the twenty first century in two himalayan glacierized watersheds greater himalayan glaciers are retreating and losing mass a combination of the latest ensemble of climate models combined with a glacio hydrological model suggests that in two contrasting watersheds in the greater himalaya glaciers will recede but net glacier melt runoff is on a rising limb until at least 2050

anomalous surface currents in the tropical indian ocean an anomalous climate event occurred in 1997 in the indian ocean with severe consequences for the surrounding continental areas in response to an intensification of the trade winds a westward gradient of sst and an anomalous reversal of the eastward surface currents with peak velocity anomalies exceeding 1 m s were evident in boreal autumn a similar but weaker event took place in 1994 in this study we examine the observational record during the 1990s including surface drifter velocities sst and altimeter sea level to confirm these dramatic changes we examine the key momentum balance between wind induced momentum flux and the pressure gradient force as well as the important role of horizontal temperature advection in the mixed layer heat response

the formation mechanism of the bonin high in august the bonin high is a subtropical anticyclone that is predominant near japan in the summer this anticyclone is associated with an equivalent barotropic structure often extending throughout the entire troposphere although the equivalent barotropic structure of the bonin high has been known for years among synopticians because of its importance to the summer climate in east asia there are few dynamical explanations for such a structure the present paper attempts to provide a formation mechanism for the deep ridge near japan we propose a new hypothesis that this equivalent barotropic ridge near japan is formed as a result of the propagation of stationary rossby waves along the asian jet in the upper troposphere the silk road pattern first the monthly mean climatology is examined in order to demonstrate this hypothesis it is shown that the enhanced asian jet in august is favourable for the propagation of stationary rossby waves and that the regions of descent over the eastern mediterranean sea and the aral sea act as two major wave sources second a primitive equation model is used to simulate the climatology of august the model successfully simulates the bonin high with an equivalent barotropic structure the upper tropospheric ridge is found to be enhanced by a height anomaly of more than 80 m at 200 hpa when a wave packet arrives sensitivity experiments are conducted to show that the removal of the diabatic cooling over the asian jet suppresses the silk road pattern and formation of an equivalent barotropic ridge near japan while the removal of the diabatic heating in the western pacific does not copyright 2003 royal meteorological society

horizontal structure of 500 mb height fluctuations with long intermediate and short time scales abstract maps of standard deviations and one point correlation maps based on twice daily data subjected to a variety of temporal filters are presented in order to document the horizontal structure of 500 mb height fluctuations with different time scales the filters have been chosen to isolate fluctuations with long time scales periods much longer than 30 days intermediate time scales 10 30 day periods and short time scales 2 5 6 day periods the one point correlation maps for long time scales resemble the teleconnection patterns described by wallace and cutzler these patterns are strongly regionally dependent with meridionally oriented dipole structures in the jet exit regions over the oceans indicative of strong fluctuations in the zonal wind for intermediate time scales the dominant patterns consist of more zonally oriented wave trains which originate in the jet entrance regions and cross the jet streams as they curve southeastward into the tropics another important distinction between th

a more complete version of the world glacier inventory the world glacier inventory wgi was conceived half a century ago as an activity to be completed during the international geophysical year 1957 58 it consisted until very recently of nearly 70 000 glacier records covering slightly less than one quarter of the glacier ice outside the ice sheets a complete wgi must be a compromise if it is to be available and usable soon a more complete version called wgi xf is available and usable now and contains records for just over 131 000 glaciers and nearly half of the global extent of ice the additional glaciers come mainly from the assimilation of existing inventories but also from rescuing inventories that have been lost and from new inventories in canada and the subantarctic in wgi xf the xf stands for extended format flagging the fact that wgi xf conforms to a set of explicit specifications which enhance usefulness by eliminating low level inconsistencies two important features are nominal glaciers and glacier complexes a nominal glacier of which there are about 5000 in wgi xf is one about which little is known other than its existence and approximate location a glacier complex is one or more contiguous glaciers this term embodies the idea which is not new that inventories can be preliminary based upon vector outlines which await subdivision by trained glaciologists many regional studies have found that measurements of changes in single glaciers require accurate work and painstaking quality control wgi xf is not assuredly reliable as a source for such detailed work but there are several other subjects in which less detail would be a price worth paying for more complete coverage incomplete information about the dates of imagery and maps is a hindrance to analysis and the recovery of dates from metadata should have high priority

timing and extent of late quaternary glaciation in the western himalaya constrained by 10be moraine dating in garhwal india glacial chronologies from the himalayan region indicate various degrees of asynchronous glacial behavior part of this has been related to different sensitivities of glaciers situated in contrasting climatic compartments of the orogen but so far field data in support for this hypothesis is lacking here we present a new 10 be derived glacial chronology for the upper tons valley in western garhwal india and initial results for the pin and thangi valleys in eastern himachal pradesh these areas cover a steep gradient in orographic precipitation and allow testing for different climatic sensitivities our data provide a record of five glacial episodes at w16 ka w11 12 ka w8 9 ka w5 ka and 1 ka in the thangi valley our results indicate a glacial episode at w19 ka but no data are available for younger glacial deposits in this valley at their largest mapped extent w16 ka the two main glaciers in the upper tons valley joined and descended down to w2500 m asl which represents a drop of w1400 m compared to the present day glacial extent during the holocene the two largest glaciers produced distinct glacial landforms that allowed us to reconstruct changes in the equilibrium line altitude ela over w20 km north south distance that is presently associated with a steep gradient in rainfall we observe that ela changes have been consistently w2 times higher for the glacier located in a presently wetter climate pointing at different climate sensitivities related to the amount of precipitation that they receive at regional scale our data is in reasonable agreement with other published glacial chronologies from the western himalaya and suggest that glacial advances during the holocene have been largely synchronous in this region comparison of glacial chronologies from the western himalaya with other palaeoclimatic proxy data suggests that long term changes in glacial extents are controlled by glacial interglacial temperature oscillations related to the waxing and waning of the large northern hemisphere ice sheets while the timing of millennial scale advance and retreat cycles are more directly related to monsoon strength

ice ablation and meteorological conditions on the debris covered area of baltoro glacier karakoram pakistan during the recent italian expedition k2 2004 50 years later june july 2004 on baltoro glacier karakoram pakistan glaciological field experiments were carried out on the debris covered area of this high elevation glacier the aim was to investigate the ice ablation and its relations with debris thermal properties and meteorological conditions ablation measurements along the glacier up to about 5000 m and within a dedicated test field were combined with meteorological data from two automatic weather stations located at urdukas 4022 m a s l and at k2 base camp 5033 m a s l in addition temperature measurements of the debris cover at different depth levels along the glacier allowed the calculation of debris surface temperature and of the debris thermal resistance r using the air temperature the local mean lapse rate 0 00758 cm 1 and the measured ablation the degree day factors k at different locations on the glacier were calculated the ice ablation rates were related to debris thickness and elevation they are typically on the order of 4 cm d 1 during the observation period however it was found that the surface topography slope aspect has an influence on the total ablation similar to that of the debris thickness thermal resistance of the debris cover and its distribution over the glacier were estimated finally a best guess estimate of the total meltwater production was calculated from available climate data

25 years 1981 2005 of equilibrium line altitude and mass balance reconstruction on glacier blanc french alps using remote sensing methods and meteorological data annual equilibrium line altitude ela and surface mass balance of glacier blanc ecrins region french alps were reconstructed from a 25 year time series of satellite images 1981 2005 the remote sensing method used was based on identification of the snowline which is easy to discern on optical satellite images taken at the end of the ablation season in addition surface mass balances at the ela were reconstructed for the same period using meteorological data from three nearby weather stations a comparison of the two types of series reveals a correlation of r 0 67 at the 0 01 level of significance furthermore the surface mass balances obtained from remote sensing data are consistent with those obtained from field measurements on five other french glaciers r 0 76 p 0 01 also consistent for glacier blanc is the total mass loss 10 8mw e over the studied period however the surface mass balances obtained with the remote sensing method show lower interannual variability given that the remote sensing method is based on changes in the ela this difference probably results from the lower sensitivity of the surface mass balance to climate parameters at the ela

spatial distribution of debris thickness and melting from remote sensing and meteorological data at debris covered baltoro glacier karakoram pakistan a distributed surface energy balance study was performed to determine sub debris ablation across a large part of baltoro glacier a wide debris covered glacier in the karakoram range pakistan the study area is 124 km 2 the study aimed primarily at analyzing the influence of debris thickness on the melt distribution the spatial distribution of the physical and thermal characteristics of the debris was calculated from remote sensing aster image and field data meteorological data from an automatic weather station at urdukas 4022 m a s l located adjacent to baltoro glacier on a lateral moraine were used to calculate the spatial distribution of energy available for melting during the period 1 15 july 2004 the model performance was evaluated by comparisons with field measurements for the same period the model is reliable in predicting ablation over wide debris covered areas it underestimates melt rates over highly crevassed areas and water ponds with a high variability of the debris thickness distribution in the vicinity and over areas with very low debris thickness 0 03 m we also examined the spatial distribution of the energy balance components global radiation and surface temperature over the study area the results allow us to quantify for the study period a meltwater production of 0 058 km 3

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

active break cycles diagnosis of the intraseasonal variability of the asian summer monsoon in this study various diagnostics have been applied to daily observed outgoing longwave radiation olr and ecmwf reanalysis era products to provide a comprehensive description of the active break cycles associated with the asian summer monsoon and to address the differing behaviour of the two dominant time scales of intraseasonal variability 10 20 days and 30 60 days composite analysis of olr based on filtered daily all india rainfall air for the 40 day 30 60 days intraseasonal mode indicates that during active phases convection is significantly enhanced over the indian continent extending over the bay of bengal maritime continent and equatorial west pacific while convection is suppressed over the equatorial indian ocean and northwest tropical pacific resulting in a quadrapole structure over the asian monsoon domain in response to this heating pattern the large scale hadley lateral and the two east west transverse tropical circulations are enhanced there is also a significant impact on the extra tropical circulation through excitation and propagation of rossby waves in contrast the 15 day mode is more regional to the monsoon domain and has a prominent east west orientation in convection only the local hadley circulation over the monsoon region is modulated by this mode the evolution of these two modes as revealed by pop principal oscillation pattern analysis shows that the 40 day mode originates over the equatorial indian ocean once formed it has poleward propagation on either side of the equator and eastward propagation into the equatorial west pacific from the equatorial west pacific northward propagation over the west pacific and westward propagation into the indian longitudes are prominent the propagative features are complex and interactive and are responsible for the quadrapole structure in convection seen from the composites the interannual variability assessed from the pop coefficient time series indicates that the 40 day mode is strong during the onset phase of the monsoon in all the years but systematic propagation over the entire season depends crucially on the activity of the oceanic tcz tropical convergence zone the pop analysis of the 15 day mode indicates that this event originates over the equatorial west pacific associated with westward propagating rossby waves amplifies over the northwest tropical pacific and modulates both the continental and oceanic tczs over indian longitudes simultaneously this mode is pronounced during the established phase of the monsoon due to the complexity in the propagational features of both the intraseasonal modes it is concluded that understanding the subseasonal variability of one regional component of the asian summer monsoon asm requires understanding the entire asm system

scale dependent analysis of satellite imagery for characterization of glacier surfaces in the karakoram himalaya abstract information regarding process structure relationships and change in the karakoram himalaya is of great importance in studying glacier hydrollogy mass balance and dynamic environmental change such information is not readily available detailed spatio temporal assessment requires field investigation coupled with quantitative remote sensing studies we conducted an investigation of the large batura glacier in pakistan to determine if spectral variability can be quantified and used to characterize glacier surfaces specifically spot panchromatic satellite data were evaluated for differentiating features of glacier structure resulting from ice movement ablation and supraglacial fluvial action image semivariogram analysis was conducted for assessing spectral variability patterns and fractal analysis was used to examine scale dependent variation in the data results indicate that spectral variability from fields of ice seracs can exhibit fractal characteristics although most surface features on the glacier exhibit a change in the fractal dimension over different ranges in scale the fractal dimension was found to be useful for differentiating between glacier surfaces such as white ice and debris covered ice characteristics of the debris load and the scale dependent nature of calculating the fractal dimension ultimately determined the potential of class separability

a precipitation seesaw mode between northeast asia and siberia in summer caused by rossby waves over the eurasian continent abstract there is a dominant seesaw pattern in summertime precipitation between northeast asia and siberia examined here is a mechanism of the seesaw mode focusing on quasi stationary rossby waves propagating on two upper tropospheric waveguides along the asian jet and over northern eurasia empirical orthogonal function eof analysis to the low frequency 10 day low pass filtered variation during summer reveals wave propagation patterns on both of the waveguides the time evolution of the two composite fields constructed using the obtained eof modes for each phase of the seesaw mode was investigated by the wave activity flux in both composite fields eastward propagating rossby waves originating from the north atlantic european sector branch off around eastern europe onto the two waveguides which become out of phase toward the east because of the difference in longitudinal wavelengths along them this results in opposite phase anomalies of meridional winds over northeast asia and siberia budget

the intraseasonal oscillation of eastern tibetan plateau precipitation in response to the summer eurasian wave train abstractthis study examines the characteristics and mechanisms associated with the dominant intraseasonal oscillation iso that controlled eastern tibetan plateau summer rainfall etpsr over the period 1979 2011 the results of both power and wavelet spectrum analysis reveal that etpsr follows a significant 7 20 day oscillation during most summers the vertical structure of the etpsr iso in the dry phase is characterized by a vertical dipole pattern of geopotential height with a positive center on the eastern tibetan plateau tp and a negative center on the western tp the wet phase shows the opposite characteristics to the dry phase the transitions between the dry and wet phases during an etpsr iso cycle are related to a rossby wave train that presents as large anomalous anticyclonic and cyclonic centers that alternate along the pathway from the eastern atlantic to southern china via the tp it corresponds to the evolution of the phase independent wave activity w which implies an eastward southeastw

intraseasonal variability of the south china sea summer monsoon the objective of this study is to explore based on the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis data the intraseasonal variability of the south china sea scs summer monsoon sm in terms of its structure and propagation as well as interannual variations a possible mechanism that is responsible for the origin of the 10 20 day oscillation of the scs sm is also proposed the 30 60 day hereafter the 3 6 mode and 10 20 day hereafter the 1 2 mode oscillations are found to be the two intraseasonal modes that control the behavior of the scssm activities for most of the years both the 3 6 and 1 2 modes are distinct but may not always exist simultaneously in a particular year and their contributions to the overall variations differ among different years thus the interannual variability in the intraseasonal oscillation activity of the scs sm may be categorized as follows the 3 6 category in which the 3 6 mode is more significant in terms of the percentage of variance explained than the 1 2 mode the 1 2 category in which the 1 2 mode is dominant and the dual category in which both the 3 6 and 1 2 modes are pronounced composite analyses of the 3 6 category cases indicate that the 30 60 day oscillation of the scs sm exhibits a trough ridge seesaw in which the monsoon trough and subtropical ridge exist alternatively over the scs with anomalous cyclones anticyclones along with enhanced suppressed convection migrating northward from the equator to the midlatitudes the northward migrating 3 6 mode monsoon trough ridge in the lower troposphere is coupled with the eastward propagating 3 6 mode divergence convergence in the upper troposphere it is also found that for the years in the dual category the scs sm activities are basically controlled by the 3 6 mode but modified by the 1 2 mode composite results of the 1 2 mode category cases show that the 10 20 day oscillation is manifest as an anticyclone cyclone system over the western tropical pacific propagating northwestward into the scs a close coupling also exists between the upper level convergence divergence and the low level anticyclone cyclone it is found that the 1 2 mode of the scs sm mainly originates from the equatorial central pacific although a disturbance from the northeast of the scs also contributes to this mode the flow patterns from an inactive to an active period resemble those associated with a mixed rossby gravity wave observed in previous studies

using remote sensing data to determine equilibrium line altitude and mass balance time series validation on three french glaciers 1994 2002 alpine glaciers are very sensitive to climate fluctuations and their mass balance can be used as an indicator of regional scale climate change here we present a method to calculate glacier mass balance using remote sensing data snowline measurements from remotely sensed images recorded at the end of the hydrological year provide an effective proxy of the equilibrium line mass balance can be deduced from the equilibrium line altitude ela variations three well documented glaciers in the french alps where the mass balance is measured at ground level with a stake network were selected to assess the accuracy of the method over the 1994 2002 period eight mass balance cycles results obtained by ground measurements and remote sensing are compared and show excellent correlation r 2 0 89 both for the ela and for the mass balance indicating that the remote sensing method can be applied to glaciers where no ground data exist on the scale of a mountain range or a given climatic area the main differences can be attributed to discrepancies between the dates of image acquisition and field measurements cloud cover and recent snowfalls constitute the main restrictions of the image based method

barotropic wave propagation and instability and atmospheric teleconnection patterns abstract a global barotropic model linearized about the 300 mb climatological mean january flow is perturbed by applying a series of localized forcings distributed throughout the tropics and subtropics structures which resemble the observed pacific north american and east atlantic teleconnection patterns noted by wallace and gutzler 1981 tend to recur in the responses similar patterns are found to result from the dispersion of isolated initial perturbations placed at a variety of locations in the tropics and midlatitudes it is shown that these structures are related to the most rapidly growing mode associated with barotropic instability of the zonally varying climatological basic state in the absence of damping this mode has an e folding time of about a week and a period close to 50 days in localized regions the instantaneous growth rates can be competitive with those of baroclinic instability these episodes of rapid local barotropic growth are interspersed with intervals in which the local

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

the effects of midlatitude waves over and around the tibetan plateau on submonthly variability of the east asian summer monsoon abstract convective variability at submonthly time scales 7 25 days over the yangtze and huaihe river basins yhrbs and associated large scale atmospheric circulation during the mei yu season were examined using interpolated outgoing longwave radiation olr and ncep ncar reanalysis data for 12 yr having active submonthly convective fluctuation over the yhrbs within the period 1979 2004 correlations between convection anomalies over the yhrbs and upper level streamfunction anomalies at every grid point show two contrasting patterns one pattern exhibits high correlations along the northern to eastern peripheries of the tibetan plateau defined as the net pattern whereas the other has high correlations across the tibetan plateau defined as the at pattern composite analysis of the net pattern shows slow southward migration of convection anomalies from the northeastern periphery of the tibetan plateau to southern china in relation to southward migration of the mei yu front caused by simultaneous am

structures and mechanisms of the northward propagating boreal summer intraseasonal oscillation abstract the spatial and temporal structures of the northward propagating boreal summer intraseasonal oscillation bsiso are revealed based on the analysis of both the echam4 model simulation and the ncep ncar reanalysis the bsiso structure and evolution characteristics simulated by the model bear many similarities to those derived from the ncep ncar reanalysis the most notable features are the remarkable meridional asymmetries relative to the bsiso convection in the vorticity and specific humidity fields a positive vorticity perturbation with an equivalent barotropic structure appears a few latitude degrees north of the convection center the maximum specific humidity also shows a clear northward shift in the lower troposphere two internal atmospheric dynamics mechanisms are proposed to understand the cause of the northward propagation of the bsiso the first is the vertical shear mechanism the key process associated with this mechanism is the generation of barotropic vorticity due to the couplin

chronology and climatic implications of late quaternary glaciations in the goriganga valley central himalaya india abstract goriganga valley which is located in the transition zone between the dry steppe of the tibetan plateau in the north and the sub humid himalayan climate in the south has preserved four events of glaciation with decreasing magnitude the oldest stage i glaciation is represented by a 12 5 km long discontinuous diamictite ridge which terminates north of rilkot 3100 m asl the stage ii glaciation is represented by sub rounded and partially eroded lateral moraines and terminates around martoli village 3240 m asl the stage iii and iv glacial moraines are sharp crested unstable and terminate proximal to the present day glacier at 3640 m asl and 3740 m asl respectively the stage ii moraines have been optically dated between 25 2 ka and 22 1 ka implying that glacier expanded during the global last glacial maximum lgm this is contrary to the suggestion that during last glacial maximum lgm glaciation was limited in extent due to weak indian summer monsoon ism in the monsoon dominated regions of the himalaya we ascribe the lgm glaciations to a combination of the lowered temperature and enhanced mid latitude westerlies following the lgm glaciation goriganga valley experienced two major pulses of deglaciation the older event is dated between 16 and 12 ka and is coeval with the initiation of the ism whereas the younger events 10 8 ka represent the early to mid holocene strengthened ism the stage iii and iv glaciations which terminated proximal to the modern glacier are speculated to occur during the mid holocene and little ice age lia respectively

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

former plateau ice fields in the godeanu mountains southern carpathians first evidence of glaciated peneplains in the carpathians abstract the existence of plateau ice fields in the southern carpathians has long been suggested due to the widespread presence of the bor scu surface in the region the bor scu surface is a peneplain consisting of flat plateaus in the elevation range of 1800 2200 m a s l it is present throughout the southern carpathians with the most typical appearance in the godeanu mountains these plateaus could have served as ice accumulation sites during the pleistocene glaciations as they were well above the steady state equilibrium line altitude ela 0 direct geomorphological evidence on the existence of plateau ice fields and thus well founded reconstructions are absent due to the lack of glacial landforms on the plateaus in order to test the existence of plateau ice fields a previous geomorphological survey and theoretical ice surface profiles based on a steady state perfectly plastic ice flow model were used based on these methods maps and three dimensional surface models of the former glaciers were created the ela 0 s of the paleoglaciers were estimated by the accumulation area ratio aar method according to our results three major ice fields on the central plateaus and several smaller ice fields on wide saddles were present in the godeanu mountains during the maximal glaciation the ice fields fed numerous surrounding valley glaciers several independent valley and cirque glaciers completely separated from the ice fields were also present further from the central mass of the mountain range the average ela 0 of the northern 1855 2 m a s l and the southern 1700 2 m a s l glaciers differed greatly we suggest that the surprisingly high average ela 0 of the northern glaciers was mostly caused by the missing lower sections of these paleoglaciers from our reconstructions due to the destroyed terminal glacial landforms however the terminal glacial landforms are quite well preserved in the southern valleys thus the average ela 0 of the southern paleoglaciers was suitable to correlate the maximal glaciation of the godeanu mountains with the maximal glaciation of the neighbouring retezat mountains

reconstruction of equilibrium line altitudes for tropical and sub tropical glaciers past fluctuations of tropical and sub tropical glaciers provide important palaeoclimate proxies for regions where other forms of evidence are rare however published equilibrium line altitude ela estimates for tropical and sub tropical glaciers at the lgm vary widely reflecting the diversity of methods and approaches employed by different research groups this complicates regional and global comparisons of ela estimates and emphasises the need for standardised methods the distinctive character of tropical and sub tropical glaciers however means that standard methods for reconstructing former glacier limits elas and palaeoclimate need to be adapted for local conditions many methods of ela reconstruction explicitly or implicitly make assumptions about glacier mass balance gradients and care needs to be taken that the choice of accumulation area ratios aars balance ratios brs and terminus to head ratios thars is appropriate as such indices are influenced by climatic regime debris cover and other factors ela reconstructions should employ multiple methods and should be cross checked and fully reported to allow assessment of the accuracy of ela estimates reliable glacier chronologies are equally important dating should be based on multiple radiometric techniques wherever possible and method of dating the type of material dated and the context of the date must all be reported

tributary glacier surges an exceptional concentration at panmah glacier karakoram himalaya four tributaries of panmah glacier have surged in less than a decade three in quick succession between 2001 and 2005 since 1985 13 surges have been recorded in the karakoram himalaya more than in any comparable period since the 1850s ten were tributary surges in these ten a full run out of surge ice is prevented but extended post surge episodes affect the tributary and main glacier the sudden concentration of events at panmah glacier is without precedent and at odds with known surge intervals for the glaciers interpretations must consider the response of thermally complex glaciers at exceptionally high altitudes and of high relief to changes in a distinctive regional climate it is suggested that high altitude warming affecting snow and glacier thermal regimes or bringing intense short term melting episodes may be more significant than mass balance change

assessing linkages between spatial facies changes and dimensional variations of glaciers in the upper indus basin western himalaya abstract the present study provides an insight into the heterogeneous response of 45 glaciers in the lidder and sindh river basins western himalaya and explores the linkages between glacier facies variability and changing glacier parameters results show that the region has undergone an overall deglaciation of 12 1 5 11 9 1 4 km 2 from 1996 to 2014 fluctuations in the temperature and precipitation patterns seem to be the primary factor controlling the changes in glacier dimensions r 2 0 82 in all cases glacier facies changes suggest depletion in snow ice cover 18 2 3 and an increase in ice mixed debris 4 1 4 supraglacial debris 6 1 5 and periglacial debris 17 1 2 these glacier facies transitions are possibly the result of ice melting however its relative rate and elevation decides the nature of facies conversion an increase in the proportion of supraglacial debris has led to the conversion of 11 clean glaciers to sparsely debris covered glaciers and 5 sparsely debris covered glaciers to debris covered glaciers the size of the glaciers greatly influenced the rate of conversion of glaciers and glaciers 2 dominated the others in this regard the small glaciers also experienced maximum shrinkage further the glaciers with varying supraglacial debris cover respond differently as sparsely debris covered glaciers exhibit the highest rates of retreat 25 7 3 m y followed by clean 23 7 7 3 m y and debris covered glaciers 13 1 7 3 m y thus the findings of this work clearly show that the climate change driven dimensional changes of glaciers and variations in the spatial distribution of glacier facies have strong mutual control on each other

anticorrelated intensity change of the quasi biweekly and 30 50 day oscillations over the south china sea 1 over the south china sea the year to year variations in the intensity of the quasi biweekly qbw and 30 50 day oscillations during june july are anti correlated an explanation is offered for the out of phase relationship we found during strong qbw years the june july mean convection and easterly vertical shear are enhanced over the equatorial western central pacific with corresponding low level cyclonic meridional shear to the northwest these conditions concurring with the equatorial eastern pacific warming are favorable for emanation of moist rossby waves from the equatorial western pacific on the other hand the 30 50 day becomes active when the mean convection is enhanced over the eastern indian ocean and maritime continent where this mode stems from and develops which often corresponds to cold western io one of these two large scale settings often occurs in the absence of the other so that when one mode is strong during june july the other mode tends to be weak

how large is the upper indus basin the pitfalls of auto delineation using dems summary extraction of watershed areas from digital elevation models dems is increasingly required in a variety of environmental analyses it is facilitated by the availability of dems based on remotely sensed data and by geographical information system gis software however accurate delineation depends on the quality of the dem and the methodology adopted this paper considers automated and supervised delineation in a case study of the upper indus basin uib pakistan for which published estimates of the basin area show significant disagreement ranging from 166 000 to 266 000 km 2 automated delineation used arcgis archydro and hydrology tools applied to three good quality dems two from srtm data with 90m resolution and one from 30m resolution aster data automatic delineation defined a basin area of c 440 000 km 2 for the uib but included a large area of internal drainage in the western tibetan plateau it is shown that discrepancies between different estimates reflect differences in the initial extent of the dem used for watershed delineation and the unchecked effect of iterative pit filling of the dem going beyond the filling of erroneous pixels to filling entire closed basins for the uib we have identified critical points where spurious addition of catchment area has arisen and use google earth to examine the geomorphology adjacent to these points and also examine the basin boundary data provided by the hydrosheds database we show that the pangong tso watershed and some other areas in the western tibetan plateau are not part of the uib but are areas of internal drainage our best estimate of the area of the upper indus basin at besham qila is 164 867 km 2 based on the srtm dem and 164 853 km 2 using the aster dem this matches the catchment area measured by wapda swhp an important lesson from this investigation is that one should not rely on automated delineation as iterative pit filling can produce spurious drainage networks and basins when there are areas of internal drainage nearby

combining satellite multispectral image data and a digital elevation model for mapping debris covered glaciers automated glacier mapping from satellite multispectral image data is hampered by debris cover on glacier surfaces supraglacial debris exhibits the same spectral properties as lateral and terminal moraines fluvioglacial deposits and bedrock outside the glacier margin and is thus not detectable by means of multispectral classification alone based on the observation of low slope angles for debris covered glacier tongues we developed a multisource method for mapping supraglacial debris the method combines the advantages of automated multispectral classification for clean glacier ice and vegetation with slope information derived from a digital elevation model dem neighbourhood analysis and change detection is applied for further improvement of the resulting glacier debris map a significant percentage of the processing can be done automatically in order to test the sensitivity of our method against different dem qualities it was also applied to a dem obtained from aster stereo data additionally we compared our multisource approach to an artificial neural network ann classification of debris using only multispectral data while the combination with an aster derived dem revealed promising results the ann classification without dem data does not

time variation of 500 mb height fluctuations with long intermediate and short time scales as deduced from lag correlation statistics abstract the time variation of northern hemisphere wintertime 500 mb height fluctuations with short intermediate and long time scales is investigated using lag correlation patterns derived from time filtered data fluctuations with short 2 5 6 day periods time scales propagate eastward at a rate consistent with the notion of a steering level around 700 mb which supports an interpretation in terms of baroclinic waves the mobile teleconnection patterns associated with the intermediate 10 30 day periods time scales exhibit a pattern of time variation suggestive a rossby wave dispersion with a predominance of southward dispersion from middle latitudes into the tropics the geographically fixed teleconnection patterns characteristic of the longer time scales do not show a well defined pattern of time variation but their horizontal structure resembles that of the fastest growing normal mode associated with barotropic instability of the climatological mean wintertime flow

impact of atmospheric intraseasonal variability in the indian ocean low frequency rectification in equatorial surface current and transport an ocean general circulation model ogcm is used to investigate the low frequency period longer than 90 days rectification of atmospheric intraseasonal variability 10 90 day periods in zonal surface current and transport of the equatorial indian ocean a hierarchy of ogcm solutions is found in an actual tropical indian ocean basin for the period of 1988 2001 to help to identify and isolate nonlinear processes a linear continuously stratified model and a 4 layer intermediate ocean model are also used results from the ogcm solutions suggest 1 2 that intraseasonal atmospheric forcing acts to weaken the equatorial seasonal surface currents amplitudes of the spring and autumn eastward surface jets the wyrtki jets wj and the westward surface current during january march are reduced by as much as 15 25 cm s21 by intraseasonal atmospheric forcing and strengths of the rectification exhibit a significant interannual variability important processes that cause the low frequency rectification are asymmetric response of mixed layer depth to easterly and westerly winds entrainment and upwelling of momentum during spring and autumn the westerly easterly phase of an intraseasonal event enhances weakens or even reverses the seasonal westerly winds increases decreases equatorial convergence and entrainment and thus deepens thins the mixed layer a net westward current is generated over an event mean because easterly wind acts on a thinner surface mixed layer whereas westerly wind acts on a thicker one in contrast during january march when the seasonal winds are equatorial easterlies surface currents are westward and equatorial undercurrents euc develop the rectified surface currents are eastward which reduces the westward surface flow this eastward rectification results largely from the vertical advection and entrainment of the euc the seasonal to interannual variability of the rectified surface flow is determined primarily from the seasonal cycle and interannual variability of the background state seasonal to interannual variability of the intraseasonal wind forcing also contributes the rectified low frequency zonal volume heat transports integrated over the entire water column along the indian ocean equator are persistently eastward with an amplitude of 0 15 3 106 m3 s 21 0 1 2 pw this is because westerly winds generate equatorial downwelling advecting the surface eastward momentum downward and giving an eastward subsurface current easterly winds cause equatorial upwelling and produce an eastward pressure gradient force that drives an eastward subsurface current this eastward subsurface current is advected upward by upwelling the mean effect over an intraseasonal event at the equator is to increase the eastward transport in the water column in the layers above the thermocline the rectified zonal volume heat transports are in the same direction as the rectified surface currents results from this paper may have important implications for understanding climate variability because modification of wj strength and transports can affect the sst and heat storage in the equatorial indian ocean warm pool

the new remote sensing derived swiss glacier inventory i methods a new swiss glacier inventory is to be compiled from satellite data for the year 2000 the study presented here describes two major tasks 1 an accuracy assessment of different methods for glacier classification with landsat thematic mapper tm data and a digital elevation model dem 2 the geographical information system gis based methods for automatic extraction of individual glaciers from classified satellite data and the computation of three dimensional glacier parameters such as minimum maximum and median elevation or slope and orientation by fusion with a dem first results obtained by these methods are presented in part ii of this paper kaab and others 2002 thresholding of a ratio image from tm4 and tm5 reveals the best suited glacier map the computation of glacier parameters in a gis environment is efficient and suitable for worldwide application the methods developed contribute to the u s geological survey led global land ice measurements from space glims project which is currently compiling a global inventory of land ice masses within the framework of global glacier monitoring haeberli and others 2000

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

rising river flows and glacial mass balance in central karakoram summary field observations and geodetic measurements suggest that in the central part of the karakoram mountains glaciers are either stable or expanding since 1990 in sharp contrast to glacier retreats that are prevalent in the himalayas and adjoining high altitude terrains of central asia decreased discharge in the rivers originating from karakoram is cited as a supporting evidence of this somewhat anomalous phenomenon here in contrary to those citations we show that river discharge during the melting season of the glaciers in central karakoram has increased from 1985 to 2010 we have implemented a sophisticated statistical procedure involving non parametric tests combined with a benchmark smoothing technique that has proven to be a powerful method for empirical trend analysis to remove the stochastic component from the trend component in a time series melt water from winter snows is the dominant constituent of june and july flows glacial melts predominantly contribute to august and partially to september flows which are controlled by monsoonal snowfall too at elevations approximately 3500 m for all four summer months flows increased from 1985 to 2000 august flows which actually reflect the states of the glaciers have continued to rise steadily after 2000 at the same rate as those did for the period 1985 2000 however the rising trends of june and july flows changed to slightly declining trends from 2000 to 2010 these trends most likely indicate drop in winter snowfall over karakoram and do not provide direct indications about the states of the glaciers the rising trend of august discharge is due to change in glacial storage at a steadily decreasing rate of approximately 0 04 0 05 mm day year for the period 1985 2010 this rate is nearly equal to the rate of increase in precipitation during the summer months over karakoram mountains in recent decades as determined from the era 40 and gpcp precipitation datasets thereby this is most plausibly why the glacial mass balance in central karakoram is nearly neutral the rising river flows accompanying non negative glacier mass balance are consistent with predicted future river flows derived from hydrologic modeling coupled with a climate projection suggesting increasing temperature and precipitation with unchanged glacier covers this investigation reconciles two apparently contradictory observations namely rising river flows and either zero or slightly positive mass balance of central karakoram glaciers

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

the boreal summer intraseasonal oscillation relationship between northward and eastward movement of convection the summertime intraseasonal oscillation iso is an important component of the south asian monsoon lagged regressions of intraseasonally filtered 25 80 days outgoing longwave radiation olr reveal that centers of convection move both northward and eastward from the central equatorial indian ocean subsequent to the initiation of an iso eastward movement of convection is also seen at indian subcontinent latitudes 10 8 208n based on the regression results the summertime iso convection signal appears as a band tilting northwestward with latitude and stretching from the equator to about 208n viewed along any meridian convection appears to propagate northward while equatorial convection propagates to the east to examine the robustness of the connection between eastward and northward movement individual isos are categorized and composited relative to the strength of the large scale eastward component of convection in the central equatorial indian ocean it is found that the majority of isos that exhibit northward movement onto the indian subcontinent 42 out of 54 isos or 78 also exhibit eastward movement into the western pacific ocean it is also found that when convection in the central indian ocean is not followed within 10 20 days by convection in the western pacific ocean 12 out of 54 isos or 22 the independent northward movement of convection in the indian ocean region is somewhat stunted the link between the eastward and northward movement of convection is consistent with an interpretation of the summertime iso in terms of propagating equatorial modes the northward moving portion of convection is forced by surface frictional convergence into the low pressure center of the rossby cell that is excited by equatorial iso convection a similar convergence pattern is seen for the northern winter iso but it does not generate poleward movement due to relatively cool ssts underlying the surface convergence

glaciological characteristics of the ablation zone of baltoro glacier karakoram pakistan baltoro glacier in the karakoram pakistan is one of the world s largest valley glaciers it drains an area of about 1500 km 2 and is 60km long in 2004 an italian german expedition carried out a glaciological field program on the ablation zone of the glacier focusing on the ablation conditions and the dynamic state of the glacier as baltoro glacier is a debris covered glacier ice ablation also depends on the debris properties stake measurements of ice ablation and debris cover in combination with meteorological data from automatic weather stations close by have been used to determine the local melt conditions results from these calculations have been combined with an analysis of different classes of surface cover and information about precipitation using remote sensing techniques in order to calculate mass fluxes for the upper part of baltoro glacier the dynamic state of the glacier has been investigated by gps based surface velocity measurements along the stake network a comparison of these short term measurements during the melt season with surface velocities computed from feature tracking of satellite images shows a high seasonal variability of the ice motion we have shown that this variability is up to 100 of the annual mean velocity on the basis of these investigations the mass fluxes at the concordia cross section have been quantified this approach can now be used together with the ablation calculations to reconstruct the variability of glacier extent and volume in the past using available climate data from the central karakoram from the comparison of historical measurements and photographs it is shown that the snout of baltoro glacier is oscillating back and forth a couple of hundred metres otherwise it seems not to react with the same magnitude as other glaciers to the climatic change elevation changes at concordia are a few tens of metres at the most

slight mass gain of karakoram glaciers in the early twenty first century the mass balance of hindu kush karakoram himalaya glaciers has been debated partly because of a severe lack of observations from the region an analysis of the regional mass balance of karakoram glaciers by comparison of digital elevation models from 1999 to 2008 reveals a small glacier mass gain in the area

the shape propagation and mean flow interaction of large scale weather systems abstract for a zonal average operator the eliassen palm flux provides a diagnostic of both eddy behavior and the feedback of the eddies onto the mean flow this paper addresses the diagnosis problem for other averaging operators and in particular for time averaging which has proved in recent years such a powerful means of viewing the three dimensional tropospheric flow the horizontal velocity correlation tensor gives a measure of the characteristic horizontal eddy shape at a point it also implies the direction of the group velocity relative to the mean flow in cases where such a concept is valid however the major emphasis here is on the mean flow feedback of eddies in this respect the eddy vorticity flux is determined by derivatives of the components of the anisotropic part of the tensor making a reasonable approximation allows the eddy vorticity flux convergence to be written in terms of e v 2 u 2 u v a simple interpretation of the mean flow feedback of eddies is then possible a sligh

planimetric and volumetric glacier changes in the khumbu himal nepal since 1962 using corona landsat tm and aster data multitemporal space imagery from 1962 corona kh 4 1992 landsat tm 2001 and 2005 terra aster was used to investigate the glacier changes in the khumbu himal nepal the ice coverage in the investigation area decreased by about 5 between 1962 and 2005 with the highest retreat rates occurring between 1992 and 2001 the debris coverage increased concomitantly with the decrease in total glacier area the clean ice area decreased by 10 digital terrain model dtm generation from the early corona kh 4 stereo data in this high relief terrain is time consuming and the results still contain some elevation errors however these are minor in the snow free areas with gentle slopes thus comparison of the surfaces of the debris covered glacier tongues based on the corona dtm and an aster dtm is feasible and shows the downwasting of the debris covered glaciers the highest downwasting rates more than 20 m 0 5 m a 1 can be found near the transition zone between the active and the stagnant glacier parts of the debris covered glacier tongues the downwasting is lower but still evident in the active ice areas and at the snout with thick debris cover all investigated debris covered glaciers in the study area show similar behaviour the estimated volume loss for the investigated debris covered glacier tongues is 0 19 km 3

reflectances of glaciers as calculated using landsat 5 thematic mapper data landsat 5 thematic mapper tm data have been used in previous work in order to locate zones of similar spectral reflectance on glaciers in austria and alaska and to relate these zones to the glacier facies which are indicative of glacier mass balance in this paper landsat 5 digital numbers dns have been used to compute the at satellite planetary reflectances p on spectrally similar zones on the meares and schwanda glaciers in alaska and the grossglockner glacier group in austria the patterns of tm derived reflectances in the ablation areas of the grossglockner glacier group and the meares glacier compare favorably with published reflectance curves measured on the surface of glacier ice though the surface reflectance of snow covered ice is higher than the landsat derived reflectance for the glaciers studied the accuracy of the at satellite planetary reflectances is shown to be affected by topographic and atmospheric effects and by the anisotropic nature of snow reflectance use of reflectance values for analysis of snow and ice facilitates scene to scene comparisons of glaciers

seasonal to interannual time scale dynamics of the equatorial undercurrent in the indian ocean abstractthis paper investigates the structure and dynamics of the equatorial undercurrent euc of the indian ocean by analyzing in situ observations and reanalysis data and performing ocean model experiments using an ocean general circulation model and a linear continuously stratified ocean model the results show that the euc regularly occurs in each boreal winter and spring particularly during february and april consistent with existing studies the euc generally has a core depth near the 20 c isotherm and can be present across the equatorial basin the euc reappears during summer fall of most years with core depth located at different longitudes and depths in the western basin the euc results primarily from equatorial kelvin and rossby waves directly forced by equatorial easterly winds in the central and eastern basin however reflected rossby waves from the eastern boundary play a crucial role while the first two baroclinic modes make the largest contribution intermediate modes 3 8 are also

a quantitative assessment of the genetic sources of the hydrologic flow regimes in upper indus basin and its significance in a changing climate summary reliable quantitative estimates of contributions melt water of different genetic sources make to river flows in himalayan river basins are largely unknown here we provide such estimates for upper indus basin uib analyses of historical flow records at 11 gauging stations spanning 14 48 years during a period of record from 1962 to 2010 reveal a uniform character of annual flow distributions at all gauging stations given by a gaussian function implying a unique glacio hydrometeorological condition prevailing throughout the basin controlling four hydrologic flow regimes within uib two low flow regimes occur during the months of october to december l1 and january to march l2 and two high flow regimes that occur during april june h1 and july september h2 for all stations flow magnitudes follow h2 h1 l1 l2 in the main stem of upper indus river the contributions to total annual flow volumes m 3 during these flow regimes are 53 62 during h2 24 32 during h1 8 9 during l1 and 4 6 during l2 in the main tributaries these ranges are 47 74 during h2 15 38 during h1 8 10 during l1 and 4 6 during l2 separation of annual hydrographs by linear smoothing and recursive digital filtering technique shows that the annual contribution of melt water m2 from an elevation band 3500 5300 m to total annual flow volume m 3 varies from 41 to 54 along the main stem of indus upstream of the himalayan foothills contribution of melt water m1 from an elevation band 2500 3500 m varies from 16 to 29 in the tributaries annual contributions of m2 vary from 37 to as high as 65 similarly annual contributions of m1 in the tributaries vary from as low as 12 to 34 thus the relative importance of melt water originating from high altitudes far overweighs that originating from mid altitudes in river runoff within uib the chief component of m1 is seasonal snows whereas m2 is a mixture of glacial melts seasonal snows falling in winter and spring and monsoonal snows falling in the summer july september the m2 component contributes to base flows during l1 regime base flow recession occurs during l2 regime during the h2 regime three watersheds with greatest glaciated surfaces straddling the karakoram mountains contribute 48 54 of flows at shatial bridge a point upstream of tarbela reservoir up to which rainfall contributions to river discharges in uib are inconsequential during the h1 regime these watersheds drained by shyok shigar and hunza rivers contribute 20 31 of flows at this point during l1 and l2 regimes their contributions are 33 39 and 31 32 respectively contributions of glacial melt and snowmelt to annual river flows vary from 18 35 and 38 50 respectively in the major tributaries and the main stem of upper indus depending on the location upper indus river just upstream of tarbela reservoir carries annual flows constituted of 70 melt water of which 21 is contributed by glacial melts and 49 by snowmelts thus changes in climatic trends will greatly control the future water availability within uib if glacial retreat and reduction of the perennial snow and ice covers are happening in uib in a changing climate then there will indeed be long term reductions in river flows in uib and hence sustainability of water resources in this basin will potentially be at risk

an energy balance model for debris covered glaciers including heat conduction through the debris layer extensive covers of supraglacial debris are often present in glacier ablation areas and it is essential to assess exactly how the debris affects glacier melt rates this paper presents a physically based energy balance model for the surface of a debris covered glacier the model is driven by meteorological variables and was developed using data collected at miage glacier italy during the ablation seasons of 2005 2006 and 2007 the debris surface temperature is numerically estimated by considering the balance of heat fluxes at the air debris interface and heat conduction through the debris is calculated in order to estimate melt rates at the debris ice interface the predicted hourly debris surface temperatures and debris internal temperatures provide a good fit to temperatures measured on rock covered miage glacier r 2 0 94 and the tephra covered glacier on villarrica volcano chile r 2 0 82 the model can also be used to reproduce observed changes in melt rates below debris layers of varying types and thicknesses an important consideration for the overall mass balance of debris covered glaciers

a comprehensive mass flux scheme for cumulus parameterization in large scale models abstract observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large scale models but this approach through the introduction of a spectral cloud ensemble leads normally to rather complex schemes in this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions this is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection gate marshall islands tradewind cumuli atex bomex and extratropical organized convection sesame 79 and then in a nwp model the scheme considers a population of clouds where the cloud ensemble is described by a one dimensional bulk model as earlier applied by yanai et al in a diagnostic study of tropical convection cumulus scale downdrafts are included various types of convection are represented i e penetrative convection in c

variability of zonal currents in the eastern equatorial indian ocean on seasonal to interannual time scales this study examines equatorial zonal current variations in the upper layers of eastern indian ocean in relation to variations in the indian ocean dipole iod the analysis utilizes data from the research moored array for african asian australian monsoon analysis and prediction rama and the european centre for medium range weather forecasts ocean reanalysis system 4 ecmwf oras4 surface currents are characterized by semiannual eastward flowing wyrtki jets along the equator in boreal spring and fall forced by westerly monsoon transition winds the fall jet intensifies during negative iod niod events when westerlies are anomalously strong but significantly weakens during positive iod piod events when westerlies are anomalously weak as zonal wind stress weakens during piod events sea surface height becomes unusually low in the eastern basin and high in the west setting up an anomalous pressure force that drives increased eastward transport in the thermocline opposite tendencies are evident during niod events in response to intensified equatorial westerlies current transport adjustments to anomalous zonal wind forcing during iod events extend into the following year consistent with the cycling of equatorial wave energy around the basin a surface layer mass budget calculation for the eastern sea surface temperature sst pole of the iod indicates upwelling of 2 9 0 7 sv during normal periods increasing by 40 50 during piod events and reducing effectively to zero during niod events iod related variations in wyrtki jet and thermocline transports are major influences on these upwelling rates and associated water mass transformations which vary consistently with sst changes

coordinated influences of the tropical and extratropical intraseasonal oscillations on the 10 30 day variability of the summer rainfall over southeastern china this study explores the spatial variations and physical mechanisms of 10 30 day rainfall anomalies over southeastern china based on daily station observed rainfall data for the period 1979 2015 empirical orthogonal function analysis shows that the dominant spatial distribution of 10 30 day rainfall anomalies is a monopole pattern over the south of the middle and lower reaches of the yangtze river valley smly lead lag composites reveal that the evolution of such a monopole pattern depends on the coordinated influences of 10 30 day atmospheric intraseasonal oscillations isos from the tropics and mid high latitudes in the upper troposphere the southeastward propagating rossby wave train from the mid high latitudes which presents as anomalous anticyclones and cyclones alternating over eastern europe to southeastern coastal area of china induces strong ascents descents over the smly via vorticity advection circulation anomalies associated with tropical iso over east asia western north pacific trigger a vertical cell with strong updraft downdraft over the smly and downdraft updraft to the south further enhancing the ascents descents over the smly forming the wet dry phases of 10 30 day rainfall anomalies moreover due to the meridional non uniformity of iso related diabatic heating along the indian ocean longitudes an anticyclone cyclone is generated over the central indian northern bay of bengal which tends to anchor the anomalous ascents descents over the smly through its interaction with the intraseasonal rossby wave from mid high latitudes thus favoring the persistence of wet dry phases of the 10 30 day smly rainfall anomalies

intraseasonal teleconnection between the summer eurasian wave train and the indian monsoon this study investigated the most recurrent coupled pattern of intraseasonal variability between midlatitude circulation and the indian summer monsoon ism the leading singular vector decomposition svd pattern reveals a significant coupled intraseasonal variation between a rossby wave train across the eurasian continent and the summer monsoon convection in northwestern india and pakistan hereafter referred to as nism the wave train associated with an active phase of nism rainfall displays two high pressure anomalies one located over central asia and the other over northeastern asia they are accompanied by increased rainfall over the western siberia plain and northern china and decreased rainfall over the eastern mediterranean sea and southern japan the circulation of the wave train shows a barotropic structure everywhere except the anomalous central asian high located to the northwest of india where a heat induced baroclinic circulation structure dominates the time lagged svd analysis shows that the midlatitude wave train originates from the northeastern atlantic and traverses europe to central asia the wave train enhances the upper level high pressure and reinforces the convection over the nism region meanwhile it propagates farther toward east asia along the waveguide provided by the westerly jet after an outbreak of nism convection the anomalous central asian high retreats westward composite analysis suggests a coupling between the central asian high and the convective fluctuation in the nism the significance of the midlatitude ism interaction is also revealed by the close resemblance between the individual empirical orthogonal functions and the coupled svd modes of the midlatitude circulation and the ism it is hypothesized that the eastward and southward propagation of the wave train originating from the northeastern atlantic contributes to the intraseasonal variability in the nism by changing the intensity of the monsoonal easterly vertical shear and its associated moist dynamic instability on the other hand the rainfall variations over the nism reinforce the variations of the central asian high through the monsoon desert mechanism thus reenergizing the downstream propagation of the wave train the coupling between the eurasian wave train and nism may be instrumental for understanding their interaction and can provide a way to predict the intraseasonal variations of the indian summer monsoon and east asian summer monsoon

biweekly and 21 30 day variations of the subtropical summer monsoon rainfall over the lower reach of the yangtze river basin abstract the lower reach of the yangtze river basin lyrb is located at the central region of the mei yu and baiu front which represents the subtropical east asian ea summer monsoon based on the newly released daily rainfall data two dominant intraseasonal variation isv modes are identified over the lyrb during boreal summer may august with spectral peaks occurring on day 15 the biweekly mode and day 24 the 21 30 day mode these two modes have comparable intensities and together they account for above about 57 of the total intraseasonal variance both isv modes exhibit baroclinic structures over the lyrb at their extreme phases however the genesis and evolutions associated with the two modes are different considering the genesis of their extreme wet phases over the lyrb the biweekly mode is initiated by a midlatitude jet stream vorticity anomaly moving southeastward while the 21 30 day mode is primarily associated with a low level westward propagation of an anticyclonic anomaly from

the effect of midlatitude transient eddies on monsoonal southerlies over eastern china abstractthe strengthening of monsoonal southerlies over east asia is associated with the westward intensification of the north pacific subtropical high previous work has shown that the seasonal mean position and strength of subtropical highs are affected by tropical and subtropical diabatic heating here it is shown that the synoptic time scale strengthening of southerlies over eastern china is dynamically tied to extratropical eddy activity composite analysis based on strong southerly wind events highlights an antecedent baroclinic wave train propagating southeastward into eastern china from extratropical central asia this wave train generates quasigeostrophic ascent over eastern china that is associated with heavy precipitation the anomalously cold upper tropospheric conditions associated with the wave train decrease static stability throughout the lower and middle troposphere in eastern china while low level moistening enhances equivalent potential temperature it is proposed that the resulting re