the role of bay of bengal convection in the onset of the 1998 south china sea summer monsoon abstract assimilated analysis fields from the south china sea monsoon experiment and the outgoing longwave radiation data from the national center for atmospheric research ncar have been employed to describe the large scale and synoptic features of the subtropical circulation during the bay of bengal bob 6 20 n 80 100 e and south china sea scs 7 20 n 110 120 e monsoon onsets in 1998 the results show that the asian monsoon onset during may 1998 exhibited a typical eastward development from the bob region to the scs domain the weakening and retreat of the subtropical anticyclone from the scs were preceded by the intrusion of westerlies and the development of convective activities over the northern part of the scs nscs 15 20 n 110 120 e as the vertical shear of zonal wind changes in sign the ridge surface of the subtropical anticyclone tilted northward and the summer pattern was established over the scs based on these observational results version 4 of the ncar climate model ccm3

impact of the eruptive activity on glacier evolution at popocatepetl volcano mexico during 1994 2004 abstract distribution rate and magnitude of the glacier changes caused by eruptive activity over 1994 2001 at popocatepetl volcano were determined digital elevation models computed by scanned photographs within a digital photogrammetric workstation and the subsequent dem comparison allowed the determination of glacial changes the results show that drastic changes occurred in glacier geometry and morphology over 1996 2001 53 of the glacier surface area was lost due to melting processes the most important loss occurred over 2000 2001 when 19 of the glacier covered area disappeared the glacier volume losses increased over time during 1999 2000 the largest loss was observed however in february 2001 the glacier showed an apparent small increase in volume volcanic processes disturbed the mass balance of the glacier thereby accelerating the ablation processes the eruptive behavior of popocatepetl was characterized during this time by alternating periods of explosive events and low activity pyroclastic flow generation ejection of incandescent material and tephra fall affected the glacier the tephra volume distribution and remobilization produced considerable changes on glacier evolution tephra deposition on the glacier surface was the most frequent process the irregular distribution and thickness of tephra provoked differential ablation and tephra remobilization processes took place on the glacier surface together these processes incised the glacier surface over time based on these results and observations a model of glacier evolution is proposed involving an adjustment phase thinning phase areal retreat phase and fragmentation phase a complex interplay of factors and processes took place between eruptive activity and the glaciers at popocatepetl volcano the glacier evolution and subsequent extinction were induced by the eruptive behavior over the years while not the only process at work eruptive activity played the primary role in accelerating retreat and as a consequence in glacier extinction

effects of the november 13 1985 eruption on the snow pack and ice cap of nevado del ruiz volcano colombia abstract about twenty five to thirty percent of the ice on the ice cap of nevado del ruiz was fractured and destabilized by earthquakes and explosive activity on november 13 1985 comparison of aerial and ground photographs taken before and after the eruption allows calculation of the volume of snow and ice removed from each glacial basin during the eruption about 16 4 2 km 2 of the surface area of the ice and snow was lost the corresponding volume is estimated to be close to 0 06 km 3 or 9 of the total volume of ice and snow at least four distinct processes including explosions ice avalanches surficial erosion of snow and slush avalanches were responsible for transporting snow firn and ice downslope heat from pyroclastic flows and surges and their deposits was responsible for melting snow and ice both at the surface of the ice cap in situ and during its downslope transport voluminous lahars were triggered in 3 of the 4 main drainages on the volcano by the approximately 43 million m 3 of liquid water about 62 million m 3 of snow firn and ice produced by these combined processes thermal and mechanical effects of the pyroclastic flows and surges included scouring direct melting and entraining snow firn and ice which left several erosional features on the ice cap and deposits both on the ice and on the edges of the ice cap subsurface and englacial drainage of water through crevasses was deduced from depositional and morphological features at the ice margins some meltwater might have been trapped in reservoirs but some water was also released shortly after the eruption the estimated volume of released meltwater is about 43 million m 3 i e 2 4 times more than the approximate 11 12 million m 3 of water incorporated into the lahars thus roughly 21 million m 3 of water were released but did not contribute to lahar generation this non contributing water was 1 included in snow avalanches and sediment laden slush avalanches outside the lahars channels or bound up in the wet pyroclastic surge deposits 2 incorporated in the phreatic explosive products or saturated firn by meltwater which issued from the thermal effect of the tephra fall 3 sublimated into steam during the passage of the pyroclastic flows or 4 stored within the ice meltwater may still be be trapped within the ice cap and may be a potential source of water for future lahars

the asian summer monsoon an intercomparison of cmip5 vs cmip3 simulations of the late 20th century the boreal summer asian monsoon has been evaluated in 25 coupled model intercomparison project 5 cmip5 and 22 cmip3 gcm simulations of the late twentieth century diagnostics and skill metrics have been calculated to assess the time mean climatological annual cycle interannual variability and intraseasonal variability progress has been made in modeling these aspects of the monsoon though there is no single model that best represents all of these aspects of the monsoon the cmip5 multi model mean mmm is more skillful than the cmip3 mmm for all diagnostics in terms of the skill of simulating pattern correlations with respect to observations additionally for rainfall convection the mmm outperforms the individual models for the time mean the interannual variability of the east asian monsoon and intraseasonal variability the pattern correlation of the time pentad of monsoon peak and withdrawal is better simulated than that of monsoon onset the onset of the monsoon over india is typically too late in the models the extension of the monsoon over eastern china korea and japan is underestimated while it is overestimated over the subtropical western central pacific ocean the anti correlation between anomalies of all india rainfall and nino3 4 sea surface temperature is overly strong in cmip3 and typically too weak in cmip5 for both the enso monsoon teleconnection and the east asian zonal wind rainfall teleconnection the mmm interannual rainfall anomalies are weak compared to observations though simulation of intraseasonal variability remains problematic several models show improved skill at representing the northward propagation of convection and the development of the tilted band of convection that extends from india to the equatorial west pacific the mmm also well represents the space time evolution of intraseasonal outgoing longwave radiation anomalies caution is necessary when using gpcp and cmap rainfall to validate 1 the time mean rainfall as there are systematic differences over ocean and land between these two data sets and 2 the timing of monsoon withdrawal over india where the smooth southward progression seen in india meteorological department data is better realized in cmap data compared to gpcp data

recent geomorphologic evolution of a glaciovolcanic active stratovolcano popocatepetl mexico abstract the recent geomorphologic evolution of the statovolcano popocatepetl 19 03 n 98 35 w including the volcanic activity and the evolution of the glacier that still exists on the north face was assessed most of the data were obtained from references in historical sources and aerial photographs dating from 1945 this information was supplemented with data from fieldwork conducted between 1992 and 1995 landform typology shows volcanic and glacial interactions the conclusions affirm that a geomorphologic evolution of the volcano occurred since the maximum glacier advance in the little ice age lia and the formation of a proglacial ramp later fluvioglacial gorges cut into the ramp especially during the 1921 27 eruption once the glacier had shrunk to a small size and was left hanging above the steep slope the streams disappeared and the gorges filled with blocks that fell in snow and ice avalanches

asian summer monsoon onset barrier and its formation mechanism the onset process of asian summer monsoon asm is investigated based on diagnostic analysis of observations of precipitation and synoptic circulation results show that after the asm commences over the eastern bay of bengal bob around early may the onset can propagate eastwards towards the south china sea and western pacific but is blocked on its westward propagation along the eastern coast of india this blocking termed the monsoon onset barrier mob presents a gill type circulation response to the latent heating released by bob monsoon convection this convective condensation heating generates summertime wintertime vertical easterly westerly shear to its east west and facilitates air ascent descent the convection then propagates eastward but gets trapped on its westward path to the east of the central bob the surface air temperature sat cools faster than the underlying sea surface temperature sst due to monsoon onset thus more sensible heat flux supports the onset convection to propagate eastward to the west of the central bob however the land surface sensible heating over the indian peninsula is strengthened by the enhanced anticyclone circulation and air descent induced by the bob monsoon heating the strengthened upstream warm horizontal advection then produces a warm sat center over the mob region which together with the in situ cooled sst reduces the surface sensible heating and atmospheric available potential energy to prevent the occurrence of free convection therefore it is the change in both large scale circulation and air sea interaction due to bob summer monsoon onset that contributes to the mob formation

a comparison of ship drift drifting buoy and current meter mooring velocities in the pacific south equatorial current in this note we compare mean seasonal cycles of zonal and meridional velocity in the pacific south equatorial current based on current meter mooring data drifting buoy data and ship drift data monthly averages of ship drift and drifting buoy data were computed over 2 latitude by 10 longitude rectangles centered at the positions of multiyear current meter moorings near 0 110 w and 0 140 w all three representations of the flow field show the basic character of the annual mean and its variations provided that the sampling characteristics associated with each measurement technique are taken into account in particular we find that more than 15 days of drifter data regardless of year are required on a 2 latitude by 10 longitude basis to produce monthly mean estimates that agree with moored estimates to within about 5 10 cm s 1 rms we also infer that windage affects climatological monthly mean ship drift velocities although uncertainties in the data limit a precise determination of the windage magnitude an upper bound appears to be about 3 of the surface wind speed though the actual effect of windage may be considerably smaller

mesoscale convection and bimodal cyclogenesis over the bay of bengal abstractmesoscale convective systems mcss are an essential component of cyclogenesis and their structure and characteristics determine the intensity and severity of associated cyclones case studies were performed by simulating tropical cyclones that formed during the pre and postmonsoon periods in 2007 and 2010 over the bay of bengal bob the pre post monsoon environment was characterized by the coupling of northwesterly southwesterly wind to the early advance southwesterly northeasterly monsoonal wind in the bob the surges of low level warm southwesterlies with clockwise rotating vertical shear in the premonsoon period and moderately cool northeasterlies with anticlockwise rotating vertical shear in the postmonsoon period transported moisture and triggered mcss within preexisting disturbances near the monsoon trough over the bob mature mcss associated with bimodal cyclone formations were quasi linear and they featured leading edge deep convection and a trailing stratiform precipitation r

extreme precipitation events in the middle east dynamics of the active red sea trough 1 the active red sea trough arst is an infrequent weather phenomenon that is associated with extreme precipitation flash floods and severe societal impacts in the middle east me using reanalysis era interim and observational precipitation aphrodite and stations data we investigate its underlying dynamics geographical extent and seasonality twelve arst events affecting the levant have the same dynamical characteristics as those associated with a major flood in jeddah saudi arabia on 25 november 2009 hence the jeddah flooding was caused by an arst which implies that arsts can affect a much larger part of the me than previously assumed we present an arst concept involving six dynamical factors 1 a low level trough the red sea trough rst 2 an anticyclone over the arabian peninsula the arabian anticyclone aa 3 a transient midlatitude upper trough 4 an intensified subtropical jet stream 5 moisture transport pathways and 6 strong ascent resulting from tropospheric instability and the synoptic scale dynamical forcing we explain the arst as the interaction of a persistent stationary wave in the tropical easterlies i e the rst with a superimposed amplifying rossby wave resulting in northward propagating moist air masses over the red sea our findings emphasize the relevance of the aa causing moisture transport from the arabian and red seas the particular topography in the red sea region and associated low level circulation makes the arst unique among tropical extratropical interactions the arst seasonality is explained by the large scale circulation and in particular the seasonal cycle of the semipermanent quasi stationary rst and aa

tephra snow and water complex sedimentary responses at an active snow capped stratovolcano ruapehu new zealand a feature of small scale explosive volcanism at stratovolcanoes is the rapid destruction of primary near vent pyroclastic deposits by sedimentary processes a protracted series of explosive eruptions of moderate volume from september 1995 until july 1996 at mount ruapehu in new zealand its largest eruptive episode this century afforded an opportunity to study these remobilisation processes in detail all significant sub plinian eruptions occurred in mid winter forming metre thick tephra accumulations on steep slopes covered with perennial ice and seasonal snow subsequent events demonstrated the variety and complexity of the erosion processes that remobilise primary pyroclasts in such a setting these processes arose from the complex interactions of tephra with snow and ice and liquid water in varying proportions and were very diverse in nature and scale their effectiveness can be gauged from the fact that there is almost no stratigraphic record of any of the 40 eruption episodes recorded in the past 100 years at ruapehu syn eruptive remobilisation processes included the generation of eruption triggered lahars by the ejection of hot water from the crater lake post eruptive interactions mainly remobilised fall deposits from proximal areas and included rain triggered lahars which were among the largest and most hazardous events with the greatest distal impacts

influences of enso on the vertical coupling of atmospheric circulation during the onset of south asian summer monsoon based on multiple sources of atmospheric and oceanic data this study performs a series of composite analysis of the south asian summer monsoon sasm onset against enso events and indicates that warm cold enso events induce later earlier onset of the sasm by modulating the vertical coupling of the upper and lower level circulation over the south asia specifically during the monsoon onset of bay of bengal bob the enso induced convection anomalies over the southern philippines can modulate the position of south asian high sah in late april in the upper troposphere which evolves to affect the monsoon onset convection by changing the upper divergence pumping effect in the lower troposphere enso induces an anomalous zonal gradient of sea surface temperature sst over the indian western pacific ocean to alter the barotropic instability which further affects the formation of bob monsoon onset convection during the indian summer monsoon onset the anomalous convection over northeastern bob and indochina peninsula in late may act to change the sah position and its relevant upper divergence pumping over the arabian sea as meanwhile the indian monsoon onset convection is also modulated by the enso induced changes in intensity of the inertial instability and the forced convection over the as which are related to an enso induced anomalous cross equatorial sst gradient and zonally asymmetric meridional gradient of sea level pressure and an anomalous westerly over the central as in the lower troposphere results demonstrate that during the bob and india monsoon onset the influences of enso on the upper circulation are similar but are distinctly different on the lower level circulation

what controls seasonal variations of the diurnal cycle of sea surface temperature in the eastern tropical indian ocean abstractrecent in situ buoy observations revealed interesting seasonal features of the diurnal sea surface temperature cycle dsst in the eastern tropical indian ocean composite analysis shows that areas away from the equator exhibit stronger seasonal variations of dsst while weaker seasonal variations appear near the equator the most interesting characteristic is the distinctive contrast of the seasonal variations of dsst between the bay of bengal bob and the region south of the equator particularly around 12 s while the range of dsst is weakest in the bob during boreal summer it has its largest range around 12 s in austral summer furthermore bob dsst exhibits two peaks that occur during the monsoon transitions march april and october whereas dsst south of the equator shows only a single peak in its annual cycle using a one dimensional oceanic mixed layer model the authors examined the cause of the distinctive annual cycles of dsst north and south of the equator two parallel experiment

strong modulations on the bay of bengal monsoon onset vortex by the first northward propagating intra seasonal oscillation monsoon onset vortex ov in the form of tropical cyclone is often observed in the pre monsoon period and contributes to the subsequent abrupt establishment of summer monsoon over the bay of bengal bob it is identified here that all historical ovs occurred during the convection enhanced phase of the first northward propagating intra seasonal oscillation fniso the individual contributions from the four large scale environmental fields associated with the intra seasonal variations to the cyclone genesis are diagnosed with the aid of the genesis potential index the significant moistening of mid level atmosphere which is embedded in the fniso convection enhanced phase is shown to be the primary factor leading to the cyclone genesis the water vapor budget analysis is further done to understand the governing process for the mid level humidity increase it is clearly seen that the vertical advection process dominated by the anomalous vertical advection of the mean vertical water vapor gradient plays the critical role hence the ovs are shown to be strongly modulated by fnisos both of which are important elements of the complex story of the bob monsoon onset

lahar flow simulations using laharz program application for the popocatepetl volcano mexico lahars are a type of catastrophic event that is generated in volcanic environments due to the recent technological advances computer simulated models have become widely used by the scientific community to predict the distribution of catastrophic events such as floods debris avalanches earth landslides or lahars and to mitigate possible damage to populations located in a risk area our study risk area is located in the popocatepetl volcano a large and active stratovolcano in the trans mexican volcanic belt here lahars have been occurring during the last century and some of them have seriously affected nearby towns since one of the main input parameters into a lahar simulation is the digital elevation model dem this paper focuses on studying lahar simulations on popocatepetl using dems obtained from various sources with the aid of a popular package known as laharz the first simulations were performed using a 1 50 000 topographic map with 20 m contours interval the second set of tests used an enhanced dem with profiles measured during fieldwork in the lahar channel in the last set of tests we added lateral artificial barriers to the channel profiles used in the previous enhanced dem our results show that the use of high resolution and detailed dems does not necessarily guarantee a realistic lahar simulation as was previously thought and a detailed explanation as to why the laharz code computation creates ragged edges is offered our results also offer useful information on the level of detail necessary for an input dem into laharz in order to obtain lahar simulations closer to real lahars the minimum resolution for the dem used in simulations must be less than the width of the narrowest cross section of the channel to realistically reproduce the lahars for dems with lower resolution sometimes the modeled lahars are shorter in length and therefore underestimate real hazards to populations also the results show that lateral barriers are sometimes needed to obtain more realistic inundation areas

onset of the south west monsoon and sea surface temperature anomalies in the arabian sea in 1979 the year of the global weather experiment the atmosphere and ocean of the monsoon region were particularly well observed for this reason the onset period of the monsoon 11 19 june 1979 was selected for international comparison of numerical prediction models1 previous studies2 4 have demonstrated that successful predictions for this period are difficult to achieve i report here two examples of numerical predictions that highlight the role of sea surface temperatures namely a control forecast using climatological sea surface temperatures and an anomaly forecast using more realistic and warmer surface temperatures specified for the eastern arabian sea it is shown that the use of the more accurate sea surface temperatures enables a better prediction of the development of a monsoon depression to be obtained

extremely early summer monsoon onset in the south china sea in 2019 following an el nino event abstractthe el nino southern oscillation enso is regarded as one of the most important factors for onset of the south china sea summer monsoon scssm previous studies generally indicated that a

genesis of the south asian high and its impact on the asian summer monsoon onset abstractthe formation of the south asian high sah in spring and its impacts on the asian summer monsoon onset are studied using daily 40 yr ecmwf re analysis era 40 data together with a climate mean composite technique and potential vorticity diabatic heating pv q analysis results demonstrate that about 2 weeks before the asian summer monsoon onset a burst of convection over the southern philippines produces a negative vorticity source to its north the sah in the upper troposphere over the south china sea is then generated as an atmospheric response to this negative vorticity forcing with the streamline field manifesting a gill type pattern afterward the persistent rainfall over the northern indochinese peninsula causes the sah to move westward toward the peninsula consequently a trumpet shaped flow field is formed to its southwest resulting in divergence pumping and atmospheric ascent just over the southeastern bay of bengal bob near the surface as a surface anticyclone is formed over t

improved extended reconstruction of sst 1854 1997 abstract an improved sst reconstruction for the 1854 1997 period is developed compared to the version 1 analysis in the western tropical pacific the tropical atlantic and indian oceans more variance is resolved in the new analysis this improved analysis also uses sea ice concentrations to improve the high latitude sst analysis and a modified historical bias correction for the 1939 41 period in addition the new analysis includes an improved error estimate analysis uncertainty is largest in the nineteenth century and during the two world wars due to sparse sampling the near global average sst in the new analysis is consistent with the version 1 reconstruction the 95 confidence uncertainty for the near global average is 0 4 c or more in the nineteenth century near 0 2 c for the first half of the twentieth century and 0 1 c or less after 1950

the effect of a sea surface temperature anomaly on a prediction of the onset of the south west monsoon over india at the time of the onset of the monsoon in june 1979 the sea surface temperatures in the eastern arabian sea were higher than normal a prediction experiment designed to reveal the effects of this anomaly on the onset is described this involves two 8 day forecasts made using the same model and the same initial conditions they differ only in using different sea surface temperatures in the eastern arabian sea a better prediction of the onset is obtained by using the anomalously high temperatures rather than the normal climatological values in particular the development of a tropical storm over the arabian sea the strengthening of the somali jet and the northward movement of the rainfall over india are all better predicted the mechanism of the onset in the model is discussed and two important feedback loops are identified one involving moisture flux convergence and the other involving the surface fluxes of sensible and latent heat the most important factor in both loops is the release of latent heat over the arabian sea a linear model is used to show that the onset may be thought of as a response to this heating the roles of barotropic and baroclinic processes in the onset are also discussed

the interaction of moist convection and mid level dry air in the advance of the onset of the indian monsoon the advance of the onset of the indian monsoon is here explained in terms of a balance between the low level monsoon flow and an over running intrusion of mid tropospheric dry air the monsoon advances over a period of about 6 weeks from the south of the country to the northwest given that the low level monsoon winds are westerly or southwesterly and the midlevel winds northwesterly the monsoon onset propagates upwind relative to midlevel flow and perpendicular to the low level flow and is not directly caused by moisture flux toward the northwest lacking a conceptual model for the advance means that it has been hard to understand and correct known biases in weather and climate prediction models the mid level northwesterlies form a wedge of dry air that is deep in the far northwest of india and over runs the monsoon flow the dry layer is moistened from below by shallow cumulus and congestus clouds so that the profile becomes much closer to moist adiabatic and the dry layer is much shallower in the vertical toward the southeast of india the profiles associated with this dry air show how the most favourable environment for deep convection occurs in the south and onset occurs here first as the onset advances across india the advection of moisture from the arabian sea becomes stronger and the mid level dry air is increasingly moistened from below this increased moistening makes the wedge of dry air shallower throughout its horizontal extent and forces the northern limit of moist convection to move toward the northwest wetting of the land surface by rainfall will further reinforce the north westward progression by sustaining the supply of boundary layer moisture and shallow cumulus the local advance of the monsoon onset is coincident with weakening of the mid level northwesterlies and therefore weakened mid level dry advection

impact of tropical cyclone development on the instability of south asian high and the summer monsoon onset over bay of bengal this paper analyzes the evolution of the south asian high sah during and after the development of tropical cyclone neoguri over the south china sea scs in mid april 2008 the formation of tropical storm nargis over the bay of bengal bob in late april and the asian summer monsoon onset as well as their interrelationships numerical sensitivity experiments are conducted to explore the underlying mechanism responsible for these seasonal transitions in 2008 it is demonstrated that strong latent heating related with tropical cyclone activities over the scs can enhance the development of the sah aloft and generate zonal asymmetric potential vorticity pv forcing with positive vorticity advection to its east and negative advection to its west following the decay of the tropical cyclone this asymmetric forcing leads to instability development of the sah presenting as a slowly westward propagating rossby wave accompanied by a westward shift of the high pv advection a strong upper tropospheric divergence on the southwest of the sah also shifts westward while positive pv eddies are shed from the high pv advection and eventually arrives in the southern bob such synoptic patterns provide favorable pumping conditions for local cyclonic vorticity to develop the latent heating release from the cyclogenesis further intensifies the upper layer divergence and the lower and upper circulations become phase locked leading to the explosive development of the tropical cyclone over the southern bob consequently a tropical storm is generated and the bob summer monsoon commences

geochemical surveillance of magmatic volatiles at popocatepetl volcano mexico surveillance of popocatepetl volcanic plume geochemistry and so 2 flux began in early 1994 after fumarolic and seismic activity increased significantly during 1993 volatile traps placed around the summit were collected at near monthly intervals until the volcano erupted on december 21 1994 additional trap samples were obtained in early 1996 before the volcano erupted again emplacing a small dacite dome in the summit crater abundances of volatile constituents ppm day of cl s total f co 2 hg and as varied but most constituents were relatively high in early and late 1994 however ratios of these constituents to cl were highest in mid 1994 34 s s total in trap solutions ranged from 1 5 to 6 4 lowest values generally occurred during late 1994 13 c co 2 of trap solutions were greatly contaminated with atmospheric co 2 and affected by absorption kinetics when trap data are combined with so 2 flux measurements made through november 1996 popocatepetl released about 3 9 mt so 2 16 mt co 2 0 75 mt hcl 0 075 mt hf 260 t as 2 6 t hg and roughly 200 mt h 2 o near vent gas concentrations in the volcanic plume measured by correlation spectrometer cospec and fourier transform infrared ftir commonly exceed human recommended exposure limits and may constitute a potential health hazard volatile geochemistry combined with petrologic observations and melt inclusion studies show that mafic magma injection into a preexisting silicic chamber has accompanied renewed volcanism at popocatepetl minor assimilation of cretaceous wall rocks probably occurred in mid 1994

local oceanic precursors for the summer monsoon onset over the bay of bengal and the underlying processes abstractlocal sea surface temperature sst plays an important role in the onset of the bay of bengal bob summer monsoon bobsm previous study indicated that the meridionally warmest sst axis wssta appears in mid april in the central bob which may be a precursor for the bobsm onset in this study it is found that a warm but not the meridionally warmest center which is defined as the secondary wssta swssta occurs in early april in the central bob leading the bobsm onset by five pentads dates of the swssta occurrence are significantly positively correlated with dates of the wssta occurrence in the central bob and the bobsm onset on an interannual time scale the swssta is an earlier precursor for the bobsm onset the formation of the oceanic precursor and its impact on the bobsm onset are as follows before the bobsm onset resulting from more surface heat input and shallower mixed layer affected by the low level anticyclone and subtropical high in the central bob local sst shows the most rap

the glaciers of popocatepetl volcano mexico changes and causes an updated inventory of popocatepetl volcano s glaciers and field observations for 1977 1992 is presented two glaciers 0 559 km 2 and four permafrost fields 0 239 km 2 are reported here comparing new descriptions of the glaciar del ventorrillo with previous descriptions a systematic retreat pattern is identified the average retreat rate in terms of terminus altitude for 1906 1968 is nearly 7 m year advance rate 10 m year for 1968 1978 and a response of glacier terminus is documented for 1978 1982 at 40 m year morphological changes are a reduction of 25 in the glaciated area and strong retreat of the tezcalco tongue glaciar noroccidental is a stationary glacierette whose area was reduced by 12 in 34 years total glaciated area was reduced by 22 permafrost fields are located around the glaciers and are the remains of larger glaciers fluctuations are explained in terms of a an increase of heat flow b local climatic changes c global climatic changes and d a combination of these further work is needed to evaluate the role of the glaciers in the local environment the impact of the local and global climate on them the role they would play in the case of explosive activity of popocatepetl and its consequences

air sea interaction and formation of the asian summer monsoon onset vortex over the bay of bengal in spring over the southern bay of bengal bob a vortex commonly develops followed by the asian summer monsoon onset an analysis of relevant data and a case study reveals that the bob monsoon onset vortex is formed as a consequence of air sea interaction over bob which is modulated by tibetan plateau forcing and the land sea thermal contrast over the south asian area during the spring season tibetan plateau forcing in spring generates a prevailing cold northwesterly over india in the lower troposphere strong surface sensible heating is then released forming a prominent surface cyclone with a strong southwesterly along the coastal ocean in northwestern bob this southwesterly induces a local offshore current and upwelling resulting in cold sea surface temperatures ssts the southwesterly together with the near equatorial westerly also results in a surface anticyclone with descending air over most of bob and a cyclone with ascending air over the southern part of bob in the eastern part of central bob where sky is clear surface wind is weak and ocean mixed layer is shallow intense solar radiation and low energy loss due to weak surface latent and sensible heat fluxes act onto a thin ocean layer resulting in the development of a unique bob warm pool in spring near the surface water vapor is transferred from northern bob and other regions to southeastern bob where surface sensible heating is relatively high the atmospheric available potential energy is generated and converted to kinetic energy thereby resulting in vortex formation the vortex then intensifies and moves northward where sst is higher and surface sensible heating is stronger meanwhile the zonal mean kinetic energy is converted to eddy kinetic energy in the area east of the vortex and the vortex turns eastward eventually southwesterly sweeps over eastern bob and merges with the subtropical westerly leading to the onset of the asian summer monsoon