thermal infrared data analyses of meteor crater arizona implications for mars spaceborne data from the thermal emission imaging system thermal infrared tir data from the advanced spaceborne thermal emission and reflection radiometer aster instrument are used to identify the lithologic distribution of the meteor crater ejecta blanket and nearby within 3 km region this has many applications to the analysis of data from the thermal emission imaging system themis instrument that is currently in orbit at mars aster and themis whereas orbiting different planets have similar spatial and spectral resolutions themis represents the highest spatial resolution 100 m to date of the martian surface thereby allowing small 1km impact craters to be studied in detail for the first time meteor crater serves as an analog for the many similar sized impact sites on the surface of mars these sites are future research targets with themis and aster data of meteor crater provides ideal data and geologic landscape in preparation for future themis investigations fieldwork at meteor crater yielded sample collection of the primary lithologies and an opportunity to validate previously collected high resolution 3 2 m airborne thermal imaging multispectral scanner tims data laboratory thermal emission spectra were obtained for the samples collected deconvolution of aster tir emissivity data were performed with image end members and sample end members comparisons of the spaceborne data to high resolution airborne tims data were used to assess the validity of the aster end member analyses the aster image end member analysis agreed well with the earlier tims end member analysis where the effects of resolution degradation were accounted for laboratory spectra and mineral spectral libraries provided poor fits of deconvolution of multispectral tir data lithologies with similar spectral signatures or with low areal abundances were difficult to identify using the same methodology as that applied to the aster tir data of meteor crater themis tir data of a small 1 km impact crater in syrtis major were analyzed the crater s rim and ejecta blanket was found to contain larger particle sizes than the surrounding ejecta free plain indicating a young fresh impact age and little or no accumulation of dust the composition of the rim ejecta and surrounding plain was determined to be basaltic it is hoped that the work performed here will complement future investigations of fresh impact sites with themis data that may be used to solve geologic questions such as 1 the composition of ejecta blocks that represent pre impact underlying stratigraphy in high albedo dust covered regions of mars 2 the approximate age of impact and 3 regolith dust thickness which appears to be a factor of 2

impacts of convectively coupled kelvin waves on environmental conditions for atlantic tropical cyclogenesis abstracthigh amplitude convectively coupled equatorial atmospheric kelvin waves cckws are explored over the tropical atlantic during the boreal summer 1989 2009 focus is given to the atmospheric environmental conditions that are important for tropical cyclogenesis cckws are characterized by deep westerly vertical wind shear to the east of its convectively active phase and easterly vertical wind shear to the west of it this dynamical signature increases vertical wind shear over the western tropical atlantic ahead of the convectively active phase and reduces vertical wind shear after its passage the opposite is true over the eastern tropical atlantic where the climatological vertical wind shear is easterly positive total column water vapor tcwv anomalies progress eastward with the convectively active phase of the cckw whereas negative tcwv anomalies progress eastward with the convectively suppressed phase during the passage of the convectively active phase of the cckw a zonally oriented strip o

rapid filamentation zones in intense tropical cyclones intense tropical cyclones often possess relatively little convection around their cores in radar composites this surrounding region is usually echo free or contains light stratiform precipitation while subsidence is typically quite pronounced in this region it is not the only mechanism suppressing convection another possible mechanism leading to weak echo moats is presented in this paper the basic idea is that the strain dominated flow surrounding an intense vortex core creates an unfavorable environment for sustained deep moist convection strain dominated regions of a tropical cyclone can be distinguished from rotationdominated regions by the sign of s 2 s 2 2 where s1 ux y and s2 x uy are the rates of strain and x uy is the relative vorticity within the radius of maximum tangential wind the flow tends to be rotation dominated 2 s 2 s 2 so that coherent structures such as mesovortices can survive for long periods of time outside the radius of maximum tangential wind the flow tends to be strain dominated s 2 s 2 2 resulting in filaments of anomalous vorticity in the regions of strain dominated flow the filamentation time is defined as fil 2 s 2 s 2 2 1 2 in a tropical cyclone an approximately 30 kmwide annular region can exist just outside the radius of maximum tangential wind where fil is less than 30 min and even as small as 5 min this region is defined as the rapid filamentation zone since the time scale for deep moist convective overturning is approximately 30 min deep convection can be significantly distorted and even suppressed in the rapid filamentation zone a nondivergent barotropic model illustrates the effects of rapid filamentation zones in category 1 5 hurricanes and demonstrates the evolution of such zones during binary vortex interaction and mesovortex formation from a thin annular ring of enhanced vorticity

mapping the piute mountains california with thermal infrared multispectral scanner tims images thermal infrared multispectral scanner tims data were acquired in 1990 over the piute mountains california to evaluate their usefulness for lithologic mapping in an area of metamorphosed structurally complex igneous and sedimentary rocks the data were calibrated and atmospherically corrected and emissivity variations in the form of alpha residuals were extracted from which color composite images were made there was an excellent visual correlation between the units revealed in the color composite image and the lithologic units mapped in the eastern side of the area it was also possible to correct improve and extend the recent map for example several areas mapped as granodioritic gneiss had tims alpha residual spectra consistent with mafic rocks and were subsequently mapped as amphibolite the presence of a swarm of mafic dikes of which only a few had previously been identified was also revealed the images also showed color variations in granitoid plutons that correlated with compositional variations previously determined by extensive field and geochemical work the western piute mountains is an area that has proven to be especially difficult to map with field and air photographic methods due to heterogeneous nature of certain units and various levels of desert varnish the images permitted the extremely heterogeneous proterozoic schists gneisses and granites to be easily mapped because the small scale compositional variability was averaged to the tims pixel size 12 m 12 m square areal measurements from the images show that the proterozoic rocks in the piute mountains consist of granitoids 50 biotite gneiss 15 pelitic gneiss 15 quartzite 10 and amphibolite 10 tims data can dramatically increase the efficiency and the quality of geologic mapping in well exposed heterogeneous areas with minimal vegetation cover where detailed mapping of lithologic contacts by traditional methods is unusually difficult

regression analysis of zonally narrow components of the mjo abstractrecent works have demonstrated that eastward propagating features smaller than zonal wavenumber 3 but with spatial structures similar to those of the madden julian oscillation mjo frequently develop over the indo pacific warm pool these signals are characterized by periods shorter than 4 weeks but since they occur as part of a spectral peak of the mjo they might be characterized by similar physics these zonally narrow features occur at any phase of traditionally defined 30 60 day mjo events but they occur most frequently in its active convective phase this work presents a linear regression analysis based on filtering in the wavenumber frequency domain to compare such signals with traditionally defined mjos and 15 30 m s 1 convectively coupled kelvin waves results show that the trough collocated with the easterly wind anomaly extends westward into the region of lower tropospheric westerly wind and deep convection in the zonally narrow slow signals and mjos the fast kelvin waves have a ri

a global view of martian surface compositions from mgs tes thermal emission spectrometer tes data from the mars global surveyor mgs are used to determine compositions and distributions of martian low albedo regions two surface spectral signatures are identified from low albedo regions comparisons with spectra of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass the distribution of the two compositions is split roughly along the planetary dichotomy the basaltic composition is confined to older surfaces and the more silicic composition is concentrated in the younger northern plains

african easterly wave variability and its relationship to atlantic tropical cyclone activity abstract automatic tracking of vorticity centers in european centre for medium range weather forecasts analyses has been used to develop a 20 yr climatology of african easterly wave activity the tracking statistics at 600 and 850 mb confirm the complicated easterly wave structures present over the african continent the rainy zone equatorward of 15 n is dominated by 600 mb activity and the much drier saharan region poleward of 15 n is more dominated by 850 mb activity over the atlantic ocean there is just one storm track with the 600 and 850 mb wave activity collocated based on growth decay and genesis statistics it appears that the 850 mb waves poleward of 15 n over land generally do not get involved with the equatorward storm track over the ocean instead there appears to be significant development of 850 mb activity at the west african coast in the rainy zone around 10 n 10 w which it is proposed is associated with latent heat release based on the tracking statistics it has been shown th

identification of quartzofeldspathic materials on mars 1 a unique spectral component has been identified near and on the central peaks of two 30 km diameter craters in northern syrtis major these exposures are clearly visible in thermal emission imaging system themis color radiance images as well as themis and thermal emission spectrometer tes surface emissivity data both tes and themis data indicate the presence of increased 1050 1250 cm 1 8 9 5 m absorption compared to the surrounding basaltic plains and tes data also display other absorptions at 400 470 and 800 cm 1 25 20 and 12 m consistent with the presence of quartz ratio and isolated central peak spectral unit spectra match laboratory emissivity spectra of granitoid rocks composed primarily of quartz and plagioclase feldspar deconvolution results also indicate that the surface contains quartz and feldspar in addition to a high si glass and or sheet silicate component because central peak materials are brought up from depth during the cratering event the association of the quartzofeldspathic mineralogy with the central peaks of the craters indicates that the quartz bearing material was excavated from depth the occurrence in the two adjacent craters may imply a granitoid pluton of considerable extent a plausible formation mechanism for this relatively silicic material may be similar to that of terrestrial trondhjemites which do not require plate tectonics the rarity of the exposures implies that the process that formed the granitoid composition was probably not widespread the presence of quartz bearing material on mars indicates that mechanisms that produce highly differentiated magmas have been present and extends the diversity of surface compositions identified

thermally distinct ejecta blankets from martian craters utilizing the termoskan data set of the phobos 88 mission we have recognized a new feature on mars ejecta blanket distinct in the thermal infrared edith virtually all of the more than 100 features discovered in the termoskan data are located on the plains near valles marineris ediths have a startlingly clear dependence upon terrains of hesperian age implying a spatial or temporal dependence on hesperian terrains almost no thermally distinct ejecta blankets are associated with any of the thousands of craters within the data set that occur on the older noachian units ediths also do not appear on the portions of the younger tharsis amazonian units seen in the data the hesperian terrain dependence cannot be explained by either atmospheric or impactor variations noachian and hesperian terrains must have experienced identical atmospheric and impactor conditions during hesperian times thermally distinct ejecta blankets therefore reflect target material differences and or secondary modification processes not all lobate ejecta blankets are thermally distinct but all ediths correlated with visibly discernible ejecta blankets are associated with lobate ejecta blankets the boundaries of the thermally distinct areas usually follow closely the termini of the fluidized lobate ejecta blankets even when the ejecta blankets show a high degree of sinuosity thus the thermally distinct nature of ediths must be due to the primary ejecta formation process the coupling of these thermal anomalies to morphology is unlike most sharp martian inertia variations which are decoupled from observed surface morphology some thermally distinct ejecta blankets occur near otherwise similar craters that do not have thermally distinct ejecta blankets thus wind patterns or locally available aeolian material cannot provide a single overall explanation for the observed variations we compiled a data base of 110 edith and non edith craters ranging in diameter from 4 2 km to 90 6 km there are almost no correlations within the data base other than occurrence on hesperian terrains we postulate that most of the observed ediths are due to excavation of thermally distinctive noachian age material from beneath a relatively thin layer of younger more consolidated hesperian volcanic material the plausibility of this theory is supported by much geological evidence for relatively thin near surface hesperian deposits overlying massive noachian megabreccias on the edith rich plains units we suggest that absence of thermally distinct ejecta blankets on noachian and amazonian terrains is due to absences of distinctive near surface layering thermally distinct ejecta blankets are excellent locations for future landers and remote sensing because of relatively dust free surface exposures of material excavated from depth

variations in martian surface composition and cloud occurrence determined from thermal infrared spectroscopy analysis of viking and mariner 9 data viking infrared thermal mapper irtm and mariner 9 infrared interferometer spectrometer iris data were examined for evidence of spatial variations in the composition of surface materials and the abundance of atmospheric condensates the irtm instrument collected broadband spectral radiance in bands centered at 7 9 11 and 20 m these measurements were converted to emissivities at 9 11 and 20 m and used to construct multispectral images at five seasons ls 90 180 180 360 0 90 90 180 and 180 360 and at local times of 6 8 8 10 10 12 12 14 and 14 16 h 24 h equals one martian day during dusty periods ls 180 360 these images clearly revealed the presence of suspended dust during clear periods ls 0 180 the seasonal and diurnal variations in water ice cloud occurrence could be mapped using the 11 m irtm band clouds tended to occur over the tharsis region and the region between 0 and 60 w near the equator and to evolve from dispersed hazes to more localized hazes during the day as northern summer progressed during the viking period the northern clouds transitioned from a diffuse haze to a more concentrated zone of clouds in the equatorial region with a well defined northern boundary during clear periods the irtm multispectral data reveal significant absorptions at 9 11 and 20 m that are strongly correlated with surface albedo these absorptions are produced by surface materials and individual four point spectra show compositional variations within both dark and bright material types the iris instrument collected high spectral resolution 2 4 cm 1 data from 6 to 50 m unfortunately only 85 daytime spectra out of the 21 000 total collected were acquired after the intense global dust storm of 1971 subsided after ls 330 the close agreement of these spectra convolved to irtm resolution with the irtm surface spectra confirms that they also represent surface rather than atmospheric materials the irtm four point spectra show similarities with plagioclase feldspar minerals clays and pyroxenes although the low spectral resolution of irtm prevents definitive mineral identification carbonates do not compose a significant fraction of the dark region materials the iris surface spectra show similarities with feldspars clays and pyroxenes in the 8 12 m region but do not match any of these minerals well in the 18 25 m region overall the irtm and iris data are consistent with previous suggestions of mafic to ultramafic compositions but data provide stronger evidence that unweathered plagioclase feldspars may be significant components of the present surface together the irtm and iris reveal the presence of absorption features associated with surface materials which should permit detailed surface compositional mapping using future thermal ir spectral measurements

diffusion creep dislocation creep and mantle rheology abstract viscosity depth profiles in the earth s mantle are estimated on the basis of microrheological equations for ultrabasic silicates the preliminary reference earth model prem and two assumed geotherms one with and one without a lower mantle upper thermal boundary layer the estimation includes assessment of variations of creep parameters with depth both constant strain rate non linear viscosity and newtonian viscosity are in the range 1020 1021 pa s in the upper mantle in the lower mantle there is a moderate increase in viscosity with depth and upper limit estimates are of the order of 1022 and 1023 pa s respectively as uncertainties are one order of magnitude the newtonian viscosity mantle inferred from geophysical observations cannot be rejected on the strength of rheological considerations by the same token convection should be mantle wide as the viscosity layering is not sufficient to prevent it on the other hand if the mantle is chemically stratified and separate convective circulations exist in the upper and lower mantle the thermal boundary layer below the 670 km discontinuity should have a discernible viscosity signature

age relationship of basaltic and andesitic surface compositions on mars analysis of high resolution tes observations of the northern hemisphere 1 previous mars global surveyor thermal emission spectrometer tes results have identified two principal surface compositions on mars basaltic surfaces are found primarily in the southern highlands while andesitic surfaces are found in the northern lowlands and in smaller concentrations distributed throughout the southern highlands in 1 pixel per degree composition maps the exact boundary between the basaltic and andesitic compositions is obscured by large amounts of equatorial surface dust in this work high resolution tes surface spectral data are used to identify and characterize isolated regions of basalt within the equatorial dust regions and northern lowlands generally between 20 s 60 n 0 360 w in an effort to better understand the nature of the boundary between the two compositions the purpose of refining this boundary is to more accurately determine the relationship of the compositional dichotomy with global surface morphology and derived crustal thickness results show that the basaltic surface composition is closely associated with the ancient cratered terrain morphology but is not well correlated with crustal thickness the northern extent of the tes basalt composition is also established with four exceptions there are no significant concentrations 30 surface cover of basalt greater than 400 km2 in area within the northern plains three are located within or adjacent to knobby terrain which has been suggested to be erosional remnants of the cratered highlands the fourth exception is in milankovic crater and may represent a local basalt flow or basaltic material excavated during crater formation results from this work suggest that there is a stratigraphic relationship between the basaltic and andesitic surface compositions with younger andesitic materials overlying older basaltic materials throughout the equatorial and northern plains regions

a global view of equatorial waves and tropical cyclogenesis abstractthis study investigates the number of tropical cyclone formations that can be attributed to the enhanced convection from equatorial waves within each basin tropical depression td type disturbances i e easterly waves were the primary tropical cyclone precursors over the northern hemisphere basins particularly the eastern north pacific and the atlantic in the southern hemisphere however the number of storms attributed to td type disturbances and equatorial rossby waves were roughly equivalent equatorward of 20 n tropical cyclones formed without any equatorial wave precursor most often over the eastern north pacific and least often over the western north pacific the madden julian oscillation mjo was an important tropical cyclone precursor over the north indian south indian and western north pacific basins the mjo also affected tropical cyclogenesis by modulating the amplitudes of higher frequency waves each wave type reached the attribution threshold 1 5 times more often and tropi

morphology and composition of the surface of mars mars odyssey themis results the thermal emission imaging system themis on mars odyssey has produced infrared to visible wavelength images of the martian surface that show lithologically distinct layers with variable thickness implying temporal changes in the processes or environments during or after their formation kilometer scale exposures of bedrock are observed elsewhere airfall dust completely mantles the surface over thousands of square kilometers mars has compositional variations at 100 meter scales for example an exposure of olivine rich basalt in the walls of ganges chasma thermally distinct ejecta facies occur around some craters with variations associated with crater age polar observations have identified temporal patches of water frost in the north polar cap no thermal signatures associated with endogenic heat sources have been identified

convectively coupled kelvin waves and tropical cyclogenesis in a semi lagrangian framework abstractthis study examines how convectively coupled kelvin waves interact with the semi lagrangian circulation of easterly waves to modulate tropical cyclogenesis recent studies have shown that fewer tropical cyclones form in the three days before passage of the kelvin wave s peak convection and more develop in the three days thereafter separately other studies have identified the recirculation of moisture and vorticity within easterly waves using a semi lagrangian frame of reference that framework is achieved by subtracting the easterly wave phase speed from the earth relative winds this study combines these recent findings by testing whether the equatorial westerlies from kelvin waves can help close the semi lagrangian circulation past studies have shown that kelvin waves tilt westward with height in the troposphere such that equatorial westerlies build upward from the surface in the days following the convective peak this study shows that the easterly wave s semi lagrangian closed circulation gr

dust coatings on basaltic rocks and implications for thermal infrared spectroscopy of mars 1 thin coatings of atmospherically deposited dust can mask the spectral characteristics of underlying surfaces on mars from the visible to thermal infrared wavelengths making identification of substrate and coating mineralogy difficult from lander and orbiter spectrometer data to study the spectral effects of dust coatings we acquired thermal emission and hemispherical reflectance spectra 5 25 m 2000 400 cm 1 of basaltic andesite coated with different thicknesses of air fall deposited palagonitic soils fine grained ceramic clay powders and terrestrial loess the results show that thin coatings 10 20 m reduce the spectral contrast of the rock substrate substantially consistent with previous work this contrast reduction continues linearly with increasing coating thickness until a saturation thickness is reached after which little further change is observed the saturation thickness of the spectrally flat palagonite coatings is 100 120 m whereas that for coatings with higher spectral contrast is only 50 75 m spectral differences among coated and uncoated samples correlate with measured coating thicknesses in a quadratic manner whereas correlations with estimated surface area coverage are better fit by linear functions linear mixture modeling of coated samples using the rock substrate and coating materials as end members is also consistent with their measured coating thicknesses and areal coverage a comparison of ratios of thermal emission spectrometer tes spectra of dark and bright intracrater and windstreak deposits associated with radau crater suggests that the dark windstreak material may be coated with as much as 90 areal coverage of palagonitic dust the data presented here also will help improve interpretations of upcoming mini tes and thermal emission imaging system themis observations of coated mars surface materials

global mineral distributions on mars 1 determining the mineralogy of mars is an essential part of revealing the conditions of the surface and subsurface a deconvolution method was used to remove atmospheric components and determine surface mineralogy from thermal emission spectrometer data at 1 pixel per degree ppd minerals are grouped into categories on the basis of compositional and spectral similarity and global concentration maps are produced all binned pixels are fit well with rms errors of 0 005 in emissivity higher rms errors are attributed to short wavelength particle size effects on dust covered surfaces significant concentrations 0 10 of plagioclase high ca pyroxene sheet silicates high si glass and hematite are detected and display distributions consistent with previous studies elevated concentrations of plagioclase and high ca pyroxene are consistent with basaltic surfaces and are located in low albedo highlands regions north of 45 s significant concentrations of plagioclase and sheet silicates high si glass and low concentrations of high ca pyroxenes are consistent with andesitic surfaces and are concentrated in both southern and northern high latitude low albedo regions andesitic surfaces in the southern hemisphere have a lower spectral contrast than northern surfaces an isolated surface located in solis planum is spectrally distinct but compositionally similar to other surfaces interpreted to be andesitic in composition concentrations of olivine below the detection limit correctly identify its presence in two of three locations potassium feldspar low ca pyroxene basaltic glass olivine sulfate carbonate quartz and amphibole are not detected with confidence at 1 ppd the results presented here indicate a predominance of volcanic compositions within martian dust free surfaces

experimental deformation of a synthetic dunite at high temperature and pressure i mechanical behavior optical microstructure and deformation mechanism abstract we have performed a series of 27 deformation experiments on a very dry synthetic dunite using the griggs solid medium apparatus strain rates ranged from 1 10 4 to 1 10 7 sec 1 temperatures varied from 1100 to 1300 c and the confining pressure was maintained at 10 or more usually 15 kbar macor im a commercially available anhydrous machinable glass ceramic with a low melting point was used in many of the experiments we find that strength measurements performed using macor as a confining medium are similar to results obtained using sodium chloride as the confining solid tests performed in undried sample assemblies using air dried dunite specimens resulted in creep strengths greater than those found in any earlier studies except those of post 1973 1977 a single test on a sample for which both sample and assembly were dried at a temperature sufficiently high to drive off any adsorbed water resulted in a creep strength comparable to that determined by post 1973 1977 for very dry mt burnett dunite despite our experimental difficulties we are led to believe that our synthetic dunite exhibits mechanical behavior consistent with that determined in other experimental studies in which natural dunites and peridotites were used furthermore we conclude that dry dunite is very probably as strong as the oft disputed results of post earlier indicated finally we show that the optical textures of our highly recrystallized experimental specimens are essentially identical to naturally produced porphyroclastic textures and that the deformation mechanism in both the experimental and natural specimens is probably dislocation creep with recovery by dynamic recrystallization

mesoscale features associated with tropical cyclone formations in the western north pacific abstract the mesoscale features of 124 tropical cyclone formations in the western north pacific ocean during 1999 2004 are investigated through large scale analyses satellite infrared brightness temperature tb and quick scatterometer quikscat oceanic wind data based on low level wind flow and surge direction the formation cases are classified into six synoptic patterns easterly wave ew northeasterly flow ne coexistence of northeasterly and southwesterly flow ne sw southwesterly flow sw monsoon confluence mc and monsoon shear ms then the general convection characteristics and mesoscale convective system mcs activities associated with these formation cases are studied under this classification scheme convection processes in the ew cases are distinguished from the monsoon related formations in that the convection is less deep and closer to the formation center five characteristic temporal evolutions of the deep convection are identified i single convection event ii two co

sources of tropical subseasonal skill in the cfsv2 abstractthis study applies fourier filtering to a combination of rainfall estimates from trmm and forecasts from the cfsv2 the combined data are filtered for low frequency lf 120 days variabil

analysis of hot springs and associated deposits in yellowstone national park using aster and aviris remote sensing the advanced spaceborne thermal emission and reflection radiometer aster and the airborne visible ir image spectrometer aviris data were used to characterize hot spring deposits in the lower midway and upper geyser basins of yellowstone national park from the visible near infrared vnir to thermal infrared tir wavelengths field observations of these basins provided the critical ground truth for comparison with the remote sensing results fourteen study sites were selected based on diversity in size deposit type and thermal activity field work included detailed site surveys such as land cover analysis photography global positioning system gps data collection radiometric analysis and vnir spectroscopy samples of hot spring deposits geyser deposits and soil were also collected analysis of aster data provided broad scale characteristics of the hot springs and their deposits including the identification of thermal anomalies aviris high spectral resolution short wave infrared swir spectroscopy provided the ability to detect hydrothermally altered minerals as well as a calibration for the multispectral swir aster data from the image analysis differences in these basins were identified including the extent of thermal alteration the location and abundance of alteration minerals and a comparison of active near extinct and extinct geysers we determined the activity level of each region using a combination of the vnir swir tir spectral differences as well as the presence of elevated temperatures detected by the tir subsystem of aster the results of this study are applicable to the exploration of extinct mineralized hydrothermal deposits on both earth and mars

thermal infrared spectroscopy of experimentally shocked anorthosite and pyroxenite implications for remote sensing of mars 1 the feldspar and pyroxene mineralogies on mars revealed by the thermal emission spectrometer tes on mars global surveyor likely record a variety of shock effects as suggested by petrologic analyses of the martian meteorites and the abundance of impact craters on the planet s surface to study the effects of shock pressures on thermal infrared spectra of these minerals we performed shock recovery experiments on orthopyroxenite and anorthosite samples from the stillwater complex montana over peak pressures from 17 to 63 gpa we acquired emissivity and hemispherical reflectance spectra 350 1400 cm 1 7 29 mm of both coherent chips and fine grained powders of shocked and unshocked samples these spectra are more directly comparable to remotely sensed data of mars e g tes than previously acquired absorption or transmission spectra of shocked minerals the spectra of experimentally shocked feldspar show systematic changes with increasing pressure due to depolymerization of the silica tetrahedra for the spectra of chips this includes the disappearance of small bands in the 500 650 cm 1 region and a strong band at 1115 cm 1 and changes in positions of a strong band near 940 cm 1 and the christiansen feature near 1250 cm 1 spectra of the shocked powders show the gradual disappearance of a transparency feature near 830 cm 1 fewer changes are observed in the pyroxene spectra at pressures as high as 63 gpa spectra of experimentally shocked minerals will help identify more precisely the mineralogy of rocks and soils not only from tes but also from future mars instruments such as minites and themis index terms 3944 mineral physics shock wave experiments 3934 mineral physics optical infrared and raman spectroscopy 5420 planetology solid surface planets impact phenomena includes cratering 5460 planetology solid surface planets physical properties of materials keywords anorthosite pyroxenite shock spectra thermal infrared remote sensing mars

standardizing the nomenclature of martian impact crater ejecta morphologies the mars crater morphology consortium recommends the use of a standardized nomenclature system when discussing martian impact crater ejecta morphologies the system utilizes nongenetic descriptors to identify the various ejecta morphologies seen on mars this system is designed to facilitate communication and collaboration between researchers crater morphology databases will be archived through the u s geological survey in flagstaff where a comprehensive catalog of martian crater morphologic information will be maintained

the role of convectively coupled atmospheric kelvin waves on african easterly wave activity abstractthe role of convectively coupled atmospheric kelvin waves cckws on african easterly wave aew activity is explored over tropical africa during boreal summer examination of the pre alberto aew in 2000 highlights the observation that the convective trigger for the initiation of the aew was generated by a strong cckw and that the subsequent intensification of the aew at the west african coast was associated with a second cckw composite analysis shows that generally aew activity increases during and after the passage of the convectively active phase of strong cckws the increase in aew activity is consistent with convective triggering at the leading edge of the convective phase of the cckw this convective triggering occurs in a region where the background low level easterly vertical wind shear is increased by the cckw as the aew propagates westward through the convectively active phase of the cckw it can develop in an environment favorable for convection it is also shown that this phase of

hydrolytic weakening in olivine single crystals deformation experiments on single crystals of san carlos olivine under hydrous conditions were performed to investigate the microphysical processes responsible for hydrolytic weakening during dislocation creep hydrogen was supplied to the crystals using either talc or brucite sealed in nickel capsules with the crystal deformation experiments were carried out using a gas medium apparatus at temperatures of 1050 to 1250 c a confining pressure of 300 mpa differential stresses of 45 to 294 mpa and resultant strain rates of 1 5 10 6 to 4 4 10 4 s 1 for talc buffered i e water and orthopyroxene buffered samples at high temperatures the dependence of strain rate on stress follows a power law relationship with a stress exponent n of 2 5 and an activation energy of 490 kj mol brucite buffered samples deformed faster than talc buffered samples but contained similar hydrogen concentrations demonstrating that strain rate is influenced by orthopyroxene activity under hydrous conditions the values of n and dependence of strain rate on orthopyroxene activity are consistent with hydrolytic weakening occurring in the climb controlled dislocation creep regime that is associated with deformation controlled by lattice diffusion under hydrous conditions and by pipe diffusion under anhydrous conditions analyses of postdeformation electron backscatter diffraction data demonstrate that dislocations with 100 burgers vectors are dominant in the climb controlled regime and dislocations with 001 are dominant in the glide controlled regime comparison of the experimentally determined constitutive equations demonstrates that under hydrous conditions crystals deform 1 to 2 orders of magnitude faster than under anhydrous conditions

observations of a convectively coupled kelvin wave in the eastern pacific itcz abstract a case study of a convectively coupled kelvin wave in the eastern pacific intertropical convergence zone itcz is presented as observed during the 1997 pan american climate studies pacs tropical eastern pacific process study tepps the large scale convective envelope associated with this disturbance with a zonal scale of approximately 1000 2000 km propagates eastward at 15 m s 1 along the mean convective axis of the itcz this envelope consists of many smaller scale westward moving convective elements with zonal scales on the order of 100 500 km as the convectively coupled kelvin wave disturbance propagates eastward it exerts a strong control on local convection radar and vertical profiler data collected aboard the noaa r v ronald h brown during the wave passage show that convection deepens rapidly as the kelvin wave approaches from the west progressing from isolated shallow cumuli to organized deep convective features within just 12 h initially rainfall in the vicinity of the s

thermal inertia mapping of mars from 60 s to 60 n twenty micrometer brightness temperatures are used to derive the thermal inertia for 81 of the martian surface between latitudes 60 these data were acquired by the two viking infrared thermal mappers in 1977 and 1978 following the two global dust storms of 1977 the spatial resolution used is 2 in latitude by 2 in longitude and the total range in derived inertia is 1 to 15 10 3 cal cm 2 sec 12 k 1 the distribution of thermal inertia is strongly bimodal with all values of thermal inertia less than 4 10 3 cal cm 2 sec 12 k 1 being associated with three disjoint bright regions mostly in the northern hemisphere sufficient dust is raised in global storms to provide fine material adequate to produce these low inertia areas but the specific deposition mechanism has not been defined at the low resolution used no complete exposures of clean rock were found there is some tendency for darker material to be associated with higher thermal inertia although the trend is far from one to one the distribution of high and low inertia areas is sufficiently nonrandom to produce a variation in whole disk brightness temperature with central meridian longitude this variation and the change in surface kinetic temperature associated with dust storms are factors in establishing the whole disk brightness temperature at radio and infrared wavelengths and will be important for those who use mars as a calibration source

spectroscopic study of the moses lake dune field washington determination of compositional distributions and source lithologies 1 source lithologies and transport histories of materials within the ephrata fan are investigated data were collected using a variety of remote sensing laboratory spectroscopic and field observations and techniques laboratory thermal emission spectra were collected of bedrock within the grand coulee dune samples and clast deposits factor analysis target transformation and end member recovery techniques were applied to the set of dune samples as well as a set of grain size fractions the dune sample spectra are composed of three components that represent basalt granodiorite and clay compositions the basalt and granodiorite components are similar to spectra of clast and bedrock samples from the grand coulee and the ephrata fan the clay component is similar to weathering surfaces located within the dune field the same components were recovered from the set of grain size fractions from a single dune sample demonstrating a relatively higher basalt concentration with grain sizes greater than 250 m thermal infrared multispectral scanner tims data display significant intradune compositional variation and no discernable interdune compositional variation indicating that the basalt and granodiorite components were likely deposited simultaneously and subsequently separated by wind based on grain size basalt and granodiorite bedrock units within the channeled scablands are source materials for the deposits within the ephrata fan and moses lake dune field the columbia river located 20 km west of the dune field is not a likely source of material

mapping playa evaporite minerals and associated sediments in death valley california with multispectral thermal infrared images efflorescent salt crusts and associated sediments in death valley california were studied with remote sensing data acquired by the nasa thermal infrared multispectral scanner tims nine spectral classes that represent a variety of surface materials were distinguished including several classes that reflect important aspects of the playa groundwater chemistry and hydrology evaporite crusts containing abundant thenardite sodium sulfate were mapped along the northern and eastern margins of the cottonball basin areas where the inflow waters are rich in sodium gypsum calcium sulfate crusts were more common in the badwater basin particularly near springs associated with calcic groundwaters along the western basin margin evaporite rich crusts generally marked areas where groundwater is periodically near the surface and thus able to replenish the crusts though capillary evaporation detrital silicate minerals were prevalent in other parts of the salt pan where shallow groundwater does not affect the surface composition the surface features in death valley change in response to climatic variations on several different timescales for example salt crusts on low lying mudflats form and redissolve during seasonal to interannual cycles of wetting and desiccation in contrast recent flooding and erosion of rough salt surfaces in death valley probably reflect increased regional precipitation spanning several decades remote sensing observations of playas can provide a means for monitoring changes in evaporite facies and for better understanding the associated climatic processes at present such studies are limited by the availability of suitable airborne scanner data however with the launch of the earth observing system eos am 1 platform in 1998 multispectral visible near infrared and thermal infrared remote sensing data will become globally available

ejecta distribution patterns at meteor crater arizona on the applicability of lithologic end member deconvolution for spaceborne thermal infrared data of earth and mars 1 a spectral deconvolution using a constrained least squares approach was applied to airborne thermal infrared multispectral scanner tims data of meteor crater arizona the three principal sedimentary units sampled by the impact were chosen as end members and their spectra were derived from the emissivity images to validate previous estimates of the erosion of the near rim ejecta the model was used to identify the areal extent of the reworked material the outputs of the algorithm reveal subtle mixing patterns in the ejecta identified larger ejecta blocks and were used to further constrain the volume of coconino sandstone present in the vicinity of the crater the availability of the multialtitude data set also provided a means to examine the effects of resolution degradation and quantify the subsequent errors on the model these data served as a test case for the use of image derived lithologic end members at various scales which is critical for examining thermal infrared data of planetary surfaces the model results indicate that the coconino ss reworked ejecta is detectable over 3 km from the crater this was confirmed by field sampling within the primary ejecta field and wind streak the areal distribution patterns of this unit imply past erosion and subsequent sediment transport that was low to moderate compared with early studies and therefore places further constraints on the ejecta degradation of meteor crater it also provides an important example of the analysis that can be performed on thermal infrared data currently being returned from earth orbit and expected from mars in 2002

the mjo kelvin wave transition 1 as the madden julian oscillation mjo moves eastward from the indian to the pacific ocean it typically accelerates becomes less strongly coupled to convection and becomes more similar to a dry kelvin wave this transition is analyzed using observations of outgoing longwave radiation and era interim reanalyses of surface pressure and 850 hpa zonal wind two individual example events as well as composites are shown the transitions are well defined with distinct disturbances on either side of the transition whose identities as mjo or kelvin waves are clear in some cases there appears to be a pre existing kelvin wave passing through the mjo from the west to the east but this feature is not apparent in the composites the transitions occur at different longitudes in different events over a wide range from the eastern indian to the central pacific oceans

on the possibility of newtonian flow in the upper mantle abstract the possibility of a linear creep newtonian viscosity upper mantle is reexamined on the basis of present knowledge on flow mechanisms in olivine including differences between activation parameters for creep and for diffusion and revised estimates of grain boundary width results of the comparison between linear superplastic creep and power law creep are presented as crossover temperature between lattice and grain boundary diffusion and crossover stress between non linear and linear creep as a function of temperature depth grain size grain boundary width grain boundary diffusion activation energy and rate controlling species silicon or oxygen for the most realistic values of the parameters linear creep is well within the range of possibilities there is no major objection from rheology to the idea of a newtonian viscosity upper mantle viscosities for the two kinds of creep are compared for laboratory upper mantle and tentatively lower mantle conditions this results in a prediction of the grain size at which coble creep could be observed in olivine polycrystals in the laboratory 10 m or less the upper mantle viscosity is in the 1020 1021 pa s range minimum estimates for the viscosity of the lower mantle are of the same order the pictures of the rheology of the mantle derived from microphysical models of flow and from geophysical observation can therefore be made compatible

tropical cyclogenesis associated with kelvin waves and the madden julian oscillation abstractthe madden julian oscillation mjo influences tropical cyclone formation around the globe convectively coupled kelvin waves are often embedded within the mjo but their role in tropical cyclogenesis remains uncertain this case study identifies the influences of the mjo and a series of kelvin waves on the formation of two tropical cyclones typhoons rammasun and chataan developed in the western north pacific on 28 june 2002 two weeks earlier conditions had been unfavorable for tropical cyclogenesis because of uniform trade easterlies and a lack of organized convection the easterlies gave way to equatorial westerlies as the convective envelope of the madden julian oscillation moved into the region a series of three kelvin waves modulated the development of the westerlies cyclonic potential vorticity pv developed in a strip between the growing equatorial westerlies and the persistent trade easterlies farther poleward rammasun and chataan emerged from the apparent breakdown of this strip the

crater gradation in gusev crater and meridiani planum mars 1 the mars exploration rovers investigated numerous craters in gusev crater and meridiani planum during the first 400 sols of their missions craters vary in size and preservation state but are mostly due to secondary impacts at gusev and primary impacts at meridiani craters at both locations are modified primarily by eolian erosion and infilling and lack evidence for modification by aqueous processes effects of gradation on crater form are dependent on size local lithology slopes and availability of mobile sediments at gusev impacts into basaltic rubble create shallow craters and ejecta composed of resistant rocks ejecta initially experience eolian stripping which becomes weathering limited as lags develop on ejecta surfaces and sediments are trapped within craters subsequent eolian gradation depends on the slow production of fines by weathering and impacts and is accompanied by minor mass wasting at meridiani the sulfate rich bedrock is more susceptible to eolian erosion and exposed crater rims walls and ejecta are eroded while lower interiors and low relief surfaces are increasingly infilled and buried by mostly basaltic sediments eolian processes outpace early mass wasting often produce meters of erosion and mantle some surfaces some small craters were likely completely eroded buried craters 100 m in diameter on the hesperian aged floor of gusev are generally more pristine than on the amazonian aged meridiani plains this conclusion contradicts interpretations from orbital views which do not readily distinguish crater gradation state at meridiani and reveal apparently subdued crater forms at gusev that may suggest more gradation than has occurred

large scale influences on tropical cyclogenesis in the western north pacific abstract objectively analyzed data from the european centre for medium range weather forecasts are used to examine the large scale aspects of the formation of tropical cyclones it is hypothesized that tropical cyclogenesis occurs when external atmospheric forcing on the synoptic or larger scale provides uplift through a deep layer enhancing convection in a region with environmental conditions favorable for genesis emphasis is placed on the roles of upper level troughs low level wind surges preexisting tropical cyclones and propagating wave disturbances in triggering tropical cyclogenesis composites of the 200 hpa and 850 hpa flows reveal the presence of both upper level troughs and low level wind surges respectively prior to genesis in the composites the wind surges also appear to be related to the presence of a prior circulation located approximately 2000 km to the west of the genesis location an examination of the individual cases demonstrates that approximately 85 of all storms had either

characteristics of tropical easterly wave pouches during tropical cyclone formation abstractthe pregenesis evolution of wave pouches was examined for 164 named tropical cyclones that originated from zonally propagating tropical easterly waves over the atlantic during july october 1989 2010 using the european centre for medium range weather forecasts ecmwf interim re analysis era interim and the climate prediction center cpc morphing technique cmorph precipitation east of 60 w most wave pouches 80 form at 700 hpa first often extending down to 850 or 925 hpa off the coast of west africa by contrast the majority of the wave pouches 68 over the west atlantic west of 60 w form at 850 or 925 hpa first wave pouches become more vertically aligned approaching genesis it was also found that vorticity at 925 hpa intensifies faster than that at 600 hpa a warm core structure forms at the meso scale near the pouch center prior to genesis but is less well defined at the meso pouch scale the evolution of precipitation and the low level convergence suggests that convection

regional dust deposits on mars physical properties age and history major dust storms on mars play an important role in the deposition and removal of fine dust material thermal radar and visual remote sensing observations provide important constraints on the martian regolith which have been used to determine the location and physical properties of regional dust deposits these deposits are located in three northern equatorial regions tharsis 20 s to 50 n 60 to 190 w arabia 5 s to 30 n 300 to 360 w and elysium 10 to 30 n 210 to 225 w they are covered by fine 2 40 m bright albedo 0 27 particles with fewer exposed rocks and coarse deposits than found elsewhere dust is currently deposited uniformly throughout the equatorial region at a rate of 40 m global storm over geologic time the rate of accumulation may vary from 0 to 250 m yr due to changes in atmospheric conditions produced by orbital variations dust deposited during global storms is subsequently removed only from dark regions resulting in a net accumulation in the low inertia bright regions the thickness of these current dust deposits is 0 1 2 m the thermal inertia places a lower limit of 0 1 m on the thickness of these deposits while the sparse but ubiquitous presence of exposed rocks and the degree of visible mantling indicate that the thickness is less than 5 m dual polarization radar observations of a very rough texture in tharsis are consistent with this model with a 2 m thick dust layer burying most of the surface rocks but permitting radar sampling of the rough subsurface based on their thickness and rate of accumulation the age of these deposits is 105 106 years suggesting a cyclic process of deposition and removal one possible cause may be cyclic variations in the magnitude and location of maximum wind velocities related to variations in mars orbit at present perihelion and maximum wind velocities occur in the south whereas regional dust deposits occur in the north suggesting net transport from south to north orbital parameters oscillate with periods ranging from 5 104 to 106 years the agreement between these periods and the dust deposit age suggests a possible link at different stages in orbit evolution maximum wind velocities will occur in the north with subsequent erosion and redistribution of the accumulated fines based on this model much of the uppermost martian surface is very young and is being continually reworked

estimating silicic lava vesicularity with thermal remote sensing a new technique for volcanic mapping and monitoring remote monitoring of active lava domes pro vides insights into the duration of continued lava extru sion and detection of potentially associated explosive activity on inactive flows variations in surface texture ranging from dense glass to highly vesicular pumice can be related to emplacement time volatile content and internal structure pumiceous surface textures also pro duce changes in thermal emission spectra that are clear ly distinguishable using remote sensing spectrally the textures describe a continuum consisting of two pure end members obsidian and vesicles the distinct spec tral features of obsidian are commonly muted in pu mice due to overprinting by the vesicles which mimic spectrally neutral blackbody emitters assuming that this energy combines linearly in direct proportion to the percentage of vesicles the surface vesicularity can be estimated by modeling the pumice spectrum as a lin ear combination of the glass and blackbody spectra based on this discovery a linear retrieval model using a least squares fitting approach was applied to airborne thermal infrared data of the little glass mountain and crater glass rhyolite flows at medicine lake volcano california as a case study the model produced a ve sicularity image of the flow with values from 0 to f70 which can be grouped into three broad textural classes dense obsidian finely vesicular pumice and coarsely vesicular pumice values extracted from the image compare well with those derived from sem anal ysis of collected samples as well as with previously re ported results this technique provides the means to accurately map the areal distributions of these textures resulting in significantly different values from those de rived using aerial photographs if applied to actively deforming domes this technique will provide volcano logists with an opportunity to monitor dome wide de gassing and eruptive potential in near real time in july 1999 such an effort will be possible for the first time when repetitive global multispectral thermal infrared data become available with the launch of the advanced spaceborne thermal emission and reflectance ra diometer aster instrument aboard the earth ob serving system satellite

mixed rossby gravity waves and western pacific tropical cyclogenesis part i synoptic evolution abstract a large amplitude mixed rossby gravity wave packet is identified in the western pacific using 6 10 day bandpass filtered winds individual disturbances of 2300 3000 km wavelength propagated westward as the packet moved slowly eastward the packet first appeared and subsequently amplified within a region of active convection associated with the madden julian oscillation mjo which was isolated by low pass filtered outgoing longwave radiation the packet lasted about 5 weeks then rapidly dispersed as the active mjo moved away from it to the east west of 150 e individual disturbances within the packet turned northwestward away from the equator indicating an apparent transition from mixed rossby gravity waves to off equatorial tropical depression td type disturbances cyclones filled with cloud and anticyclones cleared during the transition nevertheless convective structure consistent with mixed rossby gravity waves remained outside the circulation centers and three tropical cyclones for

convectively coupled kelvin waves over tropical africa during the boreal summer structure and variability the structure and variability of convectively coupled kelvin waves during the boreal summer are explored using satellite observed brightness temperature data and ecmwf reanalyses kelvin wave activity is most prominent between the central and eastern pacific across africa and the indian ocean composite analysis shows that over sub saharan africa kelvin wave convection is peaked north of the equator while the dynamical fields tend to be symmetric with respect to the equator convectively coupled kelvin waves propagate faster over the pacific and western atlantic 24 m s 1 and slow down over tropical africa 14 m s 1 consistent with stronger coupling between the dynamics and convection over tropical africa the kelvin waves observed over africa generally propagate into the region from anywhere between the eastern pacific and the atlantic and decay over the eastern indian ocean basin results show marked interannual variability of kelvin wave activity over africa anomalously high kelvin wave variance tends to occur during dry years while low variance occurs during wet years african kelvin wave activity is positively correlated with sst anomalies in the equatorial east pacific the same warm sst anomalies that are favorable for enhanced kelvin wave activity suppress the mean rainfall over tropical africa via a more slowly varying teleconnection and associated subsidence a brief analysis of an intense kelvin wave in august 1987 a dry year shows a clear impact of the wave on convective development and daily rainfall over tropical africa this kelvin wave was also associated with a series of easterly wave initiations over tropical africa

a climatology of waves in the equatorial region abstract propagating anomalies of moisture and moist deep convection in the tropics are organized into a variety of large scale modes these include but are not limited to the so called intraseasonal oscillations convectively coupled waves similar to those predicted by shallow water theory on the equatorial beta plane and tropical depression type disturbances along with the annual and diurnal cycles these modes act and interact to control much of the variance of tropical convection analyses of 10 yr of outgoing longwave radiation olr and precipitable water pw data are carried out to develop comparative climatologies of these wavelike modes the analysis relaxes the commonly used cross equatorial symmetry constraints which allows study of the portions of the wavelike processes that are asymmetric across the equator mean background states are found for olr and for pw as functions of day of the year examination of anomalies together with the background reveals much about how the waves are affec

the subsurface character of meteor crater arizona as determined by ground probing radar ground probing radar has provided new two dimensional stratigraphic and structural information on meteor crater arizona four 50 mhz transects inside the crater and one 100 mhz transect on a northeast radial across the exterior ejecta blanket were carried out the frequencies used were in relation to the desired depth of investigation greater than 50 m at 50 mhz and 30 m for 100 mhz the results obtained inside the crater show that the water table can be clearly detected at depths of 65 m as can the contact between the crater wall and the infilling allochthonous breccia lens in addition we were able to detect 1 point reflectors from relatively coherent blocks 1 5m within the breccia lens 2 a zone 7 m thick relatively free of point reflectors from the immediate fall back unit 3 a series of subhorizontal reflectors a few meters apart due to bedding in the post impact crater sediments and 4 five separate subhorizontal reflectors from what we interpret to be a series of postimpact paleo water table levels in the breccia lens the ejecta blanket transect indicates a 4 10 m thick ejecta layer and the underlying moenkopi formation sandstone as well as the moenkopi kaibab contact and bedding within the kaibab formation in addition reverse faults with displacements up to 4 m were detected in the bedrock as well as changes from subhorizontal to 30 in the dip of the bedrock as the crater rim is approached from the northeast beneath the ejecta blanket the total uplift observed at the crater rim is around 55 m the radar data indicate uplift effects out to a radial distance of 400 m from the rim farther than that determined from drilling 300 m the results demonstrate the utility of continuous ground probing radar cross sections in studying the near subsurface 50 m character at meteor crater this relatively rapid low cost technique can be extended to other structures but confident interpretation requires supplemental ground truth constraints

water enhanced dynamic recrystallization and solution transfer in experimentally deformed carnallite cylindrical samples of polycrystalline carnallite kmgcl3 6h2o were deformed in a triaxial apparatus at 60 c at confining pressures between 0 1 and 31 mpa and at strain rates between 10 4 and 10 8 s 1 in a number of cases small amounts of saturated carnallite brine were added samples without added brine deform by intracrystalline slip mechanical twinning cracking and by frictional sliding on crack surfaces stress strain curves of these samples are strongly dependent on confining pressure addition of brine has a dramatic effect on both microstructural development and mechanical properties grain boundary migration is strongly enhanced at lower strain rates additional intracrystalline effects start to appear together with the onset of solution transfer rapid compaction in samples deformed with added brine causes high fluid pressures to develop at higher strain rates addition of brine results in a decrease of the flow stress by a factor of two this weakening will increase even further at strain rates below about 10 9 s 1 when solution transfer becomes rate controlling it is argued that deformation of carnallite in nature is adequately described by the flow law found for samples deformed with added brine

rheology of the lithosphere selected topics we review recent results concerning the rheology of the lithosphere with special attention to the following topics 1 the flexure of the oceanic lithosphere 2 deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins 3 the rheological stratification of the continents 4 strain localization and shear zone development and 5 strain induced crystallographic preferred orientations and anisotropies in body wave velocities we conclude with a section citing the 1983 1986 rock mechanics literature by category

emissivity of terrestrial materials in the 3 5 μm atmospheric window remotely sensed infrared radiance emitted by a surface is a function both of its kinetic temperature and its spectral emissivity consequently assumptions are usually made about the emissivity of earth surface materials to allow their temperatures to be determined or vice versa to increase the accuracy of these assumptions the directional hemispherical spectral reflectance of a wide range of natural earth surface materials has been measured and is summarized here these include igneous metamorphic and sedimentary rocks desert varnish soils vegetation water and ice kirchhoff s law can be used to predict directional spectral emissivity from these data

comment on the effect of pressure on the rate of dislocation recovery in olivine by d l kohlstedt h p k nichols and paul hornack

rock mechanics observations pertinent to the rheology of the continental lithosphere and the localization of strain along shear zones emphasized in this paper are the deformation processes and rheologies of rocks at high temperatures and high effective pressures conditions that are presumably appropriate to the lower crust and upper mantle in continental collision zones much recent progress has been made in understanding the flexure of the oceanic lithosphere using rock mechanics based yield criteria for the inelastic deformations at the top and base at mid plate depths stresses are likely to be supported elastically because bending strains and elastic stresses are low the collisional tectonic regime however is far more complex because very large permanent strains are sustained at mid plate depths and this requires us to include the broad transition between brittle and ductile flow moreover important changes in the ductile flow mechanisms occur at the intermediate temperatures found at mid plate depths two specific contributions of laboratory rock rheology research are considered in this paper first the high temperature steady state flow mechanisms and rheology of mafic and ultramafic rocks are reviewed with special emphasis on olivine and crystalline rocks rock strength decreases very markedly with increases in temperature and it is the onset of flow by high temperature ductile mechanisms that defines the base of the lithosphere the thickness of the continental lithosphere can therefore be defined by the depth to a particular isotherm tc above which at geologic strain rates the high temperature ductile strength falls below some arbitrary strength isobar e g 100 mpa for olivine tc is about 700 800 c but for other crustal silicates tc may be as low as 400 600 c suggesting that substantial decoupling may take place within thick continental crust and that strength may increase with depth at the moho as suggested by a number of workers on independent grounds put another way the moho is a rheological discontinuity a second class of laboratory observations pertains to the general phenomenon of ductile faulting in which ductile strains are localized into shear zones ductile faults have been produced in experiments of five different rock types and is generally expressed as strain softening in constant strain rate tests or as an accelerating creep rate stage at constant differential stress a number of physical mechanisms have been identified that may be responsible for ductile faulting including the onset of dynamic recrystallization phase changes hydrothermal alteration and hydrolytic weakening microscopic evidence for these processes as well as larger scale geological and geophysical observations suggest that ductile faulting in the middle to lower crust and upper mantle may greatly influence the distribution and magnitudes of differential stresses and the style of deformation in the overlying upper continental lithosphere

thermal infrared 2 5 13 5 μm spectroscopic remote sensing of igneous rock types on particulate planetary surfaces fundamental molecular vibration bands are significantly diminished by scattering thus such bands in spectra of fine particulate regoliths i e dominated by 5 m particles or regoliths displaying a similar scale of porosity are difficult to use for mineralogical or rock type identification consequently other spectral features have been sought that may be more useful in spectroscopic remote sensing of composition we find that mineralogical information is retained in overtones and combination tones of the fundamental molecular vibrations in the 3 0 to 7 0 m region but that relatively few minerals have a sufficiently distinctive band structure to be unambiguously identified with currently available techniques more significantly identification of general rock type as defined by the scfm chemical index scfm sio2 sio2 cao feo mgo is possible using spectral features associated with the principal christiansen frequency and with a region of relative transparency between the si o stretching and bending bands however environmental factors may affect the appearance and wavelengths of these features finally prominent absorption bands may result from the presence of relatively small amounts of water hydroxyl or carbonate because absorption bands exhibited by these materials in the 2 7 to 4 0 m region where silicate spectra are otherwise featureless increase strongly in spectral contrast with decreasing particle size such materials are thus detectable in very small amounts in a particulate regolith composed predominantly of silicate minerals

rheology and deformation mechanisms of an isotropic mica schist we have investigated the transitional semibrittle deformation of a mica schist 75 biotite by shortening cylinders cored at 0 45 and 90 to foliation to varying strains at confining pressures pc to 500 mpa constant strain rates e from 1 5 10 7 to 1 6 10 4 s 1 and temperatures t from 25 to 400 c deformation is concentrated within one or more throughgoing millimeter wide shear zones at all conditions these localize at low strains e 2 through the nucleation and coalescence of dense sets of intragranular microkink bands mkbs despite distinct differences in the relative number of mica grains oriented favorably for slip and kinking in different loading directions the differential stresses required for shear zone development vary little with fabric orientation biotite schist undergoes a transition from strain softening to steady strength mechanical response at confining pressures in the range 75 to 150 mpa the pressure sensitivity of strength characterized by the slope of the mohr envelope decreases from 0 5 at pc 100 mpa to 0 1 at pressures greater than 200 mpa reflecting the increasing contribution of glide and kinking in biotite at higher pressures however dilatancy associated with microcracking and void formation along mkb boundaries persists to at least 500 mpa within the pressure insensitive regime 200 pc 500 mpa temperature and strain rate dependencies of strength determined in stepping tests reveal a strong history dependence to flow that cannot strictly be described by a steady state constitutive law samples deformed in steps from low to high temperatures or fast to slow strain rates consistently exhibit stronger temperature and strain rate sensitivities than those deformed along t decreasing or e increasing paths path dependent effects may reflect differences in the degree to which inherited dislocation substructures are utilized or overprinted during later deformation increments by assuming an exponential relationship between differential stress d and strain rate e of the form e c exp d exp q rt we fit the data with two end member flow laws with a single activation energy q 89 kj mol and exponential constants ss 0 15 0 01 mpa 1 and ws 0 55 0 04 mpa 1 that account for the different responses observed along stepping paths that are strongly sensitive or weakly sensitive to t and e respectively application of the results to crustal deformation suggests that mica rich aggregates are weaker than other common rock types throughout a broad midcrustal depth range supporting the inference that retrograde reaction to phyllosilicates may be important in localizing crustal deformations within large faults and shear zones

attributing tropical cyclogenesis to equatorial waves in the western north pacific abstract tropical cyclogenesis is attributed to an equatorial wave when the filtered rainfall anomaly exceeds a threshold value at the genesis location it is argued that 0 mm day 1 simply requiring a positive anomaly is too small a threshold because unrelated noise can produce a positive anomaly a threshold of 6 mm day 1 is too large because two thirds of storms would have no precursor disturbance between these extremes consistent results are found for a range of thresholds from 2 to 4 mm day 1 roughly twice as many tropical cyclones are attributed to tropical depression td type disturbances as to equatorial rossby waves mixed rossby gravity waves or kelvin waves the influence of the madden julian oscillation mjo is even smaller the use of variables such as vorticity and vertical wind shear in other studies gives a larger contribution for the mjo it is suggested that its direct influence on the rainfall in forming tropical cyclones is less than for other variables the impacts of tropical

quantitative compositional analysis using thermal emission spectroscopy application to igneous and metamorphic rocks the mineral composition of a suite of igneous and metamorphic rocks was determined using the thermal infrared emission spectra of these rocks in a linear spectral deconvolution algorithm this algorithm assumes that the infrared spectrum of each rock is a linear mixture of the component mineral spectra weighted by volume abundance a diverse suite of 36 common rock forming and accessory minerals was used in the deconvolution the model was tested by comparing the mineralogy derived from the infrared spectrum with petrographically estimated abundances for 45 igneous and 51 metamorphic rock samples the mineral abundances derived from these two techniques agree to within 67 15 for the primary minerals feldspar pyroxene quartz and calcite dolomite and 69 17 for secondary minerals such as micas and amphiboles these differences are comparable to the error for traditional thin section mode estimates which are 65 15 for major minerals and 5 for minor minerals the detection limit for the primary and secondary minerals found in the rocks analyzed ranged from 5 to 10 each major rock type studied here was easily distinguished by its spectral characteristics the best results in both the qualitative determination of the rock type and dominant minerals and the quantitative reproduction of absorption features and mineral composition were obtained for igneous rock samples for metamorphic rocks pelite and quartzo feldspathic samples gave slightly better results than calcareous or mafic samples a controlled analysis in which the end member suite was reduced based on an initial estimate of the rock type only improved the results by several percent for most primary and secondary minerals the quality of the obtained results demonstrates that a linear deconvolution of infrared emission spectra provides an accurate rapid technique for determining the quantitative mineral composition of rock samples in a laboratory and has application to future in situ measurements

genesis of pre hurricane felix 2007 part i the role of the easterly wave critical layer abstract the formation of pre hurricane felix 2007 in a tropical easterly wave is examined in a two part study using the weather research and forecasting wrf model with a high resolution nested grid configuration that permits the representation of cloud system processes the simulation commences during the wave stage of the precursor african easterly wave disturbance here the simulated and observed developments are compared while in part ii of the study various large scale analyses physical parameterizations and initialization times are explored to document model sensitivities in this first part the authors focus on the wave vortex morphology its interaction with the adjacent intertropical convergence zone complex and the vorticity balance in the neighborhood of the developing storm analysis of the model simulation points to a bottom up development process within the wave critical layer and supports the three new hypotheses of tropical cyclone formation proposed recently by dunkerton montgome

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

flow mechanisms in sulphide minerals abstract the sulphide minerals as a group display a diverse range in strength and mechanical behaviour in crustal environments deforming by a range of different flow mechanisms which can lead to the development of characteristic microfabrics the dependence of creep rate on imposed parameters such as stress difference temperature grainsize effective confining pressure and the activities of various components varies for each type of flow mechanism for particular phases changes in the dominant operative flow mechanism may occur in response to changes in the imposed environmental variables at high applied stress differences low effective confining pressures and low temperatures brittle failure and cataclastic flow are significant deformation mechanisms in some sulphide minerals at elevated confining pressures brittle failure can be suppressed and low temperature plasticity processes involving dislocation glide and or deformation twinning may operate with decreasing applied stress difference and at elevated temperatures even though strain may be accommodated largely by dislocation glide deformation may be rate controlled by recovery processes and dynamic recrystallization may be significant in influencing microfabric development the operation of dislocation glide processes leads to the development of crystallographic preferred orientations at very low applied stress difference various grainsize dependent atomic transfer deformation mechanisms may be important in many fluid present low to medium grade metamorphic environments solution precipitation creep processes are active in the deformation of some sulphide phases in fluid absent situations grain boundary diffusion creep may be significant at higher temperatures where intragranular diffusion is relatively rapid lattice diffusion creep processes are expected to be a major deformation mechanism in fine grained sulphide assemblages at elevated temperatures grain boundary sliding may be an important deformation mechanism

eolian intracrater deposits on mars physical properties and global distribution abstract an investigation of martian intracrater materials has been made using their thermophysical properties as derived from viking irtm observations over one fourth of all craters larger than 25 km in diameter between 50 s and 50 n have localized deposits of coarse material on the floor which are associated with dark splotches seen visually assuming homogeneous unconsolidated materials the measured thermal inertias of these deposits i 0 003 10 3 to 0 026 10 3 cal cm 2 sec 1 2 k 1 imply effective grain sizes ranging from 0 1 mm to 1 cm with a modal value of 0 9 mm these deposits are coarser and darker than the surrounding terrains and the majority of the martian surface but are not compositionally distinct from materials with similar albedos they occur more frequently in the south in regions of relatively coarse material 0 2 to 2 mm and in relatively dark areas these features most likely formed by entrapment of marginally mobile material which can be transported into but not out of crater depressions by the wind very few have recognizable dune forms those that do have effective grain sizes less than 0 5 mm the majority of the splotch deposits are coarser than the dune forming materials found in the north polar region and inside extreme southern latitude craters and probably form low broad zibar dunes or lag deposits intracrater deposits are noticeably lacking from the interior of the large northern hemisphere low inertia region of arabia 10 s to 30 n 300 to 360 w interpreted to be a sink for suspended dust but do occur around the perimeter of this region this distribution suggests that the intracrater features have been buried in the interior of arabia and that the dust deposit is less extensive at the margins and may currently be expanding the occurrence of regional dust deposits in the north may be related to the maximum wind activity currently occurring in the southern hemisphere and suggests that the location of regional sinks may migrate with time as the solar insolation maximum migrates

age and geomorphic history of meteor crater arizona from cosmogenic 36cl and 14c in rock varnish abstract using cosmogenic 36 cl buildup and rock varnish radiocarbon we have measured the exposure age of rock surfaces at meteor crater arizona our 36 cl measurements on four dolomite boulders ejected from the crater by the impact yield a mean age of 49 7 0 85 ka which is in excellent agreement with an average age of 49 3 ka obtained from thermoluminescence studies on shock metamorphosed dolomite and quartz these ages are supported by undetectably low 14 c in the oldest rock varnish sample

atlantic tropical systems of 1993 abstract a total of 70 tropical waves also known as african or easterly waves were counted in the atlantic basin during the 1993 hurricane season these waves led to the formation of 9 of the 10 total number of tropical cyclones in the atlantic hurricane basin it appears that tropical waves led to the formation of practically all of the eastern pacific tropical cyclones in 1993

mapping alluvial fans in death valley california using multichannel thermal infrared images we have mapped alluvial fans in death valley california using nasa s 8 12 m six channel airborne thermal infrared multispectral scanner tims we are able to recognize both composition and relative age differences age unit boundaries are generally consistent with those obtained by conventional mapping composition was verified by field investigation and comparison with existing geologic maps bedrock and its young derived fan gravels have similar emissivities the original composition of the fans is modified by differential erosion and weathering permitting relative age mapping with tims

effect of varying enstatite content on the deformation behavior of fine grained synthetic peridotite under wet conditions the effect of varying enstatite content on the deformation behavior of synthetic fine grained 1 to 2 m forsterite enstatite rock with 0 5 wt added water was investigated at temperatures of 900 to 1000 c strain rates between 10 7 and 10 5 s 1 and a confining pressure of 600 mpa the samples exhibited approached steady state flow at stresses 60 mpa the results show that at constant strain rate increasing enstatite content is associated with a sharp decrease in flow strength in the range 0 2 5 vol enstatite with little further change up to 20 vol the observed power law n value of 1 7 and microstructures are similar to those obtained in previous work on material with 2 5 wt enstatite and are consistent with a water enhanced grain boundary sliding gbs dominated deformation mechanism significantly a negative correlation was found between grain size and enstatite content indicating that enstatite content played a role in controlling the grain size of the starting materials moreover a high correlation between measured flow strength and grain size was found consistent with a grain size exponent of 3 in a conventional grain size sensitive flow equation a water enhanced deformation mechanism involving gbs accommodated probably by grain boundary diffusion and or dislocation activity is therefore implied with the effect of enstatite content on flow strength being an indirect physical effect caused by grain size control other effects of second phase content such as weakening caused by interphase boundary diffusion and or migration processes seem to be unimportant under the conditions investigated

atlantic tropical cyclogenesis a three way interaction between an african easterly wave diurnally varying convection and a convectively coupled atmospheric kelvin wave abstractthis paper explores a three way interaction between an african easterly wave aew the diurnal cycle of convection over the guinea highlands ghs and a convectively coupled atmospheric equatorial kelvin wave cckw these interactions resulted in the genesis of tropical storm debby over the eastern tropical atlantic during late august 2006 the diurnal cycle of convection downstream of the ghs during the month of august is explored convection associated with the coherent diurnal cycle is observed off the coast of west africa during the morning later convection initiates over and downstream of the ghs during the afternoon these convective features were pronounced during the passage of the pre debby aew the superposition between the convectively active phase of a strong cckw and the pre debby aew occurred shortly after merging with the diurnally varying convection downstream of the ghs the cckw aew interaction preceded tropical cyclogenesis by 18 h the cckw provided a favorable environment

the surface of syrtis major composition of the volcanic substrate and mixing with altered dust and soil syrtis major is an old low relief volcanic plateau near the equatorial regions of mars it is a persistent low albedo feature on the planet and is thought to contain a high abundance of exposed bedrock and or locally derived surface material and debris spatially resolved variations in surface spectral properties and therefore composition are investigated with data from the imaging spectrometer for mars ism instrument ism obtained 128 wavelength channel spectra from 0 76 to 3 16 m for contiguous pixels approximately 22 22 km in size across much of the plateau the value and spatial distribution of four primary spectral variables albedo continuum slope wavelength of the ferric ferrous band minimum area of the ferric ferrous absorption are mapped and coregistered to viking digital photomosaics analysis of these maps shows that although there is a high degree of overall spectral variability on the plateau the key indicators of mafic mineralogy are relatively homogeneous detailed examination of reflectance spectra from representative areas across the plateau indicate the volcanic surface is dominated by augite bearing basalts and the pyroxene composition in the basalts is estimated to be 0 275 0 075 ca ca fe mg and 0 3 0 1 fe fe ca mg additional mineral components may include olivine feldspar and glass most of the spectral variability on the plateau is interpreted to result from mixing of volcanic bedrock and or locally derived surface material and debris with highly altered dust and soil in western syrtis major the altered material is a transient component on the surface or occurs in large spatially coherent patches e g crater rims in eastern syrtis major it is apparent that the dust components are firmly fixed to the basaltic substrate as a stable oxide rind or coating

kelvin waves and tropical cyclogenesis a global survey abstractconvectively coupled atmospheric kelvin waves are among the most prominent sources of synoptic scale rainfall variability in the tropics but large uncertainties surround their role in tropical cyclogenesis this study identifies the modulation of tropical cyclones relative to the passage of a kelvin wave s peak rainfall i e its crest in each basin tropical cyclogenesis is generally inhibited for 3 days before the crest and enhanced for 3 days afterward composites of storms forming in the most favorable lags illustrate the dynamical impacts of the waves in most basins the tropical cyclone actually forms during the convectively suppressed phase of the wave the 850 hpa equatorial westerly anomalies provide the cyclonic vorticity for the nascent storm and 200 hpa easterly anomalies enhance the outflow the wind anomalies persist at both levels longer than the kelvin wave s period and are often related to the madden julian oscillation mjo the onset of these wind anomalies occurs with the

petrographic studies of the impact melts from meteor crater arizona usa we investigated the ballistically dispersed melts from meteor crater arizona usa to determine the stratigraphic extent of its melt zone from the compositional relationship of melts and target rocks most melt particles are crystallized hydrated and oxidized pristine glasses are rare hydration and oxidation occurred at ambient temperatures long after the impact the preserved glasses are generally clear and texturally homogeneous but unlike typical impact melts they have unusually heterogeneous compositions both within individual particles and from sample to sample for example the average sio2 for individual particles ranges from 43 to 65 the projectile content is unusually high and it is distributed bimodally with specific samples containing either 5 10 or 20 30 feo these compositional heterogeneities most likely reflect the high carbonate content of the target rocks and the release of copious co2 that dispersed the melts thereby terminating melt flow and mixing the high projectile content and the co2 depleted residue of purely sedimentary rocks produced mafic melts that crystallized fine grained olivine and pyroxene the melts fall into three compositional groups reflecting variable proportions of the major target formations moenkopi kaibab and coconino least square mixing calculations revealed one group to contain 55 moenkopi 40 quartz rich upper kaibab and 5 meteorite suggesting a source depth of 90 m or 30 m respectively additional studies especially hydrocode calculations are needed to better understand the source depth of these melts and their exceptionally high projectile content

constraints on the mechanism of deformation of olivine imposed by defect chemistry abstract more is known about diffusion electrical conductivity and creep in forsterite and olivine than any other mineral this paper examines these data to see what constraints are placed on the mechanisms of deformation in these minerals experimental observations show a creep rate for forsterite independent of the activity of oxygen a o 2 in olivine the creep rate is proportional to a 1 6 o 2 and in addition is ten times faster for the enstatite excess situation than for the magnesiowustite excess situation these data are consistent with positively charged kinks being the rate controlling species in olivine the data for forsterite are also compatible with a kink controlled mechanism although some other jog and diffusion controlled mechanisms remain as possibilities the activation energy for creep is not related to that for diffusion of silicon or oxygen for kink controlled mechanisms the activation energy is approximately given by the sum of the fermi level and the activation energy for charged kink migration minus the ionization energy of the kink the fermi level can be changed by minor changes in impurities and by changes in the imposed thermodynamic environment so unless these parameters are controlled during deformation variations in observed activation energies for creep are to be expected from one set of experiments to another

determining the modal mineralogy of mafic and ultramafic igneous rocks using thermal emission spectroscopy the modal mineralogies of 20 mafic and ultramafic igneous rocks were determined from their thermal infrared emission spectra using a linear deconvolution approach which uses a library of end member mineral spectra to model a bulk rock spectrum over 90 of the modes obtained from thermal emission spectra agree with modes obtained by traditional optical analyses to within the stated error of the optical analyses 5 15 vol library spectra of several compositions within a solid solution series e g plagioclase feldspars labradorite and bytownite were commonly used in each best fit model and are assumed to represent in combination a composition in the rock for which an identical mineral spectrum was unavailable in the library the accuracy of this assumption was evaluated by calculating a weighted average solid solution composition for plagioclase and or pyroxenes from the library minerals used in the model best fit of 14 rocks and comparing these compositions to the actual chemistries measured by electron microprobe or the optically estimated an the derived solid solution compositions are generally within 10 15 an or mg of the measured composition modal data derived from the spectra via the deconvolution were summed and converted to weight percent wt oxides for comparison to standard bulk chemistry data sio2 al2o3 and na2o k2o were generally slightly overestimated and feo and mgo were typically slightly underestimated modes and wt oxides were plotted on standard rock type classification diagrams and provide broadly accurate classifications demonstrating that the linear deconvolution technique is successful at deriving useful mineralogical information from thermal infrared emission spectra of bulk rock samples furthermore convolution of the laboratory data to spectral resolutions comparable to remote sensing instruments specifically the mars global surveyor thermal emission spectrometer demonstrates only a 5 vol increase in modal uncertainty for minerals present in abundances 10 vol this study thus provides a strong foundation for the application of this technique to mafic igneous sample spectra from both laboratory and remote sensing instruments

in situ10be 26al exposure ages at meteor crater arizona a new method of dating the surface exposure of rocks from in situ production of 10be and 26al has been applied to determine the age of meteor crater arizona a lower bound on the crater age of 49 200 1 700 years has been obtained by this method

the role of tropical waves in tropical cyclogenesis abstract this paper analyzes relationships between tropical wave activity and tropical cyclogenesis in all of the earth s major tropical cyclone basins twenty nine years of outgoing longwave radiation data and global reanalysis winds are filtered and analyzed to determine statistical relationships between wave activity in each basin and the corresponding cyclogenesis composite analyses relative to the storm genesis locations show the structures of the waves and their preferred phase relationships with genesis five wave types are examined in this study including mixed rossby gravity waves tropical depression type or easterly waves equatorial rossby waves kelvin waves and the madden julian oscillation the latter is not one of the classical tropical wave types but is a wavelike phenomenon known to have a strong impact on tropical cyclogenesis tropical cyclone formation is strongly related to enhanced activity in all of the wave filter bands except for the kelvin band in each basin the structure o

projection of tropical cyclones on wavenumber frequency filtered equatorial waves theimpactoflocalizedconvectionassociatedwithtropicalcyclones tcs onactivityascribedtoequatorial waves is estimated an algorithm is used to remove outgoing longwave radiation olr signal in the vicinity of observed tropical cyclones and equatorial wave modes are extracted using the standard wavenumber frequency decomposition method the results suggest that climatological activity of convection coupled equatorial waves is overestimated where tc tracks are densest the greatest impact is found for equatorial rossby er and tropical depression td type waves followed by the madden julian oscillation mjo the basins most affected are the eastern and western north pacific ocean where on average tcs may contribute up to 10 15 of the climatological wave amplitude variance in these modes in contrast kelvin waves are least impacted by the projection of tcs the results are likely relevant for studies on the climatology of equatorial waves in observations and global climate model simulations and for those examining individual cases of tc genesis modulated by equatorial wave activity