merging the minnaert k parameter with spectral unmixing to map forest heterogeneity with chris proba data the compact high resolution imaging spectrometer chris mounted onboard the project for onboard autonomy proba spacecraft is capable of sampling reflected radiation at five viewing angles over the visible and near infrared regions of the solar spectrum with high spatial resolution we combined the spectral domain with the angular domain of chris data in order to map the surface heterogeneity of an alpine coniferous forest during winter in the spectral domain linear spectral unmixing of the nadir image resulted in a canopy cover map in the angular domain pixelwise inversion of the rahman pinty verstraete rpv model at a single wavelength at the red edge 722 nm yielded a map of the minnaert k parameter that provided information on surface heterogeneity at a subpixel scale however the interpretation of the minnaert k parameter is not always straightforward because fully vegetated targets typically produce the same type of reflectance anisotropy as non vegetated targets merging both maps resulted in a forest cover heterogeneity map which contains more detailed information on canopy heterogeneity at the chris subpixel scale than is possible to realize from a single source optical data set

statistical patterns of high latitude convection obtained from goose bay hf radar observations we have derived patterns that describe the statistical interplanetary magnetic field imf dependencies of ionospheric convection in the high latitude region of the northern hemisphere the observations of plasma motion were made with the hf coherent backscatter radar located at goose bay labrador over the period september 1987 to june 1993 the area covered by the measurements extended poleward of 65 to a working limit of about 85 distributions of electrostatic potential have been derived and expressed as series expansions in spherical harmonics the patterns are the first derived from direct ground based observations of ionospheric convection that approach in completeness and level of detail the patterns derived in recent satellite studies rich and hairston 1994 weimer 1995 we show the dependence of the convection on imf angle in the gsm y z plane for three intervals of imf magnitude in this plane except for predominantly northward imf the convection is primarily two cell the dusk cell is larger in terms of both spatial extent and potential variation the effect of imf by is apparent in the global shaping of the cells and the orientation of the overall pattern in mlt for by by the dusk dawn cell is more round crescent shaped and the pattern more rotated toward earlier mlts the by effect on the nightside convection is pronounced and is hemispherically antisymmetric like the well known day side by effect for imf increasingly northward the convection trajectories on the dayside become increasingly distorted evolving through a three cell to a four cell circulation the additional cells appear on either side of the noon meridian and result in sunward flow the overall agreement with the results of the satellite studies is good and extends to quite fine detail in the case of the comparison with weimer 1995 there are significant differences with the statistical patterns derived from magnetometer measurements which tend to show domination by the dawn rather than the dusk cell

why is the bay of bengal less productive during summer monsoon compared to the arabian sea 1 the bay of bengal is traditionally considered to be a less productive basin compared to the arabian sea we explore the reasons for this in the central bay during summer copious rainfall and river water freshen the upper layers of the bay by 3 7 psu during summer and sst was warmer by 1 5 2 c than in the central arabian sea this leads to a strongly stratified surface layer the weaker winds over the bay are unable to erode the strongly stratified surface layer thereby restricting the turbulent wind driven vertical mixing to a shallow depth of 20 m this inhibits introduction of nutrients from below situated close to the mixed layer bottom into the upper layers while advection of nutrients rich water into the euphotic zone makes the arabian sea highly productive this process is unlikely in the bay of bengal

large scale imaging of high latitude convection with super dual auroral radar network hf radar observations the hf radars of the super dual auroral radar network superdarn provide measurements of the e b drift of ionospheric plasma over extended regions of the high latitude ionosphere with the recent augmentation of the northern hemisphere component to six radars a sizable fraction of the entire convection zone approximately one third can be imaged nearly instantaneously 2 min to date the two dimensional convection velocity has been mapped by combining line of sight velocity measurements obtained from pairs of radars within common volume areas we describe a new method of deriving large scale convection maps based on all the available velocity data the measurements are used to determine a solution for the distribution of electrostatic potential expressed as a series expansion in spherical harmonics the addition of data from a statistical model constrains the solution in regions of no data coverage for low order expansions the results provide a gross characterization of the global convection we discuss the processing of the radar velocity data the factors that condition the fitting and the reliability of the results we present examples of imaging that demonstrate the response of the global convection to variations in the interplanetary magnetic field imf in the case of a sudden polarity change from northward to southward imf the convection is seen to reconfigure globally on very short 6 min timescales

weekly observations on dispersal and sink pathways of the terrigenous flux of the ganga brahmaputra in the bay of bengal during ne monsoon the analyses of 64 sequential satellite images october 1999 march 2001 of indian remote sensing satellite irs p4 ocean color monitor ocm bands around 490 555 and 670 nm for total suspended matter tsm synchronous sea truth data acquisition and salinity variations have been used to construct dispersal pathways of the surficial fluvial flux into the northern bay of bengal during the ne monsoon from the spatial extent of the plumes of tsm 160 120 km during october of 1999 and2000 off the mouth of the himalayan rivers the ganga andthe brahmaputra g b it is deduced that fluvial flux does not diminish concurrently with the termination of the southwest sw monsoon as suggestedby time series trap experiments in the northern bay during the ne monsoon the g b plumes move north to south initially off the mouth and thereafter advects sw alongshore in the form of coastal sediment plumes reducing the salinity of the coastal waters along the entire northern bay during october december we have observed a strong relation between enhanced episodic discharges of the ganga brahmaputra g b and augmented coastal turbidity during weekly events it is also observed that even during such short weekly events of very high pulse of tsm discharge by the g b system the fluvial fluxes do not advect offshore into the deeper regions of the northcentral bay but are transportedalongshore andd istributedalong the shelf our results therefore suggest that the reduced recovery of the fluxes in the sediments traps subsequent to the sw monsoon are not linearly related to the magnitude of fluvial flux of the g b but stems from the prevalent dispersal patterns r 2005 elsevier ltd all rights reserved

identification of the temperature gradient instability as the source of decameter scale ionospheric irregularities on plasmapause field lines 1 recent observations with the new mid latitude superdarn hf radar located at wallops island virginia have identified a class of ionospheric irregularities that is prevalent in the nightside sub auroral ionosphere under low to moderate kp conditions these irregularities can be observed for many hours and generally exhibit very low doppler velocities a recent collaborative experiment using the wallops radar and the millstone hill incoherent scatter radar has determined that these irregularities are located at the ionospheric footprint of the plasmapause and in a region of opposed electron density and electron temperature gradients we conclude that the irregularities are produced by the temperature gradient instability tgi or by turbulent cascade from primary irregularity structures produced from this instability this is the first experimental confirmation that the tgi is effective in producing decameter scale ionospheric irregularities

a three dimensional model based approach to the estimation of the tree top height by fusing low density lidar data and very high resolution optical images light detection and ranging lidar technology has been extensively used for estimating forest attributes although high spatial density lidar data can be used to accurately derive attributes at single tree level low density lidar data are usually acquired for reducing the cost however a low density strongly affects the estimation accuracy due to the underestimation of the tree top and the possible loss of crowns that are not hit by any lidar point in this paper we propose a 3 d model based approach to the estimation of the tree top height based on the fusion between low density lidar data and high resolution optical images in the proposed approach the integration of the two remotely sensed data sources is first exploited to accurately detect and delineate the single tree crowns then the lidar vertical measures are associated to those crowns hit by at least one lidar point and used together with the radius of the crown and the tree apex location derived from the optical image for reconstructing the tree top height by a properly defined parametric model for the remaining crowns detected only in the optical image we reconstruct the tree top height by proposing a k nearest neighbor trees technique that estimates the height of the missed trees as the average of the k reconstructed height values of the trees having most similar crown properties the proposed technique has been tested on a coniferous forest located in the italian alps the experimental results confirmed the effectiveness of the proposed method

first in situ measurements of hf radar echoing targets 1 the sounding rocket investigation of cusp irregularities 2 ici 2 was launched into the cusp ionosphere over svalbard to investigate the production of decameter scale irregularities in the electron plasma associated with hf radar backscatter the main mission objective was to obtain high resolution measurements of decameter scale electron plasma irregularities and to quantify the growth rate for the gradient drift instability gdi at the 5 7 khz sampling rate of the absolute density measurements ici 2 has provided the first documentation in terms of absolute electron density measurements of how 10 m structures are located on km scale electron density gradients ici 2 traversed a cusp electron density structure created by ongoing soft precipitation 10 m scale irregularities were generated at km scale density gradients the estimated growth time for the gdi process was 10 50 seconds

a numerical investigation of the phytoplankton bloom in the bay of bengal during northeast monsoon 1 a 4 5 layer model of the indian ocean coupled to a four component npzd ecosystem model is used to study the phytoplankton bloom in the bay of bengal during the northeast monsoon of 1996 the model realistically simulates the surface chlorophyll bloom observed by satellite derived ocean color images in the western bay of bengal during that time it also reproduces the subsurface chlorophyll maximum present earlier in the fall the terms in the phytoplankton equation for the model s mixed layer show that the surface bloom is caused by the entrainment not only of subsurface nutrients but also of phytoplankton from the subsurface maximum to our knowledge this study is the first to report enrichment of surface chlorophyll by entrainment of the subsurface maximum upwelling caused by ekman pumping and mixed layer entrainment occurring over an already shallow thermocline drives the vertical fluxes an intense wind event from 26 november to 5 december also generated favorable conditions for the formation of a phytoplankton bloom

on the eastward shift of winter surface chlorophyll a bloom peak in the bay of bengal analysis of satellite derived surface layer phytoplankton chlorophyll a concentration chl a in the bay of bengal revealed an eastward shift of peak of chl a bloom during northeast monsoon period november march from western to the eastern bay the winter chl a bloom in the western bay is shorter duration 1 2 months while that in the eastern bay is longer duration 3 4 months unlike other oceans the eastward bloom peak shift found in the bay of bengal is opposite to the direction of propagation of rossby wave and seasonal mean zonal currents during winter sufficient light is available in the bay of bengal for phytoplankton growth herein we studied the processes controlling the eastward winter bloom peak shift and the zonal depiction of bloom duration in the bay of bengal there is no single dominant process that drives the eastward bloom peak shift everywhere in the bay of bengal rather different physical processes operate in different regions the physical mechanisms governing the eastward winter chl a bloom peak shift reported here include open ocean ekman pumping coastal upwelling upwelling driven by rossby wave wind induced vertical mixing nutrients supply from river input and westward advection through prevailing zonal currents

observation of polar cap patches and calculation of gradient drift instability growth times a swarm case study the swarm mission represents a strong new tool to survey polar cap patches and plasma structuring inside the polar cap in the early commissioning phase the three swarm satellites were operated in

coefficients for sea surface wind stress heat flux and wind profiles as a function of wind speed and temperature surface layer coefficients for wind profiles wind stress and heat flux in typical open sea conditions are briefly reviewed businger dyer flux gradient relationships and a charnock wind stress formula fit the empirical data and are dimensionally consistent these have been solved by an iterative method and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data

lidar based geometric reconstruction of boreal type forest stands at single tree level for forest and wildland fire management vegetation structure is an important parameter in fire risk assessment and fire behavior modeling we present a new approach deriving the structure of the upper canopy by segmenting single trees from small footprint lidar data and deducing their geometric properties the accuracy of the lidar data is evaluated using six geometric reference targets with the standard deviation of the lidar returns on the targets being as low as 0 06 m the segmentation is carried out by using cluster analysis on the lidar raw data in all three coordinate dimensions from the segmented clusters tree position tree height and crown diameter are derived and compared with field measurements a robust linear regression of 917 tree height measurements yields a slope of 0 96 with an offset of 1 m and the adjusted r 2 resulting at 0 92 however crown diameter is not well matched by the field measurements with r 2 being as low as 0 2 which is most certainly due to random errors in the field measurements finally a geometric reconstruction of the forest scene using a paraboloid model is carried out using values of tree position tree height crown diameter and crown base height

physical and biological mechanisms for planetary waves observed in satellite derived chlorophyll we examine the evidence for global propagation of planetary wavelike features in sea surface chlorophyll over much of the midlatitude ocean westward propagating signals are seen that travel at the same speed as that predicted for long planetary waves we then test three mechanisms for production of this signal these are horizontal passive north south advection by the wave against a mean background gradient vertical upwelling of nitrate which is converted into chlorophyll and vertical upwelling of chlorophyll itself the tests involve comparisons of the amplitude and phase of the predicted signal with observations the horizontal advective process predicts an amplitude for chlorophyll fluctuations that is in fair agreement with the data though both overestimating and underestimating in places the predictions for the phase difference between the chlorophyll and sea surface height signatures are in good agreement with the data the upwelling biological mechanism could potentially give a large signal in the chlorophyll field but the predicted amplitude patterns and the predicted phase difference which is everywhere negative are not in accord with the observations except in a few regions the amplitude predicted by upwelling of chlorophyll is small compared with the horizontal advection mechanism we conclude that over most of the ocean the chlorophyll signal is well explained by horizontal advective processes although we cannot rule out that there exist locations where additional biological mechanisms may be responsible for at least part of the signal

floodplain roughness parameterization using airborne laser scanning and spectral remote sensing abstract floodplain roughness parameterization is one of the key elements of hydrodynamic modeling of river flow which is directly linked to exceedance levels of the embankments of lowland fluvial areas the present way of roughness mapping is based on manually delineated floodplain vegetation types schematized as cylindrical elements of which the height m and the vertical density the projected plant area in the direction of the flow per unit volume m 1 have to be assigned using a lookup table this paper presents a novel method of automated roughness parameterization it delivers a spatially distributed roughness parameterization in an entire floodplain by fusion of casi multispectral data with airborne laser scanning als data the method consists of three stages 1 pre processing of the raw data 2 image segmentation of the fused data set and classification into the dominant land cover classes khat 0 78 3 determination of hydrodynamic roughness characteristics for each land cover class separately in stage three a lookup table provides numerical values that enable roughness calculation for the classes water sand paved area meadows and built up area for forest and herbaceous vegetation als data enable spatially detailed analysis of vegetation height and density the hydrodynamic vegetation density of forest is mapped using a calibrated regression model herbaceous vegetation cover is further subdivided in single trees and non woody vegetation single trees were delineated using a novel iterative cluster merging method and their height is predicted r 2 0 41 rse 0 84 m the vegetation density of single trees was determined in an identical way as for forest vegetation height and density of non woody herbaceous vegetation were also determined using calibrated regression models a 2d hydrodynamic model was applied with the results of this novel method and compared with a traditional roughness parameterization approach the modeling results showed that the new method is well able to provide accurate output data the new method provides a faster repeatable and more accurate way of obtaining floodplain roughness which enables regular updating of river flow models

super dual auroral radar network observations of convection during a period of small magnitude northward imf observations of the high latitude northern hemisphere convection pattern are presented for varying small magnitude interplanetary magnetic field imf conditions a new data analysis technique is used which makes use of all available data from the superdarn network rather than only using data from the regions of overlap of radar fields of view using this technique the area over which convection is determined is often greatly extended from the region of overlap the imf during this period was small magnitude b 4 nt during one interval imf b z was northward while b y was nearly zero convection during this interval evolved to a pattern with a large dusk cell with flow across the noon meridian from dusk toward dawn in a later interval imf b z and b y were both nearly zero during this interval convection evolved to a four cell pattern comparison of the observations with conceptual models showed significant differences for both intervals during the first interval statistical models and the observations compared favorably during the second interval however the observations showed a significantly different pattern from the first interval while statistical models predict the same pattern for both intervals the behavior of the convection pattern can be in part ascribed to the role played by b x which was the dominant imf component throughout this interval

interhemispheric study of polar cap patch occurrence based on swarm in situ data the swarm satellites offer an unprecedented opportunity for improving our knowledge about polar cap patches which are regarded as the main space weather issue in the polar caps we present a new robust algorithm that automatically detects polar cap patches using in situ plasma density data from swarm for both hemispheres we compute the spatial and seasonal distributions of the patches identified separately by swarm a and swarm b between december 2013 and august 2016 we show a clear seasonal dependency of patch occurrence in the northern hemisphere nh patches are essentially a winter phenomenon as their occurrence rate is enhanced during local winter and very low during local summer although not as pronounced as in the nh the same pattern is seen for the southern hemisphere sh furthermore the rate of polar cap patch detection is generally higher in the sh than in the nh especially on the dayside at about 77 magnetic latitude additionally we show that in the nh the number of patches is higher in the postnoon and prenoon sectors for interplanetary magnetic field imf by 0 respectively and that this trend is mirrored in the sh consistent with the ionospheric flow convection overall our results confirm previous studies in the nh shed more light regarding the sh and provide further insight into polar cap patch climatology along with this algorithm we provide a large data set of patches automatically detected with in situ measurements which opens new horizons in studies of polar cap phenomena

an internal crown geometric model for conifer species classification with high density lidar data the knowledge of the tree species is a crucial information that governs the success of precision forest management practice high density small footprint multireturn airborne light detection and ranging lidar scanning can collect a huge amount of point samples containing structural details of the forest vertical profile which can reveal important structural information of the forest components lidar data have been successfully used to distinguish between coniferous and deciduous broadleaved tree species however species classification within a class e g the conifer class using lidar data is a challenging problem when considering the tree external crown characteristics only this paper presents a novel method for conifer species classification based on the use of geometric features describing both the internal and external structures of the crown the internal crown geometric features igfs are defined based on a novel internal branch structure model which uses 3 d region growing and principal component analysis to delineate the branch structure of a conifer tree accurately igfs are used together with external crown geometric features to perform conifer species classification three different support vector machines have been considered for classification performance evaluation the experimental analysis conducted on high density lidar data acquired over a portion of the trentino region in italy proves the effectiveness of the proposed method