Development of daily spatial heat unit mapping from monthly climatic surfaces for the Australian continent

In absence of other limitations, the growth rate of a plant is dependent upon the amount of heat it receives. Each species, whether a crop, weed or disease organism, is adapted to grow at its optimum rate within a specific temperature range. Within this range, the growing degree days (GDD) is the heat accumulation above a given base temperature for a specific time period, such as a crop's growing season or phenological stage. In this paper we detail a methodology to predict GDD for synthetically generated average growing seasons derived from long term average climate data over the Australian continent. An application of these techniques has been made using the GEODATA 9 second DEM, with temperature threshold values estimated to characterize optimum growth in citrus (Citrus sinensis (L.) Osbeck). Three major determinants of the annual growth cycle of Citrus sp. were established and predicted on a spatial basis including the starting day of the growing season, the GDD for a growing season, and the time required to accumulate an arbitrarily selected 2000 GDD from the estimated starting day. When these critical environmental factors are expressed on a spatial basis, covering the Australian continent, the combination can be used to identify locations where new crop varieties can most effectively be grown to maximize fruit quality and productivity, or to extend the harvest season. Likewise, new germplasm introduced to Australia from overseas can be horticulturally assessed at sites climatically matched to the source location.     

Knowing our own history? Geography department archives in the UK

The paper presents an analysis of the returns to a questionnaire survey on the state of department archives within UK departments of geography. The results of the survey are discussed in relation to recent work in geography which has examined the archive as a site for knowledge's making but seldom in its own terms as a resource for the history of geography, and studies within the archival sciences which have considered the archive as something more than a 'storehouse' for collective memory. The paper reveals that the archival record for the history of British geography is at best uneven, and in many departments non-existent, although information on departmental history is held, often as memory, by individual geographers. The paper considers the survey's implications for the future histories of British geography and addresses the nature of the UK geography department archive as resource and responsibility.     

The climatic and physiographic controls of the eastern Mediterranean over the late Pleistocene climates in the southern Levant and its neighboring deserts

Modern-day synoptic-scale eastern Mediterranean climatology provides a useful context to synthesize the diverse late Pleistocene (60–12 ka) paleohydrologic and paleoenvironmental indicators of past climatic conditions in the Levant and the deserts to its south and east. We first critically evaluate, extract, and summarize paleoenvironmental and paleohydrologic records. Then, we propose a framework of eastern Mediterranean atmospheric circulation features interacting with the morphology and location of the southeast Mediterranean coast. Together they strongly control the spatial distribution of rainfall and wind pattern. This cyclone–physiography interaction enforces the observed rainfall patterns by hampering rainfall generation south and southeast of the latitude of the north Sinai coast, currently at 31°15′.The proposed framework explains the much-increased rains in Lebanon and northern Israel and Jordan as deduced from pollen, rise and maintenance of Lake Lisan, and speleothem formation in areas currently arid and semiarid. The proposed framework also accounts for the southward and eastward transition into semiarid, arid, and hyperarid deserts as expressed in thick loess accumulation at the deserts' margins, dune migration from west to east in the Sinai and the western Negev, and the formation of hyperarid (< 80 mm yr^− 1) gypsic–salic soils in the southern Negev and Sinai. Our climatic synthesis explains the hyperarid condition in the southern Negev, located only 200–250 km south of the much-increased rains in the north, probably reflecting a steeper rainfall gradient than the present-day gradient from the wetter Levant into its bordering southern and eastern deserts.At present, the rainiest winter seasons in Lebanon and northern and central Israel are associated with more frequent (+ 20%), deeper Cyprus Lows traversing the eastern Mediterranean at approximately the latitude of southern Turkey. Even these wettest years in northern Israel do not yield above average annual rainfall amounts in the hyperarid southern Negev. This region is mainly influenced by the Active Red Sea Troughs that produce only localized rains. The eastern Mediterranean Cyprus Lows also produce more dust storms and transport higher amounts of suspended dust to the loess area than any other atmospheric pattern. Concurrent rainfall and dust are essential to the late Pleistocene formation of the elongated thick loess zone along the desert northern margin. Even with existing dust storms, the lack of rain and very sparse vegetation account for the absence of late Pleistocene loess sequences from the southern Negev and the formation of hyperarid soils.When the north Sinai coast shifted 30–70 km northwest due to last glacial global sea level lowering, the newly exposed coastal areas supplied the sand and dust to these active eastern Mediterranean cyclones. This enforced the latitude of the northern boundary of the loess zone to be directly due east of the LGM shoreline. This shift of coast to the northwest inhibited rainfall in the southern Levant deserts and maintained their hyperaridity. Concurrently, frequent deep eastern Mediterranean Cyprus Lows were funneled along the northern Mediterranean increasing (probably doubling) the rains in central and northern Israel, Lebanon, southwestern Syria and northern Jordan. These storms and rains formed lakes, forests, and speleothems only a short distance north of the deserts in the southern Levant.     

Sediment remobilisation from decomposing cordgrass (Spartina anglica) patches on a wave‐exposed intertidal flat

Abstract

Concerns about the potential adverse effects of Spartina invasion on New Zealand estuaries, such as habitat loss and degradation, have led to herbicide use to control its spread. An experiment was conducted in the Manukau Harbour (New Zealand) to determine sediment remobilisation rates (?E) from herbicide‐treated S. anglica patches. Paired treatment and control patches (≤25 m diam.) were monitored at two sites 500 m apart with different wave exposures. Above‐ (AGB) and below‐ground (BGB) biomass decomposition and AE were determined from repeat surveys over c. 2.5 years. Work done by waves (W), which integrates wave‐energy dissipation at the bed over time, was used as a surrogate measure of sediment transport potential. Complete AGB loss occurred in both treated patches within 3 months of initial herbicide application, whereas BGB (a matrix of roots and rhizomes) persisted much longer. An exponential decay model (r ² = 0.6) fitted to the site‐two treatment data predicted an c. 85% reduction in BGB after 5 years, whereas the BGB changes for the larger and more heterogeneous site‐one treatment were more complex. BGB was a better predictor of average bed elevation than AGB in multiple regression models and, although bed elevation decreased through time and with waves, BGB was positively related to bed elevation at both sites. AE was similar for both treatment patches (c. 0.05 and c. 0.06 m yr^‐1, P < 0.001, r² ≥ 0.97) and complete sediment loss was predicted to occur within 6–10 years. The site‐one control patch accumulated sediment (0.01 m yr^‐1 , P < 0.001, r ² = 0.81) whereas the more wave‐exposed site‐two control eroded (0.01 m yr^‐1, P = 0.0017, r ² = 0.61). The potential for adverse sediment effects resulting from Spartina control at wave‐exposed sites will be minimal if the treated areas are small relative to the size of the estuary.     

Mid-Mountain Clouds at Whistler During the Vancouver 2010 Winter Olympics and Paralympics

A comprehensive study of mid-mountain clouds and their impacts on the Vancouver 2010 Winter Olympics and Paralympics is presented. Mid-mountain clouds were frequently present on the Whistler alpine venue, as identified in an extensive archive of webcam images over a 45-day period from February 5 to March 21, 2010. These clouds posed serious forecast challenges and had significant impacts on some Olympic and Paralympic alpine skiing competitions. Under fair weather conditions, a diurnal upslope (anabatic) flow can work in concert with a diurnal temperature inversion aloft to produce a localized phenomenon known as “Harvey’s Cloud” at Whistler. Two detailed case studies in this paper suggest that mid-mountain clouds can also develop in the area as a result of a moist valley flow interacting with a downslope flow descending from the mountaintop. A southerly inflow through the Sea-to-Sky corridor can be channeled by the local topography into a westerly upslope flow toward Whistler Mountain, resulting in orographic clouds on the alpine venue. Under favorable circumstances, these clouds are trapped to the mid-mountain zone by the leeward subsidence of an elevated southerly flow. The presence of the downslope subsidence was manifested by a distinguished dry layer observed on the top of the mid-mountain clouds in both cases. It is the subsidence-induced adiabatic warming that imposes a strong buoyant suppression to trap the mid-mountain cloud. On the other hand, the subsidence-induced dry layer has the potential to trigger evaporative instability to periodically breakup the mid-mountain cloud.     

Performance evaluation of active wireline heave compensation systems in marine well logging environments

The basic functionality and performance of a new Schlumberger active wireline heave compensation system on the JOIDES Resolution was evaluated during the sea trial and a 3-year period of the IODP Phase II operations. A suite of software programs was developed to enable real-time monitoring of the dynamics of logging tools, and assess the efficiency of wireline heave compensation during downhole operations. The evaluation of the system effectiveness was performed under normal logging conditions as well as during stationary tests. Logging data were analyzed for their overall quality and repeatability, and to assess the reliability of high-resolution data such as formation microscanner (FMS) electrical images. This revealed that the system reduces 65–80 % of displacement or 88–98 % variance of downhole tool motion in stationary mode under heave conditions of ±0.2–1.5 m and water depths of 300–4,500 m in open holes. Under similar water/heave conditions, the compensator system reduces tool displacement by 50–60 %, or 75–84 % variance in downhole tool motion during normal logging operations. Such compensation efficiency (CE) is comparable to previous compensation systems, but using advanced and upgradeable technologies, and provides 50–85 % heave motion and heave variance attenuation. Moreover, logging down/up at low speeds (300–600 m/h) reduces the system’s CE values by 15–20 %, and logging down at higher speeds (1,000–1,200 m/h) eliminates CE values by 55–65 %. Considering the high quality of the logging data collected, it is concluded that the new system can provide an improved level of compensation over previous systems. Also, if practically feasible, future integration of downhole cable dynamics as an input feedback into the current system could further improve its compensation efficiency during logging operations.     

Sediment supply: The main driver of shelf-margin growth

Despite the obvious importance of sediment supply to shelf-margin architecture and to the potential of margins to contain and bypass deep-water sands, the role of supply in shelf-margin growth has received limited attention. High cross-shelf sediment flux is critically important for the occurrence of deep-water sands, not least on Greenhouse or rapidly subsiding margins where the impact of eustatic sea-level fall may be insufficient to drive sediment delivery out across the shelf into deep-water areas. To draw greater attention to the supply parameter we review a number of shelf margins that have grown chiefly through supply by shelf-edge deltas and associated sediment-gravity flows. Based on structural style and water depth, we recognize two broad types of shelf-margin. Moderately deep-water margins produce clinoforms < 1000 m high and show rates of shelf-edge progradation < 60 km/My and aggradation < 270 m/My, and consequently, infill their basins relatively rapidly, and develop more progradational architectures with morphologically smooth and relatively undeformed slopes. Very deep-water margins produce clinoforms > 1000 m high and generally show rates of shelf-edge progradation < 40 km/My and aggradation < 2500 m/My, and therefore infill their basins more slowly and develop more aggradational architectures with much gravity-driven slope deformation, proneness to failure and ponded architectures (salt or shale driven). On both margin types, long-term (> 1 My) rates of shelf-edge progradation of several tens of km/My tend to be linked to the delivery of relatively large volumes of sand into the deep-water basin. Delivery of this sand beyond the shelf-edge happens despite Greenhouse conditions and is likely recurrent and periodic (delivery cycles in the order of 100′s ky). Such prominent margin growth is a strong indication that sediment influx was relatively high and we refer to these margins as “supply-dominated” shelf margins. The Gulf of Mexico margin is a well-known and data-rich example of a “supply-dominated” shelf-margin during certain times (e.g., Paleocene). In contrast, on both margin types, low rates of shelf-edge progradation are linked to diminished (or even non-existent) and less frequently recurrent deep-water sediment delivery suggestive of relatively low sediment influx. Occurrence of deep-water sand delivery under low sediment influx probably requires fall of relative sea level. The differences between rapidly and slowly prograding margins indicate that sediment supply (and not sea level) is likely to be the key limiting factor on the growth of shelf margins and that sediment supply, as interpreted through progradation rate, can therefore be used to make a first-order prediction of relative amounts of sand passed to deep-water areas.     

Geology, failure conditions, and implications of seismogenic avalanches of the 1944 eruption at Vesuvius, Italy

Widespread avalanching occurred at Mt. Vesuvius during its 1944 eruption, the latest activity of this volcano. The 1944 avalanche deposits display many of the morphological and structural features shown by common slides of the slump-earth flow variety, including levees, transverse ridge-and-trough topography, and preserved stratigraphy. The longest avalanche travelled 1.3 km, with an estimated volume of slightly more than one million cubic meters. Avalanches came to rest on moderately-inclined slopes. Internal structure includes low- and high-angle shears and tensional fractures. Deposits are poorly consolidated. Two lithologic types are observed; avalanches composed of both blocks and ash, with blocky rubble forming a capping layer, and avalanches composed almost wholly of ash. Block-and-ash avalanches were triggered where slopes of loose tephra had been preloaded with lava flows. Ash avalanches formed where heavy accumulations of ash were deposited by prevailing winds. Seismic activity accompanying eruption served as a trigger for avalanching.     

On the behaviour of fluorine and chlorine during magmatic differentiation

The behaviour of fluorine and chlorine during differentiation is considered in the light of halogen data for granites and separated biotites from the Dartmoor granite pluton of S.W. England, hornblende-bearing ultrabasic and basic rocks from a layered intrusion at Rhiw, N. Wales, and recent literature data on halogens in apatites from the Shonkin Sag laccolith and the Skaergaard intrusion.The data indicate that whereas fluorine concentrations are highest in the late stage differentiates, chlorine concentration is highest in the earlier differentiates. It is suggested that this behaviour of the two halogens is due to their relative affinities for silicate melts. Chlorine having a low solubility in silicate melts and a strong affinity for associated aqueous phases will tend to be concentrated in early formed hydrous minerals, leaving fluorine with its strong affinity for the melt to be enriched in the late-formed hydrous minerals.     

Structural analysis of soil microrelief in palaeosols of the Lower Jurassic “Laterite Derivative Facies” (Mishhor and Ardon formations) Makhtesh Ramon,Israel

A sequence of palaeosols developed on exposed overbank sediments of successive alluvial cycles of the Lower Jurassic “Laterite Derivative Facies” (LDF) at Makhtesh Ramon, contains well-developed, penecontemporaneous soil microrelief structures. The folded structures commonly show overthrusting, and vary in wave length and amplitude.They are characterized by slickensided surfaces, cuspate in cross section with the curviplanar deformed surfaces oriented concave up. The palaeosol stratigraphy is well established over the entire Makhtesh Ramon area and this afforded the opportunity of obtaining controlled structural measurements on the folded surfaces and their associated slickensided striae as a means of providing data for reconstruction of the fold geometry.Stereographic projection of the poles to the LDF fold surfaces, on two separate palaeosol horizons from several localities, together with the slickensided striae, were plotted on the lower hemisphere of a Schmidt equal-area net. The LDF folds were seen to be symmetrical and asymmetrical structures with a gently plunging fold axis of 4–10°. Maximum and minimum dip values of the cuspate curviplanar surface (SP₁) were well emphasized by the plots (20° and 30° for symmetrical structures) and data from the two horizons obtained from several localities showed remarkable uniformity.A second slickensided, curviplanar surface of deformation (SP₂) shows the same range of dip values as SP₁ and intersects the SP₁ surface normal to the SP₂ fold axis. The internal arrangement of symmetry elements within the LDF folds remains approximately constant regardless of the large variation between the gross morphological parameters such as amplitude and wavelength, and this appears to be a reflection of the response of a soil with inherent anisotropies, to stress.The geometry of the LDF structure resembles that of linear or wavy gilgai. The SP₁ surface therefore is most likely the result of upthrusting on the edges of drainage rills affected by differential wetting. The SP₂ surface bears a constant geometric relationship with SP₁ and is therefore considered to have formed penecontemporaneously during the upthrusting of the SP₁ blocks. A rectangular surface fracture pattern parallel to and normal to topographic slope, is considered to be an alternative means of initiating the upward growth of the soil microrelief features.