Recirculating Purging System for Hemispherical Net Radiometers

A purging system was developed to prevent internal condensation in hemispherical net radiometers without frequent changing of desiccant. Continuous recirculation of dry air through the radiometer and a desiccant tube prevented condensate formation during cool and wet periods

Automated verification of shape, size and bag properties.

In recent years, separation logic has emerged as a contender for formal reasoning of heap-manipulating imperative programs. Recent works have focused on specialised provers that are mostly based on fixed sets of predicates. To improve expressivity, we have proposed a prover that can automatically handle user-defined predicates. These shape predicates allow programmers to describe a wide range of data structures with their associated size properties. In the current work, we shall enhance this prover by providing support for a new type of constraints, namely bag (multi-set) constraints. With this extension, we can capture the reachable nodes (or values) inside a heap predicate as a bag constraint. Consequently, we are able to prove properties about the actual values stored inside a data structure

Controlled Cooling of Onion Umbels by Periodic Sprinkling

Low onion (Allium cepa L.) seed yields frequently occur without obvious reasons, particularly with hybrid varieties. Solutions to the problem need to be found to insure seed for bulb onion production. Water and temperature stress in the umbel may be factors during hot, dry, sunny weather. We investigated the relationship of umbel temperature to ambient and umbel conditions and the effects of periodic wetting of the umbels. Onions were grown in a field experiment at Kimberly, Idaho on Portneuf silt loam sail (Durixerollic Calciorthids; coarse-silty, mixed, mesic) using commercial practices except that periodic sprinkling was provided with a rotating-head sprinkler irrigation system when temperatures exceeded certain levels. Sprinkling for five min reduced floret temperatures as much as 15 C below ambient. The florets remained cool for 20 to 40 min, depending on umbel maturity, wind speed, and air temperature and humidity. Nearly mature umbels were hotter and required more sprinkling to keep cool. Five min of sprinkling every 20 to 30 min usually provided adequate cooling. A specially-designed temperature sensor was found to successfully simulate the behavior of an onion floret during wetting and drying, permitting direct control of the initiation, duration, and frequency of sprinkling. Excessive temperatures did not occur during the experiment, so seed yields were similar on and unsprinkled plots. While we have shown that periodic sprinkling will provide umbel cooling and minimize undesirable effects on pollination, similar studies need to be conducted in hotter, major seed producing areas to establish economic benefits

Hazard assessment at Mount Etna using a hybrid lava flow inundation model and satellite-based land classification

International audienceUsing a lava flow emplacement model and a satellite-based land cover classification, we produce a map to allow assessment of the type and quantity of natural, agricultural and urban land cover at risk from lava flow invasion. The first step is to produce lava effusion rate contours, i.e., lines linking distances down a volcano’s flank that a lava flow will likely extend if fed at a given effusion rate from a predetermined vent zone. This involves first identifying a vent mask and then running a downhill flow path model from the edge of every pixel around the vent mask perimeter to the edge of the DEM. To do this, we run a stochastic model whereby the flow path is projected 1,000 times from every pixel around the vent mask perimeter with random noise being added to the DEM with each run so that a slightly different flow path is generated with each run. The FLOWGO lava flow model is then run down each path, at a series of effusion rates, to determine likely run-out distance for channel-fed flow extending down each path. These results are used to plot effusion rate contours. Finally, effusion rate contours are projected onto a land classification map (produced from an ASTER image of Etna) to assess the type and amount of each land cover class falling within each contour. The resulting maps are designed to provide a quick look-up capability to assess the type of land at risk from lava extending from any location at a range of likely effusion rates. For our first (2,000 m) vent zone case used for Etna, we find a total of area of ~680 km2 is at risk from flows fed at 40 m3 s−1, of which ~6 km2 is urban, ~150 km2 is agriculture and ~270 km2 is grass/woodland. The model can also be run for specific cases, where we find that Etna’s 1669 vent location, if active today, would likely inundate almost 11 km2 of urban land, as well as 15.6 km2 of agricultural land, including 9.5 km2 of olive groves and 5.2 km2 of vineyards and fruit/nut orchards

Relationship Between Foliage Temperature and Water Stress in Potatoes

Field studies were conducted in southern Idaho to evaluate the possibility of using thermal infrared measurements of potato foliage to detect soil water deficits. Concurrent measurements of foliage-air temperature differences (Tf-Ta), leaf water potential (?leaf) and vapor pressure deficit (VPD) were obtained from differentially-irrigated Russet Burbank and Kennebec potatoes during the 1982 and 1983 growing seasons. Foliage-air temperature differences for well-watered potatoes were linearly related to VPD. Differences in Tf-Ta values between stressed and well-watered potatoes were relatively small in the early morning when evaporative demand was low. However, severe soil water deficits caused afternoon Tf-Ta values to rise as much as 8.0 C above non-stressed levels under conditions of high VPD. Foliage-air temperature differences and VPD data were used to construct a plant water stress index (PWSI) which reflected the rise in Tf-Ta, above non-stressed levels at a given VPD. The PWSI was linearly related to depressions in ?leaf caused by moderate to severe soil water deficits. However, the PWSI did not increase significantly above non-stressed values unless the soil matric potential ?soil fell below – 70 kPa (centibars). Since potatoes are normally irrigated before ?soil falls below – 60 kPa, it appears that foliage temperature measurements cannot be used to effectively schedule irrigation for this crop

Air Temperature and Vapor Pressure Changes Caused by Sprinkler Irrigation

The downwind effect of evaporation from sprinkler spray was studied in the field to determine if air temperature and vapor pressure were changed enough to influence plant growth and water use. Wet-bulb and dry-bulb temperature profiles were measured upwind and at three distances downwind from a sprinkler lateral before and during sprinkling. Wind-speed and direction were also measured. Air temperature generally was reduced less than 1 C, and vapor pressure in the air was increased less than 0.8 mb. This amount of change in the air temperature and humidity is not likely to be sufficient to cause any significant change in plant growth or evaporative loss of water

Response of Plant Water Potential to the Irrigated Environment of Southern Idaho

Laboratory studies have shown that plant water potential affects a number of key processes involved in growth, but there has been almost no information on what levels of water potential occur under irrigated conditions in the field. Before assessing the practical implication of laboratory results on soil and crop management, this type of information must be available. Consequently, plant water potential in irrigated crops of Zea mays, Triticum aestivum, Hordeum vulgaris, Phaseolus vulgaris, Pisum sativum, Solanum tuberosum, Beta vulgaris, and Medicago sativa, L. was measured throughout the growing season in southern Idaho. Soil moisture conditions and potential evapotranspiration were monitored. Daily changes in plant water potential varied from less than 5 bars to more than 20 bars, while random sampling of supposedly homogeneous sets of plants showed an average variation of about 2 bars. Changes due to differences in soil moisture were also detected, even though the soil moisture potential was kept high enough for near-optimum crop production. Though the crops differed widely in their response to changes in environment, the plant water potential was strongly affected by microclimatic conditions. Day-to-day changes in plant water potential generally correlated more closely with changes in potential evapotranspiration than with changes in soil moisture content. Many of the daily changes observed in the plants remain unexplained, however. In general, the average water potential levels of all the field-grown plants were lower than levels reported from growth chamber studies. Potentials seldom rose above —8 bars and were never observed above —5 bars

Photosynthesis Under Field Conditions. IX. Vertical Distribution of Photosynthesis Within a Corn Crop

The vertical distribution of the photosynthetic fixation of carbon dioxide within a crop of corn was calculated from carbon dioxide profile data and transfer coefficients obtained by analysis of windspeed measurements. Infrared analyzers were used to measure the carbon dioxide concentration at several heights within and above the crop. The calculated total fixation for the day was approximately 60 g CO? m-? (equivalent to 470 pounds of sugar per acre per day). The results demonstrated the importance of the upper leaves in the fixation of carbon dioxide and showed the increased fixation by the lower leaves during periods of high light penetration. There was some indication that a coupling existed between the level of windspeed and fixation under conditions of high light and relatively low windspeed. With refinement in technique the method could be used to obtain more quantitative estimates of the distribution of photosynthesis in other crops

The Energy Budget at the Earth's Surface: Assessing Sources and Sinks of Carbon Dioxide in a Corn Crop Using a Momentum Balance Approach

In two previous communications (Wright and Lemon 1966a, 1966b) an aerodynamic method was described for evaluating the source and sink distribution of carbon dioxide in plant communities. Some data were presented for a corn crop, giving quantitative information about photosynthetic fixation and respiration release of carbon dioxide, layer by layer, within the crop. In the method, CO2 concentration profiles and windspeed measurements of the bulk air were made within and above the crop. The analysis of the windspeed measurements to calculate diffusivity coefficients required tedious analysis of windspeed fluctuations and the application of complicated statistical and mixing length theories. It is our purpose to present here a simpler method, requiring vertical profiles of mean windspeed, vertical profiles of mean carbon dioxide concentration and representative vertical profiles of the foliage surface area density of the plant community

Measuring the Effects of Surface Features on the Atmospheric Boundary Layer with Instrumented Aircraft

The influence of mesoscale features (e.g., irrigation projects, desert regions, patches of forest, cities, etc.) on the atmosphere is difficult to determine unless the sensors are very numerous or highly mobile. An instrumented aircraft system permits such measurements and was used to determine the influence of lakes and reservoirs, irrigation, a group of forested hills, a small city, and an area of (dry land) nonirrigated agricultural land on the vertical and horizontal characteristics of the lowest layer of the atmosphere. Studies were conducted over portions of southern Alberta, and southern Idaho. Strong sensible heat advection was found to cause high evaporation from a small lake with the formation of a cool air layer which extended well beyond the lee side of the lake. The flux of water vapor over irrigated land was essentially double that over surrounding nonirrigated areas. A small city produced a heat island which delayed development of a temperature inversion for up to 9 h