Stevenson Screen Research Articles

Patterns of activity and inactivity in echidnas (Tachyglossus aculeatus) free-ranging in a hot dry climate: correlates with ambient temperature, time of day and season

Echidnas occur throughout Australia. They exhibit daily fluctuations in body temperature (Tb) and use torpor to various degrees throughout much of their range. Echidnas elsewhere are commonly diurnal except during hot weather. This study used temperature-sensitive radio-transmitters to investigate the activity patterns and temperature relations of echidnas in the relatively hot, dry climate of south-west Queensland with respect to temperature and photoperiod. During activity, echidnas were characterised by rising, but not necessarily high, Tbs. Activity was seen only within an ambient temperature range (as measured in a nearby Stevenson Screen: Tss) of 9–33�C so that activity was seen during the day and at night during the cool weather but only at night in summer. Echidnas used caves, burrows and logs when inactive. Tbs of inactive echidnas declined except when affected by rising ambient temperatures, as determined within these shelters (Ta). In summer, Tbs of echidnas in these shelters changed little or rose with increasing Ta to levels even higher than in active echidnas.Torpor was used by echidnas for periods up to nine days during winter and occasionally for up to one day during summer. Due to the difficulty of identifying the occurrence of torpor from Tb alone in warm conditions, the possibility that echidnas utilise torpor for less than one day remains inconclusive. Nevertheless, at least five bouts of torpor were identified in four (of eight) echidnas during winter/spring and two bouts of torpor from two echidnas in summer.

Daily temperature extremes for Britain

The utmost care has been taken in checking available records and conditions of thermometer exposure in order to provide tables of Britain’s extreme temperatures for every date of the year. The stages at which comparable standards of exposure (including site exposure) were implemented, following the invention of the Stevenson screen in 1866, have been discussed by Webb and Meaden (1993) and Parker (1994). Table 1 lists Britain’s highest recorded temperatures for every date of the year. This covers the period beginning with the introduction of standardised thermometer exposure in the mid-1870s and ending on the last day of 1999. It fully updates the list published by Meaden and Webb (1984), and revised by Webb and Meaden (1997). The distinction between ‘standard’ and ‘representative’ stations must be noted. Camden Square, although not quite meeting the criteria for an ideal standard station, was probably very representative of inner London. Likewise, the early twentieth-century stations at Epsom and Beddington were, then, quite representative of town gardens in the home counties. Table 2 includes a fully updated version of the table of daily extreme minimum temperatures for the eight months October to May inclusive, first published by Webb (1 985). The extremes listed are limited to sites below 500 m, excluding ‘high-level’ weather stations which are not at permanently inhabited heights (e.g. Ben Nevis Observatory!). The highest village in England is Flash (Staffordshire) at 463m. Reported minima for June to September include many readings from such upland sites, making the compilation of a daily list of minima for this period of the year impracticable. Moreover, comprehensive summer ‘lows’ would arguably be of only technical interest, as it is cold summer days which stick in the public awareness (and which attract media attention). However, recorded lows for each 10-day period in these four warmest months have been included in Table 2, in order to answer questions such as “what is the lowest temperature on record in late June”, or “in early September”. Table 2 covers the 125 years ending in 1999. Local factors (adiabatic warming, relative altitude, soil type, etc.) can raise summer maxima by up to about 2 degC above general levels. The fohn effect in winter (Lockwood 1962) can account for larger anomalies downwind of mountain ranges. Otherwise highs more than 2 degC above adjacent stations (at comparable altitudes) must be treated with scepticism. Potential pitfalls in the study of temperature (and other) extremes are discussed by Dukes and Eden (1 997). The larger local variations in extreme minimum temperatures make it less appropriate to reject the authenticity of such readings on the basis of support from other stations alone, especially as their occurrence has often been in areas with a low density of climatological stations. Over the past 20 years, remote sensing of surface temperatures has been effectively used to identify very localised extreme minima, e.g. in 198 1-82 (Roach and Brownscombe 1984). This has highlighted the fact that we probably do not know the absolute range of British temperatures, because it is unlikely that orthodox thermometer screens have always been sited at the coldest spots (McClatchey et al. 1987)! From earlier in the period under discussion, there remain some sites for which full details are elusive, e.g. the site at Aviemore (certainly a cold location) from which several low minima were quoted for 1895 (Bayard and Marriott 1895). As discussed in Webb and Meaden

Behaviour of tsetse (Diptera: Glossinidae) during the hot season in Zimbabwe: the interaction of micro-climate and reproductive status

AbstractStudies were made of the behaviour of Glossina pallidipes Austen and G. morsitans morsitans Westwood during the hot season (September–November) in Zimbabwe, and attributes of samples of tsetse from refuges, odour-baited traps, targets and mobile baits were compared. Various arrangements of electric nets were used to study tsetse as they entered or left artificial refuges. The peak time of entry into a refuge varied between 0800 h and 1400 h and coincided with the time when the air temperature reached 32°C; the response was stronger if 32°C occurred earlier in the day. The peak time of exit varied between 1500 h and 1700 h, being significantly later on hotter days, but did not show a clear temperature threshold. Micro-meteorological measurements showed that refuges were significantly cooler than the surrounding riverine woodland during the day but warmer at night. There was no significant difference between the air temperatures in leafless mopane woodland and semi-evergreen riverine woodland during the day but at night the riverine woodland was significantly cooler. Combining the micro-meteorological data with the estimated local movements of tsetse suggested that during the hot season, tsetse experienced temperatures 2°C cooler than the daily mean in a Stevenson screen located in mopane woodland. Compared with the catches of tsetse from traps, refuges had higher proportions of G. m. morsitans, males, young flies and females in the later stages of reproduction, and it is suggested that during the hot season, samples from refuges were less biased than traps with respect to species and sex composition, age and reproductive status. During the hot season, tsetse populations declined by c. 90% and although air temperatures exceeded lethal levels (c. 40°C), the refuge-entering responses meant that adult flies probably experienced a maximum of only c. 35°C. It is suggested that the decline in numbers is not due to direct mortality effects of temperature on adults but may be due, in part, to a doubling in the rates of reproductive abnormality during the hot season and an increase in adult mortality related to a temperature-dependent decrease in pupal period.

Wheat spike temperatures in relation to varying environmental conditions

Most field studies investigating the effect of temperature on growth processes use temperatures recorded within a Stevenson screen. These are likely to deviate from temperatures within the plant. This investigation reports a comparative study of methodologies and applications for measuring temperatures in the field during grain development by comparing Stevenson screen, ambient (air temperatures within the crop canopy), and wheat spike temperatures. Miniature sensors were inserted into wheat spikelets located midway on the spike of a primary tiller at anthesis. Located also within the crop canopy, and at the same height as the spike sensors, were sensors to measure ambient temperatures. Stevenson screen temperatures were also recorded at the site. Temperatures were recorded automatically every 12 min during grain filling from anthesis to maturity. Plants were grown in dryland and irrigated conditions within the same location, with the aim of determining differences in plant temperatures between stressed and non-stressed plants. Stevenson screen temperatures did not relate closely to ambient or spike temperatures. Plants growing in adequate soil moisture conditions had spike temperatures lower than ambient temperatures, but in some dryland trials, where soil moisture was limiting, spike temperatures equalled ambient temperatures, indicating that the plants were under moisture stress. Temperature differences of up to 5˚C were observed between the spikes of irrigated and non-irrigated crops on a hot day. Neither ambient nor screen temperatures gave an accurate measurement of spike temperature on hot days. Spike temperature differences between 2 cultivars, awned and awnless, were investigated. Trends were not consistent over both years; however, in 3 of the 4 environments, the maximum spike temperatures were higher for the awned cultivar (Hartog) than the awnless cultivar (Halberd). On very hot days, when ambient temperatures exceeded 40˚C, spikes of Hartog were cooler than those of Halberd.

COMMENT ON ‘HISTORICAL THERMOMETER EXPOSURES IN AUSTRALIA’ BY N. NICHOLLSET AL.

This short note presents seasonal time series for the 1888–1946 period of Adelaide temperature records comparing Glaisher stand and Stevenson screen data, as examined by Nicholls et al.. Site changes and a station move may account for discontinuities in the seasonal trends, which make the data unrepresentative as a test of comparative thermometer exposure. Research directions are suggested that may cast light on these problems in the data. © 1997 by the Royal Meteorological Society.

HISTORICAL THERMOMETER EXPOSURES IN AUSTRALIA

There is ample contempory evidence that most meteorological themometers in Australia were not exposed in Stevenson screens until very late in the nineteenth century, and in many places not until well into the twentieth century. There is also evidence, from a long-running comparision at Adelaide, that mean temperatures in a Stevenson screen are lower than in an open stand in Australian conditions. Thus, there are strong grounds for expecting that ninteenth century, and some early twentieth century, Australian temperatures are biased warm, relative to modern exposures.

Comment on D. E. Parker, ‘effects of changing exposure of thermometers at land stations’

AbstractThis short note reviews the Minutes of two Intercolonial Meteorological Conferences, held at Melbourne, Australia in 1881 and 1888, where the transcripts refer to the use of the Stevenson screen. Additional historical and modern material is reviewed demonstrating the use of the Stevenson screen in late nineteenth century Australia and Fiji. Some possible implications for the climate change debate in Australia are considered.

Effects of changing exposure of thermometers at land stations

AbstractIn view of the implications for the assessment of climatic changes since the mid‐nineteenth century, systematic changes of exposure of thermometers at land stations are reviewed. Particular emphasis is laid on changes of exposure during the late nineteenth and early twentieth century when shelters often differed considerably from the Stevenson screens, and variants thereof, which have been prevalent during the past few decades. It is concluded that little overall bias in land surface air temperature has accumulated since the late nineteenth century: however, the earliest extratropical data may have been biased typically 0.2°C warm in summer and by day, and similarly cold in winter and by night, relative to modern observations. Furthermore, there is likely to have been a warm bias in the tropics in the early twentieth century: this bias, implied by comparisons between Stevenson screens and the tropical sheds then in use, is confirmed by comparisons between coastal land surface air temperatures and nearby marine surface temperatures, and was probably of the order of 0.2°C.

Metabolic rates of tsetse flies in the field as measured by the excretion of injected caesium

ABSTRACT Teneral tsetse flies, Glossina morsitans morsitans Westw., were injected with labelled caesium (137Cs) <18 h after emergence and released in the Zambezi Valley of Zimbabwe between May 1983 and June 1984, and again in February 1985. Radioactivity in flies recaptured time t days after injection indicated a three‐stage exponential loss of caesium, identical for both sexes. For t≫4 the estimated rate constant (‐0.119 per day) was significantly lower than for 4≫t≫12 (–0.252 per day). By day 15 about 97% of the isotope had been excreted; thereafter the loss rate fell by an order of magnitude. The data for t>4 days were well fitted by the sum of two exponentials but no smooth function was found to fit all three phases. The loss rate from the rapidly metabolized pool increased exponentially with temperature at the same rate as for male tsetse kept in the dark in the laboratory. However, the loss rate in the field was lower at every temperature, suggesting that these flies live at 2–6oC lower than the average Stevenson screen temperature. Published estimates of hunger cycle and daily flight durations, made on the basis of measured rates of caesium excretion, are invalid because they use the assumption that flies are living in the field at screen temperatures. The data suggest that both sexes have the same metabolic rate up to the age of about 15 days, which implies that the females (being larger and having to nourish a larva in the latter stages of this period) must be less active and/or live at even lower temperatures than the males.

A small unaspirated screen for air temperature measurement

Abstract Performance data is presented for a small unaspirated temperature screen, a modification of the stacked plate design. The mean difference between temperatures recorded in the small screen and temperatures recorded in a Stevenson screen was 0.3°C during the day and 0.1°C at night. The effect of wind speed on daytime temperature error is discussed.

Estimating evapotranspiration from wheat using weather measurements and carborundum or Piché evaporimeter

Hourly evaporation rates from a Piché evaporimeter installed inside a Stevenson screen were compared with rates measured from a Piché exposed to the atmosphere, but screened from direct short- and long-wave radiation (shaded) and with rates registered on a carborundum evaporimeter similarly exposed. Strict linear relationships exist between evaporation from the shaded Piché evaporimeter, the Piché in a screen and the shaded carborundum evaporimeter. The latter was 1.6 times more sensitive than the shaded Piché. The shaded Piché was 1.4 times more sensitive than the screened Piché. Regression equations for the aerodynamic term (AT) in the Penman-Monteith equation were developed. AT was expressed in terms of hourly evaporation measured by a Piché in a Stevenson screen ( Epsc), an exposed, but shaded Piché ( Eps), and a carborundum evaporimeter ( Ecs). The following relationships were found: 1. (i) AT = 0.018 ( Epsc) + 0.09 (mm h −1) r = 0.95 2. (ii) AT = 0.014 ( Eps) + 0.05 (mm h −1) r = 0.96 3. (iii) AT = 0.008 ( Ecs) + 0.06 (mm h −1) r = 0.95 Estimates of maximum evapotranspiration rates, ETm, obtained by substituting these relationships for AT in the Penman-Monteith equation were then tested against lysimeter measurements of ETm. In 1985, values of the index of agreement varying between 0.94 and 0.95, and mean absolute difference varying from 0.10 to 0.09 mm h −1, for the three types of evaporimeters were obtained from these comparisons. In 1986, values of the corresponding test parameters were 0.92 and 0.09 mm h −1 when the carborundum evaporimeter was used. These values demonstrate the reliability of the proposed model. While the sensitivity of the evaporimeters varied greatly, no one proved more accurate than any other. The carborundum evaporimeter proved to be the most sensitive.

Autumn Frost Damage on Young Picea sitchensis 1. Occurrence of Autumn Frosts in Scotland compared with Western North America

Dates of first autumn air frosts (in Stevenson screens) of −2.5°C and 4.5°C were obtained for 42 meteorological stations in northern Britain with runs of 18 to 116 years. Frequency distributions of first frost dates were approximately normal. Altitude, distance from the sea, latitude and distance from the NWSE axis of Britain together accounted for 75% and 81% of the variation in dates of first −2.5°C and −4.5°C frosts, respectively, at the 42 stations. The variance in dates of first frosts decreased from lowland coastal to upland inland sites. Multiple regressions were used to produce maps of first frost dates in 20 × 20 km grid squares of Scotland. Dates of first 28°F (−2.2°C) and 24°F (−4.4°C) frosts were obtained for 20 sites in western North America, spanning the natural range of P. sitchensis . Mean dates were earlier, and variances decreased, from south to north. Upland sites like Eskdalemuir and Kielder Castle experience –2.5°C and −4.5°C frosts earlier in the autumn than all coastal stations in western North America south of about latitude 58°N (between Cordova and Sitka), and about 4 weeks earlier than at Masset on the Queen Charlotte Islands. Thus, P. sitchensis from Q.C.I. and further south may often experience autumn frosts in Scotland before the trees have experienced the cool/short days that they require to induce frost hardening.

The performance of a thermometer screen on an automatic weather station

The performance of a Didcot-type thermometer screen on an Automatic Weather Station and a conventional Stevenson screen were compared, both with each other and against an aspirated Assmann psychrometer. Maximum temperature in the Didcot screen exceeded the conventional screen maximum by up to 1 K on calm, sunny days, and Didcot minimum temperatures were as much as 1.5 K less than the screen minima on still, clear nights; mean temperature discrepancies between screens were + 0.3 and − 0.4 K for maxima and minima, respectively. The apparent psychrometric constant for the Didcot screen was 1.0 mbar K −1 which increased to 1.2 mbar K −1 when u < 2 m s −1 in contrast to the value of 0.799 mbar K −1 frequently used for the Stevenson screen.

Accumulated temperatures in some pest habitats in 1976–1978

Temperatures were measured at eight points in the soil and in a Stevenson screen on a 6 × 16 m experimental plot at Harpenden, southeastern England. Accumulated temperatures of 430 day-degrees C above 5°C were reached earliest at depths of 5 cm beneath flat bare soil and under the south slope of a small grass-covered mound. Temperatures were also accumulated to 150 day-degrees C above 10°C for the same sites and compared with those from four sites on the bark of a small apple tree on the same plot. The 150 day-degrees was reached very much earlier on the south-facing bark than at any other site, reflecting the large daily fluctuation in temperature on the bark, where maxima exceeded 40°C on occasions. The significance of these results in relation to insect emergence is discussed.

Rate of deposition, and resistance to deposition, of fluorides on alkali-impregnated papers

Two years of weekly observations of airborne fluoride concentrations, rates of deposition in gauges and on alkali papers and environmental variables were analysed. Many of the variables were strongly correlated but partial correlations indicated that deposit gauges retained mostly larger particulate fluorides by wet and dry deposition, whereas alkali papers suspended in a Stevenson screen principally retained gaseous fluoride. The relationship between gaseous F and F retained on alkali papers was sufficiently precise for papers to be used for environmental monitoring. Temperature, precipitation and wind speed had no discernible effect on the rate of deposition on alkali papers. The rate of deposition of fluoride on papers was analysed in terms of resistance and compared with published work. This showed that there were major differences in the rates of deposition reported by different authors that arose largely because the aerodynamic resistance was a major component of the total resistance to fluoride deposition. Variations in technique, such as the design of the shelter, that affect aerodynamic resistance, have a dominating effect on the total resistance. Comparability between laboratories using alkali papers for monitoring purposes can be achieved only by careful design and standardisation of the technique.

A study of runway temperature and screen temperature over Santacruz Airport

Variations in runway temperature affect air density over the runway and this affects the lift of an aircraft and its effective payload. Temperature measured by an electrical thermometer installed near the runway (indicated as R) has been found to vary with temperature measured by a thermometer placed in a Stevenson's screen (indicated as S) within a wide limit of +5. 9 deg. C to -4.0 deg. C. This study is based on observations at Santacruz airport and discusses the diurnal, seasonal and annual variations of (R-S). Causes of such variations have also been investigated.

DEGREE-DAY RELATIONSHIPS TO THE DEVELOPMENT OF LITHOCOLLETIS BLANCARDELLA (LEPIDOPTERA: GRACILLARIIDAE) AND ITS PARASITE APANTELES ORNIGIS (HYMENOPTERA: BRACONIDAE)

AbstractDegree-day relationships in the development of Lithocolletis blancardella (Fab.) and Apanteles ornigis Weed, its major parasite, were established from laboratory and field studies in Ontario apple orchards during 1973, 1974, and 1975. Under constant laboratory conditions, temperature thresholds for development of overwintering pupae were estimated by three methods, and found to be 6.3°, 6.7°, and 5.7°C for L. blancardella, and 10.4°, 10.4°, and 11.3°C for A. ornigis. Degree-day accumulations in the field were calculated by two methods using daily maximum and minimum temperatures recorded from the pupal habitat and a Stevenson screen. Degree-days in the pupal habitat accumulated from 1 January, above 5.7°C for L. blancardella and 11.3°C for A. ornigis were more accurate than Stevenson screen degree-day accumulations for predicting first emergence; however, after emergence, seasonal development was best related to Stevenson screen degree-days accumulated from 1 April, above 6.7°C for L. blancardella and 10.4°C for A. ornigis. This study shows that degree-day relationships can be used in an apple pest management programme to optimize timing of insecticide applications against L. blancardella and preserve A. ornigis, its major natural enemy.

The effect of climate on the photosynthesis of Picea mariana at the subarctic tree line. 1. Field measurements

Field measurements of the diurnal rates of photosynthesis of Picea mariana, the dominant tree species at the subarctic tree line, were made during the summers of 1972 and 1973 at Schefferville, Quebec (latitude 55° N). All relevant plant physiological and environmental parameters were also monitored. Photosynthesis was measured with an open gas analysis system with temperature-controlled cuvettes. Maximum daily rates were 2.0–3.5 mg CO2 g−1 dry weight h−1. Daily totals were between 15 and 30 mg CO2 g−1 dry weight. Temperature was unimportant in affecting daily photosynthesis totals during the summer months. The photosynthesis vs. needle temperature curve had an optimum of 15C. Dark respiration rates were 0.2–0.4 mg CO2 g−1 dry weight h−1 at 15C. The photosynthesis vs. light intensity curve was saturated at 0.8 ly min−1 (1.0 μE cm−2 s−1 PhAR.). As a result, heavy cloud cover considerably reduced daily photosynthesis. No seasonal variations in photosynthesis over June, July, and August were observed. No differences in maximum rates occurred between the three experimental sites. Needle temperatures within the cuvettes were 2–4C above air temperature under full sunlight (1.2 ly min−1). Needle temperatures under natural conditions were up to 7C above Stevenson screen temperatures and fluctuated rapidly with changes in turbulence.

Biology, Damage and Control of Rosy Rnstic Moth, Hydraecia micacea (Esp.), on Hops

SUMMARYThe biology and importance of rosy rustic moth as a pest of hops was studied during 1967–72 in Kent.First larvae were found inside hop bines between 19 April and 7 May and they normally tunnelled in the pith of bines until June; thereafter they attacked the subterranean crown and roots. Sometimes bine tunnelling did not occur before subterranean feeding. Pupae occurred in soil near damaged hills during July and August. The earliest pupa was found on 29 June 1967. Eggs collected in September and overwintered in a Stevenson screen hatched in early May in the subsequent year.Larval damage occurred more frequently in weedy gardens and was most severe on headlands. Some gardens were regularly damaged each year. Two DDT sprays applied on 6–7 May and 16–18 May gave good control of larvae. Generally, less effective control was obtained with fenitrothion, azinphos‐methyl and methidathion. On a headland where six per cent of bines were tunnelled, larvae were controlled with three DDT sprays and the yield of hops was increased 2·5 cwt/acre (314 kg/ha). Symptoms of Fusarium canker were found in a larger proportion of tunnelled bines than in undamaged bines.

THE DIURNAL AND SEASONAL PATTERN OF HATCHING OF WINTER MOTH EGGS, OPEROPHTERA BRUMATA (GEOMETRIDAE: LEPIDOPTERA)

AbstractWinter moth hatching begins daily at approximately 0645 hours A.S.T. both in the field during the normal hatching season and in the laboratory during the winter. This diurnal pattern is not related to temperature or light and appears to be intrinsic.The seasonal rate of hatching in the spring was related to accumulated heat. Eggs first exposed to cold December temperatures then stored at 35°F (1.7 °C) until early spring, were incubated at a series of controlled temperatures. The theoretical threshold temperature of development was determined as 41°F (5 °C). Accumulated degree-days based on this threshold did not give the best estimate of the time of hatching in the field where temperatures, because they were recorded in Stevenson’s screens (meteorological cabinets), were generally lower than those at the egg sites. The best estimate was obtained by using a lower base temperature of 39°F (3.9 °C) which compensated for differences in temperature between Stevenson screens and egg sites. Mean hatch in the field occurred when accumulated degree-days reached 292.A predictive curve is presented which predicted the date of mid-hatch of the winter moth to within 1 to 2 days over a 9-year period.