No abstract

No abstract

ABSTRACT:Temperatures of nine thermometer screens during a 6-year field experiment in De Bilt (the Netherlands) have been compared. The screens are currently in use throughout the world and comprise the following types: an aspirated Young screen, four naturally ventilated round-shaped multi-plate screens (KNMI, Vaisala, Young, Socrima), a slightly aspirated version of the KNMI screen, a synthetic Stevenson screen (both aspirated and naturally ventilated) and a naturally ventilated wooden Stevenson screen. The multi-plate KNMI screen served as a reference. For the daily minimum, maximum, and mean air temperatures (T n , T x , T mean ), the absolute seasonal mean differences with the reference were almost all ≤ 0.1°C. An exception is the aspirated Young screen for which differences in mean T x in summer (JJA) are most notable and amount to −0.43°C. The differences of the individual T n , T x , T mean values may be much larger than their seasonal averages. For the aspirated Young and the naturally ventilated Stevenson screens they are most notable, where the Young is generally cooler (T x and T mean ) and the Stevensons warmer than the reference. The absolute temperature differences between the screens and the reference are shown to increase with decreasing cloud cover and windspeed. Furthermore, using the original 15-s samples it is shown that random variations cause fast-responding screens to have more extreme T n , T x values than slow-responding screens. For a supposed transition of the natural ventilated synthetic Stevenson screen to the reference screen, transfer functions are successfully developed for the 10-min temperature data and the daily T n and T x data. It is argued that the explained variance of the models could have further improved when high-accuracy (especially in the range 0-3 m/s) windspeed measurements were available (at screen level and position).

ABSTRACT:Temperatures of ten thermometer screens have been studied for particular weather conditions during a 6-year field experiment in De Bilt (the Netherlands). The comparison comprised two versions of an aspirated Young screen, four naturally ventilated round shaped multi-plate screens (KNMI, Vaisala, Young, Socrima), a slightly aspirated version of the KNMI screen, a synthetic Stevenson screen (both aspirated and naturally ventilated) and a naturally ventilated wooden Stevenson screen. All the screens were equipped with fast-responding sensors. A simple method is presented to obtain intersensor accuracies of about 0.03°C under field conditions. The response time of the screens is studied by making a daily comparison of the time stamps of the minimum and maximum temperatures. The analysis shows that the response of the naturally ventilated Stevenson screens is about 7-8 min slower than for the other screens. The screens have been compared for conditions of rainfall, wind, clear sunny days, days with snow cover and days with fog. It is demonstrated how these weather conditions affect the temperature measurements of the screens. The results show that the screens can roughly be classified into three distinct groups: (1) the round shaped multiplate screens, (2) the naturally ventilated Stevenson screens, and (3) the strongly aspirated screens. Owing to the complexity of reducing climate and siting dependent environmental impacts on temperature measurements, it is not possible to design one particular screen as a worldwide reference. For each climate, a special screen has to be developed as the best balance between the application of impacts reduction techniques and sensing the real air temperature.

GRANIT, R. and J. P. VAN DER MEULEN. The pause during contrartion in the discharge of the spindle afferents from primary end organs in cat extensor muscles. Acta physiol. scand. 1962. 55. 231-211. -Recently much detailed information has become available about the structural design of the muscle spindles. I t seems highly pertinent that the large spindle-afferents from primary end organs possess two kinds of terminals, one set deriving from the nuclear bag of special 'nuclear bag'-fibres, another from purely muscular, short, so-called 'nuclear chain'-fibres. Also spindles may vary in length over more than a tenfold range (cat). The pause in the discharge of the muscle spindles in isometric contraction has been studied and the findings evaluated from the point of view of spindle anatomy. The primary end organs were found to fall into two groups, long-pause spindles and shortpause spindles. This grouping is assumed to express their anatomical length. This may vary between 2 and 22 mm. The pause either ended with a phasic burst, often succeeded by a brief, secondary pause, or else the discharge was resumed in a tonic fashion. Thus spindles were 'phasic' or 'tonic' with respect to how they resumed firing after the 'pause'. Nearly all the 'tonic' spindles were found among the longpause spindles. The hypothesis adopted to explain the phasic-tonic differentiation is that phasic spindles are dominated by 'nuclear bag'fibres, tonic ones by 'nuclear chain'-fibres. Spindles are also known to vary considerably with regard to the relative number of these two different fibre types.