Average winter temperatures at De Bilt (the Netherlands): 1634–1977

A very long series of average winter temperatures in the Netherlands is presented. The series is based on direct observations (1735–1977) and administrative data concerning Dutch canals (1634–1734). The sources and the reliability of the data are discussed. Some characteristics of the series are shown.     

Two applications for circumglobal radiation measured at De Bilt

Summary For each month a linear regression equation has been derived for the relation between the daily sums of circumglobal and global radiation based on measurements at De Bilt during a period of two years. The goodness of fit of this relation is proved by comparison of the standard deviations of the differences of the calculated and observed daily sums and of the standard deviation of the monthly mean of the global radiation or of this mean itself. Using the period of observations from 0 to 24 hrs. one gets results which are 52 per cent less accurate than those from a period of observations from 8 to 8 hrs. If one estimates the daily sums of the global radiation by means of a linear relation to the relative duration of sunshine the standard deviation of the differences between calculated and observed daily sums is 2.5 times as large as in the first case. From simultaneous measurements of the circumglobal radiation above a short grass mat (reflection coefficient 0.147 in the spectral region from 0.3 to 3.0 μ) and above a bare, sandy soil, rich in humus, the reflection coefficient of bare soil could be determined to 0.076 which is in good agreement to the results of other authors.

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Zusammenfassung Es werden lineare Regressionsgleichungen für alle Monate für die Beziehung zwischen den Tageswerten der Zirkumglobalstrahlung und der Globalstrahlung auf Grund von zweij?hrigen Messungen in De Bilt abgeleitet. Die Güte der Anpassung wird überprüft durch das Verh?ltnis der Streuung der Differenzen zwischen den beobachteten und berechneten Tagessummen der Globalstrahlung und der Streuung der Monatsmittel der Globalstrahlung oder diesem Mittel selbst. Die Verwendung der Beobachtungsperiode von 0 bis 24 Uhr führt zu einem um 52% schlechteren Ergebnis als die Periode von 8 bis 8 Uhr. Sch?tzt man die Tagessummen der Globalstrahlung mit Hilfe einer linearen Beziehung zur relativen Sonnenscheindauer, dann wird die Streuung der Differenzen zwischen berechneten und beobachteten Tagessummen 2,5 mal so gro? wie im ersten Fall. Aus gleichzeitigen Messungen der Zirkumglobalstrahlung über einer Grasmatte (Reflexionskoeffizient 0,147 im Spektralbereich 0,3 bis 3,0 μ) und über kahlem, sandigem, humusreichem Boden konnte der Reflexionskoeffizient des kahlen Bodens zu 0,076 bestimmt werden, was in guter übereinstimmung mit den Resultaten anderer Autoren ist.

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Résumé Partant de mesures effectuées durant deux ans à De Bilt, l'auteur établit pour chaque mois des équations de régression linéaire pour la relation existant entre les valeurs journalières de la radiation globale et de la radiation sphérique. Il en contr?le l'exactitude au moyen du rapport existant entre la dispersion des différences des sommes journalières calculées et mesurées de la radiation globale et la dispersion des moyennes mensuelles ou de ces moyennes elles-mêmes. En partant d'une période d'observation de 0 à 24 heures, on obtient des résultats de 52% moins exactes qu'à partir de la période située entre 8 et 8 heures. Si l'on estime la somme journalière de la radiation totale au moyen d'une fonction linéaire de la durée de l'insolation relative, la dispersion des différences entre les sommes calculées et observées est 2,5 fois supérieure au cas précédent. En mesurant simultanément la radiation sphérique sur un gazon (coefficient de réflexion 0,147 dans la bande située entre 0,3 et 3,0 μ) et sur un terrain nu, sablonneux et riche en humus, on a pu déterminer un coefficient de réflexion de 0,076 pour le sol nu, ce qui correspond bien aux valeurs indiquées par d'autres auteurs.

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With 3 Figures

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Dedicated to Dr.W. M?rikofer on the occasion of his 70th birthday.     

Identifying the Origin of Anomalous High Tropospheric Ozone in the Ozonesonde Data at Uccle by Comparison with Nearby De Bilt

Abstract

The ozonesonde stations at Uccle (Belgium) and De Bilt (Netherlands), separated by only 175?km, offer a unique opportunity to test the influence of different ozonesonde types and different correction strategies, as well as to detect the presence of inhomogeneities in the ozonesonde time series resulting from changes in sounding equipment (solution, radiosonde, ozonesonde, interface, sounding software, etc.). In particular, we highlight a 2.5 year period (beginning of 2007 to mid-2009) of anomalous high tropospheric ozone values measured by ozonesondes at Uccle and compare these with the observations from De Bilt. Because the ozone deviations are only observed in the free troposphere where ozone concentrations are relatively low, and not in the boundary layer or the stratosphere, this issue is directly related to the sensitivity of ozonesondes. Therefore, the effect of every instrumental change, even though small, during this 2.5 year anomalous period is analyzed considering a change in the radiosounding equipment, different ozonesonde batches, operational differences at the stations, differences on ascent and descent during the anomalous period; an environmental cause is also examined. Unfortunately, one single, specific cause for the observed high tropospheric ozone values at Uccle could not be identified. There are two explanations consistent with the observations and not ruled out by the analysis here: 1) the majority of the ozonesondes used at Uccle between March 2007 and August 2009 needed longer conditioning of their sensors and, therefore, behaved more accurately at low ozone concentrations during their descent or when used a second time, and 2) an environmental origin arising from a local difference in the air mass between Uccle and De Bilt and between the ascent and descent.     

The interpretation of baseline atmospheric turbidity measurements at Cape Grim,Tasmania

Five years of turbidity data at Cape Grim have been analysed. The turbidity at 500 nm in clean maritime airmasses from the South to the West shows a seasonal variation, with a minimum in winter. There is also a variation in turbidity with wind speed. The winter minimum can be explained partially by a minimum in wind strength in that season. On the assumption, based on observations at Cape Grim and at other locations, that the boundary layer turbidity is caused by seasalt haze, an attempt is made to interpret the observed turbidity values and their seasonal changes. Optical extinction coefficients at the surface deduced from the measured values of optical depth are compared with extinction coefficients calculated from Mie theory using particle size distributions measured at Cape Grim. Reasonable agreement is obtained when the growth of salt particles in the high maritime humidity is considered, using both theoretical models and previous experimental results together with the rapid increase in salt concentration with wind speed.     

Analysis of atmospheric turbidity levels at Taichung Harbor near the Taiwan Strait

In this study, two universal turbidity parameters, the Angstrom turbidity coefficient and Linke turbidity factor, are applied to study the atmospheric turbidity characteristics of Taichung Harbor. Meteorological parameter values were measured during 2004 and 2005 at the Wuchi weather station of the Taiwan Central Weather Bureau, near the Taiwan Strait. Results based on the Angstrom turbidity models (β_Lou, β_Pin, and β_Vis) indicated that annual mean values of the Angstrom turbidity coefficients were 0.174, 0.21 and 0.201, respectively. Four sets of Linke turbidity factors (T_Lin, T_Lou, T_Pin and T_Vis) were calculated using the original Linke method and the Dogniaux method, incorporating the computed Angstrom turbidity coefficients (β_Lou, β_Pin and β_Vis); the resultant values were 4.30, 6.40, 7.10 and 6.95, respectively. The monthly average values, frequency of occurrence, and cumulative frequency distributions were calculated using different models to describe the clear-sky atmospheric conditions at Taichung Harbor. The frequency results show that for over 50% of the dataset, three sets of Angstrom turbidity coefficients fell between 0.15 and 0.18, and four sets of Linke turbidity factors (T_Lin, T_Lou, T_Pin and T_Vis) fell between 4.0 and 6.5. Thus, for 50% of cloudless days, the sky can be between turbid and clear over Taichung Harbor. Furthermore, the results reveal that for 30% of the dataset, three Angstrom sets of turbidity coefficients (β_Lou, β_Pin, and β_Vis) exceed 0.2 and four sets of Linke turbidity factors (T_Lin, T_Lou, T_Pin and T_Vis) exceed 5.0. This indicates that 30% of cloudless sky conditions can be considered turbid to very turbid.     

The relationship between turbidity and spectral optical depth

Abstract

Spectral and spectrally integrated direct beam irradiances measured in Hamilton during the summer of 1981 were used to examine the relationship between the aerosol optical depth τ_a and Unsworth and Monteith's turbidity coefficient τ_A, which is a measure of spectrally averaged optical depth. Good correlation was obtained between τ_a at a wavelength of 0.67 μm and τ_A, thus confirming experimentally Blanchet's (1982) conclusion from a numerical study.     

Passive dew collection in a grassland area, The Netherlands

Passive dew collection experiments were initiated in late 2003 in the centre of The Netherlands within a grassland area. A specially designed 1 m² insulated planar dew collector, set at a 30° angle from horizontal, was covered with a thin (0.39 mm) polyethylene foil and subsequently replaced with 4 mm polyvinyl chloride. A second dew collector, in the shape of an inverted pyramid, was constructed to reduce the view angle to only the nighttime sky. A simple surface energy-budget model and an aerodynamic model were used to simulate the dew collected by both collectors. The planar collector collected about 90% of the dew at the grass cover while the pyramid collector collected about 1.20% of the grass cover. The aerodynamic model was able to predict the amount of collector data to within 50% for the planar collector and 60% for the inverted pyramid collector. The pyramid collector design was able to collect about 20% more dew than the inclined planar collector.     

The influence of climate upon the number of weather-working hours in combine harvesting in The Netherlands

Summary An outline is given of a method of estimating the number of hours during which the combine harvester can be operated in a certain harvesting period. This method is based on a study of the relation between the daily rainfall and the hourly estimates by 60 observers of the possibility of combine harvesting (weather-working hours).Over the years 1964, 1965 and 1966, the relationship between the possibility to combine harvest and the rainfall has been summarized in a linear regression equation:y=a+b ₁ x ₁+b ₂ x ₂, withy=mean number of weather-working hours per day per half-monthly period, x₁=mean daily rainfall per half-monthly period, x₂=number of dry days per half-monthly period.For chosen percentiles of the frequency distribution ofy the corresponding number of weather-working hours in the same period can be estimated for future years. Taking the (two dimensional) frequency distribution of x₁ and x₂ as fixed, confidence intervals for the estimated number of weather-working hours can be calculated.

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Zusammenfassung Es wird eine Methode zur Abschätzung der Stundenzahl, während der ein Mähdrescher innerhalb einer bestimmten Ernteperiode eingesetzt werden kann, besprochen. Die Methode beruht auf einer Untersuchung über die Beziehung zwischen der täglichen Regenmenge und der Möglichkeit des Mähdrescher-Einsatzes, welche von 60 Beobachtern Stunde für Stunde geschätzt wurde (Arbeitswetter-Stunden).Die Beziehung zwischen der Möglichkeit des Mähdrescher-Einsatzes und der Regenmenge wurde für die Jahre 1964, 1965 und 1966 in einer linearen Regresionsgleichung dargestellt:y=a+b ₁x₁+b ₂x₂, woy=mittlere Zahl von Arbeitswetter-Stunden pro Tag je Monatshälfte, x₁=mittlere tägliche Regenmenge pro Monatshälfte, x₂=Zahl der Trockentage pro Monatshälfte.Man kann für ausgewählte Perzentile der Häufigkeitsverteilung vony die entsprechende Zahl der Arbeitswetter-Stunden in derselben Periode für künftige Jahre abschätzen.Aus der zweidimensionalen Häufigkeitsverteilung von x₁ und x₂ können Konfidenzbereiche für die geschätzte Zahl der Arbeitswetter-Stunden berechnet werden.

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Résumé On discute une méthode permettant d'estimer le nombre d'heures durant lesquelles une moissonneuse-batteuse peut être engagée au cours d'une période déterminée de moisson. Cette méthode repose sur une recherche des relations existantes entre la somme journalière de précipitation et les possibilités d'utilisation de la machine, relevées d'heure en heure par 60 observateurs (heures employables de machine).La relation entre la quantité de précipitations et la possibilité d'emploi d'une moissonneuse-batteuse est représentée par des équations linéaires de régression pour 1964 aussi bien que pour 1965 et 1966:y=a+b ₁x₁+b ₂x₂. La signification des symboles est la suivante:y=le nombre moyen d'heures employables de machine par jour, calculé par un demi-mois,x ₁=la quantité journalière moyenne de précipitaations par un demi-mois, x₁=la quantité journalière moyenne de précipitaations par un demi-mois, x₂=le nombre de jours secs par un demi-mois.Partant de percentiles choisis de la distribution de fréquences dey, il est possible d'éstimer le nombre d'heures employables des moissonneuse-batteuses dans la même période pour les années a venir.Disposant de la distribution de fréquences des deux variablesx ₁ etx ₂ on peut calculer des intervalles de confidence pour le nombre estimé d'heures employables de machine par jour.

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With 1 Figure     

Interrelationships between atmospheric turbidity,the diffusely reflected visible radiation at the top of the earth's atmosphere and the global solar radiation at the surface

Summary The flux of radiation emerging at the top and bottom of a realistic model of a cloud-free, plane-parallel, vertically inhomogeneous turbid atmosphere has been computed for different values of atmospheric turbidity and surface albedo in 83 unequal spectral intervals over the short-wave or solar radiation (0.285–2.5 m) regime. These computations have been utilized to determine the diffusely reflected radiation at the top of the atmosphere in the spectral interval 0.535–0.7035 m (which covers the visible channels of the radiometers onboard the Geosynchronous Operational Environmental Satellites and the NOAA polar orbiting satellites) and in the spectral interval 0.375–0.7035 m. The total global solar radiation (0.285–2.5 m) reaching the surface has also been determined. Simple linear regression relationships have been established between (i) the reflected radiation at the top and atmospheric turbidity and (ii) between the global radiation at the surface and the reflected radiation at the top. These regression relationships yield coefficients of determination very close to unity. The implications of this strong linear dependence of the reflected radiation on atmospheric turbidity and of the global radiation at the surface on the reflected radiation at the top to satellite-based studies of the feasibility of estimation of the insolation (global radiation) at the surface are briefly mentioned.With 3 Figures     

Changes in integral and aerosol atmospheric turbidity in Trans-Baikal and Central Siberia

The analysis of time series of the Linke turbidity factors is performed for the atmosphere mass m = 2 (T ₂) and atmospheric aerosol optical thickness for the wavelength λ₀ = 0.55 μm (AOT) from the data of 14 actinometrical stations of Central Siberia and Trans-Baikal territory. It is shown that over the period from 1976 to 2006, the increased atmospheric transparency is observed in the region. Quantitative estimates of changes in multiyear mean annual variations of T ₂ and AOT at different periods of averaging and for different time periods are derived.     

横断山脉中段云岭白茫雪山的大气混浊度

本文根据1983和1984年横断山脉中段云岭白茫雪山东坡三个不同拔海高度(4292m、3760m和2025m)上测量的太阳直接辐射资料,计算并分析了云岭白茫雪山林克大气混浊因子T_P。T_P随拔海高度的升高而减小,不同拔海高度上T_p的年变化趋势基本一致,最大值出现在7、8月份,最小值在11月份。若将T_P分成气溶胶混浊因子T_R和水汽混浊因子T_W(T_P=1+T_R+T_W),水汽混浊因子T_W的年变化趋势与降水分布相吻合,气溶胶混浊因子T_R呈相反的变化趋势。地处干热河谷的奔子拦,由于局地气候的影响,其混浊度较大,接近海拔50m的北京,年平均值为3.09。     

Variability of the Linke and Unsworth-Monteith turbidity parameters in Athens, Greece

Summary  This work studies the variability of the Linke (T _L ) and Unsworth-Monteith (T _U ) turbidity parameters in the urban atmosphere of Athens. Beam irradiance observations performed at the Actinometric Station of the National Observatory of Athens are used in the period 1975–1995. This study examines (i) the inter-annual variation of T _L and T _U , (ii) their mean seasonal variability, (iii) their monthly average variation, and (iv) their mean daily variation. Also, for various air-mass origins, the mean seasonal variations of T _L and T _U are given. The frequency of occurrence of the parameters in various ranges is also shown. An innovative interpretation of the impact of the Saharan dust on the radiative properties in the atmosphere of Athens is attempted. Received May 19, 2000 Revised October 17, 2000     

Analysis and trends of atmospheric turbidity parameters over Cairo

Summary This work deals with the Linke turbidity factor, based on total spectrum observations of the direct solar beam and aerosol turbidity parametersa _a , , and based on observations in broad spectral bands. Diurnal and seasonal variations of these turbidity parameters were analyzed for the period 1975 to 1991.Annual variations of these parameters show low values in winter and high values in both spring and summer. The extinction coefficients decrease with increase of both wavelength and optical airmass. Trend analysis shows an increase in aerosol extinction coefficient below 0.63 m, and a slight decrease for longer wave-lengths.Linear regression relations are also constructed to estimate botha _a and whenT _L is available. The relations show thata _a can be estimated with errors below 20%. The relation with the parameter, may give better results when it is estimated by assigning a fixed value of .Nomenclature AV Monthly and total average of the measured parameter - a Atmospheric optical thicknes - a _a Aerosol optical thickness - a _r Mean value of optical thickness of. Rayleigh atmosphere over all wavelengths - a _o Ozone optical thickness - a _o Ozone absorption coefficient - a _w Water vapor optical thickness - COR Correlation coefficient of the linear relation in percentage - Ex₁, Ex₂, Ex₃ Aerosol extinction coefficients in the bands .2–.53, .53–.63, .63–.695, respectively - I _(o) Normal incident direct solar radiation, under clear sky condition - I _o Extraterrestrial insolation at normal incidence - m _r Relative (optical) air mass - NO Number of the observations used in either making the relation or the verification - RMSE Root mean square error of the linear relation - RMSE% Percentage value of the root mean square error relative to the average measured value AV - T _L Linke turbidity factor - T Dry bulb temperature in °C - u _o Ozone layer thickness, cm - Z Zenith angle - Ångström wavelength exponent - Ångström turbidity coefficient - Wavelength - Y The year number after 1975 With 5 Figures     

Neo-Atlantis: The Netherlands under a 5-m sea level rise

What could happen to the Netherlands if, in 2030, the sea level starts to rise and eventually, after 100 years, a sea level of 5 m above current level would be reached? This question is addressed by studying literature, by interviewing experts in widely differing fields, and by holding an expert workshop on this question. Although most experts believe that geomorphology and current engineering skills would enable the country to largely maintain its territorial integrity, there are reasons to assume that this is not likely to happen. Social processes that precede important political decisions – such as the growth of the belief in the reality of sea level rise and the framing of such decisions in a proper political context (policy window) – evolve slowly. A flood disaster would speed up the decision-making process. The shared opinion of the experts surveyed is that eventually part of the Netherlands would be abandoned.     

Short term variability of atmospheric turbidity and optical turbulence in a desert environment

Summary Variability of atmospheric turbidity calculated from direct beam solar radiation measurements and the transverse coherence length,r ₀, derived from differential image motion of stellar sources show pronounced fluctuations on the order of a few minutes under convectively unstable conditions in a desert environment. The quiescent periods, neutral events, when local near surface adiabatic conditions occur show substantial reductions in the fluctuations of the same quantities. Image motion results for nighttime (stable) conditions display slowing varying patterns with reduced short term (few minutes) variations.The measurements were taken using a suite of instrumentation probing the same volume of atmosphere. The instrumentation used includes a pyrheliometer, Atmospheric Turbulence Measurement and Observation System (ATMOS), a sodar, a scintillometer, and tower- mounted sensors. A time-height display of sodar data calibrated for the refractive index structure parameter,C _n ² , coupled with scintillometer measurements show the diurnal evolution of the boundary layer responding to the local heating-cooling cycle and drainage flows from the surrounding mountains. Several atmospheric features are seen and discussed in these results as they affect the nature of the patterns of turbidity andr ₀. Of particular interests are the development of convection, changes in the capping inversion, thermal plume structures, neutral events, and wave-turbulence interactions. Sinusoidal oscillations, identified as internal gravity waves, are seen in the nighttime laminated structures.With 10 Figures     

呼伦贝尔草原大气浑浊度的测量和尘埃输送的初步探讨

利用相对日射表和玻璃滤光片,于1974—76年的4—7月份在呼伦贝尔草原进行了大气浑浊度的测量。根据测量结果,研究了半干旱草原尘埃输送的特性。通过不同测点的对比,分析了草原开垦对尘埃输送的影响。