The atmospheric boundary layer mixing height (MH) is an important bulk parameter in air quality (AQ) modelling. Formulating this parameter under statically stable conditions, such as in the Arctic, has historically been difficult. In an effort to improve AQ modelling capacity in North America, MH is studied in two geographically distinct areas: the Arctic (Barrow, Alaska) and the southern Great Plains (Lamont, Oklahoma). Observational data from the Atmospheric Radiation Measurement program, Climate Research Facility and numerical weather forecasting data from Environment Canada's Regional Global Environmental Multiscale (GEM15) model have been used in order to examine the suitability of available parameterizations for MH under statically stable conditions and also to compare the level of agreement between observed and modelled MH. The analysis period is 1 October 2011 to 1 October 2012. The observations alone suggest that profile methods are preferred over surface methods in defining MH under statically stable conditions. Surface methods exhibit poorer comparison statistics with observations than profile methods. In addition, the fitted constants for surface methods are site-dependent, precluding their applicability for modelling under general conditions. The comparison of observations and GEM15 MH suggests that although the agreement is acceptable in Lamont, the default model surface method contributes to a consistent overprediction of MH in Barrow in all seasons. An alternative profile method for MH is suggested based on the bulk Richardson number. This method is shown to reduce the model bias in Barrow by a factor of two without affecting model performance in Lamont. 相似文献
GPS Solutions - goGPS is a positioning software application designed to process single-frequency code and phase observations for absolute or relative positioning. Published under a free and... 相似文献
Experimental analysis was performed using multiplicative algebraic reconstruction technique (MART) to map the ionosphere over Brazil. Code and phase observations from the global navigation satellite system (GNSS) together with the international reference ionosphere (IRI) enabled the estimation of ionospheric profiles and total electron content (TEC) over the entire region. Twenty-four days of data collected from existing ground-based GNSS receivers during the recent solar maximum period were used to analyze the performance of the MART algorithm. The results were compared with four ionosondes. It was demonstrated that MART estimated the electron density peak with the same degree of accuracy as the IRI model in regions with appropriate geometrical coverage by GNSS receivers for tomographic reconstruction. In addition, the slant TEC, as estimated with MART, presented lower root-mean-square error than the TEC calculated by ionospheric maps available from the International GNSS Service (IGS). Furthermore, the daily variations of the ionosphere were better represented with the algebraic techniques, compared to the IRI model and IGS maps, enabling a correlation of the elevation of the ionosphere at higher altitudes with the equatorial ionization anomaly intensification. The tomographic representations also enabled the detection of high vertical gradients at the same instants in which ionospheric irregularities were evident. 相似文献
Two rock series are distinguished in the Nain anorthosite massif: the anorthosite-adamellite suite, occupying most of the massif, and the troctolite-syenite suite, which occurs in layered intrusions. Field relations show that troctolitic rocks intrude anorthositic rocks, but are intruded by adamellitic rocks.
The following evolutionary model is suggested for the Nain massif. Fractional crystallization in a parental magma resulted in a density-stratified magma mass in which plagioclase crystals accumulated by suspension at a level where the density of crystal and liquid matched. Thus, a plagioclase cumulate formed, which was underlain by heavier troctolitic magma and overlain by lighter acidic magma. Settling of the plagioclase mass caused local intrusion of troctolitic magma, which differentiated in members of the troctolite-syenite suite. Subsequent disturbance of the magma chamber distorted the solidified portion, and caused local intrusive relationships between it and the acidic rest magma, which further differentiated in members of the adamellite series. 相似文献
Zusammenfassung Der Diffusionsstrom des Wasserdampfes in Schnee und dessen Anteil am Stoffumsatz wird unter vereinfachenden Annahmen über
die Schneestruktur und den Mechanismus der Diffusion berechnet. Für einen linearen Temperaturverlauf im Schnee folgt ein Abbau
von Substanz an der warmen Begrenzungsfl?che und eine daran anschlie?ende, nach der kalten Seite hin abnehmende Verdichtung.
Der so berechnete Umsatz ist quantitativ nicht ausreichend für die Deutung der Schneemetamorphose, so da? noch andere Prozesse
wie Thermodiffusion am Austausch beteiligt erscheinen.
Summary The diffusion of water vapor in snow and its influence on the mass exchange is calculated under simplifying assumptions on
the snow structure and the mechanism of diffusion. With a constant temperature gradient in a snow body a loss of solid substance
is obtained on the warm boundary of the sample and adjacently a condensation in the snow which decreases toward the cold end.
The computed mass transfer is not quite sufficient for interpreting the metamorphism of snow. Other processes such as thermodiffusion
seem to be involved in the mass exchange.
Résumé Le courant de diffusion de la vapeur d'eau dans la neige et sa contribution à l'échange de matière sont calculés en adoptant
des hypothèses simplificatrices pour la structure de la neige et le mécanisme de la diffusion. Avec un gradient de température
constant, il se produit sur la surface chaude une évaporation, juxtaposée à une zone de condensation décroissante vers le
c?té froid. L'échange ainsi calculé ne suffit pas quantitativement à expliquer la métamorphose, ce qui indique que d'autres
phénomènes, tels que la thermodiffusion contribuent aux échanges.
Mit 1 Textabbildung
Herrn Dr.W. M?rikofer zu seinem 70. Geburtstag gewidmet. 相似文献