307 research outputs found
Analysis of the Systematic Errors Found in the Kipp & Zonen Large-Aperture Scintillometer
No full textStudies have shown a systematic error in the Kipp & Zonen large-aperture scintillometer (K&ZLAS) measurements of the sensible heat flux, H. We improved on these studies and compared four K&ZLASs with a Wageningen large-aperture scintillometer at the Chilbolton Observatory. The scintillometers were installed such that their footprints were the same and independent flux measurements were made along the measurement path. This allowed us to compare H and the direct scintillometer output, the refractive index structure parameter, C2n. Furthermore, spectral analysis was performed on the raw scintillometer signal to investigate the characteristics of the error. Firstly, correlation coefficients =0.99 confirm the robustness of the scintillometer method, and secondly we discovered two systematic errors: the low-C2n error and the high-C2n error. The low-C2n error is a non-linear error that is caused by high-frequency noise, and we suspect the error to be caused by the calibration circuit in the receiver. It varies between each K&ZLAS, is significant for H = 50 W m-2, and we propose a solution to remove this error using the demodulated signal. The high-C2n error identified by us is the systematic error found in previous studies.We suspect this error to be caused by poor focal alignment of the receiver detector and the transmitter light-emitting diode that causes ineffective use of the Fresnel lens in the current Kipp & Zonen design. It varies between each K&ZLAS (35% up to 240%) and can only be removed by comparing with a reference scintillometer in the field
Annotated Bibliography on O.K. Bouwsma Collection
No full textDr. Ronald Hustwit is the author of O.K. Bouwsma: A Philosophers Journey, Something About O.K. Bouwsma, An Annotated Bibliography of Bouwsma’s works, and an Index of The Bouwsma Collection at The Humanities Research Center, The University of Texas. He has edited five works of O.K. Bouwsma’s papers: Toward a New Sensibility, Without Proof or Evidence, Wittgenstein Conversations, Bouwsma’s Notes on Wittgenstein’s Philosophy and Bouwsma’s Commonplace Book.https://openworks.wooster.edu/bouwsma/1000/thumbnail.jp
Text of speech by Missouri House Representative O.K. Armstrong opposing amendment barring Japanese American doctor from practicing medicine
No full textText of Missouri House Representative O.K. Armstrong's speech in front of House of Representatives to oppose an amendment banning Japanese American Doctor Fujikawa from practicing medicine in the State Tubercular Sanatorium. Armstrong states that Dr. Fujikawa chose to leave the relocation center because his services were needed in the State Sanatorium, that without his assistance, 150 tubercular patients would be sent home. Armstrong mentions bravery of Japanese American combat regiment fighting in Italy and condemns racism and discrimination of Japanese Americans, stating "Dr. Fujikawa is not responsible for our war with Japan. For that matter the people of the Japanese Empire had no voice in their destiny, no control over the mad warlords who launched the attack at Pearl Harbor." He strongly opposes amendment preventing Dr. Fujikawa from practicing medicine both as an outcry against discrimination, and in support of Dr. Fujikawa, whose services are needed in the state of Missouri.The War Relocation Authority (WRA), together with the Wartime Civil Control Administration (WCCA), the Civil Affairs Division (CAD) and the Office of the Commanding General (OFG) of the Western Defense Command (WDC) operated together to segregate and house some 110,000 men women and children from 1942 to 1945. The collection contains documents and photographs relating to the establishment and administrative workings of the (WDC), the (WRA) and the (WCCA) for the year 1942
Leadership perceptions of third grade students based on both gender of the leader and gender of the student
No full textPlan BThe purpose of this study was to determine the relationship between the gender of third grade students at Longfellow Elementary and their rating of perceived leadership effectiveness of both males and females as measured by the Kapanke-Sproul scale. The subjects for this study were all of the third grade students at Longfellow Elementary School. This study utilized four pictures with written narrative descriptions attached. The students were each given a packet of four pictures with written narrative descriptions. Each packet contained an effective male leader, an effective female leader, an ineffective male leader, and an ineffective female leader. Half of the students received a picture of a male described as an effective leader while the other half of the students received a picture of a female with the same written description. Next, half of the students received a picture of a female with the description of an effective leader, and the other half of the students received a picture of a male with the same written description. Thirdly, half of the class was given a picture and written description of an ineffective male leader, while the other half of the students were given a picture of a female with the same written description. Lastly, half of the class was given a picture of a female with the a written description of an ineffective leader, and the other half of the class was given a picture of a male with the same written description. At the bottom of each written narrative description there were two questions, and the students were asked to rate their perception of effective leadership ability for each individual on a "Likert Scale." The results were analyzed to determine if gender of the leaders affected how they were perceived by the students. The results were also analyzed to determine if gender of the student affected whether males or females were perceived to be more effective leaders To this researcher's surprise, none of the findings were statistically significant. When looking at the raw data, it appeared that male students perceived male leaders as more effective and female students perceived female leaders to be more effective, but when the data was analyzed this was not the case. The data analysis showed that generally, males and females are perceived as equally effective, regardless of the gender of the student or the leader. The collective findings of this study resulted in the conclusion to accept the Null Hypothesis that there is no statistically significant difference in perceived leadership effectiveness of adult males versus females based upon gender of the third grade students. It is important to study gender issues to help understand what still needs to change to help eliminate sex-role stereotypes in society, occupations, and leadership roles. This information was used to make suggestions for future guidance curriculum to ensure gender equality
Exploring Scintillometry in the Stable Atmospheric Surface Layer
No full textThe main objective of this thesis is to investigate observation methods of heat and momentum exchange and key variables that characterise turbulence in the atmospheric stable surface layer (SSL), a layer defined as the lower part of the stable boundary layer (SBL) where surface fluxes do not change significantly with height. The SBL is often confined to a shallow layer above the surface and is often intermittent, i.e. quiescent periods with almost laminar flow are interchanged with turbulent bursts. These conditions complicate surface flux measurements considerably, since ideally these then need to take place close to the surface and over short flux averaging intervals. Scintillometers, unlike traditional flux measurement techniques such as eddy covariance (EC), can be operated just above the surface (< 1 m) and over short flux averaging intervals (< 1 minute). These features have led us to explore in more detail the applicability of scintillometers in the SSL.Two types of scintillometers will be considered, notably the displaced-beam small-aperture scintillometer (DBSAS) and the large-aperture scintillometer (LAS) deployed in three field campaigns we contributed to as part of this thesis: RAPID in Idaho, USA, (1999), CASES-99 in Kansas, USA (1999) and BBC in Cabauw, the Netherlands (2001). In addition, an old data-set is analysed with LAS data gathered during the La Poza experiment in Sonora, Mexico (1996).The DBSAS and the LAS are optical instruments that consist of a transmitter and a receiver. The receiver records intensity fluctuations of the light beam emitted by the transmitter, which are caused by refraction of the beam upon its passage through the turbulent surface layer. These intensity fluctuations are a measure of the structure parameter of temperature,C T2. The DBSAS obtains also the dissipation rate of turbulent kinetic energy,e, from the correlation between the two displaced beams. In itself, these quantities are important properties of turbulence. Moreover, when the flow is turbulent they are related to the turbulent fluxes of sensible heat, H , and momentum,t, usually expressed by the velocity scale u * , by virtue of Monin-Obukhov similarity theory (MOST).The DBSAS is the most suitable scintillometer to be used in the SBL, since it gives a measure of the mechanically induced turbulence (i.e.e), which is the only turbulence generating mechanism in stable conditions. For the LAS - that does not measuree- the mechanical turbulent transport is usually included using wind speed measurement and an estimate of the roughness length.Several detailed aspects of the application of scintillometry and EC in obtaininge, C T2 , H andtare discussed. The most general aspects presented are the following. For CASES-99 and BBC we compared the DBSAS performance against EC in obtaininge, C T2 , H andtover a wide range of stable conditions and conclude that the DBSAS is superior in obtaining turbulence information over short intervals with remarkably little scatter, but that the derived parameters contain systematic errors. When corrected for the systematic errors (using ad-hoc solutions) the DBAS appears to provide accurate C T2 ,eand resulting H , andtfor short time intervals and close to the ground. In addition, for the BBC we also investigated the LAS and combinations of LAS and DBSAS to jointly solveeand C T2 for both stable and unstable conditions. Furthermore, for CASES-99 we derived new MOST relations foreand C T2 and show how these can be used to evaluate the MOST relations for dimensionless wind speed and temperature gradients. Also, alternative scaling parameters based oneand C T2 are introduced. Last, we investigated an important practical aspect of the scintillometer application, i.e. what effective height to use to calculate H when the beam-height of the instrument varies along the path. This is done based on a data-set from the La Poza experiment in Sonora, Mexico (1996)
Exploitation of homogeneous isotropic turbulence models for optimization of turbulence remote sensing
No full textHomogeneous isotropic turbulence (HIT) models are compared, with respect to optimization of turbulence remote sensing. HIT models have different applications such as load calculation for wind turbines (Mann, 1998) or droplet track modelling (Pinsky and Khain, 2006). Details of vortices seem of less relevance for modelling `realistic measurements', where the single purpose is to retrieve the eddy dissipation rate (EDR). Without the need for modelling the vortices, a faster and simpler approach might be favorable. The cascade turbulence model (CTM) is suggested. The CTM solution is scale invariant and a fast solution for one-dimensional HIT modelling. In this presentation modelled radar measruments for scanning mode (rotating antenna) are compared for different HIT models. The consequences for turbulence remote sensing optimization are discussed
Variance Method to Determine Turbulent Fluxes of Momentum And Sensible Heat in The Stable Atmospheric Surface Layer
No full textEvidence is presented that in the stable atmospheric surface layer turbulent fluxes of heat and momentum can be determined from the standard deviations of longitudinal wind velocity and temperature, ¿u and ¿T respectively, measured at a single level. An attractive aspect of this method is that it yields fluxes from measurements that can be obtained with two-dimensional sonic anemometers. These instruments are increasingly being used at official weather stations, where they replace the standard cup anemometer-wind vane system. With methods such as the one described in this note, a widespread, good quality, flux network can be established, which would greatly benefit the modelling community. It is shown that a 'variance' dimensionless height (¿¿) defined from ¿uand ¿Tis highly related to the 'conventional' dimensionless stability parameter ¿ = z/L, where is height and L is the Obukhov length. Empirical functions for ¿¿ are proposed that allow direct calculation of heat and momentum fluxes from ¿u and ¿F. The method performs fairly well also during a night of intermittent turbulence
Displaced-beam small aperture scintillometer test: CASES-99 stable boundary layer experiment
No full textIn this study we investigated the performance of a displaced-beam small aperture scintillometer (DBSAS) - operated over a path length of 112 m - under stable conditions using data gathered during the CASES-99 experiment in Kansas, USA. The DBSAS has the advantage over the eddy covariance method that it can determine fluxes of sensible heat and momentum close to the surface and/or over short (< 1 minute) averaging intervals. Both aspects are of importance in the often shallow and non-stationary stable boundary layer (SBL). From raw DBSAS measurements the dissipation rate of turbulent kinetic energy and the structure parameter of temperature can be deduced, which follow Monin-Obukhov similarity theory (MOST) to give the friction velocity, u* the temperature scale, T* and subsequently the sensible heat flux, H. All these variables were compared with eddy covariance data for 10-minute time averages. Systematic errors were found for the DBSAS u*; i.e. overestimation for low u* values and underestimation for high u* values. It seems these errors cannot be attributed to the use of MOST, since they are already present in the dissipation rate data. In determining the dissipation rate, a form of the temperature spectrum in the dissipation range has to be assumed. The way the DBSAS weights this spectrum will be discussed. Furthermore, the sensitivity of the DBSAS method to small off-sets in instrumental parameters will be discussed. It was found that an adjustment of the beam displacement distance, d that is within the accuracy at which d is determined, removes some of the systematic errors. This adjustment is presented as a working hypothesis, not a general solutio
Monin-Obukhov Similarity Functions of the Structure Parameter of Temperature and Turbulent Kinetic Energy Dissipation Rate in the Stable Boundary Layer
No full textThe Monin-Obukhov similarity theory (MOST) functions fepsi; and fT, of the dissipation rate of turbulent kinetic energy (TKE), ¿, and the structure parameter of temperature, CT2, were determined for the stable atmospheric surface layer using data gathered in the context of CASES-99. These data cover a relatively wide stability range, i.e. ¿ = z/L of up to 10, where z is the height and L the Obukhov length. The best fits were given by f¿ = 0.8 + 2.5¿ and fT= 4.7[1 + 1.6(¿)2/3], which differ somewhat from previously published functions. ¿ was obtained from spectra of the longitudinal wind velocity using a time series model (ARMA) method instead of the traditional Fourier transform. The neutral limit f¿ = 0.8 implies that there is an imbalance between TKE production and dissipation in the simplified TKE budget equation. Similarly, we found a production-dissipation imbalance for the temperature fluctuation budget equation. Correcting for the production-dissipation imbalance, the 'standard' MOST functions for dimensionless wind speed and temperature gradients (Øm and Øh) were determined from f¿ and compared with the Øm and Øh formulations of Businger and others. We found good agreement with the Beljaars and Holtslag [J. Appl. Meteorol. 30, 327-341 (1991)] relations. Lastly, the flux and gradient Richardson numbers are discussed also in terms of f¿ and fT
Evaporation in the Atacama Desert
No full textUnderstanding evaporation in arid regions is essential for climate change assessment and optimizing water resources management under a changing climate. This thesis analyses the physical processes that govern local evaporation in a representative salt flat setting at the Altiplano region of the Atacama Desert. Such physical processes are analyzed from climatic to sub-diurnal scales. Moreover, regional (>100 km) to local (<1 km) scales are integrated, through the analysis of the ocean-desert circulation and its influences on the atmospheric boundary layer and surface fluxes. Firstly, findings show that wind-driven turbulence is the primary evaporation controller at the sub-diurnal scale, whereas radiation plays a major role at the seasonal scale. Secondly, at the local scale, surface fluxes are mainly controlled by mechanical turbulence, which is only present in the afternoon due to a regional-scale flow resulting from the thermal contrast between the cool Pacific Ocean and the warm Atacama Desert. Thirdly, the regional flow that triggers evaporation in the Altiplano origins from the marine boundary layer, whose stability regime dominates the formation of fog and the inland moisture transport. Finally, the role of surface heterogeneity on turbulent fluxes measurements is quantified at the sub-kilometer scale, where footprint and MOST functions play an important role. This thesis contributes to untangling and linking processes driving evaporation from local to regional-scale and from sub-diurnal to inter-annual scale, across confined saline lakes in arid regions
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