Physical,radiative, and dynamical processes within a nighttime marine stratus cloud

Observations taken by aircraft and conventional platforms are used to investigate dynamical, physical, and radiative processes within a marine stratus cloud during the Canadian Atlantic Storms Program (CASP) II field project which took place over the east coast of Canada. Stratus which formed over the ocean on February 6, 1992 during the nighttime, is studied to analyze cloud top and base processes. The cloud was supercooled during the study period. Fluctuations and fluxes are calculated along constant flight altitude legs approximately 100 km long in space. The scales of structures larger than 5 km are removed from the analysis using a running average technique. Droplet spectra obtained by a forward scattering spectrometer probe (FSSP) were used in a 1-D radiative transfer model to calculate infrared (IR) fluxes and radiative heating rates. A heat conservation equation was used to estimate vertical air velocity (w _a ) within the cloud. The results showed that, because of a warmer ocean surface, significant moisture and heat were transferred from the ocean surface to the boundary layer. The cloud base was at about 400 m height and the top was at about 1.4 km.w _a at the cloud base was estimated about 5 cm s^–1. Strong IR cooling rate at the cloud top was calculated to be 75°C day^–1 for a 100 m thick layer. Negative skewness inw _a , suggesting narrow downdrafts, was likely due to radiative cooling at the cloud top. The entrainment velocity was found to be about 1.5 cm s^–1 at cloud top. Mean moisture and heat fluxes within the cloud were estimated to be comparable to those from the ocean surface. Vertical air velocity at the cloud top due to radiative cooling was found to be about –40 cm s^–1.     

Cusp Modeling and Observations at Low Altitude

Cusp properties have been investigated with an open-field line particle precipitation model and Defense Meteorological Satellite Program (DMSP) satellite observations. Particular emphasis is placed on the effects of IMF B_y, since previous studies focus mostly on IMF B_z. The model-data comparisons for various IMF configurations show that the model captures the large-scale features of the particle precipitation very well, not only in the cusp region, but also in other open-field line regions such as the mantle, polar rain, and open-field line low-altitude boundary layer (LLBL). When the IMF is strongly duskward/dawnward and weakly southward, the model predicts the occurrence of double cusp near noon: one cusp at lower latitude and one at higher latitude. The lower latitude cusp ions originate from the low-latitude magnetosheath whereas the higher latitude ions originate from the high-latitude magnetosheath. The lower latitude cusp is located in the region of weak azimuthal E × B drift, resulting in a dispersionless cusp. The higher latitude cusp is located in the region of strong azimuthal and poleward E × B drift. Because of a significant poleward drift, the higher latitude cusp dispersion has some resemblance to that of the typical southward IMF cusp. Occasionally, the two parts of the double cusp have such narrow latitudinal separation that they give the appearance of just one cusp with extended latitudinal width. From the 40 DMSP passes selected during periods of large (positive or negative) IMF B_y and small negative IMF B_z, 30 (75%) of the passes exhibit double cusps or cusps with extended latitudinal width. The double cusp result is consistent with the following statistical results: (1) the cusp’s latitudinal width increases with |IMF B_y| and (2) the cusp’s equatorward boundary moves to lower latitude with increasing |IMF B_y|.     

Low ozone event at Madrid in November 1996

A sudden transient increase of the solar ultraviolet (UV) radiation was detected with a ground-based photometer in Madrid (Spain, 41°N, 3°W) on 25 November 1996 (Cordoba et al., 2000. UV-B irradiance at Madrid during 1996, 1997 and 1998. J. Geophys. Res. 105 (D4) (2000) 4903–4906). The data obtained by the TOMS satellite instrument revealed that this event was related to a reduction of the total ozone column values. This low ozone episode has been analysed. The ozone decrease was accompanied by a reduction of air temperature in the lower stratosphere. The anti-correlation between total ozone and air parcel height along the three-dimensional isentropic back-trajectories suggests that the adiabatic uplift of air contributed significantly to both the ozone and the temperature decreases observed. The uplift could be caused by the propagation into the lower stratosphere of the high-pressure cell located over the mid-Atlantic region.     

Airports and Environment: Proposal of Wastewater Reclamation at São Paulo International Airport

One way to reduce water consumption in urban areas is by using alternative sources of supply that can be provided by collecting rainwater and reusing wastewater for less restricted purposes. Thus, this study evaluated the characteristics of effluents produced by the wastewater treatment plant (WWTP) of São Paulo International Airport (SPIA), Brazil, in order to reuse it in non‐potable situations. The results achieved, indicated high efficiency in the biological system utilized by SPIA. The removal rates is equal to or >90% for most of the parameters analyzed, among them, fluoride, salinity, nitrite, nitrate, ammonium nitrogen, total nitrogen, phosphorus, sedimentable solids, turbidity, conductivity, apparent color, chemical oxygen demand, biochemical oxygen demand, total organic carbon, fecal coliforms, and oils and greases. Despite the final effluents were good enough to be launched in the local streams, they shall be submitted to a complementary treatment in order to fit some quality parameters to be reused for specific demands (landscape irrigation, toilet flushing, vehicle washing, fire fighting, and dust control).     

Observations of a Unique Cusp Signature at Low and Mid Altitudes

Observations of a unique cusp feature at low and mid altitudes are reported. This feature has a consistent double-peaked or “V”-shaped structure at the equatorward edge of high-latitude particle precipitation flux, and is predominantly present for high IMF B_y conditions. The observations are consistent with the Crooker (‘A split separator line merging model of the dayside magnetopause’, J. Geophys. Res. 90 (1985) 12104, ‘Mapping the merging potential from the magnetopause to the ionosphere through the dayside cusp’, J. Geophys. Res. (1988) 93 7338.) antiparallel merging model, which predicts a narrow wedge-shaped cusp whose geometry depends greatly on the dawn/dusk component of the IMF. Various observations are presented at low altitudes (DE-2, Astrid-2, Munin, UARS, DMSP) and at mid altitudes (DE-1, Cluster) that suggest a highly coherent cusp feature that is consistent with the narrow, wedge-shaped cusp of Crooker (1988), and contains persistent wave signatures that are compatible with previously reported high-altitude measurements. A statistical survey of Astrid-2 and DMSP satellite data is also presented, which shows this feature to be persistent and dependent on the IMF angle at the magnetopause, as expected. Thus, the cusp signatures observed at a wide range of altitudes present a coherent picture that may be interpreted in terms of a footprint of the magnetopause current layer.     

再生混凝土的低温抗震性变化对比分析

再生混凝土作为建筑材料在被使用前,需要对其低温抗震性能做出分析。但目前我国是全球新建筑数量最多的国家,再生混凝土成本低、需求量大,建筑方根据对普通混凝土的印象,直接将再生混凝土应用到建筑工程建设中,其中存在低温抗震性能不明确的问题。针对这个问题,提出再生混凝土的低温抗震性变化对比分析,通过再生混凝土的材料配比及实验搭建设计再生混凝土低温抗震结构模型。根据其指标对其低温抗冻性能、加速度变化、损伤指标、刚度稳定性、层位移变化等几个方面进行变化对比分析。对比实验结果表明:再生混凝土当含气量在逐渐降低时,其保温效果降低,强度在降低,抗冻性也在降低,耐久性和稳定性较差,并且在地震后楼层间的位移和加速度变化较大,不能保证楼层的稳定性;位移角无法降低到最小;随着位移和负载地震力不断增加,再生混凝土逐渐产生开裂变化,刚度减小速度较快,刚度退化程度较大,低温抗震性能较差。     

膨胀土地区机场跑道的地基处理研究

为解决在膨胀土山区修建机场时跑道地基处理的问题,以安康地区膨胀土为研究对象,在对现行石灰改良膨胀土施工控制参数常用方法分析的基础上,进行膨胀土及石灰改良膨胀土的膨胀性能和强度的相关试验。研究结果表明:随着石灰掺量的增加,最优含水率增大,最大干密度减小,胀缩潜势呈降低趋势,石灰掺量与最大干密度呈非线性关系,在石灰掺量达到9%时有荷膨胀率变化的规律性很强;相同石灰掺量改良土的CBR与击实功、含水量等因素有关,并不随着压实系数增加而增大。掺加石灰的比例对石灰改良膨胀土的强度增长影响较大,石灰掺量9%时的CBR值明显大于其他掺量;相同压实系数下石灰掺量3%和6%改良膨胀土的压缩性比较接近,石灰掺量增加到9%时其压缩性明显降低。结合试验结果,提出用石灰改良膨胀土对跑道进行地基处理,并以膨胀性指标作为主要控制指标、强度指标作为验证指标来确定施工参数。     

Anomalous Variations of Ionosphere Associated with the Strong Earthquake at Pakistan-Iran Border at a Low Latitude Station Agra,India

In this paper, we analyze the TEC data for April 2013 observed at Agra station, India (geogr. lat. 27.2° N, long. 78° E) to examine the effect of earthquake of magnitude M = 7.8 which occurred on 16 April 2013 at Pakistan–Iran border region. We process the TEC data using the s statistical criterion to find out anomalous variation in TEC data. We also study the VLF propagation signal from NPM, Hawaii (21.42° N, 158° W), which is monitored at the same station (Agra station) in the light of this earthquake as well as solar flares. The nighttime fluctuation method is used to analyze the VLF data for the period of ±5 days from the day of earthquake (11–21 April 2013). The anomalous enhancements and depletions are found in TEC data on 1–9 days before the occurrence of event.     

Implementation of a Single-Column Model for Fog and Low Cloud Forecasting at Central-Spanish Airports

Operations at Central-Spanish airports are often, especially in winter, affected by visibility reduction. The Instituto Nacional de Meteorología (INM), the Spanish Weather Service, has developed a single-column model (SCM) in order to improve short-term forecasts of fog, visibility and low-clouds. The SCM, called H1D, is a one-dimensional version of the HIRLAM limited-area model. It is operationally run for three airports in the region: Madrid-Barajas, Almagro and Albacete-Los Llanos. Since SCMs cannot deal with horizontal heterogeneity, the terms that depend on the horizontal structure of the atmosphere are estimated from the outputs of the three-dimensional (3-D) model and introduced into the SCM as external forcings. The systematic analysis of the meteorological situations has evidenced the existence of a close relationship between fog formation and the presence of drainage winds in the region. Since the 3-D model docs not have the necessary resolution to correctly simulate the main features of the drainage flow caused by the complex topography in the proximity of Madrid-Barajas, it cannot provide the SCM with the correct forcings. This problem has been partially overcome through the introduction of a module that, under certain conditions, substitutes the values computed from the 3-D model outputs by others that are based on a conceptual model of the phenomenon and have been empirically derived from climatological knowledge. This module improves the H1D verification scores for the basic meteorological variables—wind, temperature and humidity—and reduces the false alarm rate in fog forecast.     

Identification of Mining Blasts at Mid- to Far-regional Distances Using Low Frequency Seismic Signals

—?This paper reports results from two recent monitoring experiments in Wyoming. Broadband seismic recordings of kiloton class delay-fired cast blasts and instantaneous calibration shots in the Black Thunder coal mine were made at four azimuths at ranges from 1° to 2°. The primary focus of this experiment was to observe and to explain low-frequency signals that can be seen at all azimuths and should routinely propagate above noise to mid-regional distances where most events will be recorded by International Monitoring System (IMS) stations.¶The recordings clearly demonstrate that large millisecond delay-fired cast blasts routinely produce seismic signals that have significant spectral modulations below 10?Hz. These modulations are independent of time, the azimuth from the source and the orientation of the sensor. Low-frequency modulations below 5?Hz are seen beyond 9°. The modulations are not due to resonance as they are not produced by the calibration shots. Linear elastic modeling of the blasts that is guided by mine-blast reports fails to reproduce the fine detail of these modulations but clearly indicates that the enhanced “spectral roughness” is due to long interrow delays and source finiteness. The mismatch between the data and the synthetics is likely due to source processes, such as nonlinear interactions between shots, that are poorly understood and to other effects, such as variations of shot time and yield from planned values, that are known to be omnipresent but cannot be described accurately. A variant of the Automated Time-Frequency Discriminant (Hedlin, 1998b), which uses low-frequency spectral modulations, effectively separates these events from the calibration shots.¶The experiment also provided evidence that kiloton class cast blasts consistently yield energetic 2–10 second surface waves. The surface waves are strongly dependent on azimuth but are seen beyond 9°. Physical modeling of these events indicates that the surface waves are due mainly to the extended source duration and to a lesser extent to the slap-down of spalled material. The directionality is largely a path effect. A discriminant that is based on the partitioning of energy between surface and body waves routinely separates these events from the calibration shots.¶The Powder River Basin has essentially no natural seismic activity. How these mining events compare to earthquake observations remains to be determined.     

Inferring Low Cloud Base Heights at Night for Aviation Using Satellite Infrared and Surface Temperature Data

A nighttime image product that depicts areas of the lowest cloud base heights has been developed by combining brightness temperature data from the Geostationary Operational Environmental Satellite (GOES) Imager InfraRed (IR) bands centered at 3.9 μm and 10.7 μm, with hourly shelter temperatures from surface observing sites and offshore marine buoys. A dependent data sample showed a good correlation between the surface temperature minus IR cloud top temperature differences versus measured cloud base heights. Histogram analysis indicated that a temperature difference of less than 4-C related to a > 50% frequency of ceilings below 1000 ft above ground level, the threshold for Instrument Flight Rules (IFR). Using this result as a model, an experimental Low Cloud Base image product was developed that highlights regions of likely IFR ceilings. Validation of the Low Cloud Base product for two separate periods resulted in Probabilities of Detection of 67% and 72% and False Alarm Rates of 6% and 11%, respectively. Some regional variation observed could be related to the relative frequency of multi-layered overcast conditions. The biggest factor leading to underdetection of IFR ceilings by the GOES Low Cloud Base product is the presence of overlying clouds, including thin cirrus contamination. The GOES Low Cloud Base product shows potential for use as guidance for aviation meteorologists over both continental and marine areas.     

Assessment of Water Quality in the Elbe River at Low Water Conditions Based on Factor Analysis

An assessment of water quality measurements during a long‐lasting low water period in the Elbe River is presented. Weekly samples were taken from May to December 2003 at a sampling site in the middle part of the Elbe River. For multivariate data analysis, 34 parameters of 46 samplings were considered. As a result of this analysis, 78% of the variance of the data set is explained by five factors. They can be assigned to the following latent variables: season (37.5%) > tributaries (12.7%) > re‐suspension (10.4%) > discharge (9.4%) > complexation (8.5%). For the investigated sampling site, two key processes were identified as dominating factors on the water quality during low water conditions. First, seasonal phytoplankton development caused changes in redox conditions with consequences for re‐solution of pollutants from sediments. Second, tributaries have a higher impact on the main stream, due to changes in mixing processes. Therefore, in addition to flood investigations, monitoring strategies, and management plans should be developed in order to survey changes in water quality during low water conditions.     

昆明新机场岩溶漏斗地基处理试验研究

昆明新机场飞行区共发育岩溶漏斗234个,密度高达11.9个/km2,若处理不当势必引起后期的沉降问题和地基稳定性问题.选择有代表性的试验区进行不同的岩溶漏斗处理,并对处理前后的试验区进行原位波速测试、标准贯入试验、载荷试验等对比研究.试验结果表明:采用3 500 kN·m、4 500 kN·m务击能的强夯置换法处理岩溶...     

The performance of constructed wetlands for,wastewater treatment: a case study of Splash wetland in Nairobi Kenya

The performance of a constructed wetland for wastewater treatment was examined for four months (December 1995 to March 1996). The study area, hereby referred to as the Splash wetland, is approximately 0·5 ha, and is located in the southern part of Nairobi city. Splash wetland continuously receives domestic sewage from two busy restaurants. Treated wastewater is recycled for re‐use for various purposes in the restaurants. Both wet and dry season data were analysed with a view of determining the impact of seasonal variation on the system performance. The physical and chemical properties of water were measured at a common intake and at series of seven other points established along the wetland gradient and at the outlet where the water is collected and pumped for re‐use at the restaurants. The physico‐chemical characteristics of the wastewater changed significantly as the wastewater flowed through the respective wetland cells. A comparison of wastewater influent versus the effluent from the wetland revealed the system's apparent success in water treatment, especially in pH modification, removal of suspended solids, organic load and nutrients mean influent pH = 5·7 ± 0·5, mean effluent pH 7·7 ± 0·3; mean influent BOD₅ = 1603·0 ± 397·6 mg/l, mean effluent BOD₅ = 15·1 ± 2·5 mg/l; mean influent COD = 3749·8 ± 206·8 mg/l, mean effluent COD = 95·6 ± 7·2 mg/l; mean influent TSS = 195·4 ± 58·7 mg/l, mean effluent TSS = 4·7 ± 1·9 mg/l. As the wastewater flowed through the wetland system dissolved free and saline ammonia, NH₄⁺, decreased from 14·6 ± 4·1 mg/l to undetectable levels at the outlet. Dissolved oxygen increased progressively through the wetland system. Analysis of the data available did not reveal temporal variation in the system's performance. However, significant spatial variation was evident as the wetland removed most of the common pollutants and considerably improved the quality of the water, making it safe for re‐use at the restaurants. Copyright © 2001 John Wiley & Sons, Ltd.