Airplane investigation of a case of convective cloud bands over the North Sea

During the experiment KONTROL 1985, an interesting case of prefrontal, nonprecipitating cloud bands parallel to the front at distances of about 25 km was observed over the North Sea. Spectral analysis of high frequency airplane measurements is discussed, putting special emphasis on the significance of the resulting spectral signals. A smaller scale roll circulation of a few kilometers wavelength mainly below cloud base could be inferred from these data. The rolls transport momentum downwards, but heat and moisture upwards into the cloud layer where transport is taken over by individual cloud elements. In addition, reasons for the existence, spacing and orientation of the larger scale cloud bands are discussed.     

Contrail frequency over Europe from NOAA-satellite images

Contrail cloudiness over Europe and the eastern part of the North Atlantic Ocean was analyzed for the two periods September 1979 - December 1981 and September 1989 - August 1992 by visual inspection of quicklook photographic prints of NOAA/AVHRR infrared images. The averaged contrail cover exhibits maximum values along the transatlantic flight corridor around 50 °N (of almost 2%) and over western Europe resulting in 0.5% contrail cloudiness on average. A strong yearly cycle appears with a maximum (<2%) in spring and summer over the Atlantic and a smaller maximum (<1%) in winter over southwestern Europe. Comparing the two time periods, which are separated by one decade, shows there is a significant decrease in contrail cloudiness over western Europe and a significant increase over the North Atlantic between March and July. Contrail cloud cover during daytime is about twice as high as during nighttime. Contrails are found preferentially in larger fields of 1000 km diameter which usually last for more than a day. Causes, possible errors and consequences are discussed.     

Kontur: Observations of cloud streets and open cellular structures

In September and October 1981 the experiment KonTur (Convection and turbulence) was conducted over the North Sea. Its objectives were to investigate organized convective patterns, like cloud streets (boundary layer rolls) and cellular cloud structures. Two aircraft (British Hercules C-130 and German Falcon 20) performed detailed measurements within these patterns. Several cases of cloud streets and open cells were observed.Boundary layer rolls appear to be connected with an inflection point in the cross-roll wind component. The aspect ratio of the rolls (wavelength versus depth) is between three and four in accordance with other observations and linear stability analysis. Four scales of motion are involved: the mean flow, the roll circulation, individual clouds and turbulence. The vertical transport are dominated at lower levels by turbulence and at higher levels by roll-scale motions.Open cellular cloud structures are connected with large air-sea temperature differences due to cold air outbreaks from the northwest. The aspect ratio of the cells is of the order of 10. The bulk contribution to the total transport of heat and momentum originates from the cloudy walls of the cells. A vertical cross section through a composite open cell is presented.     

Dissolution kinetics of natural magnesite in lactic acid solutions

In this study, the dissolution of magnesite particles in aqueous lactic acid solutions was investigated in a batch reactor employing the parameters of stirring speed, particle size, temperature and acid concentration. The shrinking core model was evaluated to determine the effect of particle size, temperature and concentration. It was also found that the stirring speed did not change the dissolution. Consequently, it was determined that the dissolution rate is controlled by surface chemical reaction. The activation energy of the process was determined to be 50.3 kJ mol^− 1.     

Water and sediment quality assessment in the mid-Black Sea coast of Turkey using multivariate statistical techniques

The aim of this study was to investigate the water and sediment quality in the mid-Black Sea coast of Turkey. The samples were collected from six stations during 2007. Investigated parameters were total carbon (TC), total inorganic carbon (TIC), total organic carbon (TOC), ammonium-nitrogen (NH₄-N), nitrate-nitrogen (NO₃-N), nitrite-nitrogen (NO₂-N), total phosphorus (TP), sulphate, total hardness, methylene blue active substances (MBAS), phenol, adsorbable organic halogens (AOX), dissolved oxygen (DO), pH and electrical conductivity (EC) in water samples and TC, TIC, TOC, TP, pH, electrical conductivity (EC), redox potential (Eh) and water content (WC) in sediment samples. Different multivariate statistical techniques were used to evaluate variations in surface water and sediment quality. Principal component analysis helped in identifying the factors or sources responsible for water and sediment quality variations. Five factors were found responsible for 87.63% of the total variance in the surface waters. In sediments, three factors explained 84.73% of the observed total variance. Cluster analysis classified the monitoring sites into two groups based on similarities of water and sediment quality characteristics.     

Persistent organochlorine residues in sediments along the coast of mid-Black Sea region of Turkey

The aim of this study is to determine aspects of water and surface sediment quality in the coastal zone of the mid-Black Sea, and of rivers discharging into it, by analyzing their organochlorine pesticides (OC) levels. Surface sediment samples and water samples were collected from 14 sites from the rivers Ye?ilirmak, Abdal, Mert, Kürtün, Engiz and Kizilirmak. In sediments, Aldrin ranged from 19.3 to 87.3 ng/g and p,p'-DDT ranged from 18.6 to 31.0 ng/g.