Variability of photosynthetic pigments in the Colombian Pacific Ocean and its relationship with the wind field using ADEOS-I data

Variability of the oceanographic conditions in the Colombian Pacific Ocean, a part of the Panama Basin, is subjected to the variability of wind conditions in the equatorial part of the Pacific Ocean. Data of OCTS and NSCAT of ADEOS-I satellite provided as monthly averages for the period November 1996-June 1997 by NASDA, were processed and manipulated. A meridional (N-S) component and a zonal (E-W) component were run in order to analyse the data variability and correlation. It is concluded that the variability of the oceanic surface chlorophyll and SST in the Colombian Pacific is a seasonal event related to the migration of the ITCZ and the generation of a wind jet at the Isthmus of Panama. Upwelling due to the wind rotor is present throughout the whole period, with variable spatial distribution and a tendency to be located towards the eastern part of the basin. In a similar way, high chlorophyll concentrations observed in March coincide with both the intensification of the vertical velocities during that month, and the maximal rise of the thermocline in the northern part of the Panama Basin. Picture series of surface chlorophyll, SST, wind stress and Ekman pumping are provided for the studied area.     

A new concept for high resolution temperature analysis over complex terrain

Summary The analysis of high resolution temperature data over complex topography is often problematic due to the specific influence of orography and thus, requires a special methodology. The new concept of Low Level Temperature (LLT) is defined, and can be obtained when potential temperature observations are reduced to the height of the so-called Minimum Topography, a special low level topography that accentuates basins and valleys but smoothes out single summits and scarped slopes. The Vienna Enhanced Resolution Analysis (VERA) is used to produce a comprehensive set of LLT analyses over the Alpine region by evaluating three-hourly synoptic ECMWF data for the period 1980–2001. LLT fields are then evaluated climatologically in order to gain two-dimensional representations and single grid point time series. Mean LLT fields for different months and times of the day provide highly resolved spatial and temporal information on temperature fields over basins and valleys i.e., the main settlement areas in mountainous terrain.     

Ion-Gas Interaction in a Vacuum Arc At Intermediate Pressures

Measurements of the ion flux as a function of the pressure in a plasma arc are presented. We report data on Ti and Pt cathodes using N₂ and Ar as the filling gases. Values of an effective collision cross section derived from the attenuation measurements are inferred.     

Probing FSR star cluster candidates in bulge/disc directions with 2MASS colour–magnitude diagrams

We analyse 20 star cluster candidates projected mostly in the bulge direction  (|ℓ| < 60°)  . The sample contains all candidates in that sector classified by Froebrich, Scholz & Raftery with quality flags denoting high probability of being star clusters. Bulge contamination in the colour–magnitude diagrams (CMDs) is in general important, while at lower Galactic latitudes disc stars contribute as well. Properties of the candidates are investigated with Two Micron All Sky Survey (2MASS) CMDs and stellar radial density profiles (RDPs) built with field star decontaminated photometry. To uncover the nature of the structures we decontaminate the CMDs from field stars using tools that we previously developed to deal with objects in dense fields. We confirm in all cases excesses in the RDPs with respect to the background level, as expected from the method the candidates were originally selected. CMDs and RDPs taken together revealed six open clusters, five uncertain cases that require deeper observations, while nine objects are possibly field density fluctuations.     

Colour gradients in globular clusters

Radial colour gradients in the globular clusters NGC 2808, NGC 1851, NGC 5139, NGC 5139, NGC 6388, NGC 6441, NGC 6541, NGC 6723, and NGC 7099 were searched byB-V and DDO photoelectric photometry, using a set of circular diaphragms. Two of the observed globular clusters, NGC 5139 (Cen) and NGC 7099 (M30), showedB-V and C(45–48) colour gradients; the colour C(42–45) is essentially constant in these clusters, which means that the physical reason for those gradients cannot be attributed to chemical composition variations, since C(42–45) is a good metal abundance indicator.B-V colours in the external regions of NGC 5139 and NGC 7099 were obtained by synthesizing the observed HR diagrams of these clusters. The ages and the relaxation times for NGC 5139 and NGC 7099 indicate that mass segregation must have taken place in both clusters, which is probably related to the observed colour gradients.