Barometer Simultaneous barometric readings from across a network of weather stations allow maps of air pressure to be produced, which were the first form of the modern weather map when created in the 19th century. Isobars, lines of equal pressure, when drawn on such a map, give a contour map showing areas of high and low pressure. Localized high atmospheric pressure acts as a barrier to approaching weather systems, diverting their course. Atmospheric lift caused by low-level wind convergence into the surface brings clouds and sometimes precipitation. The larger the change in pressure, especially if more than 3.5 hPa (0.1 inHg),
Atmospheric-pressure laser ionization atmospheric pressure (AP) ion source with APLI. In principle only the ionizing laser light has to be coupled into the existing ion source through UV transparent windows. Couplings with separation methods like Supercritical Fluid Chromatography (SFC) and Chip-Electrospray (Chip-ESI) have also been demonstrated with APLI. APLI is a selective ionization method, because the 1+1 REMPI ionization requires an adequate existing electronic intermediate state and both electronic transitions must be quantum mechanically allowed. UV tunability and discrete energy states of analyte allow improved ionization with reduced background signal. In particular polynuclear aromatic compounds fulfil the spectroscopic requirements for 1+1 REMPI, thus