A comparison of temperature inversion statistics at a coastal and a non-coastal location influenced by the same synoptic regime

摘要

The primary aim of this work is to examine to what extent the climatology of atmospheric temperature inversions at one location is site specific, and to what extent it reflects a wider area for which the same synoptic conditions can be assumed. To this end radiosonde data from a coastal and a non-coastal location in eastern England separated by 210 km and influenced by the same synoptic conditions are used. Analysis of these data shows that there is a pronounced difference between the inversion climatologies at the two sites. The vertical distribution of base-heights of inversions has a very distinct maximum at a height of about 200 m at the location proximate to the coast. This maximum is not present at the inland location, and the difference is due to both sea-breezes and advection from the sea due to synoptic-scale wind field. Examining the vertical distributions of base-heights of inversions at the two locations under conditions that either maximize or minimize the effect of sea-breeze it is found that the differences in the two distributions are to a certain extent deterministic (therefore predictable) rather than random, as the dominant mechanisms which are responsible for these differences (diurnal and yearly cycles) have an obvious regularity. Using standard statistical methods it is further shown that, apart from this difference, nearly all other inversion statistics for the two locations are similar when the atmospheric layer from surface to 700 hPa is taken into consideration. However, when only the first inversion in each temperature profile is considered, the inversions activity throughout the year, defined with the aid of an index, in the two locations is not correlated, indicating that for the lowest part of the surface-700 hPa region, local factors overwhelm the synoptic conditions. Thus, these results provide evidence that the inversion climatology at one location can be generalised over a wider area where the same synoptic regime can be assumed. Given that, at least to an extent, any differences in the characteristics of inversions due to local factors can be inferred once the underlying mechanisms are carefully studied, this work has also important implications for micrometeorological studies as for instance the local diffusion and transport of air pollutans.