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An unrotated principal components analysis was carried out to establish the most representative modes for the joint variability between the heights of the upper and lower boundaries of cirrus clouds and three different mandatory levels (850, 500, and 100 hPa), and the associated stability of the troposphere over Buenos Aires. Discussion is limited to the first three most representative structures found, which consists of spatial patterns (or empirical orthogonal functions, EOFs) and their time-evolving coefficients (or principal components, PCs). EOF1shows a direct (indirect) mode that encompasses the cirrus slightly below (above) its mean position, with 500 and 100 hPa exhibiting a similar behaviour and 850 hPa acting the opposite way. EOF1is associated with above-normal stability (instability) for direct (indirect) modes (i.e. positive (negative) values of PC1). On a monthly average, this occurs in the austral winter (summer) months. Regarding EOF2, all three mandatory levels experience positive (negative) height anomalies in direct (indirect) modes and cirrus goes up (down) under mild stability (instability). Monthly averages show that PC2is approximately positive in summer and in early fall and negative the rest of the year. As to EOF3, it is characterized by a stability similar to that of EOF2, with direct (indirect) modes showing lowered (raised) cirrus and all three mandatory levels above (below) normal conditions; on a monthly basis, PC3is best described as having a semi-annual evolution, with maxima (minima) in March and October (January and August). Overall, EOF1has the highest stability or instability, depending upon the sign of PC1. These results are the first of their kind worldwide. [ABSTRACT FROM AUTHOR]

The article presents a study on the association between the standardized tropopause height anomalies (STHAs) and standardized 500 and 100-hectopascal (hPa) height anomalies based from their latitudinal heights. It says that the study utilized a FORTRAN program to compute the tropopauses which were obtained from significant levels. It mentions that using the empirical orthogonal functions (EOFs), it was revealed that tropopause height correlates with the temperature in the lower stratosphere.