A CASE STUDY OF THE UNCORRELATED RELATIONSHIP BETWEEN TROPICAL TROPOPAUSE TEMPERATURE ANOMALIES AND STRATOSPHERIC WATER VAPOR ANOMALIES

Abstract:

Using the measurements from the Halogen Occultation Experiment (HALOE) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim reanalysis data for the period 1994–C2005, we analyzed the relationship between tropical tropopause temperature anomalies and stratospheric water vapor anomalies. It is found that tropical tropopause temperature is correlated with stratospheric water vapor, i.e., an anomalously high (low) tropical tropopause temperature corresponds to anomalously high (low) stratospheric water vapor during the period 1994–C2005, except for 1996. The occurrence frequency and strength of deep convective activity during the ‘mismatched’ months is less and weaker than that during the ‘matched’ months in 1996. However, the instantaneous intensity of four short periods of deep convective activity, caused by strong surface cyclones and high sea surface temperatures, are greater during the ‘mismatched’ months than during the ‘matched’ months. Water vapor is transported from the lower troposphere to the lower stratosphere through a strong tropical upwelling, leading to an increase in stratospheric water vapor. On the other hand, deep convective activity can lift the tropopause and cool its temperature. In short, the key factor responsible for the poor correlation between tropical tropopause temperature and stratospheric water vapor in 1996 is the instantaneous strong deep convective activity. In addition, an anomalously strong Brewer–CDobson circulation brings more water vapor into the stratosphere during the ‘mismatched’ months in 1996, and this exacerbates the poor correlation between tropical tropopause temperature and stratospheric water vapor.