Sunday, 22 January 2017
4E (Washington State Convention Center )
Overshooting convection is defined as convection that rises past the tropopause and into the stratosphere. This type of convection is typically associated with only the strongest storms on Earth. Quantifying overshooting convection on Earth is rather difficult, but previous studies have quantified it using various approaches. The tropopause level varies based on location, meaning convection could be able to shoot into the tropopause at one location, but not at another. Because of this, the tropopause must be calculated at every location; having a global mean tropopause will not be sufficient. This study aims to quantify the probability of tropopause-penetrating convection using the conservation of equivalent potential temperature as an air mass rises. Using ERA-Interim monthly mean data from 1979-2015, the seasonal mean (DJF, JJA) tropopause pressure levels across Earth are calculated based on the World Meteorological Organization (WMO) lapse-rate tropopause definition. The potential temperature (θtp) of the tropopause is then calculated. Surface-based equivalent potential temperature (θe) is calculated using six hourly temperature and specific humidity data from the ERA-Interim and is compared to the seasonal tropopause potential temperature. Places where θe exceeds θtp are considered to be places where tropopause-penetrating convection could have occurred. Current findings show “hot spots” of high θe values in northern India during JJA, where the Asian monsoon is prevalent. In DJF, there are areas in the deep tropics that have θe approaching θtp, also signifying areas of deep convection.
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