Understading Upper Tropospheric and Lower Stratospheric Temperature Structure Variations over Tropical and Extratropical Precipitation Systems
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The upper troposphere and lower stratosphere (UTLS) is a coupling region in the atmosphere in which air typically has characteristics of both the troposphere and stratosphere. This region is distinct in radiation, dynamics, chemistry, and microphysics, and a strong connectivity amongst these different processes makes it highly susceptible to climate change. Stratosphere-troposphere exchange across the tropopause is an important bidirectional process influencing the chemistry of the UTLS. Deep convection plays a large role in this exchange through the direct convective injection of water vapor into the lower stratosphere, by enhancing thin cirrus cloud presence, and by modulating the ozone budget. Many of these processes are also influenced by the extremely low temperatures at these altitudes. Therefore, understanding the role convection plays in the heat budget of the UTLS is paramount in climate research. In this dissertation, firstly, the UTLS vertical temperature structure changes near deep convection are quantified throughout two tropical regions. Deep convection observed from the Tropical Rainfall Measuring Mission (TRMM) satellite is collocated with high vertical resolution temperature profiles from COSMIC GPS Radio Occultation (RO) satellites along with ERA-Interim reanalysis from 2007 to 2011. A distinct layered structure of upper tropospheric warm anomalies, tropopause-level cool anomalies, and lower stratospheric warm anomalies is observed. The amplitude of temperature anomalies increases for deeper convection, marked by higher 20 dBZ radar echo top heights or colder infrared cloud-top temperatures. UTLS diurnal temperature variation also increases in both regions near deep convection. Secondly, to further examine the relationship between convection and UTLS temperatures, precipitation systems with different sizes, depths, and surface types are analyzed within different synoptic environments throughout the extratropics. Precipitation features (PFs) observed by the Global Precipitation Measurement (GPM) satellite are collocated with nearby GPS RO temperature profiles from 2014 to 2017. PFs are classified as non-deep stratospheric intrusion (non-DSI; more likely to be related to thermodynamic instability) or deep stratospheric intrusion (DSI; related to strong dynamic effects on the tropopause through folding) using potential vorticity. Non-DSI PFs introduce a similar vertical UTLS temperature anomaly structure to the tropics, whereas DSI PFs are mainly associated with major cooling from the mid-troposphere to just above the tropopause. These warm and cool anomalies also display strong seasonal variations from the subtropics to the high latitudes. Additionally, small but deeper non-DSI PFs typically result in lower lapse rate tropopause (LRT) heights, whereas large size but shallower PFs lead to a higher LRT. On the other hand, DSI PFs are almost always associated with large LRT height decreases. Finally, the unique characteristics of the extratropical tropopause are analyzed by illustrating when and where bimodal tropopause height distributions occur and how they relate to different synoptic environments and the occurrence of double tropopauses within individual temperature profiles. Tropopause heights are calculated and analyzed seasonally using COSMIC GPS RO temperature profiles from 2006- 2017. Tropopause bimodality occurs within the subtropics (between 20°-40°) and a distinct seasonality is observed, with bimodality occurring most frequently in winter due to a stronger subtropical jet stream. The region with a bimodal tropopause distribution nearly overlaps with the region that experiences a high frequency of double tropopauses (DTs). DT occurrence frequency is highest in winter along the poleward edge of the bimodal band. However, when analyzing profiles with only a single tropopause identified, bimodality occurs much less frequently and is reduced in meridional extent. These results suggest that seasonal tropopause bimodality is caused by two different factors, as the occurrences of double tropopauses strongly influence the tropical side of the bimodal band while single tropopause profiles that are more tropical in nature strongly influence the poleward side. The results shown in this dissertation display the unique characteristics of the UTLS and the noteworthy impact that both tropical and extratropical precipitation systems have on its thermodynamic structure. Additionally, these results suggest there are intricate relationships between different types of precipitation systems and their properties to the types of temperature anomalies that they produce. This study will enhance the community’s understanding of both tropical and extratropical convection, stratosphere-troposphere exchange processes, and tropopause characteristics.