Amanda Maycock is working with Karen Rosenlof, David Fahey, Judith Perlwitz, Jennifer Kay, and others at the NOAA Earth System Research Laboratories to study the representation of the tropical tropopause layer (TTL) in global chemistry-climate models. The TTL is a region of the atmosphere between 14-18 km in the tropics that is distinguished by a combination of chemical, dynamical, physical and radiative characteristics from the troposphere below and the stratosphere above. Most air that is transported from the troposphere to the stratosphere passes through the TTL – the so-called ‘gateway’ to the stratosphere - and it is thus of central importance in the global chemistry-climate system. However, state-of-the-art global models show little convergence in representing TTL characteristics in the current climate, and exhibit large differences in the predicted response of the TTL to future changes in greenhouse gases. This source of uncertainty limits our ability to make accurate predictions of major environmental changes anticipated this century, such as ozone recovery and climate change. During her visit, Amanda will work with researchers to analyse key processes in current global models that may contribute to this uncertainty, and evaluate them against new observational datasets. The goal is for this to provide valuable new insights for developers and users of chemistry-climate models. After several short visits to Boulder in the past few years, Amanda is looking forward to an extended stay and having the opportunity to interact with the lively research communities at NOAA and CU.