Tropical Cyclone Intensification
Research funded by NASA focuses on improving our understanding of the processes that differentiate between tropical cyclones that intense hurricanes versus those that remain modest in intensity. Using aircraft and satellite datasets with high-resolution ensemble model simulations, a hypothesis that increased symmetry in rainfall around the center of the cyclone is a key factor in this determination is being tested, along with the potential that it is more important than the intensity of the deep convection in the cyclone.
Convective Precipitation Systems and Environments
Further research funded by NASA has focused on characterizing the properties of deep convective systems around the world using radar and radiometer data from the TRMM and GPM satellites, and the University of Utah TRMM/GPM Precipitation Feature Database. Extreme storms, from convective intensity, rain rate, and size perspectives, are a particular focus because of their impact on society. We are working to better understand their connection to large-scale environmental thermodynamic and kinematic conditions, processes that organize scatter storms into contiguous large systems that produce more lightning and are longer lived, and whether retrievals of their properties by satellite are biased by assumptions made in retrieval algorithms.
High Resolution Model Evaluation and Improvement
Research funded by DOE has focused on evaluating and improving high-resolution simulations of deep convective systems around the world by using in situ and remote sensing measurements from field campaigns. Previous work has established significant biases in both convective intensity and parameterizations of cloud particle properties and microphysical processes. Recent work has focused on the impacts of model resolution and microphysics representation on feedbacks between precipitation, cold pools, and mesoscale inflows and outflows that significantly impact system evolution, while the impact of newly developing novel microphysics parameterization methods on convective clouds are also being tested.
High Ice Water Content Production and Detection
Research funding from NSF has led to a better understanding of high ice water content regions with low radar reflectivity in deep convective cloud systems that can present hazards to commercial aircraft. Our research aims to improve detection and methods of avoidance of these regions. It also involves identifying the cloud processes that produce these regions of numerous, small ice particles and improving their representation in models. Additionally, since 2006, our group has worked with the commercial aircraft radar division of Rockwell Collins, Inc., using the University of Utah Precipitation Feature database and our understanding of the variability of deep convective system properties around the world to assist them in designing their aircraft radar displays to adjust to this variability, better informing pilots of potential hazards.
Our group also actively participates in field campaigns around the world. Recent examples include NASA GPM satellite validation campaigns across the US, the HS3 and GRIP tropical cyclone campaigns, and the HAIC-HIWC project in Darwin, Australia and Cayenne, French Guiana. Upcoming projects include the DOE-supported CACTI and NSF-supported RELAMPAGO campaigns in Argentina. Dr. Varble is the PI of CACTI, which seeks to better understand the processes that control convective cloud properties including deep convective initiation and upscale growth so that parameterizations in climate models can be improved, while RELAMPAGO has more of a focus on understanding and predicting high impact weather in this region that is known to produce the tallest and largest deep convective systems in the world.