Understanding the factors that influence temperatures in the tropical lower stratosphere is important for interpreting past climate variations and projecting future climate. The changes in the…

This federal contract award was granted by the National Aeronautics and Space Administration (NASA) Shared Services Center to the University of Washington (UW) as the prime contractor. The $541,669 grant will fund research to investigate the dynamically forced changes in tropical lower-stratospheric temperatures through the fusion of satellite data from the Earth Observing System (EOS) Aqua and Aura missions. The research aims to reconcile observational analyses and climate modeling studies on long-term changes in this region, provide an evaluation of observationally derived trends, and shed light on the discrepancy between models and observations. This grant is part of NASA's effort to "The Science of Terra, Aqua, and Suomi NPP" and aligns with the agency's Earth Science research objectives. The contract does not have a set-aside designation.

Understanding the factors that influence temperatures in the tropical lower stratosphere is important for interpreting past climate variations and projecting future climate. The changes in the tropical lower-stratospheric temperatures on decadal time scale are driven by the changes in radiatively active trace constituents as well as changes in dynamically forced upwelling. An important open scientific question is that, for a change in the tropical lower-stratospheric temperature driven by the upwelling changes there, how much temperature change is directly caused by the upwelling changes, and how much is indirectly a result of their effect on radiatively active constituents. A closely-related question is why the general circulation models (gcms) and chemistry-climate models (ccms) simulated a smaller tropical lower-stratospheric cooling than observations in the past 3-4 decades. The clouds from EOS aqua modis and temperature, O3, and H2O from EOS aura MLS provide the key measurements to investigate the dynamically forced change in tropical lower-stratospheric temperatures for its relative partitioning caused by the direct dynamic effect and the composition changes that are driven by the dynamics. The overall objective of this proposed project is to investigate the dynamically forced changes in tropical lower-stratospheric temperatures through the fusion of aqua/modis and aura/MLS measurements along with reanalysis data and radiation models. We will address the key scientific question that, for a change in tropical lower-stratospheric temperature driven by the upwelling changes there, how much temperature change is directly caused by the upwelling changes, and how much is indirectly brought about through their effect on radiatively active constituents. We will focus on the analyses of seasonal and interannual variability, which is largely caused by the upwelling changes associated with the extratropical and tropical/subtropical wave activities, respectively. The proposed project represents the first research effort to take into account the cloud radiative effects on the lower-stratospheric temperatures through both cloud climotological backgrounds and cloud changes, achieved though the fusion of the aqua modis and aura MLS observations with the radiation models. The data from modis will play a primary role in answering the scientific question addressed in the proposal. We will analyze the trends with available long-term datasets by applying the partitioning relations derived from seasonal and interannual variations. The proposed investigation will (i) reconcile the observational analyses and modeling studies on the long-term changes in the tropical lower-stratospheric temperatures in the past 3-4 decades, (II) provide a critical evaluation of observationally derived long-term trends in the tropical lower-stratospheric temperatures, O3 and H2O, and (III) shed light on the long-standing issue of smaller tropical lower-stratospheric cooling from gcms and ccms than observations. The proposed effort will directly contribute to "the science of terra, aqua, and suomi NPP" by "undertaking studies responsive to NASA, the science mission directorate's science objectives, and the NASA earth science research objectives and providing answers to NASA's earth science research questions through the use of data and derived products from terra/aqua and their measurement sensors". IT will be part of "2.1 science data analysis" efforts in the tasnpp science "for analysis of terra and/or aqua and/or suomi NPP data to answer disciplinary, interdisciplinary, or multi-disciplinary earth science research questions". IT will also be responsive to 2.1.1 of the solicitation by "utilizing terra, aqua, and suomi NPP data in conjunction with appropriate data from other satellites" for "multimission and multisensor innovative research that can be used to quantify change, characterize processes, and examine function within the earth system over time".