Multivariate Tropical Variability from Microwave Satellite Data Records

Abstract:

Satellite observations provide great insight into processes that regulate the variability of atmospheric variables related to moist dynamics, from daily to decadal scales. Here we will focus on a long and accurately calibrated suite of satellite data records covering more than 3 decades. The satellite observations include the latest generation of geophysical retrievals coming from an extensive network of satellite microwave radiometer and scatterometers, dating back to 1987. These observables include Sea Surface Temperature, surface wind, columnar water vapor, cloud water, and precipitation. These variables are simultaneously measured using different combinations of frequency channels: they represent independent and unconstrained measurements, yet they are consistent with each other.

We will describe the observed variability in the Pacific at a wide range of time scales, from seasonal to decadal. Our study period includes two major El Nino events along with several moderate ENSO events, with different flavors, major phase transitions of the Pacific Decadal Oscillation, and a significant fraction of the anthropogenic warming. For each observable, the major modes of variability and patterns are extracted with EOF decompositions. Among these variables, columnar water vapor will be explored in great detail: it is the most accurate among the satellite measurements, and provides insights into atmospheric dynamical and thermodynamical processes, yet has not received the deserved attention.

Our analyses will address the following issues: What drives the columnar water vapor variability? How are the main modes of variability for all the different variables correlated with each other? Is there evidence for causality from the observed relationships? How are modes of variability in the Pacific basin related to variability in the Atlantic and Indian ocean basins? What is the contribution of interannual variability to the observed decadal scale changes?