Climate Seminar Series presents...
Moisture Surges Over the Gulf of California and their Relationship to Convective Activity
John Freddy Mejia
The University of Oklahoma School of Meteorology
20 November 2008, 2:00 PM
National Weather Center, Room 3902
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK
Directions to the NWC (.pdf, 60 kb)
The North American Monsoon (NAM) is characterized by widespread convective activity and rainfall that is tied to key synoptic and sub-synoptic atmospheric circulation features during summer. The core monsoon region, over NW Mexico, often experiences an atmospheric phenomenon recognized in the literature as a “Moisture Surge.” These moisture surges represent one of the most important sources of rainfall variability in the NAMS core region. In this seminar, I will show how moisture surges are linked to multiscale interaction of atmospheric processes ranging from mesoscale convective activity, typically in the form of mesoscale convective systems (MCSs), to larger-scale phenomena, ranging from synoptic-scale systems such as tropical easterly waves and eastern Pacific tropical storms to intraseasonal variations such as the 30-60 day Madden-Julian Oscillation (MJO).
The present research addresses these connections by using three different approaches. First, a detailed analysis of a well-observed moisture surge event that occurred during the North American Monsoon Experiment (NAME-2004) permits a unique four-dimensional description structure. Secondly, comprehensive climatological composites were generated using a multiyear set of surge events, historical satellite-estimated MCSs, the North American Regional Reanalysis products (NARR), and microwave scatterometer SeaWinds (QuikSCAT) data.
Finally, numerical simulation experiments using the Advance Research Weather and Research Forecasting (ARW V3.0) model focused on mesoscale convective processes under different synoptic-scale background flows.
Specifically, the ARW was run in a near-idealized mode where convective outflows were forced using cold bubbles. These cold bubbles emulated convective outflows resulting from real life MCS events.
Taken together, the results provide new insights into the nature of the GoC moisture surge variability and describe the influence of MCS’s in modulating the intensity of moisture surges and the GCLLJ.