A View of Jerry Meehl's Work on Multiscale Interactions in the Climate System

I first met Jerry in the early 1980s when we were both graduate students at the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado. In those days, prior to the internet, Jerry and Marla (now his wife) would often spend a weekend day (or two) at the Mesa Lab, where we could run our punchcard programs on the Cray 1A mainframe. Even then, Jerry had very diverse interests, including a focus on tropical and Southern Hemisphere climate variability, undoubtedly due in part to the influence of Harry van Loon. Jerry and I were both involved in the TOGA COARE field program, based out of Townsville, Australia. Participating in daily map discussions for mission planning purposes, we got to see the direct impact of synoptic and intraseasonal scale events on the ocean, and in particular, the equatorial "westerly wind bursts" (WWBs). These intriguing events led us (with Klaus Weickmann) to examine the synoptic scale forcing mechanisms that generated these episodes in a 1994 Journal of Geophysical Research paper, using NMC global analyses, a precursor to reanalysis. We found that high pressure surges from Asia associated with the intraseasonal Madden-Julian Oscillation (MJO) and higher frequency (6-30 day) synoptic scale events forced a large fraction of WWBs, along with lower tropospheric cyclone pairs on either side of the equator, which are now known to be associated with equatorial Rossby waves. That study was also motivated by a Monthly Weather Review survey of the synoptic scale activity during COARE led by Dave Gutzler that we participated in, where we saw how important the MJO was to the late December 1992 and February 1993 WWBs that were very well observed by the field observations. That paper was then followed up by a 1996 study led by Jerry, also published in JGR, where we attempted to statistically link tropical convective activity over the western tropical Pacific to extratropical forcing using several years of NMC and ECMWF analyses, as a comparison to events observed during COARE. I believe that this series of highly cited papers helped raise awareness within the community of how important extratropical forcing of the tropics could be on intraseasonal and subseasonal time scales. Since one of Jerry’s primary interests is climate variability, he then went on to lead a review of how such tropical processes could influence global climate in a 2001 Climate Dynamics paper, which focused on time and space scale interactions between El Nino and subseasonal phenomena, and their potential role in lower frequency climate variability out to decadal time scales. In this presentation I will review more recent developments in this area, highlighting the role that Jerry has played as a scientist who has been highly motivated to consider the wide range of scales involved in climate variability in both observations and models.

References

Kiladis, G. N., G. A. Meehl, and K. M. Weickmann, 1994: Large-scale circulation associated with westerly wind bursts and deep convection over the western equatorial Pacific. J. Geophys. Res., 99, 18,527-18,544.

Gutzler, D. S., G. N. Kiladis, G. A. Meehl, K. M. Weickmann, and M. Wheeler, 1994: The global climate of December 1992-February 1993. Part II: Large-scale variability across the tropical western Pacific during TOGA COARE. J. Climate, 7, 1606-1622.

Meehl, G. A., G. N. Kiladis, K. M. Weickmann, M. Wheeler, D. S. Gutzler, and G. P. Compo, 1996: Modulation of equatorial subseasonal convective episodes by tropical extratropical interaction in the Indian and Pacific Ocean regions. J. Geophys. Res., 101, 15,033-15,049.

Meehl, G. A., R. Lukas, G. N. Kiladis, K. M. Weickmann, A. J. Matthews, and M. Wheeler, 2001: Time and space scale interactions in the climate system: Implications for climate variability and predictability, Climate Dyn. 17, 753-775.