Does the subtropical jet catalyze the midlatitude atmospheric regimes?

• Published in: Geophysical research letters Vol. 33; no. 6; pp. L06814 - n/a
• Main Authors: Ruti, Paolo M., Lucarini, Valerio, Dell'Aquila, Alessandro, Calmanti, Sandro, Speranza, Antonio
• Format: Journal Article
• Language: English
• Published: Washington, DC American Geophysical Union 01.03.2006; Blackwell Publishing Ltd
• Subjects: Atmospheric Processes; Climate dynamics; Earth sciences; Earth, ocean, space; Exact sciences and technology; General circulation; Global Change; Nonlinear Geophysics; Probability distributions, heavy and fat-tailed; Tides and planetary waves; atmosphere; Mid latitude; detection; Weather forecast; strength; Critical parameter; Variability; exhibits; climate; indicators; troposphere; low frequency; Dynamical climatology; climate modification; Winter; Northern Hemisphere; Probability density function; Jet; Planetary wave; theory; statistics
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2005GL024620

Understanding the atmospheric low‐frequency variability is of crucial importance in fields such as climate studies, climate change detection, and extended‐range weather forecast. The Northern Hemisphere climate features the planetary waves as a relevant ingredient of the atmospheric variability. Several observations and theoretical arguments seem to support the idea that winter planetary waves indicator obey a non‐Gaussian statistics and may present a multimodal probability density function, thus characterizing the low‐frequency portion of the climate system. We show that the upper tropospheric jet strength is a critical parameter in determining whether the planetary waves indicator exhibits a uni‐ or bimodal behavior, and we determine the relevant threshold value of the jet. These results are obtained by considering the data of the NCEP‐NCAR and ECMWF reanalyses for the overlapping period. Our results agree with the non‐linear orographic theory, which explains the statistical non‐normality of the low‐frequency variability of the atmosphere and its possible bimodality.