Articles | Volume 8, issue 2
Clim. Past, 8, 535–544, 2012
Clim. Past, 8, 535–544, 2012

Research article 15 Mar 2012

Research article | 15 Mar 2012

A critical humidity threshold for monsoon transitions

J. Schewe1,2, A. Levermann1,2, and H. Cheng3,4 J. Schewe et al.
  • 1Earth System Analysis, Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany
  • 2Institute of Physics, University of Potsdam, 14476 Potsdam, Germany
  • 3Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an, 710049, China
  • 4Department of Geology and Geophysics, University of Minnesota, Minneapolis, 55455, USA

Abstract. Monsoon systems around the world are governed by the so-called moisture-advection feedback. Here we show that, in a minimal conceptual model, this feedback implies a critical threshold with respect to the atmospheric specific humidity qo over the ocean adjacent to the monsoon region. If qo falls short of this critical value qoc, monsoon rainfall over land cannot be sustained. Such a case could occur if evaporation from the ocean was reduced, e.g. due to low sea surface temperatures. Within the restrictions of the conceptual model, we estimate qoc from present-day reanalysis data for four major monsoon systems, and demonstrate how this concept can help understand abrupt variations in monsoon strength on orbital timescales as found in proxy records.