Climate Dynamics

, Volume 31, Issue 5, pp 551–571 | Cite as

Extension and Intensification of the Meso-American mid-summer drought in the twenty-first century

  • Sara A. Rauscher
  • Filippo Giorgi
  • Noah S. Diffenbaugh
  • Anji Seth


Recent global-scale analyses of the CMIP3 model projections for the twenty-first century indicate a strong, coherent decreased precipitation response over Central America and the Intra-America Seas region. We explore this regional response and examine the models’ skill in representing present-day climate over this region. For much of Central America, the annual cycle of precipitation is characterized by a rainy season that extends from May to October with a period of reduced precipitation in July and August called the mid-summer drought. A comparison of the climate of the twentieth century simulations (20c3m) with observations over the period 1961–1990 shows that nearly all models underestimate precipitation over Central America, due in part to an underestimation of sea surface temperatures over the tropical North Atlantic and an excessively smooth representation of regional topographical features. However, many of the models capture the mid-summer drought. Differences between the A1B scenario (2061–2090) and 20c3m (1961–1990) simulations show decreased precipitation in the future climate scenario, mostly in June and July, just before and during the onset of the mid-summer drought. We thus hypothesize that the simulated twenty-first century drying over Central America represents an early onset and intensification of the mid-summer drought. An analysis of circulation changes indicates that the westward expansion and intensification of the North Atlantic subtropical high associated with the mid-summer drought occurs earlier in the A1B simulations, along with stronger low-level easterlies. The eastern Pacific inter-tropical convergence zone is also located further southward in the scenario simulations. There are some indications that these changes could be forced by ENSO-like warming of the tropical eastern Pacific and increased land–ocean heating contrasts over the North American continent.

Key words

Central America Climate change Mid-summer drought North Atlantic subtropical high 



We acknowledge the modeling groups for providing their data for analysis, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) for collecting and archiving the model output, and the JSC/CLIVAR Working Group on Coupled Modelling (WGCM) for organizing the model data analysis activity. The multi-model data archive is supported by the Office of Science, U.S. Department of Energy. We thank Dr. Xunqiang Bi for downloading and processing some of the data used in this analysis. We are grateful to Dr. David Enfield, Dr. Scott Curtis, Dr. Alessandra Giannini, Dr. Fred Kucharski, and three anonymous reviewers for their extremely helpful comments and enlightening discussion of this work.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Sara A. Rauscher
    • 1
  • Filippo Giorgi
    • 1
  • Noah S. Diffenbaugh
    • 2
  • Anji Seth
    • 3
  1. 1.Earth System Physics SectionThe Abdus Salam International Centre for Theoretical PhysicsTriesteItaly
  2. 2.Purdue Climate Change Research Center and Department of Earth and Atmospheric SciencesPurdue UniversityWest LafayetteUSA
  3. 3.Department of GeographyUniversity of ConnecticutCTUSA

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