Can a regional climate model improve the ability to forecast the North American monsoon?

Christopher L. Castro, Hsin I. Chang, Francina Dominguez, Carlos Carrillo, Jae Kyung Schemm, Hann Ming Henry Juang

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

Global climate models are challenged to represent the North American monsoon, in terms of its climatology and interannual variability. To investigate whether a regional atmospheric model can improve warm season forecasts in North America, a retrospective Climate Forecast System (CFS) model reforecast (1982-2000) and the corresponding NCEP-NCAR reanalysis are dynamically downscaled with the Weather Research and Forecasting model (WRF), with similar parameterization options as used for highresolution numerical weather prediction and a new spectral nudging capability. The regional model improves the climatological representation of monsoon precipitation because of its more realistic representation of the diurnal cycle of convection. However, it is challenged to capture organized, propagating convection at a distance from terrain, regardless of the boundary forcing data used. Dynamical downscaling of CFS generally yields modest improvement in surface temperature and precipitation anomaly correlations in those regions where it is already positive in the global model. For the North American monsoon region, WRF adds value to the seasonally forecast temperature only in early summer and does not add value to the seasonally forecast precipitation. CFS has a greater ability to represent the large-scaleatmospheric circulation in early summer because of the influence of Pacific SST forcing. The temperature and precipitation anomaly correlations in both the global and regional model are thus relatively higher in early summer than late summer. As the dominant modes of early warm season precipitation are better represented in the regional model, given reasonable large-scale atmospheric forcing, dynamical downscalingwill add value to warm season seasonal forecasts. CFS performance appears to be inconsistent in this regard.

Original languageEnglish (US)
Pages (from-to)8212-8237
Number of pages26
JournalJournal of Climate
Volume25
Issue number23
DOIs
StatePublished - Dec 1 2012

Keywords

  • Climate prediction
  • Interannual variability
  • Mesoscale forecasting
  • Mesoscale models
  • Regional models

ASJC Scopus subject areas

  • Atmospheric Science

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