Introduction to special section: Regional climate modeling revisited

This paper provides an introduction to the special issue of the Journal of Geophysical Research on "New Developments and Applications With the NCAR Re gional Climate Model (RegCM)." In the first part of the paper we revisit an d discuss outstanding issues in regional climate modeling in view of the pr ogress achieved in this area of research during the last decade. We discuss issues of simulation length, spin-up, model physics, domain and resolution , lateral boundary conditions, multiple and two way nesting, and variable r esolution approaches. In the second part we introduce the papers included i n this issue. Among the primary model developments that occurred ill the la st few years are inclusions of the radiative transfer package and cumulus c onvection scheme from thee National Center for Atmospheric Research (NCAR) global model CCM3, a simplified explicit moisture scheme including direct i nteraction with cloud radiation, testing of a variable resolution model con figuration, improvements in the coupled lake model, and interactive couplin g with radiatively active atmospheric aerosols. The papers in the issue ill ustrate a wide range of applications over different regions, such as the Un ited States, East Asia, central Asia, eastern Africa. The main model limita tions and areas in need of improvement are indicated.