A Brief Introduction to CRU, GHCN, NCEP2, CAM3.5 Yi-Chih Huang

CRU (I) Gridded dataset produced by the Climate Research Unit at the University of East Anglia CRUTEM3 – Land surface temperature anomalies – Monthly since January 1850, on a 5x5 degree grid HadCRUT3 – A blend of CRUTEM3 and HadSST2 – Monthly since January 1850, on a 5x5 degree grid

CRU (II) TS3 – Variables: precipitation, wet-day frequency, mean temperature, diurnal temperature range, vapor pressure, sunshine, cloud cover, ground frost frequency – Monthly during 1901~2006 on a 0.5° × 0.5° grid

GHCN Global Historical Climatology Network Anomaly Method Monthly precipitation anomalies Monthly temperature anomalies X 5 degree grid

NCEP-DOE Reanalysis 2 (I) Monthly, Daily, Sub-Daily for 1979/1/ /12/31 An improved version of the NCEP/NCAR Reanalysis I – Same resolution as N/N Reanalysis: T62 L28 – Same raw observed data – Same dependence of satellite temperature retrievals Fixed known errors in N/N Reanalysis – S. H. PAOBs – Snow cover – Oceanic albedo – Discontinuities in radiation fluxes

NCEP-DOE Reanalysis 2 (II) Improved diagnostics – Snow/water budget – Cloud diagnostics field – Winter time precipitation, surface temp and fluxes in high latitudes – Tropical precipitation Some improvements in the assimilation system – Soil wetness, especially the interannual variations

NCEP-DOE Reanalysis 2 (III) Possible drawbacks – Overestimates OLR over warm pool – Equatorial upper level moisture much drier over convection area – Summer precipitation rates in Arctic region – Long term spin-down of soil wetness in polar latitudes

CAM3.5 (I) Community Atmospheric Model – 1.9x2.5 deg / 26 levels Separates parameterization suite from dynamical core Slab Ocean Model – Mixed layer temperature Thermodynamic sea ice model – Snow depth, surface temperature, ice thickness, ice fractional coverage, and internal energy

CAM3.5 (II) Lin-Rood finite volume dynamic core – Flux-form semi-Lagrangian scheme – Sub-cycling within the 2D Lagrangian dynamics Deep Convection – Convective momentum transports – Dilute plume calculation Cloud Fraction – Polar cloud freeze-drying