HR: 09:00h
AN: A21B-03 INVITED     [Abstracts]
TI: ERA-40 and Climate Variations
AU: * Uppala, S M
EM: Sakari.Uppala@ecmwf.int
AF: European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, RG2 9AX United Kingdom
AU: Simmons, A J
EM: Adrian.Simmons@ecmwf.int
AF: European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, RG2 9AX United Kingdom
AU: Kallberg, P W
EM: Per.Kallberg@ecmwf.int
AF: European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, RG2 9AX United Kingdom
AB: Reanalyses have brought an important multivariate component to the understanding of climate variations on the global scale. All observations are used to constrain short-range background forecasts in order to create an optimum analysis by combining the 4D- information from the forecast and observations over a long period of time taking into account their error characteristics. The background forecast is also used to identify and eliminate erroneous or conflicting observations and to give adjustments for the possible biases in them. The reanalysis view of climate variations in contrast to the traditional climate statistics is a simultaneous view of all variables from a single dynamically consistent source. In addition to the analyzed variables the model integration from analysis time to the next gives products from physical processes and therefore contributes to studies of hydrological cycle and general circulation. ERA-40 reanalysis products are a significant improvement on those from the first generation ERA-15 reanalysis. The improvements have been partly due to the development of the underlying operational forecasting system, to the identification of deficiencies in ERA-15 and also due to a more comprehensive usage of space based and conventional observations. ERA-40 now represents low frequency variability and trends of surface air temperature that is in good agreement with independent analysis of surface station data since late 1970s. At the same time the monthly mean middle to upper-tropospheric and lower stratospheric temperatures are in good agreement with the MSU record processed by Mears et al. and the QBO is in good agreement with independent rocketsonde data. However, the Brewer-Dobson circulation is too intense, the age of air in the stratosphere is too young and significant temperature biases are found in upper stratosphere. Precipitation over the tropical belt is also excessive during the satellite era from 1979 onwards. Improvements towards the next generation climate reanalysis will be made by improving the assimilating model, using a more refined assimilation method, and by improving, where possible, the data coverage and data usage. This will yield reanalyses that are further suited to establishing a more objective view of variations in climate.
DE: 3309 Climatology (1620)
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly