Evaluation of reanalysis soil moisture simulations using updated Chinese soil moisture observations.

TitleEvaluation of reanalysis soil moisture simulations using updated Chinese soil moisture observations.
Publication TypeReport
Date Published11/2004
Series/CollectionERA-40 Project Report Series
Document Number20
AuthorsLi, H-Y, Robock, A, Liu, S, Mo, X, Viterbo, P
Event Series/CollectionERA Report
Place of publicationShinfield Park, Reading

Using 19 years of Chinese soil moisture data from 1981-1999, we evaluate soil moisture in three reanalysis outputs: ERA40, NCEP/NCAR reanalysis (R-1), and NCEP/DOE reanalysis 2 (R-2) over China. R-2 shows improved interannual variability and better seasonal patterns of soil moisture than R-1 as the result of incorporation of observed precipitation, but not for all stations. ERA40 produces a better mean value of soil moisture for most Chinese stations and good interannual variability. Limited observations in the spring indicate a spring soil moisture peak for most of the stations. ERA40 generally reproduced this event, while R-1 or R-2 generally did not capture this feature, either because the soil was already saturated or the deep soil layer is too thick and damps such a response. ERA40 and R-1 have a temporal time scale comparable to observations, but R-2 has a memory of nearly 5 months for the growing season, about twice the temporal scale of the observations. The cold season tends to prolong soil moisture memory by about 3 months for R-2 and 1 month for ERA40. The unrealistic long temporal scale of R-2 can be attributed to the deep layer of the land surface model, which is too thick and dominates the soil moisture variability. R-1 has the same land surface scheme as R-2, but shows a temporal scale close to observations, which actually is because of soil moisture nudging to a fixed climatology. This new long time series of observed soil moisture will prove valuable for other studies of climate change, remote sensing, and model evaluation.

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