Evaluation of IPCC Soil Moisture Simulations for the latter half of the 20 th Century

Evaluation of IPCC Soil Moisture Simulations for the latter half of the 20th Century Haibin Li1, Alan Robock1, Martin Wild 2 1Department of Environmental Sciences, Rutgers University, New Brunswick, NJ, USA 2Institute for Atmospheric and Climate Science ETH, Swiss Federal Institute of Technology, Zurich, Switzerland

Outline • Why?? Model intended for projections should provide reliable reproduction of past/current climate • Data sets Observations & model outputs • Analysis Seasonal cycle, interannual variability, spatial pattern. Long term soil moisture evolution in warm season – trend analysis. Sensitivity experiment – radiation vs. soil moisture • Conclusions

Observations

Model outputs:

Seasonal cycle Top 10 cm (unit: cm) Better agreement over FSU regions. Less discrepancy in warm seasons. Total soil column (SWI)

Now single model performs superior than others at all regions. Better simulations in Ukraine, Russia and Illinois boxes. Poor results at Mongolia and China. CGCM3.1 (t47) has stronger interannual variations than obs at all regions. Two UK models have interannual variations comparable to obs. Taylor Diagram for top 10 cm soil moisture

Better simulation of precipitation not necessarily means more realistic soil moisture. Other factors also contribute. Taylor Diagram for precipitation

Generally, the drier the region is, the stronger interannual variation. Large inter-model differences and model-to-obs difference. Interannual variability (Coefficient of variance)

Seasonal trends b. precipitation a. Soil moisture c. temperature d. Radiation (SW)

Soil moisture evolution in summer (JJA), 1958-1999. Upward trend for both regions. Model ensembles show little change. The observed trend is far above that of model’s range. Evidence from pan evaporation (Peterson et al. 1995 ) and solar radiation at the earth surface (Wild et al. 2005).

Precipitation & temperature all increase slightly but are not statistically significant. Precipitation Observed trend for temperature is well constrained in models. Temperature What likely contributes to the observed trend in soil moisture?

Coincidence? Sensitivity experiments from ECHAM5 model (linear trend: units in mm/decade) Radiation: from dimming to brightening. Soil moisture: from upward trend to level-off.

Linear trend for top 10 cm (1981-1999, mm/decade)

Conclusions • Less discrepancy in warm season simulations. • Better simulations over Ukraine and Russia and Illinois boxes but not necessarily a result of good precipitation. • Large differences between obs and models in terms of interannual variability. Some model systematically exhibits stronger interannual variations. • Significant trends in warm season (JJAS) for soil moisture. Prep & temp don’t show much change. Model simulated trend for temperature is generally reliable. • Sensitivity analysis from ECHAM5 model did show model with indirect aerosol scheme may have a better change to capture observed soil moisture pattern.

Acknowledgements:

Evaluation of IPCC Soil Moisture Simulations for the latter half of the 20 th Century

Evaluation of IPCC Soil Moisture Simulations for the latter half of the 20 th Century

Presentation Transcript

The Dawn of the 20 th Century

The 20 th Century

Fashions Of The 20 th Century-1960

1 st Half of the 20 th Century Walkaway Review

Utah in the 1 st Half of the 20 th Century: 1900-1945

Utah in the 1 st Half of the 20 th Century: 1900-1945

Fashions of the 20 th Century 1930

Environmental Disasters of the 20 th Century

First Half of the 20 th Century 1901-1950

The changing Society of the 20 th Century

The Decades of the 20 th Century

Europe in the Latter 20 th Century: An Overview

At the beginning of the 20 th century

THE DAWN OF THE 20 TH CENTURY

The 20 th Century History of China

Art of the early 20 th century

Music of the 20 th Century

The 20 th Century

Influential Educators of the 20 th Century

Artists of the 20 th Century

The 20 th century

The Dawn of the 20 th Century