Deficient precipitation sensitivity to Sahel land surface forcings among CMIP5 models. (9th June 2022)

• Record Type: Journal Article
• Authors: Wang, Fuyao; Notaro, Michael; Yu, Yan; Mao, Jiafu
• Is Part Of: International journal of climatology. Volume 43:Number 1(2023)
• Page Start: 99
• Page End: 122
• Publication Date: 2022-06-09
• Subjects: CMIP5 -- DGVM -- land surface feedback -- precipitation -- Sahel; Climatology -- Periodicals; Climat -- Périodiques; Climatologie -- Périodiques; 551.605
• DOI: 10.1002/joc.7737
• Languages: English
• ISSNs: 0899-8418

Abstract

Abstract: The overall performance of the simulated seasonal precipitation response to local terrestrial forcings, namely vegetation abundance and soil moisture, in the Sahel among the Coupled Model Intercomparison Project Phase Five (CMIP5) Earth System Models (ESMs) is systematically investigated and compared with its observational counterpart using a multivariate statistical method. The observed seasonal precipitation response is evaluated against a large ensemble of observational, reanalysis, and satellite data sets to provide quantification of uncertainties. The behaviour of models with and without a Dynamic Global Vegetation Model (DGVM) component is also explored, along with the mechanisms responsible for terrestrial feedback on rainfall. In general, the CMIP5 models can reasonably capture the seasonal evolution of Sahel precipitation and soil moisture, albeit with wet biases during the pre‐monsoon period and dry biases during the peak monsoon period. The non‐DGVM ESMs simulate comparable leaf area indices (LAIs) with observations, while DGVM‐enabled ESMs simulate too much year‐round LAI. The variance of precipitation that is attributed to oceanic forcings in CMIP5 is comparable with observations; however, the variance of precipitation that is attributed to terrestrial forcings is smaller in CMIP5 models than observed, especially for non‐DGVM ESMs. CMIP5 models, especially those without DGVMs, undervalue precipitation's observed response strength to soil moisture anomalies. In both observations and CMIP5 models, none of the atmospheric variables show significant responses to direct vegetation forcing, except for the response in transpiration. Although vegetation has minimal direct effect on the atmospheric state, it can affect the atmosphere by modifying soil moisture and transpiration rate indirectly, which helps explain the more realistic simulation of rainfall in DGVM‐enabled ESMs than non‐DGVM ESMs. Coupling of an ESM to a DGVM is critical in generating reasonable land–atmosphere feedback and examining future ecological and climatic changes over the Sahel. Abstract : Percent explained variance of JJA precipitation anomalies across the Sahel attributed to oceanic (blue), vegetation (green), soil moisture (red/orange), and total (black/grey) forcings in observations, CMIP5 ESMs, DGVM‐enabled and non‐DGVM CMIP5 ESMs during 1960–2000. The shading indicates the 10th and 90th percentiles across either the multi‐observational data sets or multi‐CMIP5 models. The solid horizontal lines indicate the 50th percentile. The red boxes in DGVM and non‐DGVM columns indicate that the difference between DGVM‐enabled ESMs and non‐DGVM ESMs is statistically significant.