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The cold tongue mode (CTM), which represents the out-of-phase relationship in sea surface temperature anomaly (SSTA) variability between the Pacific cold tongue region and elsewhere in the tropical Pacific, shows a long-term cooling trend in the eastern equatorial Pacific. In this study, we investigate how well the CTM is reproduced in historical simulations generated by the 20 models considered in Phase 5 of the Coupled Model Intercomparison Project (CMIP5). Qualitatively, all 20 models roughly capture the cooling SSTA associated with the CTM. However, a quantitative assessment (i.e., Taylor diagrams and the ratio of the trend between the simulations and observations) shows that only five of these 20 models (i.e., CESM1-CAM5, CMCC-CM, FGOALS-g2, IPSL-CM5B-LR, and NorESM1-M) can reproduce with useful accuracy the spatial pattern and long-term trend of the CTM. We find that these five models generally simulate the main ocean dynamical process associated with the CTM. That is, these models adequately capture the long-term cooling trend in the vertical advection of the anomalous temperature by the mean upwelling. We conclude that the performance of these CMIP5 models, with respect to simulations of the long-term cooling trend associated with the vertical advection, and the related long-term decreasing trend of the vertical gradient of the oceanic temperature anomaly, can play an important role in successful reproduction of the CTM.

This study proposed a parameterization methodology based on Landsat-7 ETM data and field observations and tested it for deriving an evaporative fraction (EF) over a heterogeneous landscape. As a case study, the methodology was applied to the experimental area of CAMP/Tibet located on the central Tibetan Plateau. Four scenes of Landsat-7 ETM data were used in the study. Scenes of 9 June 2002 and 28 August 2002 were selected as case examples of summer and autumn, respectively; the scene of 2 December 2002 was selected as a winter case; and 24 March 2003 was selected as a spring case (or pre-monsoon period). To validate the proposed methodology, the Landsat-7 ETM derived EFs were compared to ground-measured values in four different months that spanned a wide range of surface conditions and surface features. This comparison revealed that the predictions were in good accordance with the ground measurements with absolute percent differences of less than 9.5%. It was concluded that the proposed methodology successfully facilitates the retrieval of EF using Landsat-7 ETM data and field observations over the study area.