Climate drift in preindustrial control (PICTL) simulations can lead to spurious climate trends and large uncertainties in historical and future climate simulations in coupled models. This study examined the long-term behaviors and stabilities of the PICTL simulations in the two versions of FGOALS2 (the Flexible Global Ocean-Atmosphere-Land System model Version 2), which have been submitted to the Coupled Model Inter-comparison Project Phase 5 (CMIP5). As verified by examining time series of thermal fields and their linear trends, the PICTL simulations showed stable long-term integration behaviors and no obvious climate drift [the magnitudes of linear trends of SST were both less than 0.04oC (100 yr)-1] over multiple centuries. The changed SSTs in a century (that corresponded to the linear trends) were less than the standard deviations of annual mean values, which implied the internal variability was not affected. These trend values were less than 10% of those of global averaged SST from observations and historical runs during the periods of slow and rapid warming. Such stable long-term integration behaviors reduced the uncertainty of the estimation of global warming rates in the historical and future climate projections in the two versions of FGOALS2. Compared with the trends in the Northern Hemisphere, larger trends existed in the SST and sea ice extents at the middle to high latitudes of the Southern Hemisphere (SH). To estimate the historical and future climate trends in the SH or at some specific regions in FGOALS2, corrections needed to be carried out. The similar long-term behaviors in the two versions of FGOALS2 may be attributed to proper physical processes in the ocean model. 相似文献
Accurate understanding of snow cover phenology and its changes is important to hydrological processes and climate system. Having recognized the potential uncertainties in remote sensing snow cover products, we used daily snow depth observations from 514 meteorological stations across China to investigate the spatiotemporal variations in snow cover phenology during 1970–2014. Climatologically, the snow cover onset date (Do) and end date (De) as well as the number of snow cover days (Ds) depended on latitude at most stations outside of the Tibetan Plateau (TP). For the high-elevation stations, which were mainly in the TP, multiple snow-free breaks (SFBs) during the cold season made Ds insensitive to Do and De. Furthermore, the number of SFBs (Db) increased significantly with the rise in elevation, explaining why higher altitudes in TP did not necessarily have greater Ds values despite the earlier Do and later De values. From 1970 to 2014, most stations in China exhibited delayed Do and advanced De due mainly to the increased temperature, but such trends were significant at only 10.5% and 15.4% of the stations, respectively. During the same period, shortened Ds primarily occurred south of ~ 40° N, whereas the opposite ones dominated north of ~ 40° N. Most stations (except those in Hexi Corridor) with significant growth in Ds were characterized by delayed Do and advanced De. Such a phenomenon of “increased snow cover days during shortened cold season” was due to the significant shrinkage in Db values. The spatial pattern of the trends in annual total snow depth overall follows that of Ds, suggesting that the Ds, when takes SFBs into consideration, could be an indicator of variations of snow water resources in China. The trends in Do, De and Ds were not elevation dependent in TP.
The damage to the masonry-infilled reinforced concrete (RC) frame buildings in Charikot, the capital city of Dolakha district in Nepal, during the 2015 April-to-May Nepal earthquake sequence is reported. Most of these buildings were built by the owners with little governmental inspections regarding their structural design or constructional quality. Although they generally performed better than other structural systems such as stone-masonry houses, the RC frames sustained extensive damage ranging from cracking of infill to complete collapse. In particular, eight of the 72 inspected RC frames alongside an uphill street collapsed in different ways. In addition to the un-engineered nature of these RC frames, their collapse could also be attributed to multiple technical reasons including the effect of terrain, the pounding between adjacent buildings and the accumulative damage in the earthquake sequence. 相似文献