Search

Sea surface temperature (SST) variability has been shown to have predictive value for land precipitation, although SSTs are unable to fully predict intraseasonal to interannual hydrologic extremes. The possible remote effects of large‐scale land surface temperature (LST) and subsurface temperature (SUBT) anomalies in geographical areas upstream and closer to the areas of drought/flood have largely been ignored. Here evidence from climate observations and model simulations addresses these effects. Evaluation of observational data using Maximum Covariance Analysis identifies significant correlations between springtime 2‐m air temperature (T2 m) cold (warm) anomalies in both the western U.S. and the Tibetan Plateau and downstream drought (flood) events in late spring/summer. To support these observational findings, climate models are used in sensitivity studies, in which initial LST/SUBT anomaly is imposed to produce observed T2 m anomaly, to demonstrate a causal relationship for two important cases: between spring warm T2 m/LST/SUBT anomalies in western U.S. and the extraordinary 2015 flood in Southern Great Plains and adjacent regions and between spring cold T2 m/LST/SUBT anomalies in the Tibetan Plateau and the severe 2003 drought south of the Yangtze River region. The LST/SUBT downstream effects in North America are associated with a large‐scale atmospheric stationary wave extending eastward from the LST/SUBT anomaly region. The effects of SST in these cases are also tested and compared with the LST/SUBT effects. These results suggest that consideration of LST/SUBT anomalies has the potential to add value to intraseasonal prediction of dry and wet conditions, especially extreme drought/flood events. The results suggest the importance of developing land data and models capable of preserving observed soil memory. Possible remote effects of large‐scale land surface temperature in geographical areas upstream on droughts/floods have largely been ignoredObservations show significant lagged correlation between spring surface temperature and downstream drought‐flood in North America and East AsiaNorth America and East Asian modeling studies show causal relationship between spring land temperature anomaly and downstream summer drought/flood

Natural lakes and artificial reservoirs are important components of the Earth system and essential for freshwater, food, and energy. Relatively little is known about the variations of lake and reservoir surface area globally. For the first time, this study presents the global variation of lake and reservoir surface areas for all water bodies larger than 1 km2. Using radar remote sensing, we found that global aggregate area variations were only 2% of total surface area over a 3 year period. When considering the total surface area of shoreline regions that transition between land and water, these variations equaled 20% of total lake and reservoir surface area, largely driven by variations of smaller water bodies. Additionally, surface areas of reservoirs tends to be more variable than the surface area of lakes of similar size. The large surface area variations evidenced here, could have a previously underappreciated impact on the Earth System. Natural lakes and artificial reservoirs are important parts of the Earth system and provide many benefits for humanity. Despite this importance, there are key things about lakes and reservoirs that are unknown globally, including how and when surface areas vary. This study uses satellite‐based radar observations to estimate surface area variations in a set of the world's largest lakes and reservoirs. We found that the total surface area variability was relatively small when aggregated globally, only accounting for 2% of mean global surface water area. However, the total shoreline area that transitioned between water and land as a result of lake and reservoir variability was much more substantial, around 20% of mean global surface area. The variability of smaller water bodies contributed more to these transitional areas than larger water bodies. We also found that artificial reservoirs tended to be more variable than similarly sized natural lakes. Ultimately, the large surface area variations evidenced here, particularly in small water bodies, could have a previously underappreciated impact on the Earth System. Smaller water bodies show significantly more global sum total surface area variability than larger water bodiesReservoirs show more surface area variability than lakes of similar sizesGlobal intermittently inundated surface water body area is ∼20% of its average, and small water bodies made up the most significant portion Smaller water bodies show significantly more global sum total surface area variability than larger water bodies Reservoirs show more surface area variability than lakes of similar sizes Global intermittently inundated surface water body area is ∼20% of its average, and small water bodies made up the most significant portion