Gong, W. P., Schuttelaars, H. & Zhang, H. Tidal asymmetry in a funnel-shaped estuary with mixed semidiurnal tides. Ocean. Dynam 66, 637–658, https://doi.org/10.1007/s10236-016-0943-1 (2016). The Yangtze River, with a drainage area of 1.8 × 10 6 km 2, is the largest river in southern Asia 4. The YRE is located on the eastern China coast. As the major channel connecting the Yangtze River and East China Sea, the YRE is influenced by moderate tides and strongly varying river discharges 66. The YRE has a semidiurnal tidal regime ( \(({a}_{{K}_{1}}+{a}_{{O}_{1}})/({a}_{{M}_{2}}+{a}_{{S}_{2}}) < 0.25\), in which a represents tidal amplitude), where M 2 is the dominant tide and followed by S 2, K 1 and O 1. Under the intermediate river flow and tidal conditions, Jiangyin is the landward limits of tidal current reversal (240 km away from the mouth), while the tidal wave propagates upstream until Datong (645 km away from the mouth). The 20th Century Reanalysis (V2) Project http://www.esrl.noaa.gov/psd/data/gridded/data.20thC_ReanV2.html (2015)

A nonstationary harmonic analysis method is applied to examine the spatiotemporal evolution of tidal duration asymmetry under strongly variable river discharge conditions in the YRE, divided between the pre-TGD (1965–1985) and post-TGD (2003–2014) periods. The results quantify the contributions of dual and triad tidal combinations to the overall tidal duration asymmetries, based on tidal skewness. The hydrologic and morphologic effects are assessed based on the response of tidal duration asymmetry to varying river discharge and morphological changes, with the following main findings: Friedrichs, C. T. & Aubrey, D. G. Non-linear tidal distortion in shallow well-mixed estuaries: a synthesis. Estuarine, Coast. Shelf Sci. 27, 521–545, https://doi.org/10.1016/0272-7714(88)90082-0 (1988).

Yearbook of astronomy 2021

Hydrological data United Kingdom 1985 Yearbook: an account of rainfall, river flows and groundwater levels January to December 1985 Marcos, M., Puyol, B., Wöppelmann, G., Herrero, C. & Garcia-Fernandez, M. J. The long sea level record at Cadiz (southern Spain) from 1880 to 2009. Journal of Geophysical Research 116, C12003 (2011). Immersive and compelling. I read it in a single day! Everyone should take a plunge into this book.’ CATHY RENTZENBRINK China’s Yangtze River Estuary (YRE) is a natural system whose hydrodynamics exhibit strong spatiotemporal variations, making it an excellent location to investigate estuarine tidal dynamics. Although the characteristics of tidal propagation in the YRE have been widely studied 37, 38, the effects of river discharge have long been neglected and remain a challenge to understand nonstationary tidal dynamics. Recently, increasing attention has been paid to the responses of tidal dynamics to varying river discharge in the YRE 23, 39, 40, 41, 42, 43, 44, but few of those have described the long-term evolutions of tidal properties. In particular, it is of interest to establish the contrast before and after the operation of the Three Gorges Dam (TGD), which is the world’s largest river damming project. Its impacts have raised public concern following rapid economic development and increasing awareness of possible negative impacts for natural resources and the environment 45, 46, 47. Each volume has an introductory section which briefly describes methods of prediction,the effect of meteorological conditions on tides, and comments on any special tidal problems of the areas covered by the volume.

Seneviratne, S. I. et al. in A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change (IPCC) (eds Field C. B. et al.) 109–230 (Cambridge University Press, 2012). Whilst some have been critical, suggesting that the Yearbook had run its course and should have been laid to rest, the series continues and this is the fifth edition under the editorship of Mr Jones. Dangendorf, S. et al. Persistent acceleration in global sea-level rise since the 1960s. Nat. Clim. Chang. 9, 705–710, https://doi.org/10.1038/s41558-019-0531-8 (2019). We investigated two types of events: (1) extreme sea level events; and (2) extreme skew surges. Extreme sea level events directly lead to the exceedance of critical thresholds and hence are the primary dataset that should be analysed when assessing flooding. However, analyses of skew surge events are also useful, as they provide information on ‘near misses’. As we have shown, some of the skew surge events coincided with the extreme sea level events, when the storm surge occurred around the time of high water of a spring tide; most did not coincide, because the surge occurred near low tide or on a neap tide. Had several of the larger skew surge events occurred on a high spring tide, they would have resulted in higher extreme sea levels than have been observed in the last 100 years. In addition, skew surge time-series are more appropriate proxies for the inter-annual, multi-decadal and longer-term changes in ‘storminess’ and the links to regional climate, compared to extreme sea level time-series that are also influenced by astronomical tides.UK Tide Gauge Network, British Oceanographic Data Centre https://www.bodc.ac.uk/data/online_delivery/ntslf/ (2015) Dronkers, J. Tidal asymmetry and estuarine morphology. Neth. J. Sea Res. 20, 117–131, https://doi.org/10.1016/0077-7579(86)90036-0 (1986). Following the transfer of the Groundwater Archive to the Institute of Geological Sciences (now the British Geological Survey), the second edition of Groundwater: United Kingdom, covering the period 1974-80, was prepared by the Institute of Hydrology at the request of the Water Directorate of the Department of the Environment. Subsequently, groundwater level data were included in the Hydrological data UK publications. Wang, Z., Jeuken, C. & De Vriend, H. Tidal asymmetry and residual sediment transport in estuaries. Delft Hydraulics report Z2749 (1999).

Interestingly, only 15 of the 111 (14%) extreme skew surge events led to extreme sea levels ( Fig. 2d), while the vast majority (86%) did not. Hence, most extreme sea levels arose from moderate (i.e., <1 in 5 year return levels) skew surge events combined with astronomical spring high tides. Spatial analysisIn the fourth step, we extracted twice daily HW and LW value from the digital high frequency sea level dataset at Southend available from 1929 to 1983 and 1987 to the end of 1995. The extracted high and low water values from this digital dataset where then combined with the historic dataset captured from the ledgers at Southend. Pinto, J. G., Bellenbaum, N., Karremann, M. K., & Della-Marta, P. M. Serial clustering of extratropical cyclones over the North Atlantic and Europe under recent and future climate conditions. Journal of Geophysical Research: Atmospheres 118, 12476–12485 (2013).

The ‘Article Section’ of the book offers the reader longer articles by authors, both well-known and less-known, including prominent BAA members and Section Officers. As with the shorter essays these cover a range of topics, including: a summary of astronomy in the past year; the prospect of a human mission to Mars; archaeoastronomy; a technical essay on observing the Sun; an historical essay on Henrietta Swan Leavitt; and a fascinating article on some women in astronomy by Mary McIntyre, a topic which today is rightly being researched in greater depth. As with the shorter articles, these are very well written and presented.Haigh, I. D., Eliot, M. & Pattiaratchi, C. Global influences of the 18.61 year nodal cycle and 8.85 year cycle of lunar perigee on high tidal levels. Journal of Geophysical Research: Oceans (1978–2012) 116, C06025 (2011). Wadey, M. et al. A comparison of the 31 January–1 February 1953 and 5–6 December 2013 coastal flood events around the UK. Front. Mar. Sci. 2, 84 (2015). Cai, H., Savenije, H. H. G. & Toffolon, M. Linking the river to the estuary: influence of river discharge on tidal damping. Hydrol. Earth Syst. Sc. 18, 287–304, https://doi.org/10.5194/hess-18-287-2014 (2014).