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These high rates of precipitation result in high rates of river discharge to the coastal ocean. These global averages mask great variability. For example, there are tropical coastal areas of high aridity, such as the Red Sea and Arabian Sea as well as the NW coast of Australia. In these areas, rates of evaporation exceed precipitation and temperatures often exceed the global average, having devastating effects on coral growth and reproduction and lower biodiversity, as fewer species can tolerate these conditions.

      In the tropical Atlantic, atmospheric circulation anomalies interact with ocean circulation to produce anomalous SST and precipitation patterns (Figures 1.1 and 2.6). These anomalies originate off the African coast and expand westwards. Indeed, precipitation is low in these regions, and SSTs are correspondingly high year‐round. A large area of the tropical southeast Atlantic is low in rainfall, south of the equator to about 30 °S, like the eastern boundary of South America. The El Niño‐Southern Oscillation (ENSO) phenomenon is the primary source of short‐term climate variability and is associated with distinct and different atmospheric and oceanic climate anomalies that affect rainfall, river flow, temperature, tropical cyclone activity, and shifts in the position of the major convergence zones (see Section 2.6).

Schematic illustration of seasonal mean global precipitation (mm d-1) from the Global Precipitation Climatology Project (GPCP) (a) December–January–February (DJF), (b) March–April–May (MAM), (c) June–July–August (JJA) and (d) September–October–November (SON), 1979–2014.

      Source: Image in the public domain courtesy of the NASA Scientific Visualization Studio. https://sus.gsfc.nasa.gov/4760 (accessed 10 June 2021). © NASA.

      Monsoons are a central component of global climate and are critical to the global transport of atmospheric energy and water vapour. More than 70% of the world's population lives in monsoonal regions and these systems have a profound effect on society and the global economy. Zhisheng et al. (2015) proposed the following definition of the global monsoon:

       The global monsoon is the significant seasonal variation of three‐dimensional planetary‐scale atmospheric circulations forced by seasonal pressure system shifts driven jointly by the annual cycle of solar radiative forcing and land‐sea interactions, and the associated surface climate is characterised by a seasonal reversal of prevailing wind direction and a seasonal alternation of dry and wet conditions.

Schematic illustration of global distribution of monsoon domains and dry regions.

      Source: Zhou et al. (2016), figure 1, p. 3590. Licensed under CC BY 4.0. © Copernicus Publications.

      2.4.1 The Asian Monsoon

Schematic illustration of global tracks and intensity of all tropical storms, 1856–2006.

      Source: Image retrieved via public access from NASA Earth Observatory. http://earthobservatory.nasa.gov/IOTD/view.php?id=7079. (accessed 25 June 2019). © NASA.

      The

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