A month of severe weather wreaks havoc across China

  • The severe weather has led to travel disruption. Image: Anna Gowthorpe/PA Archive/Press Association Images

    More heavy rain is forecast for the first week of April. Image: MeteoGroup UK

    A change in wind direction is set to give a much drier weekend. Image: MeteoGroup UK

  • A month of severe weather wreaks havoc across China
    30.03.2013 15:46

    March 2013 may be remembered as a month of exceptionally cold weather in the UK, however it will be remembered for completely different reasons in China where no fewer than five separate bouts of severe weather have occurred. These have included torrential storms with rain, sleet, hail and thunder as well as several tornadoes, leading to high economic costs and dozens of lives lost.

    Large parts of central and southern China have had an active month, weather-wise, with widespread and powerful storm activity. The storms are estimated to have damaged 106,749 acres of cropland with as much as 16,803 acres of crops completely destroyed.
    A particularly powerful tornado hit Dongguan in Guangdong province on 20th March with maximum wind speeds of up to 176.8 km/h. This event alone led to 9 fatalities, 272 people severely injured and the equivalent of $209 million in damage to the economy.

    While convective thunderstorms are by no means unheard of in central and southern China, they are far more commonplace during the rainy season. This takes places between the months of May and September when air pressure is low and surface heating is at its highest, giving rise to intense convection and subsequent heavy rain. For instance, average precipitation in Shanghai and Hong Kong during the month of June is 180mm and 394mm respectively, compared to just 84mm and 74mm in March. To put this into perspective, Yangjiang in Guangdong province recorded a phenomenal 105mm of precipitation in just 48 hours between 28th and 30th March.

    One possible explanation for the unseasonal weather is that southern China has been predominantly influenced by southerly winds in recent weeks. When this warm and humid air from the tropics collides with the much colder, drier air from continental Asia, this instability gives the perfect conditions for the birth of powerful storms and tornadoes.

    Rapid urbanisation across China is thought to be one of the main factors contributing to the severe flooding and travel disruption. Despite the fact that the torrential storms are likely to cause some localised flooding regardless of terrain, the increase in impermeable surfaces that goes hand in hand with the construction of new settlements is undoubtedly going to reduce the speed and ability of the ground to absorb the water. There are potentially more than a billion of people at risk with as much as 66% of the population situated in regions at significant threat from flooding.

    Another problem in dealing with floodwater is that the number of rivers in China have halved in 60 years, limiting the natural method of flood dispersal. Also, many of China’s remaining waterways have been blocked by the authorities for the ever-increasing demand on industry and water supply for the booming population.

    The Chinese authorities have an emergency response system in place which acts upon the forecasts provided by the National Climate Center to give warning to those who may be affected by imminent storm activity. However, the sporadic and fast-forming nature of convective storms means that they can only be predicted with any accuracy around 20 to 30 minutes before they break out. This doesn’t leave sufficient time for the message to reach those most at risk.

    The weather across southern China is expected to remain unsettled into the first week of April with further heavy and thundery showers, sparking the further risk of localised flooding. However, it is likely to turn drier towards the weekend as air pressure builds and winds change to a cooler and drier northerly direction, bringing a light at the end of the tunnel.

    By: John Lee