本周四，中国数个产粮大省干旱多时的冬天终于迎来零星降雪，从政策制定者到各地打雪仗的孩子们对此都兴奋不已。
今冬的旱情已引发了包括联合国(UN)在内的一些方面对小麦收成的担心。中国总理温家宝周三主持召开国务院会议，讨论粮食政策，随后宣布发放逾10亿美元的抗旱浇麦补贴和抗旱机具购置补贴。
但中国同时也在部署一种抗旱"银弹"：会增加自然降雪的大规模云种散播。
官方媒体报道称，周三晚间和周四清晨，中国空军在14.99万平方公里的空域播撒氧化银，以期在冷风来袭期间推动云团的形成。
由此产生的阵雪并不大，仅有几毫米降雪。
但自从在北京奥运会期间用类似方法驱散云团之后，中国气象部门似乎越来越喜爱这种技术。中国有3.7万余名"人工影响天气工作者"参与人工影响天气计划，气象部门还设定了全年增雨目标。
云种散播的原理是推动湿空气转变为降雨，具体方法常常是向湿空气播撒碘化银晶体，以加速雨滴（或雪花，就像此次情况这样）的形成。官方媒体称，本周中国的云种散播工程动用了2197枚火箭和6448枚炮弹。
科学家们表示，人工增雨是否真的会增加降雨仍没有定论。但各方似乎仍愿意投入大量资源，对易干旱地区实施人工增雨，即使结果很有争议。
对于忙着庆祝今冬（连续108天无降水后）第一场雪的北京民众而言，论据似乎无可辩驳。对于中国领导人而言，此次降雪的时机也极其可心――温家宝讲话后立即来临。但从长期来看，中国将持续缺水。要解决这个问题，仅仅靠散播一些碘化银晶体可能是不够的。
译者/何黎
http://www.ftchinese.com/story/001036892
China's long, dry winter was broken by scatted snowfall across several breadbasket provinces on Thursday―much to the joy of policymakers, as well as snowball-throwing children every where.
The drought this winter has raised concerns about the wheat crop in some quarters including the UN. China's top policy body, the State Council, was summoned to discuss crop policies by Premier Wen Jiabao on Wednesday, and subsequently more than $1bn in crop subsidies and drought relief was announced.
But China is also deploying a proverbial "silver bullet" to fight the drought: large-scale cloud seeding that will augment natural snowfall.
According to official media, China's air force showered silver oxide over 149,900 sq km on Wednesday evening and Thursday morning, boosting the formation of clouds during a cold front.
The resulting shower was light―just a couple of millimetres of snow.
But the technique is one that China's air force seems increasingly fond of, after using similar methods to keep clouds at bay during the Beijing Olympics. China employs more than 37,000 rainmakers, people involved with weather modification programs, and the meteorological bureau sets annual goals for how much rainfall should increase.
Cloud seeding works by encouraging moist air to turn into rain, often by sowing silver iodide crystals into moist air to speed up the creation of raindrops (or snowflakes, in this case). China's cloud-seeding projects this week involved more 2,197 rockets and 6,448 artillery shells, according to state media.
Scientists say the jury is still out on whether cloud seeding really does create additional rainfall. But, it seems, people are still willing to devote a lot of resources to rainmaking in drought-prone areas, even when results are debatable.
For the Beijingers busy celebrating the first snowfall of the season (after 108 days with no moisture), the evidence seems undeniable. And for China's leaders the timing of the snowfall is extremely convenient, arriving as it does just after Mr Wen's remarks. But China is chronically short of water in the long term―a problem that may take more than a few silver iodide crystals to solve.
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