Beryllium-10 and beryllium-7 in precipitation in Dubendorf (440 m) and at Jungfraujoch (3580 m), Switzerland (1998-2005)
Beryllium-10 and beryllium-7 in precipitation in Dubendorf (440 m) and at Jungfraujoch (3580 m), Switzerland (1998-2005)
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DOI：
10.1029/2007jd009160
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发表时间：
2008-06
影响因子：
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通讯作者：
U. Heikkilä;J. Beer;V. Alfimov
中科院分区：
文献类型：
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作者：
U. Heikkilä;J. Beer;V. Alfimov
[1]从1998年至今，在瑞士的一个高海拔（少女峰，46.32°N 7.59°E，3580 m）和一个低海拔（杜本多夫，47.25°N 8.27°E，440 m）站的月降水样本中测量了铍-10和铍-7。7 Be的平均沉积通量在杜本多夫为380 ± 30 atoms m−2 s−1，在少女峰约赫为320 ± 20 atoms m−2 s−1; 10 Be的平均沉积通量在杜本多夫为810 ± 70 atoms m−2 s−1，在少女峰约赫为810 ± 60 atoms m−2 s−1。在少女峰测得的10 Be/7 Be比值（2.4 ± 0.1）高于杜本多夫（2.1 ± 0.1），这可能是由于少女峰平流层空气中的7 Be含量因放射性衰变而减少。该比率对应于110-120天的平均大气停留时间。沉积通量表现出夏季最大、冬季最小的季节变化。10 Be/7 Be比值在少女峰上半年根据季节性平流层-对流层交换（STE）变化呈现最大值。在杜本多夫，最大值出现在1个月后。一个两箱模型的分析表明，由于季节性变化的STE计算的变异性解释只有三分之一的10 Be/7 Be比率的观测变异性。其余的变异性是由局部影响引起的，例如降水率和中纬度地区高于平均水平的STE变异性。根据模型计算，全球平均10 Be/7 Be比值仅在1.1和1.5之间变化，具有季节性变化的STE。中纬度地区较大的测量值表明10 Be/7 Be比值具有纬度依赖性。
[1] Beryllium-10 and beryllium-7 have been measured in monthly precipitation samples at a high (Jungfraujoch, 46.32°N 7.59°E, 3580 m) and a low (Dubendorf, 47.25°N 8.27°E, 440 m) altitude station in Switzerland from 1998 till today. The average deposition fluxes of 7Be are 380 ± 30 atoms m−2 s−1 in Dubendorf and 320 ± 20 atoms m−2 s−1 at Jungfraujoch, and the fluxes of 10Be are 810 ± 70 atoms m−2 s−1 in Dubendorf and 810 ± 60 atoms m−2 s−1 at Jungfraujoch. The 10Be/7Be ratio measured at Jungfraujoch (2.4 ± 0.1) is higher than in Dubendorf (2.1 ± 0.1), which is probably caused by a greater share of stratospheric air at Jungfraujoch in which the 7Be content is reduced because of radioactive decay. The ratios correspond to a mean atmospheric residence time of ∼110–120 d. The deposition fluxes show a seasonal change with a summer maximum and a winter minimum. The 10Be/7Be ratio exhibits a maximum in the first half of the year at Jungfraujoch in accordance with seasonal stratosphere-troposphere exchange (STE) variations. In Dubendorf the maximum occurs 1 month later. An analysis with a two-box model shows that the calculated variability due to seasonally varying STE explains only one third of the observed variability in the 10Be/7Be ratio. The rest of the variability is caused by local effects, such as the precipitation rate and the larger than average STE variability at the midlatitudes. According to the model calculations, the global mean 10Be/7Be ratio only varies between 1.1 and 1.5 with a seasonally varying STE. The larger measured values in the midlatitudes point to a latitudinal dependence of the 10Be/7Be ratio.