Atmospheric moisture budget over Antarctica and the Southern Ocean based on the ERA‐40 reanalysis
Atmospheric moisture budget over Antarctica and the Southern Ocean based on the ERA‐40 reanalysis
复制标题
基于 ERA-40 再分析的南极洲和南大洋的大气湿度收支
DOI：
--
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
T. Vihma
中科院分区：
文献类型：
--
作者：
Hanna Tietäväinen;T. Vihma
根据欧洲中期天气预报中心的ERA - 40再分析，分析了1979-2001年期间南极洲和南大洋的大气湿度收支。瞬态涡旋经向输送对水汽南下输送贡献最大。平均经向环流有助于南极沿海地区向北输送，但这种作用被静止涡旋向南输送所补偿。经向水汽输送辐合在64-68°S最大，而纬向输送辐合在气旋高解区具有区域性重要性。水汽输送的年际变化与南方环状模态（SAM）有关。东向输运与SAM指数呈显著正相关（95%置信水平），而北向输运与SAM指数在60°S附近呈显著负相关。ERA - 40再分析很好地实现了水文平衡：水汽通量辐合（基于分析）和净降水（基于24小时预报的降水减去蒸发）之间的差异在南大洋上仅为13毫米/年（3%），在大陆冰盖上为- 8毫米/年（5%）。在公海上，分析方法有利于通量收敛的准确性。在整个研究区，年平均通量辐合超过净降水11 mm yr - 1（3%）。1979-2001年南极大陆冰盖平均降水的ERA - 40结果为177±8 mm yr - 1，而以前的估计范围为173 ~ 215 mm yr - 1。1979-2001年期间，ERA - 40数据未显示南极接地冰原和冰架上的降水有任何统计上显著的趋势。从ERA - 40数据来看，整个大陆的年平均净蒸发量（蒸发量减去凝结量）为正。版权所有©2008英国皇家气象学会
The atmospheric moisture budget over Antarctica and the Southern Ocean was analysed for the period 1979–2001 on the basis of the ERA‐40 reanalysis of the European Centre for Medium‐Range Weather Forecasts. Meridional transport by transient eddies makes the largest contribution to the southward water vapour transport. The mean meridional circulation contributes to the northward transport in the Antarctic coastal areas, but this effect is compensated by the southward transport by stationary eddies. The convergence of meridional water vapour transport is at its largest at 64–68°S, while the convergence of zonal transport is regionally important in areas of high cyclolysis. Inter‐annual variations in water vapour transport are related to the southern annular mode (SAM). The eastward transport has a significant (95% confidence level) positive correlation with the SAM index, while the northward transport has a significant negative correlation with SAM near 60°S. Hydrological balance is well‐achieved in the ERA‐40 reanalysis: the difference between the water vapour flux convergence (based on analysis) and the net precipitation (precipitation minus evaporation, based on 24‐h forecasts) is only 13 mm yr−1 (3%) over the Southern Ocean and − 8 mm yr−1 (5%) over the continental ice sheet. Over the open ocean, the analysis methodology favours the accuracy of the flux convergence. For the whole study region, the annual mean flux convergence exceeded net precipitation by 11 mm yr−1 (3%). The ERA‐40 result for the mean precipitation over the Antarctic continental ice sheet in 1979–2001 is 177 ± 8 mm yr−1, while previous estimates range from 173 to 215 mm yr−1. For the period 1979–2001, the ERA‐40 data do not show any statistically significant trend in precipitation over the Antarctic grounded ice sheet and ice shelves. From the ERA‐40 data, the annual average net evaporation (evaporation minus condensation) is positive over the whole continent. Copyright © 2008 Royal Meteorological Society