Northern Hemisphere Extratropical Cyclones in a Warming Climate in the HiGEM High-Resolution Climate Model
Northern Hemisphere Extratropical Cyclones in a Warming Climate in the HiGEM High-Resolution Climate Model
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DOI：
10.1175/2011jcli4181.1
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发表时间：
2011-10-15
影响因子：
4.9
通讯作者：
Hodges, Kevin I.
中科院分区：
文献类型：
--
作者：
Catto, Jennifer L.;Shaffrey, Len C.;Hodges, Kevin I.
本文研究了气候变暖时北方半球冬季（12月至2月）热带外风暴路径和气旋的变化。两个理想化的气候变化实验与高分辨率全球环境模式版本1.1（HiGEM1.1），一个加倍的CO2和一个四倍的CO2实验，进行了比较，对目前的控制运行。采用客观的特征跟踪方法，重点关注区域变化。控制运行的热带风暴路径的气候学与欧洲中期天气预报再分析中心（ERA-40）的40年期预报结果吻合较好，而气旋强度的频率分布也比较好。在两次模拟中，平均气候变化与政府间气候变化专门委员会第四次评估报告（AR 4）模式的模拟结果基本一致。冬季极地表面变暖强烈增强，北大西洋对流层下部变暖减少，与经向翻转环流的减缓有关。在不同的CO2强迫下，两种理想化模式的北大西洋环流变化是不同的。在北大西洋，风暴路径受MOC减慢、地面极地变暖增强和热带对流层上部变暖增强的影响，在2 × CO2试验中风暴路径向东北移动，但在4 × CO2试验中没有移动。在太平洋，在2 × CO2试验中，平均气候变化与当地温度变化有关。而在4 × CO2实验中，太平洋的变化受到减弱的热带环流的影响。风暴路径的变化与纬向风的变化相一致，随着CO2强迫的增加，北方半球的气旋总数减少。气旋强度的变化是用850百帕涡度、平均海平面气压和850百帕风来发现的。发现北方半球气旋的强度相对于对照减弱。
Changes to the Northern Hemisphere winter (December February) extratropical storm tracks and cyclones in a warming climate are investigated. Two idealized climate change experiments with the High Resolution Global Environmental Model version 1.1 (HiGEM1.1), a doubled CO2 and a quadrupled CO2 experiment, are compared against a present-day control run. An objective feature tracking method is used and a focus is given to regional changes. The climatology of extratropical storm tracks from the control run is shown to be in good agreement with the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40), while the frequency distribution of cyclone intensity also compares well.In both simulations the mean climate changes are generally consistent with the simulations of the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) models, with strongly enhanced surface warming at the winter pole and reduced lower-tropospheric warming over the North Atlantic Ocean associated with the slowdown of the meridional overturning circulation. The circulation changes in the North Atlantic are different between the two idealized simulations with different CO2 forcings. In the North Atlantic the storm tracks are influenced by the slowdown of the MOC, the enhanced surface polar warming, and the enhanced upper tropical-troposphere warming, giving a northeastward shift of the storm tracks in the 2 x CO2 experiment but no shift in the 4 x CO2 experiment.Over the Pacific, in the 2 X CO2 experiment, changes in the mean climate are associated with local temperature changes, while in the 4 X CO2 experiment the changes in the Pacific are impacted by the weakened tropical circulation. The storm-track changes are consistent with the shifts in the zonal wind.Total cyclone numbers are found to decrease over the Northern Hemisphere with increasing CO2 forcing. Changes in cyclone intensity are found using 850-hPa vorticity, mean sea level pressure, and 850-hPa winds. The intensity of the Northern Hemisphere cyclones is found to decrease relative to the control.