Observed relationship between the Turkana low-level jet and boreal summer convection
Observed relationship between the Turkana low-level jet and boreal summer convection
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图尔卡纳低空急流与夏季北方对流之间的观测关系
DOI：
10.1007/s00382-019-04769-2
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发表时间：
2019
期刊：
影响因子：
4.6
通讯作者：
Cook, Kerry H.
中科院分区：
文献类型：
--
作者：
Vizy, Edward K.;Cook, Kerry H.
图尔卡纳低空急流是肯尼亚北部的一种环流特征，在许多观测数据集中，该特征在空间上并未得到很好的解析。在这里，对高分辨率 TRMM、IMERG 和 CMORPH 降水估计以及 ERA5 和 MERRA2 重新分析进行了分析，以更好地了解对急流强度的控制以及南苏丹急流出口区域急流与北方夏季降雨变化之间的关系。对 2000 年至 2017 年南苏丹雨季高峰（8 月）进行了分析。从气候角度来看，急流出口区域的降雨量在清晨达到峰值，与急流最大值一致。强急流增强了低空风辐合，并使低空纬向水汽梯度短暂向西移动。在南苏丹西部，由于白天供暖，降雨量在下午晚些时候/晚上达到高峰。每日图尔卡纳急流强度与降水之间的相关性表明，南苏丹东部、埃塞俄比亚和东非高地上空存在显着的负相关关系。对强急流和弱急流周期的综合分析表明，与强急流相关的大气条件包括赤道以南东非海岸的低空脊增强，导致图尔卡纳海峡的高度梯度更强，以及该海峡和邻近高地的干燥条件。这些条件支持更强的射流，由于高地夜间更强的冷却以及射流出口区域上空干燥空气平流的增强，下降流进一步增强了射流。因此，虽然低层辐合可能会增加，但由于大气湿度降低和不稳定性减弱，南苏丹东部的对流减弱。弱喷气机情况则相反。
The Turkana low-level jet is a circulation feature over northern Kenya that is not spatially well-resolved in many observational datasets. Here, high-resolution TRMM, IMERG, and CMORPH precipitation estimates, along with the ERA5 and MERRA2 reanalyses are analyzed to better understand the controls on jet strength and the relationship between the jet and boreal summer rainfall variability in the jet exit region over South Sudan. The height of the South Sudan wet season, August, is analyzed for 2000–2017. Climatologically, rainfall peaks over the jet exit region during the early morning hours, coinciding with the jet maximum. The strong jet enhances low-level wind convergence and briefly shifts the low-level zonal moisture gradient westward. Over the western South Sudan, rainfall peaks in the late afternoon/evening in association with daytime heating. The correlation between the daily Turkana Jet strength and precipitation indicates a significant negative relationship over eastern South Sudan, and over the Ethiopian and East African Highlands. Composite analysis of strong and weak jet periods reveal that the atmospheric conditions associated with a strong jet include enhanced low-level ridging along the East African coast south of the equator resulting in a stronger height gradient in the Turkana Channel, as well drier conditions over the channel and adjacent highlands. These conditions support a stronger jet that is further enhanced by katabatic flow due to the stronger nighttime cooling over the highlands, as well as enhanced dry air advection over the jet exit region. Thus, while low-level convergence may increase, convection weakens over eastern South Sudan due to the reduced atmospheric moisture content and weaker instability. The opposite occurs for the weak jet case.
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DOI：
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发表时间：
1978
期刊：
影响因子：
--
作者：
J. Hart;G. Rao;H. V. D. Boogaard;John A. T. Young;J. Findlater
通讯作者：
J. Findlater
肯尼亚北部（图尔卡纳海峡）新发现的喷气式飞机
DOI：
--
发表时间：
1982
期刊：
影响因子：
--
作者：
J. Kinuthia;G. Asnani
通讯作者：
G. Asnani
北部夏季印度洋附近的主要低层气流，西印度洋上空对流层低层的半球间空气输送。
DOI：
--
发表时间：
1970
期刊：
影响因子：
--
作者：
J. Findlater
通讯作者：
J. Findlater
大非洲之角的突然降雨转变：观测和区域模型模拟
影响因子：
--
作者：
E. Riddle;K. Cook
通讯作者：
K. Cook
维多利亚湖及东非北部裂谷其他湖泊的历史涨落
影响因子：
4.9
作者：
S. Nicholson
通讯作者：
S. Nicholson