The Diurnal Cycle of East Pacific Convection, Moisture, and CYGNSS Wind Speed and Fluxes
The Diurnal Cycle of East Pacific Convection, Moisture, and CYGNSS Wind Speed and Fluxes
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DOI：
10.1029/2022jd038133
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发表时间：
2023-04
期刊：
影响因子：
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通讯作者：
Emily M. Riley Dellaripa;E. Maloney;C. DeMott
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文献类型：
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作者：
Emily M. Riley Dellaripa;E. Maloney;C. DeMott
热带太平洋的远东地区是地球上降雨量最多的地区之一。这一地区的特点是一个强大的昼夜循环与降水开始在哥伦比亚的安第斯山脉在下午晚些时候和离岸移动过夜，同时组织成中尺度对流系统（MCS）。当MCS向西移动时，它们可以产生热带东风波，发展成热带气旋。新的测量近地面风速和潜热通量（LHFLX）从气旋全球导航卫星系统（CYGNSS）使命和ERA5再分析被用来评估变化的区域流模式，水分和LHFLX，有利于一个强大的向西传播的降水日周期在该地区。在CYGNSS时代（2018年5月至10月至2021年）的延长的北方夏季期间，比较了强与弱向西传播的日降水量。强传播的日子有一个更潮湿的对流层低层，更强的垂直积分水汽通量辐合比弱传播的降水天。增强的低层湿度得到了来自更强区域气流的风力驱动LHFLX的支持，包括乔科和加勒比低层急流以及巴拿马和帕帕加约间隙风。近海辐合和涡度的增加也有助于维持强降水传播期间的对流。背景变化的物理环境，而不是日变化，似乎更重要的是支持一个强大的降水日周期在该地区。
The far eastern tropical Pacific is one of the rainiest locations on Earth. This region is characterized by a robust diurnal cycle with precipitation initiating over the Andes mountains in Colombia in the late afternoon and moving offshore overnight while organizing into mesoscale convective systems (MCSs). As the MCSs move westward, they can seed tropical easterly waves that develop into tropical cyclones. Novel measurements of near‐surface wind speeds and latent heat flux (LHFLX) from the Cyclone Global Navigation Satellite System (CYGNSS) mission and ERA5 reanalysis are used to evaluate changes to regional flow patterns, moisture, and LHFLX that favor a strong westward propagating diurnal cycle of precipitation in this region. Days with strongly versus weakly westward propagating diurnal precipitation are compared during the extended boreal summer of the CYGNSS era (May–October 2018–2021). Strongly propagating days have a more moist lower troposphere with stronger vertically integrated moisture flux convergence than days with weakly propagating precipitation. The enhanced low‐level moisture is supported by increased wind‐driven LHFLX from stronger regional flows including the Choco and Caribbean Low‐Level Jets and Panama and Papagayo gap winds. Increased offshore convergence and vorticity also help sustain convection during the days with strongly propagating precipitation. Background variations in the physical environment, as opposed to diurnal variations, seem more important for supporting a robust diurnal cycle of precipitation in the region.