Cross-equatorial northerly surge (CENS) is known to cause torrential rainfall over Java Island in the Maritime Continent. Some studies indicated that the rainfall increase is attributed to changes in the diurnal cycle of rainfall (DCR) in northwestern Java. It is not well understood whether the DCR changes are present in the other parts of Java Island and whether the changes are similar to those in northwestern Java. This study performs climatological analyses to investigate the regional variation of the influence of the CENS on the DCR over Java Island using IMERG and ERA5 data sets of 20 years of boreal winter. We find that there are differences in intensity, timing, and coverage of DCR responses over western, central, and eastern Java. CENS modifies the timing of coastal rainfall on the northern coast, resulting in early morning rainfall enhancement owing to the convergence between the incoming northerlies and land breeze. A small increase in early morning rainfall is observed in eastern Java, possibly due to the northerly flow gaining more zonal components on the eastern coast, which then results in relatively weaker convergence than the western coast. The timing of early morning rainfall appears to be slightly different between the three areas. CENS is also found to suppress afternoon rainfall inland because of increasing static stability due to cold air advection from the north. The suppression varies from western to eastern Java, with the largest suppression seen in western Java. Relatively narrower and wider suppression areas are found in central and eastern Java, respectively. These differences are attributed to the topography characteristics of Java.

中文翻译：

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越赤道偏北风潮对爪哇岛降雨日周期影响的区域变化

据了解，跨赤道北风潮（CENS）会在海洋大陆的爪哇岛造成暴雨。一些研究表明，降雨量增加归因于爪哇西北部降雨日周期（DCR）的变化。目前尚不清楚爪哇岛其他地区是否也存在 DCR 变化以及这些变化是否与爪哇岛西北部的变化类似。本研究利用 IMERG 和 ERA5 20 年北半球冬季数据集进行气候学分析，调查 CENS 对爪哇岛 DCR 影响的区域变化。我们发现爪哇西部、中部和东部 DCR 响应的强度、时间和覆盖范围存在差异。CENS 修改了北部海岸的沿海降雨时间，由于北风和陆风的交汇，导致清晨降雨量增加。爪哇东部清晨降雨量小幅增加，可能是由于北向气流在东海岸获得更多纬向成分，导致辐合相对较西海岸弱。这三个地区的清晨降雨时间似乎略有不同。CENS 还发现，由于来自北方的冷空气平流增加了静态稳定性，CENS 抑制了内陆下午的降雨。西爪哇省和东爪哇省的镇压情况各不相同，其中西爪哇省的镇压规模最大。爪哇中部和东部分别发现相对较窄和较宽的压制区域。