Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, School of Atmospheric Physics, Nanjing University of Information Science & Technology, Nanjing, China.
School of Atmospheric Sciences, Sun Yat-Sen University, Guangzhou, China.
Sci Total Environ. 2020 Sep 20;736:139445. doi: 10.1016/j.scitotenv.2020.139445. Epub 2020 May 15.
Compared with interdecadal, interannual, or seasonal scales, the variations of diurnal temperature range (DTR) at the intraseasonal scale and their driving forces are less understood. Using surface meteorological observations and multi-source satellite retrievals during 2013-2017, together with Random Forest modeling, this study examines the intraseasonal variation of summer DTR in the Yangtze River Delta (YRD) region, China, and determines its potential driving factors [i.e., daily maximum/minimum surface air temperature (SAT/SAT), sunshine duration (SSD), rainfall, altitude, land vegetation cover, and land surface thermal environment including daytime/nighttime land surface temperature (LST/LST) and anthropogenic heat flux (AHF)]. It is found that the intraseasonal variation of DTR at both 8-day and monthly scales in the YRD exhibits regional differences and is modulated by different primary factors across the region. The evident intraseasonal variation of DTR, with a peak in June, in the northern YRD, is largely attributable to nighttime temperatures (SAT and LST), which in turn are mainly attributable to different LST responses to the underlying surface cover changes associated with crop rotation. In contrast, as the YRD metropolitan area (MYRD) is covered by a large proportion of built-up surfaces, and the weather stations there are surrounded by a higher surface thermal environment and AHF, the MYRD has stably higher LST and SAT in the whole summer season. Thus, the summer DTR in the MYRD exhibits marginal intraseasonal variations. In the southern YRD, there is also a distinct DTR characteristic, with a maximum in July and minimum in June, since this region is largely covered by forests with constantly high-density vegetation cover, and its DTR variation is mainly forced by SSD, which directly affects SAT. The findings reported here have important implications for understanding the influences of human activities on regional climate and environmental change for other regions of the world that experience various external forcings.
与年代际、年际和季节尺度相比，日内时间尺度上的温度日较差（DTR）变化及其驱动因素了解较少。本研究利用 2013-2017 年期间的地面气象观测和多源卫星反演资料，结合随机森林模型，研究了中国长江三角洲（YRD）夏季 DTR 的季节内变化，并确定了其潜在的驱动因素[即每日最高/最低地面气温（SAT/SAT）、日照时间（SSD）、降雨量、海拔、陆地植被覆盖以及包括白天/夜间陆地表面温度（LST/LST）和人为热通量（AHF）在内的陆地表面热环境]。结果表明，YRD 地区 8 天和月尺度 DTR 的季节内变化存在区域差异，并且由该区域不同的主要因素来调节。在 YRD 的北部，DTR 明显的季节内变化出现在 6 月，主要归因于夜间温度（SAT 和 LST），而夜间温度主要归因于不同的 LST 对与作物轮作相关的下垫面覆盖变化的响应。相比之下，由于 YRD 大都市区（MYRD）被大量的建成表面所覆盖，并且那里的气象站被较高的表面热环境和 AHF 所包围，整个夏季 MYRD 的 LST 和 SAT 都相对较高。因此，MYRD 的夏季 DTR 季节内变化很小。在 YRD 的南部，7 月的 DTR 最高，6 月的 DTR 最低，这是因为该地区主要覆盖着森林，其植被覆盖密度较高，DTR 的变化主要由 SSD 驱动，SSD 直接影响 SAT。本研究的结果对理解人类活动对世界其他地区气候和环境变化的影响具有重要意义，因为这些地区受到各种外部强迫的影响。
