Boreddy Suresh K R, Nair Vijayakumar S, Babu S Suresh
Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022, India.
Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022, India.
Sci Total Environ. 2023 Nov 25;901:166461. doi: 10.1016/j.scitotenv.2023.166461. Epub 2023 Aug 20.
Aerosol-bound water, a ubiquitous and abundant component of atmospheric aerosols, has an impact on regional climate, visibility, human health, the hydrological cycle, and atmospheric chemistry. Yet, the intricate relationship between aerosol liquid water (ALWC) and chemical composition and relative humidity (RH) was not well understood. The present study explores ALWC derived from the ISORROPIA II model using real-time, high-resolution data of non-refractory submicron chemical species and meteorological parameters (temperature and RH) collected over the Indian Ocean as part of the ICARB (Integrated Campaign for Aerosols, Gases, and Radiation Budget)-2018 experiment. Results show that ALWC values over the South Eastern Arabian Sea (SEAS) were found to be higher by 4-6 times than those observed over the Equatorial Indian Ocean (EIO) due to a large decrease in aerosol loading from SEAS to EIO. ALWC peaked in the early morning hours (4:00-7:00), with greater values during the nighttime and lower values during the daytime across SEAS, which is comparable with RH variation. While the ratio of organics-to-SO mass fraction linearly decreased with increasing mass-based growth factors (MGFs) over EIO, such a scenario was not observed over SEAS. The latitudinal gradient of mass fraction of ALWC had shown a decrease towards EIO, consistent with organic fraction. The extinction coefficient of the dry mass of submicron particles is noticeably increased by 40 % by ALWC over SEAS and EIO. Moreover, ALWC could enhance the aerosol negative forcing by an average of 66 % (64 %) over SEAS (EIO) at the top of the atmosphere during the cruise period. These inferences imply that ALWC is the key factor in assessing the role of aerosols on atmospheric radiative forcing. Overall, the present study highlights the serious need to consider the ALWC in climate forcing simulations, particularly in moist tropical environments where their effect can be significant.
气溶胶结合水是大气气溶胶中普遍存在且含量丰富的成分，对区域气候、能见度、人类健康、水文循环和大气化学都有影响。然而，气溶胶液态水（ALWC）与化学成分及相对湿度（RH）之间的复杂关系尚未得到充分理解。本研究利用作为ICARB（气溶胶、气体和辐射收支综合观测）-2018实验一部分在印度洋收集的非难熔亚微米化学物种和气象参数（温度和RH）的实时高分辨率数据，探索了源自ISORROPIA II模型的ALWC。结果表明，由于从阿拉伯海东南部（SEAS）到赤道印度洋（EIO）气溶胶负荷大幅下降，SEAS上空的ALWC值比EIO上空观测到的值高4至6倍。ALWC在清晨时段（4:00 - 7:00）达到峰值，在整个SEAS地区夜间值较大，白天值较低，这与RH变化情况相当。虽然在EIO上有机物与SO质量分数之比随基于质量的增长因子（MGFs）增加呈线性下降，但在SEAS上未观察到这种情况。ALWC质量分数的纬向梯度向EIO方向减小，与有机组分一致。亚微米颗粒干质量的消光系数在SEAS和EIO上因ALWC而显著增加40%。此外，在巡航期间，ALWC可使大气顶层的气溶胶负强迫在SEAS（EIO）上平均增强66%（64%）。这些推断意味着ALWC是评估气溶胶对大气辐射强迫作用的关键因素。总体而言，本研究突出表明在气候强迫模拟中，特别是在其影响可能显著的潮湿热带环境中，迫切需要考虑ALWC。
