夏季青藏高原臭氧谷双心结构的上平流层中心形成机制

Since ozone hole has been found, ozone depletion always attracts community interest very much. The ozone valley over the Tibetan Plateau (OVTP) is the strongest seasonal ozone low out of the polar region. Researches on the OVTP mainly focus on the ozone low near tropopause and suggest dynamic process is dominant in the ozone depletion. The applicant (2015) found double-core structure of the OVTP from multiple satellite observations and reanalysis data. There is another ozone depletion center over the Tibetan Plateau in the upper stratosphere. We diagnosed formation mechanism of the upper core using a new generation satellite data set with high resolution and presumed chemical processes may play an important role, which still has uncertainty. Therefore, in the proposal, we managed to uncover the Upper Stratospheric OVTP in Summer (USOS), using multiple satellite observations, reanalysis data and chemical climate model. Procedures are as follows. 1) we will diagnose dynamic transport flux, EP flux and reveal dynamic effect on the USOS, using satellite data, reanalysis data and model output data. 2) we will diagnose chemical effect on the USOS, using chemical reaction rates, reactants concentration, temperature and ultraviolet radiation from model output. 3) we will run 3 sensitivity tests and uncover chemical effects of different factors. Model will be restarted contiually with zonal average of the key atmospheric compositions as initial fields and impulse, which can uncover effect of the key compositions. Temperature will be replaced by the zonal mean values when model calculate the chemical reaction rate coefficient, which can reveal effect of the temperature. Surface albedo will be used as zonal mean and zonal mean cloud characteristics will be used as continual impulse to model, which can show effect of upward ultraviolet radiation reflected by, scattered by and transmitted through cloud.

青藏高原是全球最强的非极地季节性臭氧低值区，其最强的低值中心位于对流层顶附近，动力过程起主导作用。2015年，申请人从多套卫星和再分析资料中发现了夏季青藏臭氧谷的双心结构。除对流层顶外，上平流层也存在臭氧损耗中心。尽管我们通过一套新一代高分辨率卫星资料，推测化学过程起重要作用，但仍存在不确定性。因此，本项目拟利用多套卫星、再分析资料和化学气候模式，揭示夏季青藏高原臭氧谷上平流层中心的形成机制。1）利用卫星和模式的输出资料，诊断动力输送通量和行星波的作用，揭示其动力作用。2）利用模式输出的反应速率、反应物浓度、温度、紫外辐射，诊断化学作用。3）运行三组敏感性试验，利用关键成分纬圈平均作为初始场，不断重启模式；在反应速率系数计算中置入纬圈平均温度；在地表反照率计算中置入纬圈平均值，利用纬圈平均的云作为初始场不断重启模式，揭示关键成分、温度和向上反射、散射和透射紫外辐射对化学过程的作用。

利用WACCM4模式模拟了夏季青藏高原臭氧谷双心结构。评估了在夏季上平流层青藏高原臭氧谷附近模式对大气成分、温度和风场的模拟性能。利用多源卫星资料、再分析资料和模式输出的臭氧和风场资料，研究了动力输送对夏季青藏高原臭氧谷双心结构的上平流层中心的作用。利用模式输出资料，诊断了化学反应对夏季青藏高原臭氧谷双心结构的上平流层中心的作用。设计并运行敏感性试验，揭示了关键成分、温度、辐射在化学作用中扮演的角色。结果表明：利用WACCM4模拟青藏高原臭氧谷的双心结构，通过比较春夏秋冬四季青藏高原上空的臭氧纬偏廓线的分布，模式模拟出的臭氧谷的垂直结构与季节变化，都和卫星资料接近。对于上平流层低值中心的模拟，位置偏东，强度相近。臭氧输送使得夏季青藏高原臭氧谷上部中心加强，其中定常输送起到主要作用，瞬变输送作用较弱使得臭氧谷略微减弱。定常和瞬变输送的共同作用，从纬向和经向两个方向来看，纬向臭氧输送使得臭氧谷加强且强度较强，经向臭氧输送使得臭氧谷减弱且强度较弱。氯与臭氧的反应以及氧化氯和氧原子的反应分别主要在春夏冬和春夏对青藏高原附近上平流层的臭氧低值中心的形成起着促进作用。辐射和温度的纬向不均匀性减弱了青藏高原附近上平流层的臭氧低值。以上结果加深了学界对青藏高原臭氧低值区形成机制的认识。