Characteristics Of Penetrating Convection And Its Impacts On Ozone Variation In The UTLS

Deep convection penetrating the tropopause, also known as penetrating convection, plays a crucial role in controlling the budget of energy, water vapor, as well as other trace constituents of the tropical upper troposphere and lower stratosphere (UTLS). In order to understand these important impacts, a number of ways to observe the distribution and frequency of penetrating convection from spaceborne platforms have been proposed. The launch of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) provides a new opportunity to study the vertical structure and the intensity of tropical convection. However, since the previous studies do not use the accurate tropopause data, TRMM PR and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) observations are first combined to understand the characteristics of deep and penetrating convection over tropics and subtropics in this thesis. Meanwhile, we aim to better quantify the deep convective temperature and water vapor signals in the UTLS using multiple datasets. In addition, the contribution of typhoons to ozone variation in the UTLS over the western North Pacific is also estimated. The major findings are presented as follows.(1) Characteristics of Global thermal tropopauseClimatological tropopause height reaches its maximum16.5km over tropics and sharply decreases in subtropics, settling to values of9km at the poles. Meanwhile, the static stability over tropopause shows a unique horizontally and vertically variation, with maxima located0-1km and1-3km above the tropopause. The lower maximum is centered at the equator; the upper maximum has its largest magnitude at10°-15°latitude in both hemispheres. It can be found that static stability maxima are significant over Central Africa, West Pacific and East Pacific between December and May. Moreover, static stability minima occur over the subtropics. The fluctuations of tropopause caused by convective clouds are limited within1km. The results reveal that tropopause over tropics and subtropics is modified by both the convective activity and processes in the UTLS, rather than the convective activity.The mean deviations between COSMIC and IGRA tropopause parameters are (0.02±0.54) km for height,(1.61±15.44) hPa for pressure,(-0.06±2.25) K for temperature and (-0.52±5.59) K for potential temperature. Comparisons of tropopause height between COSMIC and NCEP are (0.20±0.57) km and (-0.16±0.90) km during December-January-February and June-July-August, respectively. NCEP tropopause is2-km higher over the tropics and2-km lower over subtropics.Multiple tropopause events have a strong tendency to follow the subtropical jet and are presented over Andes throughout the year. Thickness of Multiple tropopause events is6km at subtropical jet. During December-May, there is a decrease in multiple tropopause frequency over the eastern Pacific and western Atlantic, which is regions of Rossby wave breaking triggered by jet weakening. Multiple tropopause is accompanied by a low static stability between tropopauses.(2) Characteristics of Penetrating ConvectionIt is found that0.005～0.05%of the total PR pixel numbers can penetrate the tropopause.Penetrating Convection shows regional variability and seasonal variations. Penetrating convection is more frequent over land than over ocean. The highest frequency of penetrating convection is found over ITCZ, Asian Summer Monsoon, Central Africa and Amazon. The average rain top of penetrating convection ranges from14to18.5km.Results also show that penetrating convection clouds are frequently observed within an equivalent radius of2.5km. The vertical distributions show that most of penetrating convective clouds overshoot less than4.5km above the tropopause. The regional statistics indicate that the penetrating convective clouds are wider and taller in the Asian monsoon region.The relationship between stratosphere-troposphere flux and the horizontal extents of penetrating convective clouds is demonstrated to be strong in the Asian monsoon region and weak in the other region of tropics and extratropics. Therefore, penetrating convection of Asian monsoon region may play a significant role in the stratosphere-troposphere exchange.(3) The role of deep convection on temperature and water vapor in the UTLSThere is an evident regional difference in deep convective structures. Deep convection is strongest over land and is weakest over ocean, with monsoonal convection intermediate between them. Latent heat profiles shows similar characteristic. Major regional difference on convective structure are related to updraft and microphysics. Temperature anomaly profile reveals a wave like response to deep convection:warming middle tropopause and upper half of the UTLS and cooling the lower UTLS. The most pronounced temperature signal appears for temperature profiles in proximity to penetrating convection.Both deep and penetrating convection can hydrate the troposphere. The most significant hydration can be found over land (water vapor mixing ration increase more than40%), less over monsoon region, and least over ocean. Meanwhile, deep and penetrating convection can dehydrate the environment near cloud top. Deep convection shows a stronger dehydration.(4) Impact of typhoon on the ozone variations in the UTLS over the northwest PacificDuring the passage of Typhoon Hai-Tang in2005over the northwest Pacific, low values of ozone column and ozone mixing ratio above200hPa are observed right above the typhoon’s track, a result due to the strong upward propagation of air associated with overshooting convection in typhoon. A comparative analysis of different stages of Hai-Tang suggests that in the region where typhoon has higher intensity the troposphere-to-stratosphere transport is enhanced.The statistic analysis for typhoon over the northwest Pacific during2004-2012suggests that0.18%of the convective pixel numbers reach the tropopause, with a weighted averaged equivalent radius and penetrating depth of4.0km and0.49km, respectively. Typhoons cause ozone column between200hPa and50hPa (OCUTLS) decrease significantly within10°radius, with-5DU (about-5%of the local OCTULS). The strongest decrease appears within0.5°-3°radius of the typhoon center.This thesis reveal the deep convection penetrating the accurate tropopause. In addition, we exhibit precipitation, temperature and water vapor structures of penetrating convection in the UTLS and offer new guidance for categorization of convection over land, monsoon and ocean for modeling studies.