Starzec M, Mullendore G L, Homeyer C R
Department of Atmospheric Sciences, University of North Dakota, Grand Forks, ND, USA.
School of Meteorology, University of Oklahoma, Norman, OK, USA.
J Geophys Res Atmos. 2020 Mar 16;125(5). doi: 10.1029/2019jd031164. Epub 2020 Feb 14.
To better constrain model simulations, more observations of convective detrainment heights are needed. For the first time, ground-based S band radar observations are utilized to create a comprehensive view of irreversible convective transport over a 7-year period for the months of May and July across the United States. The radar observations are coupled with a volumetric radar echo classification scheme and a methodology that uses the convective anvil as proxy for convective detrainment to determine the level of maximum detrainment (LMD) for deep moist convection. The LMD height retrievals are subset by month (i.e., May and July), by morphology (i.e., mesoscale convective system, MCS, and quasi-isolated strong convection, QISC), and region (i.e., northcentral, southcentral, northeast, and southeast). Overall, 135,890 deep convective storms were successfully sampled and had a mean LMD height of 8.6 km or tropopause-relative mean LMD height of -4.3 km; however, LMD heights were found to extend up to 2 km above the tropopause. May storms had higher mean tropopause-relative LMD heights, but July storms contained the highest overall LMD heights that more commonly extended above the tropopause. QISC had higher mean tropopause-relative LMD heights and more commonly had LMD heights above the tropopause while only a few MCSs had LMD heights above the tropopause. The regional analysis showed that northern regions have higher mean LMD heights due to large amounts of diurnally driven convection being sampled in the southern regions. By using the anvil top, the highest possible convective detrainment heights extended up to 6 km above the tropopause.
为了更好地限制模型模拟，需要更多对流消散高度的观测数据。首次利用地基S波段雷达观测数据，对美国5月和7月为期7年的不可逆对流输送情况进行了全面观测。雷达观测数据与一种体积雷达回波分类方案以及一种使用对流砧作为对流消散代理的方法相结合，以确定深厚湿对流的最大消散高度（LMD）。LMD高度反演数据按月份（即5月和7月）、形态（即中尺度对流系统、MCS，以及准孤立强对流、QISC）和区域（即中北部、中南部、东北部和东南部）进行了子集划分。总体而言，成功采样了135,890次深厚对流风暴，其平均LMD高度为8.6千米，或相对于对流层顶的平均LMD高度为-4.3千米；然而，发现LMD高度可延伸至对流层顶上方2千米处。5月的风暴相对于对流层顶的平均LMD高度更高，但7月的风暴总体LMD高度最高，且更常延伸至对流层顶上方。QISC相对于对流层顶的平均LMD高度更高，且更常出现LMD高度高于对流层顶的情况，而只有少数MCS的LMD高度高于对流层顶。区域分析表明，由于在南部地区采样了大量由昼夜驱动的对流，北部地区的平均LMD高度更高。通过使用砧顶，对流消散的最高可能高度延伸至对流层顶上方6千米处。
