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An assessment of factors limiting tropical congestus cloud-top heights.

机译：限制热带充血云顶高度的因素的评估。

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摘要

I investigate the capping mechanisms behind mid-level cumulus congestus clouds. Two theories are analyzed using two months (January-February 2007) of collocated data between the Atmospheric InfraRed Sounder (AIRS) onboard Aqua and the Cloud Profiling Radar (CPR) onboard CloudSat, as well as data from the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (a, ERA) Interim Reanalysis.;The first theory is that dry, free-tropospheric air caps convection due to increased detrainment of unsaturated air at cloud-top, limiting the cloud's buoyancy. This theory is given credence by the sharp differences in AIRS relative humidity (RH) between three cloud categories separated by CPR cloud-top height. Broad layers are noted where the difference in local RH is statistically significant. Congestus occurs more frequently than deep convective clouds when the free-tropospheric RH is less than 30%. Mean RH from the ERA reanalysis shows that RH increases in the midtroposphere (around 600 hPa) by a specific difference of 3% in RH in the presence of deep clouds, compared to RH in the presence of congestus.;The second theory is that a decreased vertical temperature lapse rate, dT/dp, would slow cloud growth, creating a mode of cloud-top heights at the stable layer as clouds lose buoyancy. The signal for lapse rate changes in the AIRS data, however, is not as strong as the signal for RH differences. Near 600-400 hPa, roughly the region where congestus cloud-top heights are located, no significant difference in lapse rates is noted between congestus and deep clouds; in fact, the mean values suggest that congestus clouds appear in more unstable atmospheres than deep clouds. Only slight differences in temperature and lapse rate are noted in ERA data as well. These results suggest that drier air may play a greater role in limiting congestus cloud-top heights than increased atmospheric stability.;Five years of relative humidity (RH) observations from the Atmospheric Infrared Sounder (AIRS) instrument aboard the Aqua satellite are then analyzed to identify areas of anomalously dry air between 600 and 400 hPa over deep convective regions of the tropical oceans. Back trajectories are then calculated for each observed parcel.
机译：我研究中层积云充血云背后的封盖机制。使用两个月（2007年1月至2007年2月）在Aqua船上的大气红外测深仪（AIRS）和CloudSat船上的云剖析雷达（CPR）之间并置的数据以及来自欧洲中距离天气中心的数据对两种理论进行了分析。预报（ECMWF）重新分析（a，ERA）临时重新分析。；第一种理论是，由于云顶顶部不饱和空气的增加增加，干燥的，对流层空气帽对流，限制了云的浮力。 AIRS相对湿度（RH）在由CPR云顶高度分开的三个云类别之间的急剧差异为该理论提供了可信度。在局部RH的差异在统计学上显着的地方，应注意有较宽的层。当对流层相对湿度小于30％时，比深对流云更容易发生充血。 ERA再分析的平均RH表明，与存在充血的RH相比，深云存在下RH在对流层中层（约600 hPa）的相对湿度增加3％的特定差异;第二种理论是垂直温度下降速率dT / dp的降低会减慢云的生长，由于云失去浮力，会在稳定层上形成云顶高度的模式。但是，AIRS数据中的失败率变化信号不如RH差异信号强。在600-400 hPa附近，大约是充血云顶高度所在的区域，充血和深云之间的消失率没有显着差异。实际上，平均值表明充血云比深云出现在更不稳定的大气中。 ERA数据中也仅记录了温度和流失率的细微差异。这些结果表明，干燥的空气在限制充血云顶高度方面可能比增加大气稳定性发挥更大的作用;然后对Aqua卫星上的大气红外测深仪（AIRS）仪器进行的五年相对湿度（RH）观测进行了分析，以得出以下结论：确定热带海洋深对流区域600至400 hPa之间异常干燥的空气区域。然后为每个观察到的地块计算后退轨迹。

著录项

  • 作者

    Casey, Sean Patrick.;

  • 作者单位

    Texas A&M University.;

  • 授予单位 Texas A&M University.;
  • 学科 Atmospheric Sciences.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 103 p.
  • 总页数 103
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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