热带云的非绝热加热结构及其对热带大气环流的影响

The latent heat release and the radiative heating of tropical cloud systems significantly affect the vertical structure of diabatic heating in tropics, which strongly modulates the large-scale circulation. This proposal develops an unique method to combine measurements from MODIS IR, AMSR-E microwave, CloudSat Cloud Profiling Radar, CALIPSO lidar onboard A-Train satellites to identify and characterize mesoscale convective systems (MCSs), Non-MCS deep cloud systems, upper troposphere ice clouds not connected to deep convection, large fields of stratus and stratocumulus, cumulus, cumulus congestus and smaller isolated cumulonimbus. By using the cloud vertical profile (feature) and microphysics paramters retrieved from CloudSat CPR and CALIPSO lidar measurements, the radiative heating of these types of cloud systems can then be determined. To compile the full diabatic heating structre dirunal averaged radiative heating profiles need to be determined. First the instantaneous radiative heating profile will be computed by using the Fu-Liou radiative transfer model following the same method used by the standart CloudSat Fluxes and Heating Rates Product. After being validated/compared with the CloudSat product, the cloud radiative heating will be recomputed to obtain the dirunally averaged profile along with estimates of uncertainties of computed heating profiles. Then empirical vertical profiles of radiative heating of each type of system can be obtained through the compositing method. On the other hand, the latent heat structure associated with each type of systems will be sorted out by using TRMM PR measurements following existed methods from Global Precipitation Measurement (GPM) scientists. Additional information about the variability of the latent heating profile of deep convective systems across different regions will be considered. Realistic estimates of shallow isolated precipitaing system will be used. Latent heat of shallow (light rain) systems will be estimated with CloudSat in stead of PR due to the detection limit of PR. These composite modes associated with each type of systems will be compiled to generate the tropical 3-D diabatic heating structure and used with simple models to determine the steady state response of large-scale circulation to each radiatively important cloud systems. The objective of this proposal is to better estimate the radiative contribution to the tropical diabatic heating structure of each type of cloud systems and andvace our knowledge about their impacts on the general circulation. This will also build the foundation for more sophisticated weather and climate model to more realistically include the effects of tropical clouds.

热带云系统形成过程中的潜热释放和云对辐射传输的影响是决定大气非绝热加热垂直分布重要因子，进而显著影响大气环流。本项目利用独特的方法结合2006-2011年多平台卫星观测（红外,微波,云雷达,激光雷达）客观地识别中尺度对流系统（MCSs）和其他深对流系统、与MCSs无关的高空冰云、大面积的层云和层积云及积云，浓积云与小的积雨云等独立的小的对流系统。结合新颖的CloudSat云雷达与CALIPSO激光雷达对云的垂直结构的观测与Fu-liou辐射传输模式计算云的日平均辐射加热廓线。进而通过合成分析的方法从统计上量化各种云系统的辐射加热廓线。结合辐射加热和对潜热的估算一起与简单的环流模式揭示大气环流对不同云系统非绝热加热贡献的响应。本项目目标是进一步认识不同云系统的热带3维辐射加热和潜热结构及其对环流的影响，从而为在更复杂先进的天气、气候模式中更真实的模拟热带云的影响打下基础。

云是影响热带大气非绝热加热结构及大气上界辐射能量平衡的重要因子， 进一步理解影响其特征的现象、过程和机理对量化其对辐射及环流的影响有重要意义。由于云的特征依赖于影响其发展的物理过程，合理的在模式里模拟云不仅仅需要在统计上知道云的时空特征，而要更好的理解产生不同云的过程和机理。因此基于云系统的研究相对于目前在气候研究中被广泛采用的空间格点数据统计更有利于对过程的理解。本研究主要利用2006-2011年的A-Train MODIS、AMSR-E、CloudSat和CALIPSO的观测客观地识别深对流系统，并考察深对流系统在热带重要的天气气候现象中的行为与变化特征及其阐释相关机理。并结合其他云系统资料进一步量化不同云系统对气候尺度大气辐射及环流的影响..本项目考察了深对流系统在热带重要的低频振动MJO过程中的行为与变化特征及其相关机理。发现总体上聚集型系统内部特征和降雨类型更多由层云降雨主导，但是在MJO深对流激发之后深对流系统宏观变化与其内部特征变化反向（即宏观上由聚集型向离散型过渡的同时其内部结构体现更多层云降雨特征）。并发现聚集型系统的发生和对流层中层水汽高值密切相关。大的离散型深对流系统虽然与聚集型系统有相似的内部特征，但是自由对流层水汽、周边浅对流及中等程度对流发生频次都与聚集型系统更为密切相关。上这些发现表明传统上对有组织深对流系统形成的机理的认知并不足以解释聚集型系统形成的原因，聚集型系统相对于大的离散型系统可能表征了更高层面的深对流系统自聚集现象。本项目研究并发现聚集型系统与水汽的相关并不局限于MJO，而可能是与对流本身过程相关。另发现聚集性可能是影响深对流生成砧状云效率的最重要的因素。.本项目研究发现日变化对云辐射加热廓线的影响与MJO等大尺度对流相位和尺度显著相关，并发现深对流系统潜热结构事实上与深对流系统类型和尺度相关。这些发现进一步表明云的非绝热加热与影响不同系统生消的物理因素相关，仅仅根据格点数据做统计无法正确估算云的非绝热加热。本项目研究建立了依据系统类型重构热带不同云系统非绝热加热的方法，为考察大气环流对不同云系统加热分量的响应打下基础。

内容获取失败，请点击重试