S-PolKa Radar Observations of the Cloud Population in DYNAMO (DYNAmics of the Madden-julian Oscillation (MJO))

本项目使用国家大气研究中心S-波尔卡雷达来解决马登-朱利安振荡动力学野外实验的一个主要目标：记录马登-朱利安振荡动力学在其从抑制到活动再到抑制条件的整个周期中的云群演变。S-波尔卡唯一能够实现这一目标的原因是：(1)它不仅能看到降水对流，而且能看到非降水云；(2)它的双偏振技术能够确定降水对流的微物理以及运动学和降水结构。S-波尔卡雷达与其他雷达合作，提供了有关MJO对流云演化的丰富信息，该项目通过分析S-波尔卡数据并与模式输出进行比较，确定了MJO各个阶段的云团组织和结构。S波段S-波尔卡雷达的高灵敏度提供了对非降水云的观测。在高度抑制的条件下，MJO云团最初以小积云线的形式出现。当这些云中的一部分沉淀时，阵雨形成冷水池，占据了边界层结构。冷池引发更多更大的对流，直到深降水对流开始占据主导地位。S-波尔卡之所以能看到非降水云，是因为它们产生布拉格散射，具有可识别的双偏振特征。对S-波尔卡扫描的分析将记录云层的组织和演变为线条和冷池模式。共置垂直指向Ka波段雷达(DOE KAZR)将添加垂直结构信息。将浅层云的经验特征与细分辨率数值模式输出进行比较。S-波尔卡、S双极化资料揭示了深层对流和中尺度对流系统(MCSs)的主要微物理特征。出现了两种类型的对流天气过程：一种是伴随着层状降水拖曳的锋线，另一种是由对流单体死亡而形成层状降水的非锋线系统。这两类MCS的微物理和运动学结构将由S-波尔卡确定。一个几乎位于同一位置的C波段多普勒雷达(SMART-R)将提供额外的运动学信息。与区域模式的结果进行比较，将有助于深入了解MCSs是如何发展的，以及它们是如何受到风切变和其他环境因素的影响的。将DYNAMO与其他NSF部署(TIMEX和NAME)的观测结果进行比较，可以看出赤道对流与MCSs在陆地和复杂地形附近和上空的副热带地区的不同之处。S-波尔卡和其他雷达得到的浅、深和中尺度对流要素的特征将有助于理解单个分量对MJO聚合云系集的贡献。了解云人口的构成是如何演变的也很重要。S-波尔卡发电机的资料表明，MJO云人口发展是多尺度的。MJO的对流活动期为1-4周。在此期间，对流是由中尺度赤道波控制的，它将对流人口集中到较短的2-4天周期，在此期间对流人口经历类似的增长和下降周期。这个中间尺度很重要，介于云尺度和MJO尺度之间。为了研究这种中尺度行为，S-波尔卡数据将根据印度洋盆地范围内对MJO多尺度行为的模拟进行检验。迪纳摩的一个主要目标是确定MJO在印度洋上空发展时云种群演变的细节。该项目将对实现这一目标做出重大贡献。更广泛的影响：MJO影响全球天气，从亚洲季风的变化到美国冬季天气的变化。该项目对S-波尔卡数据集的分析所提供的物理理解支持了开发更好的模式来预测MJO。此外，该项目还有助于培训女科学家。

This project uses the National Center for Atmospheric Research S-PolKa radar to address a primary goal of the Dynamics of the Madden-Julian Oscillation (MJO) field experiment (DYNAMO): to document the evolution of the cloud population of the MJO throughout its cycle from suppressed to active and back to suppressed conditions. S-PolKa was uniquely capable of achieving this goal because of: (1) its ability to see not only the precipitating convection but also the nonprecipitating clouds; and (2) its dual-polarization technology that allowed determination of the microphysical as well as kinematic and precipitation structure of the precipitating convection. Working in concert with other radars, S-PolKa provided a wealth of information on the convective cloud evolution in the MJO, and this project determines the organization and structure of the cloud population at all of its stages of the MJO through analysis of the S-PolKa data and comparison with model output. The high sensitivity of the S-band S-PolKa radar provided observations of nonprecipitating clouds. In highly suppressed conditions, the MJO cloud population occurs initially in lines of small cumulus. When some of these clouds precipitate, the showers form cold pools, which take over the boundary layer structure. The cold pools trigger more and larger convection until the deep precipitating convection begins to dominate. The nonprecipitating clouds are seen by S-PolKa because they produce Bragg scattering, with identifiable dual-polarization signatures. Analysis of the S-PolKa scans will document the organization and evolution of the clouds into lines and cold pool patterns. A co-located vertically pointing Ka-band radar (the DOE KAZR) will add vertical structure information. The empirical characteristics of the shallow clouds will be compared to fine resolution numerical model output. S-PolKa?s dual-polarization data indicates the dominant microphysical characteristics of deeper convection and mesoscale convective systems (MCSs). Two types of MCSs occurred: squall-lines with trailing stratiform precipitation and non-squall systems in which stratiform precipitation formed from the dying of convective cells. The microphysical and kinematic structures of both types of MCS will be determined from S-PolKa. A nearly co-located C-band Doppler radar (SMART-R)will provide additional kinematic information. Comparison with regional model output will give insight into how the MCSs developed and how they were affected by wind shear and other environmental factors. Comparison of the DYNAMO observations with other NSF deployments (TiMREX and NAME) will indicate how the equatorial convection differs from MCSs in the subtropics near and over land and complex terrain.The characteristics of shallow, deep, and mesoscale convective elements derived from S-PolKa and the other radars will facilitate understanding of the contributions of the individual components to the aggregated cloud ensemble of the MJO. It is also important to understand how the composition of the cloud population evolves. The DYNAMO S-PolKa data shows that the MJO cloud population development is multiscale. The convectively active period of an MJO lasts from 1-4 weeks. Within this period the convection is controlled by intermediate-scale equatorial waves, which concentrate the convective population into shorter 2-4 day periods in which the convective population goes through a similar cycle of growth and decline. This intermediate scale is important, lying between cloud scale and MJO scale. To study this intermediate-scale behavior, the S-PolKa data will be examined in light of Indian Ocean basin-wide simulations of the multiscale behavior of the MJO.A primary goal of DYNAMO was to determine the details of the evolution of the cloud population of the MJO as it develops over the Indian Ocean. This project will be a major contribution toward the achievement of that aim.Broader Impacts:The MJO affects weather globally, from variations in the Asian monsoon to variations in winter weather over the U.S. The physical understanding provided by this project's analysis of the S-PolKa dataset underpins the development of better models to forecast the MJO. In addition, the project contributes to the training of women scientists.