Downdrafts and cold pool characteristics for strong mesoscale convective systems (MCSs) and isolated, unorganized deep precipitating convection are analyzed using multi-instrument data from the DOE Atmospheric Radiation Measurement (ARM) GoAmazon2014/5 campaign. Increases in column water vapor (CWV) are observed leading convection, with higher CWV preceding MCSs than for isolated cells. For both MCSs and isolated cells, increases in wind speed, decreases in surface moisture and temperature, and increases in relative humidity occur coincidentally with system passages. Composites of vertical velocity data and radar reflectivity from a radar wind profiler show that the downdrafts associated with the sharpest decreases in surface equivalent potential temperature (iθ/isube/sub) have a probability of occurrence that increases with decreasing height below the freezing level. Both MCSs and unorganized convection show similar mean downdraft magnitudes and probabilities with height. Mixing computations suggest that, on average, air originating at heights greater than 3?km must undergo substantial mixing, particularly in the case of isolated cells, to match the observed cold pool iθ/isube/sub, implying a low typical origin level. Precipitation conditionally averaged on decreases in surface equivalent potential temperature (Δiθ/isube/sub) exhibits a strong relationship because the most negative Δiθ/isube/sub values are associated with a high probability of precipitation. The more physically motivated conditional average of Δiθ/isube/sub on precipitation shows that decreases in iθ/isube/sub level off with increasing precipitation rate, bounded by the maximum difference between surface iθ/isube/sub and its minimum in the profile aloft. Robustness of these statistics observed across scales and regions suggests their potential use as model diagnostic tools for the improvement of downdraft parameterizations in climate models.
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机译：使用来自DOE大气辐射测量（ARM）GoAmazon2014 / 5计划的多仪器数据，分析了强中尺度对流系统（MCS）和孤立的，无组织的深降水对流的气流和冷池特征。观察到柱水蒸气（CWV）的增加导致对流，MCS之前的CWV高于隔离细胞。对于MCS和隔离的电池，风速增加，表面湿度和温度降低以及相对湿度增加与系统通道同时发生。雷达风廓线仪的垂直速度数据和雷达反射率的合成表明，与表面等效电位温度（θ e ）的急剧下降相关的下降气流有发生的可能性随着高度降低到冻结水平以下而增加。 MCS和无组织的对流都显示出相似的平均下降气流幅度和高度概率。混合计算表明，平均而言，源自高度大于3？km的空气必须进行大量混合，尤其是在隔离细胞的情况下，以匹配观察到的冷池θ e ，这意味着较低的典型原点水平。由于表面负电势温度（Δθ e e）的负值最大，有条件地对表面等效电势温度（Δθ e e）的减小进行平均值与高降水概率相关。降水引起的Δθ e 的更有条件的条件平均值表明，θ e 的水平随着增加而减小降水率，由表面θ e 之间的最大差和其在高空剖面中的最小值之间的界限确定。这些在各个尺度和地区观察到的统计数据的稳健性表明，它们潜在地用作模型诊断工具，以改善气候模型中的下降气流参数化。
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