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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >MARINE BOUNDARY LAYER STRUCTURE AND FRACTIONAL CLOUDINESS
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MARINE BOUNDARY LAYER STRUCTURE AND FRACTIONAL CLOUDINESS

机译：海洋边界层结构和分数周期

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Radiosonde data collected during the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE), 1987, the Atlantic Stratocumulus Transition Experiment (ASTEX), 1992, and the Tropical Instability and Waves Experiment (TIWE), 1990, were used to develop four composite thermodynamic soundings of the marine boundary layer for cloud conditions ranging from solid stratocumulus to trade cumulus and sea surface temperatures ranging from 16 degrees to 27 degrees C. Average cloud fraction and cloud base height for the composite soundings were estimated using laser ceilometers located at each of the four sites. The average fractional cloudiness varied from 0.83 off the coast of California at San Nicolas Island (33.4 degrees N, 119.6 degrees W) during FIRE to 0.26 over the central equatorial Pacific during TIWE (0 degrees N, 140.0 degrees W). During ASTEX, two sites in the vicinity of the Azores generally experienced cloud conditions characterized by cumulus clouds penetrating into a stratocumulus layer. At the more northerly site, the island of Santa Maria (37.0 degrees N, 25.2 degrees W), the average fractional cloudiness was 0.67 compared with 0.40, 1000 km downstream at the German R/V Valdivia (28.0 degrees N, 24.0 degrees W). The two composite soundings from ASTEX and the composite sounding from TIWE indicate decoupled boundary layer structures. These three soundings have a cloud layer that is conditionally unstable and show a systematic increase in relative humidity with increasing fractional cloudiness. The effect of cloud top entrainment on fractional cloudiness was evaluated. For the four composite soundings the fractional cloudiness decreases as the slope of the normalized w-theta mixing line increases (greater instability), but this decrease is 4 times less than that from previous studies. Fractional cloudiness diagnosed from parameterizations using cloud layer relative humidity compares well with the observed mean cloudiness. [References: 49]
机译：1987年，在第一个国际卫星云气候项目（ISCCP）区域实验（FIRE），1992年大西洋层积云过渡实验（ASTEX）和1990年热带不稳定性和波浪实验（TIWE）中收集了探空仪数据。海洋边界层的四种复合热力学测深，范围从固态平积云到贸易积云，海表温度范围从16摄氏度到27摄氏度。云层分布的平均云量和云底高度是使用位于四个站点中的每个站点。在FIRE期间，平均分数混浊度从加利福尼亚圣尼古拉斯岛海岸的0.83（北纬33.4度，西经119.6度）变化到TIWE赤道太平洋中部（北纬0度，西经140.0度）为0.26。在ASTEX期间，亚速尔群岛附近的两个地点通常都经历了云状条件，其特征是积云渗透到平积层中。在更北端的圣玛丽亚岛（北纬37.0度，西经25.2度），平均分数混浊为0.67，而德国瓦尔迪维亚R / V（北纬28.0度，西经24.0度）则为0.40，下游为1000 km。 。 ASTEX的两个复合测深和TIWE的复合测深表明边界层结构是分离的。这三个测深的云层在条件上是不稳定的，并且随着相对混浊度的增加，相对湿度有系统地增加。评估了云顶夹带对分数云度的影响。对于这四个复合测深，分数浊度随归一化w-theta混合线的斜率增加而减小（更大的不稳定性），但这种降低比以前的研究少4倍。使用云层相对湿度通过参数化诊断的分数浊度与观察到的平均浊度比较好。 [参考：49]

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