In situ and remote sensing observations of water vapor are analyzed to assess the evidence for direct convective hydration of the lower stratosphere. We have examined several hundred balloon‐borne and airborne in situ measurements of lower stratospheric humidity in the tropics and northern midlatitudes. We find that the tropical lower stratospheric H₂O enhancements above the background occur quite infrequently, and the height of the enhancements is within about 1 km of the cold‐point tropopause. Following Schwartz et al. (2013, https://doi.org/10.1002/grl.50421), we examine the anomalously high (above 8 ppmv) water vapor mixing ratios retrieved by the Aura Microwave Limb Sounder (MLS) at 100‐ and 82‐hPa pressure levels, and we determine their vertical location relative to the local tropopause based on both Global Forecast System (GFS) operational analysis and the ERA5 reanalysis temperature data. We find that essentially all of the >8‐ppmv MLS water vapor measurements over the extratropical North American monsoon region are above the relatively low lapse‐rate tropopause in the region, and most are above the local cold‐point tropopause. Over the Asian monsoon region, most (80/90%) of the high H₂O values occur below the relatively high‐altitude local lapse‐rate/cold‐point tropopause. Anomalously high MLS water vapor retrievals at 100 and 82 hPa almost never occur in the deep tropics. We show that this result is consistent with the in situ observations given the broad vertical averaging kernel of the MLS measurement. The available evidence suggests that direct hydration of the lower stratosphere is important over North America during the monsoon season but likely has limited impact in the tropics.

中文翻译：

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平流层下层直接对流水化的观测证据评估

对水蒸气的原位和遥感观测进行了分析，以评估平流层下部直接对流水化的证据。我们已经检查了热带和北中纬度地区平流层较低湿度的数百个气球传播和空中传播测量结果。我们发现热带低平流层H ₂O在背景之上的增强很少发生，并且增强的高度在距对流层顶冷点约1 km之内。继Schwartz等。（2013年，https：//doi.org/10.1002/grl.50421），我们研究了Aura微波Limb Sounder（MLS）在100-hPa和82-hPa压力下获得的异常高的水蒸气混合比（高于8 ppmv）。级别，然后根据Global Forecast System（GFS）运营分析和ERA5重新分析温度数据确定它们相对于局部对流层顶的垂直位置。我们发现基本上所有>北美温带季风区的8 ppmv MLS水汽测量值高于该地区相对较低的流失率对流层顶，而大部分高于局部冷点对流层顶。在亚洲季风区，大多数（80/90％）高H ₂ O值发生在相对较高的局部失速/冷点对流层顶之下。在深热带地区，在100和82 hPa处异常高的MLS水汽反演几乎从未发生过。我们表明，给定MLS测量的宽垂直平均核，该结果与原位观测结果一致。现有证据表明，在季风季节，平流层下部直接水合作用对北美地区很重要，但对热带地区的影响可能有限。