North Africa experienced a severe heatwave in April 2010 with daily maximum temperatures (\(T_{max}\)) frequently exceeding \(40\,^{\circ }\mathrm{C}\) and daily minimum temperatures (\(T_{min}\)) over \(27\,^{\circ }\mathrm{C}\) for more than five consecutive days in extended Saharan and Sahelian areas. Observations show that areas and periods affected by the heatwave correspond to strong positive anomalies of surface incoming longwave fluxes (\(LW_{in}\)) and negative anomalies of incoming shortwave fluxes (\(SW_{in}\)). The latter are explained by clouds in the Sahara, and by both clouds and dust loadings in the Sahel. However, the strong positive anomalies of \(LW_{in}\) are hardly related to cloud or aerosol radiative effects. An analysis based on climate-model simulations (CNRM-AM) complemented by a specially-designed conceptual soil-atmospheric surface layer model (SARAWI) shows that this positive anomaly of \(LW_{in}\) is mainly due to a water vapor greenhouse effect. SARAWI, which represents the two processes driving temperatures, namely turbulence and longwave radiative transfer between the soil and the atmospheric surface layer, points to the crucial impact of synoptic low-level advection of water vapor on \(T_{min}\). By increasing the atmospheric infrared emissivity, the advected water vapor dramatically increases the nocturnal radiative warming of the soil surface, then in turn reducing the nocturnal cooling of the atmospheric surface layer, which remains warm throughout the night. Over Western Sahel, this advection is related to an early northward incursion of the monsoon flow. Over Sahara, the anomalously high precipitable water is due to a tropical plume event. Both observations and simulations support this major influence of the low-level water vapor radiative effect on \(T_{min}\) during this spring heatwave.

北非在2010年4月经历了严重的热浪，每日最高温度（\（T_ {max} \））经常超过\（40 \，^ {\ circ} \ mathrm {C} \）和每日最低温度（\（T_ {min} \））超过\（27 \，^ {\ circ} \ mathrm {C} \）在撒哈拉沙漠和萨赫勒地区扩大了连续五天。观测表明，受热波影响的面积和周期对应于表面入射长波通量的强正异常（\（LW_ {in} \））和入射短波通量的负正异常（\（SW_ {in} \））。后者是由撒哈拉沙漠中的云，以及萨赫勒地区的云和尘埃所解释的。但是，强烈的正异常\（LW_ {in} \）与云或气溶胶的辐射效应几乎没有关系。基于气候模型模拟（CNRM-AM）的分析，再加上特殊设计的概念性土壤-大气表层模型（SARAWI），表明\（LW_ {in} \）的正异常主要是由于水蒸气引起的温室效应。SARAWI代表驱动温度的两个过程，即土壤和大气表层之间的湍流和长波辐射传递，指出了天气低水平对流对\（T_ {min} \）的关键影响。通过增加大气的红外发射率，平流的水蒸气会极大地增加土壤表面的夜间辐射增温，进而减少大气表层的夜间降温，而夜间整个晚上都保持温暖。在萨赫勒西部地区，这种对流与季风流向北早期侵入有关。在撒哈拉沙漠上空，异常高的可降水量归因于热带羽流事件。观测和模拟都支持春季热浪期间低水平水蒸气辐射效应对\（T_ {min} \）的主要影响。