Improvement of cloud modelling for global and regional climate and weather studies requires comprehensive information on many cloud parameters. This information is delivered by remote observations of clouds from ground-based and space-borne platforms using different methods and processing algorithms. Cloud liquid water path (LWP) is one of the main obtained quantities. Previously, measurements of LWP by the SEVIRI (Spinning Enhanced Visible and InfraRed Imager) and AVHRR (Advanced Very High Resolution Radiometer) satellite instruments provided evidence for the systematic differences between LWP values over land and water areas in northern Europe. An attempt is made to detect such differences by means of ground-based microwave observations performed near the coastline of the Gulf of Finland in the vicinity of St Petersburg, Russia. The microwave radiometer (RPG-HATPRO, Radiometer Physics GmbH – Humidity And Temperature PROfiler), located 2.5 km from the coastline, is functioning in the angular scanning mode and is probing the air portions over land (at an elevation angle of 90^∘) and over water (at seven elevation angles in the range 4.8–30^∘). The influence of the land–sea LWP difference on the brightness temperature values in the 31.4 GHz spectral channel has been demonstrated, and the following features have been detected: (1) an interfering systematic signal is present in the 31.4 GHz channel, which can be attributed to the humidity horizontal gradient, (2) clouds over the opposite shore of the Gulf of Finland mask the LWP gradient effect. Preliminary results of the retrieval of LWP over water by the statistical regression method applied to the microwave measurements by HATPRO in the 31.4 and 22.24 GHz channels are presented. The monthly averaged results are compared to the corresponding values derived from the satellite observations by the SEVIRI instrument and from the reanalysis data.

中文翻译：

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基于地面微波观测的海岸线地区云状液态水路径水平不均匀性检测：可行性研究

改进用于全球和区域气候和天气研究的云模型需要有关许多云参数的全面信息。该信息是通过使用不同方法和处理算法从地面和星载平台对云进行远程观察来提供的。云水路径（LWP）是获得的主要量之一。以前，通过SEVIRI（旋转增强型可见光和红外成像仪）和AVHRR（先进的超高分辨率辐射计）卫星仪器对LWP的测量为北欧陆地和水域的LWP值之间的系统差异提供了证据。试图通过在俄罗斯圣彼得堡附近的芬兰湾海岸线附近进行的地面微波观测来检测这种差异。^∘）并在水（在范围为4.8-30 7的仰角^∘）。已经证明了陆海LWP差异对31.4 GHz频谱信道中的亮度温度值的影响，并且检测到以下特征：（1）31.4 GHz信道中存在干扰的系统信号，可以是归因于湿度水平梯度，（2）芬兰湾对岸的云层掩盖了LWP梯度效应。给出了通过统计回归方法在31.4和22.24 GHz信道上由HATPRO进行微波测量的水上LWP取回的初步结果。将月平均结果与SEVIRI仪器从卫星观测数据和重新分析数据得出的相应值进行比较。