3-D water vapor field in the atmospheric boundary layer observed with scanning differential absorption lidar

Abstract

Abstract. High-resolution three-dimensional (3-D) water vapor data of the atmospheric boundary layer (ABL) are required to improve our understanding of land-atmosphere exchange processes. For this purpose, the scanning differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) was developed as well as new analysis tools and visualization methods. The instrument determines 3-D fields of the atmospheric water vapor number density with a temporal resolution of a few seconds and a spatial resolution of up to a few tens of meters. We present three case studies from two field campaigns. In spring 2013, the UHOH DIAL was operated within the scope of the HD(CP) 2 Observational Prototype Experiment (HOPE) in western Germany. HD(CP) 2 stands for High Definition of Clouds and Precipitation for advancing Climate Prediction and is a German research initiative. Range-height indicator (RHI) scans of the UHOH DIAL show the water vapor heterogeneity within a range of a few kilometers up to an altitude of 2 km and its impact on the formation of clouds at the top of the ABL. The uncertainty of the measured data was assessed for the first time by extending a technique to scanning data, which was formerly applied to vertical time series. Typically, the accuracy of the DIAL measurements is between 0.5 and 0.8 g m −3 (or < 6 %) within the ABL even during daytime. This allows for performing a RHI scan from the surface to an elevation angle of 90 • within 10 min. In summer 2014, the UHOH DIAL participated in the Surface Atmosphere Boundary Layer Exchange (SABLE) campaign in southwestern Germany. Conical volume scans were made which reveal multiple water vapor layers in three dimensions. Differences in their heights in different directions can be attributed to different surface elevation. With low-elevation scans in the surface layer, the humidity profiles and gradients can be related to different land cover such as maize, grassland, and forest as well as different surface layer stabilities.

Characterisation of boundary layer turbulent processes by the Raman lidar BASIL in the frame of HD(CP)&lt;sup&gt;2&lt;/sup&gt; Observational Prototype Experiment

“…Within the considered time interval, z i is found to be characterised by a limited variability, with a mean value z i of 1290 m a.g.l, and a standard deviation of 75 m. The minimum and maximum values of z i during the observation period are 1140 and 1440 m a.g.l., respectively. This result is in very good agreement with the simultaneous measurements performed by the University of Hohenheim Differential Absorption Lidar (UHOH-DIAL; Wagner et al, 2013;Späth et al, 2016), deployed in Hambach, approx. 4 km E-SE, with a mean value of 1295 m and a standard deviation of 86 m .…”

Sensitivity study of the planetary boundary layer and microphysical schemes to the initialization of convection over the Arabian Peninsula

“…Currently it is difficult to evaluate the quality of the vertical structures of temperature, moisture, and wind due to the unavailability of high spatial and temporal resolution atmospheric profiler data like differential absorption lidar and Raman lidar instrumentation (Hammann et al 2015;Späth et al 2016).…”

The HD(CP)&lt;sup&gt;2&lt;/sup&gt; Observational Prototype Experiment (HOPE) – an overview

“…A temperature rotational Raman lidar (TRRL) measured temperature profiles Hammann et al, 2015;Radlach et al, 2008) and a water vapour DIAL measured absolute humidity profiles Späth et al, 2016;Wagner et al, 2013). In contrast to the Raman lidar technique, the DIAL technique, which is based on the alternating emission of laser pulses at frequencies strongly and weakly absorbed by water vapour, does not require calibration.…”

“…Barrera-Verdejo et al (2016) similarly showed the positive impact of combining rotational Raman lidar measurements of BASIL with microwave radiometer observations for improving the temperature profile above the boundary layer. Based on scanning measurements with the water vapour DIAL of IPM made during HOPE-Jülich, Späth et al (2016) (see Sect. 2.1.1) presented a detailed study of the 3-D structure of the water vapour field between the supersites HAM, KRA, and JUE with a range resolution of 30-300 m and a temporal resolution in the range of 10 s for each profile.…”