Vertical Structure of a Nonprecipitating Cold Frontal Head as Revealed by Raman Lidar and Wind Profiler Observations

Abstract

The vertical distributions of water vapor, aerosols and cloud backscattering, and three-dimensional wind were measured using a Raman lidar and a wind profiler during the passage of a non-precipitating cold front during the night of 19-20 March 2002 over Tsukuba, Japan. The passage of the cold frontal head was identified by a sharp drop in the temperature at a height of 213 m, when the backscattering ratios sharply decreased below an altitude of approximately 2.7 km. The water vapor mixing ratios showed high values (@2.5 g kg À1 ) around the frontal head. Arc clouds were observed in the watersaturated air above the frontal head in updraft regions (@1 m s À1 ). The cold air mass showed the geometrical and dynamical characteristics of gravity (density) currents: nose and head identified by the lowbackscattering ratio region at the leading edge, billow-like patterns in the backscattering ratio behind the head, and feeder flows within the head (in a positive direction toward the frontal head). The observed height, and the propagation speed of the cold air mass, approximately agreed with those calculated from surface meteorological data using gravity current models, although there were uncertainties in the calculated values because of the lack of the vertical distributions of temperature and pressure data.

Dust Event in the Gobi Desert on 22-23 May 2013: Transport of Dust from the Atmospheric Boundary Layer to the Free Troposphere by a Cold Front

“…4b). Sakai et al (2005), which shows that the particle backscattering ratio of cold air mass was smaller than that of warm air mass. The leading edge of the cold air mass is not clear because of the large attenuated backscatter coefficient around the cold front due to the dust layer ranging from the warm air mass to the cold air mass.…”

Dust Hotspot in the Gobi Desert: A Field Survey in April 2019

“…Based on the photograph, the height of the dust storm head was estimated to be 600 m, which was calculated using the distance between the camera and the dust storm, calculated from GPS data, and the focal length of the camera lens. The head structure suggests that the dust storm was induced by a gravity current (Simpson, 1987;Stull, 2006;Sakai et al, 2005).…”

“…On a local scale, severe dust storms result in the loss of human lives and significantly interrupt social and economic activities (Shao et al, 2003). Dust storms are a manifestation of gravity currents, which have been extensively investigated in the laboratory and field (Simpson, 1987;Sakai et al, 2005). Relatively small dust hotspots, where dust events occur frequently due to the local topography and surface conditions, have been identified in the Sahara and Gobi Deserts (Gillette, 1999;Knippertz and Todd, 3 2010;Zhang et al, 2016).…”

The Life Cycle of an Undular Bore and Its Interaction with a Shallow, Intense Cold Front

“…Schultz (2005) reviewed a collection of mechanisms believed responsible for the formation of prefrontal features, including the generation of a prefrontal bore and subsequent gravity waves. A number of prior studies have investigated cases in which a trough or wind shift formed in advance of a cold front in association with a bore (e.g., Haase and Smith 1984;Karyampudi et al 1995;Koch and Clark 1999;Locatelli et al 2002;Sakai et al 2005). In the present study, we will examine the interaction between a prefrontal bore and its associated surface cold front in order to illustrate the relationship between the bore life cycle and the evolution of the prefrontal features.…”