Surface flux and atmospheric boundary layer observations from the LAPS project over the middle stream of the Huaihe River basin in China

Abstract

Abstract:Observations of the surface layer and the atmospheric boundary layer (ABL) were collected as part of the Lower Atmosphere and Precipitation Study (LAPS), which investigated the relationship between the surface conditions and the ABL processes. The LAPS was part of the Core Research for Evolutional Science and Technology (CREST) program, under the auspices of the Japan Science and Technology Agency (JST). Observations began in August 2003 over a flat surface region in midlatitude China at 32Ð55°N, 116Ð78°E. Observations before, during, and after the Meiyu season in China provided data for surface conditions varying from relatively dry to moist. Preliminary analysis of the surface and the ABL observations shows relationships between the surface fluxes and the ABL structure. ABL depth was enhanced by sensible heat flux. Fluctuations in the ABL depth corresponded to plume-like wind structures within the ABL. Day-to-day variability in ABL depth was controlled mainly by buoyancy flux over the surface during dry periods. It was also affected by vertical motion at the top of the ABL, especially during wet periods.

Characteristics of Vertical Circulation in the Convective Boundary Layer over the Huaihe River Basin in China in the Early Summer of 2004

“…Therefore, the top of the CBL is detected as a large SNR because of the turbulence and the large gradient of water vapor between the humid boundary layer and dry free atmosphere (Angevine et al 1994). In this study, we used the concept outlined above but also added a limit to the possible height range (Tanaka et al 2007). The CBL top height was estimated within a variable range to avoid large SNRs near the surface or above the actual CBL top.…”

“…During this season, a surface transition is caused by the change in the crop in the double-cropping system. For a detailed description of the observations, see Tanaka et al (2007). Table 1 shows the operating specifications of the WPR.…”

“…The sensible heat flux was the primary controlling factor, as reported by previous studies of relatively dry terrestrial areas (e.g., Kaimal et al 1976;Stull 1988;Yi et al 2001). However, although Tanaka et al (2007) investigated the characteristics of the bulk structure of the CBL, the vertical circulation in the CBL has not been studied.…”

“…Tanaka et al (2007) described the seasonal change of parameters with regard to the land surface (e.g., albedo, soil moisture), physical values near the surface [e.g., sensible heat flux, latent heat flux (LHF)], and the height of the CBL top. The height of the CBL top was found to correlate with the sensible heat provided from the land surface, which was related to vegetation change; the CBL top was low when paddy fields covered the land surface.…”

Convective Boundary Layer above a Subtropical Island Observed by C-band Radar and Interpretation using a Cloud Resolving Model

“…Recent remote sensing techniques such as windprofiler radars (WPRs) and lidars much improve the ability to capture turbulent air motion in the upper layer of the CBL. One way to obtain a vertical CBL profile is by using a combination of a flux tower and WPR, and this method was used in past studies (e.g., Tanaka et al 2007). To date, creation of the CBL over flat terrain has been the subject of both theoretical and observational studies.…”