Preliminary results of ABL observations in LAPS project in Huaihe river basin*Hiroki Tanaka1,2, Tetsuya Hiyama1, Atsushi Higuchi1, Taro Shinoda1, Hatsuki Fujinami1,2, Kenji Nakamura1(1: HyARC, Nagoya University, 2: CREST, JST)*HyARC, Nagoya University, Japan, 464-8601, Furo-cho,Chikusa Nagoya, Japan. e-mail: hiroki@hyarc.nagoya-u.ac.jp
Abstract
In order to clarify the relationships between the terrestrial surface and the atmospheric boundary layer (ABL), a continuous
observation system for the surface and the ABL meteorology was installed on August 2003, in the mid-latitude flat regionsin Huaihe river basin. A 30-meter tower was installed to obtain the hydro-meteorological parameters within the surface
sub-layer, on the surface, and under the ground. Mixed layer meteorology was observed by a wind profiler radar (WPR),Doppler sodars, and a micro-wave water vapor profiler. Intensive observation was carried out including the research of thesurrounding vegetation during before and after Meiyu season 2004. The surrounding surface condition clearly reflected onthe ABL meteorology through the surface heat fluxes. The WPR echo intensity within the ABL showed periodical peaks
during daytime of clear days, implying the plume-like turbulences.
Keyword: atmospheric boundary layer, surface heat flux, wind profiler radar, observation

1. Introduction
LAPS, the Lower Atmosphere and Precipitation Study,
one of the projects of the Core Research for Evolutional
Science and Technology (CREST) of the Japan Scienceand Technology Agency (JST), aims to clarify theprocesses and mechanisms of precipitation onset, theSurface-ABL-Cloud-Precipitation relationship. The main
target of the observation in this study was the Surface-ABL
relationship before and after the Meiyu, the rainy season inChina. The intensive observation including vegetation
researches for surroundings was carried out from 24th May
through 16th July in 2004. This paper introduces theLAPS observation in China, and reports the preliminary
results of the surface-ABL observations including thetower observation, the wind profiler radar (WPR)
observation, and the manual observations during theintensive observation period.

2. Site and Materials
2.1.
Study site
The study site was set at the mid-latitude flat surface
regions in China. The main site is located at Shouxian,
116.78E and 32.55N, 22.7m A.S.L., the middle reaches ofHuaihe river, Anhui province of China (cf. Fig.1). The
other sites were set at Xiaoxian and Feixi for the Doppler
sodar observations.

2.2.

Fig. 1: Location of the observation site.
Ultra-sonicanemo-thermomet

Hygrothermometer

Open-path gas
analyzer

Windscope

3-cup anemometer
Infraredthermometer
Rain gage30m
4-component
radiometer
Barometer
Heat-flow plate
Thermometer

Water level gage

10mContinuous observations

The observation started in summer 2003 at Shouxian,
Xiaoxian, and Feixi with a 30-meter tower (cf., Fig. 2), aWPR (L-28, Sumitomo Electric Industries, LTD., Japan),three Doppler sodars (XFAS, Scintec, AG., Germany), anda micro-wave water vapor profiler (TP/WVP-3000,Radiometrics, Co., USA.)The tower, the flux and meteorological observation
system was installed to obtain the hydro-meteorologicalparameters such as the turbulent fluxes, the radiation fluxes,
the wind velocity, the temperature, the humidity, and so on.
The positions of the installed devices on the tower wereshown in Fig. 2. The static parameters excepting theturbulent variables were stored every 5 minutes. The
turbulent fluxes were computed every 30 minutes using the20m

TDR soilhygrometer

0m
-0.2m
-0.4m

Fig. 2: Illustration for the tower observation.
turbulent variables collected by 10Hz.
The 3-D wind vector profiles within the ABL wereobtained by the WPR observation every minute. TheWPR observation also provided the echo intensity from theatmosphere, which indicates the turbulent intensity at each
altitude.

2.3.

Manual observations

The manual observations were carried out at 6 points
around the Shouxian site. The temperatures of the paddy
water, the soil, and the surface were observed everyday
with approximately 1 hour intervals during daytime. The
canopy height, the water depth, and the SPAD values
reflecting the chlorophyll concentration were taken once aday. The leaf area indexes (LAI) for unit area wasobserved once a week.

Fig. 3: The change in the canopy height, the leaf areaindex (LAI), and the albedo during the intensive
observation period in 2004.

3. Results and Discussions
3.1.
Surface conditions
The dominant vegetation was wheat until 30th May when
it was harvested. The wheat litter was burned artificiallyon the ground from 1st through 4th June. Rice seedlings
were planted with filling water on 14th June, after the ashof the wheat litter was plowed under the ground. Thenthe rice seedlings grew up during the later half of theobservation period. The change in the canopy height andthe LAI were shown in Fig. 3 with the observed albedo.
The change of the albedo was well corresponding to thesurface events mentioned above. The canopy height wasgood indicator of LAI in this season.

3.2.

Fig. 4: Diurnal changes of the solar radiation (black line),
the sensible heat flux (red marked lines), and the latent
heat flux (blue marked lines) on clear days in 2004.

Surface fluxes and ABL structures

The diurnal changes of the energy fluxes over thesurface on 5 clear days were shown in Fig. 4. Both of thesensible H and latent flux λE were changed similarly,
corresponding to the change in the solar radiation on 22nd
May, before the wheat was cut off. The λE was decreased
between the cutting and water filling, 31st May and 3rd June.
After filling water and planting rice seedlings, 22nd Juneand 3rd July, the H dropped and the λE increased.
Figure 5 shows the echo intensity obtained by the WPR
observation on the same days as Fig. 4, implying theturbulent intensity. The periodical peaks were detected
when H was not small, at the daytime of 22nd, 31st May and3rd June. These peaks might indicate the plume-liketurbulences due to the large surface heating indicated bythe H. The relatively large echo during the daytime on
22nd June might reflect the high humidity due to the large
λE. The ABL depth was developed until 1.5-2.0 km, evenwhen the H was not significant on the humid days, 22ndJune and 3rd July.

Fig. 5: Diurnal time-height sections of the echo intensity
received by the Windprofiler on the same days as Fig. 4.