Introduction

1. Interaction between the surface and the atmospheric boundary layer (ABL)
   
   • FIFE results leaded Surface condition - Surface flux - boundary layer circulation relationship. (Wai and Smith 1998)
   • Flatland's simultaneous observation of the wind profiler radar (WPR) and surface flux focused on entrainment zone. (Angevine et al. 1998)
2. Asian monsoon region
   • Many individual surface or ABL observation have been recorded under GAME and GAME-related projects. (Hiyama et al., 1999; Ohta et al., 1999; Sugita et al., 1999; Asanuma et al., 2000; Ohta et al., 2001; Tanaka et al., 2001; Reddy et al., 2001; Bian et al., 2002; Toda et al., 2002; Hiyama et al., 2003; Gao et al., 2003; Komatsu et al., 2003; Choi et al., 2004; Strunin et al., 2004; Strunin and Hiyama, 2004; Shinoda et al., 2005)
   • Simultanenous observation of WPR and surface flux meaurements have not yet been reported for the Asian monsoon region.
3. LAPS project to clarify precipitation onset mechanisms
   • ABL processes are one of many triggers that generate clouds and precipitation.
   • Changes in surface condition alter surface heat and water vapor fluxes that in turn affect ABL structures.

Basic equations

1. Wind profiler rader echo and ABL depth

• ABL depth is an important parameter in studies of the ABL.
• WPR detects the ABL top as the level with maximum WPR echo, because the entrainment layer has large scalar gradients and therefore many turbulent structures. (Angevine et al. 1994, 2001; White et al. 2002)
• The WPR echo P_R is given by the radar equation as
  where P_r transmitted peak power, G antenna gain, λ radar wavelength, r range to the backscatter volume, θ beam width, h pulse length, and η radar reflectivity per unit volume.
• The radar reflectivity η is proportional to the refractive index structure parameter C_n² as follows;
  The structure parameter C_n² represents the intensity of turbulence, and strongly depends on gradients of vapor density.

2. Surface flux and ABL depth

• Based on conservation of temperature within ABL, ABL depth can be estimated from Surface heat flux, the vertical motion at ABL top, and horizontal advection. If the vertical motion and horizontal advection are negligible, ABL depth is related to surface heat flux as follow (cf., Garratt 1992 based on Tennekes 1973):
  Here z0 initial depth, Δz increment of depth, Γ lapse rate, ε entrainment parameter, and Q_S surface virtual temperature flux.

Target of this observation

• Surface-ABL relationship in Asian monsoon region (Meiyu region).

Goals of this study

• To understand how the drastic change in surface moisture condition during the Meiyu season affects the ABL structre.
• To describe the vapor source that provides or maintains high humidity throughout the Meiyu season.

Contents of this paper

• Description of the surface and ABL observations in the LAPS project
• Presentation of the initial data from tower obseravtions, WPR observations, and vegetation reearch
• Presentation of the relationships between ABL depth versus the surface heat fluxes and other parameters, such as vertical motion at ABL top.

Site

Site is located at Shouxian Meteorol. Obs. near the Huaihe River in Anhui Province, China. Latitude 32.55 N Longitude 116.78 E Altitude 22.7 m A.S.L. Monitoring started in Aug 2003. IOP-2004: 24 May to 16 Jul 2004. (IOP-2005: 17 May to 16 Jul 2005)

Variables observed manually duraing IOP-2004

Variables	Intervals	Notes
Water temperature	1 hour during daytime, 08:00-17:00 LT	No water before 14 JUN
Soil temperature	1 hour during daytime, 08:00-17:00 LT	At 0.1 m below-ground
Surface temperature	1 hour during daytime, 08:00-17:00 LT	Soil surface before 14 JUN; Water surface after 15 JUN
Vegetation height	Once per day	No vegetation between 31 MAY and 15 JUN
Water depth	Once per day	No water before 14 JUN
SPAD*	Once per day	No vegetation between 31 MAY and 15 JUN
Leaf area index (LAI)	5 times, 25 MAY, 16 JUN, 24 JUN, 30 JUN, 7 JUL	No vegetation between 31 MAY and 15 JUN
Cloud amount	Twice per day	Using fish-eye sky photos and weather condition records

*: An index of the chlorophyll density obtained by a chlorophyll sensor (SPAD-502, Konica Minolta, Japan)

Observed items on the surface layer observation system

Operation specifications for WPR

1. Data accessing has been presented at this seminar on 20041125
2. Estimation of the ABL depth from WPR data has been presented in GSMaP-LAPS Joint Workshop on 200050324

Overview of the climate and surface conditions

Diurnal development of the ABL depth

Seasonal changes in the ABL depth

Concluding remarks

1. A preliminary analysis of surface and ABL observations revealed relationships between surface fluxes and the ABL structure.
2. Buoyancy flux enhanced ABL development.
3. Fluctuations in ABL depth were related to plume-like wind structures within the ABL.
4. Daily variations in ABL depth were controlled mainly by the buoyancy flux over the surface during dry periods.
5. Variations were strongly affected by atmospheric vertical motion during wet periods such as the Meiyu season.
6. Further analysis to investigate how ABL depth is affected by the combined effects of temperature and humidity profiles in addition to surface fluxes is warranted.
7. The source of the increased atmospheric humidity during the onset of Meiyu, and the mechanism that maintains humidity during the Meiyu season, may be surface vapor flux caused by irrigation. Humid conditions affect ABL structure and development.
8. In addition, synoptic-scale vapor transport may increase atmospheric humidity during the onset of Meiyu. Relationships between local phenomena and synoptic-scale humidity must be studied with further observations, satellite remote sensing, and reanalysis data such as NCEP/NCAR.
9. Projections of water vapor transport at synoptic scales, i.e., weather forecasts, influence agricultural schedules. Interactions between anthropogenic hydrological activities and atmospheric phenomena also warrant future study.

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Eco-hydromet. Seminar 20050722

Acknowledgments

This part of the Lower Atmosphere and Precipitation Study (LAPS) was conducted under the Core Research for Evolutional Science and Technology (CREST) program of the Japan Science and Technology Agency (JST) and the Hydrospheric Atmospheric Research Center (HyARC) at Nagoya University. The authors thank LAPS members for their cooperation and helpful discussions, CREST research manager Dr. Shigeo Masuda for kind collaboration, and Ms. Tomoko Tanaka for hard work with logistics. The authors thank Sumitomo Electronic Industries, Ltd., and Climatec, Inc. for cooperation with the establishment of the observation systems. We also thank Shouxian Meteorological Observatory, Anhui Meteorological Bureau, and the China Meteorological Administration for their collaboration in this study.



Thank you for your attention.





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