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William Blumen
and
Warren M. Washington

The scope of activities and accomplishments in areas of atmospheric dynamics and numerical weather prediction under investigation in the People's Republic of China during the period 1949–1966 is surveyed. The principal topics considered include cumulus and turbulent boundary layer dynamics and the dynamics of meso-, synoptic-, and planetary-scale motions. Attention is focused on the complementary research paths followed in theoretical and numerical dynamics, particularly in relation to the development of operational forecasting models. These latter accomplishments are traced from the late 1950s until mid-1966, at which time overseas distribution of Chinese scientific journals was discontinued. Significant investigations of both regional and global circulation regimes have also been noted. However, a more exhaustive overview of the contributions made by Chinese meteorologists to the theory of the general circulation appears warranted.

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Gregory S. Poulos
,
William Blumen
,
David C. Fritts
,
Julie K. Lundquist
,
Jielun Sun
,
Sean P. Burns
,
Carmen Nappo
,
Robert Banta
,
Rob Newsom
,
Joan Cuxart
,
Enric Terradellas
,
Ben Balsley
, and
Michael Jensen

The Cooperative Atmosphere–Surface Exchange Study—1999 (CASES-99) refers to a field experiment carried out in southeast Kansas during October 1999 and the subsequent program of investigation. Comprehensive data, primarily taken during the nighttime but typically including the evening and morning transition, supports data analyses, theoretical studies, and state-of-the-art numerical modeling in a concerted effort by participants to investigate four areas of scientific interest. The choice of these scientific topics is motivated by both the need to delineate physical processes that characterize the stable boundary layer, which are as yet not clearly understood, and the specific scientific goals of the investigators. Each of the scientific goals should be largely achievable with the measurements taken, as is shown with preliminary analysis within the scope of three of the four scientific goals. Underlying this effort is the fundamental motivation to eliminate deficiencies in surface layer and turbulent diffusion parameterizations in atmospheric models, particularly where the Richardson number exceeds 0.25. This extensive nocturnal boundary layer (NBL) dataset is available to the scientific community at large, and the CASES-99 participants encourage all interested parties to utilize it.

These preliminary analyses show that during nights where weak (< 2 m s−1) surface winds and strong static stability near the surface (exceeding 150 C km−1 to 20 m AGL) might otherwise indicate essentially nonturbulent conditions, that various, sometimes undefined, atmospheric phenomena can generate significant turbulent mixing, and therefore significant turbulent fluxes. In many cases, a jet structure will form in the NBL between 50 and 200 m AGL, resulting in strong shear between the surface and jet maximum. Consequently, though surface winds are weak, turbulence can be a significant feature in the stable NBL. Further, contrary to some previous work studying nocturnal jets over the Great Plains, the wind direction in the jet is often influenced by an inertial oscillation and seldom confined to the southerly quadrant (e.g., the Great Plains low-level jet).

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Margaret A. LeMone
,
Robert L. Grossman
,
Richard L. Coulter
,
Marvin L. Wesley
,
Gerard E. Klazura
,
Gregory S. PouIos
,
William Blumen
,
Julie K. Lundquist
,
Richard H. Cuenca
,
Shaun F. Kelly
,
Edward A. Brandes
,
Steven P. Oncley
,
Robert T. McMillen
, and
Bruce B. Hicks

This paper describes the development of the Cooperative Atmosphere Surface Exchange Study (CASES), its synergism with the development of the Atmosphere Boundary Layer Experiments (ABLE) and related efforts, CASES field programs, some early results, and future plans and opportunities. CASES is a grassroots multidisciplinary effort to study the interaction of the lower atmosphere with the land surface, the subsurface, and vegetation over timescales ranging from nearly instantaneous to years. CASES scientists developed a consensus that observations should be taken in a watershed between 50 and 100 km across; practical considerations led to an approach combining long-term data collection with episodic intensive field campaigns addressing specific objectives that should always include improvement of the design of the long-term instrumentation. In 1997, long-term measurements were initiated in the Walnut River Watershed east of Wichita, Kansas. Argonne National Laboratory started setting up the ABLE array. The first of the long-term hydrological enhancements was installed starting in May by the Hydrologic Science Team of Oregon State University. CASES-97, the first episodic field effort, was held during April–June to study the role of surface processes in the diurnal variation of the boundary layer, to test radar precipitation algorithms, and to define relevant scaling for precipitation and soil properties. The second episodic experiment, CASES-99, was conducted during October 1999, and focused on the stable boundary layer. Enhancements to both the atmospheric and hydrological arrays continue. The data from and information regarding both the long-term and episodic experiments are available on the World Wide Web. Scientists are invited to use the data and to consider the Walnut River Watershed for future field programs.

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