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A. Stickler, A. N. Grant, T. Ewen, T. F. Ross, R. S. Vose, J. Comeaux, P. Bessemoulin, K. Jylhä, W. K. Adam, P. Jeannet, A. Nagurny, A. M. Sterin, R. Allan, G. P. Compo, T. Griesser, and S. Brönnimann

To better understand variability in weather and climate, it is vital to address past atmospheric circulation. This need requires meteorological information not just from the surface but also at upper levels. Current global upper-level datasets only reach back to the 1940s or 1950s and do not cover some important periods in the first half of the twentieth century. Extending the observational record is therefore considered important in order to analyze climate variability in the past and verify global climate models used to predict future climate change. Although earlier upper-air data from platforms such as radiosondes, aircraft, pilot balloons, registering balloons, and kites are available from various sources, no systematic compilation and quality assessment of upper-level data prior to the International Geophysical Year (1957/58) has ever been performed. Here we present the Comprehensive Historical Upper-Air Network (CHUAN). It is a consistent global historical upper-air dataset that has been derived from heterogeneous data available from various sources as well as from newly digitized data. This paper describes the CHUAN dataset, the metadata, the quality control procedures, and the relationship to existing datasets. Some examples are given of its usefulness for analyzing weather and climate during the first half of the twentieth century. The CHUAN dataset comprises 3987 station records worldwide or about 16.4 million profiles (of which 12.6 million are before 1958 and 5.3 million, primarily from pilot balloons, are before 1948). A monthly mean version can be downloaded from the World Wide Web (www.historicalupperair.org).

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W. P. Kustas, D.C. Goodrich, M.S. Moran, S. A. Amer, L. B. Bach, J. H. Blanford, A. Chehbouni, H. Claassen, W. E. Clements, P. C. Doraiswamy, P. Dubois, T. R. Clarke, C. S. T. Daughtry, D. I. Gellman, T. A. Grant, L. E. Hipps, A. R. Huete, K. S. Humes, T. J. Jackson, T. O. Keefer, W. D. Nichols, R. Parry, E. M. Perry, R. T. Pinker, P. J. Pinter Jr., J. Qi, A. C. Riggs, T. J. Schmugge, A. M. Shutko, D. I. Stannard, E. Swiatek, J. D. van Leeuwen, J. van Zyl, A. Vidal, J. Washburne, and M. A. Weltz

Arid and semiarid rangelands comprise a significant portion of the earth's land surface. Yet little is known about the effects of temporal and spatial changes in surface soil moisture on the hydrologic cycle, energy balance, and the feedbacks to the atmosphere via thermal forcing over such environments. Understanding this interrelationship is crucial for evaluating the role of the hydrologic cycle in surface–atmosphere interactions.

This study focuses on the utility of remote sensing to provide measurements of surface soil moisture, surface albedo, vegetation biomass, and temperature at different spatial and temporal scales. Remote-sensing measurements may provide the only practical means of estimating some of the more important factors controlling land surface processes over large areas. Consequently, the use of remotely sensed information in biophysical and geophysical models greatly enhances their ability to compute fluxes at catchment and regional scales on a routine basis. However, model calculations for different climates and ecosystems need verification. This requires that the remotely sensed data and model computations be evaluated with ground-truth data collected at the same areal scales.

The present study (MONSOON 90) attempts to address this issue for semiarid rangelands. The experimental plan included remotely sensed data in the visible, near-infrared, thermal, and microwave wavelengths from ground and aircraft platforms and, when available, from satellites. Collected concurrently were ground measurements of soil moisture and temperature, energy and water fluxes, and profile data in the atmospheric boundary layer in a hydrologically instrumented semiarid rangeland watershed. Field experiments were conducted in 1990 during the dry and wet or “monsoon season” for the southwestern United States. A detailed description of the field campaigns, including measurements and some preliminary results are given.

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