Search Results

You are looking at 1 - 10 of 657 items for :

  • Bulletin of the American Meteorological Society x
  • All content x
Clear All
Steven M. Quiring, Trent W. Ford, Jessica K. Wang, Angela Khong, Elizabeth Harris, Terra Lindgren, Daniel W. Goldberg, and Zhongxia Li

The NASMD is a high-quality observational soil moisture database that includes over 1,800 stations to support drought, land–atmosphere, and satellite/model validation studies. Soil moisture is an important state variable in the climate system, as it stimulates land–atmosphere interactions by modifying energy and wetness fluxes in the boundary layer ( Legates et al. 2011 ). Soil water content influences evapotranspiration and corresponding near-surface atmospheric moisture availability ( Pal and

Full access
Anita Drumond, Milica Stojanovic, Raquel Nieto, Sergio Martin Vicente-Serrano, and Luis Gimeno

An online catalog of drought episodes in the IPCC reference regions from 1980 to 2015, with an analysis of the moisture transport during the most severe meteorological drought episodes, is described. Understanding hydroclimatological processes is incredibly important, given the number of scientific disciplines involved and their association with several economic, social, and ecological impacts ( Allen and Ingram 2002 ). Climate change is driving global temperature changes and affecting

Open access
Kun Yang, Jun Qin, Long Zhao, Yingying Chen, Wenjun Tang, Menglei Han, Lazhu, Zhuoqi Chen, Ning Lv, Baohong Ding, Hui Wu, and Changgui Lin

SCIENTIFIC BACKGROUND AND OBJECTIVES. A multiscale soil moisture and temperature monitoring network was established on the central Tibetan Plateau to support remote sensing, land hydrological modeling, and surface process studies. As the highest plateau in the world, the Tibetan Plateau (TP) directly impacts its surrounding climate and environment through atmospheric and hydrological processes. Meanwhile, the TP climate changed significantly (such as rapid warming, moistening, solar dimming

Full access
Alan Robock, Konstantin Y. Vinnikov, Govindarajalu Srinivasan, Jared K. Entin, Steven E. Hollinger, Nina A. Speranskaya, Suxia Liu, and A. Namkhai

Soil moisture is an important variable in the climate system. Understanding and predicting variations of surface temperature, drought, and flood depend critically on knowledge of soil moisture variations, as do impacts of climate change and weather forecasting. An observational dataset of actual in situ measurements is crucial for climatological analysis, for model development and evaluation, and as ground truth for remote sensing. To that end, the Global Soil Moisture Data Bank, a Web site (http://climate.envsci.rutgers.edu/soil_moisture) dedicated to collection, dissemination, and analysis of soil moisture data from around the globe, is described. The data bank currently has soil moisture observations for over 600 stations from a large variety of global climates, including the former Soviet Union, China, Mongolia, India, and the United States. Most of the data are in situ gravimetric observations of soil moisture; all extend for at least 6 years and most for more than 15 years. Most of the stations have grass vegetation, and some are agricultural. The observations have been used to examine the temporal and spatial scales of soil moisture variations, to evaluate Atmospheric Model Intercomparison Project, Project for Intercomparison of Land-Surface Parameterization Schemes, and Global Soil Wetness Project simulations of soil moisture, for remote sensing of soil moisture, for designing new soil moisture observational networks, and to examine soil moisture trends. For the top 1-m soil layers, the temporal scale of soil moisture variation at all midlatitude sites is 1.5 to 2 months and the spatial scale is about 500 km. Land surface models, in general, do not capture the observed soil moisture variations when forced with either model-generated or observed meteorology. In contrast to predictions of summer desiccation with increasing temperatures, for the stations with the longest records summer soil moisture in the top 1 m has increased while temperatures have risen. The increasing trend in precipitation more than compensated for the enhanced evaporation.

Full access
John R. Mather

A method of computing daily values of soil moisture from climatic data is described and comparisons with measured soil moisture values are given. Because the soil moisture values are obtained from climatic data only, past values of soil moisture content, unavailable otherwise, can be determined for any place for which climatic data are available. A long record of soil moisture is computed for one locality and estimates of the probabilities of occurrence of different levels of soil moisture are made. Such estimates are essential in any realistic long range planning.

Full access
Gonzalo Miguez-Macho, Haibin Li, and Ying Fan

We demonstrate the link between two terrestrial water reservoirs: the root-zone soil moisture and the groundwater, and contribute our simulated climatologic water table depth and soil moisture fields over North America to the community. Because soil moisture strongly influences land-atmosphere fluxes, its link to the groundwater may affect the spatiotemporal variability of these fluxes. Here we simulate the climatologic water table depth at 30-arc-s resolution as constrained by U.S. Geological Survey site observations. Then, we use this water table climatology as the lower boundary for the soil, and variable infiltration capacity (VIC)-simulated land surface flux climatology as the upper boundary, to calculate the soil moisture climatology (SMC) at 14 depths (down to 4 m). Comparisons with VIC, the North America Regional Reanalysis (NARR), and observations suggest the following: first, SMC is wetter than VIC, despite their having identical land surface flux; second, while climate is the dominant signature in NARR and VIC, the water table manifests itself in SMC, with wet soil over the shallow water table; third, while soils in VIC and NARR get drier with depth, soils in SMC get wetter in regions of a shallow water table; and last, SMC has the highest root-zone (top 2 m) total soil water storage. These differences may have implications for climate modeling. We make our simulation results available to any interested researcher, for applications such as model initialization and intercomparison.

Full access
Andrew F. Bunker

The humidity indicated by the rapidly rising radiosonde lags behind the true humidity of the air, making moisture gradient determinations uncertain by a factor of 4. Application of isothermal laboratory determinations of the lag to the readings may be misleading because the radiosonde, in rising through the atmosphere, usually passes from warm air to cooler air. The lag of the strip may be quite different under these circumstances. By comparison of radiosonde reports with airplane humidity soundings, it is found that in the case of the radiosonde moving from warm, dry air (about − 5°C) to cooler, moister air (about − 18°C) the lag may increase to 165 seconds. When it passes to cooler, drier air, the lag decreases to 10 to 20 seconds. Using these lags and assuming an exponential approach to the final value, more nearly correct values of the humidity at particular heights can be computed from the radiosonde records.

Full access
Herbert Riehl

Average values of moisture and stability for the lower troposphere are computed at three-hourly intervals. Comparison of the diurnal moisture and stability variation with the diurnal rainfall variation does not yield a satisfactory explanation of the latter. Cloud observations, however, suggest an explanation of the precipitation curve, based on the effect of topography on the field of vertical motion.

Full access
William P. Lowry

This paper presents an abbreviated review of the literature concerning the relationship of evaporative moisture-loss rate to soil-moisture content. Results from a variety of sources appear to fall into four major types of curve expressing this relationship. The author compares these types and concludes that three of them are mutually supporting and represent special cases of the same process. The fourth type is considered contradictory. It is concluded further that the search for a neat, concise, general statement of the relationship under consideration is probably futile.

Full access
S. H. Melfi and D. Whiteman

Observations of the water-vapor mixing ratio in the lower atmosphere and its temporal evolution have been made with a Raman lidar. Comparison with an independent radiosonde measurement indicated excellent agreement. The moisture structure, observed up to an altitude of 5 km and over an 80-min period during the early morning of 30 April 1985 (the present lidar is limited to night operation), showed temporal variations of several atmospheric features which could not be resolved by balloon soundings. Application of the lidar should provide the opportunity to study details of atmospheric moisture, its structure, and its evolution in a manner never before realized.

Full access