Sensitivity of climate simulations to land-surface and atmospheric boundary-layer treatments - a review

Journal Article · Mon Mar 01 04:00:00 EST 1993 · Journal of Climate; (United States)

DOI:https://doi.org/10.1175/1520-0442(1993)006<0419:SOCSTL>2.0.CO;2· OSTI ID:6534557

Garratt, J R ^[1]

---

1. CSIRO Division of Atmospheric Research, Victoria (Australia)

Aspects of the land-surface and boundary-layer treatments in 20 or so atmospheric general circulation models (GCMs) are summarized. only a few of these have had significant sensitivity studies published. The sensitivity studies focus upon the parameterization of land- surface processes and specification of land-surface properties including albedo, roughness length, soil moisture status, and vegetation density. The impacts of surface albedo and soil moisture upon the climate simulated in GCMs with bare-soil land surfaces are well known. Continental evaporation and precipitation tend to decrease with increased albedo and decreased soil moisture availability. Few conclusive studies have been carried out on the impact of a gross roughness-length change. A canopy scheme in a GCM ensures the combined impacts of roughness, albedo, and soil-moisture availability upon the simulated climate. The most revealing studies to date involve the regional impact of Amazonian deforestation. Four studies show that replacing tropical forest with a degraded pasture results in decreased evaporation and precipitation, and increased near-surface air temperatures. Sensitivity studies suggest the need for a realistic surface representation in general circulation models of the atmosphere. It is not yet clear how detailed this representation needs to be, but the parameterization of boundary-layer and convective clouds probably represents a greater challenge to improved climate simulations. This is illustrated in the case of surface net radiation for Amazonia, which is not well simulated and tends to be overestimated, leading to evaporation rates that are too large. Underestimates in cloudiness, cloud albedo, and clear-sky shortwave absorption, rather than in surface albedo, appear to be the main culprits. Three major tasks for the researcher of development and validation of atmospheric boundary-layer and surface schemes are detailed.

• OSTI ID: 6534557
• Journal Information: Journal of Climate; (United States), Journal Name: Journal of Climate; (United States) Vol. 6:3; ISSN JLCLEL; ISSN 0894-8755
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
ALBEDO
ATMOSPHERIC PRECIPITATIONS
BOUNDARY LAYERS
BRAZIL
CANOPIES
CLIMATES
CLOUDS
DEVELOPING COUNTRIES
EARTH ATMOSPHERE
EARTH PLANET
EVAPORATION
GENERAL CIRCULATION MODELS
LATIN AMERICA
LAYERS
MATHEMATICAL MODELS
PHASE TRANSFORMATIONS
PLANETS
PLANTS
SENSITIVITY
SOILS
SOUTH AMERICA
SURFACE PROPERTIES